CN112740483B

CN112740483B - Anisotropic conductive film, connection structure, and method for producing connection structure

Info

Publication number: CN112740483B
Application number: CN201980061791.XA
Authority: CN
Inventors: 久保出裕美; 塚尾怜司
Original assignee: Dexerials Corp
Current assignee: Dexerials Corp
Priority date: 2018-10-03
Filing date: 2019-09-27
Publication date: 2023-07-14
Anticipated expiration: 2039-09-27
Also published as: TW202028001A; JP2020095941A; CN112740483A; KR20210033513A

Abstract

An anisotropic conductive film suitable for anisotropic conductive connection with an electronic component having bumps, such as an image display device or a driving IC chip, and a flexible plastic substrate having transparent electrodes and wirings formed thereon, has at least a conductive particle dispersion layer composed of an insulating resin layer and conductive particles dispersed therein. The anisotropic conductive film satisfies: condition (1): the conductive particles had a 20% compression elastic modulus of 6000N/mm ² Above and 15000N/mm ² The following are set forth; condition (2): the compression recovery rate of the conductive particles is 40% or more and 80% or less; condition (3): the average particle diameter of the conductive particles is 1 μm or more and 30 μm or less, condition (4): the insulating resin layer has a minimum melt viscosity of 4000 Pa.s or less; and condition (5): the number density of the conductive particles is 6000 pieces/mm ² Above and 36000/mm ² The following is given.

Description

Anisotropic conductive film, connection structure, and method for producing connection structure

Technical Field

The present invention relates to an anisotropic conductive film.

Background

For the light weight and curved surface of an image display panel, a flexible plastic substrate is used as a substrate for mounting electronic components such as an image display element and a driving IC chip. As a representative example of such a plastic substrate, from the viewpoint of preventing thermal deformation and reflection, there is a plastic substrate 24 having a structure in which a polyethylene terephthalate film 20 and a polyimide film 22 having a transparent electrode 21 formed thereon are laminated with a polyurethane-based adhesive layer 23 as shown in fig. 7 (patent document 1).

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2016-54288.

Disclosure of Invention

Problems to be solved by the invention

Incidentally, it is widely performed that bumps of an IC chip are anisotropically conductively connected to electrodes of a flexible plastic substrate as shown in fig. 7 by an anisotropic conductive film in which conductive particles are dispersed in an insulating resin binder. In this case, a large number of bumps are provided at a fine pitch on the IC chip, and an oxide film is formed on the electrode surface of the plastic substrate. Therefore, in order to reliably connect the bump and the electrode after the bump of the IC chip breaks through the oxide film on the electrode surface of the plastic substrate, the IC chip is pressed into the plastic substrate by a large press.

Therefore, since the rigidity of the IC chip is much higher than that of the plastic substrate, deformation of the plastic substrate side is increased by the pressing at the time of connection, and there is a concern that "disconnection of the wiring on the plastic substrate side" or "insufficient pressing of particles" may occur. Specifically, as shown in fig. 8, when heating and pressurizing are performed to anisotropically electrically connect the bump B of the IC chip and the electrode 21 of the plastic substrate 24 by the anisotropic conductive film ACF, there is a possibility that the adhesive layer 23 of the plastic substrate 24 is excluded from the periphery of the bump B of the IC chip, and a phenomenon (doming) of forming an inverted dome-shaped thin portion 25 is generated. If such a doming phenomenon occurs, a crack may occur in the vicinity of the shoulder 26 on the wiring 21a extending from the electrode 21. In order to evaluate the conduction reliability of anisotropic conductive connection, although the evaluation was performed by observing the indentations formed by the conductive particles sandwiched between the electrode 21 and the bump B from the polyethylene terephthalate film 20 side, there was a concern that the conductive particles 27a sandwiched between the bump B and the electrode 21 in the vicinity of the edge E of the pressing surface of the bump could observe the indentations showing good connection, whereas the conductive particles 27B sandwiched between the bump B and the electrode in the vicinity of the center C of the pressing surface of the bump B could hardly observe the indentations showing good connection (i.e., the sandwiched state of the conductive particles). If such an indentation is not observed, there is a problem that the evaluation of the conduction characteristics (initial conduction, conduction reliability, etc.) has to be lowered even if there is a good conduction.

In order to eliminate such a concern, for example, studies are being made from the viewpoints of (a) adjusting the anisotropic conductive connection conditions, (b) adjusting the structure or characteristics of the plastic substrate, (c) adjusting the structure or characteristics of the IC chip, and (d) adjusting the structure or characteristics of the anisotropic conductive film. However, in the case of conducting a study from the point of view of (a), it is necessary to modify or newly introduce the manufacturing equipment, and in the case of conducting a study from the points of view of (b) and (c), it is necessary to change the specifications of the electronic parts as the anisotropic conductive connection targets. Therefore, it is demanded to study from the point of view of (d) without modifying or newly setting the manufacturing equipment and changing the specifications of the electronic parts as the anisotropic conductive connection targets.

The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide an anisotropic conductive film which is particularly suitable for anisotropically connecting an electronic component having bumps, such as an image display device or a driving IC chip, to a flexible plastic substrate or the like on which electrodes (for example, metal electrodes such as Ti, ti/AL, or the like, metal oxide electrodes such as ITO, or metal oxide electrodes obtained by oxidizing the surfaces of the metal electrodes) are formed, wherein cracks are not generated in wiring lines of the plastic substrate during anisotropically conductive connection, and an indentation exhibiting excellent anisotropically conductive connection is formed, thereby realizing high conduction reliability.

Means for solving the problems

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

Specifically, the present invention provides an anisotropic conductive film having at least a conductive particle dispersion layer composed of an insulating resin layer and conductive particles dispersed therein, which satisfies the following conditions (1) to (5):

< condition (1) >

The conductive particles had a 20% compression elastic modulus of 6000N/mm ² Above and 15000N/mm ² The following are set forth;

< condition (2) >

The compression recovery rate of the conductive particles is 40% or more and 80% or less;

< condition (3) >

The conductive particles have an average particle diameter of 1 μm or more and 30 μm or less;

< condition (4) >

The insulating resin layer has a minimum melt viscosity of 4000 Pa.s or less; and

< condition (5) >

The number density of the conductive particles is 6000 pieces/mm ² Above and 36000/mm ² The following is given.

The present invention also provides a method for producing the anisotropic conductive film of the present invention, which comprises a step of forming a conductive particle dispersion layer by pressing conductive particles into an insulating resin layer. As a preferable mode of this step, the following modes are listed: a method in which conductive particles are held on the surface of an insulating resin layer in a predetermined arrangement, and the conductive particles are pressed into the insulating resin layer by a plate or a roller, thereby forming a conductive particle dispersion layer; or by filling the conductive particles in a transfer mold and transferring the conductive particles onto the insulating resin layer, the conductive particles are held on the surface of the insulating resin layer in a predetermined arrangement.

The present invention also provides a connection structure in which the 1 st electronic component (for example, an IC chip or an IC module) and the 2 nd electronic component (for example, a flexible plastic substrate) are anisotropically electrically connected by the anisotropic conductive film of the present invention.

ADVANTAGEOUS EFFECTS OF INVENTION

The anisotropic conductive film of the present invention has a conductive particle dispersion layer composed of at least 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, conductive particles having a 20% compression elastic modulus, a compression recovery rate, and an average particle diameter respectively in a specific numerical range are used, as the insulating resin layer for holding such conductive particles, an insulating resin layer having a minimum melt viscosity of a specific numerical value or less is used, and the degree (in other words, the number density) of holding the conductive particles in such insulating resin layer is set in a specific range. Therefore, in the case where an electronic component having bumps such as an image display element or a driving IC chip is anisotropically electrically connected to a flexible plastic substrate on which electrodes and wirings are formed by the anisotropic conductive film of the present invention, cracks can be prevented from occurring in the wirings of the plastic substrate. In addition, an indentation exhibiting good anisotropic conductive connection can be generated, and good conduction reliability evaluation can be obtained at the time of anisotropic conductive connection.

Drawings

Fig. 1A is a plan view showing the arrangement of conductive particles in an anisotropic conductive film 10A according to an embodiment.

Fig. 1B is a sectional view of an anisotropic conductive film 10A of the embodiment.

Fig. 2 is a cross-sectional view of an anisotropic conductive film 10B of the embodiment.

Fig. 3 is a cross-sectional view of an anisotropic conductive film 10C of the embodiment.

Fig. 4 is a cross-sectional view of an anisotropic conductive film 10D of the embodiment.

Fig. 5 is a cross-sectional view of an anisotropic conductive film 10E of the embodiment.

Fig. 6 is a cross-sectional view of an anisotropic conductive film 10F of the embodiment.

Fig. 7 is a schematic cross-sectional view of a plastic substrate.

Fig. 8 is a schematic view of the case where an IC chip is anisotropically electrically connected to a plastic substrate.

Detailed Description

The anisotropic conductive film of the present invention has a conductive particle dispersion layer composed of at least an insulating resin layer and conductive particles dispersed therein. As the conductive particles held in the conductive particle dispersion layer, the condition (1) is used: "20% compression elastic modulus", condition (2): "compression recovery rate" and condition (3): the conductive particles having "average particle diameters" in a specific numerical range are used as the insulating resin layer for holding such conductive particles under the condition (4): the "minimum melt viscosity" is an insulating resin layer in a specific range, and as the degree of holding conductive particles in such an insulating resin layer, condition (5) is set: the "number density" is set within a specific range. Hereinafter, an example of the anisotropic conductive film of the present invention will be described in detail with reference to the accompanying drawings. In the following drawings, the same reference numerals denote the same or equivalent components.

< integral Structure of Anisotropic conductive film >

Fig. 1A is a plan view illustrating a particle configuration of an anisotropic conductive film 10A according to an embodiment of the present invention, and fig. 1B is an X-X sectional view thereof. In addition, fig. 2, 3 to 4 are sectional views of anisotropic

conductive films

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

The anisotropic conductive film 10A may be formed into a long film having a length of 5m or more, or may be formed into a wound body wound around a winding core.

The anisotropic conductive film 10A is constituted by the conductive particle dispersion layer 3, and the conductive particles 1 in the insulating resin layer 2 are not in contact with each other in the conductive particle dispersion layer 3. The conductive particles 1 are preferably arranged regularly on one surface of the insulating resin layer 2 in an exposed state. The conductive particles 1 do not contact each other in a plan view of the film, and the conductive particles 1 do not overlap each other in the film thickness direction. A conductive particle layer constituting a single layer in which the conductive particles 1 are aligned in the position in the film thickness direction is preferable. The proportion (number basis) of the conductive particles in a state of not contacting each other is preferably 95% or more, more preferably 98% or more.

A recess 2B may be formed in the surface 2a of the insulating resin layer 2 around each conductive particle 1 with respect to the tangential plane 2p of the insulating resin layer 2 in the central portion between adjacent conductive particles (fig. 1B and 2). In addition, as shown in fig. 2, the top 1a of the conductive particle 1 may be formed on the surface 2a of the insulating resin layer 2 in a single plane, and in this case, the movement of the conductive particle due to the resin flow at the time of anisotropic conductive connection can be reduced as compared with the case of fig. 1B. As described below, in the anisotropic conductive film of the present invention, the recesses 2c (fig. 3 and 4) may be formed on the surface of the insulating resin layer directly above the conductive particles 1 embedded in the insulating resin layer 2. In the case of fig. 3, a point of the top 1a of the conductive particle 1 may be exposed from the insulating resin layer.

< conductive particles >

The conductive particles 1 may be used by appropriately selecting metal-coated resin particles having a metal layer formed on the surface of the resin core particles from among conductive particles used in a known anisotropic conductive film. As such metal-coated resin particles, metal-coated resin particles having an insulating coating treatment (e.g., an insulating fine particle adhering treatment, an insulating resin coating treatment, etc.) applied to the surface thereof can be used. The metal-coated resin particles may be used in combination of 2 or more kinds. As the conductive particles 1, conductive particles having conductive protrusions on the surface thereof may be used. For example, the following conductive particles may also be used: conductive particles in which insulating particles serving as core materials of the protrusions are adhered to the surfaces of the resin core particles and the whole is covered with a conductive layer; conductive particles obtained by coating the surfaces of such conductive particles with other conductive layers; or conductive particles in which insulating particles serving as core material of the protrusions 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. The conductive layer may be a multilayer of 2 layers or more. Protrusions may be present between the conductive layers. Such a conductive layer may be formed on the surface of the resin core particle by a known film forming method such as electroless plating, electrolytic plating, or sputtering. There are also methods for attaching conductive fine particles, and the like, and there are no particular restrictions on the method as long as the conductive fine particles satisfy the following conditions and can satisfy the conduction performance. Further, a known insulating treatment may be performed on the surface of the conductive layer. In this case, the size of the insulating layer formed by the insulating treatment after the thickness thereof is removed is used as the particle diameter of the conductive particles.

The conductive particles 1 used in the present invention satisfy the following conditions (1) to (3).

< condition (1) >

The conductive particles used in the present invention have a lower limit of 20% compression elastic modulus (K) of 6000N/mm from the standpoint that even if an oxide film is formed on the surface of an electrode or terminal of an electronic component, the oxide film is broken through by the conductive particles ² Above, preferably 10000N/mm ² The above. Here, the 20% compression elastic modulus can be calculated by measuring a compression variable of the conductive particles when a compressive load is applied to the conductive particles (for example, by using a smooth indenter end surface of a cylinder (diameter: 50 μm, made of diamond) using a micro compression tester (for example, manufactured by Fischer corporation, fischer cope H-100), compressing the conductive particles at a compression speed of 2.6 mN/sec and a maximum test load of 10 gf), and applying the measured value to the following formula (1):

20% compression springModulus of nature (K) ([ N/mm) ² ])=(3/2 ^1/2 )·F·S ^-3/2 ·R ^-1/2 (1)

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

< condition (2) >

In addition, as described above, since the conductive particles used in the present invention are required to break through the oxide film formed on the electrode or terminal surface of the electronic component, a corresponding pressure is applied to the conductive particles at the time of connection. Thus, flattening of the conductive particles is expected. Therefore, after releasing the pressure of connection, the conductive particles are required to recover after compression, while sufficiently securing the contact area with the electrode or terminal surface facing each other. From this viewpoint, the lower limit of the compression recovery rate (X) is 40% or more, preferably 55% or more. If the upper limit is too high, there is a concern that the connection state of the cured or polymerized resin is maintained, and therefore too high is not desirable, and the upper limit is 80% or less, preferably 75% or less. Here, the compression recovery rate can be calculated by measuring the displacement (L2) from the initial load (load of 0.4 mN) to the load reversal (load of 5 mN) and the displacement (L1) from the load reversal to the final load (load of 0.4 mN) by compressing the conductive particles with a smooth indenter end surface of a cylinder (diameter of 50 μm, diamond) using the above-mentioned micro compression tester, and applying the measured values to the following formula (2):

Compression recovery rate (X [% ]) = (L1/L2) ×100 (2).

< condition (3) >

The conductive particles 1 used in the present invention have a lower limit of 1 μm or more, preferably 2.5 μm or more, in terms of coping with variations in wiring height, and an upper limit of 30 μm or less, preferably 9 μm or less, in terms of suppressing an increase in on-resistance and suppressing occurrence of short circuits. The average particle diameter can be obtained by using a general particle size distribution measuring apparatus (for example, FPIA-3000 (Malvern Panalytical)). The number of the measured samples is preferably 1000 or more. The average particle diameter D of the conductive particles in the anisotropic conductive film can be obtained by using an electron microscope such as SEM. In this case, the number of measurement samples is preferably 200 or more. In the case of using, as the conductive particles, conductive particles having insulating fine particles attached to the surfaces thereof, the average particle diameter of the conductive particles in the present invention means the average particle diameter of the insulating fine particles not including the surfaces.

< insulating resin layer 2>

In the anisotropic conductive film of the present invention, as described below, the insulating resin layer 2 that holds the conductive particles 1 and functions as a matrix layer of the anisotropic conductive film may be formed of a curable resin composition, and satisfies the following condition (4).

< condition (4) >

The minimum melt viscosity of the insulating resin layer 2 constituting the anisotropic conductive film of the present invention is preferably 4000pa·s or less, more preferably 3000pa·s or less, from the standpoint of reducing the pressure at the time of connection, suppressing deformation particularly when the substrate is plastic or the like, and enabling good press-in of the conductive particles. The lower limit is preferably not particularly limited, since the lower limit is preferably low in view of suppressing deformation particularly in the plastic substrate during connection, and the lower limit is preferably not less than 200pa·s, more preferably not less than 400pa·s, from the viewpoint of preventing excessive flow of the conductive particles 1 to be held between the terminals due to resin flow during anisotropic conductive connection and from the viewpoint of preventing resin overflow during package formation. The minimum melt viscosity can be obtained by using a rotary rheometer (manufactured by TA Instruments) and a measuring plate having a diameter of 8mm, with a measuring pressure of 5g, more specifically, a temperature range of 30 to 200℃and a temperature rise rate of 10 ℃/min, a measuring frequency of 10Hz, and a load fluctuation of 5g with respect to the measuring plate.

In the case where the conductive particle dispersion layer 3 of the anisotropic conductive film 10A is formed by pressing the conductive particles 1 into the insulating resin layer 2, the insulating resin layer 2 at the time of pressing the conductive particles 1 is formed as a viscous body having the following high viscosity: when the conductive particles 1 are pressed into the insulating resin layer 2 so that the exposed diameter Lc of the conductive particles 1 is exposed from the insulating resin layer 2, the insulating resin layer 2 is plastically deformed to form a viscous body of high viscosity with the recesses 2B (fig. 1B and 2) in the insulating resin layer 2 around the conductive particles 1, or when the conductive particles 1 are pressed into the insulating resin layer 2 so that the conductive particles 1 are not exposed from the insulating resin layer 2 but are buried in the insulating resin layer 2, a viscous body of high viscosity with the recesses 2c (fig. 3 and 4) is formed on the surface of the insulating resin layer 2 directly above the conductive particles 1. Therefore, the viscosity of the insulating resin layer 2 at 60 ℃ is preferably 3000 to 20000pa·s. The measurement was performed by the same measurement method as that of the lowest melt viscosity, and the temperature was found to be 60 ℃.

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 by referring to the description of the specification (paragraph 0054) of japanese patent No. 6187665.

As described above, by forming the recess 2B (fig. 1B and 2) around the conductive particle 1 exposed from the insulating resin layer 2, the resistance received from the insulating resin is reduced compared with the case without the recess 2B due to flattening of the conductive particle 1 generated when the conductive particle 1 is sandwiched between terminals during anisotropic conductive connection, and thus the conductive particle is easily sandwiched between terminals, and the conduction performance is improved and the trapping performance is improved.

Further, by forming the recess 2c (fig. 3 and 4) on the surface of the insulating resin layer 2 directly above the conductive particle 1 which is not exposed from the insulating resin layer 2, the pressure during anisotropic conductive connection is easily concentrated on the conductive particle 1, and the conductive particle 1 is easily sandwiched between terminals, thereby improving the trapping property and the conductive performance, as compared with the case where the recess 2c is not present.

(layer thickness of insulating resin layer)

In the anisotropic conductive film of the present invention, since the resin amount capable of holding the conductive particles is sufficient, the ratio (La/D) of the layer thickness La of the insulating resin layer 2 to the average particle diameter D of the conductive particles 1 is only 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. The average particle diameter D is defined as the size of the metal-coated resin particles (the size formed by the resin core particles and the conductive layer on the surface thereof). If the layer thickness La of the insulating resin layer 2 is too large relative to the conductive particles, the conductive particles are likely to be displaced during anisotropic conductive connection, and the trapping property of the conductive particles in the terminal is reduced. Therefore, the upper limit of La/D is preferably 8.0 or less, more preferably 6.0 or less.

(composition of insulating resin layer)

The insulating resin layer 2 may be formed of a curable resin composition, for example, a heat polymerizable composition containing a heat polymerizable compound and a heat polymerization initiator. The photopolymerizable composition may optionally contain a photopolymerization initiator.

When the thermal polymerization initiator and the photopolymerization initiator are used in combination, a substance that functions as both a thermal polymerizable compound and a photopolymerizable compound may be used, or the photopolymerizable compound may be contained separately from the thermal polymerizable compound. The photopolymerizable compound is preferably contained separately from the thermally polymerizable compound. For example, a cationic polymerization initiator is used as a thermal polymerization initiator, an epoxy resin is used as a thermal polymerizable compound, a photo radical polymerization initiator is used as a photopolymerization initiator, and an acrylate compound is used as a photopolymerizable compound.

As the photopolymerization initiator, a plurality of types of photoreaction different from the wavelength may be contained. Thus, the wavelength used in the photo-curing of the resin constituting the insulating resin layer at the time of preparing the anisotropic conductive film and the photo-curing of the resin for bonding the electronic parts to each other at the time of anisotropic conductive connection can be used separately.

In the photocuring in the production of the anisotropic conductive film, all or a part of the photopolymerizable compound contained in the insulating resin layer may be photocured. By this photocuring, the arrangement of the conductive particles 1 in the insulating resin layer 2 can be maintained or fixed, and it is expected to suppress short-circuiting and improve trapping. In addition, by the photo-curing, the viscosity of the insulating resin layer in the process of producing the anisotropic conductive film can be appropriately adjusted.

The amount of the photopolymerizable compound blended in the insulating resin layer is preferably 30 mass% or less, more preferably 10 mass% or less, and particularly preferably less than 2 mass%. This is because if the photopolymerizable compound is too much, the pushing force required for press-in at the time of connection increases.

Examples of the thermally polymerizable composition include a thermally radical polymerizable acrylate composition containing a (meth) acrylate compound and a thermal radical polymerization initiator, and a thermally cationic polymerizable epoxy composition containing an epoxy compound and a thermal cationic polymerization initiator. Instead of the thermal cationic polymerizable epoxy composition containing a thermal cationic polymerization initiator, a thermal anionic polymerizable epoxy composition containing a thermal anionic polymerization initiator may be used. In addition, a plurality of polymerizable compositions may be used in combination as long as they do not particularly cause any trouble. Examples of the use thereof include use of a combination of a hot cationic polymerizable composition and a hot radical polymerizable composition.

Here, as the (meth) acrylate compound, a conventionally known thermally polymerizable (meth) acrylate monomer can be used. For example, a monofunctional (meth) acrylate monomer or a multifunctional (meth) acrylate monomer having a difunctional or more group can be used.

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

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

Examples of the epoxy compound include bisphenol a type epoxy resin, bisphenol F type epoxy resin, phenol resin type epoxy resin, modified epoxy resin thereof, alicyclic epoxy resin, and the like, and 2 or more of them may be used in combination. In addition, an oxetane compound may be used in combination in addition to the epoxy compound.

As the thermal cationic polymerization initiator, a known one as a thermal cationic polymerization initiator of an epoxy compound can be used, and for example, an iodonium salt, a sulfonium salt, a phosphonium salt, or a ferrocene that generates an acid by heat can be used, and in particular, an aromatic sulfonium salt that exhibits good potential against temperature can be preferably used.

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

The thermally polymerizable composition preferably contains a film-forming resin or a silane coupling agent. Examples of the film-forming resin include phenoxy resins, epoxy resins, unsaturated polyester resins, saturated polyester resins, polyurethane resins, butadiene resins, polyimide resins, polyamide resins, and polyolefin resins, and 2 or more of them may be used in combination. Among them, phenoxy resins are preferably used from the viewpoints of film formability, workability, and connection reliability. The weight average molecular weight is preferably 10000 or more. The silane coupling agent may be an epoxy silane coupling agent, an acrylic silane coupling agent, or the like. These silane coupling agents are mainly alkoxysilane derivatives.

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

Further, a filler, a softener, an accelerator, an anti-aging agent, a colorant (pigment, dye), an organic solvent, an ion scavenger, and the like may be contained, which are different from the insulating filler.

< degree of holding of conductive particles by insulating resin layer >

As described above, the insulating resin layer 2 exhibiting the lowest melt viscosity holds the conductive particles 1, and the degree of holding thereof can be evaluated using the number density as an index. That is, in the anisotropic conductive film of the present invention, the following condition (5) is satisfied with respect to the number density of the conductive particles 1.

< condition (5) >

If the number density of conductive particles in the anisotropic conductive film of the present invention is too small in a planar view of the film, the on-resistance value may be increased due to a decrease in the number of trapped particles, and thus the lower limit is 6000 particles/mm ² The above is preferably 7500 pieces/mm ² The above. In addition, if the number density is too high, the pressure at the time of connection needs to be increased, and there is a concern that the substrate may be deformed in the case of plastic or the like, so that the upper limit is 36000 pieces/mm in order not to excessively increase the pressure at the time of connection ² Hereinafter, it is preferably 30000 pieces/mm ² The following is given. The number density of the conductive particles may be obtained by measuring an observation image using image analysis software (WinROOF, san francisco, inc.) in addition to the observation using a metal microscope. The observation method or the measurement method is not limited to the above method.

It is preferable that a rectangular region having 1 side of 100 μm or more is arbitrarily set as the measurement region of the number density of the conductive particles at a plurality of positions (preferably 5 or more, more preferably 10 or more) so that the total area of the measurement regions is 2mm ² The above. The size or number of the respective areas may be appropriately adjusted according to the state of the number density. As an example of the case where the number density for fine pitch use is large, for a region (2 mm) of an area of 100 μm×100 μm arbitrarily selected from the anisotropic conductive film 10A at 200 ² ) The number density is measured using an observation image obtained by a metal microscope or the like, and the number density is averaged to obtain "the number density of conductive particles in a plane view" in the above formula. In a connection object having a gap between bumps of 50 μm or less and an L/S (line/space) of 1 or less, a region having an area of 100 μm×100 μm is a region where 1 or more bumps are present.

< 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 are dispersed in a regular arrangement. In either case, alignment in the film thickness direction is preferable from the viewpoint of capturing stability. Here, the alignment of the conductive particles 1 in the film thickness direction is not limited to alignment at a single depth in the film thickness direction, and includes a method in which the conductive particles are present at or near the interface between the front surface and the back surface of the insulating resin layer 2.

In addition, from the viewpoint of suppressing short-circuiting, the conductive particles 1 are preferably arranged regularly in a planar view of the film. The arrangement is not particularly limited, since it depends on the layout of the terminals and the bumps. For example, in a plan view of the film, as shown in fig. 1A, the films may be arranged in a square lattice. Examples of the regular arrangement of the conductive particles include rectangular lattices, diagonal lattices, 6-square lattices, and 3-square lattices. A combination of a plurality of lattices of different shapes is also possible. Further, the conductive particles may be arranged in a linear array at predetermined intervals, and the particles may be arranged in parallel at predetermined intervals. By forming the conductive particles 1 in a regular arrangement such as a lattice shape without touching each other, pressure can be uniformly applied to each conductive particle 1 at the time of anisotropic conductive connection, and variation in on-resistance can be reduced.

In addition, in order to achieve both of the trapping stability and the short circuit suppression, 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 aligned.

On the other hand, when the gap between terminals of the connected electronic parts is large and short circuit is difficult to occur, the conductive particles may be randomly dispersed without being regularly arranged. In the case of dispersion, it is also preferable that each conductive particle is arranged in a non-contact manner (each conductive particle exists independently in a non-contact manner) in a planar view of the film. As an example of the layout of the terminals, the number ratio may be 75% or more, preferably 90% or more, more preferably 95% or more, and still more preferably 98% or more.

In the case where the conductive particles are arranged regularly, the lattice axis or the arrangement axis of the arrangement may be parallel to the longitudinal direction of the anisotropic conductive film or the direction perpendicular to the longitudinal direction, or may intersect the longitudinal direction of the anisotropic conductive film, and may be determined according to the width of the terminal to be connected, the pitch of the terminal, and the like. For example, in the case of producing an anisotropic conductive film for fine pitch, as shown in fig. 1A, it is preferable that 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, and the angle θ formed between the longitudinal direction of the terminal 200 (the transverse direction of the film) connected using 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.

The inter-particle distance of the conductive particles 1 is appropriately determined according to the size of the terminals connected by the anisotropic conductive film or the terminal pitch. In general, from the viewpoint of preventing occurrence of short-circuiting, the lower limit of the distance between nearest neighboring particles (i.e., the distance between nearest neighboring particles) is preferably 50% or more or any longer distance of 0.2 μm or more of the average particle diameter D of the conductive particles, and the upper limit is not particularly limited as long as the condition of the number density can be satisfied, and for example, it is preferably 30 μm or less as the maximum diameter of the average particle diameter D of the conductive particles, or 10 times or less as the average particle diameter D in the case where the average particle diameter D is small.

The area occupancy of the conductive particles in the planar view of the anisotropic conductive film of the present invention is an index of the thrust force required for the pressing jig to thermocompression bond the anisotropic conductive film to the electronic component. If the area occupancy is too large, the thrust increases, and when the substrate is a substance that is easily deformed such as plastic, the substrate 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. In addition, when the area occupation ratio is too small, the fine pitch may not be handled, and therefore, 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 formula:

area occupancy [%]= [ number density of conductive particles in plan view (number/mm ² )]X { [ average value of planar area of 1 conductive particle (. Mu.m) ² )]×10 ^-6 }×100

Here, as the measurement region of the number density and area occupancy of the conductive particles, as described in paragraph 0052, a rectangular region having 1 side of 100 μm or more at a plurality of points (preferably 5 points or more, more preferably 10 points or more) is preferably arbitrarily set so that the total area of the measurement regions is 2mm ² The above. The size or number of the respective areas may be appropriately adjusted according to 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, as described above, the conductive particles 1 may be exposed from the insulating resin layer 2 or may be buried in the insulating resin layer 2 without being exposed, but the ratio [ (Lb/D) ×100] (hereinafter referred to as a buried ratio) of the distance Lb between the deepest portion of the conductive particles and the tangential plane 2p of the central portion between adjacent conductive particles of the surface 2a of the insulating resin layer where the recesses 2b, 2c are formed to the buried amount Lb relative to the particle diameter D of the conductive particles 1 (hereinafter referred to as a buried ratio) is preferably 60% to 105%.

By setting the embedding rate to 60% or more, the conductive particles 1 can be maintained in a predetermined particle-dispersed state or a predetermined arrangement by the insulating resin layer 2, and by setting the embedding rate to 105% or less, the resin amount of the insulating resin layer functioning to cause conductive particles between terminals to flow unnecessarily at the time of anisotropic conductive connection can be reduced.

In the present invention, the term "embedding rate" means a value of embedding rate (Lb/D) which is 80% or more, preferably 90% or more, and more preferably 96% or more of the total number of conductive particles contained in the anisotropic conductive film. Accordingly, the 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. In this way, by making the embedding rate (Lb/D) of all the conductive particles uniform, the compressive load is uniformly applied to the conductive particles, so that the capturing state of the conductive particles in the terminal is good, and the stability of conduction is improved.

The embedding rate can be increased by arbitrarily extracting more than 10 parts of the anisotropic conductive film to 30mm ² The above region was obtained by observing a part of the cross section of the thin film with SEM images and measuring 50 or more conductive particles in total. In order to further improve the accuracy, 200 or more conductive particles may be measured.

The measurement of the embedding rate can be obtained by performing focus adjustment on the planar view image, and the number of the embedding rate is calculated to some extent. Alternatively, a laser-induced displacement sensor (manufactured by KEYENCE corporation, etc.) may be used for the measurement of the embedding rate.

< mode of deformation of Anisotropic conductive film >

(2. Insulating resin layer)

As in the anisotropic conductive film 10E shown in fig. 5, the anisotropic conductive film of the present invention can be formed by laminating the 2 nd insulating resin layer 4 (functioning as an insulating adhesive layer) having a lower minimum melt viscosity than the edge resin layer 2 on the surface of the conductive particle dispersion layer 3 on the side where the conductive particles 1 are held (in other words, the surface of the insulating resin layer 2 where the recesses 2c are formed). Further, as in the anisotropic conductive film 10F shown in fig. 6, the 2 nd 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 surface of the conductive particle dispersion layer 3 on the side where the conductive particles 1 are not held (in other words, the surface of the insulating resin layer 2 where the recesses 2c are not formed). By stacking the 2 nd insulating resin layer 4, when anisotropic conductive connection is performed to the electronic component using the anisotropic conductive film, the space formed by the electrode or the bump of the electronic component can be filled, and the adhesion can be improved. In the case of stacking the 2 nd insulating resin layer 4, the 2 nd insulating resin layer 4 is preferably located on the electronic component side such as an IC chip that is pressed with a tool (in other words, the insulating resin layer 2 is located on the electronic component side such as a substrate placed on a table) regardless of whether the 2 nd insulating resin layer 4 is located on the formation surface of the recess 2 c. Thus, unnecessary movement of the conductive particles can be avoided, and the trapping property can be improved.

The lower the difference in the minimum melt viscosity between the insulating resin layer 2 and the insulating resin layer 2, the easier the insulating resin layer 2 is to fill the space formed by the electrode or the bump of the electronic component with the insulating resin layer 4, and the effect of improving the adhesion between the electronic components can be expected. Further, the amount of movement of the insulating resin layer 2 present in the conductive particle dispersion layer 3 becomes relatively smaller as the difference is present, so that the capturing property of the conductive particles in the terminal is easily improved. Practically, the minimum melt viscosity ratio of the insulating resin layer 2 to the 2 nd insulating resin layer 4 (i.e., [ minimum melt viscosity of the insulating resin layer 2 ]/[ minimum melt viscosity of the 2 nd insulating resin layer 4 ]) is preferably 2 or more, more preferably 5 or more, and still more preferably 8 or more. On the other hand, if the ratio is too large, when the long anisotropic conductive film is formed into a package, resin may overflow or blocking may occur, and therefore 15 or less is practically preferable. The preferable minimum melt viscosity of the insulating resin layer 2 4 can be determined by referring to the description of the specification of japanese patent No. 6187665 (paragraph 0091).

The 2 nd insulating resin layer 4 may be formed by adjusting the viscosity in the same resin composition as the insulating resin layer.

In the anisotropic conductive films 10E and 10F, the layer thickness of the 2 nd insulating resin layer 4 is preferably 4 μm or more and 20 μm or less. Alternatively, the conductive particle diameter is preferably 1 to 8 times.

The minimum melt viscosity of the entire anisotropic conductive films 10E and 10F formed by combining the insulating resin layer 2 and the 2 nd insulating resin layer 4 is preferably 200pa·s or more and 4000pa·s or less. The minimum melt viscosity of the 2 nd insulating resin layer 4 itself is preferably 2000pa·s or less, more preferably 100 to 2000pa·s, on the premise that the minimum melt viscosity ratio is satisfied.

(3. Insulating resin layer)

The 3 rd insulating resin layer may be provided on the opposite side to the 2 nd insulating resin layer 4 with the insulating resin layer 2 interposed therebetween. For example, the 3 rd insulating resin layer or the insulating adhesive layer may be made to function as an adhesive layer. The insulating resin layer may be provided to fill a space formed by an electrode or a bump of an electronic component, similarly to the insulating resin layer 2.

The resin composition, viscosity and thickness of the 3 rd insulating resin layer may be the same as or different from those of the 2 nd insulating resin layer. The minimum melt viscosity of the anisotropic conductive film formed by combining the insulating resin layer 2, the 2 nd insulating resin layer 4 and the 3 rd insulating resin layer is not particularly limited, and may be 200 to 4000pa·s.

< method for producing anisotropic conductive film >

The anisotropic conductive film of the present invention can be prepared by a preparation method having the steps of: and a step of forming a conductive particle dispersion layer by pressing conductive particles into the insulating resin layer. As a preferable mode of this step, the following modes are listed: a method in which conductive particles are held on the surface of an insulating resin layer in a predetermined arrangement, and the conductive particles are pressed into the insulating resin layer by a plate or a roller, thereby forming a conductive particle dispersion layer; or by filling the conductive particles in a transfer mold and transferring the conductive particles onto the insulating resin layer, the conductive particles are held on the surface of the insulating resin layer in a predetermined arrangement. The following modes are also exemplified: a manner in which the conductive particles are directly dispersed and held in the insulating resin layer 2; or a method in which the conductive particles 1 are adhered as a single layer to a biaxially stretchable film, the film is biaxially stretched, the insulating resin layer 2 is pressed against the stretched film, and the conductive particles are transferred to the insulating resin layer 2, whereby the conductive particles 1 are held in the insulating resin layer 2.

In the case of a method of forming the conductive particle dispersion layer by pressing conductive particles into the insulating resin layer, the lowest melt viscosity of the insulating resin layer can be determined with reference to the description of japanese patent No. 6187665 (paragraph 0097). Thus, the conductive particles can be pressed so that the surface of the insulating resin layer constituting the surface of the conductive particle dispersion layer is recessed from the tangential plane of the insulating resin layer in the central portion between adjacent conductive particles.

In the case of preparing an anisotropic conductive film having an embedding rate exceeding 100%, the anisotropic conductive film may be pressed by a pressing plate so as to have convex portions corresponding to the arrangement of conductive particles.

In the case of holding the conductive particles 1 in the insulating resin layer 2 using a transfer mold, for example, a transfer mold in which openings are formed by a known opening forming method such as photolithography, for example, using an inorganic material such as silicon, various ceramics, glass, stainless steel, or various organic materials such as resins, or the like, as a transfer mold, a transfer mold by a printing method is used. In addition, the transfer mold may take a plate-like, roll-like shape, or the like. It should be noted that the present invention is not limited to the above method.

Further, the 2 nd insulating resin layer having a lower viscosity than the insulating resin layer may be laminated on the surface of the insulating resin layer pressed with the conductive particles on the side of the conductive particles or on the opposite side thereof.

In order to economically connect electronic parts using the anisotropic conductive film, the anisotropic conductive film is preferably long to some extent. Therefore, the length of the anisotropic conductive film is particularly preferably 5m or more. It can also be determined by referring to the description of Japanese patent No. 6187665 (paragraph 0103). In addition, in the case of using an anisotropic conductive film practically, it is realistic to wind the film onto a reel to form a wound body. However, when the resin viscosity (i.e., substantially proportional to the lowest melt viscosity of the film) is too low in the case of producing a package in this way, problems such as overflow and blocking sometimes occur when the connection is continuously performed. Therefore, the minimum melt viscosity of the anisotropic conductive film is preferably 200pa·s or more. The same applies to the lamination of the 2 nd insulating resin layer or the 3 rd insulating resin layer.

< method of Using Anisotropic conductive film >

The anisotropic conductive film of the present invention is particularly preferably used in the case where the 1 st electronic component (the side heated by a tool) is a flexible material such as an IC chip, an IC module, or the like (for example, a semiconductor element formed from a wafer belonging to a general IC chip), or the 2 nd electronic component (the side placed on a stage) is a plastic substrate. It should be noted that the anisotropic conductive connection is not excluded in a manner including a combination of a 1 st electronic component such as a semiconductor element, an IC chip, an IC module, or an FPC, and a 2 nd electronic component such as an FPC, a glass substrate, a plastic substrate, a rigid substrate, or a ceramic substrate. In addition, IC chips or wafers may be stacked and multilayered using the anisotropic conductive film of the present invention. The electronic component connected by the anisotropic conductive film of the present invention is not necessarily limited to the above electronic component. Can be used for various electronic parts in recent years. For example, in the case of using an IC chip or FPC as the 1 st electronic part, an OLED plastic substrate may be used as the 2 nd electronic part. In particular, the present invention is particularly advantageous when a COP structure is formed in which the 1 st electronic component is an IC chip and the 2 nd electronic component is a plastic substrate. Accordingly, the present invention also includes "a connection structure in which the 1 st electronic component and the 2 nd electronic component are anisotropically electrically connected by the anisotropic conductive film of the present invention" and "a method for producing a connection structure in which the 1 st electronic component and the 2 nd electronic component are anisotropically electrically connected by the anisotropic conductive film of the present invention".

As a connection method of electronic parts using the anisotropic conductive film, in the case where the anisotropic conductive film is constituted of a single layer of the conductive particle dispersion layer 3, it can be prepared by the following method: for the 2 nd electronic components such as various substrates, the anisotropic conductive film is temporarily bonded from the side where the conductive particles 1 are embedded on the surface thereof, and then temporarily pressure bonded, and the 1 st electronic components such as IC chips are stacked on the side where the conductive particles 1 are not embedded on the surface of the anisotropic conductive film temporarily pressure bonded, and then thermally pressure bonded. In the case where the insulating resin layer of the anisotropic conductive film contains not only the thermal polymerization initiator and the thermal polymerizable compound but also the photopolymerization initiator and the photopolymerizable compound (which may be the same as the thermal polymerizable compound), a pressure bonding method using both light and heat may be used. Thus, unnecessary movement of the conductive particles can be suppressed to the minimum. The side not embedded with the conductive particles may be temporarily attached to the 2 nd electronic component for use. Note that, the anisotropic conductive film may be temporarily attached to the 1 st electronic component instead of the 2 nd 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 2 nd insulating resin layer 4 (functioning as an insulating adhesive layer), the conductive particle dispersion layer 3 is temporarily adhered and temporarily bonded to the 2 nd electronic components such as various substrates, and the 1 st electronic components such as IC chips are placed in alignment on the 2 nd insulating resin layer 4 side of the temporarily bonded anisotropic conductive film and thermally bonded. The 2 nd insulating resin layer 4 side of the anisotropic conductive film may be temporarily stuck to the 1 st electronic component. The conductive particle dispersion layer 3 side may be temporarily attached to the 1 st electronic component for use.

Examples

The present invention will be specifically described below with reference to examples.

Examples 1 to 8, comparative example 1 and reference example 1

(1) Preparation of resin composition for Forming insulating resin layer and insulating adhesive layer

Resin compositions for forming the insulating resin layer, the 2 nd insulating resin layer and the insulating adhesive layer were prepared by blending as shown in table 1. The minimum melt viscosity of the resulting composition was determined by the following method: a rotary rheometer (TA Instruments) was used, the pressure was kept constant at 5g, a measuring plate having a diameter of 8mm was used, and the temperature rise rate was set to 10℃per minute, the measuring frequency was set to 10Hz, and the load fluctuation relative to the measuring plate was set to 5g at a temperature range of 30 to 200 ℃. The results obtained are shown in table 1. Blend B, blend C and blend D are resin compositions used in the present invention. Blend a and blend E are resin compositions for comparative examples.

(2) Production of conductive particles

As the conductive particles 1 to 4 in Table 2, metal-coated resin particles (Au/Ni plated, average particle diameter: 3 μm) were prepared from water chemical industry Co. Here, the 20% compression elastic modulus and the compression recovery rate were carried out as described below using a micro compression tester (Fischer Co., ltd., fischer slope H-100).

<20% modulus of elasticity under compression >

The compression variable of the conductive particles at a compression rate of 2.6 mN/sec and a maximum test load of 10gf was measured on the smooth indenter end face of a cylinder (diameter: 50 μm, made of diamond) using a micro compression tester, and the value obtained by the measurement was calculated by applying the following formula (1):

20% modulus of elasticity under compression (K) ([ N/mm) ² ])=(3/2 ^1/2 )·F·S ^-3/2 ·R ^-1/2 (1)

< compression recovery Rate >

Using a micro compression tester, the conductive particles were compressed with a smooth indenter end surface of a cylinder (diameter: 50 μm, diamond), and the displacement (L2) from the initial load (load: 0.4 mN) to the load reversal (load: 5 mN) and the displacement (L1) from the load reversal to the final load (load: 0.4 mN) were measured, and the measured values were calculated by applying them to the following formula (2):

Compression recovery rate (X [% ]) = (L1/L2) ×100 (2)

The

conductive particles

1, 3, and 4 are conductive particles used in the present invention, and the conductive particles 2 are conductive particles used in the comparative example.

(3) Formation of insulating resin layer, insulating resin layer 2 and insulating adhesive layer

A PET film having a film thickness of 50 μm was coated with a resin composition (see table 1) for forming an insulating resin layer, a 2 nd insulating resin layer or an insulating adhesive layer by a bar coater, and dried in an oven at 80 ℃ for 5 minutes to form an insulating resin layer having a thickness shown in table 3 on the PET film. Similarly, the 2 nd insulating resin layer or the insulating adhesive layer was formed on the other PET film at the thickness shown in table 3.

TABLE 1

TABLE 2

(4) Manufacture of resin transfer form

The mold was manufactured such that the conductive particles 1 were arranged in a square lattice as shown in fig. 1A in a plan view, the inter-particle distance was equal to the average particle diameter of the conductive particles, and the number density of the conductive particles was the numerical value shown in table 3. That is, a mold was produced such that the convex portions of the mold were arranged in a square lattice, the pitch of the convex portions on the lattice axis was 2 times the average conductive particle diameter, the angle θ formed between the lattice axis and the transverse direction of the anisotropic conductive film was 15 °, and pellets of a known transparent resin were injected into the mold in a molten state, and cooled and solidified to form a resin transfer template having depressions in the arrangement pattern shown in fig. 1A.

(5) Fabrication of anisotropic conductive film

The recesses of the resin mold having the number of recesses corresponding to the number density of the conductive particles shown in table 2 were filled with the conductive particles shown in table 3, and the insulating resin layer was covered thereon, and the resin mold was bonded by pressing at 60 ℃ and 0.5 MPa. Then, the insulating resin layer was peeled off from the mold, and the conductive particles on the insulating resin layer were pressed into the insulating resin layer by pressing (pressing conditions: 60 to 70 ℃ C., 0.5 MPa), whereby anisotropic conductive films each composed of a single layer of the conductive particle-dispersed layer were produced (examples 1 to 5, comparative example 1, and reference example 1). The embedding state of the conductive particles is controlled by the pressing-in conditions (mainly, pressure conditions and temperature conditions).

Further, a two-layer anisotropic conductive film was produced by laminating a 2 nd insulating resin layer on the conductive particle dispersion layer produced in the same manner (examples 6 and 7). Further, a 3-layer anisotropic conductive film (example 8) was produced by laminating an insulating adhesive layer having tackiness on the conductive particle dispersion layer side of the two-layer anisotropic conductive film produced in the same manner.

(6) Evaluation

The anisotropic conductive films of the examples and comparative examples produced in (5) were measured or evaluated for (a) initial on-resistance, (b) on-reliability, (c) indentation, and (d) particle trapping properties as described below. The results are shown in table 3.

(a) Initial on-resistance

The anisotropic conductive films of examples and comparative examples were sandwiched between an evaluation IC having conductive properties and a plastic substrate, and each of the evaluation connectors was obtained by heating and pressurizing (180 ℃, 60MPa, 5 seconds), and the on-resistance of the obtained evaluation connector was measured. The initial on-resistance is practically preferably 2 Ω or less.

Here, the evaluation IC corresponds to the terminal pattern of the plastic substrate, and the dimensions are as follows. When the evaluation IC and the plastic substrate are connected, the longitudinal direction of the anisotropic conductive film is overlapped with the lateral direction of the bump.

IC for evaluating conduction characteristics

Outline 1.8X20.0 mm

Thickness of 0.5mm

Bump specification size 30×85 μm, bump distance 50 μm, bump height 15 μm

Plastic substrate (ITO wiring)

Substrate material polyethylene terephthalate matrix film/polyurethane adhesive/polyimide film (PET/PU/PI substrate)

The outline is 30X 50mm

Thickness of 0.5mm

And electrode ITO wiring.

(b) Conduction reliability

The on-resistance of the evaluation connector produced in (a) was measured in the same manner as the initial on-resistance after being placed in a constant temperature bath at a temperature of 85 ℃ and a humidity of 85% rh for 500 hours. The conduction reliability is preferably 5Ω or less in practical use, and more preferably 2Ω or less.

(c) Indentation of

The evaluation connector produced in (a) was observed from the plastic substrate side by a metal microscope to confirm whether or not an indentation was observed in the central portion of the bump end portion. The observed cases were evaluated as acceptable (good), and the cases not observed were evaluated as unacceptable (bad).

(d) Particle trapping

Using an evaluation IC for particle trapping, the alignment of the evaluation IC and a plastic (PET/PU/PI) substrate (ITO wiring) corresponding to the terminal pattern was shifted by 6 μm, and the substrate was heated and pressurized (180 ℃, 60MPa, 5 seconds), and the number of conductive particles trapped was measured in 100 areas of 6 μm×66.6 μm where the bumps of the evaluation IC overlapped with the terminals of the substrate, and the lowest number of trapping was obtained, and the evaluation was performed according to the following criteria. In practice, the evaluation is preferably B or more.

IC for evaluating particle trapping property

Outline 1.6X29.8 mm

Thickness of 0.3mm

Bump specification size 12×66.6 μm, bump pitch 22 μm (L/s=12 μm/10 μm), bump height 12 μm

Particle Capacity evaluation criterion

More than A5

More than B3 and less than 5

C is lower than 3.

TABLE 3

(consider

From the results of table 3, the anisotropic conductive films of examples 1 to 8 satisfying the following conditions (1) to (5) showed preferable results of not less than a practically problematic level for each of the characteristics of (a) initial on-resistance, (b) on-reliability, (c) indentation, and (d) particle trapping property:

< condition (1) >

< condition (2) >

< condition (3) >

< condition (4) >

< condition (5) >

On the other hand, the anisotropic conductive film of comparative example 1 exceeding the numerical range of condition (4) has a problem in terms of "on reliability". In addition, there are problems with "indentation". The anisotropic conductive film of reference example 1, which is slightly shifted downward from the numerical ranges of conditions (1) and (2), has a slightly higher initial on-resistance or resistance value in on-reliability than the anisotropic conductive films of examples 1 to 8, but is not a practically problematic level. However, considering the fluctuation of the connection conditions at the time of production, the initial on-resistance and the resistance value in the on-reliability are preferably low as in examples 1 to 8.

Industrial applicability

In the anisotropic conductive film of the present invention, as the conductive particles held in the conductive particle dispersion layer, conductive particles having a 20% compression elastic modulus, a compression recovery rate, and an average particle diameter respectively in a specific numerical range are used, as the insulating resin layer for holding such conductive particles, an insulating resin layer having a minimum melt viscosity of a specific numerical value or less is used, and the degree (in other words, the number density) of holding the conductive particles in such insulating resin layer is set in a specific range. Therefore, in the case where an electronic component having bumps such as an image display device or a driving IC chip is anisotropically connected to a flexible plastic substrate on which electrodes and wirings are formed by the anisotropic conductive film of the present invention, cracks can be prevented from being generated on the wirings of the plastic substrate, and an indentation showing good anisotropically conductive connection can be generated, and good conductive reliability evaluation can be obtained at the time of anisotropically conductive connection. Therefore, the anisotropic conductive film of the present invention is useful for anisotropically connecting an electronic component (particularly, an IC chip) to not only a glass substrate but also a plastic substrate.

Description of the marking

1. Conductive particles

1a conductive particle top

2. Insulating resin layer

2a surface of insulating resin layer

2b recess

2c recess

2p tangent plane

3. Conductive particle dispersion layer

4. 2 nd insulating resin layer

Examples of 10A, 10B, 10C, 10D, 10E, and 10F anisotropic conductive films

200. Terminal for connecting a plurality of terminals

Lattice axis of arrangement of A conductive particles

Average particle diameter of conductive particles

Layer thickness of La insulating resin layer

Lb-embedded amount (distance of deepest portion of conductive particles from tangent plane of center portion between neighboring conductive particles)

Lc exposed diameter

The longitudinal direction of the θ terminal makes an angle with the lattice axis of the arrangement of the conductive particles.

Claims

1. An anisotropic conductive film having at least a conductive particle dispersion layer composed of an insulating resin layer and conductive particles dispersed therein, satisfying the following conditions (1) to (5):

< condition (1) >

< condition (2) >

< condition (3) >

< condition (4) >

< condition (5) >

The number density of the conductive particles is 6000 pieces/mm ² Above and 36000/mm ² The following are set forth;

the conductive particles are arranged in the insulating resin layer in a noncontact manner,

the distance between nearest neighboring particles of the conductive particles is any longer distance of 50% or more or 0.2 μm or more of the average particle diameter of the conductive particles.

2. The anisotropic conductive film according to claim 1, wherein the insulating resin layer has a minimum melt viscosity of 200 Pa-s or more.

3. The anisotropic conductive film of claim 1, wherein the conductive particles are regularly arranged in a top view.

4. The anisotropic conductive film according to claim 1, wherein the 2 nd insulating resin layer is laminated on the surface of the conductive particle dispersion layer on the side where the conductive particles are held.

5. The anisotropic conductive film according to claim 1, wherein the 2 nd insulating resin layer is laminated on the surface of the conductive particle dispersion layer on the side where the conductive particles are not held.

6. The anisotropic conductive film of claim 4, wherein the lowest melt viscosity of the 2 nd insulating resin layer is lower than the lowest melt viscosity of the insulating resin layer.

7. The anisotropic conductive film according to any of claims 4 to 6, wherein the minimum melt viscosity ratio of the insulating resin layer to the insulating resin layer 2 is 2 or more.

8. A method for producing an anisotropic conductive film according to claim 1, comprising the step of forming a conductive particle dispersion layer by pressing conductive particles into an insulating resin layer.

9. The production method according to claim 8, wherein the conductive particles are held on the surface of the insulating resin layer in a predetermined arrangement, and the conductive particles are pressed into the insulating resin layer by a plate or a roller, whereby the conductive particle-dispersed layer is formed.

10. The production method according to claim 9, wherein the conductive particles are held on the surface of the insulating resin layer in a predetermined arrangement by filling the conductive particles in a transfer mold and transferring the conductive particles to the insulating resin layer.

11. A connection structure in which a 1 st electronic component and a 2 nd electronic component are anisotropically electrically connected by the anisotropic conductive film according to any one of claims 1 to 7.

12. The connection structure of claim 11, wherein the 1 st electronic component is an IC chip or an IC module, and the 2 nd electronic component is a plastic substrate.

13. A method for producing a connection structure by anisotropically electrically connecting an electronic component 1 and an electronic component 2 via the anisotropic conductive film according to any one of claims 1 to 7.