JPH0525446A - Anisotropically conductive adhesive - Google Patents

Abstract

PURPOSE:To provide the subject adhesive which has a high reliability, maintains a state of point contact necessary for electric continuity between electrode terminals on a circuit board, and withstands external influences such as an environmental change. CONSTITUTION:The objective adhesnve is prepd. by dispersing electrically conductive graphite particles pretreated with O3 and having a particle diameter of 5-100mum in an electrically insulating adhesive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive adhesive, in particular, it is placed between the electrode terminals of two circuit boards to bond these circuit boards and electrically connect the two electrode terminals. The present invention relates to an anisotropic conductive adhesive.

[0002]

2. Description of the Related Art As a means for providing electrical continuity between two circuit boards, it is known to use various anisotropic conductive adhesives in which conductive particles are dispersed in an insulating adhesive. In particular, when using carbon particles as conductive particles, the degree of adhesion with the insulating adhesive is increased, and in order to maintain the point contact state with the electrode terminals of the circuit board, which is the main role of electrical conduction, On the other hand, it is treated with a primer such as various coupling agents.

[0003]

However, it is difficult to perform a uniform surface treatment by a treating method using a primer such as various coupling agents. Particularly, when the treating amount is too large, there is a risk that an insulating film is formed on the particle surface and the conductivity is impaired. is there. Further, the treatment agent is eluted into the adhesive and causes deterioration, and particularly when the adhesive component is a thermosetting system, there is a possibility that the usable time is seriously adversely affected.

[0004]

Means for Solving the Problems Since the reliability of the connection in the anisotropic conductive adhesive is due to the surface state of the conductive particles rather than the material thereof, the inventors have activated the surface of the conductive particles, It was found that the adhesiveness with the insulating adhesive should be increased, and the present invention was reached as a result of various researches on its treatment method and materials, which dispersed conductive particles in the insulating adhesive. In the anisotropic conductive adhesive, the anisotropic conductive adhesive is graphite particles having a particle size of 5 to 100 μm, which has been subjected to O ₃ treatment before the conductive particles are mixed with the insulating adhesive. The main point is agents. By using the conductive particles that have been subjected to such a uniform surface treatment, the adhesiveness with the adhesive is increased without adversely affecting the insulating adhesive component, and the circuit board, which is the main role of electrical conduction, is Thus, it is possible to provide an anisotropic conductive adhesive capable of maintaining a point contact state with an electrode terminal.

As the conductive particles used in the present invention, reliability of connection for a long period of time is required, and therefore it is desirable to use graphite particles which are chemically stable and have high strength against compression. By subjecting the graphite particles to O ₃ treatment, a functional group such as a carboxyl group is imparted to the particle surfaces, and the surfaces are roughened to increase the contact area with the insulating adhesive and improve the wettability. However, even graphite particles having a particle size of less than 5 μm, particularly less than 1 μm, become brittle by O ₃ treatment and cannot obtain sufficient compressive strength, and the particles are crushed or broken during pressure welding, causing poor conduction. Therefore, it is preferably 1 to 100 μm, preferably 5 μm or more, more preferably 10 μm or more and 100 μm or less.

For the O ₃ treatment of such graphite particles, an O ₃ -containing gas, for example, a gas from an O ₃ generator is usually brought into contact with the graphite particles as they are, or the graphite particles dispersed in a solvent are subjected to O ₃ stirring. _Although a method of blowing a ₃ containing gas is used, the latter method requires drying of the particles after the treatment, which deteriorates workability,
The former method is preferred. If the graphite particles are mixed with the adhesive agent and then subjected to the O ₃ treatment, the components of the connecting agent may be oxidized to cause abnormalities such as deterioration and deterioration. Therefore, the treatment is always performed before the mixing.

The electrically insulating adhesive used for dispersing the graphite particles obtained by such a method is an ethylene-vinyl acetate copolymer, a carboxyl-modified ethylene-
Vinyl acetate, ethylene-acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-isobutyl acrylate copolymer, polyamide, polyester, polymethyl methacrylate, polyvinyl ether,
Polyvinyl butyral, polyurethane, styrene-butadiene-styrene (SBS) block copolymer, carboxyl-modified SBS block copolymer, styrene-isoprene-styrene (SIS) copolymer, styrene-ethylene-butylene-styrene (SEBS) copolymer Coalescence, maleic acid modified SEBS block copolymer, polybutadiene rubber, chloroprene rubber (CR), carboxyl modified C
R, styrene-butadiene rubber, isobutylene-isoprene copolymer, acrylonitrile-butadiene rubber (N
BR), carboxyl-modified NBR, epoxy resin, silicone rubber or the like is used as a main agent.

As the tackifier, rosin, rosin derivative, terpene resin, terpene phenol copolymer, petroleum resin, coumarone indene resin, styrene resin, isoprene resin, alkylphenol resin,
Phenolic resin and the like are appropriately added as necessary as a single type or a combination of two or more types.

Phenolic resins, polyols, isocyanates, melamine resins, urea resins, urotropins, amines, acid anhydrides as a reactive auxiliary agent and a crosslinking agent,
Peroxides, metal oxides, organic acid metal salts such as chromium trifluoroacetate, metal alkoxides such as alkoxides of titanium, zirconia and aluminum, organometallic compounds of dibutyltin oxide, 2,2-diethoxyacetophenone, benzyl, etc. The photoinitiators, sensitizers such as amines, phosphorus compounds, and chlorine compounds are appropriately selected and used as necessary.

If the amount of the graphite particles is too large with respect to the insulating adhesive component, the graphite particles stochastically connect in the planar direction to impair anisotropy, and if the amount is too small, particles are formed on the electrode terminals to be connected. Since it does not exist and leads to disconnection and increase in resistance value, it is 0.
It is preferably 1 or more and 30 parts by volume or less, more preferably 1 or more and 15 parts by volume or less.

The anisotropic conductive adhesive of the present invention is generally interposed between two electrode terminal groups on two opposing electronic / electrical circuit boards, pressed from above one of the electronic / electrical circuit boards, and simultaneously heated or exposed to light. , Irradiating an electron beam to activate the adhesive, fixing the two circuit boards with the adhesive, and electrically connecting opposite electrode terminal groups through conductive particles. This circuit board is specifically made of glass such as a display panel, L
It is a flexible printed circuit board based on metal such as SI chip, metal oxide, polyimide, or polyester resin. These surfaces have -OH,
Since this adhesive has polar groups such as —COOH, —C═O, and —COOCH ₃ , it is required that the adhesive has an adhesive corresponding to this, and its solubility parameter is 8.5 or more, particularly Is preferably 9 or more.

In adjusting these solubility parameters,
In the case of adhesives based on acrylic resin, nitrile rubber, crobrene rubber, vinyl acetate resin, etc., the base polymer alone has a high solubility parameter, so it can be used as it is, but low solubility parameters such as polyisobutylene, polybutadiene, polystyrene, etc. In the case of an adhesive containing a resin having as a main component, it is possible to make the polarity suitable by adding a tackifier such as the above-mentioned phenolic resin.

In the anisotropic conductive adhesive of the present invention, when the adhesive component is a solvent-free solid state or a high-viscosity liquid at room temperature, it is dissolved in an appropriate solvent and subjected to a known method such as printing, coating or spraying. If it is applied directly on the electrode terminal to be connected or formed on the separator, cut it to the desired size and transfer it to the connection electrode terminal part for use, or when the adhesive component is liquid Can be used by coating on the connection electrode terminals at the time of connection work. This makes it possible to uniformly roughen and activate the surface of the conductive particles, increase the contact area with the insulating adhesive, wettability,
Adhesion is improved. Furthermore, high adhesion to the insulating adhesive is obtained in all directions, and microscopic movement due to external force is suppressed, and at the same time it is possible to maintain the point contact state, which is the main role of electrical conduction. Become. Further, since the O ₃ -containing gas is brought into direct contact with the particles, the treatment efficiency is good, and since no solvent is used, there is an operational advantage that drying after the treatment is unnecessary.

[0014]

【Example】

(Example) 75 g of graphite particles having an average particle size of 30 μm (graphite particles, Bellpearl C-2000, manufactured by Kanebo)
Was charged into a gas filter equipped with a 10-liter cylindrical filter, and 55 liters of gas having an O ₃ content of 4.5% by volume was added.
O ₃ -treated graphite particles were obtained by continuously blowing at a rate of time and treating for about 4 hours while stirring in an air stream. Next, acrylonitrile-butadiene rubber (NBR) 100
45 parts by weight of an alkylphenol tackifier was added to parts by weight and dissolved in toluene to obtain a 30% by weight adhesive solution. For 100 parts by weight of this adhesive solution, the O ₃
7 parts by weight of the treated graphite particles were added to obtain an anisotropic conductive adhesive of the present invention. Next, a film thickness after drying was 3 on a flexible printed circuit board in which a 0.4 mm pitch electrode terminal group was formed by a silver paste on a 25 μm PET film.
The anisotropic conductive adhesive layer was provided so as to have a thickness of 0 μm to obtain a flexible printed circuit board with an anisotropic conductive adhesive layer.

(Comparative Example) As the conductive particles, the average particle size is 3
A flexible printed circuit board with an anisotropic conductive adhesive layer was obtained in the same manner as in Example except that 0 μm O ₃ untreated Belpearl C-2000 was used.

Flexible printed circuit boards with anisotropic conductive adhesive layers obtained in Examples and Comparative Examples and area resistivity 30
Ω ITO solid glass substrate at 140 ℃, 20kg / c
m ^2, was heat sealed connection conditions of 10 sec, thermal shock test (-30 ° C., 30 minutes 85 ° C., repeated 1000 times alternately 30 min conditions) and the drop test from a height of a normal temperature environment 50cm Then, the resistance value between the electrode terminals of each flexible printed circuit board and the ITO solid glass substrate was measured, and the results are shown in Tables 1 and 2.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

When the anisotropic conductive adhesive of the present invention is used, O
_{3 The} conductive graphite particles whose surface has been uniformly roughened and activated by the treatment are uniformly and firmly adhered to the insulating adhesive from all directions, and are necessary for electrical conduction between the electrode terminals of the circuit board. It is possible to provide a highly reliable electric or electronic component that maintains a contact state and can withstand the influence of external force such as environmental change.

Claims (1)

Claim: What is claimed is: 1. An anisotropic conductive adhesive having conductive particles dispersed in an insulating adhesive, wherein an O ₃ treatment is performed before the conductive particles are mixed with the insulating adhesive. Particle size 1
An anisotropic conductive adhesive characterized by being 100 μm graphite particles.