JPH0593917A - Production of external circuit connecting structure for liquid crystal panel - Google Patents

Abstract

PURPOSE:To improve a yield without adding higher strictness particularly to environment and the management of conductor particles and to allow and facilitate the repair to regenerate the juncture between a liquid crystal panel and an external circuit in the process for production of the connecting structure for connecting electrodes for driving the liquid crystal panel and the external circuit for driving the liquid crystal panel by using a thermosetting resin dispersedly contg. the conductor particles. CONSTITUTION:The conductor particles remaining in non-desired parts are melted away by a laser beam 11 after disposition of the cured body of a film formed of the thermosetting resin 9 dispersedly contg. the conductor particles in the method for producing the connecting structure for the external circuit for the liquid crystal panel by positionally matching the electrodes 3 for connecting the external circuit connected to the electrodes for driving the liquid crystal panel and provided on the substrate 2 of the liquid crystal panel 1 and the external circuit electrodes 5 connected to the external circuit 6 for driving the liquid crystal panel and disposing the cured body of the above-mentioned film between these electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal panel, and more particularly to a method of manufacturing a connection structure between a liquid crystal panel having a ferroelectric liquid crystal and an external circuit. The present invention is also suitable as a method for regenerating and repairing the connection structure.

[0002]

2. Description of the Related Art Conventionally, as a method for electrically connecting an FPC (flexible printed circuit board) and a liquid crystal panel substrate, a film-shaped anisotropic conductive film in which conductive particles are dispersed and contained in an insulating resin. The method of connecting by thermocompression bonding is widely known.

By the way, in recent years, Clark et al. Have announced a ferroelectric liquid crystal device having a memory property in US Pat. No. 4,367,924. This ferroelectric liquid crystal device can be applied to a display panel by multiplexing drive proposed by Kamibe et al. In US Pat. No. 4,655,561 and is expected to realize a high-definition display with a large screen by the liquid crystal device. Has been done.

In the ferroelectric liquid crystal device described above, as revealed by Okada et al. In US Pat. No. 4,690,089, etc., in producing a monodomain orientation state, the isotropic phase is gradually cooled from the high temperature side. (About 5 ° C./hour), it was necessary to pass a cholesteric phase or a smectic A phase to generate a chiral smectic phase. Under the present circumstances, it is impossible to form a monodomain orientation state when the cooling process up to the chiral smectic phase or the temperature rising process up to the isotropic phase is rapidly performed.

Therefore, when the liquid crystal panel having the ferroelectric liquid crystal and the external control circuit are electrically connected, in the connection method using the thermocompression bonding process described above, the ferroelectric liquid crystal element is partially or entirely covered. Since the heated element is rapidly heated, and the heated element is rapidly cooled after releasing the thermocompression bonding, the orientation state of the monodomain may not be generated when returning to the chiral smectic phase. Such disorder of the alignment state can be restored to the original alignment state of the monodomain by performing a realignment treatment, but the anisotropic conductive adhesive containing a conventional thermoplastic resin as a main component is used. In the case of using, the reorientation process causes problems such as an increase in connection resistance. Therefore, as disclosed in U.S. Pat. No. 4,964,700, a method of electrically connecting with an anisotropic conductive adhesive using a thermosetting adhesive has been proposed.

[0006]

In an external connection circuit for connecting a liquid crystal panel having ferroelectricity and an external circuit,
Using the above-mentioned thermosetting anisotropic conductive adhesive is extremely effective. However, since the thermosetting anisotropic conductive adhesive is impossible or extremely difficult to regenerate and repair the external connection circuit that has become defective after thermosetting, the yield is lowered and the cost is increased. In addition, since the repair is performed after the external connection circuit is mechanically peeled off, the adhesive is swollen with a solvent such as MEK (methyl ethyl ketone) and peeled off with plastic tweezers, etc., and then repaired. It took a long time, and the rate of destruction of other parts during regeneration was high, which was unproductive.

The present invention has been made in view of the problems in the above-mentioned conventional example, and is a thermosetting resin containing conductive particles dispersedly contained in the driving electrodes of the liquid crystal panel and the external circuit for driving the liquid crystal panel. In the manufacturing method of the connection structure for connecting using, it is possible and easy to improve the yield or regenerate and repair the connection part of the liquid crystal panel and the external circuit without strict management of the environment and the conductive particles. The purpose is to

[0008]

In order to achieve the above object, in the present invention, an external circuit connecting electrode provided on a substrate of a liquid crystal panel and connected to a driving electrode of the liquid crystal panel,
Between the external circuit electrode connected to an external circuit for driving the liquid crystal panel provided outside the substrate, a cured body of a film formed of a thermosetting resin containing conductive particles dispersed therein is disposed, In the method for producing an external circuit connection structure of a liquid crystal panel for connecting these external circuit connection electrodes and external circuit electrodes, the conductor particles remaining in an undesired portion after the curing body is placed are melted and removed by laser light. It is characterized by doing.

In a preferred embodiment of the present invention, the external circuit electrode is a film carrier formed at a portion where the base film substrate is removed. The conductor particles are a low melting point alloy or metal such as solder. further,
The liquid crystal panel uses a ferroelectric liquid crystal.
In this case, the ferroelectric liquid crystal is preferably a chiral smectic phase formed by slowly cooling from an isotropic phase, particularly a chiral smectic C phase or an H phase, and the thickness of the chiral smectic liquid crystal is a The thickness is preferably set so as to eliminate the spiral structure inherent in the smectic phase.

[0010]

In the present invention, as described above, the external circuit connecting electrode and the external circuit electrode are connected by the thermosetting resin containing the conductive particles dispersed therein, and then the conductive particles remaining in the undesired portion are connected. Is melted and removed by laser light. Thereby, it is possible to easily prevent or short-circuit a short circuit between the external circuit connecting electrodes or between the external circuit electrodes due to the conductive particles remaining in an undesired portion.

[0011]

[First Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show a connection structure according to a first embodiment of the present invention. FIG. 1 is a sectional view and FIG. 2 is a plan view. In the connection structure shown, the substrate 2 of the liquid crystal panel 1
The external circuit connecting electrode 3 provided on the film carrier tape 4 is made of a transparent conductor such as ITO or tin oxide, and the external circuit electrode 5 provided on the film carrier tape 4 is made of copper foil with tin, nickel,
It is formed by plating with gold or the like. Reference numeral 6 is a driver IC for driving the liquid crystal panel. The anisotropic conductive adhesive 7 shown in the figure adheres a film formed of a thermosetting adhesive 9 containing conductive particles 8 dispersed therein under predetermined curing conditions (temperature, pressure, time).

In FIG. 1, a laser device 10 schematically shows a mode of irradiating a desired joining portion with a laser beam 11. An enlarged view of part A in FIG. 2 is shown in FIG. The external circuit connecting electrode and the external circuit electrode are aligned to form the electrode 12 and the space 13. At this time, the conductive particles of the electrode portion 12 are crushed and contribute to the connection, and the conductive particles of the space portion 13 are dispersed and contained. It exists in a dispersed state while maintaining the shape at the time.

However, especially when the connecting portion is miniaturized, the conductive particles cannot exist in the state of being dispersed in the space portion 13 especially when the foreign matter 14 and the like exist, and are arranged in a dam shape to electrically insulate the space portion 13. Will destroy.

Some of the above-mentioned foreign substances are attached to the anisotropic conductive adhesive generated from the human body and are suspended in the environment in which it is contained. When a connection portion of 10 lines / mm is to be formed, the space portion has a design center value of 50 μm. Therefore, in order to prevent dielectric breakdown of this space portion, variations in the formation of the external circuit electrode and the connection between the external circuit electrode and the external circuit are required. Considering the displacement of the working electrodes during alignment, it is practically necessary to manage and remove foreign matter of 20 μm or more, which is impossible in practice.

However, as described above, since the thermosetting anisotropic conductive adhesive is used for connecting the liquid crystal having the ferroelectricity, conventionally, the yield is lowered as a defect, or
As described above, it takes a great deal of time to repair and repair, that is, after mechanically peeling off the external connection circuit, and then peeling it off with plastic tweezers while swelling the adhesive with a solvent such as MEK (methyl ethyl ketone). I was doing repair repairs.

On the other hand, in the present embodiment, the YAG laser was irradiated with 20 μm square and 6 mJ three times, whereby the conductive particles could be removed and repaired.

Further, among the conductive particles, conductive particles 1 having an abnormal diameter are used.
5 exists, the electrodes 3 and 5 which should not be connected originally
The two are connected across the space portion 13. In order to prevent this, in the case of a connection part of 5 lines / mm level, 35 μm or less
It is necessary to control the diameter of the conductive particles to 25 μm or less. This is because the thickness of the external circuit electrode of the film carrier is
In the case of the 5 lines / mm level connection portion at 35 [mu] m ^t, 10 lines / mm level connection but by that a 18~25μm ^t, the conductive particles dispersed contained in the anisotropic conductive adhesive by the value It is practically impossible to manage.

In the present embodiment, the diameter control of the conductive particles is carried out according to the conventional standard, and after the connection process is performed, the particles having an abnormal diameter cause an insulation failure, whereas the YAG laser 20 μm × 50 μm square, 6 mJ. By conducting the irradiation of 3 times, the conductive particles having an abnormal diameter were removed and a repair was performed.

[0020]

Second Embodiment FIGS. 4 and 5 show a second embodiment of the present invention. The difference of this embodiment from the first embodiment is that the film carrier tape 4 at the connecting portion is removed and the external circuit electrode 5 is overhanged. In this embodiment, FIG.
As shown in (1), the laser beam can be irradiated from the side corresponding to the side of the film carrier tape of the first embodiment, and the conductive particles are more likely to be scattered, and there is an advantage that the repair is facilitated. However, the repair and repair were carried out under the same conditions as in the first embodiment.

[0021]

Modified Example of the Embodiments In the first and second embodiments described above, solder is used as the conductive particles. Since the melting point of solder is low, the energy of laser light is low, and there is an advantage that the thermal effect adhesive is less damaged. It is also possible to use a low melting point metal such as In as the conductive particles.

[0022]

As described above, according to the present invention,
In a connection structure that uses a thermosetting anisotropic conductive adhesive to connect the liquid crystal panel and an external circuit, the conductive particles remaining in undesired parts are melted and removed by laser light. (1) Easy reconditioning (2) Yield was improved, (3) It was not necessary to make environmental foreign matter management more rigorous than necessary, and equipment investment was reduced. (4) Foreign matter of anisotropic conductive adhesive, particles of abnormal diameter It is no longer necessary to make the removal more severe than necessary, and the cost can be reduced. (5) The industrial effect is extremely large, such as enabling a fine connection pitch at a practical level.

[Brief description of drawings]

FIG. 1 is a sectional view of a connection structure according to a first embodiment of the present invention.

FIG. 2 is a plan view of the first embodiment of the present invention.

FIG. 3 is an enlarged view of the first embodiment of the present invention.

FIG. 4 is a sectional view of a connection structure according to a second embodiment of the present invention.

FIG. 5 is a plan view of the second embodiment of the present invention.

[Explanation of symbols]

1: Liquid crystal panel, 2: Liquid crystal panel substrate, 3: External circuit connection electrode, 4: Film carrier tape (substrate separate from substrate 2), 5: External circuit electrode, 6: Driver IC,
7: anisotropic conductive adhesive, 8: conductive particles, 9: thermosetting adhesive, 10: laser device, 11: laser light, 12:
Electrodes (external circuit connection electrodes and external circuit electrodes), 1
3: Space (undesired part), 14: Foreign matter, 15: Conductive particles with abnormal diameter.

Claims (7)

[Claims] 1. To connect an external circuit for driving a liquid crystal panel to a driving electrode of a liquid crystal panel, the external circuit connecting electrode provided on a substrate of the liquid crystal panel and connected to the driving electrode and the external circuit are connected. Manufacture an external circuit connection structure for liquid crystal panels by aligning the position of the connected external circuit electrodes and arranging a cured film of a film formed of a thermosetting resin containing dispersed conductive particles between those electrodes. The method for manufacturing an external circuit connection of a liquid crystal panel according to the method, wherein the conductive particles remaining in an undesired part are melted and removed by a laser beam after the cured body is arranged. 2. The manufacturing method according to claim 1, wherein the external circuit electrode is a film carrier formed in a portion where the base film substrate is removed. 3. The method according to claim 1, wherein the conductor particles are a low melting point alloy such as solder or a metal. 4. The manufacturing method according to claim 1, wherein the liquid crystal panel uses a ferroelectric liquid crystal. 5. The method according to claim 4, wherein the ferroelectric liquid crystal is a chiral smectic phase formed by gradually cooling an isotropic phase. 6. The manufacturing method according to claim 5, wherein the film thickness of the chiral smectic liquid crystal is set to be thin enough to eliminate the spiral structure inherent to the chiral smectic phase in the absence of an electric field. 7. The method according to claim 5, wherein the chiral smectic phase is a chiral smectic C phase or an H phase.