JPH10140116A - Anisotropically conductive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an anisotropically conductive thermosetting adhesive which can connects minute circuits to each other at a low temp. in a short time by dispersing conductive particles in a resin compsn. comprising a free-radical- polymerizable resin, an org. peroxide, a thermoplastic elastomer, and a maleimide. SOLUTION: In electrically connecting minute circuits to each other by using an anisotropically conductive thermosetting adhesive prepd. by dispersing conductive particles in a resin compsn. comprising a free-radical-polymerizable resin having both a low-temp. quick curability and a good storage stability, an org. peroxide, and a thermoplastic elastomer, neither sufficient adhesive strength nor connection stability can be obtd. because the resin and the elastomer cause the phase separation due to the difference in compatibility at the step of connecting under heating. The phase separation can be avoided by adding a maleimide to the adhesive, and since a maleimide itself cures, an anisotropically conductive thermosetting adhesive excellent in connecting characteristics is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical connection between fine circuits such as a connection between an LCD (liquid crystal display) and a TCP (tape carrier package) and a connection between a TCP and a PCB (printed circuit board). The present invention relates to an anisotropic conductive adhesive used.

[0002]

2. Description of the Related Art In recent years, anisotropic conductive adhesives in which conductive particles are dispersed in an adhesive resin have been used for liquid crystal displays LCD and T.D.
The necessity of various fine circuit connections such as connection between a CP or TCP and a PCB has been dramatically increased, and an anisotropic conductive adhesive has been used as a connection method thereof. In this method, an anisotropic conductive adhesive is sandwiched between members to be connected and heated and pressed, so that electrical insulation is maintained between adjacent terminals in the surface direction, and electrical conduction is provided between upper and lower terminals. . Anisotropic conductive adhesives have often been used for such applications because of the lack of heat resistance of the adherend and the short circuit between adjacent terminals in fine circuits, such as soldering. The reason is that the connection method cannot be applied.

[0003] The anisotropic conductive adhesive is classified into a thermoplastic type and a thermosetting type. Recently, however, an epoxy resin-based thermosetting type having higher reliability than the thermoplastic type has been used. Things are becoming widely used. As the thermoplastic type anisotropic conductive adhesive, styrene-based copolymers such as SBS (styrene-butadiene-styrene), SIS (styrene-isoprene-styrene), and SEBS (styrene-ethylene-butadiene-styrene) are mainly used. However, these thermoplastic types are basically used in the melt-fusion method, and their workability is generally lower in temperature and shorter time than those of thermosetting if the conditions are selected. Although it is considered applicable and possible,
Due to the low moisture resistance and chemical resistance of the resin, the connection reliability was low, so that it could not withstand a long-term environmental test.

On the other hand, as a thermosetting type anisotropic conductive adhesive which is currently mainstream, an epoxy resin type thermosetting type having a good balance between storage stability and curability is widely used. However, in practice, these thermosetting types are used at a temperature of 150 to 200 ° C. due to their curing reactivity in order to achieve both storage stability and resin curability.
It is necessary to heat and cure for about a second.
At a temperature of 0 ° C. or less, it was difficult to cure the resin in a practical connection time. Furthermore, regarding storage stability,
For example, a system in which a latent curing agent such as a BF ₃ amine complex, dicyandiamide, an organic acid hydrazide, or an imidazole compound is blended has been proposed, but those having excellent storage stability require a long time or high temperature for curing. And low temperature
On the other hand, those which can be cured in a short time have a problem that storage stability is inferior, and all of them have advantages and disadvantages.

In addition to the problems described above, in connection workability between fine circuits using a thermosetting type anisotropic conductive adhesive, a member once connected due to a displacement or the like may be damaged or damaged. There has been a growing demand for peeling without damage and joining again (so-called repair). However, while most of them have advantages such as high adhesive strength and high reliability, it is extremely difficult to respond to such seemingly contradictory requirements, and no satisfactory products have been obtained. In particular, recently, the LCD module has been rapidly increasing in size, definition, and narrowing of the frame, and accordingly, the connection pitch and the connection width have also rapidly advanced. So, for example,
In the connection between the LCD and the TCP, problems such as the connection pattern being shifted due to the extension of the TCP at the time of connection and the members inside the LCD being thermally affected by the temperature at the time of connection due to the narrow width of the connection portion. Was. Further, in the connection between the TCP and the PCB, since the PCB has become longer, there has been a problem that the PCB and the LCD are warped due to heating during the connection, and the wiring of the TCP is disconnected.

Therefore, it has been considered to solve these problems by connecting at a lower temperature.
When trying to connect with a conventional thermoplastic type anisotropic conductive adhesive, connection at a relatively low temperature is possible, but there is a problem that the connection reliability is poor because the moisture resistance and heat resistance of the resin are low. Also, when trying to connect at low temperature with an epoxy resin-based anisotropic conductive adhesive, which is the mainstream of thermosetting type, it is necessary to lengthen the connection time to cure the resin,
It was not practically applicable.

As an anisotropic conductive adhesive which enables low-temperature connection, an adhesive resin in which a cationically polymerizable substance and a sulfonium salt are blended and conductive particles are dispersed (Japanese Patent Laid-Open No. 7-90237). Also, there has been proposed an epoxy resin or the like and a dispersion of conductive particles in a 4- (dialkylamino) pyridine derivative (Japanese Patent Application Laid-Open No. 4-189883). It has not been put to practical use due to problems such as corrosion of the steel. Furthermore, as a material that enables low-temperature connection, a thermosetting anisotropic conductive adhesive in which conductive particles are dispersed in an adhesive in which a radical polymerizable resin and an organic oxide, a thermoplastic elastomer are blended, is used. Although it is considered that the radical polymerizable resin and the thermoplastic elastomer are separated from each other due to a difference in compatibility at the time of heat bonding, there is a problem that sufficient bonding strength and connection stability cannot be obtained. . That is, at present, a resin system that satisfies all of the curability, workability, adhesiveness, connection reliability, etc. in a well-balanced manner has not been obtained. There is a strong demand for an anisotropic conductive adhesive having excellent properties, storage stability, and repairability.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems of the prior art, and has been made as a result of various studies. The purpose of the present invention is to provide a connection between an LCD and a TCP or a TCP. Thermosetting anisotropic, which can be connected at a low temperature and in a short time, and has excellent adhesiveness, connection reliability, storage stability, and repairability in the electrical connection between microcircuits such as the connection between PCB and PCB. It is intended to provide a conductive adhesive.

[0009]

Means for Solving the Problems The present inventor has developed an adhesive containing a radical polymerizable resin, an organic peroxide, and a thermoplastic elastomer, which can achieve both low-temperature quick-curing and storage stability. When making a thermosetting connection using a thermosetting anisotropic conductive adhesive in which conductive particles are dispersed, the radical polymerizable resin and the thermoplastic elastomer are phase-separated from each other due to the difference in compatibility during heat bonding. As a result of various investigations on the point that sufficient adhesive strength and connection stability cannot be obtained,
By adding a maleimide that is compatible with both the radical polymerizable resin and the thermoplastic elastomer in the adhesive, phase separation during heating connection is suppressed, and the maleimide itself cures, resulting in excellent connection characteristics. The present inventors have found that a heat-curable anisotropic conductive adhesive having the same can be obtained and have reached the present invention. That is, the present invention is an anisotropic conductive adhesive characterized in that conductive particles are dispersed in a resin composition comprising a radically polymerizable resin, an organic peroxide, a thermoplastic elastomer and a maleimide.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The radically polymerizable resin used in the present invention is not particularly limited, and has at least one carbon-carbon double bond in a molecule and is capable of radical polymerization. For example, vinyl ester resins, unsaturated polyester resins, diallyl phthalate, various acrylates and the like can be mentioned. Above all, a vinyl ester resin having both curability and storage properties, heat resistance, moisture resistance and chemical resistance of the cured product can be suitably used. Here, the vinyl ester resin refers to a resin obtained by a reaction between an epoxy resin and acrylic acid or methacrylic acid, or a reaction between glycidyl methacrylate and a polyhydric phenol. These may be used alone or in combination with those having different structures and molecular weights. Further, in order to ensure the storage stability, a polymerization inhibitor such as quinones, polyhydric phenols and phenols can be added in advance (for example, JP-A-4-146951). In order to further improve curability, fluidity during heating, and workability, acrylates such as trimethylolpropane triacrylate (TMPTA), pentaerythritol diallylate monostearate, tetraethylene glycol diacrylate, pentaerythritol tetraacrylate, and styrene. It can be used after being diluted with various monomers or a common reactive diluent.

The organic peroxide used in the present invention is not particularly limited. For example, 1,1,3,3-
Tetramethylbutyl peroxy-2-ethyl hexanate, t-butyl peroxy-2-ethyl hexanate,
t-hexylperoxy-2-ethylhexanate,
1,1-bis (t-butylperoxy) -3,3,5-
Trimethylcyclohexane, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, bis (4-t-butylcyclohexyl) peroxydicarbonate and the like can be mentioned. These peroxides can be used alone or as a mixture of two or more kinds of organic peroxides for controlling curability. Various polymerization inhibitors can be added in advance to improve the storage stability. Further, in order to facilitate the work of dissolving the resin, it can be diluted with a solvent or the like before use. Naturally, the type and amount of the organic peroxide used in the present invention are determined depending on the balance between the curability and the preservability of the adhesive when each peroxide is compounded.

The thermoplastic elastomer used in the present invention is not particularly limited. Examples thereof include polyester resins, polyurethane resins, polyimide resins, polybutadiene, polypropylene, styrene-butadiene-styrene copolymer, polyacetal resin, butyl rubber, and chloroprene. Rubber, polyamide resin, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinyl acetate resin, nylon, styrene-isoprene copolymer, polymethyl methacrylate resin and the like can be used. Among them, a copolymer containing acrylonitrile and butadiene as main components can be more preferably used because it has excellent properties such as adhesion and connection reliability when used as an anisotropic conductive adhesive. Further, a copolymer obtained by introducing various functional groups such as a carboxyl group and a hydroxyl group into a copolymer containing acrylonitrile and butadiene as main components can also be used.

The maleimide used in the present invention includes:
There is no particular limitation as long as it has a function of making the radical polymerizable resin and the thermoplastic elastomer compatible with each other. Generally, a resin having a chemical structure exemplified by the formulas (1) and (2) is used. Usage conditions of anisotropic conductive adhesive (connection temperature,
Needless to say, the chemical structure can be selected or changed depending on the connection time) and the type of radical polymerizable and thermoplastic elastomer used.

[0014]

Embedded image

[0015]

Embedded image

The conductive particles used in the present invention are not particularly limited as long as they have conductivity, and various kinds of metals such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, and gold can be used. And metal alloys, metal oxides, carbon, graphite, glass and ceramics, and plastic particles coated with a metal on the surface.
Appropriate particles, materials, and amounts of these conductive particles can be selected according to the pitch and pattern of the circuit to be connected, the thickness and material of the circuit terminals, and the like.

Further, in the anisotropic conductive adhesive of the present invention,
If necessary, a suitable amount of a coupling agent may be added. The purpose of adding the coupling agent is to improve the adhesiveness of the adhesive interface of the anisotropic conductive adhesive, improve the adhesive strength, heat resistance and moisture resistance, and improve the connection reliability. As the coupling agent, particularly, a silane coupling agent can be suitably added and used. For example, an epoxy silane type, a mercapto silane type, an acryl silane type (for example, β-
(3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-
Methacryloxypropyltrimethoxysilane, etc.) can be used.

According to the present invention, an anisotropic conductive adhesive obtained by dispersing conductive particles in an adhesive containing a radical polymerizable resin, an organic peroxide, and a thermoplastic elastomer is used. At the time of curing connection, since the radical polymerizable resin and the thermoplastic elastomer are compatibilized by the maleimide contained in the adhesive, they are cured in a uniformly dispersed state. In addition, since the maleimide resin itself is cured with organic peroxide, it can be connected at extremely low temperatures and in a short time, and is an anisotropic conductive adhesive with excellent adhesiveness, connection reliability, storage stability, and repairability. Is obtained.

[0019]

The present invention will be described below with reference to examples and comparative examples. “Examples 1 to 6” and “Comparative Examples 1 to 3” Preparation of Adhesive Resin Compound The materials shown in Table 1 were dissolved in MEK so as to have the mixing ratio of the non-volatile components shown in Table 2 to obtain an adhesive resin compound solution. 2. Preparation of Anisotropic Conductive Adhesive The composition obtained in the above 2 was subjected to a release treatment of 50 μm.
m on polyethylene terephthalate film
The film was dried in an oven at 0 ° C. for 5 minutes to obtain a 15 μm thick film-like anisotropic conductive adhesive. 3. Evaluation method Table 2 shows the evaluation results of the adhesive strength, connection reliability, and storage stability of the anisotropic conductive films obtained in Examples and Comparative Examples.

[0020]

[Table 1]

[0021]

Embedded image

[0022]

Embedded image

[0023]

Embedded image

[0024]

Embedded image

[0025]

Embedded image

[0026]

Embedded image

[0027]

Embedded image

[0028]

Embedded image

[0029]

[Table 2]

The adherend is copper foil / polyimide = 25 / 75μ
TCP having a tin of 0.4 μm (pitch: 0.1 m).
10 mm, number of terminals: 200) and an indium / tin oxide film having a sheet resistance value of 30Ω formed on the entire surface to a thickness of 1.1 m.
m (hereinafter referred to as ITO glass). -Adhesive strength: Adhesion was performed under the conditions of 150 ° C, 30 kg / c, 15 s, and evaluated by a 90 ° peel test.・ Connection reliability Immediately after sample production and at 85 ° C, 85% humidity, 10
The connection resistance after leaving for 0 hour was measured. Those that could not be measured were regarded as poor conduction (OPEN). -Storage property The connection resistance value when the anisotropic conductive film was used after being left at 25 ° C for 1 week was measured.

[0031]

The anisotropic conductive adhesive of the present invention has excellent adhesive strength, connection reliability, and storage stability.

Claims (3)

[Claims] 1. An anisotropic conductive adhesive characterized in that conductive particles are dispersed in a resin composition comprising a radical polymerizable resin, an organic peroxide, a thermoplastic elastomer and a maleimide. 2. The anisotropic conductive adhesive according to claim 1, wherein the radical polymerizable resin is a vinyl ester resin. 3. The anisotropic conductive adhesive according to claim 1, wherein the thermoplastic elastomer is a copolymer containing acrylonitrile and butadiene as main components.