Abstract:
An improved diaphragm ( 34, 56 ) for drop on demand ink jet print heads and method for manufacturing the same. The present diaphragm ( 34, 56 ) includes a support element ( 42, 62 ) defining at least a portion of a chamber ( 14 ) for holding ink, the support element ( 42, 62 ) defining an opening ( 40 ) adjacent to the chamber ( 14 ), and the diaphragm ( 34, 56 ) being electroformed on a surface ( 26 ) of the support element ( 42, 62 ) around the opening ( 40 ) at least substantially covering the opening ( 40 ) and enclosing the chamber ( 14 ). The diaphragm ( 34, 56 ) preferably has a central region ( 48 ) disposed generally centrally over the opening ( 40 ) and a bellows ( 58 ) surrounds the central region ( 48 ). The central region ( 48 ) of the electroformed diaphragm ( 34, 56 ) is disposed in contact with a piezoelectric transducer ( 20, 82, 84 ) for effecting reciprocal movement of the diaphragm ( 34, 56 ) for alternately contracting and expanding the volume of the ink holding chamber ( 14 ), producing uniform pressure or acoustic waves through ink contained in the chamber ( 14 ) whereby ink menisci in nozzles of a print head in communication with the chamber ( 14 ) are uniformly oscillated.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to a diaphragm fabricated on a substrate such as a silicon wafer or the like, and more particularly, to a metal diaphragm electroformed on a silicon wafer, having utility for a drop-on-demand (DOD) ink jet print head, a capacitive pressure sensor, and other applications wherein a metallic, conductive diaphragm can be used. 
     BACKGROUND OF THE INVENTION 
     Currently, in micro electronic mechanical systems (MEMS), diaphragms are commonly fabricated from silicon, silicon oxide, silicon nitride and combinations of those materials. Shortcomings of such materials, however, include less than desired robustness compared to diaphragms fabricated from metals such as nickel. A silicon diaphragm also has cleavage planes and can be cleaved under some applications. Additionally, increasing the thickness of a silicon oxide or silicon nitride diaphragm has been found to increase the occurrence of internal stresses in the material, whereas by simply changing the integrated plating current, the thickness of an electroformed nickel diaphragm can be increased without a significant increase in internal stress. 
     Ink jet printing has become recognized as a prominent contender in the digitally controlled, electronic printing arena because, e.g., of its non-impact, low noise characteristics, its use of plain paper, and its avoidance of toner transfers and fixing. For these reasons, DOD ink jet printers have achieved commercial success for home and office use. DOD ink jet printers typically operate by subjecting a piezoelectric crystal to a high voltage electrical field, causing the crystal to bend, which in turn applies pressure on a reservoir of ink contained in an ink holding chamber of the print head via a flexible diaphragm, for selectably jetting ink drops on demand through an opposing nozzle or orifice. Typically, piezoelectric DOD printers utilize piezoelectric crystals in a push mode, a shear mode, or a squeeze mode. Piezoelectric DOD printers have achieved commercial success at image resolutions up to 720 dpi for home and office printers. 
     It is desired to fabricate a DOD print head using MEMS techniques which is operable for applying a pressure or acoustic wave to a reservoir of ink for uniformly lifting, raising or otherwise affecting the ink in an array of nozzles or orifices such that the ink can be selectably ejected through the nozzles or orifices using suitable conventional means, such as electrical impulse heaters or the like associated with the individual nozzles or orifices. However, to provide uniform ink ejection across the nozzles or orifices of the array, it has been found that the ink menisci in the respective nozzles or orifices must be uniformly affected by the pressure or acoustic waves. 
     It is believed that a primary cause of the inability to produce uniform waves is poor diaphragm function. Essentially, when the known diaphragm constructions are deflected or deformed into the ink holding chamber for lifting the ink, the diaphragms bend or bow across the length and width thereof, instead of moving as a unitary element. The bending or bowing of the diaphragm results in a domed structure with maximum deflection at the center, which does not produce a uniform pressure wave across the diaphragm. If a waveform produced in the ink is non-uniform, the ink menisci will be correspondingly non-uniform resulting in non-uniform ink droplet production. 
     Thus, what is required is a diaphragm for DOD ink jet print heads and other applications which moves or deflects as a unitary element so as to provide uniform pressure or acoustic wave generation characteristics. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an improved diaphragm for DOD ink jet print heads and other applications which moves or deflects essentially as a unitary element so as to produce a more uniform pressure or acoustic wave, for example, in a body of ink in contact therewith to facilitate more uniform ink drop production. 
     With this object in view, the present invention resides in a diaphragm structure which includes a silicon substrate, such as but not limited to a wafer, having a surface and an opening therethrough, with a metal diaphragm electroformed on the surface and extending over the opening. 
     More particularly, the present invention resides in an ink jet print head including a support element defining at least a portion of a chamber for holding ink, the support element defining an opening adjacent to the chamber, and a diaphragm electroformed on a surface of the support element around the opening at least substantially covering the opening and enclosing the chamber. 
     According to an exemplary embodiment of the present invention, the diaphragm has a central region disposed generally centrally over the opening of the support element and a bellows surrounding the central region, the central region preferably being of greater cross sectional extent than the bellows such that the central region is substantially rigid and the bellows flexible. The central region of the electroformed diaphragm is disposed in contact with or connected to a piezoelectric transducer or actuator energizable for effecting reciprocal movement of the diaphragm for alternately contracting and expanding the volume of the ink holding chamber, producing uniform pressure or acoustic waves through ink contained in the chamber whereby ink menisci in nozzles of the print head in communication with the chamber are uniformly oscillated, lifted or otherwise affected. 
     To facilitate uniform wave generation, the central region of the diaphragm can be thickened relative to the bellows, and/or a stiffening member such as a portion of a silicon wafer mounted or attached thereto. Additionally, the diaphragm can be mounted or affixed to or otherwise brought into contact with the piezoelectric transducer or actuator for oscillating or reciprocating movement therewith. The bellows surrounding the central region of the diaphragm can optionally include one or more elliptical or other shape corrugations to facilitate flexure thereof for uniform displacement of the central region. 
     The present invention also resides in a method for forming a diaphragm for an ink jet print head, including the steps of electroforming at least one metal layer on a predetermined portion of a first surface of an etchable wafer such as a silicon wafer, etch masking a portion of the second surface of the silicon wafer to define an unmasked portion of the wafer underlying a predetermined portion of the at least one metal layer, and etching through the unmasked portion of the wafer to the at least one metal layer. 
     A feature of the present invention is the provision of a diaphragm of electroformed metal which is thin yet sufficiently rigid so as to oscillate without substantial deformation thereof, for generating substantially uniform waves in a body of ink or other fluid disposed in contact with one surface of the diaphragm. 
     Another feature of the present invention is the provision of a unitary diaphragm and surrounding bellows wherein the diaphragm is of greater cross sectional extent than the bellows. 
     Another feature of the present invention is the provision of an electroformed diaphragm including a stiffening member affixed or mounted thereto. 
     According to another aspect of the present invention at least one ink inlet channel can be electroformed on the surface of the support element in position for communicating with a source of ink external or internal to the print head. Additionally, the electroformed metal layer forming the diaphragm can include one or more openings or perforations therethrough for filtering ink that flows through the at least one ink inlet channel. 
     An advantage of the present invention is the ability to move the present diaphragm as a unitary element across substantially the entire length and width thereof for generating substantially uniform waves in a body of ink or other fluid disposed in contact with one surface of the diaphragm. 
     Another advantage of the present invention is the ability to produce a diaphragm in a manner that can be easily incorporated into conventional manufacturing processes for semi-conductor devices and MEMSs using silicon wafers and the like. 
     Another advantage of the present invention is the ability to form a unitary diaphragm and bellows wherein the diaphragm is of greater cross-sectional extent than the bellows. 
     Another advantage of the present invention is the capability to produce a diaphragm and at least one ink inlet channel communicating with a chamber for holding ink using some of the same manufacturing steps. 
     These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there are shown and described illustrative embodiments of the invention. 
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS 
     While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of the invention, it is believed the invention will be better understood from the following detailed description when taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a simplified cross-sectional representation of a prior art ink jet print head including a diaphragm shown deformed by a piezoelectric transducer of the print head; 
     FIG. 2 a  is a simplified cross-sectional representation of a silicon wafer having a strike layer on one surface thereof according to the present invention; 
     FIG. 2 b  is another simplified sectional representation of the silicon wafer of FIG. 2 a  showing a portion of the strike layer masked to define a diaphragm region having a layer of metal electroformed thereon for producing a diaphragm according to the invention and an etch mask on an opposite surface of the wafer; 
     FIG. 2 c  is another simplified sectional representation of the silicon wafer of FIGS. 2 a  and  2   b  showing the portion of the wafer underlying the diaphragm and the masks removed; 
     FIG. 3 a  is a simplified sectional view of another silicon wafer including a strike layer and a pattern dry film resist on one surface thereof defining a bellows and a diaphragm region according to the present invention; 
     FIG. 3 b  is another sectional view of the silicon wafer of FIG. 3 a  showing the surface of the wafer masked around the bellows and diaphragm region and a metal layer electroformed on the bellows and diaphragm region forming a bellows and diaphragm; 
     FIG. 3 c  is another sectional view of the silicon wafer of FIGS. 3 a  and  3   b  showing the mask around the bellows and diaphragm removed and an etch mask applied to an opposite surface of the wafer; 
     FIG. 3 d  is another sectional view of the silicon wafer of FIGS. 3 a  and  3   b  after etching therethrough to the bellows and the diaphragm, and the etch mask and resist removed; 
     FIG. 3 e  is an alternative sectional view of the silicon wafer of FIGS. 3 a  through  3   c  showing the surface opposite the electroformed layer etch masked to allow etching to the bellows to leave a stiffening member attached to the diaphragm; 
     FIG. 3 f  is a sectional view of the silicon wafer of FIG. 3 e  after etching and removal of the etch mask; 
     FIG. 3 g  is an alternative sectional view of the silicon wafer of FIGS. 3 a  through  3   c  showing the bellows masked for electroforming an additional metal layer or layers onto the diaphragm; 
     FIG. 3 h  is a sectional view of the silicon wafer of FIG. 3 g  after electroforming of the additional metal layer or layers thereon and etching; 
     FIG. 4 a  is a front view of another silicon wafer including a metal layer electroformed on the front surface therein defining a diaphragm and bellows and elements disposed on an adjacent region of the electroformed layer forming ink flow channels communicating the diaphragm and bellows with a plurality of ink inlet openings through the metal layer according to the present invention; 
     FIG. 4 b  is a sectional view through the silicon wafer of FIG. 4 a  showing a piezoelectric transducer mounted to the diaphragm and an orifice plate mounted over the diaphragm and the ink flow channels; 
     FIG. 5 is a sectional view of a print head constructed according to the present invention including an alternative piezoelectric transducer embodiment associated therewith; 
     FIG. 6 is a sectional view through a print head according to the present invention showing still another embodiment of a piezoelectric transducer in association therewith; and 
     FIG. 7 is another sectional view of the print head of FIG. 6 showing deflection of the diaphragm thereof by the piezoelectric transducer; 
     FIG. 8 is an enlarged front view of an orifice plate including a closely spaced, offset array of ink ejecting orifices according to the present invention; and 
     FIG. 9 is a fragmentary sectional view of the silicon wafer of FIG. 4 a,  including a plurality of ink inlet openings through the metal layer forming a filter according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art. 
     Therefore, referring to FIG. 1, there is shown a simplified representation of a typical prior art piezoelectric actuated DOD print head  10 . Print head  10  is of laminar construction including a generally planar orifice plate  12  partially defining an ink holding chamber  14  and a plurality of ink ejecting orifices  16  arranged in a linear array communicating with chamber  14  and an orifice  16 . Print head  10  includes a diaphragm  18  disposed opposite orifices  16  enclosing ink holding chamber  14 . Diaphragm  18  is representative of a wide variety of well known diaphragm constructions including, but not limited to, metallic, silicon and polymeric diaphragm constructions. A conventional piezoelectric transducer  20  is disposed adjacent to diaphragm  18  opposite ink holding chamber  14 . Piezoelectric transducer  20  is connected to a source of electrical energy (not shown) in a well known conventional manner and is actuable by the application of an electrical field thereto. When transducer  20  is actuated, diaphragm  18  is alternatingly displaced into ink holding chamber  14  as shown for reducing the interior volume of chamber  14  to effect ejection of ink contained in chamber  14  (not shown) through the orifice  16  in the well known conventional manner. 
     However, an observed shortcoming of the prior art DOD print heads, as represented by print head  10 , is the non-uniform deformation or deflection of diaphragm  18  into ink holding chamber  14 , which has been found to generate corresponding non-uniform pressure or acoustic waves through the ink, resulting in irregular or non-uniform ink droplet production, as discussed hereinabove. This problem has been observed with a variety of prior known diaphragm constructions, including thin membranes, foils and films of a variety of materials such as metals, silicons, polymers and the like. 
     In order to overcome the problem of non-uniform wave generation, the present invention resides in a very thin metal diaphragm electroformed directly onto a surface of a rigid support element such as, but not limited to a silicon wafer, a portion of the material underlying a central portion of the diaphragm being removed, for instance, by etching, such that both opposite surfaces of the diaphragm are exposed, the support element then being laminated or otherwise suitably attached to an orifice plate or an intermediate member in communication with an ink holding chamber of a print head. 
     Referring to FIG. 2 a,  a substantially rigid planar silicon wafer  22  is prepared for receiving an electroformed nickel diaphragm according to the present invention. First, a conductive strike layer  24  is placed on a surface  26  of silicone wafer  22 . Strike layer  24  should be selected so as to adhere well to surface  26  which may comprise pure silicon or silicone dioxide, and so as to adhere well to the selected metal to be electroformed thereover. The strike layer consists of a vacuum deposited subbing layer of chrome, nickel, titanium or other refractory at a thickness of between about 2.5 and about 50 nm, for instance, about 25 nm is satisfactory. A thicker layer of metal such as nickel is then deposited on top of the subbing layer by physical vapor deposition to produce a layer having a thickness of from about 0.1 to about 0.2 microns. If the film is deposited without a significant amount of internal stress, a thicker layer can be used. The subbing layer serves as an adhesion promoting layer commonly used in thin film technology. 
     Referring to FIG. 2 b,  a relatively thick (from about 12.5 to about 75 microns) layer of a dry film photoresist  28  is patterned on strike layer  24  defining a diaphragm region  30 . A metal layer is then electroformed onto the diaphragm region  30  to form a diaphragm  34 . Diaphragm  34  can be electroformed from any metal which provides the desired operational characteristics, such as, but not limited to, nickel. Diaphragm  30  preferably has a thickness of from a few microns to a few tens of microns. An etched mask  36  is then pattern on a surface  38  of silicon wafer  22  opposite surface  26  to define an unmasked region corresponding to a selected portion of diaphragm region  30 . The unmasked portion of surface  38  is then subjected a conventional etching operable for etching silicon wafer  22  until the silicon is removed sufficiently to expose diaphragm  34 . Here, a reason for selecting nickel as the metal for diaphragm  34  becomes apparent, as nickel serves as an etch stop for a variety of etches including alkaline chemical etches such as potassium hydroxide (KOH) based etches, florine based inductively coupled plasma (ICP) etches, and reactive ion etches (RIE). The thickness of diaphragm  34  can be accurately controlled as is well known in the art by controlling plating current and plating time, plating time being the preferred manner of control. 
     Referring to FIG. 2 c,  after photoresist layer  28  and etch mask  36  are removed, diaphragm  34  is disposed in covering relation to an opening  40  etched through wafer  22 , the remaining portion of wafer  22  surrounding opening  40  providing a substantially rigid support element  42  for diaphragm  34 . Support element  42  can then be bonded, fastened or otherwise suitably mounted to an orifice plate such as orifice plate  12  (FIG. 1) with diaphragm  34  located in enclosing relation to an ink holding chamber or reservoir such as chamber  14 , or to a member disposed between the element  42  and the orifice plate. Additionally, as explained in greater detailed below, one or more inlet channels for the passage of ink from an ink source can be formed on adjacent portion of support element  42 , or on the surface of the orifice plate to which support element  42  is to be attached, to provide a pathway for communicating ink to the ink holding chamber or reservoir. Still further, a passage can be etched through support element  42  and holes formed through the metal layer to provide a pathway for communicating with the channels, as will be illustrated hereinafter. 
     Turning to FIG. 3 a,  a method for forming another embodiment of an electroformed diaphragm according to the present invention will be described. In FIG. 3 a,  a dry film or liquid photoresist layer  44  is applied to a surface  26  of a silicon wafer  22 . Photoresist layer  44  consist of a plurality of concentric, progressively larger band shaped elements  46  extending around and defining a central diaphragm region  48  on silicon wafer  22 , successive elements  46  being separated by spaces  50 . Patterned photoresist layer  44  is then heated so as to harden. When heated, the comers of band shaped elements  46  soften and reflow so as to decrease in sharpness, which is desirable as will be explained. A strike layer  52  is applied to surface  26  over band shaped elements  46  of photoresist layer  44 . Strike layer  52  can be similar to the strike layer described above. The preferred method of deposition is physical sputtering, which has been found to provide better sidewall coverage than thermal evaporation. Alternatively, layer  52  can be applied to surface  26  before band shaped elements  46  are applied. 
     Turning to FIG. 3 b,  a photoresist layer  28  is then applied to surface  26  in a pattern extending around the outermost band shaped element  46  and a metal layer  54  of nickel or another suitable metal, is electroformed onto central diaphragm region  48 , band shaped elements  46  and spaces  50  therebetween, thereby forming a diaphragm  56  on central diaphragm region  48  and bellows  58  extending around diaphragm  56 . Bellows  58  includes a plurality of concentric elliptical cross-section corrugations  60 , defined by band shaped elements  46  and spaces  50  (FIG. 3 a ), the rounded comers of band shaped elements  46  contributing to the elliptical shape. 
     Turning to FIG. 3 c,  an etch mask  36  is applied to opposite surface  38  of silicon wafer  22  in a pattern so as to define an unmasked region opposite diaphragm  56  and bellows  58  which is then etched by using a plasma or chemical etch, as explained above, through to diaphragm  56  and bellows  58 , the metal thereof acting as an etch stop. The etch mask  36  and photoresist material of band shape elements  46  are then removed singularly or jointly, for instance, using suitable conventional resist stripping steps. 
     As another step, the strike layer  52 , particularly when not patterned by photoresist layer  44 , can be removed as required using a light etch. Since diaphragm  56  is much thicker than layer  52 , it is not significantly affected by the light etch. 
     FIG. 3 d  shows the now complete diaphragm  56  and surrounding bellows  58 , the remaining portion of silicon wafer  22  extending therearound providing a support element  62 . 
     Turning to FIGS. 3 e  and  3   f,  electroformed diaphragm  56  or diaphragm  34  can be provided with a stiffening member or element for increasing the rigidity thereof. To illustrate using diaphragm  56 , the diaphragm  56  is electroformed as explained above. However, instead of etching away that portion of the silicon wafer underlying the central region of the diaphragm  56 , the portion underlying the central region is masked with etch mask  36  leaving a band shaped unmasked region  64  of surface  38  opposite a circumferential or peripheral portion of diaphragm  56  (here shown opposite bellows  58 ), as shown in FIG. 3 e.  Then, when silicon wafer  22  is etched, only that portion of silicon wafer  22  exposed by unmasked region  64  is removed, leaving support element  62  around bellows  58  and a stiffening member  66  attached to diaphragm  56 . 
     Referring to FIGS. 3 g  and  3   h,  diaphragm  56  can be further or alternatively stiffened before or after the initial electroforming thereof, by masking bellows  58  with a photoresist layer  68 , then electroforming additional metal onto bellows  56  in the above-described manner, such that diaphragm  56  has a greater cross sectional extent as denoted at X in FIG. 3 h  than the cross sectional extent of bellows  58 , as denoted at Y. Here, thicker diaphragm  56  is shown in association with stiffening member  66 , it being likewise contemplated that the thicker diaphragm being usable without the stiffening member, as desired. 
     Referring to FIG. 4 a,  another silicon wafer  22  includes a front surface  26  having a metal layer  32  electroformed thereon to form a diaphragm  56  and a bellows  58  in the above described manner. Metal layer  32  covers an adjacent portion  68  of front surface  26 , and elements  70  and  72  are disposed on metal layer  32  defining a plurality of ink inlet or flow channels  74  communicating an ink inlet region  76  with diaphragm  56  and bellows  58 . Ink inlet region  76  of metal layer  32  includes a plurality of ink inlet openings  78  therethrough communicating with an ink passage  80  (FIG. 4 b ) extending through wafer  22  and adapted for connection in fluid communication with a source of ink (not shown). Alternatively, a single ink inlet opening could be provided, the size of the ink inlet opening or openings being determinable based on the ink flow requirements of a particular application. Elements  70  and  72  can be formed of any suitable material so as to extend above metal layer  32  by an extent sufficient to form ink inlet channels  74  of desired size. For instance, elements  70  and  72  can be formed of metal electroformed onto metal layer  32  in a suitable pattern, a polyimide film layer, or the like. Diaphragm  56  is shown including a stiffening member  66  optionally affixed or mounted thereto. Stiffening member  66  can be composed of any desired material, such as, but not limited to, nickel or silicon, as discussed above. Bellows  58  is shown having an elongate or generally elliptical or oval shape with rounded ends. Such a shape facilitates use in association with a longitudinal array of ink ejecting orifices, such as illustrated in FIGS. 5 and 8, it being contemplated that that a wide variety of other shapes could be used, for instance a rounded or circular shape, as required or desired for use with a particular orifice or array of orifices. The opening over which diaphragm  56  is mounted can have a rectangular or corresponding rounded shape, as desired, a shape such as an ellipse or oval being preferably formed in silicon by dry etching with an ICP source. 
     Turning to FIG. 4 b,  silicon wafer  22  is shown including an orifice plate  12  mounted thereon over elements  70  and  72 , forming an ink holding chamber  14  adjacent to diaphragm  56  and bellows  58 , silicon wafer  22  being masked and etched as explained above in reference to FIGS. 3 e  and  3   f  to form a stiffening member  66  attached to diaphragm  56 , and wafer  22  being masked and etched in a similar manner to form an ink passage  80  therethrough communicating with ink inlet openings  78 . In this regard, ink inlet openings  78  can be relatively small so as to serve to filter ink flow therethrough en route to ink inlet region  76 . Additionally, a piezoelectric transducer  20  is shown attached or mounted to stiffening member  66  for displacing or deflecting diaphragm  56  to effect ejection of ink contained in chamber  14  through orifices  16  of orifice plate  12  in the above described manner. 
     FIG. 5 shows a diaphragm  56  constructed in the above described manner including a stiffening member  66  attached thereto, and an alternative piezoelectric transducer  82 , transducer  82  including longitudinally spaced points  84  attached to or in contact with stiffening member  66 . Piezoelectric transducer  82  can be mounted so as to be adjustably rotatable in a plane parallel to the array of orifices  16  of a print head with which diaphragm  56  is used, to allow tuning the displacement or deflection of diaphragm  56  so as to be more closely uniform from end to end. 
     FIG. 6 shows reinforced diaphragm  56  having yet another alternative piezoelectric transducer  86  in contact with or mounted to stiffening member  66  thereof, transducer  86  having just one point  84  contacting stiffening member  66  at the center thereof to provide uniform displacement of the diaphragm  56  and stiffening member  66 . 
     Here, in the instance of piezoelectric transducers  82  and  86 , points  84  can be formed of the piezoelectric material itself, or from a separate material attached to the piezoelectric material, as desired. Here it should be additionally understood that the thickness of diaphragm  56  and diaphragm  34  as well as stiffening member  66  can be varied to allow altering or adjusting the resonant frequency of the diaphragm or diaphragm assembly to provide a frequency to give the best performance. 
     To illustrate an advantage of the present invention, FIG. 7 shows deflection or displacement of diaphragm  56  of the present invention by piezoelectric transducer  86 , diaphragm  56  remaining substantially planar while bellows  58  is flexed, so as to produce uniform pressure waves throughout ink contained in ink holding chamber  14  and ink menisci in nozzles  16 , as desired. 
     To illustrate another advantage of the present invention, FIG. 8 shows a segment of a front surface of an alternative orifice plate  12  constructed according to the invention including a plurality of orifices  16  arranged in a closely spaced offset array, each orifice  16  including an electrical impulse heater  88  therearound adapted for connection in electrical communication with a source of electrical energy through a control device (both not shown) by conductive paths  90  and  92 . Diaphragms constructed according to the teachings of the present invention such as diaphragms  34  and  56  described hereinabove, facilitate the placement of orifices in closely spaced arrangements such as, but not limited to, that shown, such that a relatively large number of orifices can be provided in a small space. 
     To illustrate another advantage of the present invention, FIG. 9 shows a silicon wafer  22  constructed similarly to that of FIG. 4 b,  including a plurality of ink inlet openings  78  etched through metal layer  32  communicating ink inlet region  76  and a ink inlet channel  74  with ink passage  80 , forming a filter  94 . Openings  78  of filter  94  are large enough to allow a desired flow rate of ink to pass into region  76  but small enough to trap particulates that can clog the ink ejecting orifices. Filter  94  can also serve as a fluidic resistive element. That is, the grid-like pattern of openings  78  can regulate or resist ink flow into region  76 , thereby increasing the efficiency of the pumping of ink into the ink holding chamber. Here, it should be notified that the number and/or the size of openings  78  can be varied to achieve a desired balance of filtration and fluidic resistance. For instance, opening  78  about the same size as the ink ejecting orifices have been found satisfactory. 
     To illustrate a further advantage of the present invention, it should be apparent from the description hereinabove that the diaphragms and ink flow channels according to the invention can be produced using standard CMOS manufacturing techniques and apparatus. 
     Therefore, what is provided is several diaphragm structures and methods of manufacture thereof, operable for producing uniform acoustic or pressure waves through a body of ink in a DOD print head 
     The foregoing describes a number of preferred embodiments of the present invention. Modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the invention. 
     Parts Lists 
       10  print head 
       12  orifice plate 
       14  ink holding chamber 
       16  ink ejecting orifice 
       18  diaphragm 
       20  piezoelectric transducer 
       22  silicon wafer 
       24  strike layer 
       26  surface 
       28  photoresist layer 
       30  diaphragm region 
       32  metal layer 
       34  diaphragm 
       36  etch mask 
       38  surface 
       40  opening 
       42  support element 
       44  photoresist layer 
       46  band shaped element 
       48  central diaphragm region 
       50  space 
       52  strike layer 
       54  metal layer 
       56  diaphragm 
       58  bellows 
       60  corrugation 
       62  support element 
       64  unmasked region 
       66  stiffening member 
       68  adjacent portion 
       70  element 
       72  element 
       74  ink inlet channel 
       76  ink inlet region 
       78  ink inlet opening 
       80  ink passage 
       82  piezoelectric transducer 
       84  point 
       86  piezoelectric transducer 
       88  electrical impulse heater 
       90  conductive path 
       92  conductive path 
       94  filter