JP2003149666A - Flexible wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible wiring board capable of making a liquid crystal display device have a liquid crystal display panel having no display unevenness and high display quality by reducing the influence given by an internal stress of the flexible wiring board caused by heat pressure bonding which is applied to the liquid crystal display panel when the board is connected to the panel. SOLUTION: In a flexible wiring board having a semiconductor element, electrode terminals and wirings on the board, and in which the wirings are protected with board protective agent and which is heat-bonded to other substrates each which has electrode terminals, band-shaped slits are provided in vicinities of connection parts with other substrates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible wiring board used as an interface with electronic elements and electronic equipment, and particularly used in liquid crystal display devices.

[0002]

2. Description of the Related Art In manufacturing a liquid crystal display device, a semiconductor element for driving a liquid crystal display panel is mounted in a mounting step following a so-called cell step of holding a liquid crystal, and the outer periphery of the liquid crystal display panel is mounted. A printed wiring board and a flexible wiring board for supplying a transmission signal or power to the semiconductor element are mounted.

As a method for electrically connecting these flexible wiring boards, for example, a rubber connection method, a heat sealing method, a TAB (tape automated bonding) method, a CO
Although the G (chip on glass) method and the like have been proposed, the TAB method and the COG (chip on glass) method are predominant today from the viewpoint of automation of the mounting process and process throughput. The TAB method is a method of connecting a liquid crystal display panel and a printed wiring board using a flexible wiring board called TCP (tape carrier package) on which a semiconductor element such as a driver LSI is mounted. Note that C
The OG method is a method in which a driver element is directly mounted on one of a pair of substrates that sandwich a liquid crystal layer.

FIG. 5 shows a conventional TCP flexible wiring board connected to a liquid crystal display panel. The liquid crystal display panel 1 displays characters and images. A pair of transparent substrates 1a and 1b on which display electrode terminals are laid face each other at appropriate intervals, and a liquid crystal material is injected into the intervals to form the transparent substrate. The periphery of is sealed with a sealing material. The transparent substrate 1b is formed to be wider than the transparent substrate 1a, and a plurality of driving circuits for displaying a liquid crystal panel are formed in a portion protruding to the outside when the transparent substrate 1a is overlapped with the transparent substrate 1a. The flexible wiring board FC is used to connect the circuit board (printed wiring board) PC and the transparent substrate 1b, and may be bent and used. The flexible wiring board FC may also have the function of the circuit board.

In the flexible wiring board FC, a driving semiconductor element 4 is mounted on a substrate 5 formed of a resin film such as polyimide, and a metal wiring 6 of the semiconductor element 4 is a predetermined wiring on the back surface side of the substrate 5. Transparent substrate 1 arranged according to the configuration
It extends to the electrode terminal 5a which is a connection part with b. In order to protect the wiring 6, a protective agent (solder resist) 7 made of urethane is applied to the front surface side and the back surface side of the substrate 5 except for the electrode terminals 5a. When the flexible wiring board FC is bent and used for narrowing the frame of the liquid crystal display device, a bending slit 8 is provided in order to reduce an extra stress due to the bending. The bending slit 8 is a band-shaped cut in the bent portion of the substrate 5, and the wiring 6 that crosses the bending slit 8 is protected by a solder resist 7.

[0006]

The flexible wiring board FC is thermocompression-bonded to the transparent substrate 1b by using an anisotropic conductive film (ACF) 2 in which conductive particles are dispersed in a thermosetting resin film. . At that time, the substrate 5 is expanded by heat and then contracted by cooling, but the stress due to the expansion and contraction is transmitted to the transparent substrate 1b. Since the refractive index of the stressed part changes due to the strain of the substrate,
A local change in the refractive index occurs in the liquid crystal display panel 1, which causes display unevenness.

Therefore, an object of the present invention is to reduce the influence of stress on the liquid crystal display panel, which is caused by expansion and contraction of the flexible wiring board due to thermocompression when connecting the flexible wiring board to the liquid crystal display panel. It is also an object of the present invention to provide a high-display-quality liquid crystal display panel using the same and having no display unevenness.

[0008]

In order to solve the above-mentioned problems, the flexible wiring board according to claim 1 of the present invention comprises:
A semiconductor element, an electrode terminal, and a wiring are provided on a substrate, the wiring is protected by a protective agent, the electrode terminal is provided along at least one side of the substrate, and thermocompression bonding is performed with another substrate having the electrode terminal. In the flexible wiring board described above, a slit having a predetermined width is provided along the end face of the other substrate in the vicinity of the electrode terminal which is a connecting portion with the other substrate.

According to the present invention, since the strip-shaped slit made of only the substrate protective agent and the wiring is provided in the vicinity of the connecting portion with the other substrate, when the flexible wiring substrate is thermocompression-bonded to the other substrate, It is possible to prevent other boards from being distorted by internal stress when the flexible wiring board expanded by heating contracts due to cooling.

According to a second aspect of the present invention, based on the first aspect of the invention, the end face position closer to the other substrate in the slit is connected to the other substrate. , 0.5 mm inside the edge of the other substrate
To 0.5 mm outside and the predetermined width of the slit is 0.4 mm or more.

The absorption of internal stress by the slit depends on the position and width of the slit with respect to the other end face of the substrate. Therefore, by limiting these values to the above numerical values, it is possible to more effectively absorb the internal stress when the flexible wiring board expanded by heating contracts due to cooling, and prevent the other boards from being distorted.

The flexible wiring board according to claim 3 of the present invention is based on the invention of claim 1 or 2, and the flexible wiring board is a liquid crystal display device in which liquid crystal is provided between opposing glass substrates. The flexible wiring board is characterized in that it is located between the liquid crystal display panel in which the layers are sandwiched and the circuit board that drives the liquid crystal display panel, and connects these.

According to the present invention, claim 1 or claim 2
By using the described flexible wiring board for heating and pressure bonding to the glass substrate of the liquid crystal display panel, it is possible to provide a liquid crystal display device with high display quality and a narrow frame without display unevenness.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B are diagrams in which the flexible wiring board according to the present embodiment is mounted on a liquid crystal display panel, and FIG. 2 is a rear view of the flexible wiring board according to the present embodiment. The liquid crystal display panel 1 displays characters and images. A pair of transparent substrates 1a and 1b on which display electrode terminals are laid face each other at appropriate intervals, and a liquid crystal material is injected into the intervals to form the transparent substrate. The periphery of is sealed with a sealing material. The transparent substrate 1b is formed to be wider than the transparent substrate 1a, and a plurality of driving circuits for displaying the liquid crystal display panel 1 are formed in a portion protruding outward when being overlapped with the transparent substrate 1a. The flexible wiring board FC is used to connect the circuit board PC for controlling the transparent board 1b.

Flexible wiring board FC of the present embodiment
Is a semiconductor element 4 for driving mounted on a substrate 5 formed of a resin film such as polyimide, the metal wiring 6 of the semiconductor element 4 is arranged on the back surface side of the substrate 5, and is connected to the transparent substrate 1b. Up to the electrode terminal 5a. In order to protect the wiring 6, the electrode terminals 5 are provided on the front and back sides of the substrate 5.
A protective agent (solder resist) made of urethane is applied except for a.

When the flexible wiring board FC is bent and used for narrowing the frame of the liquid crystal display device, a bending slit 8 is provided in order to reduce extra stress due to the bending. The bending slit 8 has a band-shaped cut in the bent portion of the substrate 5. A stress absorbing slit 3 is provided between the electrode terminal 5a and the semiconductor element 4 in addition to the bending slit 8. The stress absorption slit portion is a strip-shaped cut in the substrate 5 near the electrode terminal 5a. The wiring 6 crossing the stress absorption slit 3 and the bending slit 8 is protected by a solder resist 7. Stress absorption slit 3
The connection-side end surface 3a is located 0.3 mm inward from the end surface of the transparent substrate 1b, and the width 3b of the stress absorption slit 3 is 0.5 mm. The bending slit 8 and the stress absorbing slit 3 are not formed up to the end portion (FCa, FCb in FIG. 1) of the flexible wiring board FC where the electrode terminal 5a is not formed. This is for maintaining the shape of the substrate 5.

Flexible wiring board FC of the present embodiment
Is an anisotropic conductive film (ACF: Anisotropic Conduct) in which conductive particles are dispersed in a thermosetting resin film.
iveFilm) 2 is used for thermocompression bonding to the transparent substrate 1b.
At that time, the substrate 5 is expanded by heat and then contracted by cooling, but since the stress absorbing slit 3 is provided, the internal stress due to the expansion and contraction of the substrate 5 is absorbed. Therefore, the stress applied to the transparent substrate 1b due to the expansion and contraction of the substrate 5 is reduced, the refractive index of the liquid crystal display panel 1 is eliminated, and high display quality without display irregularity can be obtained.

The position of the end surface 3a of the stress absorbing slit 3 and the width 3b of the stress absorbing slit 3 are not limited to the numerical values described in this embodiment, and the slit width 3b is wide and the stress is efficiently absorbed. It is necessary to form the stress absorption slits 3 near the transparent substrate 1b. The stress absorption rate is determined by the positions of the slit width 3b and the slit end face 3a.
If the slit width 3b is too narrow, the stress absorption slit 3 cannot fully absorb the stress.
A certain width or more is required. Further, when the position of the slit end face 3a is away from the end face of the transparent substrate 1b, the stress is not applied to the stress absorption slit 3, and the stress to be absorbed remains. With respect to the positions of the slit width 3b and the slit end face 3a, various samples were prepared and experiments were carried out. As a result, the position of the stress absorption slit end face 3a was 0.5 mm inside from the other substrate end faces to be connected. It suffices that it exists between the location (A portion in FIG. 3) and the location (B portion in FIG. 3) protruding 0.5 mm outward, and the stress absorption slit width 3b should be 0.4 mm or more. I understood.

Further, although one stress absorbing slit 3 is provided in the present embodiment, the present invention is not limited to this, and a plurality of stress absorbing slits 3 are arranged (FIG. 4A).
Alternatively, the stress absorbing slit 3 formed by one in the present embodiment may be divided into a plurality of shapes (see FIG. 4).
(B) Even if formed, the same effect can be obtained. Further, in the present embodiment, the anisotropic conductive film is used for bonding the flexible wiring board FC, but the invention is not limited to this, and any flexible wiring board of the present invention may be used as long as it is bonded by thermocompression bonding. The effect of FC is obtained similarly.

[0020]

Since the flexible wiring board of the present invention is provided with the stress absorbing slits near the electrode terminals, the internal stress due to expansion and contraction at the time of thermocompression bonding is absorbed by the stress absorbing slits and connected to another board. The stress on is reduced. Therefore, in the liquid crystal display panel to which the flexible wiring board of the present invention is connected, the stress applied to the liquid crystal display panel is small, whereby a high display quality liquid crystal display device without display unevenness can be obtained.

[0021]

[Brief description of drawings]

FIG. 1 is a top view and a cross-sectional view of a liquid crystal display device using a flexible wiring board according to an embodiment of the present invention.

FIG. 2 is a rear view of the flexible wiring board according to the embodiment of the present invention.

FIG. 3 is a diagram showing a position of an end surface of a stress absorption slit.

FIG. 4 is a flexible wiring board according to another embodiment of the present invention.

FIG. 5 is a top view and a cross-sectional view of a liquid crystal display device using a conventional flexible wiring board.

[Explanation of symbols]

1 Liquid crystal display panel 1a, 1b transparent substrate 2 Anisotropic conductive film 3 Stress absorption slit 3a End face of stress absorbing slit 3b Stress absorption slit width 4 Semiconductor element 5 substrates 5a Electrode terminal 6 wiring 7 Solder resist 8 folding slits FC flexible wiring board PC circuit board

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hikaru Fujita             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Daijuro Takano             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Hiroshi Higashi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 2H092 GA50 HA16 KB06 MA32 NA01                       PA01                 5E338 AA12 AA16 BB02 BB17 BB63                       BB75 CC01 CD32 EE26                 5E344 AA02 AA22 BB02 BB04 BB13                       CC05 CC21 CD04 DD06 DD10                       DD16 EE17

Claims (3)

[Claims] 1. A semiconductor device, an electrode terminal, and a wiring are provided on a substrate, the wiring is protected by a protective agent, the electrode terminal is provided along at least one side of the substrate, and the electrode terminal is provided. In the flexible wiring board to be heat-pressed with the board, the flexible wiring board is provided with a slit having a predetermined width along the end face of the other board, in the vicinity of the electrode terminal which is a connecting portion with the other board. 2. When connecting to the other substrate, an end face position of the slit closer to the other substrate is located between 0.5 mm inside and 0.5 mm outside the end face of the other substrate, The flexible wiring board according to claim 1, wherein the slit has a predetermined width of 0.4 mm or more. 3. In the liquid crystal display device, the flexible wiring board is positioned between a liquid crystal display panel having a liquid crystal layer sandwiched between opposing glass substrates and a circuit board for driving the liquid crystal display panel. It is a flexible wiring board for connecting to each other.
The flexible wiring board described.