JPS6279281A - Anisotropic electrically conductive adhesive - Google Patents

Abstract

PURPOSE:The titled anisotropic electrically conductive adhesive, containing electrically conductive metal particles and carbon particles in an insulating adhesive and capable of ensuring sufficient electrical conduction of carbon electrodes to indium-tin oxide electrodes and surely connecting the electrodes. CONSTITUTION:An anisotropic electrically conductive adhesive containing many electrically conductive metal particles 12, e.g. nickel particles, and carbon particles 13 in, e.g. a hot-melt type insulating adhesive 11. The connection of a printed wiring base board 1 to electrodes 2 and 4 of a liquid crystal display panel 3 is completed by using the resultant anisotropic electrically conductive adhesive 5. The electrically conductive metal particles 12 and carbon particles 13 having 20-40mum diameter in almost equal numbers are preferably incorporated to uniformly distribute at a density not to mutually contact the particles.

Description

[Detailed description of the invention] [Technical field of invention] This invention relates to an anisotropically conductive adhesive.

(Technical background of the invention and its problems) As is well known, an anisotropic conductive adhesive is an insulating adhesive mixed with a large number of conductive particles. For example, it is used to connect electrodes of two members, such as connecting an electrode on a wiring board and a terminal electrode of a liquid crystal display panel, or connecting an electrode on a wiring board and an electrode on a semiconductor chip. As this anisotropic conductive adhesive, there are conventionally known adhesives that use conductive metal particles such as nickel as conductive particles and those that use carbon particles.

Figure 2 shows the state in which the electrodes on the wiring board and the terminal electrodes of the liquid crystal display panel are connected using an anisotropic conductive adhesive. The formed flexible wiring board 3 is a liquid crystal display panel, and display panel connection electrodes 2, 2 are formed at the display panel connection part on one side of the wiring board so as to face each terminal electrode 4, 4 of the liquid crystal display panel 3, respectively. has been done. Further, 5 is an anisotropically conductive adhesive. This anisotropic conductive adhesive 5 has a large number of conductive particles 7.7 in a hot melt type (heat reactivation type) insulating adhesive 6, so that the particles do not come into continuous contact with each other. The electrodes 2.2 on the wiring board 1 and the terminal electrodes 4, 4 on the liquid crystal display panel 3 have conductive particles 7°7 interposed between them. . . , and are bonded with an insulating adhesive 6. The conductive particles 7.7 in the anisotropic conductive adhesive 5 are as follows:
Not all particles are distributed independently, and there are quite a high proportion of parts where multiple (2 to 3) particles are in contact with each other as shown in the figure. , Even if multiple particles are in contact with each other in this way, this particle and other particles are distributed in such a way that they do not come into contact with each other. Don't short-circuit your comrades.

The connection between the electrodes 2.2 on the surface of the wiring board 1 and the terminal electrodes 4.4 of the liquid crystal display panel 3 by means of the anisotropic conductive adhesive 5 is performed on one side of the wiring board 1 and the liquid crystal display panel 3, for example, on the wiring board 1. An anisotropic conductive adhesive 5 is applied onto the electrode forming surface of the electrode 4. This is done by stacking the wiring board 1 and the electrodes 2 and 2 facing each other and applying heat and pressure. When heated and pressurized with the adhesive 5 interposed, both electrodes 2.4 are electrically connected via the conductive particles 7. Glued.

By the way, as mentioned above, the electrodes 2.2 on the wiring board 1 and the terminal electrodes 4, 4 on the liquid crystal display panel 3 are bonded with an anisotropic conductive adhesive 5.
When connecting with the terminal electrode 4 of the liquid crystal display panel 3
．． 4 is a transparent electrode (hereinafter referred to as ITO electrode) generally made of ITO < indium tin oxide, which is the same as the display electrode.
In addition, since the electrodes 2, 2 on one side of the wiring board are made entirely of carbon, or are carbon electrodes with a carbon layer formed on a metal electrode to prevent oxidation, Electrode 2 between plate 1 and liquid crystal display panel 3
．． 4, in order to ensure sufficient conductivity and connect the conductive particles 7 in the anisotropic conductive adhesive 5 to the carbon electrode 2 on the wiring board 1, as well as the ITO on the liquid crystal display panel 3.
It is also necessary to make conductive contact with the 11 pole 4 with small contact resistance.

However, in the past, anisotropic conductive adhesives using conductive metal particles or carbon particles were used to connect the wiring board, the liquid crystal display panel, and the electrodes on the wiring board surface. Since the anisotropic conductive adhesive was used, the contact resistance between either the carbon electrode 2 or the ITO electrode 4 and the conductive particles 7 was small, but the contact resistance between the other electrode and the conductive particles 7 was small. Since the contact resistance between the wiring board 1 and the liquid crystal display panel 3 is large, the contact resistance between the wiring board 1 and the liquid crystal display panel 3 is
It was not possible to make a reliable continuity connection.

That is, the carbon electrode 2°2 on the wiring board 1 and the ITO electrode 4 on the liquid crystal display panel 3 are bonded using a conventional anisotropic conductive adhesive mixed with conductive metal particles such as nickel as the conductive particles 7, 7... .4, the metal particles break through the oxide film on the surface of the ITO electrode 4 to ensure conductive contact, but the metal particles do not have sufficient conductivity to the carbon electrode 2 at the initial stage of connection. However, as time passes, the contact resistance gradually increases due to the influence of humidity as the anisotropic conductive adhesive containing conductive metal particles is mixed with the carbon electrode 2 and the ITO electrode 4.
It was not possible to connect the two with sufficient continuity. In addition, when the carbon electrode 2 and the ITOI electrode 4 are connected using a conventional anisotropic conductive adhesive in which conductive particles 7.7... are mixed with carbon particles, the conduction between the carbon particles and the carbon electrode 2 is is good (this is thought to be because the carbon particles fuse with the carbon electrode), but since the carbon particles cannot break through the oxide film of the ITO electrode 4, the surface The contact resistance between the carbon particles and the ITO electrode 4 is large because the carbon particles only come into contact with the oxide film of 4 could not be connected with sufficient continuity.

(Object of the invention) This invention has been made in view of the above-mentioned circumstances, and its purpose is to improve carbon electrodes and I
It is an object of the present invention to provide an anisotropically conductive adhesive that can secure sufficient conduction and reliably connect to a TO electrode.

[Summary of the invention]

That is, the anisotropic conductive adhesive of the present invention is an insulating adhesive mixed with conductive metal particles and carbon particles, and the anisotropic conductive adhesive connects a carbon electrode and an ITO electrode. When connected, this ITO will break through the oxide film of the ITO electrode between the carbon electrode and the TO electrode.
Metal particles that are in reliable conductive contact with the electrode and carbon particles that are in reliable conductive contact with the carbon electrode are interposed, and some of these particles have metal particles and carbon particles that are in contact with each other. Since the carbon electrode and the ITO electrode are present at a high ratio, the carbon electrode and the ITO electrode are connected through the metal particles and carbon particles that are in contact with each other at least in part, so that sufficient conduction can be achieved between the carbon electrode and the ITO electrode. can be secured and connected reliably.

[Embodiments of the invention]

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

FIG. 1 shows a state in which the display panel connection electrode 2.2 on one side of the wiring board and the terminal electrode 4.4 of the liquid crystal display panel 3 are connected by the anisotropic conductive adhesive 10 of the present invention.

The wiring board 1 has a wiring board II (not shown) formed on a film board made of, for example, a polyester film, and the display panel connection electrodes 2, 2 are carbon electrodes. The terminal electrodes 4, 4 are ITO electrodes.

The anisotropic conductive adhesive 10 includes a large number of conductive metal particles 12, 12...
and carbon particles 13.13...
The hot melt type insulating adhesive 11 is made of synthetic rubber mixed with either a thermoplastic polymer material or a thermosetting polymer material, or a synthetic rubber mixed with a thermoplastic polymer material and a thermosetting polymer material. It is said to have been mixed with a polymeric material.

Further, the metal particles 12 are made of a hard metal such as nickel, and the metal particles 12.12... and the carbon particles 13.13... each have a diameter of approximately 20 mm.
It is said to be ~40 μm thick. The metal particles 12.12... and the carbon particles 13.13... are placed in approximately the same number in the insulating adhesive 11 at a density such that the particles do not come into continuous contact with each other. The mixture is evenly distributed. That is, this metal particle 12
．． 12... and carbon particles 13.13... are mixed so that they are distributed in approximately the same number per unit area, and are generally arranged alternately, and among these particles, metal particles 12 and carbon particles A high proportion of particles 13 are in contact with each other.

The connection of the electrodes 2.4 between the wiring board 1 and the liquid crystal display panel 3 using the anisotropic conductive adhesive 5 is similar to the connection using the conventional anisotropic conductive adhesive.
On the other hand, for example, an anisotropically conductive adhesive 10 is applied on the electrode forming surface of the wiring board 1, or an anisotropically conductive adhesive 1o formed in advance into a sheet is overlaid, and a liquid crystal display panel is placed on top of the anisotropically conductive adhesive 10. 3 and its electrode 4, 4 is the electrode 2 of the wiring board 1
This is done by heating and pressurizing the parts so that they are facing each other.

Therefore, as mentioned above, conductive metal particles 12,12... and carbon particles 13,13...
・The carbon electrodes 2, 2 on one side of the wiring board and the ITO on the liquid crystal display panel 3 are bonded by the anisotropic conductive adhesive 10 mixed with
Electric? 4! When 4.4 is connected, metal particles 12 are formed between the carbon electrode TFT2 and the ITO electrode 4 to break through the oxide film of the ITO electrode 4 and make reliable conductive contact with the ITO electrode 4.
and carbon particles 13 that are in reliable conductive contact with the carbon electrode 2, and some of these particles have the metal particles 12 and carbon particles 13 in contact with each other as described above. Since the carbon electrode 2 and the ITO I electrode 4 are present at a high ratio, at least a portion thereof is connected through the metal particles 12 and the carbon particles 13 that are in contact with each other. and,
In this case, the metal particles 12 and carbon particles 13 that are in contact with each other are always kept in close contact with each other by the insulating adhesive 11 around them. maintains good conductivity without bouncing due to the influence of humidity, and since the metal particles 12 are in reliable conductive contact with the ITO electrode 4 and the carbon particles 13 are in reliable conductive contact with the carbon electrode 2, the carbon electrode 2 Even if the conductivity between the metal particles 12 and the ITO electrode 4 and the carbon particles 13 is poor, the carbon electrode 2 and the ITO electrode 4 have sufficient conduction through the metal particles 12 and carbon particles 13 that are in contact with each other. Connected securely.

In addition, in the above embodiment, the carbon electrode 2 on one side of the wiring board
．． 2 is illustrated as having an electrode entirely made of carbon, but this carbon electrode 2.2 may also be one in which a carbon layer is formed on a metal electrode. Further, in the above embodiment, the connection between the carbon electrodes 2.2 on the wiring board 1 and the ITO electrodes 4, 4 on the liquid crystal display panel 3 has been described, but the anisotropic conductive adhesive of the present invention can be used, for example, in flexible connectors. Carbon electrodes and ITO for liquid crystal display panels
It can also be widely used for connection with electrodes, and connection between carbon electrodes on the surface of wiring boards and ITO electrodes (transparent electrodes on the front side) of solar cells.

〔Effect of the invention〕

The anisotropic conductive adhesive of the present invention is an insulating adhesive mixed with conductive metal particles and carbon particles.
By connecting the O electrode, sufficient conduction can be ensured between the carbon electrode and the ITO electrode, and the connection can be ensured.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a state in which a carbon electrode on a wiring board and an ITO electrode of a liquid crystal display panel are connected using the anisotropically conductive adhesive of the present invention, and Figure 2 is a cross-sectional view of a state in which a carbon electrode on a wiring board and an ITO electrode of a liquid crystal display panel are connected using the anisotropically conductive adhesive of the present invention. FIG. 2 is a cross-sectional view of a state in which a carbon electrode on a substrate surface and an ITO electrode of a liquid crystal display panel are connected. 1... Wiring board, 2... Carbon electrode, 3... Liquid crystal display panel, 4... ITOI! Pole, 10... Anisotropic conductive adhesive, 11... Insulating adhesive, 12... Conductive metal particles, 13... Carbon particles.

Claims (1)

[Claims] An anisotropic conductive adhesive characterized in that conductive metal particles and carbon particles are mixed into an insulating adhesive.