Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-08-16
2003-12-09
Nghiem, Michael (Department: 2863)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06659592
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the design and fabrication of integrated circuits. More specifically, the present invention pertains to the design and fabrication of integrated circuits used in printheads for ink-jet printers.
BACKGROUND ART
Ink-jet printer cartridges include printhead structures in which small droplets of ink are formed and ejected toward a printing medium. The printhead structures have orifice plates incorporating very small nozzles through which the ink droplets are ejected. Ejection of an ink droplet through a nozzle is accomplished by heating a volume of ink in an adjacent ink chamber. The expansion of the ink forces a droplet of ink through the nozzle, a process referred to as “firing.” The ink in the chamber is typically heated with a resistive heating material aligned with the nozzle and chamber.
Prior Art
FIG. 1
illustrates an exemplary ink-jet printer cartridge
12
used in a printer such as a thermal ink-jet printer. A printhead
20
with an orifice plate
33
is fit into the bottom of the cartridge
12
. The printhead
20
includes nozzles
25
through which ink is ejected in a controlled pattern during printing. Depending on the resolution of the printer, an array of 600 or more nozzles may be used. A flexible circuit
24
is mounted to the exterior of the cartridge
12
. Circuit contact pads
23
are for electrically coupling the cartridge
12
to a matching circuit in the printer.
Prior Art
FIG. 2
is a cross-sectional view of a portion of printhead
20
comprising a substrate
10
, a conductive layer
22
, and a printhead structure
40
. For simplicity of illustration, a single printhead structure
40
is shown; however, in actuality, many (e.g., 600) printhead structures are used.
Substrate
10
is typically a silicon wafer although other materials may be used. Substrate
10
may be separated from the conductive layer
22
by an insulation layer
14
(e.g., a dielectric). Insulation layer
14
may be omitted if substrate
10
possesses dielectric and heat transfer characteristics suitable for directly receiving conductive layer
22
.
In general usage and as used herein, conductive layer
22
is a generic term that includes both metallic (e.g., aluminum) lines and complementary metal oxide semiconductor (CMOS) logic circuits. Conductive layer
22
, under control of a microprocessor and associated drivers in the printer, selectively distributes electrical signals to each of the printhead structures
40
so that they fire in a controlled pattern to produce on the printable medium the desired characters and images.
Printhead structure
40
includes resistive heating material (resistor)
30
adjacent to a firing chamber
44
, an ink barrier
38
, and a nozzle
25
formed in orifice plate
33
and in fluid communication with firing chamber
44
. Conductive layer
22
includes a bonding pad
27
to which a lead from flexible circuit
24
(
FIG. 1
) is attached. Flexible circuit
24
carries signals generated by the microprocessor and associated drivers in the printer to conductive layer
22
via bonding pad
27
. These signals prescribe which of the printhead structures
40
are to fire, depending on the character or image to be generated. Conductive layer
22
selectively provides electrical signals to resistor
30
, which in turn produces an amount of heat sufficient for vaporizing some of the ink in firing chamber
44
, thereby forcing an ink droplet through nozzle
25
.
A problem with printheads of the prior art is that care must be taken to ensure that the electrical connections from the printer and/or print cartridge to the printhead structure are not exposed to the ink ejected from the printhead structure. The ink droplets exist as a fine mist (aerosol) and, although directed to the printable medium, may float back onto printhead structure
40
, conductive layer
22
, and the connection between bonding pad
27
and flexible circuit
24
(FIG.
2
). Therefore, the electrical connections and other components are generally coated with some type of protective material to shield them from the ink.
However, the ink is very corrosive and eventually may penetrate the protective coating and damage electrical connections in the bond
27
between conductive layer
22
and flexible circuit
24
, in conductive layer
22
, or elsewhere. Electrical connections to some of the printhead structures or emanating from any other source may consequently fail or degrade to the point where current sufficient for heating resistor
30
cannot be provided. As a result, some of the printhead structures may not fire when they are supposed to, thus reducing print quality. To address this problem, what is needed is a method and/or apparatus that can protect electrical connections in the printhead from the corrosive effects of ink.
Another problem with the prior art is that the routing of the electrical signals to the printhead structures
40
can consume valuable space in printhead
20
. As the number of printhead structures
40
increases (e.g., to achieve higher print qualities), the routing of the signals to the resistors
30
consumes more of the surface area on substrate
10
. In addition, the routing of signals becomes more complex with an increasing number of printhead structures
40
.
These latter problems are also experienced in applications other than ink-jet printers that utilize packaged integrated circuits (e.g., a semiconductor or integrated circuit die coupled with one or more structures or logic devices and mounted on a substrate). Generally, contacts for electrical signals from external sources to a packaged integrated circuit are situated toward the edge of the package or substrate. External electrical signals are therefore routed to the edge of the package or substrate, then routed to the various devices or structures that are included in the package. As logic devices become more complex, the routing of electrical signals to the integrated circuit package and within the package becomes more difficult and consumes greater quantities of the limited space available.
Therefore, what is also needed is a method and/or apparatus that can reduce the difficulty of routing electrical signals to integrated circuits and integrated circuit packages and that can reduce the area consumed by such routing, not only in ink-jet printers but in other applications as well. The present invention provides a novel solution to the above needs.
DISCLOSURE OF THE INVENTION
The present invention provides both an apparatus that can protect electrical connections from the corrosive effects of ink in an ink-jet printer and a method of forming such an apparatus. In addition, the present invention provides an apparatus (and a method for forming an apparatus) that can reduce the difficulty of routing electrical signals and that can reduce the area consumed by such routing, not only in ink-jet printers but in other applications as well.
The present invention pertains to an apparatus incorporating multiple electrical interconnects extending through a substrate (e.g., a silicon wafer). The electrical interconnects convey electrical signals through the substrate to structures (devices) mounted on the front side of the substrate. Accordingly, it is not necessary to route electrical signals to or along the front surface of the substrate in order to convey the signals to the structures, thereby reducing the difficulty of routing electrical signals as well as reducing the area consumed by such routing.
In one embodiment, each structure is electrically coupled to multiple parallel electrical interconnects extending through the substrate such that the electrical signals are carried to the structure by redundant electrical paths. The use of redundant paths can improve reliability because if an electrical interconnect should fail, electrical signals are still provided to the structure through the remaining interconnects.
In one embodiment, the present invention is implemented in an ink-jet print cartridge. The electrical interconnects convey electrical signals through the substra
Hellekson Ron Allen
I-Tsung Pan Alfred
Snyder Barry Craig
Vander Plas Hubert Allen
Hewlett--Packard Development Company, L.P.
Nghiem Michael
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