Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2003-01-03
2004-12-21
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S610100, C029S620000, C029S846000, C361S058000, C347S058000, C347S062000, C347S067000
Reexamination Certificate
active
06832434
ABSTRACT:
TECHNICAL FIELD
The present invention relates to print heads for thermal ink jet printers and, more particularly, to methods of forming thermal ink jet resistor structures for use in nucleating ink.
BACKGROUND
In the field of thermal ink jet printing, it has become a common practice to provide heater resistors on a common substrate and align these heater resistors with individual ink reservoirs and corresponding ink ejection orifices in an outer nozzle plate. These heater resistors are physically defined and electrically driven by conductive traces which can be photolithographically formed on the surface of a suitable resistor layer material, such as tantalum-aluminum. These heater resistors have been traditionally isolated from the overlying ink reservoirs by dielectric materials such as silicon carbide and silicon nitride. This type of thermal ink jet printhead is described, for example, in the Hewlett Packard Journal, Vol. 36, No. 5, May 1985, incorporated herein by reference.
Consider, for example,
FIG. 1
which shows a cross-sectional view of an exemplary ink reservoir and resistor for ejecting ink. Specifically, a substrate
102
such as silicon, supports a number of ink reservoirs
104
. Each reservoir is configured to receive ink that is to be ejected. A heater or resistor
106
is disposed within the reservoir, and a passavation layer
107
comprising a dielectric material is formed over the resistor
106
. To expel a jet of ink, the heater or resistor is heated rapidly which causes a vapor bubble
108
to form within the ink reservoir
104
. This vapor bubble then causes a quantity of ink
110
to be ejected out of the channel and towards a page that is to be printed upon.
One of the problems associated with ink jet printers and, particularly, the resistors that are used as heaters to heat the ink, is that over time, the resistor can begin to work improperly due to defects that are present in the material of the resistor. Improper resistor operation can also be caused by things such as contamination or voids in layers that are either over or under the resistor, and the presence of voids or cavitation damage. Specifically, resistors are typically formed using thin film techniques where a conductive material, such as tantalum aluminum, is deposited over a substrate and etched to form a desired resistor. This layer is a very thin layer. The resistor layer can have material defects in it which, over time and due in large part to the continual heating and cooling of the material, cause the resistor to effectively malfunction, open up or fuse. When the resistor fails to work, ink cannot be ejected from the ink reservoir and, hence, the integrity of the printer in which the resistor resides can be compromised.
SUMMARY
Methods of forming thermal ink jet resistor structures for use in nucleating ink are described.
In one embodiment, a method comprises forming a layer of conductive material over a substrate, and patterning and etching the layer of conductive material effective to form one or more arrays of resistors. Individual arrays comprise multiple, parallel-connected resistor elements and the resistor elements are configured such that failure of any one resistor element will not render its associated resistor array inoperative for nucleating ink. The resistor elements of individual arrays are formed such that collectively, the resistor elements are not independently addressable.
In another embodiment, a method comprises forming a layer of conductive material over a substrate, and forming, from the layer of conductive material, one or more arrays of resistors. Individual arrays comprise multiple, parallel-connected resistor elements and the resistor elements are configured such that failure of any one resistor element will not render its associated resistor array inoperative for nucleating ink. The resistor elements of individual arrays are formed such that collectively, the resistor elements are not independently addressable.
In a further embodiment, a method comprises forming a layer of conductive material over a substrate, where the substrate comprises a material selected from a group of materials comprising: glass, SiO
2
, SiO
2
over silicon, and SiO
2
over glass. The method further comprises forming, from the layer of conductive material, one or more arrays of resistors. Individual arrays comprise multiple, parallel-connected resistor elements and the resistor elements are configured such that failure of any one resistor element will not render its associated resistor array inoperative for nucleating ink. The resistor elements of individual arrays are formed such that collectively, the resistor elements are not independently addressable.
In another embodiment, a method comprises forming a layer of conductive material over a substrate, where the substrate comprises a material selected from a group of materials comprising: glass, SiO
2
, SiO
2
over silicon, and SiO
2
over glass. The method further comprises forming a masking layer over the substrate, patterning the masking layer to form one or more resistor array patterns, and etching the layer of conductive material through the patterned masking layer effective to form one or more arrays of resistors. Individual arrays comprise multiple, parallel-connected resistor elements. The resistor elements are configured such that failure of any one resistor element will not render its associated resistor array inoperative for nucleating ink. The resistor elements of individual arrays are formed such that collectively, the resistor elements are not independently addressable.
In yet another embodiment, a method comprises forming a first resistor element over a substrate and forming at least one other resistor element over the substrate and operably connected in parallel with the first resistor element. The resistor elements are formed for redundancy such that if one of the resistor elements fails, one or more remaining resistor elements can function to effectuate ink ejection. The resistor elements are formed such that they are not independently addressable.
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Rausch John B.
Shade David A.
Arbes Carl J.
Hewlett--Packard Development Company, L.P.
Phan Tim
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