JPH04242721A - Liquid crystal display unit - Google Patents

Abstract

PURPOSE:To mount an IC for driving to a liquid crystal display unit at a low cost and in a short process. CONSTITUTION:A lead electrode 33a formed on a base film 32 is connected with an IC 4 for driving through an anisotropic conductive film preliminarily formed on the lead electrode 33a. An IC 4 output side end electrode 33b of a lead 33 on time base film 32 is connected with a wiring electrode 15 on a glass substrate 12 of a liquid crystal display panel 11. An IC 4 input side end electrode 33c of the lead 33 on the base film 32 is connected with an electrode 22 on a circuit board 21 through the same anisotropic conductive film.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to the structure of a connecting portion when a liquid crystal driving IC is electrically connected to the liquid crystal display device.

0003

2. Description of the Related Art A method for mounting a driving IC on a liquid crystal display device is described in "Flat Panel Display '90", edited by Nikkei BP, p. 242, (1989), TAB (Tape Automated Bon
ding) method, and COG (Chip on Gla
ss) method is mainly used.

[0004] Regarding the TAB method, FIGS.
This will be explained with reference to 0.

FIG. 8 is a plan view of the tape carrier 1. As shown in FIG. 9, which is a partial cross-sectional view of a liquid crystal display device, this tape carrier 1 has a large number of leads 3 made of tin-plated copper formed on a base film 2 made of polyimide. . First, the electrodes 3a at the tips of these leads 3 and the bumps 5 made of gold on the driving IC 4 are metallurgically connected using a bonder (not shown) (ILB: Inner Lead Bondi).
ng), the driving IC 4 is mounted on the tape carrier 1. Thereafter, the driving IC 4 is sealed with a resin (not shown), and then the tape carrier 1 is punched out into a desired shape. Hereinafter, the product punched into this shape will be referred to as TAB-IC6.

In FIG. 9 and FIG. 10 which is a plan view of a liquid crystal display device, 11 is a liquid crystal display plate, and this liquid crystal display plate 11 is formed by holding a liquid crystal 14 between a pair of glass substrates 12 and 13. It is. Further, 21 is a printed circuit board (hereinafter abbreviated as PCB).

[0007] As shown in FIGS. 9 and 10,
The IC output end side electrode 3b of the lead 3 of the TAB-IC 6 and the wiring electrode 15 made of aluminum or ITO (Indium Tin Oxide) formed on the periphery of the liquid crystal display board 11 are connected by an anisotropic conductive film 16. (OLB: Outer Lead Bo)
nding). Next, the IC input end side electrode 3c of the lead 3 and the electrode 22 formed on the PCB 21 are connected to each other.
Connect by soldering. Here, the leads 3 on the TAB-IC 6 are protected by a solder resist 7 in a desired pattern.

[0008] Through the above steps, the driving IC 4 is TAB mounted on the liquid crystal display board 11.

Next, the COG method, particularly the COG method using the face-down bonding method, will be explained with reference to FIGS. 11 and 12.

The COG method using the face-down bonding method is a method in which the driving IC 4 is directly connected to the wiring electrodes 15a and 15b on the liquid crystal display board 11, as shown in FIG. 11, which is a partial cross-sectional view of the liquid crystal display device. , and is characterized in that the tape carrier 1 of the member is unnecessary. Here, 15a and 15b are driving ICs, respectively.
These are wiring electrodes corresponding to the output side and input side of No. 4. The method for connecting the drive IC 4 is described in "Nikkei Micro Devices", July 1989 issue, no. 49, p. 107, various methods are known, but usually the bump 5 and the wiring electrodes 15a, 15b are electrically connected via a connecting metal or alloy such as silver paste. .

[0011] Also, an IC input end side wiring electrode 15b,
The electrode 22 of the PCB 21 must be connected by some method, but the connection between them is usually as shown in FIG.
Also, as shown in FIG. 12, which is a plan view of the liquid crystal display board,
Flexible printed circuit (hereinafter abbreviated as FPC)
26. That is, the IC input end side wiring electrode 15b on the glass substrate 12 and the lead 27 formed on the FPC 26 are connected via the anisotropic conductive film 28. Further, the leads 27 of the FPC 26 and the electrodes 22 on the PCB 21 are connected by soldering.

The conventional mounting methods using the TAB method and the COG method described above have the following drawbacks.

In the TAB method, a driving IC 4 is placed on a tape carrier 1 made of a polyimide base film 2.
It is installed by implementing ILB. Therefore, a tape carrier 1 is required, which increases the material cost accordingly. Further, ILB is performed metallurgically by forming a gold/tin eutectic, and the temperature at that time is usually as high as 500°C. That is, a high temperature process is required. Furthermore, a sheet-like material must be separately prepared as the anisotropic conductive film 16 and inserted between the wiring electrode 15 on the glass substrate 12 and the punched-out TAB-IC 6. Therefore, the material cost increases, and it is necessary to fix the anisotropic conductive film 16, resulting in a longer process. on the other hand,
In the COG method, as shown in FIG. 12, since the IC2 must be mounted on the glass substrate 12, the driving IC4
The size of the glass substrate 12 must be increased by the area in which it is mounted. In addition, for the connection between the IC input end side wiring electrode 15b and the electrode 22 of the PCB 21,
Since the FPC 26 must be prepared, the material cost increases accordingly. Furthermore, the FPC 26 and the IC input end side wiring electrode 1
5b must be connected via a separately prepared anisotropic conductive film 28, as in the case of the TAB method,
The disadvantages are higher material costs and longer processes.

[0014]

[Problems to be Solved by the Invention] As described above, the conventional TAB method for mounting a liquid crystal display device requires tape and
The disadvantages are that a carrier 1 is required, the material cost is high, an expensive bonder is required for the metallurgical connection, the process is high temperature, and the process is long. On the other hand, in the mounting method using the COG method, the size of the glass substrate 12 becomes large. Furthermore, in the connection between the wiring electrode 15b on the glass substrate 12 and the electrode 22 on the PCB 21,
In addition to having to prepare the FPC 26, it is also necessary to separately prepare an anisotropic conductive film 28 and solder (not shown) for connection, which has the disadvantage of increasing material costs and lengthening the process.

The present invention was developed in view of the above-mentioned shortcomings of the prior art, and makes use of the advantages of both the TAB method and the COG method, and also makes it possible to implement a driving IC at low cost and in a short process. The object of the present invention is to provide a highly reliable liquid crystal display device.

[Configuration of the invention]

[0017]

[Means for Solving the Problems] In the liquid crystal display device according to the present invention, the lead electrodes of the leads formed on the base film are connected to the face via the anisotropic conductive film formed on the lead electrodes. Connected to the drive IC at the down level. At the same time, the output side end electrode and the input side end electrode of the drive IC of the leads on the base film are connected to the liquid crystal display through an anisotropic conductive film of the same layer as the anisotropic conductive film. It is connected to wiring electrodes formed around the glass substrate of the display panel and electrodes formed on the circuit board.

[0018]

[Operation] The liquid crystal display device according to the present invention has connections between the driving IC and the lead electrodes on the base film, and connections between the wiring electrodes on the periphery of the glass substrate of the liquid crystal display board and the lead electrodes on the base film. , and the electrodes on the circuit board and the electrodes of the leads on the base film are connected through the same layer of anisotropic conductive film formed on the leads on the base film. Since each connection point is formed of the same connection material, the driving IC can be mounted in a short process, and a liquid crystal display device can be provided at low cost. Further, since the connection is made using an anisotropic conductive film, a highly reliable liquid crystal display device can be provided by a low temperature process of about 150°C.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the liquid crystal display device of the present invention will be described in detail below with reference to FIGS. 1 to 7.

FIG. 5 is a sectional view of the FPC 31 (hereinafter referred to as connector 31) used in this embodiment, and FIG. 6 is a side view of the connector 31. First, the structure of this connector 31 will be explained.

The base film 32 has a thickness of, for example, 2
It is a 5μmt polyester film. A copper lead 33 having a thickness of, for example, 17 μm is formed on this base film 32, and a desired circuit pattern is drawn thereon. Further, an anisotropic conductive film 34 is provided on the lead 33.
is formed over the entire surface by, for example, a printing method. This anisotropic conductive film 34 is made of, for example, a thermosetting resin in which nickel particles are dispersed. For example, the film thickness is 20μ
mt, and the particle size of the nickel particles is about 3 μm. Furthermore, a protective film 35 is formed on the anisotropic conductive film 34, with only the connection portions to be described later removed. As this protective film 35, for example, a polyester film with a thickness of 12 μm is used.

[0022] The number of outputs of the liquid crystal driving IC4 is, for example, 120.
It is. The size of the bumps 5 on this IC 4 is approximately 90 μm square, and the pitch of these bumps 5 is, for example, 160 μm. The surface area of the IC 4 other than the bumps 5 is protected by a passivation film formed of two layers of phosphor glass and silicon nitride in this order.

The liquid crystal display panel 11 includes a pair of glass substrates 12.
, 13, a liquid crystal 14 is held between them. In the description of this embodiment, an example will be described in which the wiring electrode 15 formed on the periphery of the glass substrate 12 has a surface layer formed with chromium and aluminum in this order. Here, the film thicknesses of chromium and aluminum are, for example, 50
nm, 400 nm. Further, the pitch of the wiring electrodes 15 is, for example, 230 μm.

The PCB 21 has passive components, control ICs, etc. (not shown) mounted on a circuit board made of glass epoxy resin. The electrodes 22 formed on the PCB 21 are made of copper, and the pitch thereof is, for example, 0.
It is 7mm.

Next, the mounting of the driving IC 4 will be explained based on FIGS. 1 to 4, which are partial cross-sectional views of the liquid crystal display device.

First, the driving IC 4 is mounted face down on the connector 31. At this time, first, the bumps 5 of the IC 4 and the lead electrodes 33a of the leads 33 exposed through the openings of the protective film 35 of the connector 31 are aligned. Note that these lead electrodes 33a
The pitch of bump 5 is 160 μm, which is the same as the pitch of bump 5.
Of course, it is. Next, connect connector 3 using a pulse heat bonder (not shown).
A load of approximately 6 kg (approximately 50 g
/pad), and held at a temperature of 150° C. for about 30 seconds while applying pressure and heating with a bonder tool. When the temperature of the bonder tool has decreased, if it is released, the bump 5 on the IC 4 and the lead electrode 33a on the connector 31 will be different, as shown in FIG. 1 and FIG. 3, which is an enlarged view of a part thereof. Connection all at once via the directional conductive film 34 (ILB)
be done. In order to protect the IC 4 mounted on the connector 31, although not shown, the IC 4 may be potted with silicone resin or the like. Next, IC4
The connector 31 on which is mounted is punched out into a shape as shown in FIG. 7, which is a plan view of the liquid crystal display device.

Next, the output side end electrode 33b of the drive IC 4 in the lead 33 of the connector 31 where ILB has been completed is as shown in FIG. 1, FIG. 2 which is an enlarged view of a part thereof, or FIG. The wiring electrodes 15 of the glass substrate 12 of the liquid crystal display board 11 are connected via the anisotropic conductive film 34 of the same layer as when the driving IC 4 is connected (O
LB) Do it. At this time, the connection can be made using the same bonder as when mounting the above-mentioned IC4, and using almost the same method and conditions. However, the bonder stage is changed from one for IC4 to one for mounting liquid crystal display board 11. Also, replace the head of the bonder tool from one for IC4 to a long and narrow one with a width of about 3mm.

Next, the input side end electrode 33c of the drive IC 4 in the lead 33 of the connector 31 where OLB has been completed is connected to the electrode on the PCB 21, as shown in FIG. 1 and FIG. 4 which is an enlarged view of a part thereof. 22 through an anisotropic conductive film 34 of the same layer as when the driving IC 4 is connected. At this time, although not shown, the connection can be made using substantially the same method and conditions by simply preparing bonder heads of different lengths.

Through the above process, the driving IC 4 can be mounted on the liquid crystal display board 11 using the connector 31, as shown in FIG.

According to the configuration of the above embodiment, the driving IC 4
and the lead electrode 33a of the connector 31, the connection between the wiring electrode 15 of the glass substrate 12 of the liquid crystal display panel 11 and the electrode 33b of the connector 31, and the connection between the electrode 22 on the printed circuit board 21 and the electrode 33c of the connector 31.
Since the connection is made through the anisotropic conductive film 34 of the same layer formed on the leads 33 of the connector 31, the driving IC 4 can be mounted at low cost. In addition, since the anisotropic conductive film 34 is formed on the connector 31 in advance, the IC 4 can be mounted in a short process. Further, since the connection is made using the anisotropic conductive film 34 as a connection material, a highly reliable liquid crystal display device can be provided by a low temperature process of about 150°C.

In fact, the liquid crystal display device obtained by the above-mentioned process was subjected to mechanical tests required for liquid crystal display devices, such as thermal shock tests, high temperature and high humidity tests, high temperature tests, temperature and humidity cycle tests, vibration tests, and impact tests. When evaluated through various reliability tests, there were no problems caused by the connections.

Furthermore, in the above embodiment, the anisotropic conductive film 34
Although the detailed explanation has been given by taking as an example the case where the conductive particles therein are nickel particles, in the case where the wiring electrode 15 is an ITO electrode, the connector 31 having solder particles as the conductive particles in the anisotropic conductive film 34 may be used. If used, the present invention can be applied.

Further, in the above embodiment, the anisotropic conductive film 34 in the connector 31 is printed on the entire surface, but the anisotropic conductive film 34 is printed only on the connection portions on the leads 33. It goes without saying that the present invention is also applicable to the case where such a structure is formed.

Further, in the above embodiment, the case where the connector 31 is used without being bent was explained in detail, but since the connector 31 is flexible, although not shown in the drawings,
Of course, the present invention is also applicable to the case where the connector 31 is used by being bent. In addition, connector 3
1 and position the driving IC 4 below the PCB 21, the size of the glass substrate 12 and the PCB 21 can be reduced.

Further, in the above embodiments, the case where the material of the base film 32 is a polyester film has been described in detail, but the present invention can also be applied to cases where the material is other materials such as Kapton. Of course.

[0036]

[Effects of the Invention] According to the present invention, the driving IC and the base
Connection with the lead electrode on the film, connection between the wiring electrode on the glass substrate of the liquid crystal display panel and the electrode on the base film,
In addition, since the electrodes on the circuit board and the electrodes on the base film are connected through the same layer of anisotropic conductive film formed on the leads on the base film, it can be done in a short process. , it is possible to provide a high-yield, low-cost liquid crystal display device. Furthermore, since an anisotropic conductive film is used in all connections, a highly reliable liquid crystal display device can be provided using a low temperature process.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing an embodiment of a liquid crystal display device of the present invention.

FIG. 2 is an enlarged view of section a in FIG. 1;

FIG. 3 is an enlarged view of part b in FIG. 1;

FIG. 4 is an enlarged view of section c in FIG. 1;

FIG. 5 is a sectional view of the connector used in the embodiment.

FIG. 6 is a side view of the connector.

7 is a plan view of the entire liquid crystal display device shown in FIG. 1. FIG.

8 is a plan view of a tape carrier used in the liquid crystal display device shown in FIG. 9; FIG.

FIG. 9 is a partial cross-sectional view showing an example of a conventional liquid crystal display device.

10 is an overall plan view of the liquid crystal display device shown in FIG. 9. FIG.

FIG. 11 is a partial cross-sectional view showing another example of a conventional liquid crystal display device.

12 is a plan view of the entire liquid crystal display device shown in FIG. 11. FIG.

[Explanation of symbols]

4 Drive IC 11 Liquid crystal display board 12 Glass substrate 15 Glass substrate wiring electrode 21 Circuit board 22 Circuit board electrode 32 Base film 33 Lead 33a Lead electrode 33b Lead's output side end electrode 33 of drive IC
c Lead end electrode 34 on the input side of the drive IC
Anisotropic conductive film

Claims (1)

[Claims] 1. A lead electrode of a lead formed on a base film is connected face-down to a driving IC via an anisotropic conductive film formed on the lead electrode, and the base film is connected face-down to a driving IC. The output side end electrode and the input side end electrode of the drive IC of the leads on the film are connected to each other through an anisotropic conductive film of the same layer as the anisotropic conductive film,
A liquid crystal display device characterized in that the liquid crystal display device is connected to wiring electrodes formed on and around a glass substrate of a liquid crystal display board and electrodes formed on a circuit board.