Abstract:
Disclosed is a flexible circuit that has a nozzle member formed therein with the nozzle member including a plurality of ink orifices and the flexible circuit having electrical leads. A substrate containing a plurality of heating elements and associated ink ejection chambers and having electrodes to which the electrical leads are bonded is mounted on a back surface of the nozzle member. Each heating element is located proximate to an associated ink orifice with the back surface of the nozzle member extending over two or more outer edges of the substrate. A print cartridge body having a headland portion is located proximate to the back surface of the nozzle member and includes an inner raised wall circumscribing the substrate with an adhesive support surface formed thereon and having wall openings therein. The wall openings have an adhesive support surface and an elevated substrate support surface raised above the adhesive support surface for supporting the substrate. An adhesive layer is located between the back surface of the nozzle member and the headland to affix the nozzle member to the headland. The adhesive layer located on the adhesive support surface of the inner raised wall and along the adhesive support surface within the wall openings therein and on the elevated substrate support surface, so as to encapsulate the ends of the substrate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application relates to the subject matter disclosed in the following U.S. patent application and U.S. patents: 
     U.S. patent application Ser. No. 09/302,837, filed concurrently herewith, entitled “Inkjet Print Cartridge Design to Decrease Ink Shorts Due to Ink Penetration of the Printhead; 
     U.S. Pat. No. 5,852,460, entitled “Inkjet Print Cartridge Design to Decrease Deformation of the Printhead When Adhesively Sealing The Printhead to the Print Cartridge;” 
     U.S. Pat. No. 5,736,998, entitled “Inkjet Cartridge Design for Facilitating the Adhesive Sealing of a Printhead to an Ink Reservoir;” 
     U.S. Pat. No. 5,450,113, entitled “Adhesive Seal for an Inkjet Printhead;” 
     U.S. Pat. No. 5,442,384, entitled “Integrated Nozzle Member and TAB Circuit for Inkjet Printhead;” 
     U.S. Pat. No. 5,278,584 to Keefe, et al., entitled “Ink Delivery System for an Inkjet Printhead;” and 
     U.S. Pat. No. 5,291,226, entitled “Nozzle Member Including Ink Flow Channels.” 
     The above patents are assigned to the present assignee and are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention generally relates to inkjet printers and, more particularly, to the printhead portion of an inkjet print cartridge. 
     BACKGROUND OF THE INVENTION 
     Inkjet printers have gained wide acceptance. These printers are described by W. J. Lloyd and H. T. Taub in “Ink Jet Devices,” Chapter 13 of  Output Hardcopy Devices  (Ed. R. C. Durbeck and S. Sherr, San Diego: Academic Press, 1988) and U.S. Pat. Nos. 4,490,728 and 4,313,684. Inkjet printers produce high quality print, are compact and portable, and print quickly and quietly because only ink strikes the paper. 
     An inkjet printer forms a printed image by printing a pattern of individual dots at particular locations of an array defined for the printing medium. The locations are conveniently visualized as being small dots in a rectilinear array. The locations are sometimes “dot locations”, “dot positions”, or pixels”. Thus, the printing operation can be viewed as the filling of a pattern of dot locations with dots of ink. 
     Inkjet printers print dots by ejecting very small drops of ink onto the print medium and typically include a movable carriage that supports one or more printheads each having ink ejecting nozzles. The carriage traverses over the surface of the print medium, and the nozzles are controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controller, wherein the timing of the application of the ink drops is intended to correspond to the pattern of pixels of the image being printed. 
     The typical inkjet printhead (i.e., the silicon substrate, structures built on the substrate, and connections to the substrate) uses liquid ink (i.e., dissolved colorants or pigments dispersed in a solvent). It has an array of precisely formed nozzles attached to a printhead substrate that incorporates an array of firing chambers which receive liquid ink from the ink reservoir. Each chamber has a thin-film resistor, known as a inkjet firing chamber resistor, located opposite the nozzle so ink can collect between it and the nozzle. The firing of ink droplets is typically under the control of a microprocessor, the signals of which are conveyed by electrical traces to the resistor elements. When electric printing pulses heat the inkjet firing chamber resistor, a small portion of the ink next to it vaporizes and ejects a drop of ink from the printhead. Properly arranged nozzles form a dot matrix pattern. Properly sequencing the operation of each nozzle causes characters or images to be printed upon the paper as the printhead moves past the paper. 
     The ink cartridge containing the nozzles is moved repeatedly across the width of the medium to be printed upon. At each of a designated number of increments of this movement across the medium, each of the nozzles is caused either to eject ink or to refrain from ejecting ink according to the program output of the controlling microprocessor. Each completed movement across the medium can print a swath approximately as wide as the number of nozzles arranged in a column of the ink cartridge multiplied times the distance between nozzle centers. After each such completed movement or swath the medium is moved forward the width of the swath, and the ink cartridge begins the next swath. By proper selection and timing of the signals, the desired print is obtained on the medium. 
     In U.S. Pat. No. 5,442,384, entitled “Integrated Nozzle Member and TAB Circuit for Inkjet Printhead,” a novel nozzle member for an inkjet print cartridge and method of forming the nozzle member are disclosed. A flexible circuit tape having conductive traces formed thereon has formed in it nozzles or orifices by Excimer laser ablation. The resulting flexible circuit having orifices and conductive traces may then have mounted on it a substrate containing heating elements associated with each of the orifices. The conductive traces formed on the back surface of the flexible circuit are then connected to the electrodes on the substrate and provide energization signals for the heating elements. A barrier layer, which may be a separate layer or formed in the nozzle member itself, includes vaporization chambers, surrounding each orifice, and ink flow channels which provide fluid communication between a ink reservoir and the vaporization chambers. 
     In U.S. Pat. No. 5,648,805, entitled “Adhesive Seal for an Inkjet Printhead,” a procedure for sealing an integrated nozzle and flexible or tape circuit to a print cartridge is disclosed. A nozzle member containing an array of orifices has a substrate, having heater elements formed thereon, affixed to a back surface of the flexible circuit. Each orifice in the flexible circuit is associated with a single heating element formed on the substrate. The back surface of the flexible circuit extends beyond the outer edges of the substrate. Ink is supplied from an ink reservoir to the orifices by a fluid channel within a barrier layer between the flexible circuit and the substrate. In either embodiment, the flexible circuit is adhesively sealed with respect to the print cartridge body by forming an ink seal, circumscribing the substrate, between the back surface of the flexible circuit and the body. This method and structure of providing a seal directly between a flexible circuit and an ink reservoir body has many advantages. 
     However, during manufacturing, the headland design of previous print cartridges had several disadvantages, including difficulty in controlling the edge seal to the die or substrate without having adhesive getting into the nozzle and clogging them, or on the other hand, voids of adhesive in the flexible circuit bond window. It was also very difficult to control the adhesive bulge through the window caused by excess adhesive, or varying die placement. All of these problems result in extremely high yield losses when manufacturing thermal inkjet print cartridges. 
     U.S. Pat. No. 5,736,998, entitled “Inkjet Cartridge Design for Facilitating the Adhesive Sealing of a Printhead to an Ink Reservoir,” and U.S. Pat. No. 5,852,460, entitled “Inkjet Print Cartridge Design to Decrease Deformation of the Printhead When Adhesively Sealing The Printhead to the Print Cartridge;” improved headland designs are disclosed which alleviate some of the above-mentioned problems. 
     However, these designs did not address the problem of ink shorts caused by ink leaking into the conductive leads and conductive traces of the flexible circuit. Flexible circuit leads are bonded to pads or electrodes on the outer edges of the substrate. To enable this bonding, a window is created in the flexible circuit to allow a bonder thermode to apply force and temperature to the flexible circuit leads that are resting on the bond pads. After the leads have been bonded, an encapsulant is dispensed across the window to protect the exposed bond pad region from intrusion of ink or contamination. 
     On most flexible circuits these leads are also protected on the back side by a laminated cover layer. In addition, the leads are further protected by the structural adhesive that is used to adhere the flexible circuit to the print cartridge body. However, there are a number of disadvantages to this approach. First, there is a region at both ends of the substrate where the flexible circuit traces may not be protected by the cover layer. In this region, the traces are only protected by the structural adhesive and are therefore susceptible to corrosion and electrical shorting if ink penetrates the structural adhesive to flexible tape interface. This penetration of ink is increased due to the fact that the flexible tape to structural interface may provide a wicking surface for the ink if delamination of the flexible tape occurs. This can lead to corrosion and electrical shorting behind the substrate. Second, air pockets may be created on the underside of the flexible tape near the ends of the substrate when the structural adhesive does not squish uniformly against the flexible circuit during attachment of the flexible circuit to the print cartridge body. These air pockets can provide a path for ink to the flexible circuit traces or the bond pad region and thus lead to corrosion and electrical shorting of the leads or traces. 
     Previous solutions to the ink shorts problem have focused on (1) improving the chemical and mechanical robustness of the adhesive materials and interfaces and (2) modifying the design on top of the substrate, the layout and geometry of the thin film, thick film and the TAB bond window opening. While considerable gains have been made in both of these areas, they are limited in their effectiveness and additional robustness margin is desired. 
     Accordingly, there is a need for an improved method of encapsulating the flexible circuit leads that reduces ink shorts and corrosion due to ink penetration into the flexible circuit leads. 
     SUMMARY OF THE INVENTION 
     In a preferred embodiment, a flexible circuit has a nozzle member formed therein with the nozzle member including a plurality of ink orifices and the flexible circuit having electrical leads. A substrate containing a plurality of heating elements and associated ink ejection chambers and having electrodes to which the electrical leads are bonded is mounted on a back surface of the nozzle member. Each heating element is located proximate to an associated ink orifice with the back surface of the nozzle member extending over two or more outer edges of the substrate. A print cartridge body having a headland portion is located proximate to the back surface of the nozzle member and includes an inner raised wall circumscribing the substrate with an adhesive support surface formed thereon and having wall openings therein. The wall openings have an adhesive support surface and an elevated substrate support surface raised above the adhesive support surface for supporting the substrate. An adhesive layer is located between the back surface of the nozzle member and the headland to affix the nozzle member to the headland. The adhesive layer located on the adhesive support surface of the inner raised wall and along the adhesive support surface within the wall openings therein and on the elevated substrate support surface, so as to encapsulate the ends of the substrate. 
     The invention further includes a method of affixing a flexible circuit to an inkjet print cartridge body including providing a flexible circuit having a nozzle member formed therein with a plurality of ink orifices and the with the flexible circuit having electrical leads. The flexible circuit has a substrate mounted on a back surface of the nozzle member. The substrate has a plurality of heating elements and associated ink ejection chambers and electrodes to which the electrical leads are bonded. Each heating element is located proximate to an associated ink orifice and the back surface of the nozzle member extends over two or more outer edges of the substrate. Providing a print cartridge body having a headland portion located proximate to the back surface of the nozzle member and including an inner raised wall circumscribing the substrate. The inner raised wall has an adhesive support surface formed thereon and wall openings therein. The wall openings have an adhesive support surface and an elevated substrate support surface raised above the adhesive support surface for supporting the substrate. Dispensing an adhesive layer between the back surface of the nozzle member and the headland to affix the nozzle member to the headland. The adhesive layer is located on the adhesive support surface of the inner raised wall, along the adhesive support surface within the wall openings therein and on the elevated substrate support surface. Positioning the back surface of the nozzle member with respect to the headland such that the adhesive circumscribes the substrate and affixes the back surface of the nozzle member to the headland so as to encapsulate the ends of the substrate with adhesive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an inkjet print cartridge according to one embodiment of the present invention. 
     FIG. 2 is a plan view of the front surface of a Tape Automated Bonding (TAB) printhead assembly (hereinafter “TAB head assembly”) removed from a print cartridge. 
     FIG. 3 is a highly simplified perspective view of the back surface of the TAB head assembly of FIG. 2 with a silicon substrate mounted thereon and the conductive leads attached to the substrate. 
     FIG. 4 is a side elevational view in cross-section taken along line A—A in FIG. 3 illustrating the attachment of conductive leads to electrodes on the silicon substrate. 
     FIG. 5 is a perspective view of the headland area of the inkjet print cartridge of FIG.  1 . 
     FIG. 6 is a top plan view of the headland area of the inkjet print cartridge of FIG.  1 . 
     FIG. 7 is a side elevational view in cross-section taken along line C—C in FIG. 6 illustrating the configuration of the adhesive support surface, inner wall, gutter and of the headland design. 
     FIG. 8 is a top plan view of the headland area showing generally the location of the adhesive bead prior to placing the TAB head assembly on the headland area. 
     FIG. 9 is a partial schematic cross-sectional schematic view taken along line B—B of FIG. 1 showing portion of the print cartridge in the proximity to the TAB head assembly. 
     FIG. 10 is a cross-sectional, perspective view along line B—B of FIG. 1 with the TAB head assembly removed illustrating the internal structure of a inkjet print cartridge and the headland  50  area. 
     FIG. 11 is a partial cross-sectional view along line D—D of FIG. 1 illustrating the support of the substrate in the headland area. of the print cartridge. 
     FIG. 12 is a cross-sectional view taken along line E—E of FIG. 1 showing the adhesive encapsulating the substrate. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, reference numeral  10  generally indicates an inkjet print cartridge incorporating a printhead according to one embodiment of the present invention. The inkjet print cartridge  10  includes an internal ink reservoir (not shown) and a printhead  14 , where the printhead  14  is formed using Tape Automated Bonding (TAB). The printhead  14  (hereinafter “TAB head assembly  14 ”) includes a nozzle member  16  comprising two parallel columns of offset holes or orifices  17  formed in a flexible polymer flexible circuit  18  by, for example, laser ablation. The flexible circuit  18  provides for the routing of conductive traces  36  which are connected at one end to electrodes on a substrate (described below) and on the other end to contact pads  20 . The print cartridge  10  is designed to be installed in a printer so that the contact pads  20  on the front surface of the flexible circuit  18 , contact printer electrodes providing externally generated energization signals to the printhead. 
     FIG. 2 shows a front view of a TAB head assembly  14  removed from a print cartridge  10 . TAB head assembly  14  has affixed to the back of the flexible circuit  18  a silicon substrate  28  (not shown) containing a plurality of individually energizable thin film resistors. Each resistor is located generally behind a single orifice  17  and acts as an ohmic heater when selectively energized by one or more pulses applied sequentially or simultaneously to one or more of the contact pads  20 . Windows  22  and  24  extend through the flexible circuit  18  and are used to facilitate bonding of the other ends of the conductive traces  36  to electrodes on the silicon substrate. 
     The orifices  17  and conductive traces  36  may be of any size, number, and pattern, and the various figures are designed to simply and clearly show the features of the invention. The relative dimensions of the various features have been greatly adjusted for the sake of clarity. 
     FIG. 3 shows a highly simplified view of the back surface of a Tape Automated Bonding (TAB) printhead assembly  14  (hereinafter “TAB head assembly”). The back surface of the flexible circuit  18  includes conductive traces  36  formed thereon using a conventional photolithographic etching and/or plating process. The silicon die or substrate  28  is mounted to the back of the flexible circuit  18  with the nozzles or orifices  17  aligned with an ink vaporization chamber  32 . The conductive traces  36  are terminated by leads  37  that are bonded to electrodes  40  on the substrate  28  and by contact pads  20  designed to interconnect with a printer. Also shown is one edge of the barrier layer  30  containing vaporization chambers  32  formed on the substrate  28 . Shown along the edge of the barrier layer  30  are the entrances to the vaporization chambers  32  which receive ink from an internal ink reservoir within the print cartridge  10 . The windows  22  and  24  allow access to the leads of the conductive traces  36  and the substrate electrodes  40  (shown in FIG. 4) to facilitate bonding of the leads to the electrodes. 
     FIG. 4 shows a side view cross-section taken along line A—A in FIG. 3 illustrating the connection of the ends of the conductive traces  36  to the electrodes  40  formed on the substrate  28 . A portion  42  of the barrier layer  30  is used to insulate the leads  37  of the conductive traces  36  from the substrate  28 . Also shown is a side view of the flexible circuit  18 , the barrier layer  30 , the windows  22  and  24 , and the entrances of the ink vaporization chambers  32 . Droplets of ink  100  are shown being ejected from orifice holes associated with each of the ink vaporization chambers  32 . 
     FIG. 5 shows the headland area  50  of print cartridge  10  of FIG. 1 in a perspective view and with the TAB head assembly  14  removed to reveal the headland design used in providing a seal between the TAB head assembly  14  and the body of the print cartridge  10 . FIG. 6 shows the headland area  50  of FIG. 5 in a top plan view. FIG. 7 shows the headland area  50  in a cross-sectional view along sectional line C—C in FIG.  6 . 
     Shown in FIGS. 5,  6  and  7  are an inner raised wall  54 , an adhesive support surface  53  on the inner raised wall, openings  55  in the inner raised wall  54 , a surface  58 , a raised substrate support surface  58 A, a flat top surface  59  and a gutter  61 . Also shown are walls  62  which define the ink flow path  88  to the back of the substrate  28 . 
     FIG. 8 is top plan view showing generally the location of the dispensed adhesive  90  along the adhesive support surface  53  of inner raised wall  54 , on elevated substrate support surface  58 A and across surface  58  in the wall openings  55  of the inner raised wall  54 . 
     The adhesive circumscribes the substrate  28  when the TAB head assembly  14  is properly positioned and pressed down on the headland  50 . The adhesive  90  forms a structural attachment between the TAB head assembly  14  and the inner raised wall  54  and the support surface  58  of the print cartridge  10 . The adhesive also provides a liquid seal between the above-described circumscribed location and the back of the TAB head assembly  14  when TAB head assembly  14  is affixed to headland. 
     FIG. 9 is a partial cross-sectional schematic view taken along line B—B of FIG. 1 showing vaporization chambers  32 , thin film resistors  70 , and orifices  17  after the barrier layer  30  and substrate  28  are secured to the back of the flexible circuit  18  and the flexible circuit  18  is secured to the inner raised wall  54  of the print cartridge  10  by adhesive  90 . In operation, ink flows from reservoir  12  around the edge of the substrate  28 , and into vaporization chamber  32 , as shown by the arrow  88 . A barrier layer  30 , the flexible tape  18  and substrate  28  define the ink vaporization chambers  32 . Upon energization of the thin film resistor  70 , a thin layer of the adjacent ink is superheated, causing a droplet of ink  100  to be ejected through the orifice  17 . The vaporization chamber  32  is then refilled with ink by capillary action. Also shown is a portion of the adhesive seal  90 , applied to the inner raised wall  54  surrounding the substrate  28 . 
     The plastic print cartridge  10  body is formed such that an ink conduit directs the flow of ink  88  from an reservoir  12  within the print cartridge  10  towards the back of the substrate  88  and through a narrow gap that exists between the back surface of substrate  28  and the walls  62 . The ink  88  then flows along the back surface of substrate  28 , around the edge of substrate  28  and into the vaporization chamber  32 . The filter carrier  63  and the walls  62  direct the flow of ink  88 . The walls  62  of the ink conduit terminate approximately 0.127 mm (5 mils) from the back of the substrate  28 , thereby forming the narrow gap. An acceptable range for this gap is from about 3 mils to about 12 mils, depending on the ink viscosity and flow rates. The distance, in the preferred embodiment, between walls  62  is approximately 1 mm. The distance between walls  62  may be anywhere between about 1 mm and 5 mm. Other distances may also be suitable depending upon the size of substrate  88 , ink viscosity, and flow rates. The thickness of walls  62  is about 0.5 mm, but thinner or thicker walls will also work. 
     FIG. 10 is a cross-sectional, perspective view along line B—B of FIG. 1 with the flexible circuit  18  removed illustrating the internal structure of a inkjet print cartridge and the headland area  50 . Illustrated is an ink reservoir region  12  for containing ink, a filter carrier  63  with its filter screen  65  removed, walls  62 , the ink flow path  88  defined by the filter carrier  63  and walls  62  leading to the back surface of the substrate  28 . Also shown is a portion of the headland area  50  including inner raised wall  54 , adhesive support surface  53  on the inner raised wall, flat top surface  59  and gutter  61 . 
     Prior headland designs have not adequately addressed the problem of “ink shorts” occurring near the leads  37  of the flexible circuit  18  of TAB head assembly  14  due to ink penetrating the flex circuit  18  in the region of the leads  37 . These ink shorts cause malfunctioning of the printhead and shorten the life of the print cartridge. 
     FIG. 11 is a partial cross-sectional view along line D—D of FIG. 1 illustrating the support of the substrate in the headland area  50  of the print cartridge  10  by elevated substrate support surface  58 A before the addition of the adhesive  90 . By moving the substrate support surface  58 A further inboard, off the ends of the substrate  28 , the space  67  around the ends of the substrate  28  is open to be filled with the structural adhesive  90  that provides the ink seal. In this manner, the minimum adhesive thickness at the substrate  28  ends can be increased from essentially zero to a more optimal value of approximately between 5μ and 1 mm at the ends of the substrate  28 . 
     As the TAB head assembly  14  is pressed down onto the headland  50 , the adhesive is squished down. The adhesive squishes through the wall openings  55  in the inner raised wall to encapsulate the traces leading to electrodes on the substrate. The adhesive also squishes up through the windows  22 ,  24  and flush with the top surface of the windows. 
     From the adhesive surface  53  of the inner raised walls  54 , the adhesive overspills inwardly and outwardly into the gutter  61  between the inner raised walls  54  and the outer raised wall  60  which blocks further outward displacement of the adhesive. From the wall openings  55  in the inner raised wall, the adhesive squishes both inwardly and upwardly through windows  22 ,  24 . 
     This seal formed by the adhesive  90  circumscribing the substrate  28  allows ink to flow around the sides of the substrate  28  to the vaporization chambers  32  formed in the barrier layer  30 , but will prevent ink from seeping out from under the TAB head assembly  14 . Thus, this adhesive seal  90  provides a strong mechanical coupling of the TAB head assembly  14  to the print cartridge  10 , a fluidic seal and flexible circuit lead encapsulation. The displacement of the adhesive not only serves as an ink seal, but encapsulates the conductive traces in the vicinity of the windows  22 ,  24  from underneath to protect the conductive traces from ink. 
     FIG. 12 is a cross-sectional view taken along line E—E of FIG. 1 showing the adhesive  90  filling the region  67  between the bottom of the substrate  28  and the surface  58  after assembly. In designs which do not incorporate the present invention, the adhesive thickness under the ends of the substrate  28  is squeezed to a minimal thickness of as substrate  28  is pressed against the surface  58  during assembly. Therefore, this adhesive thickness in the substrate area provides minimal protection against ink penetration. As shown in FIG. 12, the adhesive thickness, b, between the bottom of the substrate  28  and the surface  58  may be varied by adjusting the height of elevated substrate support surface  58 A. Generally this adhesive thickness is approximately 5 to 400 microns. The length of the encapsulation of the substrate ends is determined by the dimension a in FIG.  12 . Generally this distance is approximately 0 to 150 microns. Also shown is the length, c, of the elevated substrate support surface  58 A. Generally, this distance is approximately 5 to 250 microns. 
     The advantages of the present invention have been demonstrated experimentally for two different print cartridge designs with and without the use of the present invention. Print cartridges of both designs were built with and without the use of the present invention. Accelerated storage testing at 60 degrees C for two weeks showed a significant decrease in ink penetration under the ends of the substrate  28  when the present invention was employed in either of the print cartridge designs. 
     Specifically, with the first print cartridge design, experimental results showed significant improvement in reducing ink penetration between substrate and structural adhesive. Results showed that approximately five percent of the print cartridges using the present invention exhibited ink penetration whereas, approximately sixty percent of the print cartridges not incorporating the present invention exhibited ink penetration. 
     Additionally, a second print cartridge design showed similar results when using the present invention. Experimental results from this second print cartridge design also showed significant improvement in reducing ink penetration between substrate and structural adhesive. Results showed that approximately five percent of the print cartridges using the present invention exhibited ink penetration whereas, approximately eighty-five percent of the print cartridges not incorporating the present invention exhibited ink penetration. Thus, ink penetration from print cartridges identical except for the present invention had much higher ink penetration. 
     The present invention provides increased encapsulation of the flexible circuit leads and traces that extend from the cover layer edge to the substrate edge. The design and process of the present invention uses a raised substrate support surface to provide increased encapsulation of the flexible leads by the adhesive used to secure the flexible circuit to the print cartridge body. By providing this increased encapsulation of the flexible circuit leads, corrosion and electrical shorting are greatly reduced in this region. Also, the process and design for flexible circuit lead encapsulation of the present invention produces far fewer air pockets because access to the flexible circuit leads is increased by use of a raised substrate support surface. 
     The present invention improves the robustness of the print cartridge against electrical shorts caused by ink penetrating the electrical leads of the shorting failure mode. 
     This provides tangible benefits both in increased manufacturing yields and long-life reliability for the end-user of the print cartridge. 
     An advantage of the invention that the invention can be implemented through only a change to the molded body of the print cartridge. Accordingly, unlike other potential solutions, no changes are required at the substrate or TAB head assembly level. Moreover, no manufacturing process changes are required. Finally, the present invention extends the life of the print cartridge. 
     The foregoing has described the principles, preferred embodiments and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments discussed. As an example, the above-described inventions can be used in conjunction with inkjet printers that are not of the thermal type, as well as inkjet printer that are of the thermal type Thus, the above-described embodiments should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those embodiments by workers skilled in the art without departing from the scope of the present invention as defined by the following claims.