JPH11236540A - Anisotropic conductive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-curable anisotropic conductive adhesive which enables electrical connection between microcircuits, such as between LCD(a liq. crystal display) and TCP(a tape carrier package) or between TCP and PCB (a printed circuit board), to be done in a short time even at a low temp. and is excellent in adhesive properties, connection reliability, storage stability, and repairability. SOLUTION: In an anisotropic conductive adhesive prepd. by dispersing conductive particles in a resin compsn. contg. a free-radically curable resin, an org. peroxide, a thermoplastic elastomer, and a maleimide, the free-radically curable resin is one comprising a (meth)acryloylated novolak resin and 2- hydroxy-3-phenoxypropyl acrylate.

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, LCD and TCP or TCP
The necessity of connecting various microcircuits, such as connection between a PC and a PCB, has been dramatically increased, and an anisotropic conductive adhesive in which conductive particles are dispersed in an adhesive resin has been used as a connection method. . 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. .

[0003] 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 a fine circuit due to electrical short-circuiting. This is because conventional connection methods such as the above cannot be applied. In particular, in recent years, 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.

For this reason, for example, in the connection between the LCD and the TCP, the connection pattern shifts due to the elongation of the TCP due to the heating at the time of connection, and the members inside the LCD at the temperature at the time of connection because the connection portion is narrow. Problems such as being affected by heat have arisen. 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. In order to solve these problems, there is a demand for an anisotropic conductive adhesive that can be connected at a lower temperature and in a shorter time while maintaining sufficient connection reliability.

[0005] Anisotropic conductive adhesives are classified into a thermoplastic type and a thermosetting type. Recently, epoxy resin type thermosetting types having higher reliability than the thermoplastic type have been used. Is widely used. However, these epoxy resin-based thermosetting anisotropic conductive adhesives are heated and cured at a temperature of 150 to 200 ° C. for about 30 seconds in order to achieve both storage stability and resin curability due to their curing reactivity. For example, at a temperature of 150 ° C. or less, it has been difficult to cure the resin in a practical connection time.

Further, regarding the storage stability, for example, B
F ₃ amine complexes, dicyandiamide, organic acid hydrazide, and the like that use the system compounded with latent curing agents such as imidazole compounds have been proposed, are excellent in storage stability requires prolonged or high temperature cure On the other hand, those which can be cured at a low temperature and in a short time have a problem that storage stability is inferior, and all of them have advantages and disadvantages.

[0007] In addition to the above problems, in connection workability between fine circuits using a thermosetting anisotropic conductive adhesive, a member to be connected is damaged due to a displacement or the like of a member once connected. Also, there has been a growing demand for peeling without damage and rejoining (so-called repair). However, most thermosetting anisotropic conductive adhesives have the advantages of high adhesive strength and high reliability, but it is extremely difficult to respond to the seemingly contradictory requirements of ease of repair. Not obtained.

As an anisotropic conductive adhesive which enables low-temperature connection, an adhesive obtained by dispersing conductive particles in an adhesive resin containing a cationically polymerizable substance and a sulfonium salt (JP-A-7-90237) ) Or epoxy resin etc.
A dispersion in which conductive particles are dispersed in a (dialkylamino) pyridine derivative (Japanese Patent Application Laid-Open No. 4-189883) has also been proposed. However, practical use is problematic due to problems such as the preservability of the adhesive resin and the corrosion of connected circuit terminals. Has not been reached.

As an anisotropic conductive adhesive which solves these problems and achieves both low-temperature quick-curing and storage stability, and also achieves connection reliability and repairability, radical polymerizable resins and organic A thermosetting anisotropic conductive adhesive in which conductive particles are dispersed in an adhesive component composed of a peroxide, a thermoplastic elastomer, and a maleimide resin has been proposed. In the anisotropic conductive adhesive, the radical polymerizable resin is a main component that determines many of the adhesive properties such as connection reliability, adhesive strength, and workability. And a radical polymerizable monomer added to the polymer. However, the combination of a thermosetting resin and a radically polymerizable monomer such that the resin-based anisotropic conductive adhesive exhibits good characteristics has not been optimized at present.

That is, at present, curability, workability, adhesiveness,
A resin system that satisfies all of the connection reliability etc. in a well-balanced manner has not been obtained. Therefore, it is possible to connect at a lower temperature and in a shorter time, and it is excellent in adhesiveness, connection reliability, storage stability, repairability, etc. The demand for conductive adhesives has increased.

[0011]

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 in a short time especially at low temperature, and has excellent adhesiveness, connection reliability, storage stability, and repairability in electrical connection between microcircuits such as connection between PCB and PCB It is intended to provide a conductive adhesive.

[0012]

SUMMARY OF THE INVENTION The present inventor has developed an adhesive containing a radical polymerizable resin, an organic peroxide, a thermoplastic elastomer, and a maleimide, which can achieve both low-temperature quick-curing and storage stability. As for the thermosetting anisotropic conductive adhesive with conductive particles dispersed in it, the relationship between various properties of the anisotropic conductive adhesive and the composition of the radical polymerizable resin was repeatedly examined. By using (meth) acryloylated novolak resin having a phenolic hydroxyl group as a resin and 2-hydroxy-3-phenoxypropyl acrylate in combination, high adhesion and connection to various adherends under various environments. The present inventors have found that a thermosetting anisotropic conductive adhesive having reliability can be obtained, and have reached the present invention.

That is, the present invention relates to a resin composition containing a (meth) acryloylated novolak resin having a phenolic hydroxyl group, 2-hydroxy-3-phenoxypropyl acrylate, an organic peroxide, a thermoplastic elastomer and a maleimide. This is an anisotropic conductive adhesive in which particles are dispersed.

As the radical polymerizable resin used in the present invention, a (meth) acryloylated novolak resin having a phenolic hydroxyl group having a structure represented by the formula (1) is used as a curable resin, and 2- (radical polymerizable monomer) is used as a radical polymerizable monomer.
Hydroxy-3-phenoxypropyl acrylate is used in combination.

[0015]

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Further, if necessary, acrylates such as vinyl ester resin, unsaturated polyester resin, diallyl phthalate resin and the like may be added. Similarly, acrylates such as trimethylolpropane triacrylate (TMPTA), pentaerythritol diacrylate monostearate, tetraethylene glycol diacrylate, various monomers such as styrene, and other general reactive diluents may be added. . To ensure preservation,
It is also possible to add in advance a polymerization inhibitor such as quinones, polyhydric phenols, and phenols (for example, JP-A-4-146951).

Although the ratio of the phenolic hydroxyl group to the (meth) acryloyl group in the (meth) acryloylated novolak resin used in the present invention is not particularly limited, the molar ratio of the phenolic hydroxyl group to the (meth) acryloyl group is not limited. Thus, the ratio is preferably in the range of 1: 9 to 9: 1, and more preferably in the range of 2: 8 to 5: 5.
When the ratio of the (meth) acryloyl group is more than the above range, the curability becomes good, but the adhesive strength based on the phenolic hydroxyl group is hardly obtained, and the softening point of the resin further decreases, and the syrup or sticky solid Becomes difficult to handle. Conversely, if the phenolic hydroxyl group is more than the above range, the curability will be insufficient, which is not preferable.

The proportion of 2-hydroxy-3-phenoxypropyl acrylate in the whole radically polymerizable resin used in the present invention is preferably in the range of 5 to 50% by weight. If the proportion is less than 5% by weight, when the anisotropic conductive adhesive is used, insufficient fluidity at the time of heating and an increase in curing shrinkage occur, and a sufficient adhesive strength cannot be obtained. On the other hand, if it exceeds 50%, sufficient connection reliability cannot be obtained due to a decrease in the crosslink density of the cured product.

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 organic peroxides for controlling the curability. It is also possible to add various polymerization inhibitors in advance to improve the storage stability. Further, in order to facilitate the work of dissolving the resin, it may be used after being diluted with a solvent or the like. 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 storage stability 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, and polyvinyl butyral resin. Butyl rubber, chloroprene rubber, polyamide resin, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinyl acetate resin, nylon, styrene-isoprene copolymer, styrene -Butylene-styrene block copolymer,
Styrene-ethylene-butylene-styrene block copolymer, polymethyl methacrylate resin and the like can be used. Considering properties such as adhesiveness and connection reliability when used as an anisotropic conductive adhesive among them, acrylonitrile-butadiene-methacrylic acid copolymer, polyester, polyamide resin, nylon, polyvinyl butyral resin, styrene-ethylene -Butylene-styrene block copolymer and the like can be more preferably 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 (2) and (3) is used.

[0023]

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[0024]

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Conditions for using the anisotropic conductive adhesive (connection temperature,
The chemical structure can be selected or changed depending on the connection time) and the types of the radical polymerizable resin and the thermoplastic elastomer used. Further, for the purpose of further improving the compatibility between the radical polymerizable resin and the thermoplastic elastomer, or improving the workability in producing an anisotropic conductive adhesive such as solvent solubility, an amine compound, a (meth) allyl compound,
A maleimide modified with a cyanate compound or the like can also be used. When the modified maleimide is used, an unreacted residue of the compound used for the modification may be removed.

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. Or their alloys, or metal oxides, carbon, graphite, glass or ceramic,
Plastic particles coated with a conductive material on the surface can be used. Appropriate particles, materials and amounts of these conductive particles can be selected according to the terminal spacing and terminal shape of the circuit to be connected, the thickness and material of the circuit material, 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.

[0028]

The present invention will be described below with reference to examples and comparative examples. (Example 1) [Preparation of anisotropic conductive adhesive film] In 700 parts by weight of methyl ethyl ketone, having a structure of the formula (1), a molar ratio of a phenolic hydroxyl group to a methacryloyl group was 3: 7.
80 parts by weight of a methacryloylated novolak resin having a phenolic hydroxyl group, 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, a molecular weight of 25,000 and a softening point of 120 ° C. 100 parts by weight of polyester, 5 parts by weight of 1,1-dimethylbutylperoxy-2,2-dimethylpropanoate, 100 parts by weight of bis (4-maleimidophenyl) ether
The parts by weight were dissolved to obtain a resin component solution. After uniformly dispersing 7 parts by weight of Ni / Au-plated polystyrene particles having an average particle size of 5 μm in this resin component solution, a thickness of 45 μm after drying on a polyethylene terephthalate film subjected to a release treatment is adjusted. The solution was cast and dried to obtain an anisotropic conductive adhesive film.

[Preparation of Evaluation Sample] The adherends were copper (polyimide) = 25/75 μm and 0.5 μm tin-plated TCP (pitch: 0.3 mm, number of terminals: 60) and 0.8
4 mm thick board (FR-4) Inner / outer copper foil 18 μm flash gold-plated PCB (0.30 mm pitch, 6 terminals)
0) and the crimping conditions are 130 ° C., 30 kg / cm
^2. Pressure bonding was performed for 15 seconds to obtain an evaluation sample.

[Evaluation] Adhesion force measurement: Evaluation was performed by a 90 ° peel test using an evaluation sample bonded at 130 ° C. Connection reliability:
Immediately after the preparation of the evaluation sample, and at 85 ° C and 85% humidity
The connection resistance value after being left in an atmosphere for 100 hours was measured.
If the connection resistance cannot be measured,
PEN). Storage stability: An evaluation sample was prepared using an anisotropic conductive adhesive film left in a film state at 25 ° C. for 7 days, and the connection resistance was measured immediately after the sample was prepared. Table 2 shows the results of these evaluations. The raw materials used are shown in Table 1.

[0031]

[Table 1]

[0032]

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[0033]

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[0034]

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[0035]

[Table 2]

(Examples 2 to 6 and Comparative Examples 1 to 4) The same operation as in Example 1 was performed with the compounding amounts shown in Table 2 to obtain anisotropic conductive adhesive films. The results of evaluating the obtained anisotropic conductive adhesive film in the same manner as in Example 1 are shown in Table 2.

[0037]

According to the present invention, a radical polymerizable resin,
Organic peroxide, thermoplastic elastomer, in a resin composition blended with maleimide, when heat-cured connection using an anisotropic conductive adhesive obtained by dispersing conductive particles, in the adhesive Since the radical polymerizable resin and the thermoplastic elastomer are compatibilized by the contained maleimide, and the maleimide itself is also cured, it is cured in a uniformly dispersed state, and has a phenolic hydroxyl group as the radically polymerizable resin (meth). By using an acryloylated novolak resin and 2-hydroxy-3-phenoxypropyl acrylate, an excellent adhesive force based on the hydroxyl group contained in these radically polymerizable resins can be obtained, so that connection can be made at a very low temperature and in a short time. ,
An anisotropic conductive adhesive excellent in adhesiveness, connection reliability, storage stability, and repairability can be obtained.

Claims (2)

[Claims] 1. An anisotropic conductive adhesive in which conductive particles are dispersed in a resin composition containing a radical polymerizable resin, an organic peroxide, a thermoplastic elastomer, and maleimide, wherein the radical polymerizable resin is An anisotropic conductive adhesive comprising: a (meth) acryloylated novolak resin having a phenolic hydroxyl group; and 2-hydroxy-3-phenoxypropyl acrylate. 2. An anisotropic conductive material according to claim 1, wherein the proportion of 2-hydroxy-3-phenoxypropyl acrylate in the radically polymerizable resin is in the range of 5 to 50% by weight. Adhesive.