JP2003262882A - Connection structure of electrode, and liquid crystal display device using the connected structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the connection structure of an electrode by which reliable conduction is obtained without deforming the electrode and shortcircuit never occurs between adjacent terminals though making of fine pitches of terminals is advanced. <P>SOLUTION: In the connection structure by which an adhesive is arranged between two insulated substrates having metallic electrodes provided on the surface of each and both of the metallic electrodes are position-adjusted and connected, the adhesive is nonconductive, and the surface of the metallic electrode of one insulated substrate of the two insulating substrates has a metallic projection part harder than the metallic electrode of the other insulating substrate formed by electrodeposition. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrode connection structure and a liquid crystal display device using the connection structure. More specifically, the present invention relates to a connection structure for electrically connecting two substrates provided with electrodes at opposing positions, and a liquid crystal display element using the connection structure.

[0002]

2. Description of the Related Art As an example of a circuit board mounting technique by thermocompression bonding, there is a mounting technique of an IC module of a liquid crystal display element. In the liquid crystal display element, a drive circuit is connected to a liquid crystal panel in which liquid crystal is sandwiched between two glass substrates. Generally, the driving circuit of the TFT liquid crystal panel module is TF
A tape-shaped film carrier (TCP: Tape Carrier P) which is a circuit board on which an LSI for driving the T is mounted.
ackage) and a circuit board (PCB: Printed Circuit Board) for sending power and image signals to the film carrier.

As a method of connecting the circuit board, an anisotropic conductive film (ACF: Anisot) in which conductive particles are dispersed in an adhesive is used.
Those using oropic Conductive Film) are widely known. The connection method using the anisotropic conductive film is such that one of the glass substrate and the circuit board is attached with the anisotropic conductive film, and the other is positioned and superposed on the anisotropic conductive film. By pressing the tool, the conductive particles are sandwiched between the electrodes of the two substrates. As a result, electrical conduction is developed via the conductive particles. Since the conductive particles independently exist in the resin between the adjacent electrodes of the two substrates, insulation can be maintained.

Next, FIG. 3 shows a cross section of a connection structure using an anisotropic conductive film which is a conventional technique. A glass substrate 51 on the surface of which a transparent electrode 52 made of isodin tin oxide (ITO), tin oxide (SnO 2) or the like is formed, and a metal electrode 54 formed on the surface of a circuit substrate 53 facing the glass substrate 51. Between them, an anisotropic conductive film in which conductive particles 56 are dispersed in the adhesive 55 is sandwiched. Since the conductive particles 56 are sandwiched between the electrodes 52 and 54 of the substrates 51 and 53 facing each other, conduction can be obtained. The adhesive 55 used for the anisotropic conductive film includes a thermosetting resin, a thermoplastic resin, or an ultraviolet curable resin. When a thermosetting or thermoplastic resin is used, the tool pressed against the circuit board 53 is heated to connect the boards. The conductive particles 56 in the anisotropic conductive film have a diameter of 3 to 10 μm, and in the case of a liquid crystal display element, the surface of plastic particles is Ni-plated or the Ni-plated surface is Au-plated. ing.

[0005]

However, in the connection structure using the anisotropic thin film, the conductive particles which should exist independently between the adjacent terminals are aggregated or connected due to manufacturing error or the like. , May be electrically short-circuited. This is not a problem when the distance between the terminals is large with respect to the conductive particle diameter, but the occurrence rate of short circuit increases depending on the particle diameter and the distance between the adjacent terminals. For example, when the diameter of the conductive particles is 5 μm and the distance between the terminals is smaller than 15 μm, the occurrence rate of short circuit occurs at a frequency that cannot be ignored. Further, in order to obtain the reliability of the electrical connection, the number of conductive particles sandwiched between the electrodes of the circuit board needs to be 3 to 5 or more, and when the fine pitch of the terminals is advanced and the area of the electrodes is reduced. Therefore, it becomes necessary to increase the amount of the conductive particles blended in the resin. However, when the blending amount of the conductive particles is increased, the aggregation and connection of the conductive particles are increased and the occurrence rate of short circuit between adjacent terminals is increased. As described above, in the connection structure using the anisotropic conductive film, it becomes difficult to achieve both the reliability of conduction and the prevention of short circuit between terminals as the pitch becomes finer.

On the other hand, there is a connection structure in which an electrode having irregularities on the TAB surface and a transparent electrode of a liquid crystal display element are bonded to each other by a curable adhesive. No. 52408). This TA
The convex portion of the B electrode is pressed against the transparent electrode by being pressed. As a result, in such a junction structure, the transparent electrode of the liquid crystal display element and the TA are not used without using the anisotropic conductive film.
It is possible to obtain a TAB-mounted liquid crystal display element in which the connection failure with the B electrode is reduced and the peeling resistance value of both electrodes is reduced. As a method for forming the unevenness, the publication describes a method of shaving the electrode surface with sandpaper or a method of forming a convex portion.

However, the method of scraping the electrode surface easily deforms the electrode. Further, although the method of forming the convex portion is not specified, it is considered to be a method of directly forming the convex portion on the electrode surface. When such a convex portion is formed by machining, the electrodes are easily deformed, and if the fine pitch of the terminals progresses, it becomes difficult to form the convex portion uniformly, so that the reliability of conduction decreases.

In view of the above circumstances, the present invention provides an electrode having high reliability without deforming the electrode even if the pitch of the terminal is made finer and short circuit between adjacent terminals does not occur. An object is to provide a connection structure and a liquid crystal display device using the connection structure.

[0009]

In the electrode connection structure of the present invention, an adhesive is placed between two insulating base plates each having a metal electrode on each surface, and then both metal electrodes are positioned. A connection structure for connecting together, wherein the adhesive is non-conductive, and the surface of the metal electrode of one of the two insulating bases is insulated from the other of the insulating bases. It is characterized in that a metal convex portion harder than the metal electrode of the substrate is formed by electrodeposition.

Further, the liquid crystal display device of the present invention comprises a liquid crystal panel in which a liquid crystal is sandwiched between a TFT glass substrate having a source electrode and a gate electrode and a glass substrate having a color filter, and the TFT glass substrate. What is claimed is: 1. A liquid crystal display device comprising a circuit board connected to a plurality of terminal groups arranged in a line on an end face by a connection structure of electrodes, wherein the connection structure of the electrodes is a metal provided on two insulating bases. It is a connection structure that connects the electrodes with an adhesive,
There is no conductive particle in the adhesive, and the surface of the metal electrode of one of the two insulating substrates is harder than the metal electrode of the other insulating substrate. It is characterized in that the metal convex portion is formed by electrodeposition.

Further, the circuit board of the present invention is characterized in that a hard metal projection is formed on the surface of the metal electrode provided on the insulating substrate by electrodeposition.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the electrode connecting structure of the present invention, the surface of the electrode terminal of one of the two insulating substrates to be connected has a convex portion formed by electrodeposition. The electrode terminal of one of the substrates is made of metal, and a non-conductive adhesive is used instead of the anisotropic conductive film. The adhesive is transferred to one of the two substrates, the other substrate is superposed on it and positioned, and then pressure and heat are applied from above with a tool such as a heat seal crimping machine. By doing so, the convex portion on the metal electrode of one substrate bites into the metal electrode of the other substrate, and electrical conduction can be obtained. In addition, since there are no conductive particles between adjacent metal electrodes, high insulation can be obtained. Copper (Cu) is used as the material of the electrode terminal, and a convex portion made of nickel (Ni) is formed on the surface of the terminal by electrodeposition such as plating. The method of forming the convex portion can be performed by changing the process conditions during plating. For example, when performing electric field plating, a voltage higher than usual is applied to the metal electrode to rapidly grow Ni. Alternatively, by raising the temperature of the plating solution and performing plating, Ni can be grown rapidly and the convex portions can be formed. In the case of electroless plating, lower the pH of the plating solution and remove Ni in the plating solution.
A large convex portion can be formed by adjusting the ion concentration or the reducing agent concentration to accelerate the Ni growth rate. Gold (Au) may be further plated on the surface of the plated portion to reduce the conduction resistance. The height of the convex portion is not particularly limited in the present invention, but is about 0.
3 to 1.5 μm is a standard. As a material of the metal electrode connected to the metal electrode having the convex portion, a metal having a hardness (soft) smaller than that of the plating material forming the convex portion is used.
This facilitates the protrusion of the plated portion formed on the metal electrode to pierce the opposing metal electrode. Conventionally, ITO electrodes have been used in liquid crystal display elements, but in the present invention, aluminum (Al), chromium (Cr), silver (Ag) or the like is used. In the present invention, the main material of the electrode used for the liquid crystal display element is not limited to the above-mentioned materials, and the surface of the metal electrode may be formed of these materials. When Al or Cu is used for the outermost layer of the electrode, a thin oxide film is formed on the surface, but according to the present invention, if the projection of the plated portion is larger than the thickness of the oxide film, the projection breaks through the oxide film, It is possible to dig into the internal metal electrode to make it conductive. As the adhesive used for connecting the two substrates, a thermosetting resin, a thermoplastic resin, an ultraviolet curable resin, or the like can be used. The adhesive may be in the form of tape or paste. It should be noted that if the height of the convex portion is made as high as possible and the thickness of the opposing electrodes is made large, the piercing depth becomes deeper, so that the reliability of the connection becomes higher.

The electrode connection structure of the present invention, the liquid crystal display device using the connection structure, and the circuit board will be described below with reference to the accompanying drawings.

Embodiment 1 FIG. 1 is a sectional view showing a connection structure of electrodes of a liquid crystal display element according to Embodiment 1 of the present invention.

The liquid crystal display element according to the first embodiment of the present invention is a liquid crystal panel in which liquid crystal is sandwiched between a TFT glass substrate having a source electrode and a gate electrode and a glass substrate having a color filter, and The TFT
A circuit board is connected to a plurality of terminal groups arranged in a line on the end surface of the glass substrate by the electrode connection structure of the present invention. As shown in FIG. 1, the connection structure of the electrodes has a TFT glass substrate (hereinafter simply referred to as a glass substrate).
The metal electrode 2 formed on the substrate 1 and the metal electrode 4 formed on the circuit board 3 are plated on the surface of the metal electrode 4, and the protrusions 5 of the plated portion bite into the metal electrode 2 of the glass substrate 1 ( By piercing), the continuity is obtained. A non-conductive adhesive 6 containing no conductive particles is sandwiched between the two substrates 1 and 3. As the adhesive 6, any one of thermosetting, thermoplastic and ultraviolet curable resins can be used. As the material of the metal electrode 4, for example, Cu or Au is used,
The surface is plated with Ni. The convex portion 5 of the plated portion is formed by the variation in the thickness of the Ni plated portion. In order to further reduce the conduction resistance, Au plating may be applied on the surface of the Ni plated portion. The metal electrode 2 on the glass substrate 1 is made of, for example, Al, Au, Ag, or Cu, and the convex portion 5 of the plated portion of the opposing circuit board 3 digs into the metal electrode 2 to electrically connect the two boards. Are electrically connected. An appropriate value is generally selected for the thickness of the metal electrode 2 of the glass substrate 1 within the range of 100 to 1500 nm according to the circuit specifications. The height of the protrusion 5 of the plated portion formed on the surface of the metal electrode 4 of the circuit board 3 is about the same as the thickness of the metal electrode 2 of the glass substrate 1. The circuit board 3 is generally a TCP (Tape Carrier Pac).
kage) or COF (Chip On Film) is used,
Polyimide resin is used as the raw material. As the glass substrate 1, soda glass or non-alkali glass is generally used, but in the case of film liquid crystal or the like, a synthetic resin substrate such as acrylic resin can be used.

Second Embodiment Next, a second embodiment of the present invention will be described. In the second embodiment, as shown in FIG. 2, an epoxy resin substrate 11 containing glass fibers is used instead of the glass substrate. The metal electrode 12 made of Cu is formed on the surface of the epoxy resin substrate 11, and the surface of the metal electrode 12 may be Au-plated if necessary. In the second embodiment, as in the first embodiment, the N formed on the surface of the electrode 4 of the circuit board 3 facing each other.
The projection 5 of the plated portion of i bites into the metal electrode 12 made of Cu to obtain conduction. In the second embodiment, the convex portion of the plated portion is formed on the metal electrode 4 of the circuit board 3, but the present invention is not limited to this, and the two substrates 3 and 11 to be connected are Since both are resin substrates and the plating process on the metal electrodes (terminals) is easy, it is possible to form the protrusions of the plated portions on the metal electrodes of any of the substrates. Further, as in the first embodiment, the insulating adhesive 6 is sandwiched between the two substrates 3 and 11, and no conductive particles are present. In the present invention,
The substrate 11 is not limited to the epoxy resin substrate containing glass fiber, and may be an epoxy resin substrate containing aramid fiber, a polyimide substrate or a ceramic substrate.

[0017]

As described above, according to the present invention,
Even if the pitch of terminals is made finer, highly reliable conduction can be obtained without deforming the electrodes, and a short circuit between adjacent terminals does not occur.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an electrode connection structure of a liquid crystal display element according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a connection structure of electrodes of a liquid crystal display element according to Embodiment 2 of the present invention.

FIG. 3 is a cross-sectional view of a connection structure using an anisotropic conductive film in a conventional liquid crystal display element.

[Explanation of symbols]

1 glass substrate 2, 4, 12 metal electrodes 3 circuit board 5 Convex part of plated part 6 adhesive 11 Epoxy resin substrate

Claims (7)

[Claims] 1. A connection structure in which an adhesive is disposed between two insulating bases each having a metal electrode provided on each surface thereof, and then the two metal electrodes are aligned and connected to each other. The agent is non-conductive, and a metal convex portion that is harder than the metal electrode of the other insulating substrate is electrically conductive on the surface of the metal electrode of one of the two insulating substrates. An electrode connection structure formed by bonding. 2. The electrode connection structure according to claim 1, wherein the metal convex portion bites into the metal electrode of the other insulating substrate. 3. The electrode connection structure according to claim 1, wherein the material of the metal convex portion is nickel. 4. The electrode connection structure according to claim 1, 2 or 3, wherein the material of the metal electrode of the other insulating substrate is any one of aluminum, gold, silver and copper. 5. The electrode connection structure according to claim 3, wherein gold is electrodeposited on the surface of the metallic projection of nickel. 6. A T having a source electrode and a gate electrode formed thereon.
A liquid crystal panel in which liquid crystal is sandwiched between an FT glass substrate and a glass substrate on which a color filter is formed, and the above-mentioned T
A liquid crystal display device comprising a circuit board connected to a plurality of terminal groups arranged in a line on an end face of an FT glass substrate by a connection structure of electrodes, wherein the connection structure of the electrodes is
A liquid crystal display device having the electrode connection structure according to 2, 3, 4 or 5. 7. A circuit board in which a hard metal projection is formed on a surface of a metal electrode provided on an insulating substrate by electrodeposition.