JP3419436B2 - Anisotropic conductive adhesive film - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive adhesive film. More specifically, the present invention relates to an anisotropic conductive adhesive film that can be sandwiched between circuits having narrow pitch wirings and can simultaneously achieve conduction and adhesion between circuits without mixing bubbles between the wirings. 2. Description of the Related Art An ITO terminal on a glass substrate of a liquid crystal panel is connected to a flexible substrate or a TCP (Tape carrier package).
When connecting two circuit elements and electrically connecting the terminals between them, as in the case of connecting the semiconductor chip to a terminal of the semiconductor chip or connecting the semiconductor chip to the motherboard by flip-chip bonding, a different material is used. Anisotropic conductive adhesive films have been widely used conventionally. In this case, the connection between the terminals is performed by sandwiching an anisotropic conductive adhesive film between the terminals and performing thermocompression bonding. Such an anisotropic conductive adhesive film is made of a thermosetting epoxy compound, a thermosetting agent, and a film-forming resin such as a rubber-based polymer or a high-molecular-weight solid epoxy resin (that is, a liquid at the temperature of thermocompression bonding). Polymer or resin that does not form)
And in a thermosetting insulating adhesive dissolved in an organic solvent,
It is produced by a casting method in which an anisotropic conductive adhesive composition in which conductive particles are uniformly dispersed is coated on a release sheet, dried and formed into a film. Here, as the thermosetting epoxy compound, a liquid or low-melting-point epoxy compound (that is, an epoxy resin which becomes liquid at the temperature at the time of thermocompression bonding) is used so as to follow the shape of the wiring at the time of thermocompression bonding. In addition, the film forming resin is expected to have an effect of suppressing an excessive flow of the liquid epoxy resin at the time of thermocompression bonding and an effect of pushing out bubbles (usually air) between wirings. [0004] The film thus produced has a structure in which linear polymers are entangled. [0005] In the case of the conventional anisotropic conductive adhesive film, when bonding circuit elements having a relatively large wiring space, some air is mixed between the wirings. However, since the bonding area can be secured to some extent not only on the wiring surface but also between the wirings, it was possible to suppress a remarkable decrease in bonding strength and an increase in conduction resistance. However, in recent years, the mounting density of circuit elements to be bonded with an anisotropic conductive adhesive film has become increasingly higher, and accordingly, the wiring pitch (not only the wiring surface width but also the space between wirings) has become very fine ( For example, the wiring pitch is about 50 μm, the wiring surface width is about 30 μm, and the space width is about 20 μm.
μm), when such circuit elements are adhered to each other with a conventional anisotropic conductive adhesive film, there is a problem that the intrusion of air between the wirings is inevitable more than before.
This is because although the anisotropic conductive adhesive composition required for producing a conventional anisotropic conductive adhesive film is prepared using a solvent, a rubber-based polymer that is a film-forming resin is used. This is because the solubility of the high-molecular weight epoxy resin in the solvent is lower than that of the liquid or low-melting point epoxy compound, and the content of the liquid or low-melting point epoxy compound and the thermosetting agent is secured to some extent. As a result, since the amount of the film-forming resin used is limited, it is not possible to sufficiently control the flow of the liquid or low-melting-point epoxy compound during thermocompression bonding, and it becomes insufficient to extrude bubbles from between the wirings. It also becomes difficult to sufficiently prevent the liquid or low melting point epoxy compound from protruding from the periphery of the film. An object of the present invention is to solve the above-mentioned problems of the prior art. Even when the present invention is sandwiched between circuits having narrow-pitch wirings, it is possible to prevent air bubbles from being mixed between the wirings. It is an object of the present invention to provide an anisotropic conductive adhesive film capable of simultaneously achieving conduction and adhesion of the film. [0008] The present inventor does not use a casting method using a solvent when forming an anisotropic conductive adhesive composition into a film, but uses a conventional rubber-based polymer. Polyfunctional acrylate compounds and photopolymerization initiators capable of forming a two-dimensional or three-dimensional network structure film in place of a film-forming resin forming a linear polymer entangled structure film, such as a high-molecular weight epoxy resin or a high molecular weight epoxy resin It has been found that the above-mentioned object can be achieved by forming a film by a photopolymerization method using, and the present invention has been completed. That is, the present invention provides the following components (a) to
(D) (a) a thermosetting epoxy compound, (b) a thermosetting agent for the epoxy compound of component (a), (c) a photopolymerizable polyfunctional acrylate compound, and (d) a polyfunctional acrylate compound. In an insulating adhesive containing a photopolymerization initiator for photopolymerizing a functional acrylate compound, an anisotropic conductive adhesive composition obtained by dispersing conductive particles is obtained by photopolymerizing into a film shape. An anisotropic conductive adhesive film is provided. Hereinafter, the present invention will be described in detail. The anisotropic conductive adhesive film of the present invention comprises the following components (a) to (d): (a) a thermosetting epoxy compound; (b) a thermosetting agent for the epoxy compound of component (a); c) dispersing conductive particles in an insulating adhesive containing a photopolymerizable polyfunctional acrylate compound and (d) a photopolymerization initiator for photopolymerizing the component (c) polyfunctional acrylate compound; Obtained by photopolymerizing the resulting anisotropic conductive adhesive composition into a film shape. This anisotropic conductive adhesive film is composed of a photopolymerizable polyfunctional acrylate compound of component (c).
This is a film having a structure in which a thermosetting epoxy compound of the component (a) and a thermosetting agent of the component (b) are held in a network having a three-dimensional or three-dimensional network structure. By providing such a structure to the anisotropic conductive adhesive film, unnecessary outflow of the thermosetting epoxy compound during thermocompression bonding between circuit elements can be suppressed, and bubbles between wirings can be sufficiently extruded. . The thermosetting epoxy compound as the component (a) constituting the insulating adhesive is a component for expressing the adhesive force and the adhesive force of the anisotropic conductive adhesive film. Thermosetting liquid or low-melting epoxy compound having at least two glycidyl groups, such as bisphenol A type epoxy compound, phenol novolak type epoxy compound, cresol novolak type epoxy compound, ester type used in conductive conductive adhesive film Epoxy compounds and the like can be preferably used. In addition, these compounds include monomers and oligomers. [0013] A thermosetting solid epoxy resin which is solid at the time of thermocompression bonding of the component (a) may be used in combination. The component (b) constituting the insulating adhesive
The thermosetting agent for the epoxy compound is a component that reacts with the epoxy compound of the component (a) during thermocompression bonding to be cured. As such a thermosetting agent, those which are conventionally used as a thermosetting agent for an epoxy resin in this type of anisotropic conductive adhesive film can be used. For example, amine type, acid anhydride type, Imidazole or its modified hardener can be used. Preferably, what is known as a latent thermosetting agent can be used. When the amount of the thermosetting agent for the epoxy compound of the component (b) is too small, the curing is insufficient and the electrical insulation property is reduced. When the amount is too large, the curing proceeds rapidly and the adhesive strength is reduced. Therefore, the amount is preferably 1 to 200 parts by weight, more preferably 10 to 100 parts by weight, based on 100 parts by weight of the thermosetting epoxy compound of the component (a). The photopolymerizable polyfunctional acrylate compound as the component (c) constituting the insulating adhesive is photopolymerized by irradiation with light such as ultraviolet rays to form a two-dimensional or three-dimensional network structure. It is a component that turns the adhesive composition into a film. As such a photopolymerizable polyfunctional acrylate compound, a monomer or oligomer having at least two functionalities of photopolymerizable acroyl group or methacryloyl group can be preferably used. For example, trimethylolpropane EO ( Ethylene oxide) modified (n =
1) Triacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, bisphenol A type EO-modified (n = 2) diacrylate, and the like. The amount of the photopolymerizable polyfunctional acrylate compound (c) used is too small relative to the total of 100 parts by weight of the thermosetting epoxy compound (a) and the thermosetting agent (b). When the amount is too large, the amount of the thermosetting epoxy compound of the component (a) decreases relatively, the adhesive strength decreases, and the conduction reliability also decreases. It is 1 to 50 parts by weight, more preferably 5 to 20 parts by weight. As the photopolymerization initiator of the component (d), a known photopolymerization initiator used for the photopolymerizable polyfunctional acrylate compound of the component (c) can be used. For example, cleavage-type photopolymerization initiators such as 2,2-dimethoxy-1,2-diphenylethan-1-one, benzoethyl ether, diethoxyacetophenone, benzyldimethylketal, benzyl, and benzophenone, and hydrogen-abstraction-type photopolymerization Initiators can be used. When the amount of the photopolymerization initiator of the component (d) is too small, the photopolymerization reaction of the component (c) does not occur.
If the amount is too large, a reaction occurs instantaneously to cause foaming, which causes a problem in the appearance of the film. Therefore, the amount is preferably 0.1 to 100 parts by weight of the photopolymerizable polyfunctional acrylate of the component (c).
10 to 10 parts by weight, more preferably 1 to 5 parts by weight. The insulating adhesive used in the present invention is:
Although composed of the above components (a) to (d), a monofunctional acrylate compound is required for the insulating adhesive in order to improve the mechanical properties (for example, flexibility) of the anisotropic conductive adhesive film. It can be added accordingly. As such a monofunctional acrylate, phenol EO-modified (n =
2) acrylate, 2-ethylhexyl carbitol acrylate, butyl acrylate, 2-ethylhexyl acrylate, a carboxyl group which is a reactive functional group,
An acrylate having a glycidyl group, an amino group, and a hydroxy group, such as acrylic acid, acroyloxyethyl phthalic acid, and 2-hydroxyethyl acrylate can be given. In order to improve the mechanical properties of the anisotropic conductive adhesive film, various resins not involved in photopolymerization or heat curing, such as phenoxy resin, may be used as the insulating adhesive. It can be added as appropriate. As the conductive particles dispersed in the insulating adhesive described above, known conductive particles used for this type of anisotropic conductive adhesive film can be used. For example, solder powder, nickel metal powder, gold / nickel-plated plastic particles, and conductive particles whose surface is insulated and coated can be used. The type and particle size depend on the use of the anisotropic conductive adhesive film. It can be selected as appropriate. The amount of the conductive particles used is preferably 0.1 to 100 parts by weight of the insulating adhesive in order to secure a good balance between the conductivity and the adhesive force of the anisotropic conductive adhesive film. It is 50 parts by weight, more preferably 2 to 10 parts by weight. The anisotropic conductive adhesive composition in which the above conductive particles are dispersed in an insulating adhesive is, for example, a component (a)
To (d) and other additives may be uniformly mixed by a conventional method to prepare an insulating adhesive, which may be uniformly mixed with a conductive particle by a conventional method. It may be prepared by simultaneously mixing (a) to (d), conductive particles and other additives. The anisotropic conductive adhesive film of the present invention comprises the above-mentioned anisotropic conductive adhesive composition comprising the component (c) of the photopolymerizable polyfunctional acrylate compound and the component (d) of a photopolymerization initiator. It is formed into a film by photopolymerization.
More specifically, the anisotropic conductive adhesive composition is applied in a layer form on a release sheet or the like by a normal application device such as a gravure coater, and irradiated with light such as ultraviolet light to start photopolymerization. Just fine. In this case, the photopolymerization rate of the photopolymerizable polyfunctional acrylate compound as the component (c) is preferably as close to 100% as possible, but does not adversely affect the electrical characteristics of the conductive joint of the anisotropic conductive adhesive film after film formation. limit,
In principle, even if the photopolymerization ratio is not 100%, for example, 90%
% Or 80%. The anisotropic conductive adhesive film of the present invention can be used in the same manner as a conventional anisotropic conductive adhesive film using a thermosetting epoxy compound as an adhesive or adhesive component. EXAMPLES Hereinafter, the anisotropic conductive adhesive film of the present invention will be specifically described with reference to examples. Examples 1 to 11 and Comparative Examples 1 and 2 (Production of anisotropic conductive adhesive film) Thermosetting epoxy compound (Epicoat 828, manufactured by Yuka Shell Epoxy) 5
0 parts by weight and an epoxy curing agent (Novacure HX3941)
HP, manufactured by Asahi Kasei Kogyo Co., Ltd.) and a polyfunctional acrylate compound (NKA-TMPT-3EO,
20 parts by weight of Shin-Nakamura Chemical Co., Ltd.) and 0.4 parts by weight of a photopolymerization initiator (Irgacure 651, Nippon Ciba Geigy) were blended to obtain a liquid insulating adhesive. 5 parts by weight of conductive particles (crosslinked polystyrene particles having an average particle size of 8 μm and plated with nickel / gold) were uniformly mixed with the insulating adhesive to obtain an anisotropic conductive adhesive composition. . The obtained anisotropic conductive adhesive composition was applied on a release film, and a 50 μm-thick release-treated polyester film was placed thereon.
(5, 30 μm) to adjust the thickness to a constant value, and further, using a 180 W / cm high-pressure ultraviolet lamp, irradiating ultraviolet rays at a dose of 2.0 J / cm ² , Polymerized. Thus, an anisotropic conductive adhesive film of Example 1 was obtained. The procedures of Example 1 described above were repeated, except that the components shown in Tables 1 to 3 were used as Examples 2 to 11 and Comparative Examples 1 and 2. As a result, the anisotropic conductive adhesive films of Examples 2 to 11 and Comparative Example 2 were obtained. However,
In the case of Comparative Example 1, the film was not formed and could not be used as an anisotropic conductive adhesive film. The anisotropic conductive adhesive film obtained in each of Examples 2 to 11 and Comparative Example 2 was cut to a width of 5 mm and a length of 100 mm with the release film attached, and the cut film was used as follows. A bonding operation was performed. (Adhesion between Circuit Board and ITO Glass) A single-sided release film was peeled off from a gold-plated flexible printed circuit board (made of polyimide) having wirings with connection pitches (μm) shown in Tables 4 to 6. The obtained anisotropic conductive adhesive film was temporarily bonded at 70 ° C. Furthermore, peeling off the release film on the other side, layering the conductor surface of ITO glass on it,
Thermocompression bonding was performed at a pressure of 20 kg / cm ² and a temperature of 180 ° C. for 10 seconds. With respect to the obtained thermocompression-bonded product, “the presence or absence of air bubbles at the thermocompression bonding portion”, “peel strength”, and “continuity reliability”
Was evaluated as shown below, and the results were shown in Tables 4-6.
Shown in "Presence or absence of bubbles in thermocompression bonding part" The bonding part of thermocompression bonding was observed from the ITO glass surface with a microscope of 200 times magnification.
The presence of air bubbles was checked. Measurement of "Peel Strength" A 10 mm wide cut was made on a flexible printed circuit board thermocompression-bonded on ITO glass, and 50 m in the 90 degree direction.
It was peeled off from the ITO glass surface at a speed of m / min, and the adhesive strength at that time was measured. In practice, the peel strength is (4
50 gf / cm). [Conductivity] A pressure cooker test was performed on the thermocompression-bonded article at 105 ° C., 100% humidity, and 6 hours, and the change in resistance was examined. If the increase in the resistance value is preferably 0.3Ω or less, rank it as “○”,
An unfavorable case of 0.5Ω or more was ranked as “×”. [Table 1] Example 1 2 3 4 5 Thermosetting epoxy compound EP828 * 1 50 50 50 50 50 Thermosetting agent for epoxy compound Nohapure HX3941HP * 2 50 50 50 50 50 Photopolymerizable polyfunctional acrylate compound NK A-TMPT-3EO * 3 20 10 30--KAYARAD TMPTA * 4---10 15 Monofunctional acrylate New Frontier PHE-2 * 5--5-10 Photopolymerization initiator Dolphin Cure 651 * 6 0.4 0.2 0.7 0.2 0.20 5.5 conductive particles (particle size = 8 µm) 5% cross-linked polystyrene (AuNi plating) 5 5 5 5 5 Table 1 Note: * 1 Yuka Shell Epoxy, * 2 Asahi Kasei Kogyo, * 3 Shin-Nakamura Chemical, * 4 Nippon Kayaku, * 5 Daiichi Kogyo Seiyaku, * 6 Nippon Ciba Geigy [Table 2] Example 6 7 8 9 10 Thermosetting epoxy compound EP828 * 1 50--50 50 Araldite CY184 * 7-50 50-- Thermal curing agent for epoxy compound Nohpe Cure HX3941HP * 2 50 50 50 50 50 50 Photopolymerizable polyfunctional acrylate compound NK A-TMPT-3EO * 3 - 20 - - - KAYARAD TMPTA * 4 15 - 10 - 5 NK ester A-400 * 8 - - - 25 25 monofunctional acrylate Aronix M-120 * 9 10 - - - 5 light Polymerization initiator Dolphin Cure 651 * 6 0.5 0.4 0.2 0.5 0.7 Conductive particles (particle size = 8 μm) 5% cross-linked polystyrene (AuNi plating) 5 5 5 5 5 * 1, * 1 to * 4 and * 6 are the same as in Table 1. * 7 Nippon Ciba-Geigy Co., Ltd. * 8 Shin-Nakamura Chemical Co., Ltd. Comparative Example Example 1 2 11 Thermosetting Epoxy Compound EP828 * 1 50 50 50 Thermosetting Agent for Epoxy Compound NOHAPURE HX3941HP * 2 50 50 50 Photopolymerizable Polyfunctional Acrylate Compound NK A-TMPT-3EO * 3 − −100 light Polymerization initiator Dolphin Cure 651 * 6-2 Phenoxy resin -10- Conductive particles (particle size = 8 μm) 5% cross-linked polystyrene (AuNi plating) 5 5 5 Table Note: * 1 to * 3 and * 6 are the same as Table 1. [Table 4] Example 1 2 3 4 5 Thickness of anisotropic conductive film (μm) 25 25 25 30 15 Connection pitch 80 μm Presence or absence of bubbles None None None None None Peel strength (gf / cm) 550 600 450 450 450 550 Conduction reliability ○ ○ ○ ○ ○ presence Mu nothingness NO NO No peel strength of the connection pitch 100μm bubbles (gf / cm) 750 650 550 450 550 conduction reliability ○ ○ ○ ○ ○ connection pitch 150μm bubble presence Mu nothingness NO NO No peel strength (gf / cm) 700 800 600 550 500 Conduction reliability ○ ○ ○ ○ ○ [Table 5] Example 6 7 8 9 10 Thickness of anisotropic conductive film (μm) 25 15 25 25 25 Connection pitch 80 μm Presence or absence of bubbles None None None None None Peel strength (gf / cm) 650 500 650 550 650 Conduction reliability ○ ○ ○ ○ ○ presence Mu nothingness NO NO No peel strength of the connection pitch 100μm bubbles (gf / cm) 700 650 750 550 750 conduction reliability ○ ○ ○ ○ ○ connection pitch 150μm bubble presence Mu nothingness NO NO No peel strength (gf / cm) 750 650 750 650 750 Conduction reliability ○ ○ ○ ○ ○ [Table 6] Note) Comparative Example 1 was not formed into a film and could not be pasted. As can be seen from Tables 4 to 6, Examples 1 to 1
The anisotropic conductive adhesive film of 0 showed excellent results in each of the evaluation items of presence / absence of bubbles, peel strength, and conduction reliability. In order to examine the influence on the presence or absence of air bubbles and the peel strength when the amount of the photopolymerizable polyfunctional acrylate compound was increased, the relative amount to the thermosetting epoxy compound was increased in Example 11. In the case of the anisotropic conductive adhesive film, bubbles between wirings can be removed,
Because the amount of the thermosetting epoxy compound decreases relatively,
It can be seen that the peel strength tends to decrease. On the other hand, in the case of Comparative Example 1 in which the photopolymerizable polyfunctional acrylate compound and the photopolymerization initiator were not used, the film was not formed, and thus could not be used as an anisotropic conductive adhesive film. As in Comparative Example 1, no photopolymerizable polyfunctional acrylate compound and no photopolymerization initiator were used.
In the case of Comparative Example 2 in which a phenoxy resin was used as the resin for film formation, air bubbles between the wirings could not be removed,
Therefore, peel strength and conduction reliability were insufficient. According to the anisotropic conductive adhesive film of the present invention, even when the film is sandwiched between circuits having narrow-pitch wirings, conduction between the circuits can be achieved without introducing air bubbles between the wirings. And adhesion can be achieved at the same time.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H01B 5/16 H01B 5/16 // C09J 4/02 C09J 4/02 (56) References JP-A-53-97035 (JP, A) JP-A-4-192212 (JP, A) JP-A-63-142084 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01B 1/20 C08F 2/48 C09J 7 / 02 C09J 9/02 C09J 163/00 H01B 5/16 C09J 4/02

Claims (1)

(57) [Claim 1] The following components (a) to (d) (a) a thermosetting epoxy compound, (b) a thermosetting agent for the epoxy compound of the component (a), c) dispersing conductive particles in an insulating adhesive containing a photopolymerizable polyfunctional acrylate compound and (d) a photopolymerization initiator for photopolymerizing the component (c) polyfunctional acrylate compound; the anisotropic conductive adhesive composition comprising, met anisotropic conductive adhesive film obtained by photopolymerizing the film shape
The insulating adhesive is a thermosetting epoxidized component (a).
1 to 2 parts by weight of the thermosetting agent of component (b) per 100 parts by weight of the compound
Polyfunctional acrylate of component (c)
The compound is combined with the thermosetting epoxy compound of the component (a) and the component
10 to 3 with respect to 100 parts by weight in total with the thermosetting agent of (b)
0 parts by weight, and the photoinitiator of component (d)
To 100 parts by weight of the polyfunctional acrylate compound of the component (c)
0.1 to 10 parts by weight, and anisotropic conductive adhesive
The composition contains conductive particles based on 100 parts by weight of the insulating adhesive.
Conductive adhesive film containing 0.5 to 50 parts by weight of particles
M