Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-11-18
2001-10-02
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S152000
Reexamination Certificate
active
06297868
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device and, more particularly, to an improvement in a semiconductor driving circuit which is mounted on the same.
A liquid crystal display panel which constitutes a liquid crystal display device utilizes, as a chamber for the liquid crystal, transparent substrates arranged to oppose each other with the liquid, crystal interposed therebetween. This liquid crystal display panel has a multiplicity of pixels formed in the area of the liquid crystal.
Means for producing an electric field is incorporated in each of the pixels to control the optical transmissivity of the liquid crystal of individual pixels. To provide this control, semiconductor driving circuits (hereinafter referred to as driver ICs) for supplying signals (voltages) to the electric field producing means of the respective pixels via signal lines are mounted on the peripheral portion of the liquid crystal display panel. If this mounting is adopted, one of the transparent substrates which constitute the panel is formed to extend beyond the other substrate at a peripheral portion of the liquid crystal display panel, and the driver ICs are mounted on this extended area. Accordingly, interconnecting layers which are connected to the input-side bumps of the driver ICs and interconnecting layers which are connected to the output-side bumps of the, driver ICs and supply signals to the respective pixels are formed in the extended area. The driver ICs are mounted on the extended area by so-called facedown-bonding in which their bumps are connected to the respective interconnecting layers with an anisotropic conductive film (ACF) interposed therebetween.
Surface-mount technologies of the aforementioned driver ICs for one of the substrates of the liquid crystal display panel are disclosed for example in Japanese Patent Application Laid-Open JP-A-172385/1987. Bump structures for semiconductor integrated circuit devices are disclosed for example in Japanese Patent Application Laid-Open JP-A-368130/1992 and Japanese Patent Application Laid-Open JP-A 166810/1993.
SUMMARY OF THE INVENTION
However, in recent years, it has been found that an electrical short circuit may occur between adjacent bumps of such a driver IC because of the trends toward larger size liquid crystal display panels and a finer-pitch arrangement of bumps on the driver IC.
From an investigation into the cause of this phenomenon, it has been found that, during thermocompression bonding in the process, of mounting a driver IC on a liquid crystal display device with an anisotropic conductive film (ACF) interposed therebetween, the binder contained in the anisotropic conductive film (ACF) is reduced in viscosity and fluidized, and while the binder is being discharged from between adjacent bumps, the conductive material mixed with the binder forms a residue (or a drift) between bumps.
The present invention is directed to the above-described problems, and an object of the present invention is to provide a liquid crystal display device which is capable of avoiding the occurrence of an electrical short circuit between adjacent bumps of a driver IC.
A representative aspect of the invention disclosed in the present application will be described below in brief.
One liquid crystal display device according to the present invention is characterized in that driver ICs are mounted on the liquid crystal display device with an anisotropic conductive film interposed therebetween and each of the driver ICS has bumps arranged in such a manner that the width of the space between one bump and an adjacent bump becomes larger toward a central side of each of the driver ICs.
In the liquid crystal display device constructed in this manner, the binder contained in the anisotropic conductive film (ACF) can be smoothly discharged without allowing the conductive material mixed with the binder to form a residue between adjacent bumps, in the process of reducing the viscosity of and fluidizing the binder of the anisotropic conductive film (ACF) and discharging the fluidized binder through the spaces between the adjacent bumps during the thermocompression bonding of the driver ICs. Accordingly, an electrical short circuit is prevented from occurring due to the conductive material between the adjacent bumps.
This feature offers a huge number of great advantages in the present situation in which the trend is to narrow the gaps between adjacent bumps of a driver IC and reduce the area of each of the bumps and in which it is necessary to increase the amount of the conductive material to be mixed with the binder in the anisotropic conductive film (ACF).
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5864377 (1999-01-01), Kim
Takenaka Yuuichi
Tsujita Yoshiyuki
Antonelli Terry Stout & Kraus LLP
Dudek James A.
Hitachi , Ltd.
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