Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-07-05
2003-09-09
Nguyen, Judy (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06616269
ABSTRACT:
This application is based on Patent Application No. 2000-209101 filed Jul. 10, 2000 in Japan, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a substrate for an ink jet print head, an ink jet print head and a manufacture method thereof, and more particularly to a structure of a bump electrode pad used for electrical connection between the substrate and electric wiring such as a TAB tape, both forming the ink jet print head.
2. Description of the Prior Art
The manufacture of an ink jet print head involves a process of connecting two components: a head chip (hereinafter simply referred to as a “chip” or “print element substrate”), which is composed of a substrate has formed therein heaters and a driver IC and matrix wires for driving the heaters and a nozzle forming member in which ink ejection ports are formed, and a TAB tape electrically connects the print head to a printer body. This connecting process is normally performed by using both heat and ultrasonic wave to connect the bumps provided on the electrode pad on the chip to inner leads of the TAB tape.
A commonly used bump is a so-called plated bump which is formed by forming and patterning a SiO
2
or SiN film as a passivation layer, forming one to three layers of barrier metal such as Ti, Cu and W as a contact improving layer on aluminum electrodes, forming a resist pattern over the barrier metal layer by photolithography, and finally growing gold by electrolytic plating.
The forming of the plated bump requires performing several cycles of a vacuum film forming process and an exposure/development process. Because in the case of the plated bump an entire wafer is subjected to the plating process, not only sound chips but also chips that become faulty in the subsequent steps are formed with gold-plated bumps. This leads to a possible increase in cost. Further, when the number of electrode pads per the wafer is small (i.e., when the number of bumps is small), the cost per bump increases.
For these reasons, an increasing number of a ball bumps are being used in recent years. The ball bump is formed by using the wire bonding method. In this forming process an arc discharge is applied to the front end of a wire passed through a ceramic tube called capillary to form a ball, which is then joined to a predetermined electrode pad on the substrate by using both heat and ultrasonic wave. Then, the capillary is lifted while at the same time the wire is held by a cut clamper, thus fracturing the wire by a tensile strength to cut off the ball portion and thereby form a bump. Another method of joining the balls to the electrode pad is known to use only heat, rather than using both heat and ultrasonic wave as in the above method.
As described above, the ball bump does not require the expensive vacuum film forming device and exposure device as do the plated bump. Further, because the passivation film and the barrier metal are not necessary, the ball bump is more advantageous than the plated bump in terms of cost when the number of pads per a piece of wafer is small.
In an ink jet print head that uses thermal energy produced by a heater to eject ink, films making up the heater or the like tend to decrease in thickness. The structure of this type of print head will be discussed as follows in terms of the thickness of the film tending to decrease.
An example substrate making such an ink jet print head is made by successively forming on a silicon base an IC film (made up of about six layers) for a driver IC or the like which consists of semiconductor devices to drive the heater in ejecting ink, a first interlayer insulating film (e.g., SiN film) forming a lowermost layer in contact with the base, a first electric wiring film (e.g., Al film) forming a common electrode for supplying an electric power to drive the heater by the driver IC in response to a drive signal or a common electrode for grounding, a second interlayer insulating film (e.g., SiO film) overlying the first electric wiring film, a heater film (e.g., TaN film) forming the heater, a second electric wiring film (e.g., Al film) directly connected to the heater to supply an electric power to the heater, and a wear resistant film (e.g., Ta film) overlying the second electric wiring film.
FIG. 16
is a plan view showing a conventional example of a heater and an electric wire for driving the heater corresponding to one ejection port in the substrate for the ink jet print head of the type described above.
FIG. 17
is a perspective view showing a head chip made by forming, on the substrate having the electric wiring film or the like, a nozzle forming member in which ink ejection ports or the like are formed.
In order to selectively drive a plurality of heaters to eject ink according to print data, the substrate for the print head is normally formed with a matrix electrode wire. In
FIG. 16
a first electric wire
202
represents a common electrode forming a part of the matrix wire and is connected in a through-hole portion
105
to a second electric wire
205
which in turn is connected to a heater film
204
forming a heater
101
. More specifically, as described later by referring to
FIG. 18
, the first electric wire
202
is formed as lower layer with respect to a direction of thickness of the substrate, and this wire
202
and the second electric wire
205
formed as an upper layer than the wire
202
are generally formed in separate steps in a substrate making process and thus are electrically interconnected via the through-holes. Further, as to the connections for supplying an electric power and a drive signal to the head chip and connections for grounding the substrate potential, the substrate is formed at its end portions with electrode pads
110
, as shown in
FIG. 17
, for electrical connection to a printer body.
FIG. 18
is a cross section showing a film structure of mainly the heater portion
101
, the through-hole portion
105
and the electrode pad portions
110
in the above substrate structure.
The film structure of the heater
101
and its vicinity is presented in
FIG. 18
as a cross section taken along the line
18
a
—
18
a
of FIG.
16
. On the silicon base
11
are laminated a first interlayer insulating film
201
, a second interlayer insulating film
203
, a heater film
204
, a part of the second electric wire film
205
, a protective film
206
, and a wear resistant film
207
.
In
FIG. 18
the film structure of the through-hole portion
105
that connects the first electric wire film
202
and the second electric wire film
205
is presented as a cross section taken along the line
18
b
—
18
b
of FIG.
16
. On the silicon base
11
are successively laminated the first interlayer insulating film
201
, the first electric wire film
202
, the second interlayer insulating film
203
, the heater film
204
, the second electric wire film
205
, the protective film
206
and the wear resistant film
207
. In this film structure, the second interlayer insulating film
203
is partly formed with through-holes to electrically connect the first electric wire film
202
to the second electric wire film
205
through the heater film
204
.
Further, in
FIG. 18
the film structure of the electrode pad is presented as a cross section taken along the line
18
c
—
18
c
of FIG.
17
. The first interlayer insulating film
201
, the first electric wire film
202
, the heater film
204
, and the second electric wire film
205
are successively laminated.
As described above, although the first electric wire film
202
and the second electric wire film
205
are electrically connected together, they are formed as separate films owing to different functions performed. That is, they are formed in separate manufacture processing steps. In more concrete terms, the first electric wire film
202
is formed under the heater film
204
. On the other hand, the second electric wire film
205
is formed over the heater film. For the sake of the film making process, the heater film
204
and t
Brooke Michael S
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Judy
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