JP3250000B2 - Terminal connection structure of liquid crystal display panel and terminal connection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to a TCP (Tape Carrier).
Package, hereinafter simply referred to as TCP), FPC (Flexible P
The present invention relates to a technique for connecting electrode terminals of a flexible circuit board such as a rinted circuit (hereinafter simply referred to as FPC) to electrode terminals of a liquid crystal display panel.

[0002]

2. Description of the Related Art With the development of a highly information-oriented society, there have been remarkable technological advances in the field of liquid crystal display panels.
In addition, with the recent increase in size, precision, and reliability of liquid crystal display panels, the mechanical strength of their terminal connections has been improved,
In addition, positioning accuracy has become a very important issue. Hereinafter, a conventional method of connecting terminals of a liquid crystal panel will be described.

FIG. 6 is an explanatory top view of a conventional liquid crystal display panel. In the figure, reference numeral 1 denotes a glass substrate constituting a liquid crystal panel, and a plurality of terminal electrodes 2 are formed on its outer edge, for example, by ITO
(Indium Tin Oxside), Cr, Al or the like. Reference numeral 3 denotes a TCP in which a pattern is formed on a resin film of polyimide or the like with a copper foil and a driving LSI 4 is mounted.
Reference numeral 5 denotes an anisotropic conductive adhesive used for bonding the electrode terminal 2 of the liquid crystal panel to the TCP 3. 6 is T
This is an external printed board for inputting a signal to CP3.

The anisotropic conductive adhesive used here often contains an epoxy-based insulating thermosetting component adhesive mixed with conductive particles.

[0005] The conductive particles include plastic particles coated with Ni / Au having a diameter of 5 to 12 µm, metallic Ni particles, and solder balls (about 10 µm in diameter).

The meaning of anisotropic conductivity means that, for example, when viewed three-dimensionally, it exhibits insulating properties in the XY directions and conductivity in the Z directions. When a large number of terminal electrodes are close to each other due to the small pitch between the terminals, such as the terminal electrodes used in liquid crystal display panels, a bridge occurs between the terminal electrodes if a conventional connection method such as soldering is used. XYZ
In some cases, a short circuit may occur in all three directions.

When the anisotropic conductive adhesive is used, each electrode of the liquid crystal panel is in the Z direction, that is, as in this case,
Since conduction occurs only in the direction in which each electrode of the corresponding TCP is connected, this is very advantageous in the field of liquid crystal panels.

As shown in the top view of FIG. 7, a driving LSI 4 is mounted on an external printed circuit board 6 by, for example, a wire bonding method, a flip chip method, or the like. There is also a method of connecting the film with an anisotropic conductive adhesive 5 via an FPC 7 patterned with a copper foil.

As a connection method, an anisotropic conductive adhesive is adhered on a liquid crystal panel or a TCP and then electrode terminals or alignment marks formed on a TCP 3 or an FPC 7 and on a glass substrate 1 of a liquid crystal display panel. In general, a method of accurately aligning an electrode terminal or an alignment mark, and performing thermocompression bonding from the TCP side with a heating and pressing tool. The heating and pressing tool means a thermocompression bonding tool in the expression of the claims.

The heating and pressurizing tool can apply pressure by using an air cylinder or the like while heating, in such a manner that an object to be pressed is sandwiched from above and below by a pressure surface of the tool and a surface plate or the like.

Since the parallelism and flatness of the pressure surface of the tool, which is the surface to be brought into contact with the object to be crimped, is important for uniform thermocompression bonding, a set screw and a set screw are arranged on the upper surface of the tool. The degree of parallelism and flatness can be adjusted.

[0012]

However, in the conventional method, the TCP and the liquid crystal display panel are bonded only on one side of the TCP. As shown in the sectional view of the connection portion between the TCP and the liquid crystal panel in FIG. 8, when the pitch of the terminal electrodes of the TCP becomes finer, a copper foil is formed on the polyimide film 8 using an epoxy-based adhesive 9 or the like. Since the bonding area between the terminal electrode 10 of the flexible circuit board formed by bonding and the polyimide film 8 is reduced, the bonding strength of the terminal electrode is rapidly reduced, and when a peeling force is applied to the polyimide film, the bonding strength is reduced. Only a structure having a problem in terms of strength, in which peeling easily occurs between the terminal electrode 9 and the terminal electrode 10, was obtained. In addition, the pitch of terminal electrodes is becoming finer as the electronic circuit technology becomes higher definition.
Not only the manufacturing accuracy of the CP, the positioning accuracy of the terminal electrodes of the TCP and the terminal electrodes of the liquid crystal display panel, but also the deviation between the terminals due to variations in the thermal expansion of the TCP during thermocompression bonding cannot be ignored. According to the experiment of the inventor of the present invention, the amount of thermal expansion in the length direction of the 35 mm wide TCP during thermocompression bonding is 60 μm to 100 μm, and the variation in the amount of thermal expansion during thermocompression bonding is as large as 40 μm. The large variation is due to the unevenness of the flatness of the heating and pressing tool. That is, the portion to which the pressure is sufficiently applied has a small spread due to the heat of the TCP, and the portion to which the pressure is insufficiently applied has a large spread. As an effective method to prevent the disadvantage that this variation is large,
For example, JP-A-5-95021 and JP-A-5-95021
In the invention disclosed in US Pat.
There has been proposed a method in which a slit is formed in a terminal electrode portion of a CP and a deviation from a terminal electrode of a liquid crystal display panel due to an amount of thermal expansion generated during thermocompression is absorbed by the slit portion. However, in this method, the anisotropic conductive adhesive flows out through the slit during thermocompression and adheres to the heating / pressing tool, so that the flatness of the heating / pressing tool is impaired and good crimping cannot be performed. Also there is a method of sandwiching the cushioning material's love between heating and pressing tool and TCP. As the cushioning material, a strip of silicone rubber having a thickness of about 0.2 to 0.4 mm is used by attaching a jig to a heating and pressing tool to make the pressure uniform.

[0013] However, the anisotropic conductive adhesive comes into close contact with the cushioning material, and the cushioning material may be broken, thus causing a problem in use.
Also, when using FPC, there is exactly the same problem as when using TCP.

An object of the present invention is to solve the above problems, the terminal contact of the liquid crystal display panel that does not cause high strength and positional deviation
SUMMARY OF THE INVENTION An object of the present invention is to provide a connection structure and a method of connecting terminals thereof .

[0015]

In order to achieve the object of the present invention, a terminal connection structure of a liquid crystal display panel according to the present invention has a different structure used for connection between an electrode terminal of the liquid crystal display panel and an electrode terminal of a flexible circuit board. The electrode terminal of the liquid crystal display panel and the flexible circuit board and a reinforcing material provided on the flexible circuit board are simultaneously bonded by thermocompression bonding using a conductive adhesive to form an integral unit. An anisotropic conductive contact melted during the thermocompression bonding between the electrode terminals of the terminal electrode portion on the circuit board.
An adhesive is applied between the flexible circuit board and the reinforcing material.
At least one slit at the location where it flows out
It is characterized by being formed as described above .

As a reinforcing material used at this time, a cushioning material used between the tool and the TCP during thermocompression bonding may be used.

Further , the terminal connection of the liquid crystal display panel of the present invention.
The method uses anisotropic conductive adhesive on the electrode terminals of the liquid crystal display panel.
Affixing multiple flex on this anisotropic conductive adhesive.
After arranging the circuit board with a predetermined gap,
Provide a reinforcing material on multiple flexible circuit boards and
Crystal display panel and the reinforcing member
Circuit board, and in this state the flexible circuit board
While connecting the electrode terminals of the plate, the anisotropic conductive contact
The adhesive is heated and dissolved, and the anisotropic conductive
The reinforcing material is attached to the liquid crystal display panel by an electrically conductive adhesive.
It is characterized by bonding .

[0018]

By using TCP or FPC having a slit formed on the base film of the terminal electrode portion, the anisotropic conductive adhesive melted at the time of thermocompression bonding flows out between the slits and is placed on the TCP or FPC. When the adhesive penetrates into the gap between the reinforcing member and the reinforcing member, the reinforcing member is also bonded, so that the TCP or the FPC is eventually sandwiched between the liquid crystal display panel and the reinforcing member and adheres from above and below.

Further, when the anisotropic conductive adhesive is cured and bonded by using a heating and pressing tool, a buffering material drawn under the heating and pressing tool is used as a reinforcing material, so that the reinforcing material is used as a buffering material. There is no need to prepare separately.

[0020]

[0021]

An embodiment of the present invention will be described with reference to the drawings.

Embodiment 1 FIG. 1 is an explanatory top view showing a method for connecting a TCP to a liquid crystal display panel according to the present invention. Liquid crystal display panel 1
An anisotropic conductive adhesive is adhered to the terminal electrode portion 2 of FIG.
The anisotropic conductive adhesive is usually in the form of a tape having a width of about 1.5 to 3.0 mm, and can be used provided with a separator as in a double-sided adhesive tape. Reference numeral 11 denotes a TCP in which at least one or more slits 14 are formed between the electrode terminals of the terminal electrode portion (hereinafter simply referred to as TCP in the description of the embodiment). Methods for forming a slit in TCP include (1) mechanical cutting,
(2) Chemical etching (3) Processing methods such as laser cutting. In forming this slit, there is no particular problem before or after the liquid crystal driving LSI 4 is mounted on the film carrier. The TCP is sucked by a TCP suction nozzle, and alignment is performed while viewing each alignment mark with a camera from below the liquid crystal display panel. When the positioning is completed, the suction nozzle is lowered and T
The CP and the liquid crystal display panel are temporarily connected by the tack force of the anisotropic conductive adhesive.

The term "tack force" as used herein means an adhesive force at which the anisotropic conductive adhesive has low tackiness at room temperature.

When the temperature is increased to 60 to 80 ° C., the tack force increases, and the TCP does not come off.

Numeral 12 is a reinforcing material placed on the upper surface of the TCP. The surface of the reinforcing material is required to have a flatness of about ± 5 μm or less. Therefore, the material of the reinforcement is flat.
Further, those having heat resistance of about 300 degrees are preferable, and silicone rubber, glass, ceramics and the like are used. The shape is preferably a strip shape as shown in FIG.
The thickness is preferably about 0.2 to 1 mm so that the heat of the heating and pressing tool is easily transmitted to the anisotropic conductive adhesive. As a method of processing the reinforcing material into a strip shape, mechanical cutting by a cutter using cemented carbide or diamond teeth is the most inexpensive and desirable. As a method of placing the reinforcing material on the TCP,
It is desirable to use a method in which the reinforcing material is suctioned by a suction nozzle and placed in alignment with TCP while the edge of TCP is recognized by a camera.

The pressure surface of the heating and pressing tool has a width of 2 to 3.5 m.
m, length of 300 to 350 mm, and high thermal conductivity and small thermal expansion coefficient as the material, for example, PSL, SKD
(One kind of cemented carbide) SUS 304 stainless steel or the like is suitable. The condition of heating and pressing is about 250-300 temperature.
C., pressure 20 to 40 kgf / cm ² , time 20 to 30 seconds.

After the reinforcing material is placed on the TCP, the cushioning material is placed thereon, and the pressure surface of the heating and pressing tool is further lowered to abut against the buffering material. As shown in the explanatory diagram, the melted anisotropic conductive adhesive 5 flows out between the slits and from both sides of the TCP and the TCP 1
The liquid crystal display panel and the reinforcing material, as well as the TCP and the reinforcing material, are integrally bonded not only between the terminal 1 and the terminal electrode portion of the liquid crystal display panel, but eventually the TCP is bonded from above and below.

In this way, all bonding is completed by one thermocompression bonding, so that a high-strength terminal connection can be made without any displacement.

The expansion of the entire electrode terminal due to the thermal expansion of the TCP generated during thermocompression bonding is the sum of the thermal expansion of each block divided by the slit formed between the electrode terminals of the TCP.

Therefore, the displacement at both ends of each block is divided by the slit, and the amount of displacement is much smaller than the amount of displacement on both sides of the TCP when no slit is formed. Absent.

Embodiment 2 FIG. 3 is an explanatory sectional view showing a second embodiment of the present invention.

Numeral 12 denotes a reinforcing material. As shown in the figure, a buffering material inserted between the heating and pressing tool 13 and the TCP 11 is conventionally used as a reinforcing material instead of the reinforcing material in the first embodiment.

When the thermocompression bonding is performed with a heating and pressing tool using both the buffer material and the reinforcing material, the flatness of the surface in contact with the liquid crystal display element may be deteriorated. However, this problem can be solved.

Reference Example FIG. 4 is an explanatory sectional view showing a reference example of the present invention.

Reference numeral 13 denotes a heating / pressing tool for thermocompression-bonding the liquid crystal display element and the TCP. As shown in the perspective view of FIG. 5, a vacuum suction hole is provided on the crimping surface. The size of the suction hole may be smaller than the tool width, and its shape may be round or square. After the buffer material 12 is vacuum-adsorbed to the heating / pressing tool, thermocompression bonding is performed. After the completion of the thermocompression bonding, the vacuum surface of the heating and pressing tool 13 is released, and then the pressure surface of the tool is raised.

[0036]

Since the present invention is configured as described above, it has the following effects.

Electrode terminals of liquid crystal display panel, TCP, FP
In connection with an electrode terminal of a flexible circuit board such as C using an anisotropic conductive adhesive, since the flexible board is bonded and sandwiched from both sides of the liquid crystal panel and the reinforcing material, the peel strength of the flexible board is And a highly reliable connection can be realized.

As a reinforcing material to be attached on the flexible substrate, a buffer material of a heating / pressing tool used when the flexible substrate and the liquid crystal display panel are thermocompression bonded to an anisotropic conductive adhesive is used. It is not necessary to prepare a new reinforcing material, and the cost of the product can be reduced.

When both the cushioning material and the reinforcing material are used and thermocompression bonding is performed by a heating and pressing tool, the flatness of the surface in contact with the liquid crystal display element may be deteriorated. However, this problem can be solved.

[0040]

[Brief description of the drawings]

FIG. 1 is an explanatory top view showing a first embodiment of the present invention.

FIG. 2 is an explanatory sectional view of a connection portion between the flexible substrate and the liquid crystal panel according to the first embodiment of the present invention.

FIG. 3 is an explanatory sectional view showing a second embodiment of the present invention.

FIG. 4 is an explanatory sectional view showing a reference example of the present invention.

FIG. 5 is an oblique view of a heating and pressing tool for carrying out a reference example of the present invention.

FIG. 6 is an explanatory top view showing an example according to the related art.

FIG. 7 is an explanatory top view showing an example according to the related art.

FIG. 8 is a sectional view of a connection portion between a flexible substrate and a liquid crystal panel in an example according to the related art.

[Explanation of symbols]

 Reference Signs List 1 glass substrate 2 terminal electrode of liquid crystal panel 3 TCP 4 driving LSI 5 anisotropic conductive adhesive 6 external printed circuit board 7 FPC 8 polyimide film 9 adhesive 10 terminal electrode of flexible substrate 11 slit formed between terminal electrodes TCP 12 Reinforcement 13 Heat and pressure tool 14 Slit

Continuation of front page (56) References JP-A-3-175427 (JP, A) JP-A-6-202136 (JP, A) JP-A-50-68356 (JP, A) JP-A-4-263220 (JP) JP-A-4-324949 (JP, A) JP-A-5-188389 (JP, A) JP-A-56-161586 (JP, A) JP-A-8-234222 (JP, A) 8-213721 (JP, A) JP-A-7-175077 (JP, A) JP-A-5-281564 (JP, A) JP-A-63-130733 (JP, U) (58) Fields investigated (Int. Cl. ^7, DB name) G02F 1/1345

Claims (3)

(57) [Claims] 1. An electrode terminal of the liquid crystal display panel, the flexible circuit board, and the flexible circuit board, using an anisotropic conductive adhesive used for connection between the electrode terminal of the liquid crystal display panel and the electrode terminal of the flexible circuit board. forms integrally bonded simultaneously by thermocompression reinforcements installed above, between the electrode terminals of the terminal electrode portions of the flexible circuit board, melted during the thermal bonding
The anisotropic conductive adhesive is in front of the flexible circuit board
There is a slit at the position where it flows out between the reinforcing material
A terminal connection structure for a liquid crystal display panel formed at least at one or more locations . 2. The thermocompression bonding tool according to claim 2, wherein the reinforcing material attached to the flexible circuit board is used for thermocompression bonding the flexible circuit board and the liquid crystal display panel with the anisotropic conductive adhesive. Claim 1 which is a cushioning material.
The terminal connection structure described. 3. An anisotropic conductive adhesive is attached to an electrode terminal of a liquid crystal display panel, and a plurality of flexible circuit boards are arranged on the anisotropic conductive adhesive with a predetermined gap therebetween. A reinforcing material is provided on a flexible circuit board, the flexible circuit board is sandwiched between the liquid crystal display panel and the reinforcing material, and the electrode terminals of the flexible circuit board are connected in this state, and the anisotropic conductive adhesive is applied. A method of connecting terminals of a liquid crystal display panel, wherein the reinforcing material is bonded to the liquid crystal display panel with an anisotropic conductive adhesive flowing out of the gap after heating and melting.