Active solid-state devices (e.g. – transistors – solid-state diode – Non-single crystal – or recrystallized – semiconductor... – Field effect device in non-single crystal – or...
Reexamination Certificate
1998-12-04
2003-10-07
Lee, Eddie (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Non-single crystal, or recrystallized, semiconductor...
Field effect device in non-single crystal, or...
C257S059000, C257S783000, C349S058000, C349S149000, C349S150000, C349S151000, C349S152000
Reexamination Certificate
active
06630686
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a liquid crystal display (LCD) device, and in particular, the present invention relates to a method for an LCD in which the pad terminal communicating an electric signal to an outer device and the terminal of the outer device cohere well with each other, and to the structure of an LCD having the same pad terminal.
2. Description of Related Art
The cathode ray tube (CRT), the most widely used display device, is being replaced by the thin flat display device because the flat display device is thinner and lighter than the CRT so it can be applied to any place. Active research activities have focused on the development of liquid crystal display devices because of their high resolution and fast response time suitable for displaying motion picture images. Furthermore, the active panel comprising an active switching element such as a thin film transistor (or TFT) is more popularly applied to the LCD.
A liquid crystal display device works by using polarization and optical anisotropy of a liquid crystal. By controlling the orientation of liquid crystal molecules having rod shape through polarization technique, transmission and interception of a light through the liquid crystal are achieved due to the anisotropy of the liquid crystal. This principle is applied to the liquid crystal display device. Active matrix LCDs (AMLCDs) having TFTs arranged in a matrix pattern and pixel electrodes connected to the TFTs provide high quality images and are now widely used.
The structure of a conventional AMLCD will now be described.
FIG. 1
shows a perspective view of the AMLCD and
FIG. 2
shows the cross-sectional view of
FIG. 1
along the cutting line II—II. The conventional AMLCD comprises an upper panel
3
and a lower panel
5
which are joined to each other with a liquid crystal material
10
injected therebetween. The upper panel
3
has a color filter panel which includes a sequential arrangement of red(R), green(G) and blue(B) color filters
7
on a first transparent substrate
1
a
at pixel positions designed in a matrix pattern. Among these color filters
7
, black matrixes
9
are formed in a lattice pattern. The black matrixes
9
prevent the colors from mixing at the boundary area. On the color filters
7
, a common electrode
8
is formed. The common electrode
8
is one electrode of the two electrodes generating an electric field applied to the liquid crystal layer.
The lower panel
5
of the LCD comprises switching elements and bus lines generating the electric field for driving the liquid crystal layer. This panel is called an active panel. The active panel
5
of an AMLCD includes pixel electrodes
41
designed in a matrix pattern and formed on a second transparent substrate
1
b.
Along the column direction of the pixel electrodes
41
, signal bus lines
13
are formed, and along the row direction of the pixel electrodes
41
, data bus lines
23
are formed. At a corner of a pixel electrode
41
, a TFT
19
for driving the pixel electrode
41
is formed. A gate electrode
11
of the TFT
19
is connected with the signal bus line
13
(or the gate line). A source electrode
21
of the TFT
19
is connected with the data line
23
(or the source line). A semiconductor layer
33
is formed between the source electrode
21
and the drain electrode
31
. An ohmic contact exists between the source electrode
21
and the semiconductor layer
33
and between the drain electrode
31
and the semiconductor layer
33
are also ohmic contacted. A gate pad
15
and a source pad
67
, the terminals of the bus lines, are formed at the end portion of the gate line
13
and the source line
23
, respectively. Additionally, a gate pad terminal
57
and a source pad terminal
25
are formed on the gate pad
15
and the source pad
67
, respectively.
As the signal voltage applied to the gate pad
15
is applied to the gate electrode
11
via the gate line
13
, the TFT
19
of the corresponding gate electrode
11
transitions to the ON state. Then the source electrode
21
and the drain electrode
31
of the TFT
19
are electrically connected so that the electrical picture data applied to the source pad
25
is sent to the drain electrode
31
through the source line
23
and the source electrode
21
. Therefore, by controlling the signal voltage to the gate electrode
11
, the transfer of picture data to the drain electrode is controlled. That is, the TFT
19
acts as a switching element. A gate insulating layer
17
is inserted between the layer including the gate electrode
11
and the layer including the source electrode
23
to electrically isolate them. A passivation layer
37
is formed on the layer including the source line
23
to protect all elements of the transistor.
The color filter panel
3
and the active panel
5
are bonded together to face each other with a certain separation distance therebetween (i.e., a cell gap). Liquid crystal material
10
fills the cell gap and the edge of the bonded panels is sealed with a sealant
81
such as an epoxy to prevent the liquid crystal from leaking out so that a liquid crystal panel of an AMLCD is completed.
The AMLCD is finally made by assembling the liquid crystal panel with peripheral devices for the screen data. At this time, the pads of the liquid crystal panel and the terminal of the peripheral devices are generally electrically connected with a tape carrier package (TCP) using an anisotropic conductive film (ACF).
FIG. 3
shows a general structure of the ACF.
FIGS. 4
a
and
4
b
illustrate the conventional method for connecting the TCP to the pad using the ACF and illustrate the structure of the pad.
As shown in
FIG. 3
, the ACF
71
comprises a plurality of conductive ball
95
coated with an insulation membrane
93
in an isotropic film
31
. On the pad terminals
47
connected to the pads
45
(for example, the gate pads
15
or the source pad
67
) at the edge of the liquid crystal panel, an ACF
71
is attached and TCP
73
is sequentially attached thereon. At this time, the conductive pad
75
of the TCP
73
should be aligned with the pad
45
(for example, the gate pads
15
or the source pad
67
) of the liquid crystal panel, as shown in
FIG. 4
a.
The TCP
73
is pressed and heated while the conductive balls
95
are inserted between the TCP pad
75
and the pad terminal
47
of the liquid crystal panel. When sufficient pressure is applied against the TCP
73
, the insulation membrane
93
covering the conductive ball
95
are broken so that each TCP pad
75
becomes electrically connected to each pad terminal
47
of the liquid crystal panel, as shown in
FIG. 4
b.
Even if there are some conductive balls
95
between the neighboredpad terminals
47
, the neighbored pad terminals
47
are electrically isolated from each other because the conductive balls
95
are covered by the insulation membrane
93
.
In the step of attaching the TCP to the pad terminal as mentioned above, the film portion
77
between each pad portion
73
are expanded somewhat by heat and pressure and cohered to the passivation layer
37
formed on the top of the liquid crystal panel. As shown in
FIG. 5
, after removing the pressure and the heat, the expanded film portion of the TCP is shrunk which results in the pulling force
83
so that the passivation layer
37
being cohered with the film portion
77
is peeled off.
Generally, after the liquid crystal panel is completed, the edge portion of the panel having the shorting bar used for protecting the electrostatic need to be trimmed off. At that time, the trimming force, which is applied to the trimmed edge, can cause the passivation layer
37
or the gate insulating layer
17
to be structurally unstable. At this portion, the passivation layer
37
can be easily peeled off, when the heating energy is removed after the film portion
77
of the TCP is cohered with the passivation layer
37
with the ACF
71
therebetween. This comes from the peeling force
89
made of the vector summ
Lee Eddie
Lee Eugene
LG.Philips LCD Co. , Ltd.
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