HK1134378B - Anisotropic conductive film and connection structure - Google Patents

Description

Anisotropic conductive film and connection structure

Technical Field

The present invention relates to an anisotropic conductive film having high adhesive strength obtained by dispersing conductive particles in a thermosetting acrylic resin composition, and a connection structure using the anisotropic conductive film.

This application claims priority from japanese patent application 2007-115929, which was filed on 25/4/2007 in the japanese country and is incorporated herein by reference.

Background

In the field of mounting technology, anisotropic conductive films have rapidly spread in terms of simplification of connection steps and lead-free. As such an anisotropic conductive film, an anisotropic conductive film containing a thermosetting epoxy resin composition is used in terms of connection reliability and heat resistance, but recently, attention has been paid to an anisotropic conductive film containing a thermosetting acrylic resin composition because of the demand for shortening of connection time and lowering of temperature.

This type of anisotropic conductive film can be used by selecting a material having a low decomposition and activation temperature from azo type initiators and peroxide type initiators as curing agents, and can be mounted by heating and pressing at a relatively low temperature of about 140 to 160 ℃ for 10 seconds or less for a short time.

However, the former anisotropic conductive film containing an acrylic resin composition has problems due to adhesive strength, such as a connection defect and low conduction reliability after connection, compared with the former anisotropic conductive film containing an epoxy resin composition.

In order to solve this problem, for example, as described in japanese patent No. 3587859, an anisotropic conductive film obtained by blending a hydroxyl group-containing resin having a molecular weight of 10000 or more with an acrylic resin composition and selecting a phosphorus-containing acrylate as an acrylic component (thermosetting component) has been studied.

As described above, although the anisotropic conductive film described in japanese patent No. 3587859 can be expected to improve the adhesive strength with an adherend such as an electronic substrate due to the presence of hydroxyl groups, it is required to improve the adhesive strength in a state where stress applied to the adherend is relaxed, that is, in a state where no bending occurs during actual mounting work, and thus the opposite problem of improving the adhesive strength in a state where stress is relaxed cannot be solved.

That is, in order to solve the problem of the opposite, it is considered that a polymer component having a molecular weight as high as possible needs to be blended with a resin material other than a component (curable component) causing curing shrinkage, and the anisotropic conductive film described in patent document 1 does not have a sufficiently high molecular weight. That is, patent document 1 describes that the miscibility of a polymer having a weight average molecular weight of 100 ten thousand or more is reduced and the incorporation is difficult. Patent document 1 describes that the acrylic rubber is compounded to relax stress and to improve cohesive force of the adhesive, but the molecular weight of the acrylic rubber is about 20 ten thousand.

In this manner, when the conventional anisotropic conductive film containing a thermosetting acrylic resin composition is used, it is difficult to improve the adhesive strength in a state where the stress is relaxed.

Disclosure of Invention

The purpose of the present invention is to provide an anisotropic conductive film that can improve the adhesive strength in a state where stress is relaxed, and a connection structure using the anisotropic conductive film.

The anisotropic conductive film according to the present invention contains a thermosetting acrylic resin composition containing at least (a) a thermosetting agent, (B) a thermosetting component, (C) a hydroxyl group-containing acrylic rubber, (D) organic fine particles, and (E) conductive particles, wherein the thermosetting component (B) contains (B1) a phosphorus-containing acrylate, the hydroxyl group-containing acrylic rubber (C) has a weight average molecular weight of 100 ten thousand or more, and the organic fine particles (D1) contain polybutadiene fine particles.

When the weight of each of the hydroxyl group-containing acrylic rubber (C), the phosphorus-containing acrylate (b1), and the polybutadiene fine particles (d1) constituting the anisotropic conductive film of the present invention is X, Y and Z, the weight ratio of these 3 components is X: Y: Z is 2:0.05:10 to 8:0.05: 16.

Further, the anisotropic conductive film according to the present invention may further contain (F) a phenoxy resin.

The connection structure according to the present invention is formed by connecting a substrate on which an electrode pattern is formed and an electronic element with the anisotropic conductive film.

The anisotropic conductive film according to the present invention contains a thermosetting acrylic resin composition, and contains (B1) a phosphorus-containing acrylate as (B) a thermosetting component and (D1) a polybutadiene-based fine particle as (D) an organic fine particle, whereby a high-molecular-weight acrylic rubber can be mixed in the acrylic resin composition, that is, (C) a hydroxyl-containing acrylic rubber having a weight average molecular weight of 100 ten thousand or more can be contained in the acrylic resin composition, and (C) a hydroxyl-containing acrylic rubber having a weight average molecular weight of 100 ten thousand or more can be contained in the acrylic resin composition, whereby a high adhesive strength can be obtained in a state where stress is relaxed.

In addition, in the anisotropic conductive film according to the present invention, the weight ratio of 3 components of (b1) the phosphorus-containing acrylate, (C) the hydroxyl group-containing acrylic rubber, and (d1) the polybutadiene fine particles is appropriate, whereby a high adhesive strength of 6N/cm or more can be obtained in a state where stress is relaxed.

Further, the anisotropic conductive film according to the present invention can further improve the film formability of the anisotropic conductive film by further containing (F) a phenoxy resin.

The connection structure according to the present invention can improve the connection reliability between the substrate and the electronic component and eliminate the difference between products by connecting the substrate on which the electrode pattern is formed and the electronic component by the anisotropic conductive film which can obtain high adhesion strength in a state where stress is relaxed.

Other objects of the present invention and advantages obtained by the present invention will be further apparent from the embodiments described below with reference to the drawings.

Drawings

FIG. 1 is a cross-sectional view of a connection structure using an anisotropic conductive film according to the present invention.

Detailed Description

The anisotropic conductive film and the connection structure using the same according to the present invention will be specifically described below. The anisotropic conductive film of the present invention is used for connecting a substrate having an electrode pattern containing ito (indium Tin oxide) to an electronic component, and the like, and specifically, is an anisotropic conductive film capable of improving adhesive strength in a state where stress is relaxed.

The components constituting the anisotropic conductive film will be specifically described below. The components are not limited to these descriptions.

The anisotropic conductive film contains, as components constituting the film, (a) a thermosetting agent, (B) a thermosetting component, (C) a hydroxyl group-containing acrylic rubber, (D) organic fine particles, (E) conductive particles, and (F) a phenoxy resin. The thermosetting component (B) contains a phosphorus-containing acrylate (B1), the hydroxyl group-containing acrylic rubber (C) has a weight average molecular weight of 100 ten thousand or more, and the organic fine particles (D) contain polybutadiene fine particles (D1).

Among them, the (F) phenoxy resin is not an essential component of the anisotropic conductive film of the present invention, but the film formability of the anisotropic conductive film can be improved by containing the (F) phenoxy resin.

Examples of the heat-curing agent (A) include azo initiators and peroxide initiators, which have low decomposition and activation temperatures. In view of low temperature and short time pressure adhesion, a peroxide initiator is preferable. Examples of the peroxide initiator include peroxides such as dibenzoyl peroxide, ditoluoyl peroxide, bis (4-methylbenzoyl) peroxide, bis (3, 5, 5-trimethylhexanoyl) peroxide and di-t-butyl peroxide. These may be used alone, or 2 or more.

(B) The thermosetting component is mainly composed of a liquid (meth) acrylate. Examples of the liquid (meth) acrylate include polyfunctional (meth) acrylates exemplified by alkyl-modified 2-or 3-functional (meth) acrylates, ethylene glycol-modified 2-or 3-functional (meth) acrylates, and polyester-modified 2-or 3-functional (meth) acrylates, and monofunctional (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, adamantyl (admantyl) meth acrylate, and hydroxyethyl (meth) acrylate. Among them, the 2-or 3-functional (meth) acrylate modified with ethylene glycol is particularly preferably used. These polyfunctional (meth) acrylates and monofunctional (meth) acrylates may be used alone or in combination of 2 or more.

Examples of the phosphorus-containing acrylate (b1) include mono (2-acryloyloxyethyl) acid phosphate, mono (2-acryloyloxypropyl) acid phosphate, and mono (2-acryloyloxybutyl) acid phosphate. The incorporation of the phosphorus-containing acrylate has an advantage of increasing the amount of adhesion to the surface of an inorganic substance such as a metal. The amount of the phosphorus-containing acrylate (b1) is preferably 0.01 to 0.5 parts by weight, more preferably 0.03 to 0.1 parts by weight, based on 60 parts by weight of the total of the resin and the liquid (meth) acrylate constituting the film component. When the amount is less than 0.01 part by weight, the solubility of the hydroxyl group-containing acrylic rubber is insufficient, and when the amount is more than 0.5 part by weight, the adhesive strength is lowered.

(C) The hydroxyl group-containing acrylic rubber is produced from an acrylic ester containing an alcoholic hydroxyl group and an acrylic ester containing a carboxyl group. The molecular weight is a weight average molecular weight of 100 ten thousand or more, more preferably 120 ten thousand or more, in a measurement by GPC (gel permeation chromatography). When the weight average molecular weight is 100 ten thousand or less, sufficient adhesive strength may not be obtained. The amount of the hydroxyl group-containing acrylic rubber (C) is 1 to 10 parts by weight, more preferably 2 to 8 parts by weight, based on 60 parts by weight of the total of the resin and the liquid (meth) acrylate that constitute the film component. When the amount is less than 1 part by weight, the adhesive strength may not be obtained, and when the amount is more than 10 parts by weight, the composition may not be dissolved in the liquid (meth) acrylate.

Examples of the organic fine particles (D) include polybutadiene fine particles, polystyrene fine particles, polyacrylate fine particles, and polyolefin fine particles. Among these, the (d1) polybutadiene-based fine particles are most preferable.

As the (E) conductive particles, conductive particles conventionally used for anisotropic conductive films can be used. Examples thereof include nickel particles, gold particles, solder particles, and resin particles coated with these metals. The surface of these particles can be coated with an insulating material. The particle diameter of these conductive particles is usually 2 to 10 μm, preferably 3 to 5 μm. The amount of the conductive particles is 1 to 50% by volume, preferably 1 to 30% by volume, based on 100% by volume of the total volume of the anisotropic conductive film (containing the conductive particles). If the amount is less than 1% by volume, the conductivity may not be obtained, and if the amount is more than 50% by volume, the insulation between the connection terminals may not be maintained.

As the phenoxy resin (F), phenoxy resins having a weight average molecular weight of 10000 to 120000 can be used, and among them, phenoxy resins having a weight average molecular weight of 40000 to 60000 are most preferable.

The thermosetting acrylic resin composition using the anisotropic conductive film of the present invention may contain a silane coupling agent for improving adhesion to a metal. The content of the silane coupling agent is preferably 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight, because if it is too small, a predetermined effect cannot be obtained and if it is too large, coatability is lowered, based on 35 parts by weight of the total components obtained by polymerizing and curing the (a) thermosetting agent, (B) thermosetting component, and (C) hydroxyl group-containing acrylic rubber in the resin composition.

When the weight of the hydroxyl group-containing acrylic rubber (C), the phosphorus-containing acrylate (b1), and the polybutadiene fine particles (d1) are X, Y and Z, respectively, a high adhesive strength (6N/cm or more) can be obtained by setting the weight ratio of these 3 components to X: Y: Z to 2:0.05:10 to 8:0.05:16, and an anisotropic conductive film having the above-described configuration in which the weight ratio of the 3 components is appropriately adjusted can obtain a high adhesive strength of 6/N/cm or more in a state where stress is relaxed.

The anisotropic conductive film of the present invention configured as described above contains a thermosetting acrylic resin composition containing at least (a) a thermosetting agent, (B) a thermosetting component, (C) a hydroxyl group-containing acrylic rubber, (D) organic fine particles, and (E) conductive particles, wherein (B1) a phosphorus-containing acrylate is contained in the thermosetting component, (C) the hydroxyl group-containing acrylic rubber has a weight average molecular weight of 100 ten thousand or more, and (D1) polybutadiene fine particles are contained in the organic fine particles (D), whereby high bonding strength can be obtained in a state where stress is relaxed.

That is, in the present invention, in view of the conventional attempt to blend a hydroxyl group-containing acrylic rubber having a weight average molecular weight of 100 ten thousand or more in the anisotropic conductive film containing a thermosetting acrylic resin composition in consideration of the miscibility (compatibility) of thermosetting components, but the miscibility with other components is insufficient, the present inventors have conducted extensive studies and as a result, have found that an acrylic rubber having a high molecular weight can be blended in an acrylic resin composition by blending a phosphorus-containing acrylate as a thermosetting component and a polybutadiene rubber in a particulate state, and thereby an anisotropic conductive film having the above-described effect of obtaining a high adhesive strength in a state where stress is relaxed can be provided.

In the anisotropic conductive film of the present invention, when the weight of (C) the hydroxyl group-containing acrylic rubber, (b1) the phosphorus-containing acrylate, and (d1) the polybutadiene fine particles is X, Y and Z, respectively, the weight ratio of these 3 components is X: Y: Z is 2:0.05:10 to 8:0.05:16, whereby a high adhesive strength (6N/cm or more) can be obtained in a state where stress is relaxed.

Further, the film formability of the anisotropic conductive film can be improved by further blending (F) a phenoxy resin with the anisotropic conductive film of the present invention.

The connection structure 2 to which the present invention is applied is configured by connecting the substrate 3 on which the electrode pattern is formed and the electronic component 4 with the anisotropic conductive film 1 configured as described above, as shown in fig. 1.

In this way, by applying the connection structure of the present invention, as described above, by obtaining the anisotropic conductive film having high adhesion strength in a state where stress is relaxed, and connecting the substrate on which the electrode pattern made of ITO is formed and the electronic component, it is possible to ensure good connectivity between the substrate and the electronic component, and to improve reliability of long-term connection.

< example >

The anisotropic conductive film of the present invention will be described in more detail with reference to examples. As shown in table 1, examples of the present invention and comparative examples 1 to 5 were used as comparative examples for comparison.

In the examples, Methyl Ethyl Ketone (MEK) was used as a solvent, and a phenoxy resin, a liquid acrylate, a peroxide initiator, a hydroxyl group-containing acrylic rubber, a phosphorus-containing acrylate, polybutadiene fine particles, a silane coupling agent, and conductive particles were added to 100 parts by weight of the solvent in the ratios (parts by weight) shown in Table 1 and mixed by a mixer, and the composition was coated on a release-treated polyethylene terephthalate film having a thickness of 50 μm using a wire bar coater, and dried at 80 ℃ for 5 minutes to produce an anisotropic conductive film having a thickness of 20 μm. In comparative examples 1 to 5, the production was carried out in the same manner as in examples except that the compositions used were changed as shown in table 1 with respect to the examples. In examples and comparative examples 1 to 5, the compatibility and adhesive strength of the formulations were measured as follows.

[ Table 1]

(parts by weight)

Teisan Resin SG-600 LB: mw: 120 ten thousand

Teisan Resin SG-280: mw: 90 ten thousand

Teisan Resin SG-790: mw: 52 ten thousand

(1) Compatibility

The compositions compounded in accordance with Table 1 were evaluated visually. The state where the hydroxyl group-containing acrylic rubber was dissolved and completely dispersed was "O", the state where a part of the hydroxyl group-containing acrylic rubber was not dissolved was "A", and the state where the hydroxyl group-containing acrylic rubber was not dissolved was "X".

From examples and comparative examples 3 and 4, it is clear that the presence of the phosphorus-containing acrylate and the organic fine particles is indispensable for making compatible the hydroxyl group-containing acrylic rubber having a weight average molecular weight of 100 ten thousand or more. As shown in table 1, in order to compatibilize the hydroxyl group-containing acrylic rubber having a weight average molecular weight of 100 ten thousand or more, a predetermined amount of a phosphorus-containing acrylate or organic fine particles must be blended. In the absence of either the phosphorus-containing acrylate or the organic fine particles, the hydroxyl group-containing acrylic rubber having a weight average molecular weight of 100 ten thousand or more could not be made compatible (comparative examples 3 and 4).

In comparative example 5, the organic fine particles were 1/2 of example, and the hydroxyl group-containing acrylic rubber was not completely compatible. From this result, it was found that the organic fine particles had to be 10 parts by weight or more relative to 5 parts by weight of the hydroxyl group-containing acrylic rubber. In the examples, it was confirmed that the hydroxyl group-containing acrylic rubber was compatible by using 10 parts by weight of the organic fine particles with respect to 5 parts by weight of the hydroxyl group-containing acrylic rubber.

(2) Adhesive strength

The anisotropic conductive films having the mixing ratios shown in table 1 were temporarily provided on ITO glasses obtained by providing an ITO film on a glass having a thickness of 0.7 mm. Then, an FPC (Flexible printed Circuit Board) having a pitch of 50 μm was bonded to the ITO glass through an anisotropic conductive film, and pressure bonding was performed under heating and pressure (tool temperature: 160 ℃, pressure: 4MPa, pressure bonding time: 4 seconds). The pressure-bonded FPC was cut into a width of 10mm, and the end portion of the FPC was pulled up in a direction of 90 ° with respect to the ITO glass surface using a tensile tester (Tensiolon, manufactured by Orientec corporation), and the adhesive strength was measured. The adhesive strength is shown in table 1.

Comparative examples 1 and 2 show examples in which the molecular weight of the hydroxyl group-containing acrylic rubber is lower than that of examples. It is considered that when the molecular weight is low, the cohesive force between the adherend interface and the molecules of the anisotropic conductive film is reduced, and the adhesive strength is reduced. It is considered that the use of the hydroxyl group-containing acrylic rubber having a low molecular weight also causes a network of the hydroxyl group-containing acrylic rubber in the anisotropic conductive film to be shortened. Further, as the hydroxyl group-containing acrylic rubber, the molecular weight Mw of Teisan Resin SG-600LB used in examples and the like was 120 ten thousand, the molecular weight Mw of Teisan Resin SG-280 used in comparative example 1 was 90 ten thousand, and the molecular weight Mw of Teisan Resin SG-790 used in comparative example 2 was 52 ten thousand.

On the other hand, as is clear from table 1, the adhesive strength increases as the molecular weight of the hydroxyl group-containing acrylic rubber increases (examples, comparative example 1, comparative example 2). It is considered that by increasing the molecular weight of the hydroxyl group-containing acrylic rubber, a network of the hydroxyl group-containing acrylic rubber in the anisotropic conductive film develops, and the cohesive force between the adherend and the anisotropic conductive film increases. Accordingly, it is considered that a high adhesive force is exhibited when the weight average molecular weight of the hydroxyl group-containing acrylic rubber is 100 ten thousand or more. Since the practical value of the adhesive strength of the anisotropic conductive film is 6N/cm or more, it is necessary to make the molecular weight of the hydroxyl group-containing acrylic rubber 100 ten thousand or more in order to obtain an adhesive strength of 6N/cm or more.

In comparative examples 3 to 5, the acrylic rubber containing a hydroxyl group was completely incompatible and an anisotropic conductive film could not be formed, and therefore, the adhesive strength could not be measured.

As described above, the anisotropic conductive film according to the embodiment of the present invention can contain a hydroxyl group-containing acrylic rubber having a weight average molecular weight of 100 ten thousand or more by mixing a high molecular weight acrylic rubber into an acrylic resin composition by containing a phosphorus-containing acrylate as a thermosetting component and a polybutadiene rubber in a particulate state, and can obtain a high adhesive strength in a state where stress is relaxed.

As described above, according to the present invention, it has been found that an anisotropic conductive film is produced by dissolving a hydroxyl group-containing acrylic rubber having a molecular weight of 100 ten thousand or more, which has been difficult to dissolve conventionally.

The anisotropic conductive film according to the present invention can improve the adhesive strength in a state where stress is relaxed, and can be used as a circuit connecting material for various electric and electronic devices.

Further, the present invention is not limited to the above-described embodiments described with reference to the drawings, and it will be apparent to those skilled in the art that various changes, substitutions, and equivalents can be made without departing from the appended claims and the spirit thereof.

Claims (3)

1. An anisotropic conductive film comprising a heat-curable acrylic resin composition containing at least (A) a heat-curing agent, (B) a heat-curing component, (C) a hydroxyl group-containing acrylic rubber, (D) organic fine particles, and (E) conductive particles,

the thermosetting component (B) contains (B1) a phosphorus-containing acrylate,

the weight average molecular weight of the acrylic rubber containing hydroxyl groups (C) is 100 ten thousand or more,

the organic fine particles (D) contain polybutadiene fine particles (D1),

when the weight of the hydroxyl group-containing acrylic rubber (C), the phosphorus-containing acrylate (b1), and the polybutadiene fine particles (d1) is X, Y and Z, respectively, the weight ratio of these 3 components is X: Y: Z of 2:0.05:10 to 8:0.05: 16.

2. The anisotropic conductive film according to claim 1, further comprising (F) a phenoxy resin.

3. A connection structure obtained by connecting a substrate having an electrode pattern formed thereon and an electronic component to each other through the anisotropic conductive film according to claim 1 or 2.