KR101444560B1 - Inkjet printhead assembly having backside electrical connection - Google Patents

Abstract

Disclosed is an inkjet printhead assembly having an ink supply manifold and a connector film for supplying power to a printhead integrated circuit and a drive circuit of the printhead integrated circuit. Each printhead integrated circuit has a front with a drive circuit and inkjet nozzle assemblies, a backside attached to the ink supply manifold, and an ink supply channel that provides fluid communication between the backside and inkjet nozzle assemblies. The connecting end of the connector film is sandwiched between a portion of the ink supply manifold and the printhead integrated circuit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an inkjet printhead assembly having a backside electrical contact,

The present invention relates to printers, and more particularly to ink jet printers. The present invention has been developed primarily to provide improved mounting of a printhead integrated circuit to facilitate maintenance of the printhead.

Applicants have shown that pagewidth inkjet printheads can be constructed using a plurality of printhead integrated circuits ("chips ") with their ends abutting along the width of the page. Although the arrangement of the printhead integrated circuit thus has many advantages (e.g., minimizing the width of the print area in the paper feed direction), each printhead integrated circuit can be connected to another printer It must still be connected to the electronic components.

To date, Applicants have described how a printhead integrated circuit can be connected to an external power / data supply by wire bonding the bond pads on each printhead integrated circuit to a flex PCB (e.g., US7, 441, 865). However, the wire bonds protrude from the ink ejection side of the printhead, thereby adversely affecting both print maintenance and print quality.

It is desired to provide a printhead assembly in which the printhead integrated circuits are connected to an external power / data supply device without such a connection affecting the number of print holdings and / or print quality.

Thus, in a first aspect, there is provided an ink supply system comprising: an ink supply manifold; a front surface having a drive circuit and a plurality of inkjet nozzle assemblies; a back surface attached to the ink supply manifold; and a fluid between the back surface and the inkjet nozzle assemblies At least one printhead integrated circuit having at least one ink supply channel for providing communication; And at least one connector film for supplying power to the drive circuit, wherein a connecting end of the connector film is sandwiched between at least a portion of the ink supply manifold and the at least one printhead integrated circuit, Assembly is provided.

The inkjet printhead assemblies in accordance with the present invention provide a convenient means of attaching the printhead integrated circuit to the ink supply manifold while receiving electrical connection to the printhead. Also, the front surface of the printhead is completely flat along its entirety.

Optionally, the connector film has a flexible polymer film having a plurality of conductive tracks.

Optionally, the connector film is a tape self-bonding (TAB) film.

Optionally, the back side has a recess for receiving the connector film.

Optionally, a recess is formed along the longitudinal edge region of each printhead integrated circuit.

Optionally, the plurality of through-silicon connectors provide electrical connection between the drive circuit and the connection end of the connector film.

Optionally, each through-silicon connector extends straight from the front to the back.

Optionally, each through-silicon connector is tapered toward the back.

Optionally, each through-silicon connector is made of copper.

Optionally, each printhead integrated circuit comprises: a silicon substrate; at least one CMOS layer having a driver circuit; And a MEMS layer having inkjet nozzle assemblies, wherein a CMOS layer is positioned between the silicon substrate and the MEMS layer.

Optionally, each through-silicon connector extends straight from the contact pad of the MEMS layer through the CMOS layer and toward the backside, and the contact pad is electrically connected to the CMOS layer.

Optionally, the printhead assembly has at least one conductor post extending linearly between the contact pad and the CMOS layer.

Optionally, each through-silicon connector is electrically isolated from the CMOS layer.

Optionally, each through-silicon connector has outer sidewalls with an insulating film.

Optionally, the outer sidewalls have a diffusion barrier layer between the insulating film and the conductive core of the through-silicon connector.

Optionally, each through-silicon connector is soldered to the connection end of the film.

Optionally, the film is bonded to the ink supply manifold along with the plurality of printhead integrated circuits.

Optionally, the plurality of printhead integrated circuits are positioned in an end-on-end butting arrangement to provide a pagewidth printhead assembly.

Optionally, the front face of the printhead is flat and free from any wire bonding connection.

Optionally, the front surface is coated with a hydrophobic polymer layer.

In a second aspect, there is provided a printer comprising: a front having a drive circuit and a plurality of inkjet nozzle assemblies; a back surface attached to the ink supply manifold; And at least one ink supply channel for providing fluid communication between the backside and the inkjet nozzle assemblies, the backside having a recess for receiving at least a portion of a connector film for supplying power to the drive circuit, Circuit is provided.

Optionally, the connecting end of the connector film is sandwiched between at least a portion of the ink supply manifold and the printhead integrated circuit when the backside is attached to the ink supply manifold.

Optionally, the recesses are formed along the longitudinal edge region of the printhead integrated circuit.

Optionally, the recesses comprise a plurality of integrated circuit contacts, each integrated circuit being connected to a drive circuit.

Optionally, the connector film is a tape self-bonding (TAB) film, wherein the integrated circuit contact is positioned to connect to a corresponding contact of the TAB film.

Optionally, the plurality of through-silicon connectors extend straight from the front side to the back side, and each through-silicon connector provides electrical connection between the driver circuit and the corresponding integrated circuit contact.

Optionally, each integrated circuit contact is defined by an end of each through-silicon connector.

Optionally, the backside has a plurality of ink supply channels extending longitudinally along the printhead integrated circuit, each ink supply channel defining one or more ink inlets for receiving ink from the ink supply manifold. Optionally, each ink supply channel supplies ink to the plurality of front entrances. Optionally, each frontal inlet supplies ink to one or more inkjet nozzle assemblies.

Optionally, each ink supply channel has a depth corresponding to the depth of the recess.

In a third aspect, there is provided an inkjet printer comprising: a silicon substrate defining a front surface and a back surface; a plurality of inkjet nozzle assemblies positioned on the front surface; a driving circuit for supplying power to the inkjet nozzle assembly; And at least one through-silicon connector extending from the front side toward the backside and providing electrical connection between the driver circuit and the at least one corresponding integrated circuit contact, the integrated circuit contact comprising a back-mounted A printhead integrated circuit is provided which is positioned to be connected to a connector film.

Optionally, each integrated circuit contact is defined by an end of each through-silicon connector.

In a fourth aspect, there is provided a method comprising providing at least one printhead integrated circuit, wherein each printhead integrated circuit includes a front face having a drive circuit, a plurality of inkjet nozzle assemblies, one or more ink inlets and a back face having a concave edge portion, Providing at least one printhead integrated circuit having at least one connector extending through the circuit, each connector having a head connected to the base and a drive circuit at a concave edge; Positioning a connecting end of the connector film at a concave edge of the connector film, the connector film having a plurality of conductive tracks, each conductive track having a respective film contact at a connecting end, Connecting each film contact to a base of a corresponding connector; And attaching a backside of each printhead integrated circuit with the connector film to the ink supply manifold to provide an inkjet printhead assembly having a backside electrical contact, A method for manufacturing the same is provided.

Optionally, the adhering step sandwiches the connecting end of the connector film between a portion of the ink supply manifold and one or more printhead integrated circuits.

Optionally, the film is a tape self-adhesive (TAB) film.

Optionally, said connecting comprises soldering each film contact to a base portion of its corresponding connector.

Optionally, the adhering step is carried out using an adhesive film.

Optionally, the adhesive film has a plurality of ink supply openings defined therein,

Optionally, the adhering step includes aligning each printhead integrated circuit with an adhesive film such that each ink feed opening is aligned with the ink inlet, bonding the printhead integrated circuit to one side of the adhesive film, To the ink supply manifold.

Optionally, in the connecting step, each printhead integrated circuit is connected to a respective connector film.

Optionally, in the connecting step, the plurality of printhead integrated circuits are connected to the same connector film.

Optionally, a plurality of printhead integrated circuits are attached to the ink supply manifold in end-to-end arrangements to provide a pagewidth printhead assembly.

Providing a wafer having a plurality of partially manufactured nozzle assemblies on the front side of the wafer and one or more through-silicon connectors extending from the front toward the back side of the wafer; Laminating and etching a conductive layer on the front side of the wafer to form a front contact pad and an actuator for each nozzle assembly on the front contact pad, the front contact pad connecting the through-silicon connector to a drive circuit of the wafer, And further performing MEMS process steps to complete the formation of nozzle assemblies and ink supply channels and through-silicon connectors for the nozzle assemblies; And dividing the wafer into a plurality of separate printhead integrated circuits wherein each printhead integrated circuit is configured to be backplane-connected to the drive circuit through the through-silicon connector and the contact pad, A method of manufacturing a printhead integrated circuit for connection is provided.

Optionally, the conductive material is selected from the group consisting of titanium nitride, titanium aluminum nitride, titanium, aluminum, and a vanadium-aluminum alloy.

Optionally, the actuator is selected from the group consisting of a thermal bubble-forming actuator and a thermal bending actuator.

Optionally, the additional MEMS fabrication process steps include etching the backside of the wafer to form recesses and ink supply channels for the backside for each printhead integrated circuit.

Optionally, the ink supply channels and recesses in the back surface have the same depth.

Optionally, the backside etch exposes a bottom portion of each through-silicon connector at a recess in the backside, each bottom portion having an integrated circuit contact.

Optionally, the through-silicon connectors are located along the longitudinal edge region of each printhead integrated circuit, and the back recess extends along the longitudinal edge region.

Optionally, the integrated circuit contacts are positioned to connect to corresponding contacts of the TAB film.

Optionally, the CMOS layer has a drive circuit, and the nozzle assemblies are disposed in a MEMS layer formed in a CMOS layer.

Optionally, at least one conductor post extends straight between the contact pad and the CMOS layer and / or between the actuator and the CMOS layer.

Optionally, the conductor posts are formed prior to laminating the conductive layer.

Optionally, the conductor posts are formed with through-silicon connectors.

Optionally, the conductor posts and through-silicon connectors are formed by laminating conductive material in predefined vias.

Optionally, the conductive material is deposited by an electroless plating process.

Optionally, each of the predefined vias has a diameter corresponding to the depth such that all the vias are evenly filled by the stack.

Optionally, the conductive material is copper.

Optionally, additional MEMS manufacturing process steps include coating the front side with a hydrophobic polymer layer.

Optionally, the hydrophobic polymer layer is made of PDM.

Optionally, the additional MEMS manufacturing process steps include a sacrificial material that is oxidized and removed.

The inkjet printhead assemblies in accordance with the present invention provide a convenient means of attaching the printhead integrated circuit to the ink supply manifold while receiving electrical connection to the printhead. Also, the front surface of the printhead is completely flat along its entirety.

Embodiments of the present invention will be described in detail with reference to the following drawings.
1 is a front perspective view of a printhead integrated circuit;
2 is a front perspective view of a pair of adjacent printhead integrated circuits.
3 is a rear perspective view of the printhead integration well shown in Fig.
4 is a cutaway perspective view of an inkjet nozzle assembly having a floor nozzle inlet.
5 is a cutaway perspective view of an inkjet nozzle assembly having a side wall nozzle inlet.
6 is a side perspective view of the printhead assembly.
Figure 7 is a bottom perspective view of the printhead assembly shown in Figure 6;
8 is an upper exploded perspective view of the printhead assembly shown in FIG.
9 is a bottom exploded bottom view of the printhead assembly shown in FIG.
10 is an overlaid top view of a printhead integrated circuit attached to an ink supply manifold.
11 is an enlarged view of Fig.
12 is a perspective view of an inkjet printer.
Figure 13 is a schematic cross-sectional view of the printhead assembly shown in Figure 6;
Figure 14 is a schematic cross-sectional view of a printhead assembly in accordance with the present invention.
15 is a schematic cross-sectional view of another printhead assembly in accordance with the present invention.
16 to 24 are schematic cross-sectional views of a wafer after various steps of manufacturing a printhead integrated circuit according to the present invention.
25 is a schematic cross-sectional view of a printhead integrated circuit according to the present invention.

To date, Applicants have described printhead integrated circuits (or "chips ") 100 that can be linked together in an end-to-end fashion to define a pagewidth printhead. Figure 1 is a front perspective view of a printhead IC 100, and Figure 2 shows a pair of printhead ICs in contact with each other.

Each printhead IC 100 has thousands of nozzles 102 arranged in rows. As shown in FIGS. 1 and 2, the printhead IC 100 is adapted to receive and print five different ink colors (e.g., CMYK and IR (infrared); CCMMY; or CMYKK). Each color channel 104 of the printhead IC 100 has a pair of nozzle rows in which one of the rows of nozzles prints the even dots and the other row of the pair of nozzle rows is an odd number Print dots. The nozzles from each color channel 104 are aligned vertically in the paper feed direction to perform dot-on-dot printing at high resolution (e.g., 1600 dpi). The horizontal distance ("pitch") between two adjacent nozzles 102 in a row is about 32 microns and the vertical distance between the rows of nozzles is based on the firing order of the nozzles. However, the rows are typically spaced apart by the exact number of dot lines (e.g., 10 dot lines). A more detailed description of the thermal arrangement of the nozzles and the ejection of the nozzles is described in USP 7,438,371, the contents of which are incorporated herein by reference.

The length of the individual printhead ICs 100 is typically about 20 to 22 mm. Thus, to print an A4 / US letter size page, 11 or 12 individual printhead ICs 100 are linked adjacent to each other. The number of individual printhead ICs 100 may be varied to accommodate different widths of paper. For example, a 4 inch photo printer typically employs five printhead ICs linked together.

The printhead IC 100 may be linked to each other in a variety of ways. One particular method of linking ICs 100 is shown in FIG. In this arrangement, the ICs 100 are shaped so that their neighboring ICs are linked to each other with no offset in the vertical direction to form the horizontal lines of the ICs. An oblique bond 106 having a generally 45 [deg.] Angle is provided between the printhead ICs. The edges of the joints have a serrated profile to facilitate alignment of the adjacent printhead ICs.

As can be seen from Figs. 1 and 2, the leftmost ink supply nozzle 102 of each row is arranged in a triangular shape 107 falling down by 10 line pitches. This arrangement maintains the pitch of the nozzles across the junction 106 to ensure that ink droplets are fed consistently along the print area. This arrangement also ensures that more silicon is provided at the edge of each printhead IC 100 to ensure sufficient linkage between the contacting ICs. Nozzles contained in each row that are dropped below should be ejected at different times to ensure that the nozzles in the corresponding column are ejected on the same line of the page. Although the control of the operation of the nozzles is performed by a printhead controller ("SoPEC") device, compensation for the rows falling below the nozzles may be performed by the CMOS circuit of the printhead or shared between the printhead and the SoPEC device . A full description of the dislodged nozzle arrangement and its control method is contained in USP 7,275,805, which is incorporated herein by reference.

Referring to Figure 3, the opposite back side of the printhead integrated circuit 100 is shown. Ink supply channels 110 are formed on the back surface of the print head IC 100 and extend long along the length direction of the print head IC. This longitudinal ink supply channel 100 meets the nozzle inlet 112 and the nozzle inlet is in fluid communication with the front nozzles 102. 4 shows a portion of the printhead IC in which the nozzle inlet 112 supplies ink directly to the nozzle chamber. 5 shows a portion of another printhead IC that supplies ink to an ink supply tube 114 in which the nozzle inlet 112 extends lengthwise along each row of nozzle chambers. In this alternative arrangement, the nozzle chambers are provided with ink from the adjacent ink supply tube region of the present invention through the inlet of the side wall.

Referring again to Figure 3, the longitudinally extending ink supply channel 110 is divided into portions by a silicon bridge or wall 116. These walls 116 provide the printhead IC 100 with additional mechanical strength in the transverse direction relative to the longitudinal channel 110.

The ink is supplied to the back side of each printhead IC 100 through the ink supply manifolds in the form of a two-part LCP molding. Referring to Figs. 6-9, a printhead assembly 130 having a printhead IC 100 is shown attached to an ink supply manifold via an adhesive film 120. As shown in Fig.

The ink supply manifold has a main LCP molding 122 and an LCP channel molding 124 sealed down there. The printhead IC 100 is bonded to the underside of the channel molding 124 using the adhesive IC attachment film 120. Above the LCP channel molding 124 is an LCP main channel 126 which is connected to the ink inlet 127 and the ink outlet 128 of the main LCP molding 122. The ink inlet 127 and the ink outlet 128 are in fluid communication with the ink reservoir and the ink supply system (not shown), which supplies ink to the printhead at a predetermined fluid pressure.

The main LCP molding 122 has a plurality of air cavities 129 which communicate with the LCP main channel 126 formed in the LCP channel molding 124. Air cavities 129 serve to attenuate ink pressure pulses in the ink supply system.

At the base of each LCP main channel 126 is a series of ink feed passages 132 that are directed to the print head IC 100. The adhesive film 120 has a series of laser drilled feed openings 134 so that the back side of each printhead IC 100 is in fluid communication with the ink feed passageways 132.

Referring to Fig. 10, the ink supply passage 132 is arranged in a series of five rows. The middle row of the ink supply passages 132 supplies ink directly to the backside of the printhead IC 100 through laser drilled holes 134 and the outer rows of the ink supply passages 132 communicate with the micromolded channel & (Not shown) to supply ink to the printhead IC through a plurality of nozzles 135, each micomolded channel ending at one of the laser drilled holes 134.

Figure 11 shows in more detail how the ink is supplied to the ink supply channel 110 on the back side of the printhead IC 100. [ Each laser drilled hole 134 is formed in the adhesive film 120 and aligned with the corresponding ink supply channel 110. Generally, the laser drilled holes 134 are aligned with one of the transverse walls 116 of the channel 110 so that ink is supplied to both channel portions of the wall 116. This arrangement reduces the number of fluid connections required between the ink supply manifold and the printhead ICs 100.

Reference portions 103A are provided on the surfaces of ICs 100 to assist in correct alignment of ICs 100 (see FIGS. 1 and 11). The reference portions 103A are in the form of markers that can be easily identified by appropriate alignment equipment to indicate the correct position of the IC 100 relative to the neighboring IC. The adhesive film 120 has a complementarity reference portion 103B that helps align each printhead IC 100 relative to the adhesive film while adhering the printhead ICs 100 to the ink supply manifold . The reference portions 103A and 103B are strategically located at the edges of the IC 100 along the length of the adhesive IC-adhering film 120. [

Print head  Data and power supply to integrated circuits

Referring to Figure 1, a printhead IC 100 has a plurality of bond pads 105 extending along one of its longitudinal edges. The bond pad 105 provides a means for receiving data and / or power from a printhead controller ("SoPEC") device that controls the operation of the inkjet nozzle 102.

The bond pads 105 are connected to the upper CMOS layer of the printhead IC 100. As shown in FIGS. 4 and 5, each MEMS nozzle assembly is formed in a CMOS layer 113, which includes the necessary logic and driver circuitry to fire each nozzle.

6 through 9, the flex PCB 140 is wire-bonded to the bond pads 105 of the printhead IC 100. As shown in FIG. The wire bonding is sealed and protected by the wire bond sealant 142 (see FIG. 7), and the sealant is typically a polymer resin. The LCP molding 122 has a curved support wing portion 123 around which the flex PCB 140 is bent and fastened. The support wing portion 123 has a plurality of openings 125 for receiving the various electrical components 144 of the flex PCB. In this manner, the flex PCB 140 can be bent around the outer surface of the printhead assembly 130. A paper guide 148 is mounted opposite the LCP molding 122 with respect to the flex PCB 140 to complete the printhead assembly 130.

The printhead assembly 130 is designed as part of a user replaceable printhead cartridge, and the cartridge can be removed from the inkjet printer 160 and replaced (see FIG. 12). Thus, the flex PCB 140 has a plurality of contacts 146 that allow power and data connections to electronic equipment (including SoPEC devices) of the printer body.

Since the flex PCB 140 is wire bonded to the bond pads 105 of each print head IC 100, the print head necessarily has a non-planar longitudinal edge region near the bond pads. This is most clearly illustrated in FIG. 13, which shows wirebonds 150 extending from bond pads 105 of a printhead IC 100 having a plurality of inkjet nozzle assemblies 101. 13, the bond pads 105 are formed in the MEMS layer and are connected to the CMOS layer 113 of the base layer via the connector pillar portion 152. [ Alternatively, the bond pad 105 may be the exposed upper layer of the CMOS 113 without any connection to the MEMS layer. In both configurations, the wire bonds extend from the inkjet exit surface 154 of the printhead and are connected to the flex PCB 140.

Wire bonding to the bond pads 105 of the printhead IC 100 has several disadvantages, primarily in that the significant longitudinal regions of the printhead IC protrude from the ink ejection surfaces 154 Wire-bond-sealing material 142). The non-planar nature of the ink ejection surface 154 results in less maintenance of the printhead. For example, the wiper blade can not sweep across the entire width of the inkjet exit surface 154 because the wire-bond seal 142 is positioned upstream or downstream of the nozzles 102 relative to the wiping direction Because it blocks the path of the wiper blade.

Another disadvantage of wire bond protrusion is that the entire printhead can not be coated with a hydrophobic coating such as PDMS. Applicants have found that PDMS coatings significantly improve both print quality and printhead maintenance (see, for example, U.S. Patent Application Publication No. US 2008/022567, the contents of which are incorporated herein by reference), a completely planar ink ejection surface And will further improve the efficacy of such coatings.

Backside electricity Connections  Configured for Print head  Integrated circuit

Considering some of the inherent disadvantages of making a wire bonding connection to the printhead IC 100, Applicant has developed a printhead IC 2, which uses an electrical connection on the backside, And has an injection surface.

Referring to Fig. 14, the printhead IC 2 is mounted to the LCP channel molding 124 of the ink supply manifold using an adhesive film 120. The printhead IC 2 has at least one longitudinal ink supply channel 110 which communicates between the ink supply manifold 101 and the nozzle assemblies 101 via the nozzle inlet 112 and the ink supply tube 114, Provide communication. Thus, the printhead assembly 160 (including the printhead IC 2) has a fluid engineering arrangement such as the printhead assembly 130 (including the printhead IC 100) described in connection with FIGS. 1-11.

However, the electrical connection portion formed in the CMOS circuit layer 113 of the printhead IC 2 is different from the printhead IC 100. [ It should be noted that the printhead IC 2 has no front wire bonding along its longitudinal edge region 4. Rather, the printhead IC 2 has a recess 6 in the back surface at its longitudinal edge, which receives a tape-automated bonding (TAB) film 8. The TAB film 8 is a flexible polymer film (e.g., a Mylar ( ^R ) film) that typically has a plurality of conductive tracks terminating at corresponding film contacts 10 at the ends of the connection ends of the TAB film. The TAB film 8 is positioned so as to be at the same height as the backside 12 of the printhead IC 2 so that the TAB film and the printhead IC 2 can be bonded to the LCP channel molding 124 with each other. The TAB film 8 may be connected to the flex PCB 140. Indeed, the TAB film can be integrated with the flex PCB 140. Alternatively, the TAB film 8 may be connected to the printer's electronics using other connection arrangements known to those skilled in the art.

The printhead IC 2 has a plurality of through-silicon vias extending from its front face to the longitudinally extending concave edge portions 6 for receiving the TAB film 8. Each through-silicon via is filled with a conductor (e.g., copper) to form a through-silicon connector 14, which provides an electrical connection to the TAB film 8. Each film contacting portion 10 is connected to the bottom portion or base 15 of the through-silicon connector 14 using suitable connections, such as, for example, solder balls 16.

The through-silicon connector 14 extends through the silicon substrate 20 of the printhead IC 2 and through the CMOS circuitry layer 113. The through-silicon connector 14 is insulated from the silicon substrate 20 by insulating side walls 21. Insulated sidewalls 21 may be formed of any suitable insulating material suitable for MEMS fabrication, such as amorphous silicon, polysilicon, or silicon dioxide. The insulating side walls 21 may be single-layered or multi-layered. For example, the insulating sidewalls 21 may comprise an outer Si or SiO ₂ layer and an inner tantalum layer. The inner Ta layer acts as a diffusion barrier to minimize diffusion of copper into the bulk silicon substrate. The Ta layer may act as a seed layer for the electrodeposition of copper during the fabrication of the through-silicon connector 14.

14, the head 22 of the through-silicon connector 14 meets the contact pads 24 formed in the MEMS layer 26 of the printhead IC 12. The MEMS layer 26 is laminated to the CMOS circuitry layer 113 of the printhead IC 2 and has all the inkjet nozzle assemblies 101 formed by the MEMS manufacturing process steps.

In the case of the applicant's bend-actuated printhead as described in US 2008/0129793, the contents of which are incorporated herein by reference, a conductive thermoelastic actuator 25 is provided in each nozzle chamber A roof of the base 101 can be formed. Accordingly, the contact pad 24 may be formed simultaneously with the thermoelastic actuator 25 during the MEMS manufacturing process, and may also be formed of the same material. For example, the contact pad 24 may be formed of a thermally elastic material such as a vanadium-aluminum alloy, titanium nitride, titanium aluminum nitride, or the like.

It will be appreciated, however, that the formation of the contact pads 24 can be incorporated at any stage in the MEMS fabrication process and can also be made of any suitable conductive material, such as copper, titanium, aluminum, titanium nitride, titanium aluminum nitride, and the like.

The contact pad 24 is connected to the upper layer of the CMOS circuit 113 through the copper conductor column portion 30 extending from the contact pad toward the CMOS circuit. Therefore, the conductor pillar portion 30 providing the electrical connection is provided between the TAB film 8 and the CMOS circuit 113. [

The arrangement of the contact pads 24 and the connector posts 30 of FIG. 14 is similar to that of the thermal bending-actuated inkjet nozzles (described in US patent application US 12 / 323,471, the contents of which are incorporated herein by reference) The present invention also includes other arrangements that provide a similar backplane electrical connection from the TAB film 8 to the CMOS circuitry 113 on the backside.

With reference to FIG. 15, for example, the through-silicon connector 14 may terminate in the protection layer 27 on the CMOS circuit 113. The buried contact pad 23 may be formed by laminating a suitable conductive material over the top CMOS layer exposed through the head 22 of the through-silicon connector and through the passivation layer 27 to form the through- . Through the subsequent deposition of photoresist 31 and ceiling layer 37 (e.g., silicon nitride, silicon oxide, etc.) during the MEMS nozzle manufacturing process, a completely flat nozzle plate and ink ejection surface are provided for the printhead. In addition, the buried contact pad 23 is completely sealed and encapsulated with the photoresist 31 under the ceiling layer 37. This other contact pad arrangement is well known in the applicant's MEMS fabrication process for forming a thermal bubble-forming inkjet nozzle assembly as described, for example, in U.S. Patent Nos. 6,755,509 and 7,303,930, the contents of which are incorporated herein by reference . The nozzle assembly shown in FIG. 15 is a thermal bubble-forming inkjet nozzle assembly having a hydrostatic heating element 28 and a nozzle opening 102 as described in USP 6,755,509. It will be readily appreciated by those skilled in the art that the material of the heating element may be laminated and subsequently etched so that the buried contact pad 23 and the hydrothermal heating element 28 may be formed together during the MEMS fabrication process. Thus, the buried contact pad 23 can be made of a material such as a heating member 36, such as titanium nitride, titanium aluminum nitride, and the like.

Referring again to FIG. 14, it should be noted that the ink ejection surface of the printhead IC 2 is completely flat and coated with a layer of hydrophobic PDMS 48. PDMS coatings and their advantages are described in detail in U. S. Patent Application Publication No. US 2008/0225082, the contents of which are incorporated herein by reference. As previously described, the planarity of the ink ejection surface, including portions of the surface in the longitudinal edge region 4 of the printhead integrated circuit 2, has significant advantages in printhead maintenance and face flooding control .

14 and 15, the contact pads 24 of the printhead ICs 2 are formed by a corresponding number of through-silicones (not shown) extending into the silicon substrate 20, although the contact pads are schematically illustrated adjacent the nozzles 102. [ Typically occupies a similar position to the bond pads 105 of the printhead IC 100 (FIG. 1) with the connector 14. Nevertheless, an advantage of the present invention is that the contact pad 24 need not be spatially separated from the inkjet nozzle 102 in the same manner as is required for the bond pad 105, Requires sufficient ambient space for wire-bond encapsulation. Thus, the backside TAB film connection enables more effective use of silicon and potentially reduces the overall width of each IC, or allows a large number of nozzles 102 to be formed across the same width of the IC. For example, in the case of the printhead IC 100, about 60-70% of the IC width is assigned to the ink nozzles 102, whereas the present invention allows more than 80% of the IC width to be assigned to the ink nozzles. This is an important advantage considering that silicon is one of the most expensive components in pagewidth inkjet printers.

Configured for backside electrical connection Print head IC of MEMS  Manufacture process

The MEMS manufacturing process for the printhead IC 2 shown in Fig. 14 will be described in detail. This MEMS manufacturing process includes several variations of the process described in US patent application US 12 / 323,471 for incorporating the features required for backside connection to the TAM film 8. Although the MEMS process is described in detail herein for purposes of illustration, it will be apparent to those skilled in the art that similar variations of any inkjet nozzle manufacturing process will provide a printhead integrated circuit configured for backside electrical connection. Actually, the Applicant has referred to a suitable MEMS manufacturing process for manufacturing the thermally actuated printhead IC shown in FIG. Accordingly, the present invention is not intended to be limited to the particular nozzle assembly 101 described below.

Figs. 16 to 25 illustrate MEMS fabrication steps for forming the printhead IC 2 described in connection with Fig. The completed printhead IC 2 has features that enable backplane connection to the CMOS circuitry 113 as well as the plurality of nozzle assemblies 101.

The starting point of the MEMS manufacturing process is a standard CMOS wafer having a silicon substrate 20 and a CMOS circuit 113 formed on the front side of the wafer. At the end of the MEMS manufacturing process, the wafer is diced through separate etched dicing streets into separate printhead integrated circuits (ICs), which define the size of each printhead IC fabricated from the wafer.

Although the present description refers to a MEMS fabrication process performed on a CMOS layer 113, the CMOS layer 113 may have multiple CMOS layers (e.g., three or four CMOS layers) It will of course be understood that it is processed. The CMOS layer 113 may be shielded with a standard ONO stack having, for example, a silicon oxide layer or, more typically, a silicon nitride layer sandwiched between two silicon oxide layers. Thus, in this specification, the CMOS layer 113 implicitly implies a shielded CMOS layer, which typically has a plurality of CMOS layers.

The description below focuses on the manufacturing process steps for one nozzle assembly 101 and one through-silicon connector 14. However, it will also be appreciated that corresponding steps will be performed simultaneously for all nozzle assemblies and all through-silicon connectors.

In the first of the steps shown in FIG. 16, the front entrance hole 32 is etched through the CMOS layer 113 and into the silicon substrate 20 of the CMOS wafer. At the same time, the front dicing hole 33 is etched through the CMOS layer 113 and into the silicon substrate. A photoresist 31 is applied to the front side of the wafer to plug the front entrance hole 32 and the front dicing street hole 33. The wafer is then polished by chemical mechanical polishing (CMP) to provide the wafer shown in FIG. 16, which has a flat front ready to proceed with subsequent MEMS steps.

Referring to FIG. 17, in the next step, an 8 micron layer of low stress silicon oxide is deposited on the CMOS layer 113 by plasma enhanced chemical vapor deposition (PECVD). The depth of the silicon oxide layer 35 defines the depth of each nozzle chamber of the inkjet nozzle assembly. After the SiO ₂ layer 35 is laminated, a wall 36 for the nozzle chambers and a portion of the front dicing hole 32 are formed by subsequent etching of the SiO ₂ layer. A silicon etching chemical reaction is employed to extend the front dicing hole 32 and to etch the ink inlet hole 32 into the silicon substrate 20. [ The resulting holes 32 and 33 are then plugged into the photoresist 31 by spin coating the photoresist and planarizing the wafer using CMP polishing. The photoresist 31 is a sacrificial material serving as a footing for the subsequent lamination of the ceiling material. It will be readily understood that other suitable sacrificial materials (e.g., polyimide) may be used for this purpose.

A ceiling material (e.g., silicon oxide, silicon nitride, or a combination thereof) is deposited over the planarized SiO ₂ layer 35 to form the front ceiling layer 37. The ceiling layer 37 will form a rigid flat nozzle plate in the completed printhead IC 2. [ Figure 17 shows the wafer at the end of this process of the MEMS manufacturing process steps.

18, a plurality of conductor punch vias 38 are etched through the ceiling layer 37 and the SiO ₂ layer 35 to the CMOS layer 113. In the next step, The conductor pillar vias 38A etched through the walls 36 will cause the nozzle actuators to be connected to the CMOS 3 of the underlying layer. Conductor post vias 38B, on the other hand, will allow electrical connection between the contact pad 24 and the CMOS layer 113 of the underlying layer.

Silicon vias 39 may be formed on the top surface of the via layer 37, the SiO ₂ layer 35, the CMOS (not shown), or the like, before filling the via 38 with a conductive material and in a variation of the process described in US patent application US 12 / 323,471. Is formed in the next step by etching through the layer 113 to the silicon substrate 20 (see FIG. 19). The through-silicon vias 39 are positioned so as to be spaced apart along the longitudinal edge region of each completed printhead IC 2. (The front dicing hole 33 effectively forms the longitudinal edges of each printhead IC 2.) Each via 39 is generally tapered toward the backside of the silicon substrate 20. [ The precise positioning of the vias 39 is determined by the positioning of the film contacts 10 of the TAB film 8 which meet the base of each via when the printhead IC is assembled and connected to the TAB film.

Through-silicon via etching is performed by patterning the mask layer of the photoresist 40 and etching the various layers. Of course, the same photoresist mask may be employed for each etch, but other etch chemistries may be required to etch each of the various layers.

Each through-silicon via 39 typically has a depth into the silicon substrate 200 corresponding to the depth of the plugged front ink inlet 32 (typically 20 microns). However, each via 39 may be formed deeper than the front ink inlet 32 depending on the thickness of the TAB film 8.

In the next step, referring to FIGS. 20 and 21, the trough-silicon vias 39 have insulating walls 21, which insulate the vias from the silicon substrate 20. The insulating wall 21 has an insulating film 42 and a diffusion preventing layer 43. The diffusion barrier layer 43 minimizes the diffusion of copper into the bulk silicon substrate 20 when each via 39 is filled with copper. The insulating layer 42 and the diffusion barrier layer 43 are formed by successive deposition steps, optionally using a mask layer 40 for selective deposition of each layer to the via 39.

The insulating film 42 may be made of any suitable insulating material such as amorphous silicon, polysilicon, silicon oxide, or the like. The diffusion barrier layer 43 is typically a tantalum film.

Referring next to Fig. 22, conductor pillar vias 38 and through-silicon vias 39 are simultaneously filled with a highly conductive material, such as copper, using electroless plating. The copper laminating step concurrently forms the nozzle conductor pillar portion 44, the contact pad conductor pillar portion 30 and the through-silicon connector 14. Proper sizing of the vias 38 and 39 diameters may be required to ensure simultaneous copper plating during this step. After the copper plating step, the deposited copper undergoes a CMP process, where the CMP process stops at the ceiling layer 37 to provide a planar structure. The conductor posts 30 and 44 are formed during the electroless copper plating step and meet the CMOS layer 113 to provide a straight conductor path from the CMOS layer to the ceiling layer 37.

23, a thermally elastomeric material is laminated and etched into the ceiling layer 37 to form the contact pads 24 on the head of the through-silicon connector 14 as well as for the respective nozzle assembly 101 A thermoelastic beam member 25 is formed.

Parts of the help fused to the open elastic beam member (25), SiO ₂ ceiling layer 37 can function as the lower inert (passive), the beam member 46 of the mechanical thermal bend actuator (thermal bend actuator). Each nozzle assembly 101 thus has a thermal bending actuator having an upper thermally elastic beam 25 and a lower inactive beam 46 connected to the CMOS 113. These types of thermally actuated bending actuators are described in more detail in, for example, U.S. Patent Application Publication No. US 2008/309729, the contents of which are incorporated herein by reference.

The thermally elastic active beam member 25 may be made of any suitable thermoelastic material, such as titanium nitride, titanium aluminum nitride, and aluminum alloy. Vanadium-aluminum alloys are preferred materials as they are described in Applicant's U.S. Patent Application Publication No. US 2008/129793, the contents of which are incorporated herein by reference, because they exhibit high thermal expansion, low density and high Young's modulus ( Young's modulus).

As described above, a thermally elastic material is also used to form the contact pad 24. The contact pad 24 extends between the head of the connector post 30 and the head 22 of the through-silicon connector 14. Thus, the contact pad 24 electrically connects the through-silicon connector 14 to each conductor post 30 and the CMOS layer 113 of the ground layer.

23, after the thermally-elastic material is laminated and etched to form the thermal bending actuator and contact pads 24, the final front MEMS fabrication process step includes etching of the nozzle openings 102 and etching of the front-side street openings 47 ) And a step of laminating the PDMS coating 48 over the entire ceiling layer 37 so as to render the front surface hydrophobic and provide an elastic mechanical seal of each thermal bending actuator. The use of PDMS coatings has been extensively described in the applicant's US patent applications US 11 / 685,084 and US 11 / 740,925, the contents of which are incorporated herein by reference.

24, the entire front side of the wafer is coated with a relatively thick layer of photoresist 49, which protects the front MEMS structure and allows the wafer to be removed from the handle wafer 50 for MEMS processing on the backside, . The backside etch forms a recess 6 in which the ink supply channel 110 and the bottom portion 15 of the through-silicon connector 14 extend. The portion of the insulating film 42 is removed when the bottom portion 15 of the through-silicon connector 14 is exposed by back-etching. The backside etch also allows singulation of the individual printhead ICs by etching up to the plugged front dicing street holes 33.

The final oxidative removal ("ashing") of the protective layer photoresist 49 forms a fluid connection between the singulation of the individual printhead ICs 2 and the backside and nozzle assembly 101. The resultant printhead IC 2 shown in Fig. 25 is ready for the through-silicon connector 14 to be connected to the TAB film 8 via the solder joint 16. The step of subsequently bonding the resulting printhead IC / TAB film assembly to the ink supply manifold provides the printhead assembly 60 shown in FIG.

The present invention has been described with reference to preferred embodiments and several other specific embodiments. However, it will be understood by those skilled in the art that the specific embodiments described herein and other embodiments are within the scope and spirit of the invention. It will therefore be appreciated that the present invention is not limited to documents properly merged as references and to the specific embodiments described herein. The scope of the invention is limited only by the appended claims.

2, 100: printhead IC 8: TAB film
14: through-silicon connector 24: contact pad
26: MEMS layer 102: nozzle
104, 110: channel 105: bond pad
106: joint 112: nozzle inlet
114: ink supply pipe 120: film
130: Printhead assembly 150: Wire bond

Claims (20)

An inkjet printhead assembly comprising an ink supply manifold, at least one printhead integrated circuit, and at least one connector film,
Each printhead integrated circuit comprising:
A silicon substrate having a front surface, a back surface attached to the ink supply manifold, and at least one ink supply channel for providing fluid communication between the back surface and the front surface;
One or more CMOS layers including drive circuits on the front side; And
A MEMS layer disposed over the CMOS layer such that the CMOS layer is positioned between the CMOS layer and the silicon substrate, the MEMS layer including a plurality of inkjet nozzle assemblies;
And,
Wherein the connector film supplies power to the drive circuit,
Wherein the connecting end of the connector film is sandwiched between at least a portion of the ink supply manifold and the at least one printhead integrated circuit,
A plurality of through-silicon connectors provide electrical connection between the drive circuit and the connection end of the connector film,
Each through-silicon connector extending straight from the contact pad in the MEMS layer through the CMOS layer toward the backside,
Wherein the contact pad is electrically connected to the CMOS layer.
The method according to claim 1,
Wherein the connector film is comprised of a flexible polymer film having a plurality of conductive tracks.
The method according to claim 1,
Wherein the connector film is a tape self-bonding (TAB) film.
The method according to claim 1,
Said back surface having a recess for receiving said connector film.
5. The method of claim 4,
Wherein the recess is formed along a longitudinal edge region of each printhead integrated circuit.
The method according to claim 1,
Each through-silicon connector tapering toward the backside.
The method according to claim 1,
Each of the through-silicon connectors being comprised of copper.
The method according to claim 1,
And at least one conductive post extending linearly between the contact pad and the CMOS layer.
The method according to claim 1,
Each through-silicon connector having an outer sidewall comprising an insulating layer.
10. The method of claim 9,
Wherein the outer sidewalls comprise a diffusion barrier layer between the insulating film and the conductive core of the through-silicon connector.
The method according to claim 1,
Wherein each through-silicon connector is connected to the connection end of the connector film by solder.
The method according to claim 1,
Wherein the connector film is bonded to the ink supply manifold along with the plurality of printhead integrated circuits.
13. The method of claim 12,
Wherein the plurality of printhead integrated circuits are disposed in an end-on-end butting arrangement to provide a pagewidth printhead assembly.
The method according to claim 1,
Wherein the front side of the print head is planar and also does not wire bond.
15. The method of claim 14,
Wherein the front side is coated with a hydrophobic polymer layer.
A silicon substrate having a front surface, a back surface for attaching to the ink supply manifold, and at least one ink supply channel for providing fluid communication between the back surface and the front surface;
One or more CMOS layers including drive circuits on the front side; And
A MEMS layer disposed over the CMOS layer such that the CMOS layer is positioned between the CMOS layer and the silicon substrate, the MEMS layer including a plurality of inkjet nozzle assemblies;
And,
Wherein a plurality of through-silicon connectors extend straight from the contact pads in the MEMS layer through the CMOS layer toward the backside,
Wherein the contact pad is electrically connected to the CMOS layer.
17. The method of claim 16,
Wherein at least one conductor post extending linearly is provided between the contact pad and the CMOS layer.
18. The method of claim 17,
Each through-silicon connector having an outer sidewall comprising an insulating film.
19. The method of claim 18,
Wherein the outer sidewall comprises a diffusion barrier layer between the insulating film and the conductive core of the through-silicon connector.
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