WO2020071271A1

WO2020071271A1 - Anisotropic conductive film, connection structure, and method for manufacturing connection structure

Info

Publication number: WO2020071271A1
Application number: PCT/JP2019/038143
Authority: WO
Inventors: 裕美久保出; 怜司塚尾
Original assignee: デクセリアルズ株式会社
Priority date: 2018-10-03
Filing date: 2019-09-27
Publication date: 2020-04-09

Abstract

This anisotropic conductive film is suitable for anisotropic conductive connection to a flexible plastic substrate on which are formed an electronic component having a bump, such as an image display element or an IC chip for driving, and a transparent electrode and wiring, the film having at least a conductive particle dispersion layer formed from an insulating resin layer and conductive particles dispersed therein. This anisotropic conductive film satisfies the following conditions. Condition (A): The modulus of elasticity of the conductive particles at 20% compression is 6000-15000 N/mm². Condition (B): The compression recovery rate of the conductive particles is 40-80%. Condition (C): The average particle diameter of the conductive particles is 1-30 μm. Condition (D): The minimum melt viscosity of the insulating resin layer is 4000 Pa∙s or less. Condition (E): The number density of the conductive particles is 6000-36000/mm².

Description

Anisotropic conductive film, connection structure, and method of manufacturing connection structure

The present invention relates to an anisotropic conductive film.

In response to demands for lighter and more curved image display panels, flexible plastic substrates have been adopted as substrates for mounting electronic components such as image display elements and driving IC chips. . As a typical example of such a plastic substrate, from the viewpoint of preventing thermal deformation and reflection, a polyethylene terephthalate film 20 and a polyimide film 22 on which a transparent electrode 21 is formed as shown in FIG. A plastic substrate 24 having a structure of being laminated with a urethane-based adhesive layer 23 is cited (Patent Document 1).

JP 2016-54288 A

By the way, it is widely used to anisotropically connect bumps of an IC chip to electrodes of a flexible plastic substrate as shown in FIG. 7 via an anisotropic conductive film in which conductive particles are dispersed in an insulating resin binder. Is being done. In this case, a large number of bumps are provided at a fine pitch on the IC chip, while an oxide film is formed on the electrode surface of the plastic substrate. For this reason, the IC chip is pressed into the plastic substrate with a relatively large pressure in order to reliably connect the bump and the electrode after the bump of the IC chip has penetrated the oxide film on the electrode surface of the plastic substrate.

For this reason, the rigidity of the IC chip is much higher than the rigidity of the plastic substrate, so the deformation at the plastic substrate side is increased due to the pressure at the time of connection, and the “wiring of the wiring at the plastic substrate side” or “insufficient pushing of particles”. There is a concern that such a problem may occur. Specifically, as shown in FIG. 8, a case where heating and pressing are performed to anisotropically conductively connect the bump B of the IC chip and the electrode 21 of the plastic substrate 24 via the anisotropic conductive film ACF. In addition, there is a possibility that the adhesive layer 23 of the plastic substrate 24 is removed outside the periphery of the bump B of the IC chip and the inverted dome-shaped thin portion 25 is formed (doming phenomenon). When such a doming phenomenon occurs, there is a concern that a crack may be generated in the vicinity of the shoulder 26 in the wiring 21a extending from the electrode 21. Further, in order to evaluate the conduction reliability of the anisotropic conductive connection, an indentation formed by conductive particles sandwiched between the electrode 21 and the bump B from the polyethylene terephthalate film 20 side is observed and evaluated. Although indentation indicating good connection is observed for the conductive particles 27a sandwiched between the bump B and the electrode 21 near the edge E of the pressing surface of the bump, With regard to the conductive particles 27b sandwiched between the bump B and the electrode 21 near the center C of the pressing surface, there is a concern that indentations indicating good connection (in other words, the sandwiching state of the conductive particles) may not be easily observed. Is done. When such indentations are not observed, there is a problem that even if there is good conduction, the evaluation of conduction characteristics (initial conduction, conduction reliability, etc.) must be low.

To eliminate these concerns, for example, (a) the viewpoint of adjusting the anisotropic conductive connection conditions, (b) the viewpoint of adjusting the structure and characteristics of the plastic substrate, and (c) the structure and characteristics of the IC chip And (d) adjusting the structure and properties of the anisotropic conductive film. However, when approaching from the viewpoint of (a), it is necessary to modify or newly introduce a manufacturing facility, and when approaching from the viewpoints of (b) and (c), it is an anisotropic conductive connection object. It is necessary to change the specifications of electronic components. Therefore, it is required to approach from the viewpoint of (d) without remodeling or newly installing a manufacturing facility or changing specifications of an electronic component to be anisotropically connected.

An object of the present invention is to solve the above-mentioned conventional problems. In particular, an electronic component having a bump, such as an image display element or a driving IC chip, is connected to an electrode (for example, a metal such as Ti or Ti / AL). Anisotropic conductive material suitable for anisotropic conductive connection to a flexible plastic substrate on which an electrode, a metal oxide electrode such as ITO, or a metal oxide electrode such as the above is oxidized. Anisotropic conductive film that has good anisotropic conductive connection without forming cracks in the wiring of the plastic substrate during anisotropic conductive connection and realizes high conduction reliability It is to provide a conductive film.

The present inventors, when performing anisotropic conductive connection using an anisotropic conductive film having a conductive particle dispersion layer composed of at least an insulating resin layer and conductive particles dispersed therein, the conductive particles Focusing on the point that will receive a compressive force in the thickness direction of the film, by controlling the elements that strongly affect the behavior when the conductive particles are subjected to compression, it can meet the object of the present invention By controlling the 20% compression elastic modulus, the compression recovery rate, the average particle diameter, the number density, and the minimum melt viscosity of the insulating resin layer of the conductive particles within specific numerical ranges under the assumption of the present invention, The inventors have found that the object can be achieved, and have completed the present invention.

That is, the present invention relates to an anisotropic conductive film having a conductive particle dispersion layer composed of at least an insulating resin layer and conductive particles dispersed therein, and the following conditions (a) to (e): Is provided.

<Conditions (a)>
20% compressive elasticity modulus of the conductive particles, 6000 N / mm ² or more 15000 N / mm ² that less is;
<Conditions (b)>
The compression recovery ratio of the conductive particles is 40% or more and 80% or less;
<Condition (C)>
The average particle diameter of the conductive particles is 1 μm or more and 30 μm or less;
<Condition (d)>
The minimum melt viscosity of the insulating resin layer is 4000 Pa · s or less; and <Condition (e)>
The number density of the conductive particles is not less than 6000 / mm ^{2 and not} more than 36000 / mm ² .

The present invention also provides a method for producing the above-described anisotropic conductive film of the present invention, which comprises a step of forming a conductive particle dispersed layer by pushing conductive particles into an insulating resin layer. In a preferred embodiment of this step, the conductive particles are held in a predetermined arrangement on the surface of the insulating resin layer, and the conductive particles are pressed into the insulating resin layer with a flat plate or a roller to form a conductive particle dispersion layer. A mode in which conductive particles are filled in a transfer mold, and the conductive particles are transferred to the insulating resin layer to hold the conductive particles in a predetermined arrangement on the surface of the insulating resin layer.

According to the present invention, further, the first electronic component, for example, an IC chip or an IC module, and the second electronic component, for example, a flexible plastic substrate are anisotropically formed through the anisotropic conductive film of the present invention. A connection structure is provided that is conductively connected.

異方性 The anisotropic conductive film of the present invention has a conductive particle dispersed layer at least composed of an insulating resin layer and conductive particles dispersed therein. In the anisotropic conductive film of the present invention, as the conductive particles held in the conductive particle dispersion layer, those having 20% compression elastic modulus, compression recovery rate and average particle diameter each in a specific numerical range are used, As the insulating resin layer holding such conductive particles, a resin having a minimum melt viscosity of a specific value or less is used, and the degree of holding the conductive particles in such insulating resin layer (in other words, the number density ) Is set within a specific range. Therefore, via the anisotropic conductive film of the present invention, an electronic component having a bump such as an image display element or a driving IC chip is anisotropically mounted on a flexible plastic substrate on which electrodes and wiring are formed. When the conductive connection is made, it is possible to prevent cracks from being generated in the wiring of the plastic substrate. In addition, it is possible to generate an indentation indicating a good anisotropic conductive connection, and it is possible to obtain a good conduction reliability evaluation at the time of the anisotropic conductive connection.

FIG. 1A is a plan view showing an arrangement of conductive particles of an anisotropic conductive film 10A of an example. FIG. 1B is a cross-sectional view of the anisotropic conductive film 10A of the example. FIG. 2 is a cross-sectional view of the anisotropic conductive film 10B of the example. FIG. 3 is a cross-sectional view of the anisotropic conductive film 10C of the example. FIG. 4 is a cross-sectional view of the anisotropic conductive film 10D of the example. FIG. 5 is a cross-sectional view of the anisotropic conductive film 10E of the example. FIG. 6 is a cross-sectional view of the anisotropic conductive film 10F of the example. FIG. 7 is a schematic sectional view of a plastic substrate. FIG. 8 is an explanatory diagram when an IC chip is anisotropically conductively connected to a plastic substrate.

異方性 The anisotropic conductive film of the present invention has a conductive particle dispersed layer at least composed of an insulating resin layer and conductive particles dispersed therein. As the conductive particles held in the conductive particle dispersion layer, the condition (a): “20% compression elastic modulus”, the condition (b): “compression recovery”, and the condition (c): “average particle diameter” Each having a specific numerical range is used, and as the insulating resin layer holding such conductive particles, the condition (d): “lowest melt viscosity” is used in a specific range, and such insulating resin layer is used. The condition (e): “number density” is set within a specific range as the extent to which the conductive particles are held in the conductive resin layer. Hereinafter, an example of the anisotropic conductive film of the present invention will be described in detail with reference to the drawings. In the drawings described later, the same reference numerals represent the same or equivalent components.

<Overall configuration of anisotropic conductive film>
FIG. 1A is a plan view illustrating the particle arrangement of the anisotropic conductive film 10A according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line XX. 2 and 3-4 are cross-sectional views of the anisotropic

conductive films

10B, 10C, and 10D of the embodiment of the present invention, respectively. The anisotropic conductive film of the present invention is not limited to the embodiments disclosed in these drawings.

The anisotropic conductive film 10A may be in the form of a long film having a length of, for example, 5 m or more, and may be a wound body wound around a core.

The anisotropic conductive film 10A is composed of the conductive particle dispersion layer 3, in which the conductive particles 1 are in non-contact with the insulating resin layer 2. Preferably, conductive particles 1 are regularly arranged in a state where conductive particles 1 are exposed on one surface of insulating resin layer 2. The conductive particles 1 are not in contact with each other in plan view of the film, and the conductive particles 1 are also present in the film thickness direction without overlapping each other. Preferably, the conductive particles 1 constitute a single conductive particle layer in which the positions in the film thickness direction are aligned. The ratio (number basis) of the conductive particles that are not in contact with each other is preferably 95% or more, and more preferably 98% or more.

On the surface 2a of the insulating resin layer 2 around each conductive particle 1, a recess 2b may be formed with respect to the tangent plane 2p of the insulating resin layer 2 at the center between adjacent conductive particles ( (FIG. 1B, FIG. 2). Further, the top 1a of the conductive particles 1 may be flush with the surface 2a of the insulating resin layer 2 as shown in FIG. At the time of connection, movement of the conductive particles due to resin flow can be reduced. As described later, in the anisotropic conductive film of the present invention, a recess 2c may be formed on the surface of the insulating resin layer immediately above the conductive particles 1 embedded in the insulating resin layer 2. 3, FIG. 4). In the case of FIG. 3, one point of the top 1a of the conductive particle 1 may be exposed from the insulating resin layer.

<Conductive particles>
As the conductive particles 1, metal-coated resin particles having a metal layer formed on the surface of the resin core particles can be appropriately selected from the conductive particles used in known anisotropic conductive films. As such metal-coated resin particles, those whose surfaces have been subjected to an insulating coating treatment (for example, an insulating fine particle adhesion treatment, an insulating resin coating treatment, etc.) can also be used. Two or more kinds of metal-coated resin particles can be used in combination. Further, as the conductive particles 1, conductive particles having conductive protrusions on the surface can also be used. For example, conductive particles in which insulating particles serving as a core material of the protrusions are adhered to the surface of the resin core particles and the whole is coated with a conductive layer; conductive particles in which the surface of such conductive particles is further coated with another conductive layer; Alternatively, conductive particles or the like, in which insulating particles serving as a core material of the projections are adhered to the surface of the resin core particles coated with the conductive layer, and the whole is further coated with the conductive layer, can be used. The conductive layer may be two or more layers. The protrusion may be present between the conductive layers. Such a conductive layer can be formed on the surface of the resin core particles by a known film forming method such as electroless plating, electrolytic plating, and sputtering. In addition, there is also a method of attaching conductive fine particles, and there is no particular limitation as long as the conductive particles satisfy the conditions described below and can satisfy conduction performance. Further, the surface of the conductive layer may be subjected to a known insulating treatment. In this case, the size excluding the thickness of the insulating layer formed by the insulating treatment is defined as the particle size of the conductive particles.

導電 The conductive particles 1 used in the present invention satisfy the following conditions (a) to (c).

<Conditions (a)>
The conductive particles used in the present invention have a lower limit of the 20% compression modulus (K) from the viewpoint that even if an oxide film is formed on the surface of an electrode or a terminal of an electronic component, the conductive particles break through the oxide film. 6000 N / mm ² or more, preferably 10000 N / mm ² or more. Here, the 20% compression modulus is determined when a compressive load is applied to the conductive particles using a micro compression tester (for example, Fisher Scope H-100 manufactured by Fischer) (for example, a cylinder (diameter: 50 μm, made of diamond)). Of the conductive particles when the conductive particles are compressed under the conditions of a compression speed of 2.6 mN / sec and a maximum test load of 10 gf) at the end face of the smoothing indenter, and the numerical value obtained by the measurement is as follows: It can be calculated by applying to equation (1).

In the formula (1), F is a load value (N) when the conductive particles are compressed and deformed by 20%, S is a compressive displacement (mm) when the conductive particles are compressed and deformed by 20%, and R is a conductive displacement. (Mm).

<Conditions (b)>
In addition, since the conductive particles used in the present invention are required to break through the oxide film formed on the surface of the electrode or terminal of the electronic component as described above, a corresponding pressure is applied to the conductive particles during connection. This is expected to flatten the conductive particles. Therefore, after the pressure of the connection is released, the conductive particles are required to be restored after compression in order to secure a sufficient contact area with the facing electrode or terminal surface. From this viewpoint, the lower limit of the compression recovery ratio (X) is 40% or more, preferably 55% or more. Further, if the upper limit is too high, there is a risk that the connection state maintained by the cured or polymerized resin may be impaired, so it is not desirable that the upper limit is too high, and the upper limit is 80% or less, preferably 75% or less. It is. Here, the compression recovery rate is determined by compressing the conductive particles on the end face of a smooth indenter of a cylinder (diameter: 50 μm, made of diamond) using the above-mentioned micro-compression tester, and from the initial load (load 0.4 mN) to the load reversal. The displacement (L2) up to (load 5 mN) and the displacement (L1) from load reversal to final load (load 0.4 mN) are measured, and the numerical value obtained by the measurement is expressed by the following equation (2). Can be calculated by applying

<Condition (C)>
The lower limit of the average particle diameter of the conductive particles 1 used in the present invention is 1 μm or more, and preferably 2.5 μm or more, from the viewpoint of coping with the variation in wiring height. From the viewpoint of suppressing occurrence of short-circuit, the upper limit is 30 μm or less, preferably 9 μm or less. Here, the average particle size can be determined using a general particle size distribution measuring device (for example, FPIA-3000 (Malvern Panicalical)). The number of measurement samples is preferably 1000 or more. The average particle diameter D of the conductive particles in the anisotropic conductive film can be determined using an electron microscope such as a SEM. In this case, the number of measurement samples is preferably 200 or more. In the case where conductive particles having insulating fine particles adhered to the surface thereof are used, the average particle size of the conductive particles in the present invention means an average particle size not including the surface insulating fine particles.

<Insulating resin layer 2>
In the anisotropic conductive film of the present invention, the insulating resin layer 2 that holds the conductive particles 1 and functions as a base layer of the anisotropic conductive film may be formed from a curable resin composition as described later. It satisfies the following condition (d).

<Condition (d)>
With respect to the minimum melt viscosity of the insulating resin layer 2 constituting the anisotropic conductive film of the present invention, the upper limit thereof is to reduce the pressure at the time of connection, particularly when the substrate is made of plastic, etc. It is 4000 Pa · s or less, and preferably 3000 Pa · s or less, from the viewpoint of enabling good pushing of the conductive particles. In addition, the lower limit is preferably not particularly limited since it is desirable from the viewpoint of suppressing deformation of the plastic substrate, particularly in connection with the plastic substrate, and may be appropriately adjusted, but the conductive particles to be sandwiched between the terminals during anisotropic conductive connection From the viewpoint of preventing 1 from being excessively flown by the resin flow as well as from the viewpoint of preventing the resin from overflowing when wound into a wound body, preferably 200 Pa · s or more, more preferably 400 Pa · s or more It is. Here, the minimum melt viscosity can be obtained by using a rotary rheometer (manufactured by TA Instruments) as an example, using a measurement plate having a diameter of 8 mm, keeping the measurement pressure constant at 5 g, and more specifically, In a temperature range of 30 to 200 ° C., the temperature can be determined by setting the temperature to 10 ° C./min, the measurement frequency to 10 Hz, and the load on the measurement plate to 5 g.

When the conductive particles 1 are pressed into the insulating resin layer 2 to form the conductive particle dispersed layer 3 of the anisotropic conductive film 10A, the insulating resin layer 2 when the conductive particles 1 are pressed is When the conductive particles 1 are pushed into the insulating resin layer 2 so that the resin particles are exposed from the insulating resin layer 2 with the exposed diameter Lc, the insulating resin layer 2 is plastically deformed and the insulating resin layer around the conductive particles 1 is deformed. 2 or a high-viscosity viscous material such that a recess 2b (FIGS. 1B and 2) is formed, or the conductive particles 1 are buried in the insulating resin layer 2 without being exposed from the insulating resin layer 2. When the conductive particles 1 are pushed into the insulating resin layer 2 immediately above the conductive particles 1, a high viscosity viscous body is formed such that a recess 2c (FIGS. 3 and 4) is formed on the surface of the insulating resin layer 2. Therefore, the viscosity at 60 ° C. of the insulating resin layer 2 is preferably set to 3,000 to 20,000 Pa · s. This measurement is carried out in the same manner as the lowest melt viscosity, and can be determined by extracting a value at a temperature of 60 ° C.

具体 The specific viscosity of the insulating resin layer 2 when the conductive particles 1 are pressed into the insulating resin layer 2 can be determined with reference to the description of Japanese Patent No. 6187665 (paragraph 0054).

As described above, since the recesses 2b (FIGS. 1B and 2) are formed around the conductive particles 1 exposed from the insulating resin layer 2, the conductive particles 1 can be connected between terminals during anisotropic conductive connection. Since the resistance received from the insulating resin to the flattening of the conductive particles 1 generated when the conductive particles 1 are pinched is reduced as compared with the case where the recess 2b is not provided, the conductive particles are easily pinched at the terminals, so that conduction is achieved. The performance is improved, and the trapping property is improved.

Further, since the recess 2c (FIGS. 3 and 4) is formed on the surface of the insulating resin layer 2 immediately above the conductive particles 1 buried without being exposed from the insulating resin layer 2, the recess 2c does not exist. As compared with the case, the pressure at the time of anisotropic conductive connection is more likely to concentrate on the conductive particles 1, and the conductive particles 1 are more easily pinched between the terminals, so that the trapping property is improved and the conduction performance is improved.

(Thickness of insulating resin layer)
In the anisotropic conductive film of the present invention, the ratio (La / D) between the layer thickness La of the insulating resin layer 2 and the average particle diameter D of the conductive particles 1 is 0 if the amount of resin capable of holding the conductive particles is sufficient. 0.3 or more, preferably 0.6 or more, and more preferably 1.0 or more. If La / D is less than 0.3, it may be difficult to precisely maintain the conductive particles 1 in a predetermined particle dispersion state or a predetermined arrangement by the insulating resin layer 2. Here, the average particle diameter D is defined by the size of the metal-coated resin particles (the size of the resin core particles and the conductive layer on the surface thereof). If the layer thickness La of the insulating resin layer 2 is excessively large with respect to the conductive particles, the conductive particles are likely to be displaced during anisotropic conductive connection, and the ability of the terminal to capture the conductive particles is reduced. Therefore, the upper limit of La / D is preferably 8.0 or less, and more preferably 6.0 or less.

(Composition of insulating resin layer)
The insulating resin layer 2 can be formed from a curable resin composition, for example, from a thermopolymerizable composition containing a thermopolymerizable compound and a thermopolymerization initiator. The thermopolymerizable composition may contain a photopolymerization initiator as needed.

When a thermal polymerization initiator and a photopolymerization initiator are used in combination, those that also function as a photopolymerizable compound may be used as the thermopolymerizable compound, and the photopolymerizable compound is contained separately from the thermopolymerizable compound. You may. Preferably, a photopolymerizable compound is contained separately from the thermopolymerizable compound. For example, a cationic polymerization initiator is used as a thermal polymerization initiator, an epoxy resin is used as a thermopolymerizable compound, a photoradical polymerization initiator is used as a photopolymerization initiator, and an acrylate compound is used as a photopolymerizable compound.

複数 As the photopolymerization initiator, a plurality of types that react to light having different wavelengths may be contained. Thereby, the wavelength used in the photocuring of the resin constituting the insulating resin layer during the production of the anisotropic conductive film and the photocuring of the resin for bonding the electronic components together at the time of the anisotropic conductive connection. You can use them properly.

光 In the photocuring at the time of producing the anisotropic conductive film, all or a part of the photopolymerizable compound contained in the insulating resin layer can be photocured. Due to this photocuring, the arrangement of the conductive particles 1 in the insulating resin layer 2 is held or fixed, and short-circuit suppression and improvement in capture are expected. In addition, the viscosity of the insulating resin layer in the process of manufacturing the anisotropic conductive film may be appropriately adjusted by the photocuring.

は The content of the photopolymerizable compound in the insulating resin layer is preferably 30% by mass or less, more preferably 10% by mass or less, and particularly preferably less than 2% by mass. This is because if the amount of the photopolymerizable compound is too large, the thrust for pushing in at the time of connection increases.

Examples of the thermopolymerizable composition include a thermoradical polymerizable acrylate composition containing a (meth) acrylate compound and a thermoradical polymerization initiator, and a thermocation polymerizable epoxy system containing an epoxy compound and a thermocation polymerization initiator. And the like. A thermal anionic polymerizable epoxy composition containing a thermal anionic polymerization initiator may be used instead of the thermal cationic polymerizable epoxy composition containing a thermal cationic polymerization initiator. In addition, a plurality of types of polymerizable compositions may be used in combination as long as there is no particular problem. Examples of the combination include a combination of a thermocationically polymerizable composition and a thermoradical polymerizable composition.

Here, as the (meth) acrylate compound, a conventionally known thermopolymerizable (meth) acrylate monomer can be used. For example, a monofunctional (meth) acrylate monomer or a bifunctional or higher polyfunctional (meth) acrylate monomer can be used.

Examples of the thermal radical polymerization initiator include organic peroxides and azo compounds. In particular, an organic peroxide that does not generate nitrogen that causes bubbles can be preferably used.

If the amount of the thermal radical polymerization initiator is too small, curing will be poor, and if it is too large, the product life will be shortened. Therefore, it is preferably 2 to 60 parts by mass, more preferably 100 parts by mass of the (meth) acrylate compound. It is 5 to 40 parts by mass.

Examples of the epoxy compound include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak type epoxy resin, modified epoxy resin thereof, alicyclic epoxy resin and the like, and two or more of these may be used in combination. it can. An oxetane compound may be used in addition to the epoxy compound.

As the thermal cationic polymerization initiator, those known as thermal cationic polymerization initiators for epoxy compounds can be employed.For example, using an iodonium salt, a sulfonium salt, a phosphonium salt, a ferrocene, or the like that generates an acid by heat is used. In particular, an aromatic sulfonium salt having a good potential with respect to temperature can be preferably used.

If the amount of the thermal cationic polymerization initiator is too small, curing tends to be poor, and if it is too large, the product life tends to decrease. Therefore, the amount is preferably 2 to 60 parts by mass relative to 100 parts by mass of the epoxy compound. Parts, more preferably 5 to 40 parts by mass.

The thermopolymerizable composition preferably contains a film-forming resin and a silane coupling agent. Examples of the film-forming resin include a phenoxy resin, an epoxy resin, an unsaturated polyester resin, a saturated polyester resin, a urethane resin, a butadiene resin, a polyimide resin, a polyamide resin, and a polyolefin resin. be able to. Among these, a phenoxy resin can be preferably used from the viewpoints of film formability, workability, and connection reliability. The weight average molecular weight is preferably 10,000 or more. Examples of the silane coupling agent include an epoxy silane coupling agent and an acrylic silane coupling agent. These silane coupling agents are mainly alkoxysilane derivatives.

The thermopolymerizable composition may contain an insulating filler for adjusting the melt viscosity. Examples of the insulating filler include silica powder and alumina powder. The size of the insulating filler is preferably 20 to 1000 nm in particle size, and the blending amount is preferably 5 to 50 parts by mass with respect to 100 parts by mass of a thermopolymerizable compound (and a photopolymerizable compound) such as an epoxy compound. .

Furthermore, a filler, a softener, an accelerator, an antioxidant, a colorant (pigment, dye), an organic solvent, an ion catcher agent and the like different from the above-mentioned insulating filler may be contained.

<Degree of retention of conductive particles by insulating resin layer>
The insulating resin layer 2 having the above-described minimum melt viscosity holds the conductive particles 1 as described above, and the degree of the holding can be evaluated using the number density as an index. That is, in the anisotropic conductive film of the present invention, the following condition (e) is satisfied with respect to the number density of the conductive particles 1.

<Conditions (e)>
The lower limit of the number density of the conductive particles in the anisotropic conductive film of the present invention in the film plan view is 6000 particles / mm ² or more, because if the number density is too small, the number of trapped particles may decrease and the conduction resistance may increase. It becomes 7500 pieces / mm ² or more. If the number density is too high, it is necessary to increase the pressure at the time of connection. If the substrate is made of plastic or the like, there is a concern about deformation, so that the pressure at the time of connection is not excessively increased. ² or less, preferably 30000 pieces / mm ² or less. Here, the number density of the conductive particles may be obtained by observing using a metallographic microscope or by measuring the observed image using image analysis software (WinROOF, Mitani Corporation). The observation method and the measurement method are not limited to the above.

In addition, as a measurement region of the number density of the conductive particles, a rectangular region having one side of 100 μm or more is arbitrarily set at a plurality of positions (preferably 5 or more, more preferably 10 or more), and the total area of the measurement region is 2 mm. It is preferred to be ² or more. The size and number of the individual regions may be appropriately adjusted depending on the state of the number density. As an example of a case where the number density for a fine pitch application is relatively large, 200 images (2 mm ² ) of an area having an area of 100 μm × 100 μm arbitrarily selected from the anisotropic conductive film 10 </ ^b > A are observed using a metallographic microscope or the like. By measuring the number density and averaging it, the “number density of the conductive particles in plan view” in the above equation can be obtained. A region having an area of 100 μm × 100 μm is a region where one or more bumps are present in a connection target having a space between bumps of 50 μm or less and an L / S (line / space) of 1 or less.

<Dispersion state of conductive particles in insulating resin layer>
The dispersion state of the conductive particles 1 in the conductive particle dispersion layer 3 of the anisotropic conductive film of the present invention includes a state in which the conductive particles 1 are randomly dispersed and a state in which the conductive particles 1 are dispersed in a regular arrangement. In either case, it is preferable that the positions in the film thickness direction are aligned from the viewpoint of capture stability. Here, that the position of the conductive particles 1 in the film thickness direction is uniform is not limited to that the conductive particles 1 are aligned at a single depth in the film thickness direction, but the front and back interfaces of the insulating resin layer 2 or the vicinity thereof. In which conductive particles are present.

導電 In addition, it is preferable that the conductive particles 1 are regularly arranged in a plan view of the film from the viewpoint of suppressing a short circuit. The arrangement mode depends on the layout of terminals and bumps, and is not particularly limited. For example, the film can be arranged in a square lattice arrangement as shown in FIG. 1A in plan view. In addition, as an aspect of the regular arrangement of the conductive particles, a lattice arrangement such as a rectangular lattice, an oblique lattice, a hexagonal lattice, and a triangular lattice can be given. A plurality of lattices having different shapes may be combined. Further, a particle row in which conductive particles are linearly arranged at predetermined intervals may be arranged in parallel at predetermined intervals. When the conductive particles 1 are not in contact with each other and are arranged in a regular array such as a lattice, pressure can be uniformly applied to each conductive particle 1 at the time of anisotropic conductive connection, and variation in conduction resistance can be reduced.

ことが Further, it is more preferable that the conductive particles are regularly arranged in a plan view of the film and the positions in the film thickness direction are uniform in order to achieve both capture stability and short-circuit suppression.

On the other hand, when the space between the terminals of the electronic components to be connected is large and a short circuit is unlikely to occur, the conductive particles may be randomly dispersed without being regularly arranged. Even in the case of dispersing, it is preferable that the individual conductive particles are arranged in a non-contact manner (the individual conductive particles are independently present in a non-contact manner) in a plan view of the film. Although this is an example because it depends on the terminal layout, the number ratio may be 75% or more, preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

When the conductive particles are regularly arranged, the lattice axis or the arrangement axis of the arrangement may be parallel to the longitudinal direction of the anisotropic conductive film or a direction perpendicular to the longitudinal direction, and the longitudinal axis of the anisotropic conductive film. It may intersect with the direction, and can be determined according to the terminal width, terminal pitch and the like to be connected. For example, in the case of an anisotropic conductive film for fine pitch, as shown in FIG. 1A, the lattice axis A of the arrangement of the conductive particles 1 is inclined with respect to the longitudinal direction of the anisotropic conductive film 10A. It is preferable that the angle θ between the longitudinal direction (the short direction of the film) of the terminal 200 connected with the anisotropic conductive film 10A and the lattice axis A is 6 ° or more and 84 ° or less, preferably 11 ° or more and 74 ° or less. .

距離 The distance between the conductive particles 1 is appropriately determined according to the size and the terminal pitch of the terminals connected by the anisotropic conductive film. Generally, from the viewpoint of preventing occurrence of short-circuit, the lower limit of the distance between the nearest particles (that is, the distance between the closest particles) is preferably 50% or more of the average particle diameter D of the conductive particles or 0.2 μm or more. The upper limit is not particularly limited as long as the condition of the number density can be satisfied. For example, the average particle diameter D of the conductive particles is preferably 30 μm or less, which is a preferable maximum diameter, or the average particle diameter is relatively small. When the diameter D is small, it is preferably 10 times or less the average particle diameter D.

The area occupancy of the conductive particles of the anisotropic conductive film of the present invention in a plan view is an index of the thrust required for the pressing jig for thermocompression bonding the anisotropic conductive film to the electronic component. If the area occupancy is too large, the thrust increases accordingly, and if the substrate is easily deformed such as plastic, it becomes a factor of deformation. Therefore, the upper limit of the area occupancy of the conductive particles is preferably 30% or less, more preferably 26% or less, and even more preferably 23% or less. Further, if the area occupancy is too small, there is a possibility that the device cannot cope with the fine pitch, so that it is preferably 3% or more, more preferably 6% or more, and still more preferably 9% or more. Here, the area occupancy [%] of the conductive particles can be calculated by the following equation.

Here, as described in the paragraph 0052, the measurement region of the number density and the area occupancy of the conductive particles may be a rectangular region having a side of 100 μm or more at a plurality of positions (preferably 5 or more, more preferably 10 or more), and the total area of the measurement regions is preferably 2 mm ² or more. The size and number of the individual regions may be appropriately adjusted depending on the state of the number density.

<Position of conductive particles in the thickness direction of insulating resin layer>
In the anisotropic conductive film of the present invention, the position of the conductive particles 1 in the thickness direction of the insulating resin layer 2 may be such that the conductive particles 1 are exposed from the insulating resin layer 2 as described above. Without being buried in the insulating resin layer 2, the surface 2 a of the insulating resin layer on which the recesses 2 b and 2 c are formed may be buried from the tangent plane 2 p at the center between adjacent conductive particles. The distance Lb at the deepest part of the conductive particles (hereinafter referred to as an embedding amount), and the ratio of the embedding amount Lb to the particle diameter D of the conductive particles 1 [(Lb / D) × 100] (hereinafter referred to as an embedding rate) Is preferably 60% or more and 105% or less.

By setting the embedding rate to 60% or more, the conductive particles 1 are maintained in a predetermined particle dispersion state or a predetermined arrangement by the insulating resin layer 2, and by setting the embedding rate to 105% or less, the anisotropic conductive connection is achieved. In some cases, the amount of resin in the insulating resin layer that acts to flow the conductive particles between the terminals unnecessarily can be reduced.

In the present invention, the numerical value of the embedding rate, the numerical value of the embedding rate (Lb / D) is 80% or more, preferably 90% or more, more preferably 90% or more of the total number of conductive particles contained in the anisotropic conductive film. Means that 96% or more is the numerical value of the embedding rate (Lb / D). Therefore, an embedding rate of 60% or more and 105% or less means that the embedding rate of 80% or more, preferably 90% or more, more preferably 96% or more of the total number of conductive particles contained in the anisotropic conductive film is 60%. % Or more and 105% or less. Since the embedding ratio (Lb / D) of all the conductive particles is uniform, the pressing force is uniformly applied to the conductive particles, so that the conductive particles are captured well by the terminals, and the stability of conduction is improved. Is improved.

The embedding rate is obtained by arbitrarily extracting 10 or more areas having an area of 30 mm ² or more from the anisotropic conductive film, observing a part of the cross section of the film with an SEM image, and measuring a total of 50 or more conductive particles. You can ask. In order to further increase the accuracy, it may be obtained by measuring 200 or more conductive particles.

Further, the embedding rate can be collectively obtained for a certain number by adjusting the focus in the surface visual field image. Alternatively, a laser type discriminating displacement sensor (manufactured by Keyence Corporation) may be used for measuring the embedding rate.

<Modification of anisotropic conductive film>
(Second insulating resin layer)
The anisotropic conductive film of the present invention is, like the anisotropic conductive film 10E shown in FIG. 5, a surface of the conductive particle dispersion layer 3 on which the conductive particles 1 are held (in other words, an insulating resin). A second insulating resin layer 4 (functioning as an insulating adhesive layer) having a lower minimum melt viscosity than that of the insulating resin layer 2 may be laminated on the surface of the layer 2 where the recess 2c is formed. Also, like the anisotropic conductive film 10F shown in FIG. 6, the surface of the conductive particle dispersion layer 3 on the side where the conductive particles 1 are not held (in other words, the recess 2c of the insulating resin layer 2 is formed). A second insulating resin layer 4 (functioning as an insulating adhesive layer) having a lower minimum melt viscosity than the insulating resin layer 2 may be laminated on the non-conductive surface). By laminating the second insulating resin layer 4, when an electronic component is anisotropically conductively connected using an anisotropic conductive film, the space formed by the electrodes and bumps of the electronic component is filled to improve the adhesiveness. Can be improved. When the second insulating resin layer 4 is laminated, the second insulating resin layer 4 is added with a tool regardless of whether the second insulating resin layer 4 is on the surface on which the recess 2c is formed. It is preferably on the side of an electronic component such as an IC chip to be pressed (in other words, the insulating resin layer 2 is on the side of an electronic component such as a substrate mounted on a stage). By doing so, unintentional movement of the conductive particles can be avoided, and trapping properties can be improved.

As the difference between the minimum melt viscosities of the insulating resin layer 2 and the second insulating resin layer 4 increases, the space formed by the electrodes and bumps of the electronic component is more easily filled with the second insulating resin layer 4. The effect of improving the adhesion between electronic components can be expected. In addition, the larger the difference, the relatively small the amount of movement of the insulating resin layer 2 existing in the conductive particle dispersion layer 3, so that the ability of the terminal to capture the conductive particles can be easily improved. In practice, the lowest melt viscosity ratio between the insulating resin layer 2 and the second insulating resin layer 4 (that is, [minimum melt viscosity of the insulating resin layer 2] / [minimum melt viscosity of the second insulating resin layer 4] Melt viscosity]) is preferably 2 or more, more preferably 5 or more, and further preferably 8 or more. On the other hand, if the ratio is too large, when a long anisotropic conductive film is formed into a wound body, there is a possibility that the resin will protrude or block, so that the ratio is preferably 15 or less in practical use. The preferred minimum melt viscosity of the second insulating resin layer 4 can be determined with reference to the description of Japanese Patent No. 6187665 (paragraph 0091).

The second insulating resin layer 4 can be formed by adjusting the viscosity of the same resin composition as the insulating resin layer.

In the anisotropic conductive films 10E and 10F, the layer thickness of the second insulating resin layer 4 is preferably 4 μm or more and 20 μm or less. Alternatively, it is preferably 1 to 8 times the conductive particle diameter.

最低 Further, the minimum melt viscosity of the entire anisotropic conductive films 10E and 10F including the insulating resin layer 2 and the second insulating resin layer 4 is preferably 200 Pa · s or more and 4000 Pa · s or less. Note that the minimum melt viscosity of the second insulating resin layer 4 itself is preferably 2000 Pa · s or less, more preferably 100 to 2000 Pa · s, on the assumption that the above-described minimum melt viscosity ratio is satisfied.

(Third insulating resin layer)
A third insulating resin layer may be provided on the opposite side of the second insulating resin layer 4 and the insulating resin layer 2 with the insulating resin layer 2 interposed therebetween. For example, the third insulating resin layer or the insulating adhesive layer can function as a tack layer. Like the second insulating resin layer, it may be provided to fill the space formed by the electrodes and bumps of the electronic component.

樹脂 The resin composition, viscosity and thickness of the third insulating resin layer may be the same as or different from those of the second insulating resin layer. The minimum melt viscosity of the anisotropic conductive film including the insulating resin layer 2, the second insulating resin layer 4, and the third insulating resin layer is not particularly limited, but may be 200 to 4000 Pa · s. it can.

<Method for producing anisotropic conductive film>
The anisotropic conductive film of the present invention can be manufactured by a manufacturing method including a step of forming a conductive particle dispersed layer by injecting conductive particles into an insulating resin layer. In a preferred embodiment of this step, the conductive particles are held in a predetermined arrangement on the surface of the insulating resin layer, and the conductive particles are pressed into the insulating resin layer with a flat plate or a roller to form a conductive particle dispersion layer. A mode in which conductive particles are filled in a transfer mold, and the conductive particles are transferred to the insulating resin layer to hold the conductive particles in a predetermined arrangement on the surface of the insulating resin layer. In addition, a mode in which the conductive particles 1 are directly sprayed and held on the insulating resin layer 2 or a single layer of the conductive particles 1 is attached to a film that can be biaxially stretched, and the film is biaxially stretched, There is also an embodiment in which the insulating resin layer 2 is pressed against the stretched film to transfer the conductive particles to the insulating resin layer 2, thereby holding the conductive particles 1 on the insulating resin layer 2.

In the case of an embodiment in which the conductive particles are formed by pushing the conductive particles into the insulating resin layer, the lowest melt viscosity of the insulating resin layer may be determined with reference to the description of Japanese Patent No. 6187665 (paragraph 0097). it can. Thereby, the conductive particles can be pushed so that the surface of the insulating resin layer forming the surface of the conductive particle dispersion layer has a recess with respect to the tangent plane of the insulating resin layer at the center between adjacent conductive particles. .

When an anisotropic conductive film having an embedding ratio of more than 100% is manufactured, the anisotropic conductive film may be pressed with a pressing plate so as to have a convex portion corresponding to the conductive particle arrangement.

When the conductive particles 1 are held in the insulating resin layer 2 using a transfer mold, examples of the transfer mold include inorganic materials such as silicon, various ceramics, glass, metals such as stainless steel, and various resins. For the organic material described above, a material in which an opening is formed by a known method for forming an opening such as a photolithographic method or a material to which a printing method is applied can be used. Further, the transfer mold can take a shape such as a plate shape or a roll shape. Note that the present invention is not limited to the above method.

In addition, a second insulating resin layer having a lower viscosity than the insulating resin layer can be laminated on the surface of the insulating resin layer into which the conductive particles have been pressed, on the surface on which the conductive particles have been pressed, or on the opposite surface. .

には In order to economically connect electronic components using an anisotropic conductive film, it is preferable that the anisotropic conductive film has a certain length. Therefore, it is preferable that the length of the anisotropic conductive film is specifically 5 m or more. It can also be determined with reference to the description of Japanese Patent No. 6187665 (paragraph 0103). When an anisotropic conductive film is practically used, it is practical to wind the film around a reel to form a wound body. However, in the case of such a wound body, if the resin viscosity (that is, substantially proportional to the minimum melt viscosity of the film) is too low, problems such as protruding and blocking may occur in continuous connection. There is. Therefore, the minimum melt viscosity of the anisotropic conductive film is preferably set to 200 Pa · s or more. This is the same even if the second insulating resin layer and the third insulating resin layer are laminated.

<How to use anisotropic conductive film>
In the anisotropic conductive film of the present invention, in particular, the first electronic component (the side heated by the tool) has relatively high rigidity such as an IC chip or an IC module (for example, from a wafer similar to a general IC chip). This is particularly applicable when the second electronic component (the side to be mounted on the stage) is a flexible material such as a plastic substrate. It should be noted that a first electronic component such as a semiconductor element, an IC chip, an IC module, or an FPC is connected to a second electronic component such as an FPC, a glass substrate, a plastic substrate, a rigid substrate, or a ceramic substrate for anisotropic conductive connection. It does not exclude aspects. Further, IC chips or wafers may be stacked to form a multilayer using the anisotropic conductive film of the present invention. The electronic components connected by the anisotropic conductive film of the present invention are not necessarily limited to the above electronic components. In recent years, it can be used for various diversified electronic components. For example, when an IC chip or an FPC is used as the first electronic component, an OLED plastic substrate can be used as the second electronic component. In particular, when the first electronic component is an IC chip and the second electronic component is a COP structure using a plastic substrate, the present invention particularly exerts its effect. Therefore, the present invention provides a “connection structure in which the first electronic component and the second electronic component are anisotropically conductively connected via the anisotropic conductive film of the present invention”; And a second electronic component through an anisotropic conductive film of the present invention for anisotropically conductive connection.

As a method for connecting an electronic component using an anisotropic conductive film, when the anisotropic conductive film is formed of a single layer of the conductive particle dispersion layer 3, the anisotropic conductive film is used for the second electronic component such as various substrates. The first electronic component such as an IC chip is provided on the side of the temporarily-bonded anisotropic conductive film where the conductive particles 1 are not embedded in the surface, in which the conductive particles 1 are temporarily embedded and temporarily compressed from the side where the conductive particles 1 are embedded in the surface. And thermocompression bonding. When the insulating resin layer of the anisotropic conductive film contains not only the thermal polymerization initiator and the thermopolymerizable compound but also the photopolymerization initiator and the photopolymerizable compound (which may be the same as the thermopolymerizable compound), A pressure bonding method using both light and heat may be used. In this way, unintentional movement of the conductive particles can be minimized. Alternatively, the side where the conductive particles are not embedded may be temporarily attached to the second electronic component for use. Note that the anisotropic conductive film may be temporarily attached to the first electronic component instead of the second electronic component, and then aligned and connected.

When the anisotropic conductive film is formed of a laminate of the conductive particle dispersion layer 3 and the second insulating resin layer 4 (functioning as an insulating adhesive layer), the conductive particle dispersion layer 3 may be formed of various substrates. The first electronic component such as an IC chip is aligned and placed on the side of the second insulating resin layer 4 of the anisotropically conductive film that has been temporarily bonded and temporarily bonded to the second electronic component. Crimp. The second insulating resin layer 4 side of the anisotropic conductive film may be temporarily attached to the first electronic component. Further, the conductive particle dispersion layer 3 side can be temporarily attached to the first electronic component for use.

Hereinafter, the present invention will be described specifically with reference to examples.
Examples 1 to 8, Comparative Example 1, Reference Example 1
(1) Preparation of Resin Composition for Forming Insulating Resin Layer and Insulating Adhesive Layer Insulating resin layer, second insulating resin layer and insulative adhesive layer are formed with the composition shown in Table 1. Each resin composition was prepared. The minimum melt viscosity of the obtained composition was kept constant at a measurement pressure of 5 g using a rotary rheometer (manufactured by TA Instruments) at a temperature of 30 to 200 ° C. using a measurement plate having a diameter of 8 mm. The temperature rate was 10 ° C./min, the measurement frequency was 10 Hz, and the load variation on the measurement plate was 5 g. Table 1 shows the obtained results. In addition, Formula B, Formula C and Formula D are the resin compositions for the present invention. Formulations A and E are resin compositions for comparative examples.

(2) Preparation of Conductive Particles Metal-coated resin particles (Au / Ni plating, average particle diameter 3 μm) manufactured by Sekisui Chemical Co., Ltd. were prepared as the conductive particles 1 to 4 in Table 2. Here, the 20% compression elastic modulus and the compression recovery rate were measured using a micro compression tester (Fisher Scope H-100, manufactured by Fisher Co., Ltd.) as described below.

<20% compression modulus>
Compression variation of conductive particles when the conductive particles are compressed under the conditions of a compression speed of 2.6 mN / sec and a maximum test load of 10 gf using a micro-compression tester on the end face of a cylindrical (diameter: 50 μm, diamond) smooth indenter. Was calculated and the numerical value obtained by the measurement was applied to the following equation (1).

<Compression restoration ratio>
Using a micro-compression tester, the conductive particles are compressed at the end face of a smooth indenter of a cylinder (diameter: 50 μm, made of diamond), and the displacement (L2) from the initial load (load 0.4 mN) to the load reversal (load 5 mN). The displacement (L1) from the load reversal to the final load (load 0.4 mN) was measured, and the numerical value obtained by the measurement was calculated by applying it to the following equation (2).

The

conductive particles

1, 3 and 4 are conductive particles for the present invention, and the conductive particles 2 are conductive particles for a comparative example.

(3) Formation of insulating resin layer, second insulating resin layer and insulating adhesive layer A resin composition for forming the insulating resin layer, the second insulating resin layer or the insulating adhesive layer (Table 1) Was coated on a PET film having a film thickness of 50 μm using a bar coater and dried in an oven at 80 ° C. for 5 minutes to form an insulating resin layer having a thickness shown in Table 3 on the PET film. Similarly, a second insulating resin layer or an insulating adhesive layer was formed on different PET films at the thicknesses shown in Table 3.

(4) Production of Resin Transfer Master The conductive particles 1 have a square lattice arrangement shown in FIG. 1A in plan view, the distance between the particles is equal to the average particle diameter of the conductive particles, and the number density of the conductive particles is as shown in Table 3. A mold was manufactured so as to be as follows. That is, the pattern of the convex portions of the mold is a square lattice array, the pitch of the convex portions on the lattice axis is twice the average conductive particle diameter, and the angle θ between the lattice axis and the lateral direction of the anisotropic conductive film is A mold of 15 ° is produced, and a known transparent resin pellet is melted and poured into the mold, and cooled and solidified to form a resin transfer master having an arrangement pattern as shown in FIG. 1A. did.

(5) Preparation of anisotropic conductive film The conductive particles shown in Table 2 are filled in the resin mold having the number of dents corresponding to the number density of the conductive particles shown in Table 3, and the above-described insulating material is placed thereon. The conductive resin layer was covered, and was adhered by pressing at 60 ° C. and 0.5 MPa. Then, the insulating resin layer is peeled from the mold, and the conductive particles on the insulating resin layer are pressed into the insulating resin layer by applying pressure (pressing conditions: 60 to 70 ° C., 0.5 MPa) to disperse the conductive particles. An anisotropic conductive film composed of a single layer was prepared (Examples 1 to 5, Comparative Example 1 and Reference Example 1). The state of embedding of the conductive particles was controlled by pressing conditions (mainly pressure conditions and temperature conditions).

{Circle around (2)} A two-layer type anisotropic conductive film was prepared by laminating a second insulating resin layer on the conductive particle dispersion layer similarly prepared (Examples 6 and 7). Furthermore, a three-layer type anisotropic conductive film was prepared by laminating an insulating adhesive layer having tackiness on the conductive particle dispersion layer side of the two-layer type anisotropic conductive film similarly prepared (executed). Example 8).

(6) Evaluation With respect to the anisotropic conductive films of the examples and comparative examples produced in (5), (a) initial conduction resistance, (b) conduction reliability, (c) indentation, and (d) ) Particle capture properties were measured or evaluated. Table 3 shows the results.

(A) Initial conduction resistance Each of the anisotropic conductive films of Examples and Comparative Examples was sandwiched between an IC for evaluating conduction characteristics and a plastic substrate, and heated and pressurized (180 ° C., 60 MPa, 5 seconds). The connection for evaluation was obtained, and the conduction resistance of the connection for evaluation was measured. The initial conduction resistance is preferably 2Ω or less for practical use.

端子 Here, the terminal patterns of the evaluation IC and the plastic substrate correspond to each other, and the sizes are as follows. When connecting the evaluation IC to the plastic substrate, the longitudinal direction of the anisotropic conductive film was aligned with the lateral direction of the bump.

IC for evaluating conduction characteristics
1.8 x 20.0mm
Thickness 0.5mm
Bump specifications Size 30 × 85 μm, distance between bumps 50 μm, bump height 15 μm

Plastic substrate (ITO wiring)
Substrate material Polyethylene terephthalate base film / Polyurethane adhesive / Polyimide film (PET / PU / PI substrate)
Outline 30 × 50mm
Thickness 0.5mm
Electrode ITO wiring

(B) Conduction reliability The conduction resistance after placing the connection for evaluation prepared in (a) in a thermostat at a temperature of 85 ° C. and a humidity of 85% RH for 500 hours was measured in the same manner as the initial conduction resistance. The conduction reliability is practically preferably 5Ω or less, more preferably 2Ω or less.

(C) Indentation The connection object for evaluation prepared in (a) was observed with a metallographic microscope from the plastic substrate side, and it was confirmed whether or not an indentation was observed at the center of the bump end. The case where it was observed was evaluated as good (good), and the case where it was not observed was evaluated as poor (poor).

(D) Particle trapping property Using the particle trapping property evaluation IC, this evaluation IC and the plastic (PET / PU / PI) substrate (ITO wiring) corresponding to the terminal pattern are heated by shifting the alignment by 6 μm. Pressurization (180 ° C, 60 MPa, 5 seconds), measure the number of captured conductive particles in 100 areas of 6 μm × 66.6 μm where the bump of the evaluation IC and the terminal of the substrate overlap, and find the minimum number of captured. Was evaluated according to the following criteria. In practice, it is preferable that the evaluation is B or more.

Evaluation IC for particle capture
1.6 x 29.8mm
0.3mm thickness
Bump specifications Size 12 × 66.6 μm, bump pitch 22 μm (L / S = 12 μm / 10 μm), bump height 12 μm

Evaluation standard of particle trapping property A 5 or more B 3 or more and less than 5 C 3 or less

(Discussion)
From the results in Table 3, the following conditions (a) to (e) were obtained:
<Conditions (a)>
20% compressive elasticity modulus of the conductive particles, 6000 N / mm ² or more 15000 N / mm ² that less is;
<Conditions (b)>
The compression recovery ratio of the conductive particles is 40% or more and 80% or less;
<Condition (C)>
The average particle diameter of the conductive particles is 1 μm or more and 30 μm or less;
<Condition (d)>
The minimum melt viscosity of the insulating resin layer is 4000 Pa · s or less; and <Condition (e)>
The anisotropic conductive films of Examples 1 to 8 satisfying that the number density of the conductive particles is not less than 6000 / mm ^{2 and not} more than 36000 / mm ² , (a) initial conduction resistance, and (b) conduction reliability. Each of the properties (c) indentation and (d) particle trapping properties showed favorable results that were at or above a level at which there was no practical problem.

On the other hand, the anisotropic conductive film of Comparative Example 1, which exceeded the numerical range of the condition (d), had a problem in “continuity reliability”. There was also a problem with "indentation". Note that the anisotropic conductive film of Reference Example 1, in which the numerical ranges of the conditions (A) and (B) are slightly deviated downward, has an initial conduction resistance and an initial conduction resistance which are lower than those of Examples 1 to 8. Although the resistance value in the conduction reliability is slightly high, it is not at a level that causes a problem in practical use. However, taking into account variations in connection conditions during manufacturing, it is preferable that the initial conduction resistance and the resistance value in conduction reliability are low as in Examples 1 to 8.

In the anisotropic conductive film of the present invention, as the conductive particles held in the conductive particle dispersion layer, those having 20% compression elastic modulus, compression recovery rate and average particle diameter each in a specific numerical range are used, As the insulating resin layer holding such conductive particles, a resin having a minimum melt viscosity of a specific value or less is used, and the degree of holding the conductive particles in such insulating resin layer (in other words, the number density ) Is set within a specific range. Therefore, via the anisotropic conductive film of the present invention, an electronic component having a bump such as an image display element or a driving IC chip is anisotropically mounted on a flexible plastic substrate on which electrodes and wiring are formed. In the case of conducting conductive connection, it is possible to prevent cracks from being generated in the wiring of the plastic substrate, and it is possible to generate indentations showing good anisotropic conductive connection. In addition, a good conduction reliability evaluation can be obtained. Therefore, the anisotropic conductive film of the present invention is useful for connecting an electronic component (especially an IC chip) to an anisotropic conductive connection not only to a glass substrate but also to a plastic substrate.

REFERENCE SIGNS LIST 1 conductive particle 1a conductive particle top 2 insulating resin layer 2a surface of insulating resin layer 2b recess 2c recess 2p tangential plane 3 conductive particle dispersion layer 4 second insulating

resin layer

10A, 10B, 10C, 10D, 10E, 10F Anisotropic conductive film 200 of Example Terminal A Lattice axis of array of conductive particles D Average particle size of conductive particles La Layer thickness of insulating resin layer Lb Embedding amount (from tangent plane at center between adjacent conductive particles Distance of the deepest part of the conductive particles)
Lc Exposed diameter θ Angle between the longitudinal direction of the terminal and the lattice axis of the array of conductive particles

Claims

An anisotropic conductive film having a conductive particle-dispersed layer composed of at least an insulating resin layer and conductive particles dispersed therein, and having the following conditions (a) to (e):
<Conditions (a)>
20% compressive elasticity modulus of the conductive particles, 6000 N / mm 2 or more 15000 N / mm 2 that less is;
<Conditions (b)>
The compression recovery ratio of the conductive particles is 40% or more and 80% or less;
<Condition (C)>
The average particle diameter of the conductive particles is 1 μm or more and 30 μm or less;
<Condition (d)>
The minimum melt viscosity of the insulating resin layer is 4000 Pa · s or less; and <Condition (e)>
An anisotropic conductive film that satisfies that the number density of the conductive particles is 6000 / mm 2 or more and 36000 / mm 2 or less.
The anisotropic conductive film according to claim 1, wherein the minimum melt viscosity of the insulating resin layer is 200 Pa · s or more.
The anisotropic conductive film according to claim 1 or 2, wherein the conductive particles are arranged in non-contact with the insulating resin layer.
4. The anisotropic conductive film according to claim 3, wherein the conductive particles are regularly arranged in a plan view.
(5) The anisotropic conductive film according to any one of (1) to (4), wherein the distance between the closest particles of the conductive particles is 50% or more of the average particle diameter of the conductive particles or 0.2 μm or more, whichever is longer.
(6) The anisotropic conductive film according to any one of (1) to (5), wherein the second insulating resin layer is laminated on the surface of the conductive particle dispersion layer on the side where the conductive particles are held.
(6) The anisotropic conductive film according to any one of (1) to (5), wherein the second insulating resin layer is laminated on the surface of the conductive particle dispersion layer on the side where the conductive particles are not held.
8. The anisotropic conductive film according to claim 6, wherein the minimum melt viscosity of the second insulating resin layer is lower than the minimum melt viscosity of the insulating resin layer.
The anisotropic conductive film according to any one of claims 6 to 8, wherein the minimum melt viscosity ratio between the insulating resin layer and the second insulating resin layer is 2 or more.
(4) The method for producing an anisotropic conductive film according to (1), further comprising a step of forming a conductive particle dispersed layer by pushing conductive particles into an insulating resin layer.
11. The method according to claim 10, wherein the conductive particles are held in a predetermined arrangement on the surface of the insulating resin layer, and the conductive particles are pressed into the insulating resin layer with a flat plate or a roller to form a conductive particle dispersion layer.
12. The manufacturing method according to claim 11, wherein the transfer mold is filled with conductive particles, and the conductive particles are transferred to the insulating resin layer so that the conductive particles are held in a predetermined arrangement on the surface of the insulating resin layer.
A connection structure in which the first electronic component and the second electronic component are anisotropically conductively connected via the anisotropic conductive film according to any one of claims 1 to 9.
14. The connection structure according to claim 13, wherein the first electronic component is an IC chip or an IC module, and the second electronic component is a plastic substrate.
A method of manufacturing a connection structure, wherein the first electronic component and the second electronic component are anisotropically conductively connected via the anisotropic conductive film according to any one of claims 1 to 9.