JPH0696620A - Anisotropic conductive material, method for connecting circuit using same, and electric circuit substrate - Google Patents

Abstract

PURPOSE:To provide an anisotropic conductive material where a fine electrode pattern can be connected with high reliability by dispersing a conductive particle covered with an active energy ray curing type resin into an insulative binder. CONSTITUTION:A conductive particle 2 such as a metal particle is covered with an active energy ray curing type resin 1, followed by dispersion in an insulative binder 3, thus forming an anisotropic conductive material. Circuit substrates 4, 6 with electrodes 5, 7, disposed opposite to each other are provided to hold the conductive material. An active energy ray irradiates the material except for the upper portions of the electrodes 5, 7. Accordingly, the resin 1 covering the irradiated portions is cured. The circuit substrates 4, 6 are pressurized or heated under pressure for electric connection and mechanical connection. Consequently, it is possible to connect a fine electrode pattern having 20mum or less with high reliability.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention can be used for electrical connection between fine electrode circuits, for example, connection between a liquid crystal display and a flexible circuit board, and connection between a semiconductor integrated circuit and a circuit board on which the semiconductor integrated circuit is mounted. The present invention relates to an anisotropic conductive material, a circuit connecting method using the same, and an electric circuit board obtained by the circuit connecting method.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and thinning of electronic parts, the patterns of wiring conductor circuits for mounting them have become finer. Therefore, it is difficult to connect these fine circuits with a conventional solder or rubber connector, and an anisotropic conductive material has recently begun to be used.

This anisotropic conductive material is composed of conductive particles dispersed in an insulating resin binder, and the material is sandwiched between two electrode circuits to be connected and pressed or heated and pressed. By compressing the resin binder by means of the above, only the electrodes facing each other between both circuits where the distance is short and the density of the conductive particles is high are electrically connected. However, in this method, if too many conductive particles are dispersed in the resin binder, parts other than the counter electrode, for example, adjacent electrodes may be electrically connected, and if the amount of conductive particles is small. On the contrary, there is a possibility that the counter electrode may lose conduction. Therefore, the connection between the electrodes having the fine circuit pattern has a problem in terms of reliability.

On the other hand, as an anisotropic material having improved reliability in connection of counter electrodes of a fine circuit pattern, it is disclosed in Japanese Patent Laid-Open No.
No. 103874 discloses an anisotropic conductive film in which the surface of conductive particles is covered with an insulating polymer that is broken when a constant pressure is applied, and in Japanese Patent Laid-Open No. 3-46774, the surface of conductive particles is insulated. Anisotropically conductive adhesive coated with a thermoplastic resin is disclosed.

[0005]

However, in the conductive particles coated with the insulating polymer, the temperature and pressure conditions at the time of connection depend on the type and amount of the coated polymer and the binder in which it is dispersed. It must be delicately controlled, and the connection of a fine electrode pattern of 20 μm or less still has a problem in reliability. The present invention is intended to solve the above problems, and an object thereof is to provide an anisotropic conductive material capable of connecting a fine electrode pattern of 20 μm or less with high reliability, a circuit connecting method using the same, and a method for connecting the same. The present invention provides an electric circuit board obtained by a connecting method.

[0006]

DISCLOSURE OF THE INVENTION The present invention is an anisotropic conductive material obtained by dispersing conductive particles coated with an active energy ray-curable resin in an insulating binder; two sheets having opposing electrodes. Of the anisotropic conductive material is disposed in at least one of the electrode circuits of the electrode, and the surface of the material is irradiated with an active energy ray except for the portion on the electrode to coat the conductive particles under the irradiated portion. After the wire-curable resin is cured, the material is sandwiched between both electrode circuits, and pressure or heat and pressure are applied to electrically and mechanically connect the circuits, which is a method of connecting circuits. And an electric circuit board formed by the circuit connecting method.

The anisotropic conductive material according to the present invention will be described in detail below. As the conductive particles used in the anisotropic conductive material of the present invention, metal particles are generally used. Examples of these are Au, Ni, Cr, Al, Mo, Sb and C.
Examples of the metal particles include u, Ag, Pt, and Co. These metal particles may be a simple substance, an alloy, or an oxide as long as they have conductivity, and it is also possible to use two or more kinds of them in combination. Further, as the conductive particles, glass, synthetic resin or the like having non-conductive particles provided with the metal coating layer on the surface can also be used.

The surface of the conductive particles is coated with an active energy ray curable resin. The active energy ray-curable resin to be coated is an active energy ray, that is, it is cured by ultraviolet rays or electron beams, etc., and exhibits insulating properties at least after curing, and is easily peeled off from the conductive particles even before curing and easily becomes a binder. Any solid or semi-solid material that does not mix is acceptable.

Such materials are selected from active energy ray-polymerizable resins such as urethane acrylate, polyester acrylate, polyester urethane acrylate, epoxy acrylate, polyol acrylate, alkyd acrylate, polyether acryl, epoxy methacrylate and polybutadiene. Is
They may be used alone or in combination of two or more.

In order to accelerate the curing of the resin,
It is preferable to add a photoinitiator, for example, diethoxyacetophenone, 2-hydroxy-2methyl-1-phenylpropan-1-one, benzyldimethylketal, 1-hydroxycyclohexylphenylketone, benzophenone, isopropylbenzoinether, isopropyl. Examples thereof include benzoin ether, benzoin methyl ether, and azobisisobutylnitrile.

The anisotropic conductive material of the present invention is one in which conductive particles coated with an active energy ray-curable resin are dispersed in a binder. The form of the anisotropic conductive material is a paste-like adhesive for one electrode. Apply it to the circuit and place another circuit on the opposite side, and electrically or electrically connect the opposing electrodes by pressing or heating / pressing, or by molding it into a film adhesive and sandwiching it between the two circuits by hot pressing. The counter electrodes can be electrically connected, or the counter electrode can be electrically connected by applying pressure or heat and pressure after applying the adhesive solution and drying the solvent.

As the binder, it is preferable to use a resin which is hardened and bonded by hot pressing as the paste-like adhesive, and when it is formed into a film, a resin which is plasticized and bonded by hot pressing is used. When the solution is applied, either a resin that is hardened and bonded by hot pressing or a thermoplastic adhesive resin that is melted by hot pressing can be used.

For example, polyethylene, polypropylene,
Polystyrene, cellulose acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl chloride, polyurethane, polyester, polyamide, unsaturated polyester, epoxy resin, chloroprene rubber, sulfonated rubber, silicone rubber, urethane rubber, SBR, NBR,
Acrylic rubber, natural rubber, ethylene vinyl acetate copolymer, polyisobutyl, polyvinyl ether rubber and the like are used as appropriate, and two or more kinds of them can be used in combination as necessary.

If necessary, rosin, modified rosin,
A tackifier such as a terpene resin, a terpene-phenol resin, an alkylphenol resin and a coumarone indene resin, a cross-linking agent, an antiaging agent, a coupling agent and the like may be appropriately added to the binder.

Next, a method of connecting an electrode circuit using the anisotropic conductive material of the present invention will be described with reference to the drawings. FIG. 1 shows the anisotropic conductive material of the present invention. The anisotropic conductive material is formed by dispersing conductive particles 2 coated with an active energy ray-curable resin 1 in an insulating adhesive 3 which is a binder.

This anisotropic conductive material is placed on the circuit board 4 having the electrodes 5 as shown in FIG. 2, and active energy rays are irradiated from the circuit board 4 side. In this case, the circuit board 4 is transparent to active energy rays, and the electrode 5 is transparent to active energy rays.

When the circuit board 4 does not transmit active energy rays or when both the circuit board 4 and the electrodes 5 transmit active energy rays, an anisotropic conductive material corresponding to the electrode portion is used as shown in FIG. A pattern mask 8 which is not exposed to light is placed on the side of the anisotropic conductive material opposite to the substrate 4, and active energy rays are irradiated from the mask side. In the latter case, a pattern mask may be installed on the substrate side and the active energy ray may be irradiated from this direction. By these methods, the active energy ray-curable resin that coats the conductive particles in the portion exposed to the active energy ray is cured.

After that, the circuit board 6 having the electrodes 7 facing the electrodes 5 is arranged so as to sandwich the anisotropic conductive material, and the binder 3 is compressed by hot pressing. As shown in FIG. 4, the active energy ray-curable resin 1 coated with conductive particles between the electrodes 5 and 7 facing each other is ruptured by pressure and heat during hot pressing, and the electrodes 5 and 7 are exposed to be conductive. Electrical contact is made through the particles 2. Except for the portion sandwiched between the electrodes 5 and 7, the resin 1 is cured by the active energy rays, so that the coating is not broken even by hot pressing and the insulating property is maintained. That is, the resin 1 in which the electrodes 5 and 7 facing each other are electrically conducted and the space between the electrodes adjacent to each other on the left and right is covered with conductive particles.
And the binder 3 keeps the insulation.

By cooling and removing the pressure, the electrical continuity between the counter electrodes in the vertical direction and the electrical insulation between the adjacent electrodes in the horizontal direction are maintained.

[0020]

The anisotropic conductive material of the present invention irradiated with an active energy ray is arranged on one electrode circuit, and the other circuit is placed from above and pressurized or heated. The binder then gains fluidity and plasticity. When sandwiched between electrode circuits and pressurized, the binder first becomes fluid and escapes to a place where the pressure is low, and moves between the conductive particles or between the electrodes adjacent in the lateral direction. In this way, the conductive particles are first sandwiched between the counter electrodes, but by further applying pressure in the vertical direction, they contact the electrodes of the uncured active energy ray-curable resin coating the conductive particles. The broken part is broken and the electrode and the conductive particle come into contact with each other. The conductive particles are sandwiched and fixed between both electrodes and directly contact with both electrodes to form an electrical connection. The conductive particles between adjacent electrodes in the horizontal direction are in a state of being wrapped with a cured insulating resin film and dispersed in the binder, so that a good insulating state is maintained between the electrodes in the horizontal direction. .

In the case of using the conventional conductive particles coated with an insulating polymer, the presence or absence of breakage of the polymer due to the difference in pressure between the counter electrodes and the portion other than the counter electrodes is utilized to determine the distance between the counter electrodes. Although conduction and insulation other than that were formed, in this case, delicate control of pressure is required. On the other hand, in the present invention, the conductive particles existing between the counter electrodes are easily broken because the surface is covered with the uncured resin, and the conductive particles in the other portions are a resin having a cured insulating property. There is no need for delicate pressure control for the connection of the electrode circuit, due to the clear difference of being covered with a coating.

[0022]

【Example】

Example 1 As conductive particles, Ni- and Au-plated polyethylene particles having an average particle size of 7 μm were used, which were coated with an active energy ray-curable urethane acrylate. This was dispersed in a binder prepared by dissolving a styrene-butadiene block copolymer and a terpene-based tackifier in toluene. This was applied to a separate film (siliconized polyester film) with a bar coder and dried to prepare a film-shaped anisotropic conductive material having an average thickness of 40 μm.

The line width is 20 μm and the pitch is 40 μm.
m, electrode having a thickness of 18 μm, placed on a flexible circuit board that transmits ultraviolet rays, 120 ° C.-10 kg / c
It was heated and pressed at m ² for 5 seconds for temporary adhesion. This was irradiated with ultraviolet rays from the flexible circuit board side. After that, the separate film was peeled off, a glass epoxy circuit board having an electrode facing the electrode of the flexible circuit board was placed on this surface, and after positioning with a microscope, 150
A circuit was connected by heating and pressurizing at 20 ° C.-20 kg / cm ² for 20 seconds for main adhesion.

As an evaluation, conduction between opposing electrodes and conduction between adjacent electrodes were examined. As a result, all the electrodes were electrically connected to each other at a resistance value of 1 Ω or less, and were electrically insulated from each other at a resistance value of 10 7 Ω or more.

Comparative Example 1 The same Ni- and Au-plated polyethylene particles as in Example 1 were used as the conductive particles, and a film-like film was formed in the same manner as in Example 1 without coating the active energy ray-curable resin. An anisotropic conductive material was prepared. Example 1 using this
A similar circuit connection was made.

As evaluation, the conduction between the counter electrodes and the conduction between the adjacent electrodes were examined as in Example 1. As a result, all the electrodes were electrically connected to each other with a resistance value of 1 Ω or less, but the adjacent electrodes were electrically connected without insulation.

Example 2 Using the same film-like anisotropic conductive material as in Example 1,
Line width 20μm, pitch 40μm, thickness 18μ
m on the circuit board with transparent electrodes,
Temporary adhesion was performed by heating and pressing at 10 kg / cm ² for 5 seconds.
A mask having the same circuit pattern as the transparent electrode was placed on the anisotropic conductive material, and ultraviolet rays were irradiated from the mask. After that, the separate film was peeled off, a transparent electrode circuit board having an electrode facing the electrode of the board was placed on this surface, and after alignment with a microscope, 150 ° C.-20 kg / cm ²
Then, pressure and heating were performed for 20 seconds, and main bonding was performed to connect the circuits.

As an evaluation, conduction between opposing electrodes and conduction between adjacent electrodes were examined. As a result, all the electrodes were electrically connected to each other at a resistance value of 1 Ω or less, and were electrically insulated from each other at a resistance value of 10 7 Ω or more.

Comparative Example 2 The same film-like anisotropic conductive material as in Comparative Example 1 was used,
The same circuit connection as in Example 2 was made. For evaluation, the conduction between the counter electrodes and the conduction between the adjacent electrodes were examined in the same manner as in Example 1. As a result, all the electrodes were electrically connected to each other with a resistance value of 1 Ω or less, but the adjacent electrodes were electrically connected without insulation.

[0030]

When a circuit is connected using the anisotropic conductive material of the present invention, delicate control of temperature and pressure is unnecessary, and a fine electrode pattern of 20 μm or less can be electrically connected with high reliability. And is extremely useful in the electrical and electronic fields.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an anisotropic conductive material of the present invention.

FIG. 2 is a schematic cross-sectional view showing a step of irradiating an anisotropic conductive material arranged on an electrode circuit with an active energy ray from the material side.

FIG. 3 is a schematic cross-sectional view showing a step of irradiating an anisotropic conductive material arranged on an electrode circuit with an active energy ray using a pattern mask.

FIG. 4 is a schematic sectional view showing an electric circuit board obtained by connecting opposite electrodes by the method of the present invention.

[Explanation of symbols]

 1 Active Energy Ray Curing Resin 2 Conductive Particles 3 Insulating Adhesive 4 Circuit Board 5 Electrode 6 Circuit Board 7 Electrode 8 Pattern Mask 9 Active Energy Ray

Claims (3)

[Claims] 1. An anisotropic conductive material obtained by dispersing conductive particles coated with an active energy ray-curable resin in an insulating binder. 2. The anisotropic conductive material according to claim 1 is arranged in at least one of two electrode circuits having opposing electrodes,
After irradiating the surface of the material with an active energy ray except the portion on the electrode to cure the active energy ray-curable resin covering the conductive particles under the irradiated portion, the material is placed between both electrode circuits. By sandwiching and pressing or heating and pressing,
A method for connecting circuits, characterized in that electrical connection and mechanical coupling between the circuits are performed. 3. An electric circuit board formed by the circuit connecting method according to claim 2.