JPH10168413A - Anisotropically conductive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an anisotropically conductive adhesive improved in adhesiveness, connection reliability, storage stability, and repairability by dispersing conductive particles in a resin compsn. contg. a free-radical-polymerizable resin, a free-radical-polymerizable monomer, an org. peroxide, a thermoplastic elastomer, and a maleimide. SOLUTION: A free-radical-polymerizable resin (A) (e.g. a vinyl ester resin) is compounded with a free-radical-polymerizable monomer (B) (e.g. 2-hydroxy-1,3- dimethanefloxypropane), an org, peroxide (C) (e.g. 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanate), a thermoplastic elastomer (D)(e.g. a polyester resin), and a maleimide (E) represented by formula I (R is a monovalent org. group) or formula II (R is a divalent org. group) at a wt. ratios of C/(A+B) and B/A of (0.1/100)-(15/100) and (1/100)-(90/100), respectively, to give a resin compsn. Conductive particles (e.g. particles of Fe, Ne, Cu, Al, or Sn) are dispersed in the compsn.

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. This anisotropic conductive adhesive is classified into a thermoplastic type and a thermosetting type.Recently, epoxy resin type thermosetting type with higher reliability than thermoplastic type is widely used. It is being used.

[0003] For the thermoplastic type anisotropic conductive adhesive, SBS (styrene-butadiene-styrene), SI
Styrene-based copolymers such as S (styrene-isoprene-styrene) and SEBS (styrene-ethylene-butadiene-styrene) have been mainly used, but these thermoplastic types are basically used in a melt-fusion method. The workability is generally considered to be good because it can be applied at a relatively low temperature and in a short time compared to the thermosetting one if the conditions are selected, but the moisture resistance and chemical resistance of the resin Therefore, the connection reliability was low due to low reliability and the like, 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. Examples of anisotropic conductive adhesives that enable low-temperature connection include those in which conductive particles are dispersed in an adhesive resin containing a cationically polymerizable substance and a sulfonium salt (JP-A-7-90237), and epoxy. Resin or the like and conductive particles dispersed in a 4- (dialkylamino) pyridine derivative (JP-A-4-1898)
No. 83) has been proposed, but has not been put into practical use due to problems such as the preservability of the adhesive resin and corrosion of the connected circuit terminals.

[0007] Further, as an agent which enables low-temperature connection, conductive particles are added to an adhesive containing a radical polymerizable resin excellent in curability at a low temperature and in a short time, an organic oxide, and a thermoplastic elastomer. It is considered to use a dispersed thermosetting anisotropic conductive adhesive, but the radical polymerizable resin and the thermoplastic elastomer are separated from each other due to the difference in compatibility at the time of heat bonding, resulting in sufficient adhesion. There was a problem that strength and connection stability could not be obtained. As a method for solving the problem of separation during heat bonding, it has been proposed to mix maleimide, which is compatible with both the radically polymerizable resin and the thermoplastic elastomer. However, in addition to the decrease in curability due to the addition of maleimide,
Since the melting points of the radical polymerizable resin and maleimide are not sufficiently low with respect to the temperature of heat bonding, the resin fluidity at the time of bonding becomes insufficient, causing poor conduction and increase in connection resistance, and the cured product becomes hard and brittle. There is a problem such as a decrease in adhesive strength, and it has not been put to practical use. 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 inventors have developed an adhesive comprising a radical polymerizable resin capable of achieving both low-temperature quick-curing and storage stability, and an organic peroxide, a thermoplastic elastomer, and a maleimide. When a thermosetting anisotropic conductive adhesive in which conductive particles are dispersed is used for thermosetting connection, the cured product of the radical polymerizable resin and maleimide is converted to electrical conductivity, curability, adhesion, workability, etc. As a result of adding various investigations on the point that sufficient characteristics cannot be obtained, a heat-curable anisotropic conductive adhesive having excellent connection characteristics can be obtained by adding a radical polymerizable monomer to the adhesive. This has led to the present invention. That is, the present invention relates to a radically polymerizable resin (A), a radically polymerizable monomer (B), an organic peroxide (C), a thermoplastic elastomer (D), a maleimide (E), and a resin dispersed in these resin compositions. (C) / {(A) + (B) + (E)} = 0.1
/ 100 to 15/100 (2) (B) / (A) = 1/100 to 90 /
100 is an anisotropic conductive adhesive.

[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, it is possible to add a polymerization inhibitor such as quinones, polyhydric phenols and phenols in advance (for example, JP-A-4-146951).

[0011] The radical polymerizable monomer used in the present invention is not particularly limited, and those having both curability and fluidity can be suitably used. For example, 2-hydroxy-1,3-dimethanefuroxypropane, dimethylacrylamide, acryloylmorpholine, ethylene glycol-modified bisphenol A diacrylate, ethylene glycol-modified bisphenol F diacrylate, ethylene glycol-modified paracumylphenol acrylate, N-vinyl -2-pyrrolidone, polypropylene glycol diacrylate, ethylene glycol isocyanurate-modified diacrylate, isoamyl acrylate, lauryl acrylate, stearyl acrylate, butoxyethyl acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isobonyl acrylate, 2-hydroxyethyl acrylate , 2-hydroxypropyl acrylate, 2
-Hydroxy-3-phenoxypropyl acrylate,
2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl-2-hydroxyethyl phthalic acid, 2-acryloyloxyethyl acid phosphate, neopentyl glycol diacrylate 1,6-hexanediol di Acrylate, isooctyl acrylate, benzyl acrylate, nonylphenoxyethyl acrylate, ethylene glycol-modified nonylphenol acrylate,
Propylene glycol-modified nonylphenol acrylate, 2-hydroxybutyl acrylate, perfluorooctylethyl acrylate, dimethylol tricyclodecane diacrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate,
Isodecyl methacrylate, n-lauryl methacrylate, tridecyl methacrylate, n-stearyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, isobonyl methacrylate, benzyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate , 2-hydroxypropyl acrylate, 2-hydroxybutyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, methacrylic acid, succinic acid, phthalic acid, glycidyl methacrylate, mono (2
-Methacryloyloxyethyl) acid phosphate, mono (2-acryloyloxyethyl) acid phosphate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, t-butyl methacrylate , Isostearyl methacrylate, behenyl methacrylate, n
-Butoxyethyl methacrylate, 2-phenoxyethyl methacrylate, 2-methacryloyloxyethyl-
2-hydroxypropyl phthalate, glycerol monomethacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, 1,3-butanediol dimethacrylate, neopentyl glycol dimethacrylate, 1,10- Decanediol dimethacrylate,
Dibromoneopentyl glycol dimethacrylate, dibromoneopentyl glycol dimethacrylate, trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,4,4
4-tetrafluoropropylbutyl methacrylate, perfluorooctylethyl methacrylate, β-methacryloyloxyethyl hydrogen phthalate, β-methacryloyloxyethyl hydrogen succinate,
3-chloro-2-hydroxypropyl methacrylate, stearyl methacrylate, β-acryloyloxyethyl hydrogen succinate, lauryl acrylate, and the like may be used, and one or more of them may be used. Furthermore, by using a radical polymerizable monomer having characteristics such as adhesion to an adherend and toughness of a cured product, it is possible to more easily design an anisotropic conductive adhesive.

The mixing ratio of the radically polymerizable monomer (B) to the amount of the radically polymerizable resin (A) is less than (B) / (A) = 1/100 by weight. Fluidity and curability are insufficient, sufficient connection reliability cannot be obtained, and the ratio is (B) / (A) = 90 /
If it exceeds 100, the workability will deteriorate and the adhesive force will decrease due to excessive fluidity during heat bonding.

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 of the organic peroxide used in the present invention is determined depending on the balance between the curability and the storage stability of the adhesive when each peroxide is blended. The mixing ratio of the organic peroxide (C) to the radical polymerizable resin (A), the radical polymerizable monomer (B) and the maleimide (E) is as follows.
(C) / {(A) + (B) + (E)} =
If it is less than 0.1, the necessary thermosetting property cannot be obtained, and the same ratio is (C) / {(A) + (B) + (E)} = 15.
If the ratio exceeds the above, storage stability decreases.

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.

[0016]

Embedded image (Wherein, R: a monovalent organic group)

[0017]

Embedded image (Wherein, R is a divalent organic group)

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, an appropriate amount of a coupling agent may be added to the anisotropic conductive adhesive of the present invention, if necessary. 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, a silane-based coupling agent can be particularly suitably added and used. Examples thereof include epoxysilane-based, mercaptosilane-based, and acrylsilane-based (for example, β- (3,4-epoxycyclohexyl) ethyltriethyl). Methoxysilane, 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, a radical polymerizable monomer, an organic peroxide, and a thermoplastic elastomer. When using an agent, the radical polymerizable monomer contained in the adhesive improves the fluidity during heating and bonding, the curability, the adhesion of the cured product, the toughness, etc., and makes it possible to connect at an extremely low temperature in a short time. Although possible, an anisotropic conductive adhesive excellent in adhesiveness, connection reliability, storage stability, and repairability can be obtained.

[0020]

The present invention will be described below with reference to examples and comparative examples. “Examples” and “Comparative Examples” 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. The adherend is copper foil / polyimide = 25/75 μm
With a 0.4 μm tin plating (pitch: 0.1
0 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 mm.
(Hereinafter, ITO glass) was used. -Adhesive strength: Pressure was applied under the conditions of 150 ° C, 30 kg / cm ² , and 15 s, and evaluation was performed 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.

[0021]

[Table 1]

[0022]

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[0023]

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[0024]

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[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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[0030]

[Table 2]

[0031]

The anisotropic conductive adhesive of the present invention can be used for electrical connection between microcircuits such as connection between LCD and TCP and between TCP and PCB, especially at low temperature and short time. In addition, adhesion, connection reliability, storage stability,
Excellent repairability.

Claims (3)

[Claims] 1. A radical polymerizable resin (A), a radical polymerizable monomer (B), an organic peroxide (C), a thermoplastic elastomer (D), a maleimide (E), and dispersed in these resin compositions. (C) / {(A) + (B) + (E)} = (C) / {(A) + (B) + (E)}
(0.1 to 15) / 100 (2) (B) / (A) = (1 to 90) / 100. 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.