Abstract:
The exemplary embodiments describe a semiconductor substrate having microelectronics integrated thereon. In one exemplary embodiment, the semiconductor substrate comprises a plurality of fluid ejecting elements positioned over a substrate. The semiconductor substrate can further comprise one or more fluid feed channel(s) formed in the substrate. The one or more fluid feed channel(s) being configured to deliver fluid to the plurality of fluid ejecting elements. The one or more fluid feed channel(s) are defined at least in part by first and second substantially parallel side walls and first and second non-parallel end walls.

Description:
RELATED APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 09/872,775 entitled “Inkjet Printhead Having A Saw Cut Ink Feed Slots and Method of Fabricating Such an Inkjet Printhead” filed on Jun. 1, 2001 now abandoned, the disclosure of which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Throughout the business world, inkjet printing systems are extensively used for image reproduction. Inkjet printing systems frequently make use of an inkjet printhead mounted within a carriage that is moved back and forth across print media, such as paper. As the printhead is moved across the print media, a control system activates the printhead to deposit or eject ink droplets onto the print media to form images and text. Such systems may be used in a wide variety of applications, including computer printers, plotters, copiers, facsimile machines, and other printing devices. 
     Ink is provided to the printhead by a supply of ink that is either carried by the carriage or mounted to the printing system such that the supply of ink does not move with the carriage. For the case where the ink supply is not carried with the carriage, the ink supply can be in fluid communication with the printhead to the ink supply is connected whereupon the printhead is replenished with ink from the refilling station. 
     For the case where the ink supply is carried with the carriage, the ink supply may be integral with the printhead whereupon the entire printhead and ink supply is replaced when ink is exhausted. Alternatively, the ink supply can be carried with the carriage and be separately replaceable from the printhead. 
     For convenience, the concepts of the invention are discussed in the context of thermal inkjet printheads. A thermal inkjet printhead die includes an array of firing chambers having orifices (also called nozzles) which face the print media. The ink is applied to individually addressable ink energizing or ejecting elements (such as firing resistors) within the firing chambers. Energy provided by the firing resistors heats the ink within the firing chambers causing the ink to bubble. This in turn causes the ink to be expelled out of the orifice of the firing chamber toward the print media. As the ink is expelled, the bubble collapses and more ink is drawn into the firing chambers, allowing for repetition of the ink expulsion process. 
     Inkjet printhead dies are in part manufactured using processes that employ photolithographic techniques similar to those used in semiconductor manufacturing. The components are constructed on a flat substrate layer of silicon by selectively adding layers of various materials and subtracting portions of the substrate layer and added layers using these photolithographic techniques. Some existing inkjet printhead dies are defined by a silicon substrate layer having firing resistors within a stack of thin film layers, a barrier layer and an orifice layer or orifice plate. Material removed from the barrier layer defines the firing chambers, while openings within the orifice layer or plate define the nozzles for the firing chambers. 
     In an inkjet printhead die, ink is delivered to the firing chambers and thereby the firing resistors by either a slotted ink delivery system or an edgefeed ink delivery system. In a slotted ink delivery system, the inkjet printhead die includes one or more slots that route ink from a backside of the printhead die to a front side where the firing resistors reside on at least one side of each of the slots. To form the ink feed slots of the printhead die, material is typically removed from the silicon substrate layer by directing a high pressure mixture of sand and air at the silicon substrate layer. 
     Generally, a single color printhead die includes a single ink delivery slot with one column of firing resistors on each side of the slot. However, a single color printhead die may include multiple slots to improve print quality and/or speed. A multicolor printhead die typically includes an ink delivery slot for each color. Generally, the printhead die is mounted to a printhead cartridge body using a structural adhesive. In multicolor print cartridges having a printhead die with multiple slots, this structural adhesive is deposited in a loop around each individual slot to separate out the individual ink colors. 
     Although this slotted ink delivery system for inkjet printhead dies adequately delivers ink to the firing resistors, there are some disadvantages to this system of ink routing. The primary disadvantages are die strength, size and manufacturing inefficiencies. With regard to strength, in a printhead die, the ink delivery slot(s) structurally weaken the printhead die. As such, the greater the size of the slots and/or the greater the number of slots the weaker the die. With regard to size, the ink delivery slots can only be put so close together before manufacturability issues arise that causes manufacture of the printhead die to be accomplished in less than an optimal cost efficient manner. As such, the width of the ink delivery slots and the spacing of the ink delivery slots limits how small the printhead die can be. Lastly with regard to manufacturing inefficiencies, use of the high pressure mixture of sand and air to form the ink feed slots in the printhead die limits the overall size of the individual slots. For example, to produce an ink delivery slot having a width of less than 300 μm and a length greater than 5000 μm can require huge increases in manufacturing cycle times along with reductions in manufacturing yields. As such, due to the inherent limitations of the high pressure sand and air ink feed slot formation process, this process is only economically feasible to produce ink feed slots having widths of greater than 300 μm and lengths less than 5000 μm. 
     Typically to obtain print quality and speed, it is necessary to maximize the density of the firing chambers (i.e. firing resistors) and/or increase the number of firing chambers. Maximizing the density of the firing chambers and/or increasing the number of firing chambers typically necessitates an increase in the size of the printhead die and/or a miniaturization of printhead die components. As discussed above, when the density is sufficiently high, conventional manufacturing by assembling separately produced components becomes more difficult and costly. In addition, the substrate that supports firing resistors, the barrier that isolates individual resistors, and the orifice plate that provides a nozzle above each resistor are all subject to small dimensional variations that can accumulate to limit miniaturization. Further, the assembly of such components for conventional printheads requires precision that limits manufacturing efficiency. 
     As such, there is a desire to form improved slotted substrates that can be incorporated into various fluid ejecting devices and printing devices. An example of which can be a printhead die employing a slotted ink delivery system that is economical to manufacture, and relatively simple to incorporate into inkjet printhead cartridges useable in thermal inkjet printing systems. In particular, the printhead die and the process for manufacturing the printhead die should allow the formation of ink feed slots having widths less than 300 μm and/or lengths greater than 5000 μm while maintaining manufacturing efficiencies. Moreover, the printhead die and the process for manufacturing the printhead die should allow an overall reduction in the size of the printhead die while maintaining the same number of firing resistors or allow more firing resistors to be included in the same printhead die size. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principals of the invention. Other embodiments of the present invention and many of the intended advantages of the present invention will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof, and wherein: 
     FIG. 1 is a perspective view of a thermal inkjet printing system with a cover opened to show a plurality of replaceable ink containers and a plurality of replaceable inkjet printhead cartridges incorporating inkjet printhead dies having printhead substrates in accordance with the present invention. 
     FIG. 2 is a perspective view a portion of a scanning carriage showing the replaceable ink containers positioned in a receiving station that provides fluid communication between the replaceable ink containers and one or more printhead cartridges incorporating inkjet printhead dies having printhead substrates in accordance with the present invention. 
     FIG. 3A is a partial sectional view of the inkjet printhead die having a printhead substrate in accordance with the present invention shown mounted to a multicolor inkjet printhead cartridge of FIG.  1 . 
     FIG. 3B is a partial sectional view similar to FIG. 3A of the inkjet printhead die having a printhead substrate in accordance with the present invention shown mounted to a single color inkjet printhead cartridge of FIG.  1 . 
     FIG. 4 is an enlarged plan view of the inkjet printhead die shown in FIG.  3 . 
     FIG. 5 is a side elevational view illustrating a preferred method of fabricating an ink feed slot in the printhead substrate of the inkjet printhead die in accordance with the present invention. 
     FIG. 6 is a side elevational view similar to FIG. 5 illustrating an alternative method of fabricating an ink feed slot in the printhead substrate of the inkjet printhead die in accordance with the present invention. 
     FIG. 7 is an enlarged partial side sectional view illustrating the ink feed slot in the printhead substrate formed using the methods of fabrication illustrated in FIG. 5 or  6 . 
     FIG. 8 is an enlarged partial end sectional view taken along line  8 — 8  in FIG. 7 illustrating the ink feed slot in the printhead substrate formed using the methods of fabrication illustrated in FIG. 5 or  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A replaceable inkjet printhead cartridge  16  useable in a thermal inkjet printing system  10  in accordance with the present invention is illustrated generally in FIGS. 1-4. The printhead cartridge  16  includes a printhead die  40  that delivers fluid to firing resistors  70  positioned within the printhead die  40  using a slotted ink delivery system. 
     In FIG. 1, the printing system  10 , shown with its cover open, includes at least one replaceable fluid container  12  that is installed in a receiving station  14 . In one preferred embodiment, the printing system  10  includes two replaceable fluid containers  12 , with one single color fluid container  12  containing a black ink supply, and one multi-color fluid container  12  containing cyan, magenta and yellow ink supplies. With the replaceable fluid containers  12  properly installed into the receiving station  14 , fluid, such as ink, is provided from the replaceable fluid containers  12  to at least one inkjet printhead cartridge  16 . In one preferred embodiment, the printing system  10  includes two replaceable printhead cartridges  16 , with one single color printhead cartridge  16  for printing from the black ink supply, and one multi-color printhead cartridge  16  for printing from the cyan, magenta and yellow ink supplies. 
     In operation, the inkjet printhead cartridges  16  are responsive to activation signals from a printer portion  18  to deposit fluid on print media  22 . As fluid is ejected from the printhead cartridges  16 , the printhead cartridges  16  are replenished with fluid from the fluid containers  12 . In one preferred embodiment, the replaceable fluid containers  12 , receiving station  14 , and the replaceable inkjet printhead cartridges  16  are each part of a scanning carriage  20  that is moved relative to the print media  22  to accomplish printing. The printer portion  18  includes a media tray  24  for receiving the print media  22 . As the print media  22  is stepped through a print zone, the scanning carriage  20  moves the printhead cartridges  16  relative to the print media  22 . Each printhead cartridge  16  has an inkjet printhead die  40 . The printer portion  18  selectively activates the printhead dies  40  (see FIGS. 3A,  3 B and  4 ) of the printhead cartridges  16  to deposit fluid on print media  22  to thereby accomplish printing. 
     The scanning carriage  20  of FIG. 1 slides along a slide rod  26  to print along a width of the print media  22 . A positioning means (not shown) is used for precisely positioning the scanning carriage  20 . In addition, a paper advance mechanism (not shown) moves the print media  22  through a print zone as the scanning carriage  20  is moved along the slide rod  26 . Electrical signals are provided to the scanning carriage  20  for selectively activating the printhead dies  40  of the printhead cartridges  16  by means of an electrical link, such as a ribbon cable  28 . 
     FIG. 2 is a perspective view of a portion of the scanning carriage  20  showing the pair of replaceable fluid containers  12  properly installed in the receiving station  14 . For clarity, only a single inkjet printhead cartridge  16  is shown in fluid communication with the receiving station  14 . As seen in FIG. 2, each of the replaceable fluid containers  12  includes a latch  30  for securing the replaceable fluid container  12  to the receiving station  14 . In addition, the receiving station  14  includes a set of keys  32  that interact with corresponding keying features (not shown) on the replaceable fluid containers  12 . The keying features on the replaceable fluid containers  12  interact with the keys  32  on the receiving station  14  to ensure that the replaceable fluid containers  12  are compatible with the receiving station  14 . 
     As seen in FIG. 3A, the tri-color printhead cartridge  16  includes a cartridge body  42  having partition walls  44  and  46  that separate the cartridge body  42  into three separate chambers  48 ,  50  and  52 . The first chamber  48  includes a first capillary member  54  for a first ink color (i.e., cyan), the second chamber  50  includes a second capillary member  56  for a second ink color (i.e., magenta), and the third chamber  52  includes a third capillary member  58  for a third ink color (i.e., yellow). The first, second and third capillary members  54 ,  56 ,  58  receive their respective color ink from the tri-color fluid container  12 . 
     In FIG. 3B, the cartridge body  42  of the single color inkjet printhead cartridge  16  includes a single chamber  60  having a single capillary member  62  for a single color. In one preferred embodiment, this single color is black. The single capillary member  62  receives its respective color ink from the single color fluid container  12 . 
     As seen in FIGS. 3A and 3B each of the tri-color (FIG. 3A) and single color (FIG. 5A) inkjet printhead cartridges  16  includes one inkjet printhead die  40  in accordance with the present invention. Because the printhead dies  40  of the single color and tri-color printhead cartridges  16  are similar only the printhead die  40  in connection with the tri-color printhead cartridge  16  of FIG. 3A will be described with particularity. 
     As seen in FIG. 3A, the inkjet printhead die  40  of the present invention functions to eject ink droplets  64  onto a print medium  22 . The printhead die  40  is defined by a substrate  66  that includes a base layer, such as a semiconductor silicon substrate  68  in accordance with the present invention. The silicon substrate  68  has a first major surface  65  and an opposite second major surface  67 . The silicon substrate  68  (i.e., base layer) provides a rigid chassis for the printhead die  40 , and accounts for the majority of the thickness of the printhead die  40 . On top of the silicon substrate  68  are a plurality of independently addressable ink energizing elements, such as firing resistors  70  (shown in FIG. 4) for heating ink to generate the ink droplets  64  in a known manner. In one preferred embodiment, the firing resistors  70  form part of a stack of thin film layers on top of the silicon substrate  68 . On top of the silicon substrate  68  is a barrier layer  76 , such as a photoresist polymer substrate. On top of the barrier layer  76  is an orifice plate  78 , such as a Ni substrate. 
     As seen in FIG. 4, the die  40  has short side edges  74 . The firing resistors  70  are electrically linked (not shown) to electrical interconnects  72  on the short side edges  74 . In a known manner, the electrical interconnects  72  contact printer portion  18  contacts (not shown) to provide the energizing signals to the firing resistors  70 . 
     As seen in FIGS. 3A and 4, the orifice plate  78  includes a plurality of nozzles  80  through which the ink droplets  64  are ejected. One nozzle  80  is associated with each firing resistor  70 . The barrier layer  76  defines a plurality of firing chambers  82  for the firing resistors  70 . One nozzle  80  and one firing resistor  70  is associated with each firing chamber  82 . The barrier layer  76  also defines a plurality of ink feed passageways  84  (See FIG. 4) for delivering ink to the firing chambers  82 . In one preferred embodiment, one ink feed passageway  84  is associated with each firing chamber  82 . Alternatively, multiple ink feed passageways  84  could be associated with each firing chamber  82 . As seen in FIG. 3A, in one embodiment, the orifice plate  78  may be oversized (i.e., larger than the barrier layer  76  and the silicon substrate  68 ) to allow the inkjet printhead die  40  to be mounted to the cartridge body  42  using a suitable adhesive  86 . 
     As seen in FIG. 3A, the silicon substrate  68  defines first, second and third ink refill channels  88 ,  90  and  92 , respectively, in accordance with the present invention, for delivering ink to the plurality of ink feed passageways  84  and ultimately to the firing chambers  82  for the firing resistors  70 . The first ink refill channel  88  is defined by a first ink feed slot  94  extending through the silicon substrate  68  from the first major surface  65  to the second major surface  67 . The second ink refill channel  90  is defined by a second ink feed slot  96  extending through the silicon substrate  68  from the first major surface  65  to the second major surface  67 . The third ink refill channel  92  is defined by a third ink feed slot  98  extending through the silicon substrate  68  from the first major surface  65  to the second major surface  67 . As seen in FIG. 4, the first, second and third ink feed slots  94 ,  96 ,  98  extend parallel to one another. 
     As seen in FIG. 4, the first ink feed slot  94  is operatively associated with a first multiplicity or at least one column of firing resistors  70 . In one preferred embodiment, the first ink feed slot  94  is operatively associated with a first multiplicity of firing resistors  70  defined by two columns  100  and  101  of firing resistors  70  immediately adjacent to each side of the slot  94 . The second ink feed slot  96  is operatively associated with a second multiplicity or at least one column of firing resistors  70 . In one preferred embodiment, the second ink feed slot  96  is operatively associated with a second multiplicity of firing resistors  70  defined by two columns  102  and  103  of firing resistors  70  immediately adjacent to each side of the slot  96 . The third ink feed slot  98  is operatively associated with a third multiplicity or at least one column of firing resistors  70 . In one preferred embodiment, the third ink feed slot  98  is operatively associated with a third multiplicity of firing resistors  70  defined by two columns  104  and  106  of firing resistors  70  immediately adjacent to each side of the slot  98 . 
     For the tricolor printhead cartridge, the first, second and third ink feed slots  94 ,  96 ,  98  fluidically communicate with the first, second and third capillary members  54 ,  56 ,  58 , respectively, such that the first set of columns  100 ,  101  of firing resistors  70  eject a first ink color (i.e., cyan), the second set of columns  102 ,  103  of firing resistors  70  eject a second ink color (i.e., magenta), and the third set of columns  104 ,  106  of firing resistors  70  eject a third ink color (i.e., yellow). In the single color inkjet printhead cartridge  16  of FIG. 3B there is only a single capillary member  62  with which all the ink feed slots  94 ,  96 ,  98  fluidically communicate. As such, the first, second, third sets of columns  100 ,  101 ,  102 ,  103 ,  104 ,  106  of firing resistors  70  all eject a single ink color (i.e., black). 
     FIG. 5 is a side elevational view illustrating a preferred method of fabricating the ink feed slots  94 ,  96 , and  98  in the printhead silicon substrate  68  of the inkjet printhead die  40  in accordance with the present invention. All the ink feed slots  94 ,  96 ,  98  are formed in the same manner so only to formation of the ink feed slot  94  will be described with particularity. As seen in FIG. 5, the ink feed slot  94  is cut in the silicon substrate  68  using a cutting saw, such as a rotating (i.e., rotary) cutting saw  110 . The rotary cutting saw  110  has a diamond encrusted peripheral cutting edge  112  that performs the cutting operation upon rotation of the rotary cutting saw  110  in a clockwise direction  114 . 
     In practice, to perform the preferred method of fabrication in accordance with the present invention, an adhesive tape  116  is first applied to the second major surface  67  of the silicon substrate  68 . The adhesive tape  116  allows for easier handling of the silicon substrate  68 , provides a cushion during the actual cutting process, reduces vibration during the cutting process, and reduces unwanted chipping during the cutting process. 
     Once the adhesive tape  116  is applied to the silicon substrate  68 , the silicon substrate  68  with the attached tape  116  is placed into position atop a fixture  118  beneath the rotary cutting saw  110  such that the first major surface  67  of the silicon substrate  68  faces the saw  110 . The silicon substrate  68  is held in a fixed position relative to the rotary cutting saw  110  atop the fixture  118  via vacuum pressure  120  provided by a vacuum source  122 . In one embodiment, the fixture  118  includes apertures  124  that allow the vacuum pressure  120  to act on the tape  116  on the second major surface  67  of the silicon substrate  68  to hold the substrate  68  in the desired position. 
     With the silicon substrate  68  held in a fixed position, the rotary cutting saw  110  is turned on to rotate the saw  110  in clockwise direction  114 . Next the rotary cutting saw  110  is lowered in a vertical direction to engage and plunge cut (see dashed line representation  110   a  of the saw  110 ) the silicon substrate  68 . In particular, the rotary cutting saw  110  is moved in a first direction  126  perpendicular to the first major surface  65  of the silicon substrate  68  to partially form the ink feed slot  94 . The saw  110  is only lowered to the adhesive tape  116 . Next, the rotary cutting saw  110  is moved horizontally to drag cut (see dashed line representation  110   b  of the saw  110 ) the silicon substrate  68 . In particular, the rotary cutting saw  110  is moved in a second direction  128  parallel to the first major surface  65  of the silicon substrate  68  to complete formation of the ink feed slot  94 . Once the slot  94  is formed, the rotary cutting saw  110  is moved back to its starting position (shown in solid lines in FIG. 5) along horizontal direction  130  and vertical direction  132 , the vacuum source  122  is turned off and the silicon substrate  68  is removed from the fixture  118  to complete the ink feed slot formation process. The silicon substrate  68  is then combined with other elements of the printhead die  40  in a known manner to complete the printhead assembly process. 
     As seen in FIGS. 7 and 8, the above method of fabrication produces an ink feed slot  94  defined by first and second parallel side walls  140  and  142 , respectfully, and first and second, non-linear, non-parallel end walls  144  and  146 , respectfully. In particular, the first and second end walls  144 ,  146  are not perpendicular to the first and second major surfaces  65 ,  67  of the silicon substrate  68 . Specifically the first and second end walls  144 ,  146  are curved such that the first end wall  144  is defined by a first arc having a first radius of curvature, and the second end wall  146  is defined by a second arc having a second radius of curvature that is substantially equal to the first radius of curvature. These curved end walls  144 ,  146  have been shown to produce a stronger silicon substrate  68  then that produced using conventional slot formation techniques that produce end walls that are linear, parallel and perpendicular to the major surfaces of the silicon substrate. In one preferred embodiment, a two inch diameter rotary cutting saw  110  is used to form the slot  94  which produces end walls  144 ,  146  having a one inch radius of curvature. 
     As seen in FIGS. 7 and 8, in accordance with the present invention, the rotary cutting saw  110  produces an ink feed slot  94  having a width dimension W defined as the distance between the first and second side walls  140 ,  142  and a length dimension L defined as the distance between median of the first and second end walls  144 ,  146 . As is readily understood, the rotary cutting saw  110  produces a slot  94  as wide as the thickness of the saw  110 . As such, an ink feed slot  94  having a width dimension W as small as 15 μm can be formed in the silicon substrate  68 . In particular, the rotary cutting saw  110  can be used to produce an ink feed slot  94  having a width dimension W of at least 15 μm and less than 300 μm. In one preferred embodiment the width dimension W is 200 μm. In addition, as is readily apparent, the rotary cutting saw  110  can be used to produce an ink feed slot  94  of almost any length dimension L of at least 5000 μm. Typically, the rotary cutting saw  110  is used to form an ink feed slot  94  having a length dimension L of at least 8000 μm. In one preferred embodiment the length dimension L is 8750 μm. 
     FIG. 6 is a side elevational view similar to FIG. 5 illustrating an alternative method of fabricating the ink feed slot  94  (as well as the ink feed slots  96 ,  98 ) in the printhead silicon substrate  68  of the inkjet printhead die  40  in accordance with the present invention. As with the preferred fabrication embodiment, the tape  116  is applied to the silicon substrate  68  and the silicon substrate is held in a fixed position on the fixture  118  via vacuum pressure  120  provided by the vacuum source  122 . 
     With the silicon substrate  68  held in a fixed position, the rotary cutting saw  110  is turned on to rotate the saw  110  in clockwise direction  114 . Next the rotary cutting saw  110  is only lowered in a vertical direction to engage and plunge cut (see dashed line representation  110   c  of the saw  110 ) the silicon substrate  68 . The saw  110  is lowered so as to pass completely through the tape  116  and into a slot  117  formed in the fixture  118  to accommodate the saw  110 . In particular, the rotary cutting saw  110  is moved only in the first direction  126  perpendicular to the first major surface  65  of the silicon substrate  68  to completely form the ink feed slot  94 . Once the slot  94  is formed, the rotary cutting saw  110  is moved back to its starting position (shown in solid lines in FIG. 6) along the vertical direction  132 , the vacuum source  122  is turned off and the silicon substrate  68  is removed from the fixture  118  to complete the ink feed slot formation process. The silicon substrate  68  is then combined with other elements of the printhead die  40  in a known manner to complete the printhead assembly process. 
     This printhead die  40  having a silicon substrate  68  produced in accordance with the present invention, substantially minimizes the size, strength and manufacturing efficiency issues associated with present slotted printhead dies. In particular, the use of a rotary cutting saw  110  to form the ink delivery slots  94 ,  96 ,  98  in the substrate  68  of the printhead die  40  produces narrower ink delivery slots while maintaining manufacturing efficiencies. Specifically, the rotary cutting saw  110  can be used to form an ink delivery slot  94 ,  96 ,  98  having a width of as small as 15 μm. Smaller ink delivery slot widths allows the printhead substrate  68  of the present invention to exhibit an overall size reduction, as well as an increase in strength. An increase in strength of the printhead substrate is also exhibited due to the curved end walls  144 ,  146  of the ink delivery slot  94 ,  96 ,  98  produced during the fabrication process as a result of the use of the rotary cutting saw  110 . In addition, the rotary cutting saw  110  can be used to produce ink delivery slots  94 ,  96 ,  98  of greater lengths while maintaining manufacturing efficiencies. Specifically, the rotary cutting saw  110  can be used to form an ink delivery slot  94 ,  96 ,  98  having a length greater than 5000 μm. Moreover, the printhead die  40  incorporating the substrate  68  of the present invention provides the above features throughout the useful life of the printhead cartridge  16  to which the printhead die  40  is mounted so as to preclude premature replacement of the printhead cartridge  16  and the associated cost. Lastly, the printhead die  40  of the present invention is relatively easy and inexpensive to manufacture, and is relatively simple to incorporate into printhead cartridges  16  used in thermal inkjet printing systems  10 . 
     Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.