Patent Application
20070296767
Further advantages of exemplary embodiments disclosed herein may become apparent by reference to the detailed description of exemplary embodiments when considered in conjunction with the drawings, which are not to scale, wherein like reference characters designate like or similar elements throughout the several drawings as follows:
As set forth above, exemplary embodiments of the disclosure relate to apparatus and methods that may enable reduction in substrate size, an increase in ejector density on a substrate, and/or an increase in ejectors on a substrate without increasing substrate size. An exemplary embodiment of the apparatus and methods described herein includes a conductive component in a polymeric layer rather than requiring it to be on a substrate.
A comparison between
All of the conductive traces, ejection actuators, drivers, and the like, are deposited on the substrate 12. Hence, sufficient substrate area is needed to provide routing of conductive traces to the ejection actuators and other devices. Because of the slot 14, the conductive traces must go around the slot 14 to provide electrical continuity to components on both sides of the slot 14. However, routing conductive traces around the slot 14 may give rise to inequities in series resistance to the fluid ejection actuators as well as increasing the size of the substrate 12 for such conductive trace placement.
The substrate 12 is electrically connected to a flexible circuit (e.g., a TAB circuit), such as by using tab bond pads on the substrate 12. The flexible circuit can only provide connections to edges of the substrate 12 since a major portion of the substrate is covered by the nozzle plate 18. Accordingly, such edge connections require additional conductive traces and contact pad areas on the substrate 12 which tends to increase rather than decrease the size of the substrate 12.
By contrast, embodiments of the disclosure provide an improved micro-fluid ejection head structure 20 as illustrate in
The nozzle plate 26 is suitably a multi-layer nozzle plate. As shown in
A conductive path 28 may be embedded in the nozzle plate 26 between layers 26A and 26B. Electrical contacts 30A and 30B with the substrate 22 are provided by contact holes 32A and 32B in the first nozzle plate layer 26A and in the thick film layer 24. The conductive path 28 may have a thickness ranging from about 1000 Angstroms to about 10 microns, for example.
As illustrated in
Next, the thick film layer 24 may be deposited adjacent the substrate 22, such as by a spin-coating or lamination process. The thick film layer 24 may be imaged and developed to provide the contact holes 32A and 32B therein, and to provide the fluid chambers and fluid supply channels for fluid flow to fluid ejection actuators on the substrate 22. The thick film layer 24 may have a thickness ranging from about 5 to about 50 microns, for example.
As shown in
Next, a conductive material may be applied to at least a portion of the first nozzle plate layer 26A and in the contact holes 32A-32B to provide the conductive path 28 and contacts 30A and 30B. The conductive material providing the conductive path 28, and contacts 30A and 30B, may be applied to the nozzle plate layer 26A, such as by a wide variety of techniques including, but not limited to, fluid jet printing, low temperature sputtering, electrolytic plating, and the like. Accordingly the conductive material may be composed of copper aluminum, silver, nickel, gold, and alloys thereof. A particularly suitable conductive material is copper that is applied by a copper plating technique
By way of example, a copper plating technique for depositing conductive materials on a polymeric layer will now be described. Prior to plating copper onto the first nozzle plate layer 26A, electroless copper deposits are applied to the nozzle plate layer 26A to provide a conductive base for subsequent plating. Such electroless copper deposits typically have a thickness ranging from about 1.0 to about 2.0 microns followed by an additional decorative or protective thickness of copper, nickel, or gold deposited electrolytically or electrolessly. The electroless copper in such applications provides good life in corrosive atmospheric and/or environmental exposures. Likewise, electroless copper may be used to provide excellent electrical conductivity in the contact holes 30A and 30B. Prior to depositing the electroless copper, the first nozzle plate layer 26A may be pretreated by immersing the first nozzle plate layer 26A in an acidic aqueous solution of stannous chloride (SnCl2) and palladium chloride (PdCl2). Many other activators may be used to pretreat the first nozzle plate layer 26A before electroless copper deposition thereon.
The pH of an electroless copper bath used for plating will influence the brightness of the copper deposits. Usually a pH value above about 12.0 is suitable. A dark deposit may indicate low bath alkalinity and contain cuprous oxide. The plating rate is also influenced by the pH. In formaldehyde-reduced baths a pH value of 12.0-13.0 is generally best. Stability of the bath and pH are critical to providing suitable copper deposits. A high pH value (14.0) results in poor solution stability and reduces the bath life. Below a pH of 9.5, solution stability is good; however, deposition slows or ceases.
During the deposition process, the principal components of the electroless copper bath (copper, formaldehyde, and caustic) must be kept within predetermined limits through replenishment. Other bath chemical components may remain within recommended ranges. Complexing agents and stabilizer levels occasionally need independent control. Other key operating parameters include temperature, air agitation, filtration, and circulation.
Various common reducing agents have been suggested, however, the best known reducing agent for electroless copper baths is formaldehyde. A complexing agent (i.e. Rochelle salt) serves to complex the copper ion to prevent solution precipitation and has an effect on deposition rates as well as the quality of the deposits. A stable electroless plating bath has a plating rate of about 1 to about 5 microns per hour and operates in an alkaline solution having a pH ranging from about 10.0 to about 13.0.
An example of a formaldehyde-reduced electroless copper bath is provided in Table I.
Recent formulations allow for alkanol amines such as N,N,N′,N′-tetrakist(2-hydroxypropyl)ethylenediamine-reduced baths. Such baths having high build rates (>10 um/hr) or heavy deposition baths operate at a lower pH without the use of formaldehyde. High build baths generally are more expensive and exhibit less stability but do not have harmful formaldehyde vapors given off during subsequent solution make up, heating, and deposition. Such baths may deposit enough low stress copper to eliminate the need for an electrolytic flash.
Subsequent to depositing the conductive material onto the first nozzle plate layer 26A, the second nozzle plate layer 26B may be applied to the conductive path 28 and first nozzle plate layer 26A. As shown in
In the foregoing illustrations, the contact holes 32A and 32B and contacts 30A and 30B were shown for convenience as substantially vertical holes 32A-32B and contacts 30A-30B. However, as illustrated in
Other embodiments of the disclosure are illustrated in
Yet another embodiment of the disclosure provides a conductive component that is embedded in a polymeric layer of a micro-fluid ejection head. For example, capacitors tend to take up a large amount of substrate area and have a higher fallout due to point defects and particle damage during substrate fabrication. One way to eliminate such defects is to move the capacitors from the substrate and into a control device remote from the substrate. However, moving the capacitors to the control device increases the cost of the control device.
Using the techniques described above, a capacitor may be embedded in the polymeric layer(s) of a nozzle plate and/or thick film layer of a micro-fluid ejection head, for example.
A first nozzle plate layer 90 may be deposited adjacent the thick film layer 70, and imaged and developed to provide a location for the capacitor 60. Once the capacitor 60 is formed, a second nozzle plate layer 92 may be deposited adjacent the first nozzle plate layer 90 to provide the embedded capacitor. It will be appreciated that other conductive devices, including, but not limited to, anti-fuse devices, and fuses may also be embedded in polymeric layers of the micro-fluid ejection head using the techniques described herein.
It is contemplated, and will be apparent to those skilled in the art from the preceding description and the accompanying drawings that modifications and/or changes may be made in the embodiments of the disclosure. Accordingly, it is expressly intended that the foregoing description and the accompanying drawings are illustrative of exemplary embodiments only, not limiting thereto, and that the true spirit and scope of the present disclosure be determined by reference to the appended claims.
