JP3425546B2 - Anisotropic conductive adhesive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electrical connection between minute circuits such as connection between LCD (liquid crystal display) and TCP (tape carrier package) and connection between TCP and 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 need for various fine circuit connections, such as the connection between PCBs and PCBs, has increased dramatically, and anisotropic conductive adhesives in which conductive particles are dispersed in an adhesive resin have been used as the connection method. . In this method, an anisotropic conductive adhesive is sandwiched between the members to be connected and heated and pressed to maintain electrical insulation between adjacent terminals in the plane direction and electrically conduct between the upper and lower terminals. .

Anisotropic conductive adhesives have been frequently used for such purposes because soldering is not performed because the adherend does not have heat resistance, and in a fine circuit, electrical shorts occur between adjacent terminals. The reason is that the conventional connection methods such as the above cannot be applied. In recent years, in particular, LCD modules have rapidly become larger in screen size, higher in definition, and narrower in frame, and accordingly, finer connection pitch and narrower connection have also been rapidly advanced.

Therefore, for example, in the connection between the LCD and the TCP, the connection pattern is displaced due to the expansion of the TCP due to the heating at the time of connection, or the connection portion is narrow so that the members inside the LCD may be affected by the temperature at the time of connection. Problems such as thermal influences have arisen. Further, in the connection between TCP and PCB, since the PCB has become longer, the PCB and the LCD warp due to the heating at the time of connection, causing a problem that the TCP wiring is disconnected.

In order to solve these problems, there is a demand for an anisotropic conductive adhesive which can be connected at a lower temperature and in a shorter time while maintaining sufficient connection reliability. Anisotropic conductive adhesives are classified into thermoplastic type and thermosetting type. Recently, epoxy resin type thermosetting type, which is more reliable than thermoplastic type, is widely used. Has been. However, these epoxy resin-based thermosetting anisotropic conductive adhesives must be heated and cured at a temperature of 150 to 200 ° C. for about 30 seconds in order to achieve both storage stability and curability of the resin due to their curing reactivity. Was required, and it was difficult to cure the resin within a practical connection time at a temperature of 150 ° C. or less.

Further, regarding storage stability, for example, B
F ₃ amine complexes, dicyandiamide, organic acid hydrazides, compounds using latent curing agents such as imidazole compounds have been proposed, but those with excellent storage stability require long time or high temperature for curing. However, those that can be cured at low temperature and in a short time have the problem of poor storage stability, and both have advantages and disadvantages.

In addition to the above-mentioned problems, in connection workability of fine circuits using a thermosetting type anisotropic conductive adhesive, the connected members are damaged due to misalignment etc. In addition, there is a growing demand for peeling and rejoining (so-called repair) without damage. However, most thermosetting type anisotropic conductive adhesives have advantages such as high adhesive strength and high reliability, but on the other hand, it is extremely difficult to meet the seemingly contradictory requirement of ease of repair. Not obtained.

As the anisotropic conductive adhesive capable of low temperature connection, conductive particles are dispersed in an adhesive resin containing a cationically polymerizable substance and a sulfonium salt (JP-A-7-90237). ), Epoxy resin, etc. 4-
A dispersion of conductive particles in a (dialkylamino) pyridine derivative (Japanese Patent Laid-Open No. 4-189883) has also been proposed, but it has problems such as storage stability of adhesive resin and corrosion of connected circuit terminals. Has not reached.

As an anisotropic conductive adhesive which solves these problems and makes both low-temperature fast curing and storage stability compatible, and connection reliability and repairability compatible, radically polymerizable resins, organic peroxides, A thermosetting anisotropic conductive adhesive in which conductive particles are dispersed in an adhesive component composed of an oxide, a thermoplastic elastomer, and a maleimide resin has been proposed. However, at present, in particular, due to lack of adhesiveness, a resin system satisfying all of curability, workability, adhesiveness, connection reliability, etc. in a well-balanced manner has not been obtained. , And adhesion, connection reliability, storage stability,
There is an increasing demand for anisotropic conductive adhesives with excellent repairability.

[0010]

SUMMARY OF THE INVENTION The present invention has been made as a result of various studies in view of such problems of the prior art, and its purpose is to connect an LCD and a TCP, and to connect a TCP. For electrical connection between microcircuits such as the connection between PCB and PCB, it is possible to connect at a low temperature and in a short time, and it has excellent adhesiveness, connection reliability, storage stability, and repairability. It is intended to provide a conductive adhesive.

[0011]

Means for Solving the Problems Radical polymerizable resin,
An anisotropic conductive adhesive obtained by dispersing conductive particles in a resin composition composed of an organic peroxide, a thermoplastic elastomer, and a phosphoric acid ester represented by the formula (1) is added to the thermoplastic elastomer (2 ) With a phenoxy resin represented by the formula
The polyol represented by the formula (3) or the poly represented by the formula (4)
The present invention relates to an anisotropic conductive adhesive containing an ester polyol .

[0012]

[Chemical 5]

[Chemical 6]

[Chemical 7]

In a further preferred form, the phenoxy resin represented by the formula ( 2) has a number average molecular weight of 10,000 to 10
In the range of 100,000 and represented by the formula (3) or
The polyester polyol represented by the formula (4) has a number average molecular weight in the range of 1,000 to 100,000, and the phenoxy resin represented by the formula (2) and the polyol represented by the formula (3) or
The anisotropic conductive adhesive has a ratio with the polyester polyol represented by the formula (4) in the range of 1: 1 to 10: 1.

[0014]

[Chemical 8]

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below.
The phenoxy resin represented by the formula (2) is a tough and ductile thermoplastic resin having a high cohesive force, and has a hydroxyl group that enhances wetting and bonding with a polar adherend. Also,
It has excellent heat resistance, does not deteriorate even when the adhesive resin is heat-cured, and does not crystallize after cooling because it is an amorphous polymer,
A smooth coating film can be obtained, and film formation becomes easy. Further, they have found that the combined use of this with a polyol improves the adhesiveness at room temperature, which was insufficient when the phenoxy resin alone was insufficient. This is because the polyol has a hydroxyl group similarly to the phenoxy resin and is compatible with the phenoxy resin to improve the flexibility of the adhesive resin at around room temperature. However, since heat resistance is insufficient when polyol alone is used, it is essential to use it together with a phenoxy resin. Further, among the polyols, the polyester polyol having an ester bond in the molecular chain is more flexible than the other polyols, and therefore the adhesive strength is further improved.

By using a phenoxy resin and a polyol having these characteristics as a thermoplastic elastomer, it is possible to impart high adhesion and high toughness to the adhesive resin after curing, and to obtain anisotropic conductive having excellent adhesive strength and connection reliability. A transparent adhesive is obtained. The phenoxy resin preferably has a number average molecular weight in the range of 10,000 to 100,000. If the molecular weight is smaller than this range, the toughness is insufficient and the adhesive strength is reduced. Further, if the molecular weight is larger than this range, the resin fluidity at the time of thermocompression bonding becomes insufficient and the connection resistance increases.

Examples of the polyol include polyether polyol, polytetramethylene ether glycol, polyester polyol, acrylic polyol, polybutadiene polyol and the like. Among them, polyester polyol is preferable, and examples thereof include polycarbonate diol, polylactone polyol and the like. There is. The number average molecular weight of the polyol is preferably in the range of 1,000 to 100,000. When the molecular weight is smaller than this range, the moisture resistance becomes poor and the reliability decreases. Also. If the molecular weight is higher than this range, the flexibility imparting effect to the phenoxy resin at around room temperature is lost and the adhesive strength is reduced.

The ratio of phenoxy resin to polyol is preferably in the range of 1: 1 to 10: 1. When the proportion of the polyol is higher than this range, the heat resistance is lowered and the reliability is deteriorated. If the proportion of the polyol is lower than this range, the effect of imparting flexibility to the phenoxy resin at around room temperature is lost, and the adhesive strength is reduced.

The thermoplastic elastomer used in the present invention includes a phenoxy resin represented by the formula (2) and (3)
The polyol represented by the formula or the polyester represented by the formula (4)
There is no particular limitation other than using terpolyol , but as other components, for example, polyimide resin, polybutadiene, polypropylene, styrene-butadiene-styrene copolymer, polyacetal resin, 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, polymethylmethacrylate resin, etc. can be used.

The radically polymerizable resin used in the present invention is not particularly limited as long as it has at least one carbon-carbon double bond in the molecule and is radically polymerizable. May be used alone or in combination of two or more. Specific examples of radically polymerizable compounds include vinyl ester resins, unsaturated polyester resins, diallyl phthalate resins, acrylates such as urethane acrylate resins, maleimide resins, and (meth) acryloylated phenol novolac resins having a phenolic hydroxyl group. Can be mentioned. Among them, vinyl ester resin and urethane acrylate resin, which have both curability and storability, and heat resistance, moisture resistance and chemical resistance of the cured product, can be preferably used.

In order to improve the curability, the fluidity at the time of heating, and the workability, trimethylolpropane triacrylate (TMPTA), pentaerythritol diallylate monostearate, tetraethylene glycol diacrylate, pentaerythritol tetraacrylate, etc. It can be used by diluting it with various monomers such as acrylates and styrene, and general reactive diluents.
Furthermore, in order to ensure 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).

The organic peroxide used in the present invention is not particularly limited and, for example, 1,1,3,3
-Tetramethylbutylperoxy-2-ethylhexanate, t-butylperoxy-2-ethylhexanate, t-hexylperoxy-2-ethylhexanate, 1,1-bis (t-butylperoxy)- 3,3
Examples thereof include 5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, bis (4-t-butylcyclohexyl) peroxydicarbonate and the like.

These peroxides can be used alone or in admixture of two or more kinds of organic peroxides in order to control the curability. It is also possible to add various polymerization inhibitors in advance in order to improve the storability. Further, in order to facilitate the work of dissolving in resin, it can be diluted with a solvent or the like and used. The type and blending amount of the organic peroxide used in the present invention are determined by the balance between the curability and storability of the adhesive when each peroxide is blended.

Examples of the phosphoric acid ester of the present invention represented by the formula (1) include acid phosphooxyethyl methacrylate, acid phosphooxypropyl methacrylate, acid phosphooxypolyoxyethylene glycol monomethacrylate, acid phosphooxypolyoxypropylene glycol. Monomethacrylate etc.

The conductive particles used in the present invention are not particularly limited as long as they have conductivity, and various metals such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver and gold are used. And their alloys, or metal oxides, carbon, graphite, glass and ceramics,
A material in which a conductive material is coated on the surface of plastic particles can be applied. The particle size, material, and compounding amount of these conductive particles can be appropriately selected depending on the terminal interval and terminal shape of the circuit to be connected, the thickness and material of the circuit material, and the like.

Furthermore, in the anisotropic conductive adhesive of the present invention,
An appropriate amount of coupling agent may be added if necessary. The purpose of adding the coupling agent is to modify the adhesive property 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 preferably added and used, and examples thereof include epoxysilane-based, mercaptosilane-based, and acrylsilane-based (for example, β-
(3,4-Epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-
Methacryloxypropyltrimethoxysilane etc.) can be used.

According to the present invention, a radically polymerizable resin,
Heat curing using an anisotropic conductive adhesive obtained by dispersing conductive particles in a resin composition containing an organic peroxide, a phosphoric acid ester represented by the formula (1), and a thermoplastic elastomer. When connecting, a phenoxy resin represented by the formula (2) and a polyol represented by the formula (3) or a polyester polyol represented by the formula (4) in a thermoplastic elastomer.
Since it has excellent adhesive strength and connection reliability, it can be connected at extremely low temperature and in a short time, and it has excellent adhesiveness, connection reliability, storage stability, and repairability. A directional conductive adhesive is obtained.

[0028]

EXAMPLES The present invention will be described below with reference to examples. <Example 1> 120 parts by weight of a novolac type vinyl ester resin, 80 parts by weight of a phenoxy resin having a number average molecular weight of 30,000, and 10 parts of polyethylene glycol having a number average molecular weight of 3,000 were used.
5 parts by weight of caprolactone-modified meta-arlyloyloxyethyl acid phosphate, 1,1,3,3
4 parts by weight of tetramethylbutylperoxy-2-ethylhexanate was dissolved in 300 parts by weight of methyl ethyl ketone to obtain a resin component solution. In this resin component solution, 1 part by weight of Ni / Au-plated polystyrene particles having an average particle diameter of 5 μm was uniformly dispersed, and the thickness after drying was adjusted to 45 μm on a polyethylene terephthalate film subjected to a mold release treatment. After the solution was cast and dried, it was slit to obtain a film of anisotropic conductive adhesive having a width of 2 mm.

<Examples 2 to 13 and Comparative Examples 1 to 11> Using the substances shown in Table 1 and using the amounts shown in Table 2 in the same manner as in Example 1, films of anisotropic conductive adhesives were prepared. Got

[0030]

[Table 1]

[0031]

[Chemical 9]

[0032]

[Chemical 10]

[0033]

[Chemical 11]

[0034]

[Chemical 12]

<Evaluation> The evaluation sample was prepared as follows. The adherend is copper foil / polyimide = 25/75 μm
TCP with 0.5 μm tin plating (pitch 0.3
mm, 60 terminals) and 0.8 mm thick 4-layer board ((FR
-4) Inner / outer layer copper foil 18μm flash gold plated PC
B (pitch: 0.30 mm, number of terminals: 60)), and the pressure bonding conditions were 130 ° C., 30 kg / cm ² , and 15 seconds, to obtain an evaluation sample.

<Measurement of Adhesive Strength> An evaluation sample adhered at 130 ° C. was used for evaluation by a 90 ° peel test. <Connection reliability> Immediately after the evaluation sample was manufactured and at a temperature of 85
The connection resistance value was measured after standing for 100 hours in an atmosphere of 85 ° C. and 85% humidity. If the connection resistance value could not be measured, it was regarded as poor conduction (OPEN).

The evaluation results are summarized in Table 2.

[Table 2]

[0038]

EFFECT OF THE INVENTION By using the anisotropic conductive adhesive of the present invention, it is possible to connect at a low temperature and in a short time, and the anisotropic conductive adhesive has excellent adhesiveness, connection reliability, storage stability and repairability. An agent is obtained.

Front page continuation (51) Int.Cl. ⁷ identification code FI H01B 1/22 H01B 1/22 D 1/24 1/24 D (58) Fields investigated (Int.Cl. ⁷ , DB name) C09J 4 / 06 C09J 9/02 C09J 171/02-171/14 C09J 201/02-201/10 H01B 1/22 H01B 1/24

Claims (4)

(57) [Claims] 1. An anisotropic conductive adhesive comprising conductive particles dispersed in a resin composition comprising a radically polymerizable resin, an organic peroxide, a thermoplastic elastomer and a phosphoric acid ester represented by the formula (1). In the agent, a phenoxy resin represented by the formula (2) and a polyol represented by the formula (3) or a polyester polyol represented by the formula (4) are added to the thermoplastic elastomer.
The anisotropic conductive adhesive agent characterized by comprising a Le. [Chemical 1] [Chemical 2] [Chemical 3] [Chemical 4] 2. The anisotropic conductive adhesive according to claim 1, wherein the phenoxy resin represented by the formula (2) has a number average molecular weight in the range of 10,000 to 100,000. 3. A polyol represented by the formula (3) or the polyol
The anisotropic conductive adhesive according to claim 1, wherein the polyester polyol represented by the formula (4) has a number average molecular weight of 1,000 to 100,000. 4. A phenoxy resin represented by the formula (2), a polyol represented by the formula (3), or a phenoxy resin represented by the formula (4).
The ratio with the polyester polyol is 1: 1 to 10: 1
The anisotropic conductive adhesive according to claim 1, which is in the range of.