Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1997-12-18
2001-04-03
Sough, Hyung-Sub (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S254000, C349S150000, C361S749000
Reexamination Certificate
active
06211469
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a printed-circuit substrate, such as a TCP (Tape Carrier Package), which includes comb-type electrodes that are connected to respective comb-type electrodes formed on a liquid-crystal panel, and an integrated circuit for driving the liquid-crystal panel (hereinafter, referred to as IC), and also relates to its connecting method.
BACKGROUND OF THE INVENTION
Recently, with regard to connecting structure between a liquid-crystal panel and an external device, printed-circuit substrates, such as TAB (Tape Automated Bonding), FPC (Flexible Printed Circuit) and TCP, have been generally employed. IC chips for driving the liquid-crystal panel are assembled on the printed-circuit substrates, thereby achieving compactness and high functionality. Thus, the packaging density of IC chips is improved in a liquid crystal display wherein these substrates are employed.
Today, in liquid crystal displays having the above-mentioned liquid-crystal panels, thin-width TCPs, which have a smaller gap between the input terminal and the output terminal, have been widely used in order to further achieve compactness.
For example, as shown in
FIGS. 4 and 5
, a thin-width TCP, which is formed into a belt shape, is provided with an IC chip
31
that is used for driving the liquid-crystal panel. In the thin-width TCP
30
, a plurality of output electrodes
32
and input electrodes
33
, which are respectively connected to the terminals of the IC chip
31
, are mounted on both sides of the IC chip
31
along the length of the thin-width TCP
30
.
The output electrodes
32
are formed into a comb shape in an extending manner to the left from the IC chip
31
as shown in the drawings. The input electrodes
33
are also formed into a comb shape in an extending manner to the right from the IC chip
31
as shown in the drawings. Those output electrodes
32
and the input electrodes
33
are covered with a film portion
34
and supported thereby.
In the central portion of the thin-width TCP
30
is provided an opening
34
b
through which the IC chip
31
is connected to the output electrodes
32
and the input electrodes
33
. Ends of the output electrodes
32
and the input electrodes
33
respectively stick out inside the opening
34
b.
The opening
34
b
is filled with protective resin through a molding process; this allows the IC chip
31
to be connected to the output electrodes
32
and the input electrodes
33
, and securely fixed therein. Thus, a resin mold section
36
is formed around the IC chip
31
.
Further, in the film portion
34
is formed a slit
34
a
by removing a part of the film portion
34
at the vicinity of the end portion on the input side. Exposed terminals
33
a
of the input electrodes
33
are located inside the slit
34
a
so as to be soldered to electrodes of a printed-circuit substrate or other substrates.
The following description will discuss a connecting method where the thin-width TCP
30
is employed. In the case where the thin-width TCP
30
is used for connecting the liquid crystal panel and the printed-circuit substrate, the output electrodes
32
and electrodes, not shown, of a liquid crystal panel
40
are first connected respectively as shown in
FIG. 6
by the use of an anisotropic conductive film or other materials.
The input electrodes
33
, on the other hand, are connected to the respective electrodes
42
through solder
43
. Thus, the printed-circuit substrate
41
and the liquid crystal panel
40
are electrically connected to each other through the thin-width TCP
30
.
The connection between the thin-width TCP
30
and the printed-circuit substrate
41
through the solder
43
is made by using a soldering iron
44
. In this case, however, the resin mold section
36
, which is formed through the molding process of the IC chip
31
, protrudes from the back side of the thin-width TCP
30
; this protruding resin mold section
36
results in a step W
O
even when the terminals are pressed down by the soldering iron
44
.
This causes the terminals
33
a
to be lifted from the printed-circuit substrate
41
, and since the terminals
33
a
do not contact the electrodes
42
well, it is difficult to solder both of them.
Therefore, in a conventional method, the terminals
33
a
and the electrodes
42
are soldered while avoiding the influence of the step W
O
caused by the protruding resin mold section
36
, as shown in FIG.
6
.
More specifically, the printed-circuit substrate
41
is fixed in a slanted state by using a device for supporting the printed-circuit substrate
41
, not shown. This arrangement makes it possible to bring the terminals
33
a
in contact with the electrodes
42
while avoiding the influence of the step W
O
caused by the protruding resin mold section
36
.
Next, after fixing the resin mold section
36
and the printed-circuit substrate
41
by the use of a temporary securing tape
45
, the terminals
33
a
and the electrodes
42
are soldered by pressing them to contact one another using the tip of the soldering iron
44
.
However, this method, which uses the thin-width TCP
30
having the conventional structure and wherein soldering is made by the soldering iron
44
while holding the conventional printed-circuit substrate
41
in the slanted state, raises the following problems.
(1) Problems Associated with the Structure of the Conventional Thin-width TCP
30
:
(a) The film portion
34
in the thin-width TCP
30
has elasticity to a certain degree. Therefore, in the conventional structure wherein the terminals
33
a
are situated in the slit
34
a
, the elasticity of the film portions
34
lying on both sides of the slit
34
a
in the thin-width TCP
30
in the length-wise direction gives adverse effects on the pliability of the terminals
33
a.
Therefore, even if the terminals
33
a
are pressed so as to bring them into contact with the electrodes
42
, the terminals
33
a
tend to be lifted up, resulting in difficulty in contacting both of them.
The contact between them becomes even worse when the printed-circuit substrate
41
or the liquid crystal panel
40
has warping or when the thin-width TCP
30
has a curl-distortion in its own structure. This results in reliability problem in the connected structure between them.
(b) In particular, in the printed-circuit substrates such as thin-width TCPs
30
wherein the IC chip
31
and the slit
34
a
are closely located, when the thin-width TCP
30
is bent by pressing its terminals
33
a
using the tip of the soldering iron
44
, the distortion stress may affect the resin mold section
36
and cause cracking in the resin mold section
36
, if the portion of the slit
34
a
does not have sufficient pliability.
(2) Problems Associated With the Connecting Method:
(a) In the conventional connecting method, since the tip of the soldering iron
44
has to be brought into contact with the slanting portion, it is difficult to keep the tip stably contacting with the connecting portion. For this reason, it is hard to obtain stable solder quality and to improve the reliability of the connecting structure.
(b) The soldering iron
44
is susceptible to wear in its tip; this also makes it difficult to obtain stable solder quality and to improve the reliability of the connecting structure.
(c) The tip of the soldering iron
44
might be caught by the exposed terminals
33
a
, causing cutoffs in them especially when the exposed terminals
33
a
have narrow terminal pitches and are made of thin copper foil.
(d) As is described in (b) of (1), in the printed-circuit substrates such as thin-width TCP
30
s wherein the IC chip
31
and the slit
34
a
are closely located, when the thin-width TCP
30
is bent by pressing its terminals
33
a
using the tip of the soldering iron
44
, the distortion stress may affect the resin mold section
36
and cause cracking in the resin mold section
36
.
SUMMARY OF THE INVENTION
The present invention is devised to solve the above-mentioned problems, and its objective is to provide a printed-circuit substrate which achieves
Conlin David G.
Dike Bronstein, Roberts & Cushman LLP
Neuner George W.
Sharp Kabushiki Kaisha
Sough Hyung-Sub
LandOfFree
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