Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-02-20
2004-10-19
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S150000, C349S152000
Reexamination Certificate
active
06806936
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a display module, a flexible wire board and a flexible wire board connecting method, which have an arrangement in which an anisotropic conductive adhesive is used to bond external connection terminals of a display panel, such as a liquid crystal display panel, to a terminal portion of a wire pattern of the flexible wire board, and a protective layer for protecting the wire pattern is formed on the flexible wire board.
BACKGROUND OF THE INVENTION
Conventionally used for connection between various electronic members, and particularly a connection between a liquid crystal display panel and its driving circuit is a flexible wire board having an arrangement in which a wire pattern is formed on a flexible insulating base material which is made of polymer, such as polyimide or the like.
On the flexible wire board is mounted a semiconductor device, thereby making up a semiconductor apparatus. The semiconductor device thus mounted becomes a driving circuit of a liquid crystal display panel. An example of a conventional semiconductor device connecting method is TCP (Tape Carrier Package) mounting. A flexible wire board on which a semiconductor device is mounted by the TCP mounting is, as shown in
FIG. 10
, arranged such that a Cu (copper) foil pattern
102
is bonded to a base polymer film
101
by a copper film adhesive layer
105
. The base polymer film
101
is a flexible insulating base material made of polymer.
Further, the Cu foil pattern
102
is covered with a polymer insulating protective film
104
. The insulating protective film
104
is bonded to the Cu foil pattern
102
by an insulating protective film adhesive layer
106
, provided that one end of the Cu foil pattern
102
is left uncovered, i.e., not covered with the insulating protective film
104
. The uncovered portion of the Cu foil pattern
102
functions as a terminal portion to connect to an external electronic member.
Here, the insulating protective film
104
insulates the Cu foil pattern
102
from the outside, protects the Cu foil pattern
102
from corrosion such as the formation of rust, and enhances resistance to bending.
On a surface of the uncovered portion of the Cu foil pattern
102
is formed a plating layer
103
which is given such plating as Au/Ni plating (i.e., an Ni layer is first formed as a base coat which is then plated with Au), Sn plating or the like. The plating layer
103
has a function to stabilize connection to an external electronic component by keeping the Cu foil pattern
102
rust free. Accordingly, the uncovered portion of the Cu foil pattern
102
becomes a terminal portion having superior conductivity.
Note that, though
FIG. 10
shows an arrangement in which the base polymer film
101
and the Cu foil pattern
102
are bonded with an adhesive (copper film use adhesive layer
105
), further available is an “adhesive-free” flexible wire board having an arrangement in which the base polymer film
101
and the copper foil pattern
102
are directly bonded.
Meanwhile, in accordance with a tendency in recent years to downsize outside dimensions of electronic devices of various kinds, such as a liquid crystal display device and the like, a form of mounting components which saves as larger space as possible is greatly demanded. In fulfillment of such demand, a flexible wire board as below is used in a bent state. The flexible wire board is connected to connection terminals of an electronic component, such as a liquid crystal display panel, etc., so as to supply the connection terminals with various signals including input signals from other electronic components such as a driving circuit and the like which are provided individually (i.e. so that they are segregated) from the electronic component having the connection terminals to which the flexible wire board is connected. By bending the flexible wire board, the flexible wire board can be placed in a position that does not obstruct the mounting of other electronic components. Moreover, thus bending the flexible wire board can downsize the whole device that includes a plurality of electronic components and the flexible wire board that connects them. Further, in accordance with a tendency in recent years to further downsize electronic devices of various kinds, such a flexible wire board that has as smaller radius of curvature as possible while maintaining high reliability is demanded.
In order to fulfil this demand, recently adopted as a connection method capable of mounting a semiconductor device onto the flexible wire board is COF (Chip On Film) mounting. The reason is that the COF (Chip On Film) mounting reduces a thickness of a base material of the flexible wire board more than TCP mounting does.
In the case of the TCP mounting, on one hand, a base material thickness of the base polymer film
101
which is a base material is 75 &mgr;m. On the other hand, in the case of the COF mounting, a base material thickness of the flexible wire board is as thin as 40 &mgr;m. The flexible wire board subject to the COF mounting has higher flexibility than that of the flexible wire board subject to the TCP mounting because of its thin base material, thereby being easily bent.
The flexible wire board subject to the COF mounting, however, has a problem such that a Cu foil pattern is likely to break when the flexible wire board is bent to be mounted onto a liquid crystal display panel.
More specifically, as shown in
FIG. 11
, in the case where a terminal portion (an uncovered portion of a Cu foil pattern
204
) of a flexible wire board
203
subject to COF mounting is bent for connection to not-shown external connection terminals of a liquid crystal display panel
201
, the absence of a solder resist
205
which is a protective layer in an end portion of the flexible wire board
203
allows a terminal corner
201
a
of the liquid crystal display panel
201
to contact terminals or a portion in the vicinity of the terminals where the Cu foil pattern
204
is exposed, thereby easily breaking wire in a portion where the contact is made.
In order to solve this problem, the uncovered portion of the Cu foil pattern
204
is conventionally fortified with resin coating or the like. However, the fortification like this inevitably increases manufacturing steps in the manufacture of the flexible wire board, thereby reducing manufacture efficiency and increasing manufacturing costs.
Further, Japanese Unexamined Patent Publication No. 138387/1997 (Tokukaihei 9-138387 published on May 27, 1997), for example, proposes a solution to the problem. Namely, an end portion of an insulating protective film to be a base material of a flexible wire board is caused to become wavy, then a bending portion of the flexible wire board is given a desirable R while maintaining a bent state, thereby dispersing stress which is added to the insulating protective film in the bending portion and suppressing emergence of a break in the wire pattern.
This arrangement, however, raises other problems. Namely, the formation of a wavy insulating protective film complicates the manufacture of the flexible wire board, which reduces manufacture efficiency and increases manufacturing costs, and also upsizes the flexible wire board by height of a wave of the wavy insulating protective film.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a display module, a flexible wire board and a flexible wire board connecting method, whereby, in a flexible wire board which is provided with an insulating protective film to cover a wire pattern and is used in a bent state, a short circuit in the wire pattern is surely prevented, and a break in the wire pattern when bent is conveniently suppressed, thus having superior reliability.
In order to attain the foregoing object, a display module according to the present invention which includes a display panel provided with external connection terminals and a flexible wire board having a wire pattern on a base material, terminals of the wire pattern of the flexible wire board and the ex
Kawaguchi Hisao
Nakaminami Hiroaki
Sakaki Yoichiro
Birch Stewart Kolasch & Birch, LLP.
Chowdhury Tarifur R.
Sharp Kabushiki Kaisha
LandOfFree
Display module including a display panel connected to a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Display module including a display panel connected to a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Display module including a display panel connected to a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3289712