JPH04171423A - Liquid-crystal display device - Google Patents

Abstract

PURPOSE:To improve reliability on connection between an output electrode located at both ends of a printed circuit board and a terminal electrode for a liquid-crystal display element by functioning the connection of an auxiliary electrode to the extended terminal electrode and the connection of a recognition marker to the extended terminal electrode as a dummy pattern to thermal stress. CONSTITUTION:The connection of an extended terminal electrode 13 to auxiliary electrodes 25, 26 is in a conductive condition to the connection of an output electrode located at both ends of a printed circuit board to an element electrode 13 for a liquid-crystal display element 10. This allows the connection to increase the number of conductive particles 30a which contribute to connection between the output electrode 23 located at both ends of the printed circuit board 20 and the terminal electrode 13 for the liquid-crystal display element 10 and also to function as a dummy pattern to thermal stress. It is thus possible to improve reliability on connection between the output electrode 23 located at both ends of the printed circuit board 20 and the terminal electrode for the liquid-crystal display element 10.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a TA B equipped with an integrated circuit bare chip.
(Tape Automated Bonding),
Or FPC (Flexible Printed
The present invention relates to a liquid crystal display device in which a printed circuit board such as C4rcuit and a liquid crystal display element are connected via an anisotropic conductive film.

[Prior Art] In recent years, liquid crystal display devices incorporating integrated circuits have become smaller and smaller.
With the promotion of high performance and high functionality, it is expected that the packaging density will further increase.In order to meet these expectations, the connection between integrated circuits and liquid crystal display elements will be made using printed circuits such as TAB or FPC. Structures using substrates are becoming more common.

For example, in conventional liquid crystal display devices, TABs are used to package integrated circuits. That is, a liquid crystal display device includes a liquid crystal display element and a large number of TABs that constitute a driver for driving the liquid crystal display element. In the TAB, a bare chip as an integrated circuit is mounted on a base film, and this bare chip is connected to a TAB electrode as an output electrode formed on a heat film.

The connection between the TAB and the liquid crystal display element is
This is accomplished by heat-pressing an anisotropic conductive film between the TAB electrode of the liquid crystal display element and a transparent electrode serving as a terminal electrode of the liquid crystal display element.

In addition, in the anisotropic conductive film, conductive particles such as metal particles such as carbon or Ni, or metal-plated Plasdec particles are made of thermoplastic resin such as ester resin, or thermosetting resin such as epoxy resin. It is dispersed in a transparent resin, and provides insulation between adjacent electrodes such as between each TAB electrode or between each transparent electrode, while providing insulation between the opposing electrodes of the TAB electrode and the transparent electrode. Conductive particles are sandwiched between them to form a current-carrying path, thereby imparting conductivity.

[Problems to be Solved by the Invention] However, as described above, the anisotropic conductive film used to electrically connect the TAB and the liquid crystal display element cannot be used - When fishing on a boat, conductive particles are mixed in a solvent such as toluene. After being dispersed, the conductive particles are stirred and dispersed together with the resin component using a ball mill, etc.
Thereafter, in order to make the particle size of the conductive particles uniform, a method is adopted in which the conductive particles are sorted and purified through a filter. Therefore, when stirring the conductive particles in the resin as described above,
When the concentration of conductive particles in the resin is high, secondary aggregation between the conductive particles tends to occur due to the high concentration, and as a result, when connecting the TAB and the liquid crystal display element, the difference between adjacent electrodes increases. A leak will occur. For this reason, there is a need to limit the concentration of conductive particles in the resin, especially in the connection between the TAB and the liquid crystal display element, which requires a high-definition connection pitch.

However, while limiting the concentration of conductive particles in the resin as described above avoids the occurrence of leakage between adjacent electrodes, it also prevents leakage between the TAB electrode of the TAB and the transparent electrode of the liquid crystal display element. This will reduce the number of conductive particles. This means that when heat is applied to the connection between the TAB electrode and the transparent electrode, thermal stress is particularly likely to be applied to both ends of the TAB, causing the TAB to expand and contract due to the heat. There is a serious problem in terms of connection reliability in that a peeling phenomenon occurs locally between the TAB electrode and the transparent electrode located on the side, which in turn leads to disconnection between the TAB electrode and the transparent electrode.

In addition, the above-mentioned disconnection between the TAB electrode and the transparent electrode due to heat,
High temperature/high temperature (40°C/95%RH~60°C/95%R
This was confirmed by the connection reliability test in H), and in addition to the above-mentioned peeling phenomenon between the TAB electrode and transparent electrode, an increase in connection resistance due to thermal stress is also a cause of disconnection. It has become.

[Means to solve the problem]

In order to solve the above problems, a liquid crystal display device according to the present invention has a bare chip of an integrated circuit on a base film, and a plurality of output electrodes connected to each terminal of this bare chip are arranged in parallel on the base film. and a liquid crystal display element formed with a plurality of terminal electrodes corresponding to the plurality of output electrodes, wherein the output electrodes of the printed circuit board and the terminal electrodes of the liquid crystal display element are different from each other. In a liquid crystal display device connected via conductive particles in a directional conductive film, the following measures are taken.

That is, in the printed circuit board, recognition markers for positioning with the liquid crystal display element are provided at both ends of the Haas film, and an auxiliary electrode is provided between the recognition marker and the output electrode. The liquid crystal display element is arranged in parallel with the electrodes, and the terminal electrodes corresponding to the output electrodes located at both ends of the printed circuit board correspond to the recognition marker and auxiliary electrode of the printed circuit board, respectively. The distal end portion is extended.

[For production]

According to the above configuration, the auxiliary electrodes are provided on the sides of the output electrodes located at both ends of the printed circuit board, and the terminal electrodes of the liquid crystal display element are extended to correspond to the auxiliary electrodes. The terminal electrode and the auxiliary electrode are connected via conductive particles in the anisotropic conductive film, similar to the connection between the terminal electrode of a liquid crystal display element and the output electrode of a printed circuit board. In addition, the connection portion between the extended terminal electrode and the auxiliary electrode as described above is electrically connected to the connection portion between the output electrode located at both ends of the printed circuit electrode and the terminal electrode of the liquid crystal display element. In turn, such a connection increases the number of conductive particles that contribute to the connection between the output electrodes located at both ends of the printed circuit board and the terminal electrodes of the liquid crystal display element, and also functions as a dummy pattern against thermal stress. This improves the connection reliability between the output electrodes located at both ends of the printed circuit board and the terminal electrodes of the liquid crystal display element.

Furthermore, by providing recognition markers on both ends of the base film that constitutes the printed circuit board, it is possible to connect the liquid crystal display element and the printed circuit board as described above with high precision. By extending the terminal electrodes of the liquid crystal display element with respect to the recognition marker, the number of conductive particles contributing to the connection between the output electrodes located at both ends of the printed circuit board and the terminal electrodes of the liquid crystal display element can be further reduced. can be increased.

[Example] An example of the present invention will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 3, the liquid crystal display device according to this embodiment has the following features:
It is composed of a liquid crystal display element 10 and a large number of TABs 20 as printed circuit boards constituting a driver for driving the liquid crystal display element 10.

The TAB 20 has a base film 21 made of a thin organic film, and a bare chip 22 as an integrated circuit is mounted on this base film 21, as well as a plurality of output electrodes as shown in FIG. T as
AB electrodes 23 are connected to respective terminals (not shown) of the bare chip 22. Above T'A B electrode 2
3... are arranged in parallel on the base film 21 at predetermined intervals, and their materials include, for example:
A material made of Cu coated with tin plating is used.

Further, in the TAB 20, recognition markers 24, 24 for positioning in connection with the liquid crystal display element 10 are provided on both end portions 21a, 21a of the base film 21, respectively, and these recognition markers 24, 24, 2
4 to output electrodes 23 and 23 located at both ends of the liquid crystal display element 10, two auxiliary electrodes 25 and 26 are provided.

The recognition marker 24 has a first approximately square shape when viewed from above.
3 markers 24a and 24c, and a second marker arranged between these first and third markers 24a and 24c and having a rectangular shape in plan view.
It is composed of a marker 24b, and the first, second, and
As shown in FIG. 2, the three markers 24a, 24b, and 24c are each formed in a convex manner on the lower surface of the base film 21, similar to the TAB electric FIi 23.

Further, the auxiliary electrodes 25 and 26 are respectively TAB electrodes 2
3, it is connected to a terminal (not shown) of the bare chip 22, and is also formed to protrude convexly from the lower surface of the base film 21.

On the other hand, the liquid crystal display element 10 has a rectangular glass substrate 11, and connection portions 12 to the TAB 20 are formed on each of three sides of the glass substrate 11'. In addition, as shown in FIG. 1, the connecting portion 12 includes
For example, ITO (Indium
Transparent electrodes 13 made of (tin oxide) or the like are formed on the glass substrate 11 at predetermined intervals so as to correspond to the TAB electrodes 23 described above.

Among the transparent electrodes 13..., those located at both ends have their tip portions extended to form recognition end portions 13a corresponding to the aforementioned recognition markers 24, and Auxiliary end portions 13b and 13c are formed corresponding to each of the auxiliary electrodes 25 and 26, respectively. The recognition end 13a has a shape along the outer periphery of each of the first, second, and third markers 24a, 24b, and 24c constituting the recognition marker 24 so as to align with the recognition marker 24 of the TAB 20. It is formed of.

The connection between the liquid crystal display element 10 and the TAB 20 is achieved by forming a conductive film formation region made of an anisotropic conductive film 30 such as AC-6101 manufactured by Hitachi Chemical Co., Ltd., on the connection portion 12 of the liquid crystal display element 10. Then, the transparent electrode 13 of the liquid crystal display element 10 and the TAB electrode 23 of the TAB 20...
- Heat compression bonding is performed by applying a pressure of, for example, 20 kg/cn from the base film 21 side of the TAB 20 at a temperature of 190°C for 20 seconds while the liquid crystal display element 10 and the TAB 20 are facing each other. Circuit connections are made.

In the anisotropic conductive film 30, as shown in FIG. 2, conductive particles 30a having an average particle diameter of about 10 μm, such as metal particles such as carbon or Ni, or metal-plated plastic particles, are made of ester. It is dispersed in a thermoplastic resin such as a thermoplastic resin, or a thermosetting resin such as an epoxy resin, and is used between each TAB electrode 23 or between adjacent electrodes between each transparent electrode 13. The conductive particles 30a are sandwiched between the corresponding electrodes of the TAB electrode 23 and the transparent electrode 13 to provide conductivity by forming a conductive path. It has become.

In the above configuration, the distal end portion is extended and the recognition end portion 13
The transparent electrode 13 of the liquid crystal display element 10 on which the auxiliary end portions 13b and 13c are formed has the TAB electrode 23 of the TAB 20 and the conductive particles 30a, similar to other transparent electrodes 13 whose tip portions are not extended. as well as being connected through
The recognition end 13a and the auxiliary ends 13b and 13c are connected to the recognition marker 24 and auxiliary electrodes 25 and 26 of the TAB 20, respectively, via conductive particles 30a.

In addition, the connection portion between the recognition marker 24 and the recognition end portion 13a of the transparent electrode 13 as described above, and each auxiliary electrode 25, 2
6 and each auxiliary end portion 13b and 13c of the transparent electrode 13 are electrically connected to the connection portion between the TAB electrode 23 located at both ends of the TAB 20 and the transparent electrode 13 of the liquid crystal display element 10, respectively.

Therefore, the TAB electrodes 23 located at both ends of the TAB 20
The number of conductive particles 30a contributing to the connection in the connection part between the TAB electrode 23 and the transparent electrode 13 of the liquid crystal display element 10 is higher than that in the connection part between the other TAB electrodes 23 and the transparent electrode 13.
and the connection portion between the recognition end portion 13a of the transparent electrode 13, and each of the auxiliary electrodes 25 and 26 and each auxiliary end portion 13b of the transparent electrode 13.
・The increase in the number of conductive particles 30a, which is connected to 13C, improves the connection reliability in the connection between the liquid crystal display element 10 and the TAB 20 at both ends, which are easily affected by heat stress. It is something that makes you

Note that the connection reliability between the liquid crystal display element 10 and the TAB 20 can be improved by increasing the connection reliability between each transparent electrode 13 or between each TAB.
Between the adjacent electrodes between the B electrodes 23..., the inter-electrode pitch is set to a high-definition pattern of 120 μm, and 6
This was confirmed as a result of a 500 hour durability test under a high temperature environment of 0°C and 95% RH.

Furthermore, in the connection between the liquid crystal display element 10 and the TAB 20 at the high-definition connection pitch as described above, in this liquid crystal display device, '' is applied to both end portions 21a and 21a of the heath film 21 constituting the TAB 20. 24 recognition markers each.
24 makes it possible to maintain alignment accuracy between the liquid crystal display element 10 and the TAB 20.

Note that the above embodiments do not limit the present invention, and various changes can be made within the scope of the present invention. For example, T.A.
Two auxiliary electrodes 25 and 26 are provided between the recognition marker 24 of B20 and the TAB electrodes 23 located at both ends, but the invention is not particularly limited to this.
In such a case, the transparent electrode 13 of the liquid crystal display element 10
It is possible to change the extension shape of the tip.

〔Effect of the invention〕

As described above, in the liquid crystal display device according to the present invention, the printed circuit board is provided with recognition markings for positioning with the liquid crystal display element at both ends of the base film, respectively, and the printed circuit board is provided with recognition markings for alignment with the liquid crystal display element. Between the recognition marker and the output electrode, an auxiliary electrode is arranged in parallel to the output electrode, and the liquid crystal display element has terminal electrodes corresponding to the output electrodes located at both ends of the printed circuit board, respectively. , a recognition marker on a printed circuit board, and an auxiliary electrode.

As a result, the connection between the auxiliary electrode and the extended terminal electrode, and the connection between the recognition marker and the extended terminal electrode are connected to the output electrode and the terminal of the liquid crystal display element located at both ends of the printed circuit board. This means that it is electrically connected to the connecting part. Therefore, the number of conductive particles contributing to the connection between the output electrodes located at both ends of the printed circuit board and the terminal electrodes of the liquid crystal display element is increased, and the number of conductive particles contributing to the connection between the auxiliary electrodes and the extended terminal electrodes is increased. The connecting portion between the recognition marker and the extended terminal electrode functions as a dummy pattern against thermal stress, thereby improving the connection reliability between the output electrode located at both ends of the printed circuit board and the terminal electrode of the liquid crystal display element. can be improved. In addition, in the connection between a printed circuit board and a liquid crystal display element, which requires high-definition connection pinch as described above, there is a
Providing recognition markers for each has the effect that connection accuracy can be maintained.

[Brief explanation of the drawing]

FIG. 1 to FIG. 3 show an embodiment of the present invention. FIG. 1 is an enlarged plan view showing a connecting portion between a liquid crystal display element and a TAB. FIG. 2 is a sectional view taken along the line A--A in FIG. 1. FIG. 3 is a plan view showing the liquid crystal display device. 10 is a liquid crystal display element, 13 is a transparent electrode (terminal electrode), 2
0 is TAB (printed circuit board), 21 is a base film, 21a is a terminal part, 22 is a bare chip, 23 is a TAB electrode (output electrode), 24 is a recognition marker, 25 is an auxiliary electrode, 30 is an anisotropic conductive film , 30a are conductive particles.

Claims (1)

[Scope of Claims] 1. A printed circuit board having a bare chip of an integrated circuit on a base film, and a plurality of output electrodes connected to each terminal of the bare chip arranged in parallel on the base film; and a liquid crystal display element in which a plurality of terminal electrodes corresponding to each other are formed, and the output electrode of the printed circuit board and the terminal electrode of the liquid crystal display element are connected to each other through conductive particles in an anisotropic conductive film. In a liquid crystal display device connected to In between, auxiliary electrodes are arranged in parallel to the output electrodes, and in the liquid crystal display element, output electrodes and corresponding terminal electrodes located at both ends of the printed circuit board are respectively connected to recognition markers of the printed circuit board. , and a liquid crystal display device characterized in that a tip portion is extended to correspond to an auxiliary electrode.