KR101024648B1 - Liquid crystal display device - Google Patents

Abstract

The present invention provides a liquid crystal display device capable of preventing separation of a driving integrated circuit and a printed circuit board.

The present invention provides a printed circuit board which generates signals required for a driving integrated circuit and includes a plurality of output pads to which the driving integrated circuit is bonded and a dummy pad between the output pads; Each of the driving integrated circuits includes a plurality of chip on films bonded on the output pads; The dummy pad may be grounded.

Description

[0001] LIQUID CRYSTAL DISPLAY DEVICE [0002]             

1 and 2 are a plan view and a cross-sectional view showing a chip on film (COF) of a conventional liquid crystal display.

3 is a view showing a part of a conventional printed circuit board.

4 is a plan view schematically illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

FIG. 5 is a diagram illustrating a part of the printed circuit board illustrated in FIG. 4.

<Description of Symbols for Main Parts of Drawings>

52a, 52b: first and second signal wiring

53a, 53b: solder resist bump: 54a, 54b

55: resin driver IC: 56

51: base film ground: 75,175

105: liquid crystal panel 131: printed circuit board

115: data drive IC 113: chip on film (COF)

125: gate drive IC 70,170: output pad                 

72,172: Dummy Pad

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of preventing separation of a driving integrated circuit and a printed circuit board.

Recently, with the rapid development of the information society, there is a need for a flat panel display having excellent characteristics such as thinning, light weight, and low power consumption, among which a liquid crystal display has a resolution, It is excellent in color display and image quality, and is actively applied to notebooks and desktop monitors.

In general, a liquid crystal display device arranges two substrates on which electrodes are formed so that the surfaces on which the two electrodes are formed face each other, injects a liquid crystal material between the two substrates, and applies a voltage to the two electrodes to generate an electric field. By moving the liquid crystal molecules, the image is expressed by the transmittance of light that varies accordingly.

Recently, the liquid crystal display device is characterized by light weight, thin, low power consumption driving, and the quality of the liquid crystal display is improved by the improvement of the liquid crystal material and the development of micro-pixel processing technology, and the application range is gradually widening. to be. In particular, when a liquid crystal display device is employed in a portable device such as a notebook computer, the liquid crystal display device should be manufactured in a portable type so as to be convenient for the user to carry.

The liquid crystal display device includes a liquid crystal panel in which liquid crystal is injected between two substrates, a backlight disposed under the liquid crystal panel and used as a light source, and a driving unit for driving the liquid crystal panel, which is located outside the liquid crystal panel. The liquid crystal panel is composed of pixels arranged in a matrix between two glass substrates and a switching element that controls signals supplied to these pixels, that is, a thin film transistor.

On the other hand, the driving unit is a driving circuit for connecting a liquid crystal panel and a printed circuit board (PCB) on which components generating various control signals, data signals, etc. are mounted, and a liquid crystal panel and a printed circuit board. And a drive integrated circuit (hereinafter referred to as a drive integrated circuit), which includes a chip on glass (COG) and tape carrier package (TCP: tape), depending on how the drive IC is packaged on a liquid crystal panel. carrier package) and chip on film (COF).

COG mounts the drive IC on the liquid crystal panel, which increases the volume of the liquid crystal display device, whereas TCP or COF mounts the drive IC using a separate film, so the film containing the drive IC is placed on the back of the liquid crystal panel. It can be bent to have a compact structure.

Therefore, in recent years, TCP or COF is mainly used, and in general, TCP or COF also refers to the film itself in which the drive IC is embedded.

Since COF has a thin film thickness compared to TCP, it can have a finer structure than TCP and is cheaper in terms of manufacturing cost. Therefore, the use of COF has recently increased.

1 and 2 are plan and cross-sectional views showing a COF.

1 and 2, a plurality of first and second signal wires 52a and 52b extending in the horizontal direction and corresponding to one-to-one are formed on the base film 51. Here, the first signal wiring 52a is electrically connected to the output pad of the liquid crystal panel, and the second signal wiring 52b is electrically connected to the output pad of the PCB.

Solder resists 53a and 53b are formed on the first and second signal wires 52a and 52b to partially expose the first and second signal wires 52a and 52b, respectively.

Bumps 54a and 54b are formed on the first and second signal wires 52a and 52b exposed by the solder resists 53a and 53b, respectively, and the drive ICs 56 are formed on the bumps 54a and 54b. ) Is placed. The first and second signal wires 52a and 52b and the drive IC 56 are connected through bumps 54a and 54b.

Resin 55 is formed on both sides of the driver IC 56. The resin 55 covers the solder resists 53a and 53b, the first and second signal wires 52a and 52b, and the bumps 54a and 54b.

The COF is bonded by a pad of a liquid crystal panel, a pad of a PCB, and an anisotropic conductive film (ACF).

The COF as described above uses an anisotropic conductive film (ACF) when connected to the output pad of the liquid crystal panel and the output pad of the PCB, respectively. Here, the ACF is a kind of thermosetting resin film containing small conductive particles. The ACF is attached onto the output pad of the PCB to be conductively bonded, and the COF is attached to the output pad of the PCB.

Thereafter, when the thermocompression bonding is performed using a heating bar (not shown), electrical contact is made in the vertical direction. At this time, it is preferable to apply appropriate heat and pressure in consideration of the material of the COF and ACF. COF and liquid crystal panel can be connected in the same way.

However, in the process of connecting the COF and the output pad of the PCB as described above, when the COF and the output pad of the PCB is thermally compressed, the base film 51 of the COF having a thin thickness swells and the COF is separated from the pad of the PCB. Occurs frequently.

Specifically, referring to the pad of the PCB illustrated in FIG. 3, the PCB has an output pad 70 connected to the second signal line 52b of the COF and dummy pads 72 positioned to the left and right of the output pad 70. Is located. The dummy pad 72 is an extra pad for further mounting signal lines when the resolution is increased or the channel is increased.

After attaching the COF and the output pad 72 of the PCB 31 and then the bonding portion of the COF and the output pad 72 of the PCB 31 is thermocompressed by a heating bar (not shown) PCB (31). A lot of heat is transferred to the output pad 70 and the dummy pad 72. Here, the output pad 70 of the PCB is connected to the connection wiring 78 including a plurality of signal lines and the like to be able to dissipate heat transferred by the heating bar, but the dummy pad 72 is electrically Since it is independent, the heat transmitted by the heating bar (heating bar) will not be able to dissipate heat.                         

Accordingly, the dummy pad 72 retains a greater amount of heat than the output pad 70, and this heat is transferred back to the base film 51 of the COF. Accordingly, bubbles are generated in the base film 51 of the COF formed thinner than the film used for TCP, and as the bubbles expand, the defects such as the pads of the COF and the PCB are separated.

Accordingly, an object of the present invention is to provide a liquid crystal display device capable of preventing separation of a driving integrated circuit and a printed circuit board.

In order to achieve the above objects, a liquid crystal display according to the present invention generates signals required for a driving integrated circuit and a printed circuit board having a plurality of output pads to which the driving integrated circuit is bonded and a dummy pad formed between the output pads. Wow; Each of the driving integrated circuits may include a plurality of chip on films mounted on the output pads, and the dummy pad may be attached to the printed circuit board and the plurality of chip on films by a device that generates heat. It is characterized in that the ground to discharge the heat generated when the outside.

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A liquid crystal display according to the present invention comprises: a printed circuit board for generating signals necessary for a driving integrated circuit and having a plurality of output pads to which the driving integrated circuit is bonded and a dummy pad formed between the output pads; Each of the driving integrated circuits may include a plurality of chip on films mounted on the output pads, and the dummy pad may be attached to the printed circuit board and the plurality of chip on films by a device that generates heat. It characterized in that it comprises a heat dissipation path for dissipating heat generated when.

The heat dissipation path may further include a ground wire connected to the dummy pad.

Other objects and advantages of the present invention in addition to the above object will become apparent from the description of the preferred embodiment of the present invention with reference to the accompanying drawings.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 4 and 5.

4 is a plan view illustrating a liquid crystal display according to the present invention.

As shown in FIG. 4, a liquid crystal panel 105 in which liquid crystal cells are arranged in a matrix form and a driving circuit unit 107 for driving the liquid crystal panel are provided.

In the liquid crystal panel 105, the gate lines and the data lines are arranged to cross each other, and the liquid crystal cells are positioned in an area where the gate lines and the data lines cross each other. The liquid crystal panel 105 is provided with pixel electrodes and a common electrode for applying an electric field to each of the liquid crystal cells. Each of the pixel electrodes is connected to any one of the data lines via source and drain terminals of a thin film transistor, which is a switching element.

The gate electrode of the thin film transistor is connected to any one of the gate lines through which the pixel voltage signal is applied to the pixel electrodes for one line. The thin film transistor causes the pixel voltage supplied to the data line to be charged to the pixel electrode in response to the gate high voltage Vgh supplied to the gate line.

That is, the liquid crystal cells charge the corresponding pixel voltage from the data line when the TFT is turned on by the gate high voltage Vgh which is sequentially supplied to the gate line, and maintains the charging voltage until the TFT is turned on again. .

The pixel voltage charged in the liquid crystal cell of any n-th gate line is maintained by the storage capacitor Cst formed by overlapping the pixel electrode with the previous gate line.

The gate high voltage Vgh is supplied to each of the gate lines for each frame only during one horizontal period (1H) at which the corresponding gate line is driven, that is, the pixel voltage is applied to the pixel electrode. Vgl) is supplied.

The storage capacitor Cst maintains the voltage charged in the current pixel electrode by the gate low voltage Vgl supplied to the previous gate line.

The driving circuit unit 107 may include a gate driver 127 for driving the gate lines, a data driver 117 for driving the data lines, and a timing controller for controlling the gate driver 127 and the data driver 117 ( 111 and a power supply unit (not shown) for supplying various driving voltages used in the liquid crystal display device.

The timing controller 111 controls the driving timing of the gate driver 127 and the data driver 117 and supplies the pixel data signal to the data driver 117. The power supply unit generates driving voltages such as a gate high voltage Vgh and a gate low voltage Vgl required by the liquid crystal display using the input power.

The gate driver 127 sequentially supplies the scanning signals to the gate lines to sequentially drive the liquid crystal cells on the liquid crystal panel by one line. The data driver 117 supplies a pixel voltage signal to each of the data lines whenever a scanning signal is supplied to any one of the gate lines.

Accordingly, the liquid crystal display displays an image by adjusting light transmittance by an electric field applied between the pixel electrode and the common electrode according to the pixel voltage signal for each liquid crystal cell.

Among them, the data driver 117 and the gate driver 127 directly connected to the liquid crystal panel 105 are integrated into a plurality of integrated circuits (ICs). Each of the integrated data driver IC 115 and the gate driver IC 125 is mounted on a chip on film (COF) 113, 123 and connected to the liquid crystal panel 105 in a tape automated bonding (TAB) manner.

Here, the driver ICs 115 and 125 connected to the liquid crystal panel 105 in the TAB manner through the COFs 113 and 123 are connected from the outside through signal lines mounted on the printed circuit boards 131 and 133 connected to the COF 113 and 123. Input control signals and DC voltages are supplied and interconnected.

In detail, the data drive ICs 125 are connected in series through signal lines mounted on the data PCB 131 and common to the control signals from the timing controller 111 and the driving voltages from the pixel data signal and the power supply unit. Will be supplied. The gate drive ICs 125 are connected in series through signal lines mounted on the gate PCB 133, and commonly receive control signals from the timing controller and driving voltages from the power supply unit.

5 is a view illustrating in detail the output pad 170 and the dummy pad 172 of the PCB (131,133) shown in FIG.

The PCBs 131 and 133 illustrated in FIG. 5 include output pads 170 connected to signal lines of the COFs 113 and 123, and dummy pads 172 positioned to the left and right of the output pads 170.

The output pads 170 of the PCB 131 are connected to signal lines of the COFs 113 and 123, and to a plurality of connection lines 178, ground lines (GND) 175, and the like.

The dummy pad 172 is used as an extra pad for further mounting signal lines when the resolution is increased or the channel is increased, and each of the dummy pads 172 is connected to the ground line 175 (GND). Accordingly, the heat transferred to the dummy pad 172 during the thermal compression of the COF 113 and the output pad 170 of the PCB is radiated through the ground wiring (GND) 175, thereby the COF 113 and the PCB (131,133). It is possible to prevent the separation from the output pad 170.

In more detail, after attaching the output pads 170 of the COFs 113 and 123 and the PCBs 131 and 133, the bonding bar between the COFs 113 and 123 and the output pads 170 of the PCBs 131 and 133 is heated. When thermal compression is performed by a lot of heat is transferred to the output pad 170 and the dummy pad 172 of the PCB (131,133). Here, the output pads of the PCBs 131 and 133 are connected to a connection line 178 including a plurality of signal lines, a ground line (GND) 175, and the like, thereby dissipating heat transferred by the heating bar. do.

Since the dummy pad 172 is also connected to the ground wiring (GND) 175 unlike the related art, it is possible to dissipate heat transferred by the heating bar to the ground wiring (GND) 175. Here, the ground wiring (GND) 175 may be a separate heat dissipation path capable of heat dissipation. In this case, a wiring for grounding exists between the dummy pad 172 and the heat dissipation path.

As a result, the heat transferred to the dummy pad 172 and the output pad 170 can be all radiated as compared with the related art, thereby reducing the thermal deviation between the dummy pad 172 and the output pad 170. As a result, the base films of the COFs 113 and 123 are not damaged so that the COFs 113 and 123 and the PCBs 131 and 133 are not separated.

As described above, the liquid crystal display according to the present invention connects the dummy pads 172 of the PCBs 131 and 133 to the ground wiring (GND) 175 so that the heat applied when the COFs 113 and 123 are bonded to the PCBs 131 and 133 is grounded. Heat dissipation (GND) 175. Accordingly, the thermal deviation between the dummy pad 172 and the output pad 170 can be reduced, thereby preventing separation of the COFs 113 and 123 and the PCBs 131 and 133.

As described above, in the liquid crystal display according to the present invention, by connecting the dummy pad of the printed circuit board to the ground GND, the heat applied when the chip-on film and the printed circuit board are bonded can be radiated to the ground GND. Accordingly, the thermal deviation between the dummy pad and the output pad can be reduced, thereby preventing separation of the chip-on film and the printed circuit board.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (4)

A printed circuit board generating signals required for a driving integrated circuit and having a plurality of output pads to which the driving integrated circuit is bonded and a dummy pad formed between the output pads; Each of the driving integrated circuits is provided with a plurality of chip-on film bonded on the output pads, The dummy pad, And a ground to discharge heat generated when the printed circuit board and the plurality of chip-on films are attached to the outside by a heat generating device. The method of claim 1, And a ground wiring connected to the dummy pad. A printed circuit board generating signals required for a driving integrated circuit and having a plurality of output pads to which the driving integrated circuit is bonded and a dummy pad formed between the output pads; Each of the driving integrated circuits includes a plurality of chip-on films bonded on the output pads, The dummy pad, And a heat dissipation path for dissipating heat generated when the printed circuit board and the plurality of chip-on films are attached to each other by a device that generates heat. The method of claim 3, wherein The heat dissipation path further comprises a ground wiring connected to the dummy pad.

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