Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-06-02
2003-06-24
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S149000, C361S769000
Reexamination Certificate
active
06583845
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims benefit of Korean patent application number P2000-08667, filed Feb. 23, 2000, which is hereby incorporated by reference for all purposes as if fully set forth herein.
FIELD OF THE INVENTION
This invention relates to a liquid crystal display having a tape carrier package including a mounted integrated circuit, and more particularly to a tape carrier package with dummy pads that are capable of fortifying a bonding force in bonding the tape carrier package onto a liquid crystal panel. Also, the present invention is related to a method of fabricating a liquid crystal display with dummy pads that are capable of fortifying a bonding force between the tape carrier package and the liquid crystal panel.
DESCRIPTION OF THE RELATED ART
Generally, an active matrix liquid crystal display uses thin film transistors (TFTs) as switching devices to display a natural-looking moving picture. Since such a liquid crystal display can be made into a smaller-size device than a cathode ray tube, it is commercially viable for use as a monitor such as a portable television, lap-top personal computer or other consumer device.
The active matrix liquid crystal display displays a picture corresponding to video signals such as television signals on a pixel (or picture element) matrix having pixels arranged at each intersection between gate lines and data lines. Each pixel includes a liquid crystal cell for controlling a transmitted light quantity in accordance with a voltage level of a data signal from a data line. A TFT (thin film transistor) is installed at an intersection between a gate line and a data line to switch a data signal to be transferred to the liquid crystal cell in response to a scanning signal (i.e., a gate pulse) from the gate line.
Such a liquid crystal display requires a number of integrated circuits (ICs) connected to the data lines and the gate lines to apply data signals and scanning signals to the data lines and the gate lines, respectively. The ICs are installed between the print wiring board (PWB) and the liquid crystal panel to apply signals supplied from the PWB to the data lines and the gate lines. IC mounting methods include chip on board, hereinafter referred to as “COB”, tape automated bonding, hereinafter referred to as “TAB”, and chip on glass, hereinafter referred to as “COG”. (Other methods are also possible.) The COB system is ainly used for a monochromatic liquid crystal display having a pixel pitch of more than 300 &mgr;m. As shown in
FIG. 1
, in this COB system, ICs
8
are mounted on a PWB
6
and a heat-seal connector
10
connects the PWB
6
and a glass substrate
3
in a liquid crystal panel
2
. In this case, a back light unit
4
used as a light source is provided between the liquid crystal panel
2
and the PWB
6
. As shown in
FIG. 2
, in the TAB system, ICs
14
are mounted on a tape carrier package (TCP)
12
. The TCP
12
is connected between the PWB
6
and the liquid crystal panel
3
. As shown in
FIG. 3
, in the COG system, an IC chip
20
is directly mounted on a glass substrate
17
in a liquid crystal panel
16
.
The above mentioned TAB IC mounting method has been widely employed because it can widen an effective area of the panel and has a relatively simple mounting process.
As shown in
FIG. 4
, the TCP
12
employed in the TAB system includes a base film
22
on which is mounted an IC
14
. The base film
22
is also provided with input and output pads
24
and
26
connected to input and output pins of the ICs
14
. The input and output pads
24
and
26
have a two-layer structure in which copper(Cu) is plated with tin(Sn) for preventing an oxidation. Line widths of the input pads
24
are set to be larger than those of the output pads
26
. As shown in
FIG. 5
, the input pads
24
of the base film
22
are connected, via an anisotropic conductive film (ACF)
30
, to pads
28
on the PWB
6
. The output pads
26
are also connected via the ACF
30
to pads
28
on the liquid crystal panel
2
.
Recently, in order to fortify a bonding force between the liquid crystal panel and the TCP
42
, separate dummy pads
50
and
52
have been provided at a liquid crystal panel
44
and a TCP
42
as shown in FIG.
6
. The dummy pads
50
and
52
function to increase a bonding force between the TCP
42
and the liquid crystal panel
44
by widening a bonded area without being connected to a signal wiring. The dummy pads
50
and
52
are bonded to each other with the ACF
30
therebetween upon bonding the output pads
46
of the TCP
42
to the gate/data pads
48
of the liquid crystal panel
44
. Line widths of the dummy pads
52
and
54
are set to be equal to those of the output pads
46
of the TCP
42
and the gate/data pads
48
of the liquid crystal panel
44
. Accordingly, the bonding forces of each dummy pad
50
and
52
are the same.
However, the TCP
42
and the liquid crystal panel
44
having the conventional dummy pads have a problem in that, since the bonding forces of each dummy pad
50
and
52
are same, a bonding force generated by the dummy pads
50
and
52
is not satisfactory. As a result, in the liquid crystal display with the conventional dummy pads, the TCP
42
can be separated from the liquid crystal panel
44
due to an impact force applied from the exterior thereof in the course of its fabrication process or its usage. The conventional TCPs
12
and
42
have limited usefulness because of such weak bonding force.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a liquid crystal display having dummy pads with an increased bonding force between a tape carrier package and a liquid crystal panel.
A further object of the present invention is to provide a method of fabricating a liquid crystal display having dummy pads that with an increased bonding force between a tape carrier package and a liquid crystal panel.
In order to achieve these and other objects of the invention, a liquid crystal display with dummy pads according to one aspect of the present invention includes a tape carrier package including first and second dummy pads to which signals are not applied, the first dummy pad having a larger width than the second dummy pad; and a liquid crystal panel including third and fourth dummy pads corresponding to the first and second dummy pads, respectively.
A liquid crystal display with dummy pads according to another aspect of the present invention includes a tape carrier package including output pads for outputting signals from an integrated circuit and dummy pads to which signals are not applied, at least one of said dummy pads having a width different from the output pads; and a liquid crystal panel including dummy pads corresponding to said dummy pads.
A method of fabricating a liquid crystal display with dummy pads according to still another aspect of the present invention includes the steps of forming first and second dummy pads on the tape carrier package in such a manner that the first dummy pad has a width different from the second dummy pad; forming third and fourth dummy pads corresponding to the first and second dummy pads, respectively, on the liquid crystal panel; and bonding the tape carrier package on the liquid crystal panel in such a manner that the first and second dummy pads correspond to the third and fourth dummy pads, respectively.
REFERENCES:
patent: 5889572 (1999-03-01), Takahashi et al.
patent: 6323930 (2001-11-01), Higuchi et al.
Cho Ju Sung
Chung Nag Su
LG.Philips LCD Co. , Ltd.
McKenna Long & Aldridge LLP
Nguyen Dung
Ton Toan
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