Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-04-27
2003-07-08
Tugbang, A. Dexter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S890100, C029S841000, C029S855000, C204S492000, C204S493000, C204S499000, C204S500000, C347S057000, C347S058000
Reexamination Certificate
active
06588095
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the protection of conductive surfaces in electrical circuits and, in particular, to the protection of conductive surfaces in a thermal inkjet print head circuit.
BACKGROUND OF THE INVENTION
Generally, an inkjet image is formed when a precise pattern of dots is ejected from a drop generating device known as a “print head” onto a printing medium. The typical inkjet print head has an array of precisely formed nozzles in an orifice plate that is attached to an ink barrier layer on a thermal inkjet print head substrate.
FIG. 1
shows a print head substrate
12
with a single nozzle
10
A formed in an orifice plate
10
. The substrate incorporates an array of firing chambers that receive liquid ink from an ink reservoir. Referring to
FIG. 1
, each chamber
11
has a thin-film resistor
13
, known as a “firing resistor”, located opposite each nozzle
10
A so ink can collect between the firing resistor and the nozzle. When electric printing pulses heat the thermal inkjet firing resistor, a small volume of ink adjacent the firing resistor is heated, vaporizing a bubble of ink, and thereby ejecting a drop of ink from the print head. The droplets strike the printing medium and then dry to form “dots” that, when viewed together, form the printed image.
Control signals for causing the resistors to “fire” originate from the printers processing unit. An electrical connection is established with the thin film resistor
13
by lithographically patterned conductive traces (not shown) connected between the resistor and an exposed bonding pad
14
remotely located from the resistor. The bonding pad facilitates connection with an exposed conductive lead on a flexible tape circuit
15
(also referred to as a flex circuit) that is carried on the print head. The flex circuit conveys control or “firing” signals from the printer's processor to the resistor.
The flex circuit is particularly suited for connecting electrical components where one or both connections may be coupled to moving parts. For example, in the case of an inkjet printer, the print head, which is scanned across the print media while ejecting droplets of ink, is electrically connected to the printer's processor with a flex circuit. In general, flex circuits are fine, conductive filaments or formed traces laminated between, overmolded with, or otherwise adhered to, a layer of a flexible, dielectric material, such as a polyimide tape. The interconnect circuit so formed can be bent or looped without affecting the electrical interconnections between the electrical components it connects.
A connection between a given firing resistor
13
and a conductive trace on the flex circuit
15
is created by attaching a conductive bonding beam
16
from the bonding pad
14
to the trace. After bonding, exposed conductive connection areas including at least the bonding pads, bonding beams and conductive traces on the flex circuit are protected/covered from the corrosive environment of the print head.
A previous approach for protecting the exposed conductive connection uses two different coating techniques to accommodate the surface characteristics of two distinct areas of the exposed connection. Specifically, since a first area including the bonding pad
14
and the bonding beam
16
is characterized by small crevices and irregularly shaped surfaces, this area is protected by dispensing a drop of protective coating
17
(including the pad and beam) thereby filling-in small crevices that are hard to coat and covering the entire area. On the other hand, a second area including the exposed conductive traces on the flex circuit
15
is characteristically planer. Consequently, this area is more adapted to a process in which the protective coating is laminated over the exposed traces using, for instance, a screen coating, or sheet/curtain process, thereby forming a protective layer of lamination
18
over the area.
One disadvantage of this coating technique is that due to the irregularity of the surface of the first area, the dispensed coating may have small unprotected pin holes or bubbles and may be unevenly distributed—resulting in unreliable protection of this area. In addition, covering the first and second areas using different processing techniques results in additional processing steps. Moreover, gaps of protection can occur between the dispensed protective coating
17
and the laminated coating
18
.
What would be desirable is a reliable method of protecting the exposed connection areas between a print head and a flex circuit or, in general, between a device and a flex circuit using a single coating process.
SUMMARY OF THE INVENTION
A method of processing and a structure formed thereof. The method is performed on an exposed conductive connection area between a first device and a flexible tape circuit by coupling the exposed connection to a first voltage and immersing the exposed connection in an electrophoretic solution in contact with an electrode at a second voltage potential thereby establishing a current between the electrode and the exposed connection such that the exposed connection is coated with a thin insulating film of uniform thickness by electrophoretic plating.
In a second embodiment of the method of processing and a structure formed thereof, the method is performed on an exposed conductive connection between a thermal inkjet device and a flexible tape circuit connectable to control signals for driving the thermal inkjet device. The method is performed by coupling the exposed connection to a first voltage and immersing the exposed connection in an electrophoretic solution in contact with an electrode at a second voltage potential thereby establishing a current between the electrode and the exposed connection such that the exposed connection is coated with a thin insulating film of uniform thickness by electrophoretic plating.
REFERENCES:
patent: 4208261 (1980-06-01), Todoroki et al.
patent: 4321290 (1982-03-01), Thams
patent: 5116472 (1992-05-01), Wolter et al.
patent: 5830340 (1998-11-01), Iljitch et al.
patent: 6033547 (2000-03-01), Trau et al.
patent: 0092321 (1983-10-01), None
patent: 0593175 (1994-04-01), None
patent: 63301591 (1988-08-01), None
patent: 2-4892 (1990-01-01), None
patent: 02267992 (1990-01-01), None
patent: 05021680 (1993-01-01), None
Hewlett-Packard Development Company LP.
Tugbang A. Dexter
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