Substrate for ink jet print head, ink jet print head and manufacturing methods therefor

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 the second electric wire film

205

are also formed in the electrode pad portion

110

along with the heater portion

101

and the through-hole portion

105

. The second electric wire film

205

in the electrode pad portion

110

forms a surface conductive film in contact with the ball bumps.

In the bubble jet type print head composed of the substrate with the above-described structure, the density of ink ejection ports and their associated structures in the print head are being increasingly enhanced in recent years to cope with the growing demands for faster printing and higher print quality. Such an increase in density may cause a problem of a heat generation or heat storage. For example, the heat generated by the heater in ejecting ink is mostly released outside together with the ejected ink droplet, with the remaining heat, which is small, accumulated in the head when the printing process continues. When the ink ejection ports are arranged in high density, the extent to which the heat is accumulated increases, causing the head temperature to rise, resulting in an ejection failure or a broken head.

To deal with this problem, it is important to minimize the amount of energy applied to the print head for ink ejection. In this respect, measures to improve the thermal efficiency of ink ejection include, for example, reducing the thickness of the protective film over the heater film to transfer heat to the ink with an increased efficiency. For example, reducing the thickness of the protective film from the conventional 8000 Å to 3000 Å can reduce the energy applied to the print head at time of ink ejection by about 40%.

Such a reduction in the thickness of the protective film, however, degrades a coverage by the protective film of stepped portions of the electric wires. To deal with this situation, the second electric wire film

205

such shown in

FIG. 18

, which is covered by the protective film and formed over the heater film, is reduced in thickness to minimize a vertical difference between levels at the stepped portion and thereby prevent the deterioration of step coverage. For example, the aluminum film of the electric wire is reduced in thickness from the conventional 4,000 Å to 2,000 Å.

However, the above-described reducing the thickness of the second electric wire causes reducing the thickness of the second electric wire film in the electrode pad portion, i.e., the surface conductive film in contact with the ball bumps. As a result, the ball bumps may result in a faulty joint and, in the worst case, may cause a bump loss, the phenomenon in which bumps come off the electrode pad. For example, when gold is used as a material of the ball bump and an aluminum electric wiring layer is used as a surface conductive film that comes into contact with the bumps on the electrode pad, the frequency of the bump loss generally increases as the thickness of the aluminum electric wiring layer decreases.

As described above, a trouble may occur in which the surface conductive film fails to adhere to the ball bumps or their joining strength is weak (generally evaluated by the strength measured by a shear tester). This is explained as follows. Because the second electric wire film of, for example, aluminum formed over the relatively hard heater film is thin, resulting in a reduced joining strength of an alloy of gold ball bump and aluminum joined by ultrasonic bonding. Increasing the intensity of the ultrasonic wave for solving this problem, however, may cause cracks in the pad portion in the substrate. Further, to minimize the energy necessary for ink ejection requires a further reduction in the thickness of the protective film and its associated second electric wire film, for example, down to 1,500 Å and 1,000 Å, respectively. This in turn makes the problem of poor junction of ball bumps more significant.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a substrate for an ink jet print head, an ink jet print head and a method of manufacture thereof, which assures a satisfactory joint between a ball bump and an electrode pad regardless of a reduction in the film thickness in the substrate for the ink jet print head.

In a first aspect of the present invention, there is provided a substrate for an ink jet print head that uses thermal energy to eject ink, the substrate comprising:

a film structure having a plurality of films laminated over the substrate, the plurality of films including a first electric wire film, a heater film and a second electric wire film formed one upon the other in that order over the substrate, a combination of the heater film and the second electric wire film allowing the thermal energy to be generated;

wherein an electrode pad portion, which is formed at a part of the film structure to make electrical connection to other than the substrate through a ball bump, is formed by an exposed part of the first electric wire film, and a thickness of the first electric wire film is larger than that of the second electric wire film.

In a second aspect of the present invention, there is provided an ink jet print head which uses thermal energy to eject ink, comprising:

a substrate making the ink jet print head, the substrate including:

a film structure having a plurality of films laminated over the substrate, the plurality of films including a first electric wire film, a heater film and a second electric wire film formed one upon the other in that order over the substrate, a combination of the heater film and the second electric wire film allowing the thermal energy to be generated;

wherein an electrode pad portion, which is formed at a part of the film structure to make electrical connection to other than the substrate through a ball bump, is formed by an exposed part of the first electric wire film, and a thickness of the first electric wire film is larger than that of the second electric wire film.

In a third aspect of the present invention, there is provided a method of manufacturing an ink jet print head which uses thermal energy to eject ink, the method comprising the steps of:

forming a substrate, the substrate constituting the ink jet print head and having a film structure, the film structure having at least a first electric wire film, an interlayer insulating film, a heater film, a second electric wire film and a protective film laminated one upon the other in that order over the substrate, a combination of the heater film and the second electric wire film allowing the thermal energy to be generated;

wherein, in an electrode pad portion formed by a part of the step of forming the film structure of the substrate and adapted to make electrical connection to other than the substrate through a ball bump, the interlayer insulating film is removed to expose the first electric wire film and to make an exposed part of the surface first electric wire film be a part to which the ball bump are joined.

In a fourth aspect of the present invention, there is provided a method of manufacturing an ink jet print head which uses thermal energy to eject ink, the method comprising the steps of:

forming a substrate, the substrate constituting the ink jet print head and having a film structure, the film structure having at least a first electric wire film, an interlayer insulating film, a heater film, a second electric wire film and a protective film laminated one upon the other in that order over the substrate, a combination of the heater film and the second electric wire film allowing the thermal energy to be generated;

wherein, in an electrode pad portion formed by a part of the step of forming the film structure of the substrate and adapted to make electrical connection to other than the substrate through a ball bump, after the interlayer insulating film is patterned to form a window therein, the heater film and the second electric wire film are deposited one upon the other and then removed to expose the first electric wire film and to make an exposed part of the surface first electric wire film be a part to which the ball bump are joined.

With the above construction, because the exposed part of the first wire electrode underlying the heater forms the electrode pad, a film which does not need to be reduced in thickness to secure the heater protective film's step coverage even when the protective film is made thinner can be used for the electrode pad. Further, an inherently thick film can be used for the electrode pad. As a result, when the ball bump is joined by an ultrasonic bonding process bonding, the bonding strength can be increased.

The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a perspective view showing an external construction of an ink jet printer as one embodiment of the present invention;

FIG. 2

is a perspective view showing the printer of

FIG. 1

with an enclosure member removed;

FIG. 3

is a perspective view showing an assembled print head cartridge used in the printer of one embodiment of the present invention;

FIG. 4

is an exploded perspective view showing the print head cartridge of

FIG. 3

;

FIG. 5

is an exploded perspective view of the print head of

FIG. 4

as seen diagonally below;

FIGS. 6A and 6B

are perspective views showing a construction of a scanner cartridge upside down which can be mounted in the printer of one embodiment of the present invention instead of the print head cartridge of

FIG. 3

;

FIG. 7

is a block diagram schematically showing the overall configuration of an electric circuitry of the printer according to one embodiment of the present invention;

FIG. 8

is a diagram showing the relation between

FIGS. 8A and 8B

,

FIGS. 8A and 8B

being block diagrams representing an example inner configuration of a main printed circuit board (PCB) in the electric circuitry of

FIG. 7

;

FIG. 9

is a diagram showing the relation between

FIGS. 9A and 9B

,

FIGS. 9A and 9B

being block diagrams representing an example inner configuration of an application specific integrated circuit (ASIC) in the main PCB of

FIGS. 8A and 8B

;

FIG. 10

is a flow chart showing an example of operation of the printer as one embodiment of the present invention;

FIG. 11

is a perspective view showing a detailed construction of a print element substrate shown in

FIG. 5

;

FIG. 12

is a cross section showing a film structure of a print head substrate according to the one embodiment of the invention;

FIG. 13

is a cross section showing a ball bump formed on an electrode pad in the substrate shown in

FIG. 12

;

FIG. 14

is an explanatory diagram showing an example method of manufacturing the substrate shown in

FIG. 12

;

FIG. 15

is an explanatory diagram showing another example method of manufacturing the substrate shown in

FIG. 12

;

FIG. 16

is a plan view showing in particular an example of an electric wire in a conventional print head substrate;

FIG. 17

is a perspective view showing a head chip using the conventional substrate; and

FIG. 18

is a longitudinal cross section showing a film structure of the conventional head substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below in detail with reference to the drawings.

A general structure of an ink jet printer which uses a ink jet print head will be explained below by referring to

FIGS. 1-10

, before explaining a structure of an electrode pad in the ink jet print head according to one embodiment of the present invention.

A term “printing”, as used herein, refers to formation of images, patterns, or the like on a printing medium or processing of the printing medium whether meaningful information such as characters, graphics, or the like or meaningless information is to be formed or whether or not the information is embodied so as to be visually perceived by human beings.

A term “printing medium”, as used herein, refers not only to paper for use in general printing apparatuses but also to materials such as cloths, plastic films, metal plates, glass, ceramics, woods, and leathers which can receive inks.

Furthermore, a term “ink” (or “liquid”) should be broadly interpreted as in a definition of the above term “printing”, and refers to a liquid that is applied to the printing medium to form images, patterns, or the like, process the printing medium, or process the ink (for example, solidify or insolubilize a coloring material in the ink applied to the printing medium).

1. Apparatus Body

FIGS. 1 and 2

show an outline construction of a printer using an ink jet printing system. In

FIG. 1

, a housing of a printer body M

1000

of this embodiment has an enclosure member, including a lower case M

1001

, an upper case M

1002

, an access cover M

1003

and a discharge tray M

1004

, and a chassis M

3019

(see

FIG. 2

) accommodated in the enclosure member.

The chassis M

3019

is made of a plurality of plate-like metal members with a predetermined rigidity to form a skeleton of the printing apparatus and holds various printing operation mechanisms described later.

The lower case M

1001

forms roughly a lower half of the housing of the printer body M

1000

and the upper case M

1002

forms roughly an upper half of the printer body M

1000

. These upper and lower cases, when combined, form a hollow structure having an accommodation space therein to accommodate various mechanisms described later. The printer body M

1000

has an opening in its top portion and front portion.

The discharge tray M

1004

has one end portion thereof rotatably supported on the lower case M

1001

. The discharge tray M

1004

, when rotated, opens or closes an opening formed in the front portion of the lower case M

1001

. When the print operation is to be performed, the discharge tray M

1004

is rotated forwardly to open the opening so that printed sheets can be discharged and successively stacked. The discharge tray M

1004

accommodates two auxiliary trays M

1004

a

, M

1004

b

. These auxiliary trays can be drawn out forwardly as required to expand or reduce the paper support area in three steps.

The access cover M

1003

has one end portion thereof rotatably supported on the upper case M

1002

and opens or closes an opening formed in the upper surface of the upper case M

1002

. By opening the access cover M

1003

, a print head cartridge H

1000

or an ink tank H

1900

installed in the body can be replaced. When the access cover M

1003

is opened or closed, a projection formed at the back of the access cover, not shown here, pivots a cover open/close lever. Detecting the pivotal position of the lever as by a micro-switch and so on can determine whether the access cover is open or closed.

At the upper rear surface of the upper case M

1002

a power key E

0018

, a resume key E

0019

and an LED E

0020

are provided. When the power key E

0018

is pressed, the LED E

0020

lights up indicating to an operator that the apparatus is ready to print. The LED E

0020

has a variety of display functions, such as alerting the operator to printer troubles as by changing its blinking intervals and color. Further, a buzzer E

0021

(

FIG. 7

) may be sounded. When the trouble is eliminated, the resume key E

0019

is pressed to resume the printing.

2. Printing Operation Mechanism

Next, a printing operation mechanism installed and held in the printer body M

1000

according to this embodiment will be explained.

The printing operation mechanism in this embodiment comprises: an automatic sheet feed unit M

3022

to automatically feed a print sheet into the printer body; a sheet transport unit M

3029

to guide the print sheets, fed one at a time from the automatic sheet feed unit, to a predetermined print position and to guide the print sheet from the print position to a discharge unit M

3030

; a print unit to perform a desired printing on the print sheet carried to the print position; and an ejection performance recovery unit M

5000

to recover the ink ejection performance of the print unit.

Here, the print unit will be described. The print unit comprises a carriage M

4001

movably supported on a carriage shaft M

4021

and a print head cartridge H

1000

removably mounted on the carriage M

4001

.

2.1. Print Head Cartridge

First, the print head cartridge used in the print unit will be described with reference to

FIGS. 3

to

5

.

The print head cartridge H

1000

in this embodiment, as shown in

FIG. 3

, has an ink tank H

1900

containing inks and a print head H

1001

for ejecting ink supplied from the ink tank H

1900

out through nozzles according to print information. The print head H

1001

is of a so-called cartridge type in which it is removably mounted to the carriage M

4001

described later.

The ink tank for this print head cartridge H

1000

consists of separate ink tanks H

1900

of, for example, black, light cyan, light magenta, cyan, magenta and yellow to enable color printing with as high an image quality as photograph. As shown in

FIG. 4

, these individual ink tanks are removably mounted to the print head H

1001

.

Then, the print head H

1001

, as shown in the perspective view of

FIG. 5

, comprises a print element substrate H

1100

, a first plate H

1200

, an electric wiring board H

1300

, a second plate H

1400

, a tank holder H

1500

, a flow passage forming member H

1600

, a filter H

1700

and a seal rubber H

1800

.

The print element silicon substrate H

1100

has formed in one of its surfaces, by the film deposition technology, a plurality of print elements to produce energy for ejecting ink and electric wires, such as aluminum, for supplying electricity to individual print elements. A plurality of ink passages and a plurality of nozzles H

1100

T, both corresponding to the print elements, are also formed by the photolithography technology. In the back of the print element substrate H

1100

, there are formed ink supply ports for supplying ink to the plurality of ink passages. The print element substrate H

1100

is securely joined to the first plate H

1200

which is formed with ink supply ports H

1201

for supplying ink to the print element substrate H

1100

. The first plate H

1200

is securely joined with the second plate H

1400

having an opening. The second plate H

1400

holds the electric wiring board H

1300

to electrically connect the electric wiring board H

1300

with the print element substrate H

1100

. The electric wiring board H

1300

is to apply electric signals for ejecting ink to the print element substrate H

1100

, and has electric wires associated with the print element substrate H

1100

and external signal input terminals H

1301

situated at electric wires' ends for receiving electric signals from the printer body. The external signal input terminals H

1301

are positioned and fixed at the back of a tank holder H

1500

described later.

The tank holder H

1500

that removably holds the ink tank H

1900

is securely attached, as by ultrasonic fusing, with the flow passage forming member H

1600

to form an ink passage H

1501

from the ink tank H

1900

to the first plate H

1200

. At the ink tank side end of the ink passage H

1501

that engages with the ink tank H

1900

, a filter H

1700

is provided to prevent external dust from entering. A seal rubber H

1800

is provided at a portion where the filter H

1700

engages the ink tank H

1900

, to prevent evaporation of the ink from the engagement portion.

As described above, the tank holder unit, which includes the tank holder H

1500

, the flow passage forming member H

1600

, the filter H

1700

and the seal rubber H

1800

, and the print element unit, which includes the print element substrate H

1100

, the first plate H

1200

, the electric wiring board H

1300

and the second plate H

1400

, are combined as by adhesives to form the print head H

1001

.

2.2. Carriage

Next, by referring to

FIG. 2

, the carriage M

4001

carrying the print head cartridge H

1000

will be explained.

As shown in

FIG. 2

, the carriage M

4001

has a carriage cover M

4002

for guiding the print head H

1001

to a predetermined mounting position on the carriage M

4001

, and a head set lever M

4007

that engages and presses against the tank holder H

1500

of the print head H

1001

to set the print head H

1001

at a predetermined mounting position.

That is, the head set lever M

4007

is provided at the upper part of the carriage M

4001

so as to be pivotable about a head set lever shaft. There is a spring-loaded head set plate (not shown) at an engagement portion where the carriage M

4001

engages the print head H

1001

. With the spring force, the head set lever M

4007

presses against the print head H

1001

to mount it on the carriage M

4001

.

At another engagement portion of the carriage M

4001

with the print head H

1001

, there is provided a contact flexible printed cable (see FIG.

7

: simply referred to as a contact FPC hereinafter) E

0011

whose contact portion electrically contacts a contact portion (external signal input terminals) H

1301

provided in the print head H

1001

to transfer various information for printing and supply electricity to the print head H

1001

.

Between the contract portion of the contact FPC E

0011

and the carriage M

4001

there is an elastic member not shown, such as rubber. The elastic force of the elastic member and the pressing force of the head set lever spring combine to ensure a reliable contact between the contact portion of the contact FPC E

0011

and the carriage M

4001

. Further, the contact FPC E

0011

is connected to a carriage substrate E

0013

mounted at the back of the carriage M

4001

(see FIG.

7

).

3. Scanner

The printer of this embodiment can mount a scanner in the carriage M

4001

in place of the print head cartridge H

1000

and be used as a reading device.

The scanner moves together with the carriage M

4001

in the main scan direction, and reads an image on a document fed instead of the printing medium as the scanner moves in the main scan direction. Alternating the scanner reading operation in the main scan direction and the document feed in the subscan direction enables one page of document image information to be read.

FIGS. 6A and 6B

show the scanner M

6000

upside down to explain about its outline construction.

As shown in the figure, a scanner holder M

6001

is shaped like a box and contains an optical system and a processing circuit necessary for reading. A reading lens M

6006

is provided at a portion that faces the surface of a document when the scanner M

6000

is mounted on the carriage M

4001

. The lens M

6006

focuses light reflected from the document surface onto a reading unit inside the scanner to read the document image. An illumination lens M

6005

has a light source not shown inside the scanner. The light emitted from the light source is radiated onto the document through the lens M

6005

.

The scanner cover M

6003

secured to the bottom of the scanner holder M

6001

shields the interior of the scanner holder M

6001

from light. Louver-like grip portions are provided at the sides to improve the ease with which the scanner can be mounted to and dismounted from the carriage M

4001

. The external shape of the scanner holder M

6001

is almost similar to that of the print head H

1001

, and the scanner can be mounted to or dismounted from the carriage M

4001

in a manner similar to that of the print head H

1001

.

The scanner holder M

6001

accommodates a substrate having a reading circuit, and a scanner contact PCB M

6004

connected to this substrate is exposed outside. When the scanner M

6000

is mounted on the carriage M

4001

, the scanner contact PCB M

6004

contacts the contact FPC E

0011

of the carriage M

4001

to electrically connect the substrate to a control system on the printer body side through the carriage M

4001

.

4. Example Configuration of Printer Electric Circuit

Next, an electric circuit configuration in this embodiment of the invention will be explained.

FIG. 7

schematically shows the overall configuration of the electric circuit in this embodiment.

The electric circuit in this embodiment comprises mainly a carriage substrate (CRPCB) E

0013

, a main PCB (printed circuit board) E

0014

and a power supply unit E

0015

.

The power supply unit E

0015

is connected to the main PCB E

0014

to supply a variety of drive power.

The carriage substrate E

0013

is a printed circuit board unit mounted on the carriage M

4001

(

FIG. 2

) and functions as an interface for transferring signals to and from the print head through the contact FPC E

0011

. In addition, based on a pulse signal output from an encoder sensor E

0004

as the carriage M

4001

moves, the carriage substrate E

0013

detects a change in the positional relation between an encoder scale E

0005

and the encoder sensor E

0004

and sends its output signal to the main PCB E

0014

through a flexible flat cable (CRFFC) E

0012

.

Further, the main PCB E

0014

is a printed circuit board unit that controls the operation of various parts of the ink jet printing apparatus in this embodiment, and has I/O ports for a paper end sensor (PE sensor) E

0007

, an automatic sheet feeder (ASF) sensor E

0009

, a cover sensor E

0022

, a parallel interface (parallel I/F) E

0016

, a serial interface (Serial I/F) E

0017

, a resume key E

0019

, an LED E

0020

, a power key E

0018

and a buzzer E

0021

. The main PCB E

0014

is connected to and controls a motor (CR motor) E

0001

that constitutes a drive source for moving the carriage M

4001

in the main scan direction; a motor (LF motor) E

0002

that constitutes a drive source for transporting the printing medium; and a motor (PG motor) E

0003

that performs the functions of recovering the ejection performance of the print head and feeding the printing medium. The main PCB E

0014

also has connection interfaces with an ink empty sensor E

0006

, a gap sensor E

0008

, a PG sensor E

0010

, the CRFFC E

0012

and the power supply unit E

0015

.

FIG. 8

is a diagram showing the relation between

FIGS. 8A and 8B

, and

FIGS. 8A and 8B

are block diagrams showing an inner configuration of the main PCB E

0014

.

Reference number E

1001

represents a CPU, which has a clock generator (CG) E

1002

connected to an oscillation circuit E

1005

to generate a system clock based on an output signal E

1019

of the oscillation circuit E

1005

. The CPU E

1001

is connected to an ASIC (application specific integrated circuit) and a ROM E

1004

through a control bus E

1014

. According to a program stored in the ROM E

1004

, the CPU E

1001

controls the ASIC E

1006

, checks the status of an input signal E

1017

from the power key, an input signal E

1016

from the resume key, a cover detection signal E

1042

and a head detection signal (HSENS) E

1013

, drives the buzzer E

0021

according to a buzzer signal (BUZ) E

1018

, and checks the status of an ink empty detection signal (INKS) E

1011

connected to a built-in A/D converter E

1003

and of a temperature detection signal (TH) E

1012

from a thermistor. The CPU E

1001

also performs various other logic operations and makes conditional decisions to control the operation of the ink jet printing apparatus.

The head detection signal E

1013

is a head mount detection signal entered from the print head cartridge H

1000

through the flexible flat cable E

0012

, the carriage substrate E

0013

and the contact FPC E

0011

. The ink empty detection signal E

1011

is an analog signal output from the ink empty sensor E

0006

. The temperature detection signal E

1012

is an analog signal from the thermistor (not shown) provided on the carriage substrate E

0013

.

Designated E

1008

is a CR motor driver that uses a motor power supply (VM) E

1040

to generate a CR motor drive signal E

1037

according to a CR motor control signal E

1036

from the ASIC E

1006

to drive the CR motor E

0001

. E

1009

designates an LF/PG motor driver which uses the motor power supply E

1040

to generate an LF motor drive signal E

1035

according to a pulse motor control signal (PM control signal) E

1033

from the ASIC E

1006

to drive the LF motor. The LF/PG motor driver E

1009

also generates a PG motor drive signal E

1034

to drive the PG motor.

E

1010

is a power supply control circuit which controls the supply of electricity to respective sensors with light emitting elements according to a power supply control signal E

1024

from the ASIC E

1006

. The parallel I/F E

0016

transfers a parallel I/F signal E

1030

from the ASIC E

1006

to a parallel I/F cable E

1031

connected to external circuits and also transfers a signal of the parallel I/F cable E

1031

to the ASIC E

1006

. The serial I/F E

0017

transfers a serial I/F signal E

1028

from the ASIC E

1006

to a serial I/F cable E

1029

connected to external circuits, and also transfers a signal from the serial I/F cable E

1029

to the ASIC E

1006

.

The power supply unit E

0015

provides a head power signal (VH) E

1039

, a motor power signal (VM) E

1040

and a logic power signal (VDD) E

1041

. A head power ON signal (VHON) E

1022

and a motor power ON signal (VMON) E

1023

are sent from the ASIC E

1006

to the power supply unit E

0015

to perform the ON/OFF control of the head power signal E

1039

and the motor power signal E

1040

. The logic power signal (VDD) E

1041

supplied from the power supply unit E

0015

is voltage-converted as required and given to various parts inside or outside the main PCB E

0014

.

The head power signal E

1039

is smoothed by the main PCB E

0014

and then sent out to the flexible flat cable E

0011

to be used for driving the print head cartridge H

1000

. E

1007

denotes a reset circuit which detects a reduction in the logic power signal E

1041

and sends a reset signal (RESET) to the CPU E

1001

and the ASIC E

1006

to initialize them.

The ASIC E

1006

is a single-chip semiconductor integrated circuit and is controlled by the CPU E

1001

through the control bus E

1014

to output the CR motor control signal E

1036

, the PM control signal E

1033

, the power supply control signal E

1024

, the head power ON signal E

1022

and the motor power ON signal E

1023

. It also transfers signals to and from the parallel interface E

0016

and the serial interface E

0017

. In addition, the ASIC E

1006

detects the status of a PE detection signal (PES) E

1025

from the PE sensor E

0007

, an ASF detection signal (ASFS) E

1026

from the ASF sensor E

0009

, a gap detection signal (GAPS) E

1027

from the GAP sensor E

0008

for detecting a gap between the print head and the printing medium, and a PG detection signal (PGS) E

1032

from the PE sensor E

0007

, and sends data representing the statuses of these signals to the CPU E

1001

through the control bus E

1014

. Based on the data received, the CPU E

1001

controls the operation of an LED drive signal E

1038

to turn on or off the LED E

0020

.

Further, the ASIC E

1006

checks the status of an encoder signal (ENC) E

1020

, generates a timing signal, interfaces with the print head cartridge H

1000

and controls the print operation by a head control signal E

1021

. The encoder signal (ENC) E

1020

is an output signal of the CR encoder sensor E

0004

received through the flexible flat cable E

0012

. The head control signal E

1021

is sent to the print head H

1001

through the flexible flat cable E

0012

, carriage substrate E

0013

and contact FPC E

0011

.

FIG. 9

is a diagram showing the relation between

FIGS. 9A and 9B

, and

FIGS. 9A and 9B

are block diagrams showing an example internal configuration of the ASIC E

1006

.

In these figures, only the flow of data, such as print data and motor control data, associated with the control of the head and various mechanical components is shown between each block, and control signals and clock associated with the read/write operation of the registers incorporated in each block and control signals associated with the DMA control are omitted to simplify the drawing.

In the figures, reference number E

2002

represents a PLL controller which, based on a clock signal (CLK) E

2031

and a PLL control signal (PLLON) E

2033

output from the CPU E

1001

, generates a clock (not shown) to be supplied to the most part of the ASIC E

1006

.

Denoted E

2001

is a CPU interface (CPU I/F) E

2001

, which controls the read/write operation of register in each block, supplies a clock to some blocks and accepts an interrupt signal (none of these operations are shown) according to a reset signal E

1015

, a software reset signal (PDWN) E

2032

and a clock signal (CLK) E

2031

output from the CPU E

1001

, and control signals from the control bus E

1014

. The CPU I/F E

2001

then outputs an interrupt signal (INT) E

2034

to the CPU E

1001

to inform it of the occurrence of an interrupt within the ASIC E

1006

.

E

2005

denotes a DRAM which has various areas for storing print data, such as a reception buffer E

2010

, a work buffer E

2011

, a print buffer E

2014

and a development data buffer E

2016

. The DRAM E

2005

also has a motor control buffer E

2023

for motor control and, as buffers used instead of the above print data buffers during the scanner operation mode, a scanner input buffer E

2024

, a scanner data buffer E

2026

and an output buffer E

2028

.

The DRAM E

2005

is also used as a work area by the CPU E

1001

for its own operation. Designated E

2004

is a DRAM control unit E

2004

which performs read/write operations on the DRAM E

2005

by switching between the DRAM access from the CPU E

1001

through the control bus and the DRAM access from a DMA control unit E

2003

described later.

The DMA control unit E

2003

accepts request signals (not shown) from various blocks and outputs address signals and control signals (not shown) and, in the case of write operation, write data E

2038

, E

2041

, E

2044

, E

2053

, E

2055

, E

2057

etc. to the DRAM control unit to make DRAM accesses. In the case of read operation, the DMA control unit E

2003

transfers the read data E

2040

, E

2043

, E

2045

, E

2051

, E

2054

, E

2056

, E

2058

, E

2059

from the DRAM control unit E

2004

to the requesting blocks.

Denoted E

2006

is a IEEE 1284 I/F which functions as a bi-directional communication interface with external host devices, not shown, through the parallel I/F E

0016

and is controlled by the CPU E

1001

via CPU I/F E

2001

. During the printing operation, the IEEE 1284 I/F E

2006

transfers the receive data (PIF receive data E

2036

) from the parallel I/F E

0016

to a reception control unit E

2008

by the DMA processing. During the scanner reading operation, the 1284 I/F E

2006

sends the data (1284 transmit data (RDPIF) E

2059

) stored in the output buffer E

2028

in the DRAM E

2005

to the parallel I/F E

0016

by the DMA processing.

Designated E

2007

is a universal serial bus (USB) I/F which offers a bi-directional communication interface with external host devices, not shown, through the serial I/F E

0017

and is controlled by the CPU E

1001

through the CPU I/F E

2001

. During the printing operation, the universal serial bus (USB) I/F E

2007

transfers received data (USB receive data E

2037

) from the serial I/F E

0017

to the reception control unit E

2008

by the DMA processing. During the scanner reading, the universal serial bus (USB) I/F E

2007

sends data (USB transmit data (RDUSB) E

2058

) stored in the output buffer E

2028

in the DRAM E

2005

to the serial I/F E

0017

by the DMA processing. The reception control unit E

2008

writes data (WDIF E

2038

) received from the 1284 I/F E

2006

or universal serial bus (USB) I/F E

2007

, whichever is selected, into a reception buffer write address managed by a reception buffer control unit E

2039

.

Designated E

2009

is a compression/decompression DMA controller which is controlled by the CPU E

1001

through the CPU I/F E

2001

to read received data (raster data) stored in a reception buffer E

2010

from a reception buffer read address managed by the reception buffer control unit E

2039

, compress or decompress the data (RDWK) E

2040

according to a specified mode, and write the data as a print code string (WDWK) E

2041

into the work buffer area.

Designated E

2013

is a print buffer transfer DMA controller which is controlled by the CPU E

1001

through the CPU I/F E

2001

to read print codes (RDWP) E

2043

on the work buffer E

2011

and rearrange the print codes onto addresses on the print buffer E

2014

that match the sequence of data transfer to the print head cartridge H

1000

before transferring the codes (WDWP E

2044

). Reference number E

2012

denotes a work area DMA controller which is controlled by the CPU E

1001

through the CPU I/F E

2001

to repetitively write specified work fill data (WDWF) E

2042

into the area of the work buffer whose data transfer by the print buffer transfer DMA controller E

2013

has been completed.

Designated E

2015

is a print data development DMA controller E

2015

, which is controlled by the CPU E

1001

through the CPU I/F E

2001

. Triggered by a data development timing signal E

2050

from a head control unit E

2018

, the print data development DMA controller E

2015

reads the print code that was rearranged and written into the print buffer and the development data written into the development data buffer E

2016

and writes developed print data (RDHDG) E

2045

into the column buffer E

2017

as column buffer write data (WDHDG) E

2047

. The column buffer E

2017

is an SRAM that temporarily stores the transfer data (developed print data) to be sent to the print head cartridge H

1000

, and is shared and managed by both the print data development DMA CONTROLLER and the head control unit through a handshake signal (not shown).

Designated E

2018

is a head control unit E

2018

which is controlled by the CPU E

1001

through the CPU I/F E

2001

to interface with the print head cartridge H

1000

or the scanner through the head control signal. It also outputs a data development timing signal E

2050

to the print data development DMA controller according to a head drive timing signal E

2049

from the encoder signal processing unit E

2019

.

During the printing operation, the head control unit E

2018

, when it receives the head drive timing signal E

2049

, reads developed print data (RDHD) E

2048

from the column buffer and outputs the data to the print head cartridge H

1000

as the head control signal E

1021

.

In the scanner reading mode, the head control unit E

2018

DMA-transfers the input data (WDHD) E

2053

received as the head control signal E

1021

to the scanner input buffer E

2024

on the DRAM E

2005

. Designated E

2025

is a scanner data processing DMA controller E

2025

which is controlled by the CPU E

1001

through the CPU I/F E

2001

to read input buffer read data (RDAV) E

2054

stored in the scanner input buffer E

2024

and writes the averaged data (WDAV) E

2055

into the scanner data buffer E

2026

on the DRAM E

2005

.

Designated E

2027

is a scanner data compression DMA controller which is controlled by the CPU E

1001

through the CPU I/F E

2001

to read processed data (RDYC) E

2056

on the scanner data buffer E

2026

, perform data compression, and write the compressed data (WDYC) E

2057

into the output buffer E

2028

for transfer.

Designated E

2019

is an encoder signal processing unit which, when it receives an encoder signal (ENC), outputs the head drive timing signal E

2049

according to a mode determined by the CPU E

1001

. The encoder signal processing unit E

2019

also stores in a register information on the position and speed of the carriage M

4001

obtained from the encoder signal E

1020

and presents it to the CPU E

1001

. Based on this information, the CPU E

1001

determines various parameters for the CR motor E

0001

. Designated E

2020

is a CR motor control unit which is controlled by the CPU E

1001

through the CPU I/F E

2001

to output the CR motor control signal E

1036

.

Denoted E

2022

is a sensor signal processing unit which receives detection signals E

1032

, E

1025

, E

1026

and E

1027

output from the PG sensor E

0010

, the PE sensor E

0007

, the ASF sensor E

0009

and the gap sensor E

0008

, respectively, and transfers these sensor information to the CPU E

1001

according to the mode determined by the CPU E

1001

. The sensor signal processing unit E

2022

also outputs a sensor detection signal E

2052

to a DMA controller E

2021

for controlling LF/PG motor.

The DMA controller E

2021

for controlling LF/PG motor is controlled by the CPU E

1001

through the CPU I/F E

2001

to read a pulse motor drive table (RDPM) E

2051

from the motor control buffer E

2023

on the DRAM E

2005

and output a pulse motor control signal E

1033

. Depending on the operation mode, the controller outputs the pulse motor control signal E

1033

upon reception of the sensor detection signal as a control trigger.

Designated E

2030

is an LED control unit which is controlled by the CPU E

1001

through the CPU I/F E

2001

to output an LED drive signal E

1038

. Further, designated E

2029

is a port control unit which is controlled by the CPU E

1001

through the CPU I/F E

2001

to output the head power ON signal E

1022

, the motor power ON signal E

1023

and the power supply control signal E

1024

.

5. Operation of Printer

Next, the operation of the ink jet printing apparatus in this embodiment of the invention with the above configuration will be explained by referring to the flow chart of FIG.

10

.

When the printer body M

1000

is connected to an AC power supply, a first initialization is performed at step S

1

. In this initialization process, the electric circuit system including the ROM and RAM in the apparatus is checked to confirm that the apparatus is electrically operable.

Next, step S

2

checks if the power key E

0018

on the upper case M

1002

of the printer body M

1000

is turned on. When it is decided that the power key E

0018

is pressed, the processing moves to the next step S

3

where a second initialization is performed.

In this second initialization, a check is made of various drive mechanisms and the print head of this apparatus. That is, when various motors are initialized and head information is read, it is checked whether the apparatus is normally operable.

Next, steps S

4

waits for an event. That is, this step monitors a demand event from the external I/F, a panel key event from the user operation and an internal control event and, when any of these events occurs, executes the corresponding processing.

When, for example, step S

4

receives a print command event from the external I/F, the processing moves to step S

5

. When a power key event from the user operation occurs at step S

4

, the processing moves to step S

10

. If another event occurs, the processing moves to step S

11

.

Step S

5

analyzes the print command from the external I/F, checks a specified paper kind, paper size, print quality, paper feeding method and others, and stores data representing the check result into the DRAM E

2005

of the apparatus before proceeding to step S

6

.

Next, step S

6

starts feeding the paper according to the paper feeding method specified by the step S

5

until the paper is situated at the print start position. The processing moves to step S

7

.

At step S

7

the printing operation is performed. In this printing operation, the print data sent from the external I/F is stored temporarily in the print buffer. Then, the CR motor E

0001

is started to move the carriage M

4001

in the main-scanning direction. At the same time, the print data stored in the print buffer E

2014

is transferred to the print head H

1001

to print one line. When one line of the print data has been printed, the LF motor E

0002

is driven to rotate the LF roller M

3001

to transport the paper in the sub-scanning direction. After this, the above operation is executed repetitively until one page of the print data from the external I/F is completely printed, at which time the processing moves to step S

8

.

At step S

8

, the LF motor E

0002

is driven to rotate the paper discharge roller M

2003

to feed the paper until it is decided that the paper is completely fed out of the apparatus, at which time the paper is completely discharged onto the paper discharge tray M

1004

a.

Next at step S

9

, it is checked whether all the pages that need to be printed have been printed and if there are pages that remain to be printed, the processing returns to step S

5

and the steps S

5

to S

9

are repeated. When all the pages that need to be printed have been printed, the print operation is ended and the processing moves to step S

4

waiting for the next event.

Step S

10

performs the printing termination processing to stop the operation of the apparatus. That is, to turn off various motors and print head, this step renders the apparatus ready to be cut off from power supply and then turns off power, before moving to step S

4

waiting for the next event.

Step S

11

performs other event processing. For example, this step performs processing corresponding to the ejection performance recovery command from various panel keys or external I/F and the ejection performance recovery event that occurs internally. After the recovery processing is finished, the printer operation moves to step S

4

waiting for the next event.

A form of application where the present invention can effectively be implemented is the ink jet print head in which thermal energy generated by an electrothermal transducer is used to cause film boiling in a liquid to form a bubble.

(First Embodiment)

Some embodiments of the structure of the electrode pad in the print head substrate used in the ink jet printer described above will be explained in the following.

FIG. 11

is a perspective view showing a detailed structure, partly cut away, of the print element substrate (the head chip) H

1100

explained in FIG.

5

. Although a total of six kinds of ink are ejected from the associated columns of ink ejection ports in the head chip H

1100

, the figure shows only two columns of ink ejection ports, each two columns matching a different kind of ink.

The head chip H

1100

is made by forming a variety of films described above on a substrate

11

as a base, which is formed by for example a silicon (Si) of 0.5-1 mm thickness, and then providing a nozzle forming member including ink ejection ports

17

or the like.

To describe in more detail, the base

11

is formed with an ink supply passage

12

shaped like a long groove passing through the base. On both sides of the ink supply passage

12

two columns of heaters

101

are arranged in a zigzag pattern. In addition to these heaters

101

, a second electric wire of aluminum (not shown) is formed by the film deposition technology to supply a drive power to the heaters

101

. Further, the base is also provided with electrode portions

14

for electric connection with the printer body side to supply an electric power to the heaters and a drive signal to the drive IC. The electrode portions

14

are each formed with a plurality of electrode pads

110

, each of which is joined with a ball bump

15

of, for example, gold in a manner described later.

The ink supply passage

12

formed in the substrate is formed by performing anisotropic etching taking advantage of a crystal orientation of the silicon base

11

. When the silicon base has crystal orientations of the <100> in a wafer plane and of the <111> in a thickness direction, an alkaline (KOH, TMAH, hydrazine, etc.) anisotropic etching is performed at an angle of about 55 degrees. This can form the ink supply passage

12

passing through the base

11

.

The substrate is further provided with a nozzle forming member. More specifically, the nozzle forming member is formed with ink ejection ports

17

at locations corresponding to their associated heaters

101

. The ink ejection ports

17

assigned to each kind of ink are arranged in a column

18

, with each ejection port line of the column

18

having an ejection port density of 600 dpi, and the two ejection port lines are arranged zigzag pattern to provide an overall density of 1200 dpi. In forming process of the nozzle forming member, ink passage walls

16

defining ink passages corresponding to the associated heaters

101

are formed by the photolithography as with the ink ejection ports.

In the head chip H

1100

of the above structure, the ink supplied to each ink passage through the ink supply passage

12

produces a bubble as the heater

101

generates heat in response to the drive signal, and the pressure of this bubble ejects the ink.

FIG. 12

is a cross section showing the film structure of the substrate making the head chip H

1100

according to the embodiment above and is a similar section to

FIG. 18

showing a conventional example.

What differs from the conventional film structure shown in

FIG. 18

is the structure of the electrode pads

110

. That is, in this embodiment a surface conductive film to be joined with the ball electrodes is selected to be the first electric wire film

202

, which represents the electric wire formed at lower position in the substrate.

FIG. 13

shows the first electric wire film

202

joined with the ball bump

15

.

The first electric wire film

202

joined with the ball bump

15

forms a common electrode of the matrix wires, as described earlier, and inherently has a relatively large thickness. That is, this wire functions as the common electrode for supplying an electric power or for grounding and has a relatively large film thickness of more than 4,000 Å or preferably about 10,000 Å and a large width pattern to reduce the voltage drop. Even when the protective film is made thin for efficient heat transfer to the ink as described above, because the first electric wire film

202

is under the heater film

204

, there is no need to reduce the thickness of the first electric wire film

202

to secure the satisfactory step coverage. This allows the surface conductive film to have an enough thickness to join the ball bump by ultrasonic bonding, thereby assuring a satisfactory joining.

In this embodiment, the gold ball bump is bonded to the electrode pads

110

by a method applying the wire bonding. Then, the ball bump is loaded to flatten their top portions to facilitate the TAB bonding.

A study conducted by the inventor of the present invention has found that the loss of bump occurs when the first electric wire film made of aluminum or aluminum alloy that forms the surface layer of the electrode pad is 4,000 Å or less in thickness. For example, when the thickness of the surface layer of the pad is set at 2,000 Å equal to the thickness of the second electric wire film which was reduced as part of the process of reducing the thickness of the protective film of the heater portion

101

, the bump loss occurs with a probability of about 1% to 50%. Even 1% of bump loss necessitates the inspection of the entire head chips, causing a significant burden to the production process. On the other hand, the use of the film structure of the electrode pad according to this embodiment enables satisfactory bonding and forming of the ball bump with almost no cost increase.

FIG. 14

shows a process of manufacturing the print head according to this embodiment in which the surface layer of the electrode pad

110

is formed by the first electric wire film

202

. In the figure, the state of the films of the electrode pad portion at each step is schematically shown to the right. It should also be appreciated that the film structure in the entire area of the substrate including the heater portions and through-hole portions is formed simultaneously by some of the following steps.

In step S

1

, a SiN film (first interlayer insulating film

201

) is deposited to a thickness of 14,000 Å, applied with a resist and exposed by a chemical vapor deposition (CVD) device and then patterned by a dry etching device. Next at step S

2

, an aluminum or aluminum alloy film (first electric wire film

202

) is deposited to a thickness of 10,000 Å, applied with a resist and exposed by a sputtering device and then patterned by a dry etching device. At step S

3

, a SiO film (second interlayer insulating film

203

) is deposited to 14,000 Å, applied with a resist and exposed by the CVD device and patterned by a wet etching device. Further at step S

4

, a TaN film (heater film

204

) is deposited to 400 Å by the sputtering device. Then at step S

5

, an aluminum film (second electric wire film

205

) is deposited to a thickness of 2,000 Å by the sputtering device. The process up to this point is performed in the same way as in the heater portion.

At the next step S

6

, an aluminum film (second electric wire film

205

) of 2,000 Å thick and a TaN film (heater film

204

) of 400 Å thick are applied with a resist and exposed and then simultaneously patterned by a dry etching device. This simultaneous patterning removes the second electric wire film

205

and the heater film

204

from the electrode pads

110

. In this embodiment, the use of the simultaneous patterning minimizes a possible increase in the number of steps which may otherwise result when the lower of the two electric wire films, or the first electric wire film

202

, is used as the surface conductive film.

Step S

7

patterns and forms the heater portions

101

by applying a resist to and exposing the aluminum film (second electric wire film

205

) of 2,000 Å thick and then removing the aluminum film with a wet etching device. At this time, the electrode pad portions

110

remain as formed by the step S

6

.

Next step S

8

deposits a SiN film (protective film

206

) to a thickness of 3,000 Å, applies a resist to and exposes the film by the CVD device and patterns the film by a dry etching device.

Next, at step S

9

, a Ta film (wear resistant film

207

) is deposited to a thickness of 2,300 Å, applied with a resist and exposed at other than the electrode pad portions, and then patterned by a dry etching device. At this time, the electrode pad portion

110

remain as formed by the step S

8

.

Then, at final step S

10

, a SiO film (second interlayer insulating film

203

) is removed to a thickness of 14,000 Å, by being applied with a resist and exposed and by a dry etching device to form the electrode pad.

(Second Embodiment)

The electrode pad structure according to the second embodiment of the invention will be described according to the film making process.

FIG. 15

shows the process of manufacturing the print head according to the second embodiment. What differs from the manufacturing process according to the first embodiment shown in

FIG. 14

is that at step S

3

the SiO film (second interlayer insulating film

203

) in the electrode pad portions

110

is formed with a window of 14,000 Å deep. Another differing point is that the TaN (heater film

204

) and the second electric wire film

205

formed over the second interlayer insulating film

203

are removed by step S

5

.

This eliminates the need of step S

10

shown in FIG.

14

. However, the first electric wire film

202

in the electrode pad portion is etched away to some extent by the etching at step S

3

and the subsequent steps. Thus the first electric wire film

202

must be made thicker than shown in the step of FIG.

14

. The amount by which the first electric wire film

202

is made thicker, of course, varies depending on the amount of overetch caused by the etching step.

As can be seen from the foregoing, according to the embodiments of this invention, because the exposed part of the first wire electrode underlying the heater forms the electrode pad, a film which does not need to be reduced in thickness to secure the heater protective film's step coverage even when the protective film is made thinner can be used for the electrode pad. Further, an inherently thick film can be used for the electrode pad. As a result, when the ball bump is joined by an ultrasonic bonding process bonding, the bonding strength can be increased.

As a result, the bonding of ball bump can be stabilized, preventing the ball bump from getting disconnected. This eliminates the head chip inspection step and therefore reduces the number of inspection workers, lowering the cost. Further, in a thin film structure that can meet the conditions for further energy consumption reductions required of the ink jet print head, this invention can stably bond the ball bumps.

The present invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspect, and it is the intention, therefore, in the apparent claims to cover all such changes and modifications as fall within the true spirit of the invention.

Number	Name	Date	Kind
4695853	Hackleman et al.	Sep 1987	A
4916464	Ito et al.	Apr 1990	A
5227812	Watanabe et al.	Jul 1993	A

Substrate for ink jet print head, ink jet print head and manufacturing methods therefor

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US Referenced Citations (3)