Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-08-01
2001-11-13
Vo, Anh T. N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S040000
Reexamination Certificate
active
06315385
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to thermal ink jet pens, more particularly, to an improved construction of the printheads for easier manufacturing.
BACKGROUND
A prior art ink-jet printer typically includes a printing cartridge or pen in which small droplets of ink are formed and ejected toward a printing medium. Such pens include printheads with orifice plates having very small orifices or nozzles through which the ink droplets are ejected. Adjacent to the orifices inside the printhead are ink chambers, where ink is stored prior to ejection. Ink is delivered to the ink chambers through ink channels. Each orifice and associated structure which defines the ink chamber and ink channel is commonly known as a firing element. A manifold in the pen connects the firing elements to an ink supply. The ink supply may be, for example, contained in a reservoir part of the pen.
Ejection of an ink droplet through an orifice may be accomplished by quickly heating a volume of ink within the adjacent ink chamber. The rapid expansion of ink vapor forces a drop of ink through the orifice. This process is called “firing.” The ink in the chamber may be heated with a transducer such as a resistor that is aligned adjacent to the orifice. If the orifice is not properly aligned with the transducer, the print quality of the pen can be adversely affected.
The current construction of orifice plates and method of attaching the orifice plates to printhead dies are prone to result in printheads whose orifice pates are misaligned.
FIGS. 1
is a cross-sectional view of a prior art mandrel
2
. This mandrel has a metallic layer
4
deposited on a substrate
6
. The metallic layer
4
is appropriately photolithographically patterned and etched to provide a molding surface for electroforming an orifice plate
8
. Holes in the metallic layer
4
have surfaces that electroform orifices
10
in the orifice plate
8
. The orifice plate
8
that is formed by using such a prior art mandrel
2
is substantially uniformly thick and has a substantially flat surface
12
. During the manufacturing of a printhead (not shown), it is this surface
12
of the orifice plate
8
that is attached to a barrier layer on a printhead die (not shown).
To increase manufacturing productivity, many such orifice plates are formed as a single sheet on an appropriate mandrel. After being electroformed to a predetermined thickness, the orifice plates are singulated for attaching individually to a printhead die. A machine picks and places each orifice plate over a corresponding printhead die on a wafer containing many such dies. The wafer and attached orifice plates are put through a “stake and bake” process to cause the orifice plates to adhere to the printhead dies. After the “stake and bake” process, each printhead consisting of a printhead die and an orifice plate is singulated using dice sawing. Each complete pair of orifice plate and printhead die is then ready for attaching to a pen body to complete the fabrication of an ink-jet pen.
During the “stake and bake” process, pressure is applied to the orifice plate to hold it in place over the printhead die. This pressure has the tendency to cause the orifice plate to shift and as a result become misaligned. Another recurring problem is adhesion of the orifice plate to the printhead die. Delamination can occur from residual stresses.
It is therefore desirable to have an orifice plate that ameliorates the misalignment and delamination problems associated with prior art electroformed orifice plates.
EP 0641 659 discloses a means of attaching an orifice plate made of tape automated bonding (TAB) circuit or flexible circuit on a printhead die so that orifices on the orifice plate are aligned over transducers on the printhead die. The alignment is achieved by copper traces on the TAB or flexible circuit mating with correspondingly etched channels in a barrier layer on the printhead die. With such alignment, only rough alignment is required when attaching the orifice plate to the printhead die. As the two are brought into contact, they tend to lock in place.
Such an alignment method works for a flexible circuit orifice plate but cannot be easily and economically duplicated for metal orifice plates. Firstly, copper traces cannot be run on metal orifice plates. With prior art methods of electroforming metal orifice plates, it is impossible for similar traces to be created on the metal orifice plates.
There is also a difference between the manufacturing process of a pen with a flexible circuit orifice plate and one with a metal orifice plate. For the former, the flexible circuit orifice plate is attached only after the printhead die is attached to a pen body. At such a stage, if there is any pen failure due to misalignment of the flexible circuit orifice plate, the whole pen is discarded. For the case of a metal orifice plate, the orifice plate is attached to the printhead die before the combination is attached to a pen body. The combination can be tested before attaching to a pen body. Yield loss in the manufacturing of metal orifice plate pens is therefore lower, making manufacturing of such pens preferable to those with flexible circuit orifice plates.
It is therefore advantageous to be able to create an electroformed orifice plate that can be attached to a printhead die so that orifices on the orifice plate are aligned over transducers on the printhead die.
SUMMARY
In one aspect of the present invention, a printhead according to a preferred embodiment has a non-uniformly thick electroformed orifice plate having orifices electroformed therethrough. This electroformed orifice plate has a thin area and a thick area. The thick area defines projections from the thin area. The printhead also has a printhead die that includes transducers on a substrate. Each transducer matches to one of the orifices of the orifice plate. The printhead also has a barrier layer on the substrate that is developed to define ink channels and ink chambers for delivering ink to the transducers. The barrier layer is also developed to define a locator. When the orifice plate is attached to the printhead die during assembly, the projections on the orifice plate mesh with the locator on the barrier layer to substantially hold the orifice plate and the printhead die in place to align each orifice to a corresponding transducer.
In another aspect of the present invention, a method for assembling the above-mentioned thermal ink jet printhead involves applying an appropriate amount of adhesive to one or both of the orifice plate and the barrier layer. Next, the method includes attaching the orifice plate to the printhead die so that the projections on the orifice plate mesh with the locator of the barrier layer to form a printhead and to substantially hold the orifice plate and the printhead die in place to align each orifice with a corresponding transducer. The printhead is finally baked to allow the orifice plate to be bonded to the printhead die.
REFERENCES:
patent: 5774149 (1998-06-01), Shimizu
patent: 5971522 (1999-10-01), Ono et al.
patent: 0641659 (1998-01-01), None
Hewlett--Packard Company
Vo Anh T. N.
LandOfFree
Self-locating orifice plate construction for thermal ink jet... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Self-locating orifice plate construction for thermal ink jet..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Self-locating orifice plate construction for thermal ink jet... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2600590