CN112740483A

CN112740483A - Anisotropic conductive film, connection structure, and method for producing connection structure

Info

Publication number: CN112740483A
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: 2021-04-30
Anticipated expiration: 2039-09-27
Also published as: TW202028001A; CN112740483B; JP2020095941A; KR20210033513A

Abstract

Is suitable for electronic parts with bumps such as image display element and driving IC chipAnd an anisotropic conductive film which is formed on the flexible plastic substrate and has transparent electrodes and wiring and which is connected to the flexible plastic substrate in an anisotropic conductive manner, the anisotropic conductive film having 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 20% compressive modulus of elasticity of the conductive particles was 6000N/mm²Above and 15000N/mm²The following; condition (2): the conductive particles have a compression recovery rate of 40% to 80%; condition (3): the conductive particles have an average particle diameter of 1 μm or more and 30 μm or less, and the condition (4): the lowest melt viscosity of the insulating resin layer is 4000Pa · s or less; and condition (5): the number density of the conductive particles is 6000/mm²Above and 36000 pieces/mm²The following.

Description

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

Technical Field

The present invention relates to an anisotropic conductive film.

Background

In order to reduce the weight and curve the image display panel, a flexible plastic substrate is used as a substrate for mounting electronic components such as an image display device and a driver IC chip. As a representative example of such a plastic substrate, from the viewpoint of preventing thermal deformation and reflection (see り Write み), 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 urethane adhesive layer 23 as shown in fig. 7 (patent document 1).

Documents of the prior art

Patent document

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

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 adhesive. 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 bumps and the electrodes of the plastic substrate after the bumps of the IC chip have broken through the oxide film on the electrode surface of the plastic substrate, the IC chip is pressed into the plastic substrate by a large pressing force.

Therefore, since the rigidity of the IC chip is much higher than that of the plastic substrate, the plastic substrate is deformed more by the pressing at the time of connection, and there is a possibility that "disconnection of the wiring on the plastic substrate side" or "insufficient press-in of the particles" may occur. Specifically, as shown in fig. 8, when heating and pressing are performed to anisotropically and electrically connect the bumps B of the IC chip and the electrodes 21 of the plastic substrate 24 via the anisotropic conductive film ACF, there is a possibility that the adhesive layer 23 of the plastic substrate 24 is removed outside the periphery of the bumps B of the IC chip, and an inverted dome-shaped thin portion 25 is formed (doming) phenomenon). When such a bulging phenomenon occurs, a crack may occur in the vicinity 26 of the shoulder on the wiring 21a extending from the electrode 21. Further, in order to evaluate the conduction reliability of the anisotropic conductive connection, the evaluation was performed by observing indentations formed by the conductive particles sandwiched between the electrode 21 and the bump B from the side of the polyethylene terephthalate film 20, but there was a possibility that the conductive particles 27a sandwiched between the bump B and the electrode 21 were observed to have indentations showing good connection in the vicinity of the edge E of the pressing surface of the bump, and the conductive particles 27B sandwiched between the bump B and the electrode were hardly observed to have indentations showing good connection (i.e., the sandwiched state of the conductive particles) in the vicinity of the center C of the pressing surface of the bump B. When such indentation is not observed, there is a problem that evaluation of conduction characteristics (initial conduction, conduction reliability, and the like) has to be reduced even if good conduction is present.

In order to eliminate such a concern, for example, studies have been made from the viewpoints of (a) adjusting the anisotropic conductive connection condition, (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 the research from the viewpoint of (a), it is necessary to modify or newly introduce a manufacturing facility, and in the case of the research from the viewpoints of (b) and (c), it is necessary to change the specification of the electronic component as the anisotropic conductive connection object. Therefore, it is required to study from the viewpoint of (d) without modifying or newly installing manufacturing equipment or changing the specification of an electronic component to be subjected to anisotropic conductive connection.

An object of the present invention is to solve the above-described problems of the related art and to provide an anisotropic conductive film which is particularly suitable for anisotropic conductive connection of an electronic component having bumps, such as an image display element 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, metal oxide electrodes such as ITO, or metal oxide electrodes obtained by oxidizing the surfaces of the above-described metal electrodes) are formed, and which can realize high conduction reliability by forming indentations that show good anisotropic conductive connection without causing cracks in the wiring of the plastic substrate at the time of anisotropic conductive connection.

Means for solving the problems

The present inventors have focused on the fact that conductive particles are subjected to a compressive force in the thickness direction of the film when anisotropic conductive connection is performed using an anisotropic conductive film having at least an insulating resin layer and a conductive particle dispersion layer composed of conductive particles dispersed therein, and have found that the object of the present invention can be satisfied by controlling an element that strongly affects the behavior of the conductive particles when compressed, and have completed the present invention by controlling the 20% compressive modulus of elasticity, the compressive recovery rate, the average particle diameter, the number density, and the minimum melt viscosity of the insulating resin layer within specific numerical ranges on the assumption that the object of the present invention can be achieved.

That is, 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 20% compressive modulus of elasticity of the conductive particles was 6000N/mm²Above and 15000N/mm²The following;

< Condition (2) >

The conductive particles have a compression recovery rate of 40% to 80%;

< Condition (3) >

The average particle diameter of the conductive particles is 1-30 [ mu ] m;

< Condition (4) >

The lowest melt viscosity of the insulating resin layer is 4000Pa · s or less; and

< Condition (5) >

The number density of the conductive particles is 6000/mm²Above and 36000 pieces/mm²The following.

The present invention also provides a method for producing the anisotropic conductive film of the present invention, including a step of forming a conductive particle dispersed layer by pressing conductive particles into an insulating resin layer. Preferred embodiments of this step include the following: a method of forming a conductive particle dispersion layer by holding conductive particles in a predetermined arrangement on the surface of an insulating resin layer and pressing the conductive particles into the insulating resin layer with a flat plate or a roller; or a method in which conductive particles are filled in a transfer mold and transferred onto an insulating resin layer, thereby holding the conductive particles in a predetermined arrangement on the surface of the insulating resin layer.

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

ADVANTAGEOUS EFFECTS OF INVENTION

The anisotropic conductive film of the present invention has a conductive particle dispersed 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 each having a specific numerical value range in each of the 20% compressive modulus of elasticity, the compressive recovery rate, and the average particle diameter are used, and as the insulating resin layer holding such conductive particles, an insulating resin layer 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 to be within a specific range. Therefore, when an electronic component having bumps, such as an image display element or a driving IC chip, is anisotropically and electrically connected to a flexible plastic substrate on which electrodes and wirings are formed by the anisotropic conductive film of the present invention, the wirings of the plastic substrate can be prevented from being cracked. Further, an indentation showing good anisotropic conductive connection can be generated, and good evaluation of conduction reliability can be obtained in the case of anisotropic conductive connection.

Drawings

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

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

FIG. 2 is a sectional view of the anisotropic conductive film 10B of the embodiment.

FIG. 3 is a sectional view of the anisotropic conductive film 10C of the embodiment.

FIG. 4 is a sectional view of the anisotropic conductive film 10D of the embodiment.

FIG. 5 is a sectional view of the anisotropic conductive film 10E of the embodiment.

FIG. 6 is a cross-sectional view of the 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 showing a case where an IC chip is anisotropically conductively connected to a plastic substrate.

Detailed Description

The anisotropic conductive film of the present invention has a conductive particle dispersed 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): "20% compression elastic modulus", condition (2): "compression recovery rate" and condition (3): the conductive particles having "average particle diameters" in specific numerical ranges are used as the insulating resin layer for holding such conductive particles under the condition (4): the "lowest melt viscosity" is an insulating resin layer in a specific range, and as the degree of holding the conductive particles in such an insulating resin layer, the condition (5): 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 drawings. In the following drawings, the same reference numerals denote the same or equivalent components.

< Overall Structure of Anisotropic conductive film >

Fig. 1A is a plan view illustrating the arrangement of particles 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 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 embodiment disclosed in these drawings.

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

The anisotropic conductive film 10A is composed of the conductive particle dispersed layer 3, and in the conductive particle dispersed layer 3, the conductive particles 1 are in a state of not being in contact with each other in the insulating resin layer 2. The conductive particles 1 are preferably regularly arranged on one surface of the insulating resin layer 2 in an exposed state. The conductive particles 1 are not in contact with each other in a plan view of the film, and the conductive particles 1 are not overlapped with each other in the film thickness direction. The conductive particle layer preferably constitutes a single layer in which the conductive particles 1 are aligned in position in the film thickness direction. The proportion (based on the number) of the conductive particles in a state of not contacting 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 can be formed with respect to a tangent plane 2p of the insulating resin layer 2 at the center portion between adjacent conductive particles (fig. 1B, 2). In addition, as shown in fig. 2, the top portions 1a of the conductive particles 1 can be flush with the surface 2a of the insulating resin layer 2, and in this case, the movement of the conductive particles 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 depressions 2c can be formed on the surface of the insulating resin layer directly above the conductive particles 1 embedded in the insulating resin layer 2 (fig. 3 and 4). 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 can be used by appropriately selecting metal-coated resin particles having a metal layer formed on the surface of a resin core particle from conductive particles used in known anisotropic conductive films. As such metal-coated resin particles, metal-coated resin particles whose surfaces have been subjected to an insulating coating treatment (for example, an insulating fine particle adhesion treatment, an insulating resin coating treatment, or the like) can be used. The metal-coated resin particles may be used in combination of 2 or more. 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 a core material of the protrusions are attached to the surface of resin core particles and the entire resin core particles are covered with a conductive layer; conductive particles in which the surfaces of such conductive particles are further coated with another conductive layer; or conductive particles in which insulating particles serving as a core material of the protrusions are attached to the surface of resin core particles coated with a conductive layer, and the entire surface is further coated with a conductive layer. The conductive layer may be 2 or more layers. The protrusions may be present between the conductive layers. Such a conductive layer can be formed by a known film forming method such as electroless plating, electrolytic plating, or sputtering on the surface of the resin core particle. Further, there are also methods of adhering conductive fine particles, and the like, and there is no particular limitation as long as the conductive 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 except the thickness thereof is defined 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 lower limit of the 20% compression modulus (K) of the conductive particles used in the present invention is 6000N/mm from the viewpoint that the oxide film is broken through by the conductive particles even if the oxide film is formed on the surface of the electrode or terminal of the electronic component²Above, preferably 10000N/mm²The above. Here, the 20% compressive elastic modulus can be calculated by measuring a compression variation of the conductive particles when a compressive load is applied to the conductive particles (for example, when the conductive particles are compressed under a condition that a compression rate is 2.6 mN/sec and a maximum test load is 10gf with a smooth indenter end face of a cylinder (made of diamond with a diameter of 50 μm) using a minute compression tester (for example, Fischer scope H-100, manufactured by Fischer corporation), and applying the measured value to the following formula (1):

modulus of elasticity (K) at 20% compression ([ 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 compressed and deformed by 20%, S is a compression displacement (mm) when the conductive particles are compressed and deformed by 20%, and R is a radius (mm) of the conductive particles.

< Condition (2) >

Further, as described above, 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 the terminal of the electronic component, a corresponding pressure is applied to the conductive particles at the time of connection. This can be expected to flatten the conductive particles. Therefore, after the pressure for connection is released, the conductive particles are required to be restored after compression while sufficiently securing a contact area with the opposing electrode or terminal surface. 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, the connection state of the cured or polymerized resin may be maintained, and therefore, the upper limit is not so high, and is preferably 80% or less, and more preferably 75% or less. Here, the compression recovery rate can be calculated by measuring the displacement (L2) from the initial load (load of 0.4mN) to the load reversal (load of 5mN) and the displacement (L1) from the load reversal to the final load (load of 0.4mN) by compressing the conductive particles with the smooth indenter end face of a cylinder (diameter of 50 μm, made of 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 lower limit of the average particle diameter of the conductive particles 1 used in the present invention is 1 μm or more, preferably 2.5 μm or more, from the viewpoint of coping with variations in wiring height, and the upper limit thereof is 30 μm or less, preferably 9 μm or less, from the viewpoint of suppressing an increase in on-resistance and suppressing occurrence of short circuits. The average particle diameter can be determined by using a general particle size distribution measuring apparatus (for example, FPIA-3000 (Malvern Panalytical). The number of samples to be measured is preferably 1000 or more. The average particle diameter D of the conductive particles in the anisotropic conductive film can be determined by an electron microscope such as SEM. In this case, the number of samples to be measured is preferably 200 or more. When conductive particles having insulating fine particles attached to the surfaces thereof are used as the conductive particles, the average particle diameter of the conductive particles in the present invention means the average particle diameter of the insulating fine particles excluding 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 the following condition (4) is satisfied.

< Condition (4) >

The minimum melt viscosity of the insulating resin layer 2 constituting the anisotropic conductive film of the present invention is 4000Pa · s or less, preferably 3000Pa · s or less, from the viewpoint of suppressing deformation particularly when the substrate is plastic or the like by reducing the pressure at the time of connection and allowing good press-fitting of the conductive particles. Further, from the viewpoint of suppressing deformation particularly in a plastic substrate at the time of connection, the lower limit thereof is desirably low, and therefore there is no particular limitation, and it is possible to adjust it as appropriate, but from the viewpoint of preventing excessive flow of the conductive particles 1 to be held between the terminals due to resin flow at the time of anisotropic conductive connection and from the viewpoint of preventing overflow of the resin at the time of formation into a wound body, it is preferably 200Pa · s or more, and more preferably 400Pa · s or more. Here, the minimum melt viscosity can be determined by using a measuring plate having a diameter of 8mm, which is kept constant at a measuring pressure of 5g by using a rotary rheometer (TA Instruments), as an example, and more specifically, can be determined by setting a temperature rise rate of 10 ℃/min, a measuring frequency of 10Hz, and a load fluctuation to the measuring plate to 5g in a temperature range of 30 to 200 ℃.

In the case where the conductive particle dispersed 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 when the conductive particles 1 are pressed is a viscous body having a high viscosity as follows: 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 high-viscosity adhesive body having a depression 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 and are buried in the insulating resin layer 2, a high-viscosity adhesive body having a depression 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 carried out by the same measurement method as the lowest melt viscosity, and the extractable temperature was 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 japanese patent No. 6187665 (paragraph 0054).

As described above, by forming the depressions 2B (fig. 1B, fig. 2) around the conductive particles 1 exposed from the insulating resin layer 2, resistance received from the insulating resin is reduced in comparison with the case without the depressions 2B with respect to flattening of the conductive particles 1 generated when the conductive particles 1 are held between the terminals at the time of anisotropic conductive connection, and therefore the conductive particles are easily held between the terminals, whereby the conductive performance is improved and the trapping property is improved.

Further, by forming the depressions 2c (fig. 3 and 4) on the surface of the insulating resin layer 2 directly above the conductive particles 1 buried without being exposed from the insulating resin layer 2, the pressure at the time of anisotropic conductive connection is more likely to be concentrated on the conductive particles 1 and the conductive particles 1 are more likely to be held between the terminals than in the case where the depressions 2c are not present, whereby the trapping property is improved and the conduction performance is improved.

(layer thickness of insulating resin layer)

In the anisotropic conductive film of the present invention, since the amount of the resin 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 preferably 0.3 or more, more preferably 0.6 or more, and still more preferably 1.0 or more. If the La/D is less than 0.3, it may be difficult to precisely maintain a predetermined particle dispersion state or a predetermined alignment of the conductive particles 1 in 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 too large relative to the conductive particles, the conductive particles are likely to be misaligned during anisotropic conductive connection, and the trapping properties of the conductive particles in the terminals are 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 thermopolymerized composition containing a thermopolymerized compound and a thermopolymerized initiator. The thermally polymerizable composition may contain a photopolymerization initiator as needed.

When a thermal polymerization initiator and a photopolymerization initiator are used in combination, a substance that functions as both a thermal polymerizable compound and a photopolymerizable compound may be used, or a photopolymerizable compound may be contained separately from a 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, various types that react with light having different wavelengths can be contained. Thus, the wavelength used in the photocuring of the resin constituting the insulating resin layer at the time of producing the anisotropic conductive film and the photocuring of the resin for bonding 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 part of the photopolymerizable compound contained in the insulating resin layer can be photocured. By this photo-curing, the arrangement of the conductive particles 1 in the insulating resin layer 2 can be maintained or fixed, and it is expected that the short circuit is suppressed and the trapping is improved. In addition, the viscosity of the insulating resin layer in the step of producing the anisotropic conductive film can be appropriately adjusted by the photocuring.

The blending amount 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 photopolymerizable compound is too much, the pushing force required for press-fitting 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 thermally cationic polymerizable epoxy-based composition containing a thermally cationic polymerization initiator, a thermally anionic polymerizable epoxy-based composition containing a thermally anionic polymerization initiator may be used. In addition, a plurality of polymerizable compositions may be used in combination as long as they do not pose any particular problem. Examples of the combination include a combination of a thermal cationic polymerizable composition and a thermal 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 and a polyfunctional (meth) acrylate monomer having two or more functional groups 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.

When the amount of the thermal radical polymerization initiator used is too small, curing is poor, and when it is too large, the product life is 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 resins, bisphenol F type epoxy resins, phenol resin type epoxy resins, modified epoxy resins thereof, alicyclic epoxy resins, and the like, and 2 or more of these may be used in combination. In addition, an oxetane compound may be used in combination with the epoxy compound.

As the thermal cationic polymerization initiator, those known as thermal cationic polymerization initiators for epoxy compounds can be used, and for example, iodonium salts, sulfonium salts, phosphonium salts, and ferrocene which generate acids by heat can be used, and particularly, aromatic sulfonium salts showing good potential for temperature can be preferably used.

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

The heat-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 these resins can be used in combination. Among them, phenoxy resins are preferably used from the viewpoint of film-forming properties, processability, and connection reliability. The weight average molecular weight is preferably 10000 or more. Examples of the silane coupling agent include epoxy silane coupling agents and acrylic silane coupling agents. These silane coupling agents are mainly alkoxysilane derivatives.

The thermally polymerizable 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 1000nm in particle diameter, and the amount of the insulating filler blended is preferably 5 to 50 parts by mass per 100 parts by mass of a thermally polymerizable compound (and a photopolymerizable compound) such as an epoxy compound.

Further, a filler, a softening agent, an accelerator, an age resistor, a colorant (pigment, dye), an organic solvent, an ion-capturing agent, and the like, which are different from the insulating filler, may be contained.

< 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 can be evaluated by 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) >

When the number density of the conductive particles in the anisotropic conductive film of the present invention is too small in a plan view of the film, the on-resistance value may increase due to a decrease in the number of trapped particles, and therefore the lower limit is 6000 particles/mm²Above, preferably 7500 pieces/mm²The 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 fear that the substrate is deformed when it is made 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 connection²Preferably 30000 pieces/mm²The following. Here, the number density of the conductive particles may be obtained by measuring an observation image with image analysis software (WinROOF, ltd., etc.) in addition to the metal microscope observation. The observation method or the measurement method is not limited to the above method.

The number of the conductive particles isThe density measurement region is preferably a rectangular region having 1 side of 100 μm or more in a plurality of positions (preferably 5 or more, more preferably 10 or more) arbitrarily set so that the total area of the measurement region is 2mm²The above. The size and number of each region may be appropriately adjusted according to the state of the number density. As an example of the case where the number density is large for the fine pitch application, the area of the region (2 mm) of 100. mu. m.times.100. mu.m arbitrarily selected from the anisotropic conductive film 10A at 200 is the region²) The "number density of conductive particles in a plan view" in the above formula can be obtained by measuring the number density using an observation image obtained by a metal microscope or the like and averaging the number densities. In a connection target having an inter-bump gap of 50 μm or less and an L/S (line/gap) 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 dispersed 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 preferred from the viewpoint of capturing stability. Here, the positional alignment of the conductive particles 1 in the film thickness direction is not limited to the alignment at a single depth in the film thickness direction, and includes a mode in which the conductive particles are present at the interface of the front surface and the back surface of the insulating resin layer 2 or in the vicinity thereof.

In addition, from the viewpoint of suppressing short-circuiting, it is preferable that the conductive particles 1 are regularly arranged under the film in a plan view. The arrangement is not particularly limited, since it depends on the layout of the terminals and bumps. For example, as shown in fig. 1A, a square lattice arrangement may be provided under the film in a plan view. Examples of the regular arrangement of the conductive particles include a lattice arrangement such as a rectangular lattice, an orthorhombic lattice, a 6-square lattice, and a 3-corner lattice. It is also possible to combine a plurality of differently shaped lattices. Further, the particle rows in which the conductive particles are linearly arranged at a predetermined interval may be arranged at a predetermined interval. By forming the conductive particles 1 in a lattice-like and irregular arrangement without contacting 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 order to achieve both the trapping stability and the short circuit suppression, it is more preferable that the conductive particles are regularly arranged in a planar view of the film and aligned in the thickness direction of the film.

On the other hand, when the gap between the terminals of the electronic components to be connected is large and short-circuiting is difficult to occur, the conductive particles can be randomly dispersed without being regularly arranged. In the case of dispersion, it is also preferable that the conductive particles are arranged in a non-contact manner (the conductive particles are independently present in a non-contact manner) in the thin film in a plan view. As an example of the terminal layout, 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 regularly arranged, the lattice axis or the arrangement axis thereof 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, or the like. For example, in the case of forming 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 by the lattice axis a and the longitudinal direction (transverse direction of the film) of the terminal 200 connected by the anisotropic conductive film 10A 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 depending on the size of the terminal connected by the anisotropic conductive film or the terminal pitch. In general, from the viewpoint of preventing the occurrence of short circuits, the lower limit of the distance between the nearest neighboring particles (i.e., the distance between the nearest neighboring particles) is preferably 50% or more or 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 is satisfied, and for example, is preferably 30 μm or less, which is a preferred maximum diameter of the average particle diameter D of the conductive particles, or is preferably 10 times or less of the average particle diameter D when the average particle diameter D is small.

The area occupancy ratio of the conductive particles of the anisotropic conductive film of the present invention in a plan view is an index of a thrust force required for the pressing jig to thermally press-bond the anisotropic conductive film to the electronic component. If the area occupancy is too large, the thrust force increases, and this causes deformation when the substrate is a material that is easily deformed such as plastic. Therefore, the upper limit of the area occupancy of the conductive particles is preferably 30% or less, more preferably 26% or less, and still more preferably 23% or less. When the area occupancy is too small, the fine pitch may not be accommodated, and therefore, the area occupancy 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 surface areas of 1 conductive particle (. mu.m)²)]×10^-6}×100

Here, as described in paragraph 0052, it is preferable to arbitrarily set a plurality of (preferably 5 or more, more preferably 10 or more) rectangular regions with 1 side of 100 μm or more, and to set the total area of the measurement regions to 2mm²The above. The size and number of each region may be appropriately adjusted according to the state of the number density.

< position of conductive particle in thickness direction of insulating resin layer >

In the anisotropic conductive film of the present invention, as described above, the conductive particles may be exposed from the insulating resin layer 2 or buried in the insulating resin layer 2 without being exposed at the positions in the thickness direction of the insulating resin layer 2, but the ratio [ (Lb/D) × 100] (buried ratio, hereinafter) of the distance (hereinafter referred to as buried amount) Lb from the tangent plane 2p at the central portion between the adjacent conductive particles at the surface 2a of the insulating resin layer where the recesses 2b and 2c are formed and the buried amount Lb to the particle diameter D of the conductive particles 1 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 to 105% or less, the amount of resin of the insulating resin layer that acts to unnecessarily flow the conductive particles between the terminals at the time of anisotropic conductive connection can be reduced.

In the present invention, the numerical value of the embedding rate means that the numerical value of the embedding rate (Lb/D) 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 the numerical value of the embedding rate (Lb/D). Therefore, an embedding rate of 60% or more and 105% or less means that an embedding rate of 60% or more and 105% or less of the total number of conductive particles contained in the anisotropic conductive film is 80% or more, preferably 90% or more, and more preferably 96% or more. By making the embedding rate (Lb/D) of all the conductive particles uniform in this way, the load of pressing is uniformly applied to the conductive particles, and therefore the state of trapping of the conductive particles in the terminal is good, and the stability of conduction is improved.

The embedding rate can be adjusted to 30mm by optionally extracting 10 or more parts of the anisotropic conductive film²The above-mentioned area is obtained by observing a part of the cross section of the thin film with an SEM image 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 embedding rate can be measured by adjusting the focal point in the area view image, and can be obtained for a certain number of the images. Alternatively, a laser type inductive displacement sensor (manufactured by KEYENCE corporation, etc.) may be used for measuring the embedding rate.

< modification of Anisotropic conductive film >

(No. 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 obtained by laminating a 2 nd insulating resin layer 4 (which functions as an insulating adhesive layer) having a lower minimum melt viscosity than the edge resin layer 2 on the surface of the conductive particle dispersed layer 3 on the side holding the conductive particles 1 (in other words, the surface of the insulating resin layer 2 on which the recesses 2c are formed). As in the anisotropic conductive film 10F shown in fig. 6, the 2 nd insulating resin layer 4 (which functions 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 dispersed layer 3 on the side where the conductive particles 1 are not held (in other words, the surface of the insulating resin layer 2 on which the depressions 2c are not formed). By laminating the 2 nd insulating resin layer 4, when an electronic component is anisotropically and electrically connected using an anisotropic conductive film, a space formed by an electrode or a bump of the electronic component can be filled, and adhesiveness can be improved. In the case of laminating the 2 nd insulating resin layer 4, the 2 nd insulating resin layer 4 is preferably positioned on the side of the electronic component such as an IC chip pressed by a tool (in other words, the insulating resin layer 2 is positioned on the side of the electronic component such as a substrate placed on a table) regardless of whether the 2 nd insulating resin layer 4 is positioned on the surface on which the recesses 2c are formed. This can prevent unnecessary movement of the conductive particles, and can improve the trapping property.

The difference in the lowest melt viscosity between the insulating resin layer 2 and the 2 nd insulating resin layer 4 is larger, and the space formed by the electrodes or bumps of the electronic component is filled with the 2 nd insulating resin layer 4 more easily, and an effect of improving the adhesiveness between the electronic components can be expected. Further, the amount of movement of the insulating resin layer 2 in the conductive particle dispersed layer 3 is relatively smaller as the difference is larger, and therefore, the trapping property of the conductive particles in the terminal is easily improved. Practically, the ratio of the lowest melt viscosity of the insulating resin layer 2 to the 2 nd insulating resin layer 4 (i.e., [ lowest melt viscosity of the insulating resin layer 2 ]/[ lowest 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, resin may overflow or block when the long anisotropic conductive film is formed into a wound body, and therefore, it is practically preferable to be 15 or less. The preferred minimum melt viscosity of the insulating resin layer 4 of the 2 nd layer can be determined by referring to the specification of japanese patent No. 6187665 (paragraph 0091).

The 2 nd 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 thickness of the 2 nd insulating resin layer 4 is preferably 4 μm to 20 μm. Alternatively, the ratio is preferably 1 to 8 times the diameter of the conductive particles.

The minimum melt viscosity of the entire anisotropic conductive films 10E and 10F obtained 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. On the premise that the minimum melt viscosity of the 2 nd insulating resin layer 4 itself satisfies the minimum melt viscosity ratio, it is preferably 2000Pa · s or less, and more preferably 100 to 2000Pa · s.

(No. 3 insulating resin layer)

The 3 rd insulating resin layer can 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 can 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, as in the case of the 2 nd insulating resin layer.

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 obtained 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 following steps: and a step of forming a conductive particle dispersed layer by pressing conductive particles into the insulating resin layer. Preferred embodiments of this step include the following: a method of forming a conductive particle dispersion layer by holding conductive particles in a predetermined arrangement on the surface of an insulating resin layer and pressing the conductive particles into the insulating resin layer with a flat plate or a roller; or a method in which conductive particles are filled in a transfer mold and transferred onto an insulating resin layer, thereby holding the conductive particles in a predetermined arrangement on the surface of the insulating resin layer. Further, the following modes are also listed: a mode in which conductive particles are directly dispersed and held in the insulating resin layer 2; or a method in which the conductive particles 1 are attached to a biaxially stretchable film in a single layer, 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 the method of forming the conductive particle dispersed layer by pressing the 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 dispersed layer has a depression with respect to the tangent plane of the insulating resin layer at the center portion between adjacent conductive particles.

In the case of producing an anisotropic conductive film having an embedding rate of more than 100%, the film may be pressed by a pressing plate so as to have projections corresponding to the arrangement of the conductive particles.

In the case where the conductive particles 1 are held in the insulating resin layer 2 by using a transfer mold, for example, a transfer mold in which an opening is formed by a known opening forming method such as a photolithography method with respect to an inorganic material such as silicon, various ceramics, glass, or metal such as stainless steel, or an organic material such as various resins, and a printing method is applied is used as the transfer mold. The transfer mold may have a plate shape, a roll shape, or the like. It should be noted that the present invention is not limited to the above method.

Further, a 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 into which the conductive particles are pressed, the surface being on the side into which the conductive particles are pressed, or the opposite surface 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 preferably 5m or more. It can also be determined by referring to the description of Japanese patent No. 6187665 (paragraph 0103). In addition, when the anisotropic conductive film is practically used, it is practical to wind the anisotropic conductive film around a reel to form a wound body. However, when the resin viscosity (that is, the viscosity substantially proportional to the minimum melt viscosity of the film) is too low in the case of producing a wound body as described above, problems such as running-out and blocking may occur when the connection is continuously performed. Therefore, the minimum melt viscosity of the anisotropic conductive film is preferably 200Pa · s or more. This is the same even if the 2 nd insulating resin layer or the 3 rd insulating resin layer is laminated.

< method of Using Anisotropic conductive film >

The anisotropic conductive film of the present invention can be preferably used particularly when the 1 st electronic component (the side heated by a tool) is a highly rigid component such as an IC chip or an IC module (for example, a semiconductor element made of a wafer belonging to a general IC chip) or the 2 nd electronic component (the side placed on a stage) is a flexible material such as a plastic substrate. It is not excluded that the anisotropic conductive connection is performed by a combination including 1 st electronic components such as a semiconductor device, an IC chip, an IC module, and an FPC, and 2 nd electronic components such as an FPC, a glass substrate, a plastic substrate, a rigid substrate, and a ceramic substrate. In addition, IC chips or wafers can be stacked and multilayered using the anisotropic conductive film of the present invention. In addition, the electronic parts connected by the anisotropic conductive film of the present invention are not necessarily limited to the above electronic parts. Can be used for various electronic parts which are diversified 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. The present invention particularly exerts its effect when a COP structure is produced in which the 1 st electronic component is an IC chip and the 2 nd electronic component is a plastic substrate. Therefore, the present invention also includes "a connection structure in which a 1 st electronic component and a 2 nd electronic component are anisotropically and electrically connected to each other through the anisotropic conductive film of the present invention" and "a method for producing a connection structure in which a 1 st electronic component and a 2 nd electronic component are anisotropically and electrically connected to each other through the anisotropic conductive film of the present invention".

As a connection method of an electronic part using the anisotropic conductive film, in the case where the anisotropic conductive film is composed of a single layer of the conductive particle dispersed layer 3, it can be prepared by: for the 2 nd electronic components such as various substrates, the 1 st electronic components such as IC chips are stacked on the surface of the anisotropic conductive film to be temporarily bonded from the side where the conductive particles 1 are embedded in the surface of the anisotropic conductive film, and the 1 st electronic components are thermocompression bonded. When the insulating resin layer of the anisotropic conductive film contains not only a thermal polymerization initiator and a thermal polymerizable compound but also a photopolymerization initiator and a 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 a minimum. In addition, the side in which the conductive particles are not embedded may be temporarily attached to the 2 nd electronic component for use. Note that, instead of the 2 nd electronic component, the 1 st electronic component may be temporarily attached with an anisotropic conductive film and then aligned and connected.

In the case where the anisotropic conductive film is formed of a laminate of the conductive particle dispersed layer 3 and the 2 nd insulating resin layer 4 (functioning as an insulating adhesive layer), the conductive particle dispersed layer 3 is temporarily bonded and temporarily pressure-bonded to the 2 nd electronic component such as various substrates, and the 1 st electronic component such as an IC chip is placed in alignment with the 2 nd insulating resin layer 4 side of the anisotropic conductive film which is temporarily pressure-bonded, and is subjected to thermocompression bonding. The 2 nd insulating resin layer 4 side of the anisotropic conductive film can be temporarily attached to the 1 st electronic component. Alternatively, the conductive particle dispersed layer 3 side may be temporarily attached to the 1 st electronic component for use.

Examples

The present invention will be described in detail 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 an insulating resin layer, a 2 nd insulating resin layer and an insulating adhesive layer were prepared in the blend ratios shown in table 1. The lowest melt viscosity of the resulting composition was determined by the following method: a measuring plate having a diameter of 8mm was used with a measuring pressure of 5g kept constant by a rotary rheometer (TA Instruments Co., Ltd.), and a temperature rise rate of 10 ℃/min, a measuring frequency of 10Hz, and a load fluctuation to the measuring plate of 5g were set within a temperature range of 30 to 200 ℃. The results obtained are shown in table 1. The resin compositions for use in the invention of the present application include blend B, blend C and blend D. 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) manufactured by waterlogging chemical industry were prepared. Here, the 20% compression modulus of elasticity and the compression recovery were measured as follows using a micro compression tester (Fischer scope H-100, manufactured by Fischer Co., Ltd.).

<20% compression modulus of elasticity >

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

< compression recovery ratio >

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

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

The

conductive particles

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

(3) Formation of insulating resin layer, No. 2 insulating resin layer and insulating adhesive layer

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

[ Table 1]

[ Table 2]

(4) Production of resin transfer template

The mold was prepared so 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 prepared such that the convex pattern of the mold was square lattice-aligned, the pitch of the convex portions on the lattice axis was 2 times the average conductive particle diameter, and the angle θ formed by the lattice axis and the transverse direction of the anisotropic conductive film was 15 °, and a known pellet of a transparent resin was poured into the mold in a molten state, cooled and solidified, thereby forming a resin transfer template having an alignment pattern shown in fig. 1A as depressions.

(5) Production of anisotropic conductive film

The conductive particles shown in table 2 were filled in the depressions of a resin mold having depressions whose number corresponds to the number density of the conductive particles shown in table 3, and the insulating resin layer was covered thereon and then pressed at 60 ℃ and 0.5MPa to bond them. 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., 0.5MPa), thereby producing an anisotropic conductive film comprising a single layer of a conductive particle dispersed layer (examples 1 to 5, comparative example 1, and reference example 1). The embedded state of the conductive particles is controlled by the press-in condition (mainly pressure condition and temperature condition).

Further, a 2 nd insulating resin layer was laminated on the similarly prepared conductive particle dispersed layer to prepare a two-layer type anisotropic conductive film (examples 6 and 7). Further, a 3-layer anisotropic conductive film was produced by laminating an insulating adhesive layer having adhesiveness on the conductive particle dispersed layer side of the two-layer anisotropic conductive film produced in the same manner (example 8).

(6) Evaluation of

With respect to the anisotropic conductive films of the examples and comparative examples produced in (5), (a) initial on resistance, (b) on reliability, (c) indentation, and (d) particle trapping property were measured or evaluated as follows. The results are shown in table 3.

(a) Initial on-resistance

The anisotropic conductive films of examples and comparative examples were sandwiched between an IC for evaluation of conduction characteristics and a plastic substrate, heated and pressurized (180 ℃, 60MPa, 5 seconds) to obtain respective connectors for evaluation, and the on-resistance of the obtained connectors for evaluation was measured. The initial on-resistance is preferably 2 Ω or less in practical use.

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

IC for evaluating conduction characteristics

The external form is 1.8 multiplied by 20.0mm

Thickness of 0.5mm

The size of the bumps is 30 multiplied by 85 mu m, the distance between the bumps is 50 mu m, and the height of the bumps is 15 mu m

Plastic substrate (ITO wiring)

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

The external form is 30 multiplied by 50mm

Thickness of 0.5mm

And an electrode ITO wiring.

(b) Conduction reliability

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

(c) Indentation

The evaluation connection produced in (a) was observed from the plastic substrate side with a metal microscope, and it was confirmed whether or not an indentation was observed in the center of the bump end. The observed cases were evaluated as passed (good), and the cases not observed were evaluated as failed (bad).

(d) Particle trapping property

Using an evaluation IC for particle capture, 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 heating and pressing (180 ℃, 60MPa, 5 seconds) were performed, and the number of captured conductive particles was measured in 100 regions of 6 μm × 66.6 μm where the bumps of the evaluation IC and the terminals of the substrate were overlapped, to obtain the lowest number of captured conductive particles, and evaluation was performed according to the following criteria. In practice, the B value is preferably equal to or higher than the B value.

IC for evaluation of particle trapping Property

The external form is 1.6 multiplied by 29.8mm

Thickness of 0.3mm

Bump size 12X 66.6 μm, bump pitch 22 μm (L/S =12 μm/10 μm), bump height 12 μm

Evaluation criteria for particle Capacity

A5 or more

More than B3 and less than 5

C is less than 3.

[ Table 3]

(examination)

From the results shown in table 3, the anisotropic conductive films of examples 1 to 8 satisfying the following conditions (1) to (5) show preferable results at a level not lower than a level at which there is no problem in practical use, with respect to the characteristics of (a) initial on resistance, (b) on reliability, (c) indentation, and (d) particle trapping property:

< Condition (1) >

< Condition (2) >

The conductive particles have a compression recovery rate of 40% to 80%;

< Condition (3) >

The average particle diameter of the conductive particles is 1-30 [ mu ] m;

< 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 "on reliability". There are also problems with "indentation". The anisotropic conductive film of reference example 1 slightly deviated downward from the numerical ranges of conditions (1) and (2) was slightly higher in initial on-resistance and on-reliability than the anisotropic conductive films of examples 1 to 8, but was not at a level that caused practical problems. However, considering the variation of the connection conditions during the production, it is preferable that the resistance value in the initial on-resistance or on-reliability is 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 each having a specific numerical value range in each of the 20% compressive modulus of elasticity, the compressive recovery rate, and the average particle diameter are used, and as the insulating resin layer holding such conductive particles, an insulating resin layer 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 to be within a specific range. Therefore, when an electronic component having bumps, such as an image display element or a driving IC chip, is anisotropically and electrically connected to a flexible plastic substrate on which electrodes and wirings are formed by the anisotropic conductive film of the present invention, cracks are not generated in the wirings of the plastic substrate, and indentations showing good anisotropic conductive connection can be generated, and good evaluation of conduction reliability can be obtained in the case of anisotropic conductive connection. Therefore, the anisotropic conductive film of the present invention is useful for anisotropic conductive connection of an electronic component (particularly, an IC chip) to not only a glass substrate but also a plastic substrate.

Description of the marks

1 conductive particle

1a conductive particle top

2 insulating resin layer

2a surface of insulating resin layer

2b concave

2c concave

2p tangent plane

3 conductive particle dispersed layer

4 nd 2 nd insulating resin layer

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

200 terminal

Lattice axis of arrangement of A conductive particles

D average particle diameter of conductive particles

Thickness of La insulating resin layer

Lb embedding amount (distance between the deepest part of a conductive particle and a tangent plane at the center part between adjacent conductive particles)

Lc exposed diameter

The angle formed by the longitudinal direction of the theta terminal and 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) >

The conductive particles have a compression recovery rate of 40% to 80%;

< Condition (3) >

The average particle diameter of the conductive particles is 1-30 [ mu ] m;

< Condition (4) >

< Condition (5) >

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

3. The anisotropic conductive film of claim 1 or 2, wherein the conductive particles are disposed in the insulating resin layer in a non-contact manner.

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

5. The anisotropic conductive film according to any one of claims 1 to 4, wherein a distance between nearest neighboring conductive particles of the conductive particles is a longer distance of 50% or more or 0.2 μm or more of an average particle diameter of the conductive particles.

6. The anisotropic conductive film according to any of claims 1 to 5, wherein a 2 nd insulating resin layer is laminated on a surface of the conductive particle dispersed layer on a side where the conductive particles are held.

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

8. The anisotropic conductive film of claim 6 or 7, wherein the lowest melt viscosity of the 2 nd insulating resin layer is lower than the lowest melt viscosity of the insulating resin layer.

9. The anisotropic conductive film of any of claims 6 to 8, wherein the minimum melt viscosity ratio of the insulating resin layer to the 2 nd insulating resin layer is 2 or more.

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

11. The production method according to claim 10, wherein the conductive particle dispersed layer is formed by holding conductive particles in a predetermined arrangement on the surface of the insulating resin layer and pressing the conductive particles into the insulating resin layer with a flat plate or a roller.

12. The production method according to claim 11, wherein the conductive particles are filled in a transfer mold and transferred to the insulating resin layer, whereby the conductive particles are held on the surface of the insulating resin layer in a predetermined arrangement.

13. A connection structure obtained by anisotropically and electrically connecting a 1 st electronic component and a 2 nd electronic component through the anisotropic conductive film according to any one of claims 1 to 9.

14. The connection structure according to claim 13, wherein the 1 st electronic component is an IC chip or an IC module, and the 2 nd electronic component is a plastic substrate.

15. A method for producing a connection structure, wherein a 1 st electronic component and a 2 nd electronic component are anisotropically conductively connected through the anisotropic conductive film according to any one of claims 1 to 9.