Anisotropic Conductive Film, Connection Structure, and Method for Manufacturing the Same

Abstract

The present application relates to an anisotropic conductive film, a connection structure, and a method for manufacturing the same. The anisotropic conductive film of the present application is an anisotropic conductive film in which an intermediate layer is sandwiched between an insulating base layer and an adhesive layer, and at least one of the conductive particles is held in the adhesive layer or the intermediate layer in a thermopolymerizable manner. The conductive particles are embedded in the intermediate layer or the adhesive layer, and the melt viscosities of the intermediate layer and the adhesive layer are each higher than the melt viscosity of the insulating base layer. When the anisotropic conductive film is viewed from above, the conductive particles exist independently of each other, and the elastic modulus of the entire anisotropic conductive film after thermopolymerization is higher than 1800 MPa at 100 °C.

Description

[0001] This application is a divisional application of a Chinese patent application with an application date of July 11, 2016, an application number of 201680037691.X, and an invention title of "Anisotropic Conductive Film and Connection Structure". Technical Field

[0002] The present invention relates to an anisotropic conductive film and a connection structure. Background Art

[0003] In order to mount electronic components such as IC chips on a transparent substrate for display elements, anisotropic conductive films are widely used. In recent years, from the viewpoint of applicability to high mounting density, in order to improve the conductive particle capture efficiency, connection reliability, and reduce the short-circuit incidence rate, an anisotropic conductive film 60 having a two-layer structure in which an insulating resin layer 61 having a relatively thick layer thickness and a conductive particle-containing layer 64 having a relatively thin layer thickness in which conductive particles 63 are dispersed in an insulating adhesive 62 are laminated as shown in Figure 6 FIG. In such an anisotropic conductive film 60, when thermally pressing from the insulating resin layer 61 side during anisotropic conductive connection, in order to suppress the excessive flow of conductive particles, it has been proposed to use a photocurable resin composition as the insulating adhesive 62 of the conductive particle-containing layer 64 (Patent Document 1). In this case, in order to hold the conductive particles well, the conductive particle-containing layer 64 is pre-cured by light.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Laid-Open No. 2003-64324 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, in the case of anisotropically conducting connection between a substrate and an electronic component such as an IC chip using an anisotropic conductive film having a conductive particle-containing layer in which conductive particles are dispersed in a photocured insulating adhesive, aggregates of conductive particles are formed, so there is a problem that the risk of short circuit cannot be eliminated, and there are also problems such as a decrease in the capture property of conductive particles at the bump edge end of the electronic component, insufficient intrusion of conductive particles into the wiring and bumps, and a decrease in conduction reliability. Further, since the adhesiveness of the conductive particle-containing layer after photocuring is reduced, when the anisotropic conductive film is pre-bonded to the connection object, there is a concern about positional deviation.

[0009] An object of the present invention is to provide an anisotropic conductive film capable of suppressing the occurrence of short circuits during anisotropic conduction, not reducing the capture property of conductive particles, being able to well squeeze into the conductive particles to suppress a decrease in conduction reliability, and exhibiting good adhesiveness.

[0010] Means for Solving the Problem

[0011] The inventors of the present invention have found that by laminating an insulating base layer, an intermediate layer, and an adhesive layer to form an anisotropic conductive film, holding conductive particles in at least one of the adhesive layer and the intermediate layer and making it thermopolymerizable, and in addition, making the melt viscosities of the intermediate layer and the adhesive layer higher than the melt viscosity of the insulating base layer, and when looking down on the anisotropic conductive film, the conductive particles exist independently of each other, and the elastic modulus of the entire anisotropic conductive film after thermopolymerization is higher than a predetermined value, the object of the present invention can be achieved, and thus the present invention has been completed.

[0012] That is, the present invention provides an anisotropic conductive film which is a thermopolymerizable anisotropic conductive film having an intermediate layer sandwiched between an insulating base layer and an adhesive layer and holding conductive particles in at least one of the adhesive layer and the intermediate layer.

[0013] The melt viscosities of the intermediate layer and the adhesive layer are higher than the melt viscosity of the insulating base layer.

[0014] When looking down on the anisotropic conductive film, the conductive particles exist independently of each other.

[0015] The elastic modulus of the entire anisotropic conductive film after thermopolymerization is higher than 1800 MPa at 100 °C.

[0016] In addition, the present invention provides a connection structure in which a first electronic component is anisotropically conductively connected to a second electronic component by the above-described anisotropic conductive film.

[0017] Advantages of the Invention

[0018] The thermopolymerizable anisotropic conductive film of the present invention has a structure in which an insulating base layer, an intermediate layer, and an adhesive layer are laminated. Due to this adhesive layer, the pre-bonding property with the object to be anisotropically conductively connected is stable. In addition, conductive particles are held in at least one of the adhesive layer and the intermediate layer, and the melt viscosity of the intermediate layer and the adhesive layer is further set to be higher than that of the insulating base layer. Therefore, during anisotropic conductive connection, the conductive particles can be well squeezed in without excessive flow, ensuring good particle capture and conduction reliability. In addition, when looking at the anisotropic conductive film from above, the conductive particles exist independently of each other. Therefore, aggregation of the conductive particles in the anisotropic conductive film can be prevented, and the occurrence of short circuits during anisotropic conductive connection can be prevented. In addition, since the conductive particles exist independently, the pressing force from the device can be made uniform, and the squeezing-in of the conductive particles can be made uniform. This is also because the layer holding the conductive particles is not photocured, so the resistance to squeezing-in caused by the photocured resin is reduced. Further, the elastic modulus of the entire anisotropic conductive film after thermopolymerization is set to be higher than 1800 MPa at 100 °C. Therefore, the retention of the squeezing-in of the conductive particles after thermopolymerization can be kept within a certain range. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Figure 1 is a cross-sectional view of the anisotropic conductive film of the present invention.

[0020] Figure 2 Figure 2 is a cross-sectional view of the anisotropic conductive film of the present invention.

[0021] Figure 3 Figure 3 is a cross-sectional view of the anisotropic conductive film of the present invention.

[0022] Figure 4 Figure 4 is a cross-sectional view of the anisotropic conductive film of the present invention.

[0023] Figure 5 Figure 5 is a cross-sectional view of the anisotropic conductive film of the present invention.

[0024] Figure 6 Figure 6 is a cross-sectional view of the anisotropic conductive film of the prior art (Comparative Example 1).

[0025] Figure 7 Figure 7 is a cross-sectional view of the anisotropic conductive film of Comparative Example 2.

[0026] Figure 8 Figure 8 is a cross-sectional view of the anisotropic conductive film of Comparative Example 3.​​​​​​​​​​​​​​​​

[0027] Figure 9 Figure 9 Cross-sectional view of the anisotropic conductive film of Comparative Example 4.

[0028] Symbol Explanation

[0029] 1, 71, 81, 91 Insulating base layer

[0030] 2, 82, 92 Intermediate layer

[0031] 3, 73, 83, 93 Adhesive layer

[0032] 4 Conductive particles

[0033] 5 Insulating filler

[0034] 10, 60, 70, 80, 90 Anisotropic conductive film

[0035] 61 Insulating resin layer

[0036] 62 Insulating adhesive

[0037] 63 Conductive particles

[0038] 64 Conductive particle-containing layer Detailed Description of the Invention

[0039] Hereinafter, an example of the anisotropic conductive film of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the drawings, the same reference numerals denote the same or equivalent components.

[0040] <<Overall Structure of the Anisotropic Conductive Film>>

[0041] Figure 1 Cross-sectional view of the anisotropic conductive film 10 of an embodiment of the present invention. The anisotropic conductive film 10 has a structure in which an insulating base layer 1, an intermediate layer 2, and an adhesive layer 3 are laminated. At least one of them is thermopolymerizable. Preferably, all three layers are thermopolymerizable.

[0042] Figure 1 In the case of, the conductive particles 4 are held between the intermediate layer 2 and the adhesive layer 3, but the conductive particles 4 can be held in any one of the insulating base layer 1, the intermediate layer 2, and the adhesive layer 3. For example, Figure 2 In the case of, the conductive particles 4 are embedded in the adhesive layer 3, Figure 3 In the case of, the conductive particles 4 are held between the insulating base layer 1 and the intermediate layer 2, Figure 4 In the case of, the conductive particles 4 are embedded in the intermediate layer 2. In addition, Figure 5 In the case of, compared with Figure 1 ​​Similarly, the conductive particles 4 are held between the intermediate layer 2 and the adhesive layer 3. Further, in order to adjust the melt viscosity, an insulating filler 5 is contained in the intermediate layer 2. It should be noted that the insulating filler 5 may also be present in other layers, and may be contained in two or more layers or in all three layers.

[0043] In the present invention, as described above, at least one of the insulating base layer 1, the intermediate layer 2, and the adhesive layer 3 exhibits thermopolymerizability. In this case, the layer holding the conductive particles 4 is preferably thermopolymerizable. This is to prevent the undesired flow of the conductive particles 4. Therefore, these layers are preferably composed of a thermopolymerizable composition containing a thermopolymerizable compound and a thermopolymerization initiator. Further, in order to adjust the melt viscosity, such a thermopolymerizable composition may contain insulating fillers such as silica powder and alumina powder. Further, it may also contain fillers, softeners, accelerators, anti-aging agents, colorants (pigments, dyes), organic solvents, ion scavengers, etc.

[0044] In the anisotropic conductive film 10 of the present invention, the melt viscosities of the intermediate layer 2 and the adhesive layer 3 are higher than the melt viscosity of the insulating base layer 1. Preferably, the order is adhesive layer 3 > intermediate layer 2 > insulating base layer 1. Thereby, the conductive particles 4 can be well squeezed in during anisotropic conductive connection. In addition, by providing the intermediate layer 2 with a relatively high melt viscosity, it is easy to balance the squeezing of the conductive particles 4 from the pressing tool and the suppression of resin flow. Specifically, the melt viscosity of the insulating base layer 1 is preferably 3000 mPa·s or less, more preferably 1000 mPa·s or less at 80°C. The melt viscosity of the intermediate layer 2 is preferably 1000 to 20000 mPa·s, more preferably 3000 to 15000 mPa·s at 80°C. The melt viscosity of the adhesive layer 3 is preferably 1000 to 20000 mPa·s, more preferably 3000 to 15000 mPa·s at 80°C. It should be noted that the melt viscosity can be measured using, for example, a rotational rheometer (TA Instruments) under the conditions of a heating rate of 10°C / minute, a constant measurement pressure of 5 g, and a measurement plate diameter of 8 mm.

[0045] In addition, in the anisotropic conductive film 10 of the present invention, when the anisotropic conductive film 10 is viewed from above, the conductive particles 4 exist independently of each other. Here, "existing independently of each other" means a state in which the conductive particles 4 do not aggregate, are not in contact with each other, and do not overlap in the film thickness direction. The degree of "non-contact" is such that the distance between the centers of adjacent conductive particles 4 is preferably 1.5 to 50 times the average particle diameter, more preferably 2 to 30 times. In addition, the state of "not overlapping in the film thickness direction" means that when the anisotropic conductive film is viewed from above, the conductive particles do not overlap with other conductive particles.

[0046] It should be noted that the proportion of "independently existing conductive particles" relative to all conductive particles is preferably 95% or more, more preferably 96% or more, and still more preferably greater than 99%. The measurement of this proportion can be carried out by measuring from the planar field images of a metallurgical microscope or an electron microscope. In addition, it can also be carried out using a known image analysis measurement system (for example, WinROOF of Mitani Sangyo Co., Ltd.).

[0047] Regarding the conductive particles 4, as described above, they exist independently when the anisotropic conductive film 10 is viewed from above. In order to achieve uniform light transmission in the entire anisotropic conductive film 10, a regular arrangement is preferred. As a regular arrangement, a lattice shape such as a hexagonal lattice, a rhombic lattice, a square lattice, a rectangular lattice, or a parallelogram lattice is preferred. In addition, it may not be a lattice shape, but a shape formed by linearly arranging side by side in a line. In this case, it is preferred that the lines exist in a slanting manner with respect to the width direction of the film. The distance between the lines is not particularly limited and can be regular or irregular, but practically a regular pattern is preferred.

[0048] In addition, in order to suppress the risk of short circuit occurrence, the area occupancy rate of the conductive particles 4 when the anisotropic conductive film 10 is viewed from above is preferably 50% or less, more preferably 40% or less. Furthermore, in order to suppress the reduction of the number of particles captured on the terminals during connection and the increase of the conduction resistance value, it is preferably 5% or more, more preferably 10% or more.

[0049] It should be noted that in the case where the conductive particles are regularly arranged while taking into account the layout of the terminals, the reduction of the number of particles captured on the terminals can be suppressed to a minimum. Therefore, as long as the area occupancy rate is 0.2% or more, there is no problem in practical use. In order to obtain stable connection, it is preferably 5% or more, more preferably 10% or more. Here, the regular arrangement that takes into account the layout of the terminals means, for example, in the long side direction of a rectangular terminal (in the case of COG connection of a normal IC, it is the width direction of the film), the outer tangent of the conductive particles is not on a straight line, and the lattice-like arrangement is configured in such a way that the outer tangent passes through the conductive particles. In other words, it can also be called a meandering state. By setting it like this, in the case where the conductive particles are present at the edge part of the terminal where it is difficult to capture, the minimum number of conductive particles can be captured. When the outer tangent of the conductive particles is on a straight line, that is, when they coincide, the conductive particles present at the edge part of the terminal may not be captured in the same way. The above is an example of the configuration to avoid such a situation. The conductive particles arranged regularly like this are preferably more than 99% of the total number of conductive particles.

[0050] The elastic modulus of the anisotropic conductive film 10 of the present invention at 100 °C after thermal polymerization is higher than 1800 MPa, preferably 2100 MPa or more. This is because if the elastic modulus is higher than 1800 MPa, the retention of the inserted conductive particles 4 becomes good. It should be noted that in order to suppress the decrease in the toughness (flexibility) of the anisotropic conductive film 10 and the decrease in the adhesion between substrates, the elastic modulus is preferably 3000 MPa or less, and more preferably 2500 MPa or less. Here, "after thermal polymerization" can be defined by the reaction rate of the thermopolymerizable compound. Specifically, an infrared absorption spectrum of the epoxy ring or unsaturated group of the thermopolymerizable compound is measured using an infrared spectrophotometer (e.g., FT / IR-4100, JASCO Corporation), and the attenuation amount (%) of the absorption wavelength of the epoxy ring before and after the reaction (connection) or the attenuation amount (%) of the absorption wavelength of the unsaturated group is obtained. This attenuation amount (%) is used as the reaction rate, and after this reaction rate reaches 80% or more, it is defined as "after thermal polymerization". It should be noted that the elastic modulus can be measured based on JIS K7244-4.

[0051] In addition, the glass transition temperature of the anisotropic conductive film 10 of the present invention after thermal polymerization is preferably higher than 145 °C, more preferably higher than 160 °C. This is because if the glass transition temperature is higher than 145 °C, the retention force after the insertion of the conductive particles becomes good, and it is easy to maintain the adhesion between substrates. In addition, as long as there is no significant reduction in the bonding strength after connection, there is no need to set an upper limit on the glass transition temperature, but from the viewpoint of processability, it is usually 220 °C or less, preferably 168 °C or less.

[0052] <Insulating base layer 1>

[0053] The insulating base layer 1 is a layer of a thermopolymerizable composition containing a thermopolymerizable compound and a thermal polymerization initiator. Optionally, a photoinitiator may be contained. Examples of the thermopolymerizable composition include a thermoradical polymerizable acrylate-based composition containing a (meth)acrylate compound and a thermal radical polymerization initiator, a thermocationic polymerizable epoxy-based composition containing an epoxy compound and a thermal cationic polymerization initiator, and the like.

[0054] Here, as the (meth)acrylate compound, conventionally known thermopolymerizable (meth)acrylate monomers can be used. For example, monofunctional (meth)acrylate-based monomers and polyfunctional (meth)acrylate-based monomers having two or more functional groups can be used. In the present invention, in order to thermally cure an intermediate layer or the like during anisotropic conductive connection, it is preferable to use a polyfunctional (meth)acrylate-based monomer in at least a part of the (meth)acrylate-based monomers. Here, (meth)acrylate includes acrylate and methacrylate.

[0055] Examples of the thermal free radical polymerization initiator include organic peroxides, azo compounds, etc. In particular, organic peroxides that do not generate nitrogen, which is the cause of bubble formation, can be preferably used.

[0056] If the amount of the thermal free radical polymerization initiator used is too small, curing will be poor, and if it is too large, the product life will be reduced. Therefore, 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 (meth)acrylate compound.

[0057] Examples of the epoxy compound include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, their modified epoxy resins, alicyclic epoxy resins, etc., and two or more of them can be used in combination. In addition to the epoxy compound, an oxetane compound can also be used in combination.

[0058] As the thermal cationic polymerization initiator, initiators known as thermal cationic polymerization initiators for epoxy compounds can be used. For example, iodonium salts, sulfonium salts, salts, ferrocene compounds, etc., which generate acid by heat, can be used. In particular, aromatic sulfonium salts that show good latency to temperature can be preferably used.

[0059] If the compounding amount of the thermal cationic polymerization initiator is too small, there is a tendency for curing to be poor, and if it is too large, there is also a tendency for the product life to be reduced. Therefore, 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.

[0060] The thermopolymerizable composition preferably contains a film-forming resin and a silane coupling agent. Examples of the film-forming resin include phenoxy resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, urethane resin, butadiene resin, polyimide resin, polyamide resin, polyolefin resin, etc., and two or more of them can be used in combination. Among them, phenoxy resin can be preferably used from the viewpoints of film-forming property, processability, and connection reliability. In addition, examples of the silane coupling agent include epoxy-based silane coupling agents, acrylic-based silane coupling agents, etc. These silane coupling agents are mainly alkoxysilane derivatives.

[0061] It should be noted that fillers, softeners, accelerators, anti-aging agents, colorants (pigments, dyes), organic solvents, ion scavengers, etc. can be compounded in the thermopolymerizable composition as needed.

[0062] The thickness of the insulating base layer 1 composed of the above thermopolymerizable composition is preferably 3 to 50 μm, more preferably 5 to 20 μm.

[0063] <Intermediate layer 2>

[0064] The intermediate layer 2 may contain the thermopolymerizable compound and the thermopolymerization initiator described for the insulating base layer 1. In such a case, the intermediate layer 2 is also a layer of a thermopolymerizable composition containing a thermopolymerizable compound and a thermopolymerization initiator, and can hold the conductive particles 4. As already described, the melt viscosity of the intermediate layer 2 is higher than that of the insulating base layer 1, so that the capture property of the conductive particles 4 can be improved.

[0065] The thickness of the intermediate layer 2 is preferably 1 to 50 μm, more preferably 2 to 20 μm, but preferably not thicker than the insulating base layer 1.

[0066] <Adhesive layer 3>

[0067] The adhesive layer 3 is a layer for imparting good adhesiveness to the anisotropic conductive film 10 even when the adhesiveness of the intermediate layer 2 is insufficient. Such an adhesive layer 3 may be composed of a layer of the same composition as the thermopolymerizable composition constituting the insulating base layer 1 and the intermediate layer 2.

[0068] The thickness of such an adhesive layer 3 is preferably 1 to 50 μm, more preferably 1 to 20 μm. It is preferably not thicker than the insulating base layer 1. The sum of the thicknesses of the adhesive layer 3 and the intermediate layer 2 preferably has a relationship of 1 to 10 times that of the insulating base layer 1.

[0069] <Conductive particles 4>

[0070] As the conductive particles 4, they can be appropriately selected and used from the conductive particles used in conventionally known anisotropic conductive films. For example, metal particles such as nickel, cobalt, silver, copper, gold, and palladium, alloy particles such as solder, and metal-coated resin particles can be mentioned. Two or more kinds can be used in combination.

[0071] As the average particle diameter of the conductive particles 4, in order to cope with unevenness in wiring height, suppress an increase in conduction resistance, and suppress the occurrence of short circuits, it is preferably 1 μm or more and 30 μm or less, more preferably 3 μm or more and 9 μm or less. The particle diameter of the conductive particles 4 can be measured using a usual particle size distribution measuring device, and its average particle diameter can also be obtained using a particle size distribution measuring device.

[0072] It should be noted that when the conductive particles 4 are metal-coated resin particles, in order to obtain good connection reliability, the particle hardness of the resin core particles (20% K value; compression elastic deformation characteristic K 20 ) is preferably 100 to 10000 kgf / mm 2 , more preferably 1000 to 7000 kgf / mm 2 .

[0073] In order to suppress the reduction in the capture efficiency of conductive particles and to suppress the occurrence of short circuits, the amount of conductive particles 4 present in the anisotropic conductive film 10 is preferably 50 or more and 100,000 or less per 1 square mm, more preferably 200 or more and 70,000 or less. The measurement of this amount can be carried out by observing the film surface with an optical microscope.

[0074] It should be noted that the amount of conductive particles 4 present in the anisotropic conductive film 10 can also be expressed on a mass basis. In this case, when the total mass of the anisotropic conductive film 10 is 100 mass parts, the amount thereof becomes preferably 1 mass part or more and 30 mass parts or less, more preferably 3 mass parts or more and 10 mass parts or less in these 100 mass parts.

[0075] <<Method for manufacturing anisotropic conductive film>>

[0076] The anisotropic conductive film of the present invention Figure 1 can be manufactured, for example, by disposing a separately formed insulating base layer on one side of an intermediate layer composed of a thermopolymerizable composition having conductive particles held on its surface, and disposing a separately formed adhesive layer on the other side of the intermediate layer, and then laminating the whole. Here, as a method for holding the conductive particles in the intermediate layer, a conventionally known method can be used. For example, the conductive particles can be held in the intermediate layer by directly dispersing the conductive particles in the intermediate layer film. Alternatively, the conductive particles can be attached in a single layer to the adhesive layer for stretching and then biaxially stretched, and the intermediate layer can be pressed against the stretched film to transfer the conductive particles to the intermediate layer, thereby holding the conductive particles in the intermediate layer. In addition, a transfer mold can be used to hold the conductive particles in the intermediate layer. An example of manufacturing the anisotropic conductive film of the present invention using a transfer mold will be described below.

[0077] Figure 1 ( Figure 5 ) The anisotropic conductive film 10 shown can be manufactured according to the following steps A to D.

[0078] First, the conductive particles are placed in the recesses of a transfer mold having a plurality of recesses (step A). Next, a thermopolymerizable composition containing a thermopolymerizable compound, a thermopolymerization initiator, and, if necessary, an insulating filler is pressed against the conductive particles in the transfer mold to form an intermediate layer having the conductive particles transferred thereon (step B). Next, a thermopolymerizable composition containing a thermopolymerizable compound and a thermopolymerization initiator is formed into a film independently of the intermediate layer to form an insulating base layer (step C), and similarly an adhesive layer is formed (step D). The adhesive layer is disposed on the conductive particle transfer surface of the intermediate layer, and the insulating base layer is disposed on the non-transfer surface of the conductive particles, and the whole is laminated, whereby Figure 1 ( Figure 5 ) the anisotropic conductive film 10 can be obtained.

[0079] By adjusting the pressing in Process B, the degree of embedding of the conductive particles into the intermediate layer can be changed. By increasing the degree of pressing, the degree of embedding of the conductive particles into the intermediate layer becomes larger, and ultimately, they can be completely embedded in the intermediate layer. Thus, anisotropic conductive films can also be manufactured. Figure 4

[0080] If an insulating base layer is disposed on the transfer surface of the conductive particles in the intermediate layer and an adhesive layer is disposed on the non-transfer surface of the conductive particles, an anisotropic conductive film 10 can be obtained. Figure 3 In addition, if the object into which the conductive particles are embedded is changed from the intermediate layer to the adhesive layer, anisotropic conductive films can be manufactured. Figure 2

[0081] (Transfer mold)

[0082] As the transfer mold used in the manufacturing method of the present invention, for example, a transfer mold having openings formed by a known opening formation method such as photolithography can be used for inorganic materials such as silicon, various ceramics, glass, stainless steel and other metals, and organic materials such as various resins. In addition, the transfer mold can take shapes such as plate-like and roll-like.

[0083] As the shape of the concave portion of the transfer mold, column shapes such as cylindrical and quadrangular prism, frustum of a cone, frustum of a pyramid, conical, quadrangular pyramid and other pyramid shapes can be exemplified.

[0084] As the arrangement of the concave portions, it can be appropriately set to a lattice shape, a staggered shape (checkerboard pattern) or the like corresponding to the arrangement adopted by the conductive particles.

[0085] Regarding the ratio of the average particle diameter of the conductive particles to the depth of the concave portion (= average particle diameter of the conductive particles / depth of the opening), considering the balance between transferability improvement and conductive particle retention, it is preferably 0.4 to 3.0, more preferably 0.5 to 1.5. It should be noted that the diameter length and depth of the concave portion of the transfer mold can be measured using a laser microscope.

[0086] Regarding the ratio of the opening diameter of the concave portion to the average particle diameter of the conductive particles (= opening diameter of the concave portion / average particle diameter of the conductive particles), considering the balance between ease of accommodation of the conductive particles, ease of extrusion of the insulating resin, etc., it is preferably 1.1 to 2.0, more preferably 1.3 to 1.8.

[0087] It should be noted that in the case where the bottom diameter of the concave portion is smaller than its opening diameter, it is preferable that the bottom diameter is 1.1 times or more and less than 2 times the conductive particle diameter, and the opening diameter is 1.3 times or more and less than 3 times the conductive particle diameter.

[0088] <<Connection structure>>

[0089] The anisotropic conductive film of the present invention can be preferably used when anisotropically conducting and connecting a first electronic component such as an IC chip, an IC module, an FPC, etc. to a second electronic component such as an FPC, a glass substrate, a rigid substrate, a ceramic substrate, etc. The connection structure thus obtained is also a part of the present invention.

[0090] As a method for connecting electronic components using an anisotropic conductive film, for example, it can be manufactured by pre-bonding the anisotropic conductive film to a second electronic component such as various substrates from the adhesive layer side, and then mounting a first electronic component such as an IC chip on the pre-bonded anisotropic conductive film and performing thermocompression bonding.

[0091] Examples

[0092] Hereinafter, the present invention will be specifically described by way of examples. It should be noted that the elastic modulus was measured based on JIS K7244-4 under the conditions of a tensile mode, a frequency of 11 Hz, a heating rate of 3 °C / minute, and a measurement temperature range of 0 to 260 °C using a dynamic viscoelasticity measuring instrument (DDV01FP-W, A&D Co., Ltd.). In addition, regarding the glass transition temperature, tanδ was calculated from the storage modulus E' and the loss modulus E" measured based on JISK7244-4, and the maximum point was taken as the glass transition temperature. The melt viscosity was measured using a rotational rheometer (TA Instruments) under the conditions of a heating rate of 10 °C / minute, a constant measurement pressure of 5 g, a measurement plate diameter of 8 mm, and a measurement temperature of 80 °C.

[0093] It should be noted that the composition of each layer of the anisotropic conductive film constituting the following examples and comparative examples is shown in Table 1, and the structure (corresponding figure), size (thickness), physical properties, and evaluation results of the anisotropic conductive film of each layer are shown in Table 2.

[0094] Example 1 ( Figure 1 Manufacture of anisotropic conductive film)

[0095] (Formation of insulating base layer)

[0096] A thermopolymerizable composition is prepared by mixing 40 parts by mass of a phenoxy resin (Nippon Steel & Sumikin Chemical Co., Ltd., YP-50), 5 parts by mass of a silica filler (Aerosil R805, Nippon Aerosil Co., Ltd.), 55 parts by mass of a liquid epoxy resin (Mitsubishi Chemical Corporation, jER828), 4 parts by mass of a thermal cationic polymerization initiator (Sansei Chemical Industry Co., Ltd., SI-60L), and 1 part by mass of a silane coupling agent (Shin-Etsu Chemical Co., Ltd., KBM-403). This composition is coated onto a PET film with a thickness of 50 μm using a bar coater and dried in an oven at 80°C for 5 minutes to form an adhesive insulating base layer with a thickness shown in Table 2 (14 μm) on the PET film. The melt viscosity of this insulating base layer is shown in Table 2.

[0097] (Formation of the intermediate layer)

[0098] On the other hand, a metal mold with an arrangement pattern of convex portions corresponding to a square lattice pattern is fabricated. A substance obtained by melting particles of a known transparent resin is poured into this metal mold and cooled and solidified to produce a resin transfer mold with concave portions in a square lattice pattern having a density shown in Table 2 (corresponding to the particle density of the conductive particles). The concave portions of this transfer mold are filled with conductive particles (Sekisui Chemical Co., Ltd., AUL703, particle size 3 μm).

[0099] Separately, another thermopolymerizable composition is prepared by mixing 40 parts by mass of a phenoxy resin (Nippon Steel & Sumikin Chemical Co., Ltd., YP-50), 30 parts by mass of a silica filler (Aerosil R805, Nippon Aerosil Co., Ltd.), 30 parts by mass of a liquid epoxy resin (Mitsubishi Chemical Corporation, jER828), 4 parts by mass of a thermal cationic polymerization initiator (Sansei Chemical Industry Co., Ltd., SI-60L), and 1 part by mass of a silane coupling agent (Shin-Etsu Chemical Co., Ltd., KBM-403). This thermopolymerizable composition is coated onto a PET film with a thickness of 50 μm and dried in an oven at 80°C for 5 minutes to form an adhesive intermediate layer with a thickness shown in Table 2 (2 μm). Using an elastic roller, this intermediate layer is pressed against the conductive particle receiving surface of the transfer mold under the conditions of a pressing temperature of 50°C and a pressing pressure of 0.5 MPa to form an intermediate layer with transferred conductive particles, and then peeled off from the transfer mold. The melt viscosity of this intermediate layer, the ratio of the independently existing conductive particles to all the conductive particles, and the conductive particle occupation area ratio are shown in Table 2.

[0100] (Formation of the adhesive layer)

[0101] Prepare a thermopolymerizable composition by mixing 50 parts by mass of a phenoxy resin (Nippon Steel & Sumikin Chemical Co., Ltd., YP-50), 20 parts by mass of a silica filler (Aerosil R805, Nippon Aerosil Co., Ltd.), 30 parts by mass of a liquid epoxy resin (Mitsubishi Chemical Corporation, jER828), 4 parts by mass of a thermal cationic polymerization initiator (Sansei Chemical Industry Co., Ltd., SI-60L), and 1 part by mass of a silane coupling agent (Shin-Etsu Chemical Co., Ltd., KBM-403). Coat this composition onto a PET film with a thickness of 50 μm using a bar coater, and dry it in an oven at 80°C for 5 minutes to form an adhesive layer with a thickness of 2 μm as shown in Table 2 on the PET film. The melt viscosity of this adhesive layer is shown in Table 2.

[0102] (Lamination of Insulating Base Layer, Intermediate Layer, and Adhesive Layer)

[0103] Align the insulating base layer with the non-transfer surface of the conductive particles of the intermediate layer, and the adhesive layer with the transfer surface of the conductive particles. Bond them under the conditions of a pressing temperature of 50°C and a pressing pressure of 0.2 MPa to manufacture Figure 1 an anisotropic conductive film. The elastic modulus and glass transition temperature of the obtained anisotropic conductive film are shown in Table 2.

[0104] Example 2 ( Figure 1 Manufacture of Anisotropic Conductive Film)

[0105] In the thermopolymerizable composition used for the adhesive layer, change the phenoxy resin from 50 parts by mass to 40 parts by mass, and change the silica filler from 20 parts by mass to 30 parts by mass. In the thermopolymerizable composition used for the intermediate layer, change the phenoxy resin from 40 parts by mass to 50 parts by mass, and change the silica filler from 30 parts by mass to 20 parts by mass. Otherwise, operate in the same manner as in Example 1 to fabricate an anisotropic conductive film. The elastic modulus and glass transition temperature of the obtained anisotropic conductive film are shown in Table 2.

[0106] Example 3 ( Figure 1 Manufacture of Anisotropic Conductive Film)

[0107] In the thermopolymerizable composition used for the intermediate layer, change the phenoxy resin from 40 parts by mass to 50 parts by mass, and change the silica filler from 30 parts by mass to 20 parts by mass. Otherwise, operate in the same manner as in Example 1 to fabricate an anisotropic conductive film. The elastic modulus and glass transition temperature of the obtained anisotropic conductive film are shown in Table 2.

[0108] Example 4 ( Figure 1 Manufacture of Anisotropic Conductive Film)

[0109] In the thermopolymerizable composition used for the adhesive layer, the phenoxy resin was changed from 50 parts by mass to 40 parts by mass, and the silica filler was changed from 20 parts by mass to 30 parts by mass. Otherwise, the operation was the same as in Example 1 to produce an anisotropic conductive film. The elastic modulus and glass transition temperature of the obtained anisotropic conductive film are shown in Table 2.

[0110] Example 5 ( Figure 1 Manufacture of anisotropic conductive film)

[0111] In the thermopolymerizable composition used for the adhesive layer, the phenoxy resin was changed from 50 parts by mass to 30 parts by mass, and the silica filler was changed from 20 parts by mass to 40 parts by mass. In the thermopolymerizable composition used for the intermediate layer, the phenoxy resin was changed from 40 parts by mass to 30 parts by mass, and the silica filler was changed from 30 parts by mass to 40 parts by mass. Otherwise, the operation was the same as in Example 1 to produce an anisotropic conductive film. The elastic modulus and glass transition temperature of the obtained anisotropic conductive film are shown in Table 2.

[0112] Example 6 ( Figure 1 Manufacture of anisotropic conductive film)

[0113] In the thermopolymerizable composition used for the insulating base layer, the phenoxy resin was changed from 40 parts by mass to 30 parts by mass, and the silica filler was changed from 5 parts by mass to 15 parts by mass. In the thermopolymerizable composition used for the intermediate layer, the phenoxy resin was changed from 40 parts by mass to 30 parts by mass, and the silica filler was changed from 30 parts by mass to 40 parts by mass. In the thermopolymerizable composition used for the adhesive layer, the phenoxy resin was changed from 50 parts by mass to 30 parts by mass, and the silica filler was changed from 20 parts by mass to 40 parts by mass. Otherwise, the operation was the same as in Example 1 to produce an anisotropic conductive film.

[0114] Example 7 ( Figure 2 Manufacture of anisotropic conductive film)

[0115] Instead of the intermediate layer, the adhesive layer was pressed against the conductive particle receiving surface of the transfer mold under the conditions of a pressing temperature of 60 °C and a pressing pressure of 1.0 MPa to form an adhesive layer in which conductive particles were transferred (almost buried). The intermediate layer and the insulating base layer were faced to the conductive particle transfer surface of the adhesive layer, and they were bonded under the conditions of a pressing temperature of 50 °C and a pressing pressure of 0.2 MPa. Otherwise, the operation was the same as in Example 1 to manufacture Figure 2 the anisotropic conductive film. The elastic modulus and glass transition temperature of the obtained anisotropic conductive film are shown in Table 2.

[0116] Example 8 ( Figure 3 Manufacture of anisotropic conductive film)

[0117] With the insulating base layer facing the transfer surface of the conductive particles in the intermediate layer and the adhesive layer facing the non-transfer surface of the conductive particles, they are bonded under the conditions of a pressing temperature of 50 °C and a pressing pressure of 0.2 MPa to manufacture Figure 3 the anisotropic conductive film. The elastic modulus and glass transition temperature of the obtained anisotropic conductive film are shown in Table 2.

[0118] Example 9 ( Figure 4 Manufacture of anisotropic conductive film)

[0119] The conditions for transferring the conductive particles to the intermediate layer were changed to a pressing temperature of 60 °C and a pressing pressure of 1.0 MPa, so that the conductive particles were buried in the intermediate layer. Except for this, the operation was the same as in Example 1 to manufacture Figure 4 the anisotropic conductive film. The elastic modulus and glass transition temperature of the obtained anisotropic conductive film are shown in Table 2.

[0120] Example 10 ( Figure 1 Manufacture of anisotropic conductive film)

[0121] 4 parts by mass of the thermal cationic polymerization initiator (Sansei Chemical Industry Co., Ltd., SI-60L) in each layer was replaced with 4 parts by mass of the photo cationic polymerization initiator (ADEKA OPTOMER SP-171, ADEKA Co., Ltd.). Except for this, the anisotropic conductive film was manufactured in the same manner as in Example 1.

[0122] Comparative Example 1 ( Figure 6 Manufacture of anisotropic conductive film)

[0123] (Formation of adhesive layer)

[0124] 40 parts by mass of phenoxy resin (Nippon Steel & Sumikin Chemical Co., Ltd., YP-50), 30 parts by mass of silica filler (Aerosil R805, Nippon Aerosil Co., Ltd.), 30 parts by mass of liquid epoxy resin (Mitsubishi Chemical Corporation, jER828), 4 parts by mass of thermal cationic polymerization initiator (Sansei Chemical Industry Co., Ltd., SI-60L), 1 part by mass of silane coupling agent (Shin-Etsu Chemical Co., Ltd., KBM-403), and 40 parts by mass of conductive particles (Sekisui Chemical Co., Ltd., AUL703, particle size 3 μm) were mixed to prepare a thermopolymerizable composition in which the conductive particles were dispersed. This thermopolymerizable composition was coated on a PET film with a film thickness of 50 μm using a bar coater and dried in an oven at 80 °C for 5 minutes to form an adhesive layer with a thickness (4 μm) shown in Table 2 on the PET film. The melt viscosity of this adhesive layer is shown in Table 2.

[0125] (Formation of insulating base layer)

[0126] Prepare the same insulating base layer as in Example 1.

[0127] (Lamination of insulating base layer and adhesive layer)

[0128] Face the adhesive layer to the insulating base layer and bond them under the conditions of a pressing temperature of 50 °C and a pressing pressure of 0.2 MPa to manufacture Figure 6 the anisotropic conductive film with a two-layer structure. The elastic modulus and glass transition temperature of the obtained anisotropic conductive film are shown in Table 2.

[0129] Comparative Example 2 ( Figure 7 Manufacture of anisotropic conductive film)

[0130] (Formation of adhesive layer)

[0131] Mix 30 parts by mass of phenoxy resin (Nippon Steel & Sumikin Chemical Co., Ltd., YP-50), 20 parts by mass of silica filler (Aerosil R805, Nippon Aerosil Co., Ltd.), 30 parts by mass of liquid epoxy resin (Mitsubishi Chemical Corporation, jER828), 20 parts by mass of photo-radical polymerization type resin EB600 (DAICEL ALLNEX Co., Ltd.), 3 parts by mass of photo-radical polymerization initiator IRGACURE 369 (BASF Japan Co., Ltd.) and 1 part by mass of silane coupling agent (Shin-Etsu Chemical Co., Ltd., KBM-403) to prepare a photo-polymerizable composition in which conductive particles are dispersed. Coat this photo-polymerizable composition on a PET film with a film thickness of 50 μm using a bar coater, dry it in an oven at 80 °C for 5 minutes, and form an adhesive layer with a thickness of 4 μm shown in Table 2 on the PET film. The melt viscosity of this adhesive layer is shown in Table 2.

[0132] Press the adhesive layer onto the conductive particle accommodating surface of the transfer mold under the conditions of a pressing temperature of 50 °C and a pressing pressure of 0.5 MPa in the same manner as in Example 1 to form an adhesive layer with transferred conductive particles, and then peel it off from the transfer mold. The melt viscosity of this adhesive layer, the ratio of the conductive particles existing independently to all the conductive particles, and the conductive particle occupation area ratio are shown in Table 2.

[0133] (Formation of insulating base layer)

[0134] Prepare the same insulating base layer as in Example 1.

[0135] (Lamination of insulating base layer and adhesive layer)

[0136] Face the insulating base layer to the conductive particle transfer surface of the adhesive layer, bond them under the conditions of a pressing temperature of 50 °C and a pressing pressure of 0.2 MPa, and irradiate ultraviolet light with a wavelength of 365 nm and an accumulated light amount of 4000 mL / cm 2 to manufacture Figure 7An anisotropic conductive film 70 having a two-layer structure. The anisotropic conductive film 70 has a thermopolymerizable insulating base layer 71, an adhesive layer 73 after photo-polymerization, and a structure in which conductive particles 4 are held at their interface. The elastic modulus and glass transition temperature of the obtained anisotropic conductive film are shown in Table 2.

[0137] Comparative Example 3( Figure 8 Manufacture of anisotropic conductive film)

[0138] (Formation of insulating base layer)

[0139] Prepare the same insulating base layer as in Example 1.

[0140] (Formation of intermediate layer)

[0141] Prepare a thermopolymerizable composition containing 30 parts by mass of phenoxy resin (Nippon Steel & Sumikin Chemical Co., Ltd., YP-50), 20 parts by mass of silica filler (Aerosil R805, Nippon Aerosil Co., Ltd.), 30 parts by mass of liquid epoxy resin (Mitsubishi Chemical Corporation, jER828), 20 parts by mass of photo-radical polymerizable resin EB600 (DAICEL ALLNEX Co., Ltd.), 3 parts by mass of photo-radical polymerization initiator IRGACURE369 (BASF Japan Co., Ltd.), and 1 part by mass of silane coupling agent (Shin-Etsu Chemical Co., Ltd., KBM-403). Coat this thermopolymerizable composition on a PET film with a thickness of 50 μm and dry it in an oven at 80 °C for 5 minutes to form an adhesive intermediate layer with a thickness (4 μm) shown in Table 2. Press this intermediate layer against the conductive particle accommodating surface of the transfer mold in the same manner as in Example 1 to form an intermediate layer with transferred conductive particles, and then peel it off from the transfer mold. The melt viscosity, the ratio of independently existing conductive particles to all conductive particles, and the conductive particle occupation area ratio of this intermediate layer are shown in Table 2.

[0142] (Formation of adhesive layer)

[0143] Prepare an adhesive layer containing 35 parts by mass of phenoxy resin (Nippon Steel & Sumikin Chemical Co., Ltd., YP-50), 10 parts by mass of silica filler (Aerosil R805, Nippon Aerosil Co., Ltd.), 55 parts by mass of liquid epoxy resin (Mitsubishi Chemical Corporation, jER828), 4 parts by mass of thermal cationic polymerization initiator (Sann Shin Chemical Industry Co., Ltd., SI-60L), and 1 part by mass of silane coupling agent (Shin-Etsu Chemical Co., Ltd., KBM-403).

[0144] (Lamination of insulating base layer, intermediate layer and adhesive layer)

[0145] Place the adhesive layer facing the transfer surface of the conductive particles of the intermediate layer, and place the insulating base layer facing the non-transfer surface of the conductive particles. Bond them under the conditions of a pressing temperature of 50 °C and a pressing pressure of 0.2 MPa, and irradiate ultraviolet rays with a wavelength of 365 nm and an accumulated light quantity of 4000 mL / cm 2 to fabricate Figure 8 the anisotropic conductive film 80. The anisotropic conductive film 80 has a structure in which a heat-polymerizable insulating base layer 81, a photo-polymerized intermediate layer 82, and a heat-polymerizable adhesive layer 83 are laminated, and conductive particles 4 are held at the interface between the intermediate layer 82 and the adhesive layer 83.

[0146] Comparative Example 4 ( Figure 9 fabrication of the anisotropic conductive film)

[0147] (Formation of the adhesive layer)

[0148] Mix 30 parts by mass of phenoxy resin (Nippon Steel & Sumikin Chemical Co., Ltd., YP-50), 20 parts by mass of silica filler (Aerosil R805, Nippon Aerosil Co., Ltd.), 30 parts by mass of liquid epoxy resin (Mitsubishi Chemical Corporation, jER828), 20 parts by mass of a photo-radical polymerizable resin EB600 (DAICEL ALLNEX Co., Ltd.), 3 parts by mass of a photo-radical polymerization initiator IRGACURE 369 (BASF Japan Co., Ltd.), and 1 part by mass of a silane coupling agent (Shin-Etsu Chemical Co., Ltd., KBM-403) to prepare a photo-polymerizable composition in which conductive particles are dispersed. Coat this photo-polymerizable composition on a PET film with a film thickness of 50 μm using a bar coater, and dry it in an oven at 80 °C for 5 minutes to form an adhesive layer with the thickness shown in Table 2 (2 μm) on the PET film. The melt viscosity of this adhesive layer is shown in Table 2.

[0149] (Formation of the intermediate layer)

[0150] Prepare an intermediate layer transferred with conductive particles in the same manner as in Example 1 according to 35 parts by mass of phenoxy resin (Nippon Steel & Sumikin Chemical Co., Ltd., YP-50), 10 parts by mass of silica filler (Aerosil R805, Nippon Aerosil Co., Ltd.), 55 parts by mass of liquid epoxy resin (Mitsubishi Chemical Corporation, jER828), 4 parts by mass of a thermal cationic polymerization initiator (Sann Shin Chemical Industry Co., Ltd., SI-60L), and 1 part by mass of a silane coupling agent (Shin-Etsu Chemical Co., Ltd., KBM-403).

[0151] (Formation of the insulating base layer)

[0152] Prepare an insulating base layer in the same manner as in Example 1.

[0153] (Lamination of the insulating base layer, intermediate layer, and adhesive layer)

[0154] With the adhesive layer facing the transfer surface of the conductive particles of the intermediate layer and the insulating base layer facing the non-transfer surface of the conductive particles, they are bonded under the conditions of a pressing temperature of 50 °C and a pressing pressure of 0.2 MPa, and irradiated with ultraviolet rays having a wavelength of 365 nm and an accumulated light quantity of 4000 mL / cm 2 to manufacture Figure 9 the anisotropic conductive film 90. The anisotropic conductive film 90 has a structure in which a thermopolymerizable insulating base layer 91, a thermopolymerizable intermediate layer 92, and a photo-polymerized adhesive layer 93 are laminated, and conductive particles 4 are held at the interface between the intermediate layer 92 and the adhesive layer 93. The elastic modulus and glass transition temperature of the obtained anisotropic conductive film are shown in Table 2.

[0155] <Evaluation>

[0156] For the anisotropic conductive films of Examples 1 to 10 and Comparative Examples 1 to 4, anisotropic conductive connections were made between the following evaluation ICs and glass substrates by thermocompression bonding under the following conditions (for Example 10, and UV irradiation was also performed as follows) to fabricate evaluation connection structures.

[0157] Evaluation IC: Outer diameter = 1.8 mm × 20 mm × 0.2 mm, gold bump specifications = 15 μm (height) × 15 μm (width) × 100 μm (length) (gap between bumps 15 μm)

[0158] Glass substrate with ITO-coated wiring: Outer diameter = 30 mm × 50 mm × 0.5 mm

[0159] Thermocompression bonding connection: Performed from the IC chip side, thermocompression bonding at 150 °C, 80 MPa, for 5 seconds.

[0160] UV irradiation connection: Thermocompression bonding was performed at a pressure of 100 °C and 80 MPa for 5 seconds. On the other hand, 1 second after 4 seconds from the start of thermocompression bonding, i-line was irradiated from an ultraviolet irradiation device (Omron Corporation, ZUV-C30H).

[0161] For the fabricated evaluation connection structures, (a) initial conduction resistance, (b) conduction reliability, (c) short-circuit incidence rate, (d) pre-bonding property, and (e) particle capture property were evaluated respectively in the manner described below. The obtained results are shown in Table 2.

[0162] (a) Initial conduction resistance

[0163] For the conduction resistance of the obtained evaluation connection structures, a digital multimeter was used to measure the value when a current of 2 mA was passed through using the four-terminal method. In practice, it is desirable that the measured resistance value be 2 Ω or less.

[0164] (b) Conduction reliability

[0165] Similar to the initial on-resistance, measure the on-resistance after placing the obtained evaluation connection structure in a constant temperature bath at 85°C and 85% RH for 500 hours. In practice, it is desirable that the measured resistance value is 6 Ω or less.

[0166] (c) Short-circuit incidence

[0167] When fabricating the connection structure, change the evaluation IC to the following IC (a comb-shaped TEG (test element group) with a 7.5-μm pitch). For the obtained connection structure, measure the short-circuit incidence using a digital multimeter and evaluate it according to the following criteria.

[0168] Outer diameter 1.5 mm × 13 mm

[0169] Thickness 0.5 mm

[0170] Bump specification: gold plating, height 15 μm, size 25 μm × 140 μm, gap between bumps 7.5 μm

[0171] (Evaluation criteria)

[0172] OK (good): When the short-circuit incidence is less than 200 ppm

[0173] NG (bad): When the short-circuit incidence is 200 ppm or more

[0174] (d) Pre-bonding property

[0175] Using a commercially available ACF attaching device (model TTO-1794M, Shibaura Mechatronics Co., Ltd.), attach the anisotropic conductive film to a glass substrate in a size of 2 mm × 5 cm, and perform pre-bonding at a pressure of 1 MPa in such a way that the final temperature after 1 second is 40 - 80°C. Visually check whether the anisotropic conductive film peels off or floats up from the glass substrate when the glass substrate is turned over, and evaluate it according to the following criteria.

[0176] (Evaluation criteria)

[0177] A (very good): When pre-bonding can be performed well even at 40°C

[0178] B (good): When pre-bonding cannot be performed at 40°C, but can be performed at 60°C

[0179] C (ordinary): When pre-bonding cannot be performed at 60°C, but can be performed at 80°C

[0180] D (bad): When pre-bonding cannot be performed at 80°C

[0181] (e) Particle capture property

[0182] Using a metallurgical microscope, observe the terminals after connection from the glass substrate side, count the number of indentations, and thereby determine the capture property of the conductive particles. The determination criteria are shown below. Note that in the table, "e-1" represents the particle capture property evaluation result in an IC chip (chip size 15 μm × 100 μm) with a connection area of 1500 μm 2 , and "e-2" represents the particle capture property evaluation result in an IC chip with a connection area of 800 μm 2 after shifting its positioning by 7 μm.

[0183] (Evaluation Criteria)

[0184] A (Very Good): 10 or more

[0185] B (Good): 5 or more and less than 10

[0186] C (Normal): 3 or more and less than 5

[0187] D (Poor): Less than 3

[0188] [Table 1]

[0189]

[0190] [Table 2]

[0191]

[0192] As can be seen from Table 2, the anisotropic conductive films of Examples 1 to 10 showed good results in any evaluation item. In particular, when the melt viscosity of the layer holding the conductive particles is significantly higher than that of the insulating base layer, there is an effect of improving the capture property of the conductive particles. The reason for showing this effect is that since the melt viscosity of the intermediate layer as the layer holding the conductive particles is higher than that of the insulating base layer, the intermediate layer is difficult to be pushed by the insulating base layer. This is because, conversely, if the melt viscosity of the insulating base layer is higher than that of the intermediate layer, the intermediate layer becomes easy to be pushed by the insulating base layer, and even the intermediate layer with an absolutely high melt viscosity will flow out.

[0193] On the contrary, in the anisotropic conductive film of Comparative Example 1, the conductive particles are randomly dispersed in the conductive particle-containing layer, so the evaluation of the short-circuit incidence rate is "NG (Poor)". In addition, since there is no adhesive layer, the pre-bonding property is lower than that of the examples.

[0194] In the case of Comparative Example 2, since the adhesive layer is a layer after photo-curing, there is a problem with pre-bonding property. In addition, the elastic modulus at 100 °C is lower than 1800 MPa, so the reduction in conduction reliability is significant. In the case of Comparative Example 3, since there is an adhesive layer, the pre-bonding property is improved compared to Comparative Example 2, but the elastic modulus at 100 °C is 1800 MPa, so the reduction in conduction reliability is significant. In the case of Comparative Example 4, although the intermediate layer is thermopolymerizable, the adhesive layer is a layer after photo-polymerization, so there is a problem with pre-bonding property. The elastic modulus at 100 °C is 1800 MPa, so the reduction in conduction reliability is significant.

[0195] Industrial applicability

[0196] The anisotropic conductive film of the present invention is useful for anisotropic conductive connection of electronic components such as IC chips to wiring substrates. With the development of miniaturization of wiring of electronic components, the present invention becomes particularly useful in the case of anisotropically conducting the miniaturized electronic components.

Claims

1. An anisotropic conductive film, which is an anisotropic conductive film having an intermediate layer sandwiched between an insulating base layer and an adhesive layer, and having a heat polymerizability of holding any conductive particles in at least the adhesive layer or the intermediate layer, The conductive particles are embedded in the intermediate layer or the adhesive layer, The melt viscosity of each of the intermediate layer and the adhesive layer is higher than that of the insulating base layer, When looking down at the anisotropic conductive film, the conductive particles exist independently of each other, The elastic modulus of the entire anisotropic conductive film after heat polymerization at 100 °C is higher than 1800 MPa.

2. An anisotropic conductive film, which is an anisotropic conductive film having an intermediate layer sandwiched between an insulating base layer and an adhesive layer, and having a heat polymerizability of holding any conductive particles in at least the adhesive layer or the intermediate layer, The conductive particles are held between the intermediate layer and the adhesive layer, The melt viscosity of each of the intermediate layer and the adhesive layer is higher than that of the insulating base layer, When looking down at the anisotropic conductive film, the conductive particles exist independently of each other, The elastic modulus of the entire anisotropic conductive film after heat polymerization at 100 °C is higher than 1800 MPa.

3. An anisotropic conductive film, which is an anisotropic conductive film having an intermediate layer sandwiched between an insulating base layer and an adhesive layer, and having a heat polymerizability of holding any conductive particles in at least the adhesive layer or the intermediate layer, The conductive particles are held between the insulating base layer and the intermediate layer, The melt viscosity of each of the intermediate layer and the adhesive layer is higher than that of the insulating base layer, When looking down at the anisotropic conductive film, the conductive particles exist independently of each other, The elastic modulus of the entire anisotropic conductive film after heat polymerization at 100 °C is higher than 1800 MPa.

4. The anisotropic conductive film according to any one of claims 1 to 3, wherein the proportion of the independently existing conductive particles to all the conductive particles is 95% or more.

5. The anisotropic conductive film according to any one of claims 1 to 3, wherein the elastic modulus of the entire anisotropic conductive film after heat polymerization at 100 °C is 2500 MPa or less.

6. The anisotropic conductive film according to any one of claims 1 to 3, wherein the glass transition temperature of the anisotropic conductive film after heat polymerization is higher than 145 °C.

7. The anisotropic conductive film according to any one of claims 1 to 3, wherein the glass transition temperature of the anisotropic conductive film after heat polymerization is 168 °C or less.

8. The anisotropic conductive film according to any one of claims 1 to 3, wherein the conductive particles are regularly arranged in a lattice pattern.

9. The anisotropic conductive film according to any one of claims 1 to 3, wherein at least one of the insulating base layer, the adhesive layer, and the intermediate layer contains an insulating filler.

10. The anisotropic conductive film according to any one of claims 1 to 3, wherein the intermediate layer contains an insulating filler.

11. The anisotropic conductive film according to claim 1, wherein the conductive particles are embedded in the intermediate layer.

12. The anisotropic conductive film according to claim 1, wherein the conductive particles are embedded in the adhesive layer.

13. The anisotropic conductive film according to claim 11 or 12, wherein the conductive particles are regularly arranged in a lattice pattern.

14. The anisotropic conductive film according to claim 2, wherein the melt viscosity of the adhesive layer is higher than that of the intermediate layer.

15. The anisotropic conductive film according to claim 14, wherein the conductive particles are regularly arranged in a lattice pattern.

16. The anisotropic conductive film according to claim 3, wherein the melting viscosity of the adhesive layer is higher than that of the intermediate layer.

17. The anisotropic conductive film according to claim 16, wherein the conductive particles are regularly arranged in a lattice pattern.

18. A connection structure formed by anisotropically conducting and connecting a first electronic component to a second electronic component with the anisotropic conductive film according to any one of claims 1 to 17.

19. A method for manufacturing a connection structure, comprising the step of anisotropically conducting and connecting a first electronic component to a second electronic component with the anisotropic conductive film according to any one of claims 1 to 17.

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