EP1473161A1

EP1473161A1 - Assembling structure of printhead

Info

Publication number: EP1473161A1
Application number: EP04009584A
Authority: EP
Inventors: Fu-San Lin; Ying-Lun Chang; Rong-Ho Yu
Original assignee: Microjet Technology Co Ltd
Current assignee: Microjet Technology Co Ltd
Priority date: 2003-04-22
Filing date: 2004-04-22
Publication date: 2004-11-03
Anticipated expiration: 2024-04-22
Also published as: ATE461044T1; EP1473161B1; DE602004026002D1; BRPI0401976B1; BRPI0401976A

Abstract

An assembling structure of a printhead includes a carrying seat (61), a rectangular heater chip (51), a barrier layer (52), a nozzle plate (53) and a flexible circuit board (7). The carrying seat (61) includes a first support portion (611) and a second support portion (612). The heater chip (51) is mounted on the first support portion (611) of the carrying seat (61). The first and the second side walls (515, 516) of the heater chip (51) and the first and the second inner walls (6121, 6122) of the second support portion (612) define a first and a second ink passages (621, 622), respectively. The bilateral sides of the heater chip (51) are uncovered by the barrier layer (52). The nozzle plate (53) is bonded onto the barrier layer (52) and has a plurality of nozzles (531) formed therein and corresponding to the ink chambers (521) of the barrier layer (52). The nozzle plate (53) having a width extended over the heater chip (51) and attached onto the second support portion (612) of the carrying seat (61) by an adhesive (63). The flexible circuit board (7) is provided on the print cartridge body (6) and has a window (70). The nozzle plate (53) is disposed in the window (70) such that the nozzle plate (53), the first support portion (611) and the second support portion (612) are not in contact with the flexible circuit board (7).

Description

FIELD OF THE INVENTION

The present invention relates to an assembling structure of a printhead, and more particularly to an assembling structure of a printhead having a reduced size and easily fabricated.

BACKGROUND OF THE INVENTION

With increasing development of personal computer, inkjet printers are widely used as peripheral devices of computers due to cost-effectiveness, low noise and good printing quality. In addition, the inkjet printers can be applied to print ink onto many kinds of media such as regular papers, specific inkjet papers, plastic films, etc.
The inkjet printers are typically classified into two types, i.e. thermal bubble inkjet printers and micro-piezoelectric inkjet printers. So far, thermal bubble inkjet printers are relatively popular. The thermal bubble inkjet printers are operated by rapidly heating a small volume of ink to cause the ink to vaporize and be ejected through one of a plurality of nozzles so as to print a dot of ink on a medium such as a paper.
Referring to Fig. 1, a conventional printhead is shown. The printhead comprises a heater chip 11, a barrier layer 12 and a nozzle plate 13. The heater chip 11 comprises a central ink slot 110, a plurality of heater resistors (not shown) surrounding the ink slot 110, and a plurality of bond pads 111 on the bilateral edges thereof along the longitudinal direction. The barrier layer 12 has a plurality of ink chambers 121 formed therein and defines ink channels (not shown) along with the heater chip 11. The nozzle plate 13 has a plurality of nozzles 131 formed therein and corresponding to the ink chambers 121 of the barrier layer 12. As such, ink can flow into the ink channels and the ink chambers 121, and be ejected from an associated nozzle 131 by means of an associated heater resistor.
The process of assembling the above printhead onto a print cartridge body will be described in more details with reference to the Fig. 2. Firstly, the nozzle plate 13 is precisely aligned with the heater chip 11 so as to form an IC assembly. Then, the nozzle plate 13 is bonded directly to conductive traces formed on a flexible tape automated bonding (TAB) circuit (not shown). Then, an adhesive is applied onto a bottom surface 21 of the print cartridge body 2, and thus the IC assembly is secured directly to the bottom surface of the print cartridge body 2. After the printhead is assembled onto the print cartridge body 2, the ink stored in the ink reservoir of the print cartridge body 2 is successively discharged through the bottom hole 22, the central ink slot 110 of the heater chip 11 and the ink channels and the ink chambers 121 of the barrier layer 12. By means of an associated heater resistor, the ink will be ejected from an associated nozzle 131 of the nozzle plate 13.
The above assembling structure has some disadvantages. For example, the strength of the heater chip 11 is relatively low due to the central slot 110. In addition, the elongated central slot 110 means that the size of the heater chip 11 is large. Furthermore, as can be seen in Fig. 3, since the bottom surface 21 is substantially flat, the area and the thickness of the adhesive layer 23 to be applied onto the bottom surface 21 should be large enough so as to offer a suitable sealing property.
Referring to Fig. 4, another process for assembling the printhead is shown. This process is performed by a tape automated bonding (TAB) technology. Firstly, conductive traces are formed on a surface of a flexible circuit board 30. Then, a nozzle plate is bonded to the flexible circuit board 30; and two parallel columns of nozzles 311 are formed in the flexible circuit board 30 by laser ablation. The heater chip is then positioned with respect to the back surface of the flexible circuit board 30 so as to align the heater resistors with the nozzles 311 formed in the flexible circuit board 30. As such, a TAB assembly is made. After an adhesive layer is applied onto the bottom surface of the print cartridge body 32, the printhead is secured to the bottom surface of the print cartridge body.
The TAB technology can increase the throughput of assembling the printhead. However, this TAB technology still has some drawbacks. For example, since the flexible circuit board is attached to the bottom surface of the print cartridge body along with the nozzle plate, the sealing property of the printhead is slightly reduced. In addition, both the alignment of the heater resistors with the nozzles 311 and the alignment of the bond pad and the conductive trace of the flexible circuit board should be precisely done. The fabrication cost is largely increased due to the complexity of double alignment procedures.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an assembling structure of a printhead having a reduced size and easily fabricated so as to increase yield of the product and overcome the drawback of the conventional TAB technology.
In accordance with a first aspect of the present invention, there is provided an assembling structure of a printhead. The assembling structure comprises a carrying seat, a rectangular heater chip, a barrier layer, a nozzle plate and a flexible circuit board. The carrying seat is formed on a print cartridge body, and comprises a first support portion and a second support portion. The second support portion comprises a first inner wall and a second inner wall. The rectangular heater chip is mounted on the first support portion of the carrying seat and comprises a first side wall and a second side wall along the longitudinal direction of the heater chip. The first and the second side walls of the heater chip and the first and the second inner walls of the second support portion defme a first and a second ink passages, respectively. The barrier layer is formed on the heater chip such that bilateral sides of the heater chip are uncovered by the barrier layer. The barrier layer has a plurality of ink chambers formed therein. The nozzle plate is bonded onto the barrier layer and has a plurality of nozzles formed therein and corresponding to the ink chambers of the barrier layer. The nozzle plate has a width extended over the heater chip and attached onto the second support portion of the carrying seat by an adhesive so as to seal the first and second ink passages. The flexible circuit board is provided on the print cartridge body and has a window. The periphery of the window of the flexible circuit board is separated from the first and the second support portions. The nozzle plate is disposed in the window, the first and the second ink passages are sealed by the nozzle plate, and the first and the second support portions are not in contact with the flexible circuit board.
In an embodiment, a plurality of bond pads are provided on bilateral edges of the heater chip along the transverse direction thereof so as to make electric connection with corresponding conductive traces located proximate to the perimeter of the window of the flexible circuit board.
In an embodiment, the length of the nozzle plate is substantially the same as that of the heater chip, and the nozzle plate has two indentation structures corresponding to the bond pads such that the nozzle plate does not cover the bond pads on the heater chip, and the first support portion and the second support portion of the carrying seat are arranged at different levels so as to support the heater chip and the nozzle plate, respectively.
In an embodiment, the nozzle plate is H-shaped.
In an embodiment, the peripheral edges of the first support portion and the second support portion of the carrying seat are provided with depression regions for dispensing the adhesive.
In accordance with a second aspect of the present invention, there is provided an assembling structure of a printhead. The assembling structure comprises a carrying seat, a heater chip, a barrier layer, a nozzle plate and a flexible circuit board. The carrying seat is formed on a print cartridge body, and comprises a first support portion and a second support portion. The heater chip is mounted on the first support portion of the carrying seat. The barrier layer is formed on the heater chip. The nozzle plate is bonded onto the heater chip. The nozzle plate has a width extended over the heater chip and attached onto the second support portion of the carrying seat. The flexible circuit board is provided on the print cartridge body and has a window. The periphery of the window of the flexible circuit board is separated from the first and the second support portions. The nozzle plate is disposed in the window, the first and the second ink passages are sealed by the nozzle plate, and the first and the second support portions are not in contact with the flexible circuit board.
In accordance with a third aspect of the present invention, there is provided an assembling structure of a printhead. The assembling structure comprises a carrying seat, a heater chip, a barrier layer, a H-shaped nozzle plate and a flexible circuit board. The carrying seat is formed on a print cartridge body, and comprises a first support portion and a second support portion. The heater chip is mounted on the first support portion of the carrying seat to define a first and a second ink passages between the carrying seat and the heater chip. The barrier layer is formed on the heater chip. The H-shaped nozzle plate is bonded onto the barrier layer. The H-shaped nozzle plate is attached onto the second support portion of the carrying seat so as to seal the first and the second ink passages. The flexible circuit board is provided on the print cartridge body. The first and the second support portions are not in contact with the flexible circuit board.
The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an exploded view illustrating a conventional printhead;
Fig. 2 is an exploded view illustrating the printhead of Fig. 1 secured onto a bottom surface of a print cartridge body;
Fig. 3 is a schematic cross-section view of the printhead of Fig. 1 secured onto the bottom surface of a print cartridge body;
Fig. 4 is a perspective view illustrating a printhead assembled by a tape automated bonding (TAB) technology;
Fig. 5 is an exploded view illustrating a printhead according to a preferred embodiment of the present invention;
Fig. 6 is an exploded view illustrating the printhead of Fig. 5 secured onto a carrying seat of a print cartridge body;
Fig. 7 is an enlarged fragmentary view of the carrying seat of Fig. 6;
Fig. 8 is a schematic cross-section view of the printhead of Fig. 5 secured onto the carrying seat of a print cartridge body;
Fig. 9 schematically illustrates another preferred carrying seat;
Fig. 10 is a top view illustrating a flexible circuit board on the print cartridge body after the IC assembly is secured onto the carrying seat; and
Fig. 11 is an exploded view illustrating a printhead according to another preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to Fig. 5, an exploded view of a printhead according to a preferred embodiment of the present invention is shown. The printhead comprises a heater chip 51, a barrier layer 52 and a nozzle plate 53. The heater chip 51 is rectangular and has a plurality of bond pads 511 on the bilateral edges thereof along the transverse direction. The barrier layer 52 is in an I-shape, and formed on the heater chip 51 such that a first recess 513 and a second recess 514 are formed on the heater chip 51. The barrier layer 52 has a plurality of ink chambers 521 formed therein and defines ink channels (not shown) along with the heater chip 51. The heater chip 51 further comprises a plurality of heater resistors (not shown) corresponding to associated ink chambers 521. The nozzle plate 53 is in a H-shape and has a plurality of nozzles 531 formed therein and corresponding to the ink chambers 521 of the barrier layer 52. The nozzles 531 are manufactured by laser or other etching means, as are known to those in the art and are not to be redundantly described herein. The length of the nozzle plate 53 is substantially the same as that of the heater chip 51. The nozzle plate 53, however, has two indentation structures 532 and 533 corresponding to the bond pads 511. After the nozzle plate 53 is coupled to the heater chip 51 and forms an IC assembly 50, as shown in Fig. 6, the nozzle plate 53 does not cover the bond pads 511 on the heater chip 51.
The process of assembling the IC assembly 50 onto a print cartridge body will be described in more details with reference to the Figs. 6, 7 and 8. Firstly, a carrying seat 61 is directly formed on a bottom surface of the print cartridge body 6. The carrying seat 61 principally comprises a first support portion 611 and a second support portion 612. Then, an adhesive 63 is applied onto the first support portion 611 and the second support portion 612. The first support portion 611 and the second support portion 612 are arranged at different levels so as to support the heater chip 51 and the nozzle plate 53 of the IC assembly 50, respectively. For a purpose of enhancing sealing property, the IC assembly 50 is securely to the carrying seat 61 by an appropriate jig tool.
As shown in Figs. 6, 7 and 8, the heater chip 51 comprises a first side wall 515 and a second side wall 516 along the longitudinal direction. The second support portion 612 has a first inner wall 6121 and a second inner wall 6122, respectively. The first side wall 515 of the heater chip 51 and the first inner wall 6121 of the second support portion 612 define a first ink passage 621.
The second side wall 516 of the heater chip 51 and the second inner wall 6122 of the second support portion 612 define a second ink passage 622. The ink stored in the ink reservoir of the print cartridge body 6 is successively discharged through the bottom hole 62, the first and the second ink passages 621, 622, the first and the second recess 513, 514, and the ink channels and the ink chambers 521 of the barrier layer 52. By means of an associated heater resistor, the ink will be ejected from an associated nozzle of the nozzle plate 53.
Furthermore, referring to Fig. 9, the peripheral edges of the first support portions 611 and the second support portions 612 are provided with depression regions 613 for dispensing the adhesive 63. In stead, the peripheral edges of the first support portions 611 and the second support portions 612 can be provided with platforms having depression regions.
Referring to Fig. 10, a flexible circuit board 7 is provided on the print cartridge body (not shown) after the IC assembly is secured onto the carrying seat. The flexible circuit board 7 has a window 70 and a set of conductive traces 71 formed on the tape for conducting signals. The IC assembly is disposed in the window 70 of the flexible circuit board 7 so that the first and the second support portions 611, 612 are not in contact with the flexible circuit board 7. Portions of the set of conductive traces are located proximate to the perimeter of the window 70. As such, the bond pads 511 on the heater chip 51 are electrically connected to the corresponding conductive traces 71 on the tape 7.
A further embodiment of another printhead is illustrated in Fig. 11. In this embodiment, the heater chip 51 included therein is similar to those shown in Fig. 5, and needs not to be redundantly described herein. The nozzle plate 53 is in a rectangular shape. The heater chip 51 is longer than the nozzle plate 53 such that the nozzle plate 53 does not cover the bond pads 511 on the heater chip 51.
As will be apparent from the above description, the assembling structure of the printhead according to the present invention has some advantages when comparing with the prior art. Firstly, since the central ink slot of the conventional heater chip is replaced by the bilateral recesses of the present heater chip for passing ink therethrough, the strength of the heater chip of the present invention is increased and the size of the heater chip is largely reduced. Second, the area and the thickness of the adhesive layer is less because the adhesive layer is only applied onto the edges of the IC assembly, and thus the amount of the adhesive to be used is also reduced without impairing the sealing property. Third, since the nozzles of the nozzle plate are fabricated without bonding onto the flexible circuit board, the conventional problem of ink leakage occurring at the interface between the nozzle plate and the flexible circuit board can be minimized. Moreover, according to the present invention, the alignment of the heater resistors with the nozzles and the alignment of the bond pad and the conductive trace of the flexible tap are separately performed such that the product yield is largely enhanced because the allowable tolerance for assembling procedure is broadened.

Claims

An assembling structure of a printhead, characterized by comprising:

a carrying seat (61) formed on a print cartridge body (6), and comprising a first support portion (611) and a second support portion (612), said second support portion (612) comprising a first inner wall (6121) and a second inner wall (6122);

a rectangular heater chip (51) mounted on said first support portion (611) of said carrying seat (61) and comprising a first side wall (515) and a second side wall (516) along the longitudinal direction of said heater chip (51), said first and said second side walls (515, 516) of said heater chip (51) and said first and said second inner walls (6121, 6122) of said second support portion (612) defining a first and a second ink passages (621, 622), respectively;

a barrier layer (52) formed on said heater chip (51) such that bilateral sides of said heater chip (51) are uncovered by said barrier layer (52), said barrier layer (52) having a plurality of ink chambers (521) formed therein;

a nozzle plate (53) bonded onto said barrier layer (52) and having a plurality of nozzles (531) formed therein and corresponding to said ink chambers (521) of said barrier layer (52), said nozzle plate (53) having a width extended over said heater chip (51) and attached onto said second support portion (612) of said carrying seat (61) by an adhesive (63) so as to seal said first and said second ink passages (621, 622); and

a flexible circuit board (7) provided on said print cartridge body (6) and having a window (70), said nozzle plate (53) being disposed in said window (70) such that said nozzle plate (53), said first support portion (611) and said second support portion (612) are not in contact with said flexible circuit board (7).
The assembling structure according to claim 1 characterized in that a plurality of bond pads (511) are provided on bilateral edges of said heater chip (51) along the transverse direction thereof so as to make electric connection with corresponding conductive traces (71) located proximate to the perimeter of said window (70) of said flexible circuit board (7).
The assembling structure according to claim 2 characterized in that the length of said nozzle plate (53) is substantially the same as that of said heater chip (51), and said nozzle plate (53) has two indentation structures (532, 533) corresponding to said bond pads (511) such that said nozzle plate (53) does not cover said bond pads (511) on said heater chip (51), and said first support portion (611) and said second support portion (612) of said carrying seat (61) are arranged at different levels so as to support said heater chip (51) and the nozzle plate (53), respectively.
The assembling structure according to claim 3 characterized in that said nozzle plate (53) is H-shaped.
The assembling structure according to claim 1 characterized in that peripheral edges of said first support portion (611) and said second support portion (612) of said carrying seat (61) are provided with depression regions (613) for dispensing said adhesive (63).
An assembling structure of a printhead, characterized by comprising:

a carrying seat (61) formed on a print cartridge body (6), and comprising a first support portion (611) and a second support portion (612);

a heater chip (51) mounted on said first support portion (611) of said carrying seat (61);

a barrier layer (52) formed on said heater chip (51);

a nozzle plate (53) bonded onto said heater chip (51), said nozzle plate (53) having a width extended over said heater chip (51) and attached onto said second support portion (612) of said carrying seat (61); and

a flexible circuit board (7) provided on said print cartridge body (6) and having a window (70), said nozzle plate (53) being disposed in said window (70) such that said nozzle plate (53), said first support portion (611) and said second support portion (612) are not in contact with said flexible circuit board (7).
The assembling structure according to claim 6 characterized in that said heater chip (51) comprises a first side wall (515) and a second side wall (516) along the longitudinal direction thereof, said second support portion (612) comprises a first inner wall (6121) and a second inner wall (6122), wherein said first and said second side walls (515, 516) of said heater chip (51) and said first and said second inner walls (6121, 6122) of said second support portion (612) define a first and a second ink passages (621, 622), respectively.
The assembling structure according to claim 6 characterized in that the peripheral edges of said first support portion (611) and said second support portion (612) of said carrying seat (61) are provided with depression regions (613) for dispensing said adhesive (63).
The assembling structure according to claim 6 characterized in that said nozzle plate (53) is H-shaped.
An assembling structure of a printhead, characterized by comprising:

a carrying seat (61) formed on a print cartridge body (6), and comprising a first support portion (611) and a second support portion (612);

a heater chip (51) mounted on said first support portion (611) of said carrying seat (61) to define a first and a second ink passages (621, 622) between said carrying seat (61) and said heater chip (51);

a barrier layer (52) formed on said heater chip (51);

a H-shaped nozzle plate (53) bonded onto said barrier layer (52), said H-shaped nozzle plate (53) attached onto said second support portion (612) of said carrying seat (61) so as to seal said first and said second ink passages (621, 622); and

a flexible circuit board (7) provided on said print cartridge body (6) and being not in contact with said first support portion (611) and said second support portion (612).