Performance inkjet printhead chip layouts and assemblies

Details Performance inkjet printhead chip layouts and assemblies Performance inkjet printhead chip layouts and assemblies

1999-11-16

2003-06-10

Tran, Huan (Department: 2861)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

C347S059000

Reexamination Certificate

active

06575562

ABSTRACT:

TECHNICAL FIELD
The present invention relates to inkjet printhead chip layouts and, more specifically, to ink jet printhead chips having an asymmetric layout wherein the heaters and TAB bond pads are located on opposing edges, and to inkjet printhead assemblies.
BACKGROUND OF THE INVENTION
Ink jet printers typically include recording heads, referred to hereinafter as printheads, that employ transducers which utilize kinetic energy to eject ink droplets. For example, thermal printheads rapidly heat thin film resistors (or heaters) to boil ink, thereby ejecting an ink droplet onto a print receiving medium, such as paper. According to this ink jet method, upon firing a resistor, a current is passed through the resistor to rapidly generate heat. The heat generated by the resistor rapidly boils or nucleates a layer of ink in contact with or in proximity to a surface of the resistor.
The nucleation causes a rapid vaporization of the ink vehicle, creating a vapor bubble in the layer of ink. The expanding vapor bubble pushes a portion of the remaining ink through an aperture or orifice in a plate, so as to deposit one or more drops of the ink on a print receiving medium, such as a sheet of paper. The properly sequenced ejection of ink from each orifice causes characters or other images to be printed upon the print receiving medium as the printhead is moved relative to the print receiving medium.
Typically, the orifices provided on such a plate are arranged in a pair of linear arrays. Moreover, the paper is typically shifted each time the printhead moves across the paper. The thermal ink jet printer is generally fast and quiet, as only the ink droplet is in contact with the paper. Such printers produce high quality printing and can be made both compact and economical.
There are many performance issues that should be considered when designing inkjet printers. Many of these issues are tied to the inkjet technology and, more specifically, to the design of the chips used in the printheads. In many regards, the printhead chip architecture and design dictates the overall performance of the printer.
Overall, however, the performance goals of printhead chip design must also be balanced with meeting cost and manufacturability requirements. For example, the cost of processed silicon is a first order function of chip area. Therefore, in order to minimize cost, the area of any chips used in the printhead should be minimized.
Conventional printhead chip architectures, such as those shown in
FIGS. 1A and 1B
, target specific design requirements, but have certain limitations. For example, center via ink feed chips
111
might ease printhead assembly, but the center via
116
takes up valuable area on the chip and makes the chip prone to cracking. Moreover, additional area on the chip is also required to wire the control and drive signals of the chip around the via
116
, as represented by chip wiring
121
.
Edge ink feed designs (commonly referred to as “edgefeeds”), such as those utilized by the chip
211
shown in
FIG. 1B
, have arisen as an alternative to center via ink feed designs. Edgefeeds do not have a via, but rather have heaters
224
on opposing edges of the chip
211
, with interconnects
270
on opposing ends of the chip. Accordingly, as there is no center via, less area on the chip is wasted, and the chips
211
are not as prone to cracking.
Typically, interconnects
270
(e.g., TAB bond pads) and their corresponding beams
271
(e.g., beams coming from a TAB circuit) must be protected from the ink, such as by covering them with encapsulant
272
for example. These areas of applied encapsulant
272
generally constitute the points on the printhead
210
that will come the closest to contacting the print receiving medium
232
as it is passed by the printhead. Therefore, as shown in
FIG. 2
, to avoid smearing any ink applied to the print receiving medium
232
, it is desirable to maintain an appropriate gap (G) (commonly referred to in the art as the “paper gap”) between the print receiving medium and the printhead
210
.
The distance (D) over which the paper gap (G) must be maintained is commonly referred to in the art as the critical paper gap control region. As can be understood, ensuring a proper paper gap (G) becomes more difficult as critical paper gap control regions (D) increase. For example, because the interconnects
270
in conventional edgefeeds are placed at the ends of the chip
211
, there is a substantial distance between areas of encapsulant
272
. As these areas of encapsulant
272
define a substantial critical paper gap control region (D), controlling the paper gap (G) in printers utilizing conventional edgefeed printhead chips
211
can often be difficult.
Moreover, inkjet printers typically utilize devices, such as an exit roller or star wheel
238
, for example, to maintain the paper gap (G). The distance (M) the print receiving medium
232
must travel past the last appropriate nozzle position (N) on the printhead
211
in order to be held at the desired paper gap (G) over the critical paper gap control region (D) (e.g., the distance the print receiving medium must travel to effectively reach a device such as device
238
), is commonly referred to in the art as the minimum print margin. The minimum print margin (M) defines, for example, how close to an edge of the print receiving medium
232
the printer can print without potentially experiencing print quality problems. As can be understood from
FIG. 2
, because of the additional area on the printhead required to bond (and encapsulate) the relevant portions of the connecting circuit (not shown) to the interconnects (not shown) of the chip
211
, printers using conventional edgefeed printhead chips typically also suffer from larger minimum print margins (M).
Accordingly, it would be advantageous to have an inkjet printhead chip design that has reduced dimensions. Moreover, it would be advantageous to have an inkjet printhead chip design that could retain the benefits of a conventional edgefeed design, while minimizing the critical paper gap control region (D). Furthermore, it would be desirable to have an inkjet printhead chip design that retains the benefits of conventional edgefeed designs while minimizing the minimum paper margin (M).
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide printhead chips that overcome problems associated with conventional chips.
It is another object of the present invention to provide inkjet printhead chips that minimize the critical paper gap control region (D) in the printer in which it is used.
It is a further object of the present invention to provide printhead chips that minimize the minimum paper margin (M) in the printer in which it is used.
Still another object of the present invention is to provide printhead chips that are easy to manufacture and assemble.
Yet a further object of the present invention is to provide inkjet printhead chips that have a minimized chip area.
Still another object of the present invention is to provide printhead chips with improved operational characteristics.
A further object of the present invention is to provide printhead chips that are inexpensive to produce.
According to one embodiment of the present invention, an inkjet printhead chip comprises a substrate, a plurality of transducers, a plurality of interconnects and driver circuitry capable of electrically connecting the transducers and the interconnects. The plurality of transducers are arranged along a first edge of a surface of the substrate. Meanwhile the plurality of interconnects are arranged along an opposing second edge of the surface of the substrate. The driver circuitry is arranged on the substrate.
Preferably, the plurality of transducers are capable of receiving ink along the first edge. In one embodiment of the present invention, the transducers are capable of receiving ink only along this first edge. More preferably, a plurality of transducers are arranged only along the first edge, while the plurality of interconnects are arranged

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