JPH11100558A - Anisotropically conductive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive which when used in electric connection between microcircuits can perform the connection at a low temperature within a short time and shows excellent adhesiveness, reliability of connection, storage stability and suitability for repair by selecting an anisotropically conductive adhesive comprising a radical-polymerizable resin, an organic peroxide, a thermoplastic elastomer, an amine-modified maleimide resin and conductive particles, wherein the organic peroxide is a specified one. SOLUTION: The organic peroxide used is a compound represented by formula I (R<1> and R<2> are each Cn H2n+1 , formula III or formula IV, provided that they may be the same or different from each other; and n is an integer of 1 or greater) or formula II (R<3> and R<4> , which may be the same or different from each other, are each Cn H2n+1 , formula II or formula IV; and n is an integer of 1 or greater). Because this peroxide has the reduced tendency to react with unreacted amine in the amine-modified maleimide resin, the adhesive can resist deterioration in storage stability and curability and can perform bonding at a very low temperature within a short time.

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 been frequently used in 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. This is because the conventional 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 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 However, the connection reliability was low due to low reliability and the like, so that it could not withstand long-term environmental tests.

On the other hand, as the 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, these thermosetting types are practically compatible with both storage stability and resin curability.
Due to its curing reactivity, it is necessary to heat and cure at a temperature of 150 to 200 ° C. for about 30 seconds.
At the following temperatures, it was difficult to cure the resin in a practical connection time.

Further, regarding the storage stability, for example, B
F ₃ amine complex, dicyandiamide, organic acid hydrazide, a compound containing a latent curing agent such as an imidazole compound and the like have been proposed, but those with excellent storage stability require a long time or high temperature for curing, On the other hand, those which can be cured at a low temperature in a short time have a problem that storage stability is inferior, and all have advantages and disadvantages.

In addition to the above problems, in connection workability between fine circuits using a thermosetting type of anisotropic conductive adhesive, a member once connected due to a position shift 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.

[0008] In particular, recently, the LCD module has rapidly increased in size, definition, and frame width.
The miniaturization of the connection pitch and the narrowing of the connection have also progressed rapidly. For this reason, for example, in the connection between the LCD and the TCP, a connection pattern shift occurs due to the extension of TCP at the time of connection, and a member inside the LCD is thermally affected by the temperature at the time of connection because the connection portion is narrow. The problem has 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 by connecting at a lower temperature, for example,
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 (JP-A-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.

[0011] Further, as a material which enables low-temperature connection, a thermosetting anisotropic conductive material in which conductive particles are dispersed in an adhesive containing a radical polymerizable resin, an organic peroxide and a thermoplastic elastomer is dispersed. Although it is considered to use an adhesive, the radical polymerizable resin and the thermoplastic elastomer are phase-separated from each other due to a difference in compatibility at the time of heat bonding, so that sufficient bonding strength and connection stability cannot be obtained. There was a problem.

In order to solve this problem, a resin composition comprising a radically polymerizable resin, an organic peroxide and a thermoplastic elastomer is mixed with a maleimide which is compatible with both the radically polymerizable resin and the thermoplastic elastomer. Although it is considered to be contained, the solubility of the maleimide in the solvent, and the low melting point of the maleimide itself when connecting in a short time at a low temperature, the fluidity of the adhesive is insufficient during heat curing due to the high melting point of the maleimide itself, resulting in poor conduction. Cause a problem,
It was not practical for lower temperature connections.

[0013] These problems can be solved by using an amine-modified maleimide resin in which the solubility and melting point of the maleimide resin are improved. However, when unreacted amine is present in the amine-modified maleimide resin, the temperature is relatively low. When the organic peroxides represented by the formulas (3) and (4) activated by the above are used, the reactivity between the carboxy radical generated by thermal decomposition and the unreacted amine is high, resulting in an inactive compound Therefore, there has been a problem that the organic peroxide does not work effectively and curability is reduced. In order to avoid the above problems, when an organic peroxide that does not generate a carboxy radical, such as the formulas (5), (6) and (7), is used, the activation temperature is high and the low-temperature curability is high. However, there was a problem that an anisotropic conductive adhesive having excellent resistance could not be obtained.

[0014]

Embedded image

[0015]

Embedded image

[0016]

Embedded image

[0017]

Embedded image

[0018]

Embedded image

As a method for solving this problem, it has been proposed to purify and use an amine-modified maleimide resin. However, there are problems such as a complicated production process, a reduced yield, and an increased possibility of contamination with new impurities. At present, it has not been put to practical use.

That is, at present, curability, workability, adhesiveness,
A resin system that satisfies all requirements such as connection reliability in a well-balanced manner has not been obtained.
An anisotropic conductive adhesive excellent in connection reliability, storage stability, repairability and the like has not been obtained.

[0021]

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.

[0022]

Means for Solving the Problems The present inventors comprise a radical polymerizable resin and an organic peroxide, a thermoplastic elastomer, and an amine-modified maleimide resin compatible with both the radical polymerizable resin and the thermoplastic elastomer. The thermosetting anisotropic conductive adhesive obtained by adding conductive particles to the resin composition reacts with the unreacted amine present in the amine-modified maleimide resin and the radical generated from the organic peroxide. In order to avoid the problem that the curability has been reduced because of the change to a stable compound by performing, and when using an organic peroxide having low reactivity with an amine, the activation temperature is high and the temperature is low. As a result of various studies on the problem that curability could not be obtained, the organic peroxide of the thermosetting anisotropic conductive adhesive was expressed by the formula (1) or (2). By using those,
Of the two types of radicals (carboxy radical and alkyloxy radical) generated when these organic peroxides are activated, the alkyloxy radical is further cleaved to form an alkyl radical having high reactivity with the radical polymerizable resin. A thermosetting anisotropic conductive adhesive that is easy to generate, has a low reactivity with unreacted amines, effectively acts as a radical, and its organic peroxide is activated at a relatively low temperature. The present inventors have found that an agent can be obtained, and have reached the present invention.

That is, in an anisotropic conductive adhesive obtained by dispersing conductive particles in a resin composition comprising a radical polymerizable resin, an organic peroxide, a thermoplastic elastomer and an amine-modified maleimide resin, the formula (1) (2) The anisotropic conductive adhesive, wherein an organic peroxide having a structure represented by the formula (2) is used.

[0024]

Embedded image

[0025]

Embedded image

The radically polymerizable resin used in the present invention is not particularly limited. The radically polymerizable resin has at least one carbon-carbon double bond in the molecule and can be radically polymerized. And unsaturated polyester resins, diallyl phthalate and various acrylates. 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). Further curability,
Various monomers such as acrylates such as trimethylolpropane triacrylate (TMPTA), pentaerythritol diallylate monostearate, tetraethylene glycol diacrylate and pentaerythritol tetraacrylate, and styrene to improve fluidity and workability during heating Or a common reactive diluent.

The organic peroxide used in the present invention is not particularly limited as long as its chemical structure is represented by the formula (1) or (2). The activation temperature of the peroxide and the reactivity of the generated radical with the amine change. For example, an alkyl group having a structure containing more methyl groups in the alkyl group has a lower reactivity between the generated alkyloxy radical and the amine, and can be more preferably used. Examples of such an alkyl group include a 1,1,3,3 tetramethylbutyl group containing three or more methyl groups, a t-butyl group, and a t-hexyl group. On the other hand, when the number of methyl groups contained in the alkyl group is two or less, the reactivity between the generated alkyloxy radical and the amine is relatively high, which is not preferable. Examples of such an alkyl group include a dimethylbenzyl group, a linear alkyl group, and a cyclohexyl group. These organic peroxides can be used alone or as a mixture of two or more kinds for controlling the 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. The type and amount of the organic peroxide used in the present invention are naturally determined by the balance between the curability and preservability of the adhesive when each peroxide is compounded, or the compatibility with the resin. is there.

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.

The amine-modified maleimide resin used in the present invention is not particularly limited, but has an action of making the radical polymerizable resin and the thermoplastic elastomer compatible with each other, and is generally (8) or (9). One obtained by reacting a maleimide having a chemical structure exemplified in the formula with an amine is used. The amine is not particularly limited.
Primary amines, bifunctional primary amines, monofunctional secondary amines, difunctional secondary amines and the like can be mentioned, and one kind or a mixture of two or more kinds is used.

[0030]

Embedded image

[0031]

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, there is provided an anisotropic conductive adhesive in which conductive particles are dispersed in a resin composition comprising a radical polymerizable resin, an organic peroxide, a thermoplastic elastomer, and an amine-modified maleimide resin. Since the reaction between the organic peroxide used and the unreacted amine in the amine-modified maleimide resin is suppressed, a decrease in the storage stability and curability is prevented. Therefore, connection at extremely low temperature and in a short time is possible, and an anisotropic conductive adhesive excellent in adhesiveness, connection reliability, storage stability, and repairability can be obtained.

[0035]

The present invention will be described below with reference to examples and comparative examples. Example 1 A 50% solution of a vinyl ester resin having the structure of the formula (10) dissolved in
0 parts by weight, 5 parts by weight of an organic peroxide having a chemical structure represented by the formula (1) 1,1,3,3 tetramethylbutylperoxy-2-ethylhexanoate, acrylonitrile having a structure of the formula (11) A butadiene-methacrylic acid copolymer dissolved in methyl ethyl ketone was used to prepare a 20% solution of 500 parts by weight of an amine-modified maleimide resin obtained by reacting N-phenylmaleimide having the structure of formula (8) with 4,4 diaminodiphenylmethane. 350 parts by weight of a 20% solution dissolved in methyl ethyl ketone, average particle size 5μ
After mixing and uniformly dispersing 7 parts by weight of Ni / Au plated polystyrene particles having a thickness of 15 μm on a polyethylene terephthalate film which has been subjected to a release treatment, a thickness of 15 μm is obtained.
m to obtain an anisotropic conductive film.

[0036]

Embedded image

[0037]

Embedded image

Example 2 In place of the organic peroxide having the chemical structure represented by the formula (1), 2,5-dimethyl-2,5-di (2) having the chemical structure represented by the formula (2) An anisotropic conductive film was obtained in the same manner as in Example 1 except that 2-ethylhexanoylperoxy) hexanate was used.

(Comparative Example 1) Instead of the organic peroxide having the chemical structure represented by the formula (1) or (2),
(3) An anisotropic conductive film was obtained in the same manner as in Example 1, except that lauroyl peroxide having the chemical structure represented by the formula (3) was used.

Comparative Example 2 In place of the organic peroxide having the chemical structure represented by the formula (1) or (2),
(4) An anisotropic conductive film was obtained in the same manner as in Example 1, except that di (2-ethylhexylperoxy) dicarbonate having the chemical structure represented by the formula was used.

(Comparative Example 3) Instead of the organic peroxide having the chemical structure represented by the formula (1) or (2),
(6) An anisotropic conductive film was obtained in the same manner as in Example 1, except that di-t-butyl peroxide having the chemical structure represented by the formula was used.

(Preparation of Evaluation Sample) TC in which copper foil / polyimide = 25/75 μm is plated with tin of 0.4 μm
Cut into 2 mm width between P (pitch: 0.10 mm, number of terminals: 200) and 1.1 mm thick glass (hereinafter ITO glass) on which an indium / tin oxide film having a sheet resistance value of 30Ω is formed on the entire surface. With the anisotropic conductive film described above interposed, the temperature is 130 ° C. and 150 ° C., the pressure is 30 kg / cm ² ,
Heat and pressure bonding was performed under the condition of 20 seconds to prepare an evaluation sample.

(Method of Measuring Adhesive Strength) The obtained evaluation sample was peeled off by 90 ° at a pulling speed of 50 mm / min using Tensilon to determine the adhesive strength.

(Method of Evaluating Connection Reliability) The connection resistance was measured immediately after the evaluation sample was prepared and after being left at a temperature of 85 ° C. and a humidity of 85% for 100 hours. Those that could not be measured were regarded as poor conduction (OPEN). Table 1 shows the evaluation results of the above examples and comparative examples.

[0045]

[Table 1]

[0046]

According to the present invention, it is possible to provide a heat-curable anisotropic conductive adhesive which can be connected at a lower temperature and has excellent connection reliability and storage stability.

Claims (1)

[Claims] 1. An anisotropic conductive adhesive in which conductive particles are dispersed in a resin composition comprising a radical polymerizable resin, an organic peroxide, a thermoplastic elastomer, and an amine-modified maleimide resin, the formula (1) (2) The anisotropic conductive adhesive, wherein an organic peroxide having a chemical structure represented by the formula (2) is used. Embedded image Embedded image