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

Abstract

This anisotropic conductive film does not hamper low-temperature rapid curing properties, has a reaction rate that does not fall bellow 80% after anisotropic conductive connection, and does not cause problems with conductive properties or adhesive strength even when an organic peroxide with a one-minute half-life temperature of 120°C or higher is used as a radical polymerization initiator. The anisotropic conductive film has a conductive particle-containing layer containing a film-forming resin, a radical polymerizable compound, a radical polymerization initiator, conductive particles, and a filler. An organic peroxide having a half-life temperature of 132°C or higher is used as the radical polymerization initiator. 5-24 mass% of non-conductive particles having a thermal conductivity of 30 W / m·K or more and an average particle size equal to or less than that of the conductive particles are used in the conductive particle-containing layer as the filler.

Description

Anisotropic conductive film, connection structure, and method for manufacturing the same

[0001] The present invention relates to an anisotropic conductive film, a connection structure, and a method for manufacturing the same.

[0002] Anisotropic conductive films having a conductive particle-containing layer in which conductive particles are dispersed or regularly arranged in an insulating resin layer are widely used as connecting materials for electronic components. From the viewpoint of low-temperature, short-time curing (low-temperature, fast curing), such anisotropic conductive films are formed from a resin composition containing a film-forming resin such as a phenoxy resin, conductive particles, a radical-polymerizable compound such as a (meth)acrylate, and an organic peroxide as a radical polymerization initiator having a 1-minute half-life temperature of less than 120°C.

[0003] However, an anisotropic conductive film using an organic peroxide with a one-minute half-life temperature of less than 120°C has the problem of reduced storage stability. To address this issue, using an organic peroxide with a one-minute half-life temperature of 120°C or higher as a radical polymerization initiator for an anisotropic conductive film can improve the storage stability of the anisotropic conductive film, but this can result in a reversible problem of "deterioration of the low-temperature rapid curing properties of the anisotropic conductive film." To solve this problem, it has been proposed to incorporate non-conductive particles with a thermal conductivity of 10 W / m·K or higher into an anisotropic conductive film (Patent Document 1).

[0004] JP 2009-289729 A

[0005] However, the technology of Patent Document 1 sometimes fails to achieve low-temperature, rapid curing properties equivalent to those achieved when an organic peroxide with a one-minute half-life temperature of less than 120° C. is used for the anisotropic conductive film. In addition, there is concern that the reaction rate of the anisotropic conductive film after compression bonding (after anisotropic conductive connection) will not reach 80% or more, which may adversely affect the conductivity characteristics and adhesive strength.

[0006] The object of the present invention is to solve the problems of the related art, and to provide an anisotropic conductive film formed from a resin composition containing a film-forming resin such as a phenoxy resin, conductive particles, a radically polymerizable compound such as a (meth)acrylate, and an organic peroxide as a radical polymerization initiator, such that even when an organic peroxide with a one-minute half-life temperature of 120°C or higher is used as the radical polymerization initiator from the standpoint of storage stability, the film exhibits low-temperature, fast curing properties equivalent to those when an organic peroxide with a one-minute half-life temperature of less than 120°C is used, and further, to prevent the reaction rate after anisotropic conductive connection from falling below 80%, thereby preventing problems from occurring in the conductivity characteristics and adhesive strength of the anisotropic conductive film.

[0007] The present inventors have discovered that the above-mentioned objects of the present invention can be achieved in an anisotropic conductive film having a conductive particle-containing layer containing a film-forming resin, a radically polymerizable compound, a radical polymerization initiator, conductive particles, and a filler by using, as the radical polymerization initiator, an organic peroxide whose one-minute half-life temperature is 132°C or higher, which is even higher than 120°C, and by using, as the filler, non-conductive particles having a thermal conductivity of 30 W / m K or higher, which is significantly higher than 10 W / m K, and an average particle size equal to or smaller than the average particle size of the conductive particles, in a specific amount range, and thereby completing the present invention.

[0008] That is, the present invention provides an anisotropic conductive film having a conductive particle-containing layer containing a film-forming resin, a radically polymerizable compound, a radical polymerization initiator, conductive particles, and a filler, wherein the radical polymerization initiator is an organic peroxide having a one-minute half-life temperature of 132°C or higher, the filler is non-conductive particles having a thermal conductivity of 30 W / m K or higher and an average particle size equal to or smaller than the average particle size of the conductive particles, and the content of the non-conductive particles in the conductive particle-containing layer is 5% by mass or more and 24% by mass or less.

[0009] The present invention also provides a connection structure in which a first electronic component and a second electronic component are anisotropically conductively connected via the anisotropic conductive film of the present invention.The present invention also provides a method for producing a connection structure in which the anisotropic conductive film of the present invention is sandwiched between the first electronic component and the second electronic component and pressure-bonded to form an anisotropic conductive connection.

[0010] The anisotropic conductive film of the present invention has a conductive particle-containing layer containing a film-forming resin, a radically polymerizable compound, a radical polymerization initiator, conductive particles, and a filler. The radical polymerization initiator is an organic peroxide having a one-minute half-life temperature of 132°C or higher. This improves storage stability. The filler contains non-conductive particles with a thermal conductivity of 30 W / m·K or higher, significantly exceeding 10 W / m·K, in a concentration of 5% to 24% by mass in the conductive particle-containing layer. This allows for efficient distribution of thermal energy throughout the anisotropic conductive film during anisotropic conductive connection, enabling anisotropic conductive connection at relatively low temperatures not significantly exceeding the one-minute half-life temperature, and ensuring a reaction rate of 80% or higher. Furthermore, the average particle diameter of the non-conductive particles is equal to or smaller than the average particle diameter of the conductive particles, so that the conductive particles' ability to be pressed into the film during anisotropic conductive connection is not impaired. Therefore, it is possible to prevent problems from occurring in the conductivity and adhesive strength of the anisotropic conductive film of the present invention not only immediately after production but also after normal storage (e.g., storage exposed to an environment of 30°C and 60% RH), and further in the conductivity and adhesive strength after a pressure cooker test (PCT).

[0011] Fig. 1 is a schematic cross-sectional view of an anisotropic conductive film having a single layer structure according to the present invention, and Fig. 2 is a schematic cross-sectional view of an anisotropic conductive film having a two-layer structure according to the present invention.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] <<Single-Layer Anisotropic Conductive Film of Fig. 1 >> Fig. 1 is a schematic cross-sectional view of an anisotropic conductive film 10 having a single-layer conductive particle-containing layer 1. The conductive particle-containing layer 1 constituting the anisotropic conductive film 10 contains a film-forming resin, a radical-polymerizable compound, a radical polymerization initiator, conductive particles 2, and a filler 3.

[0014] <Constituent Components of Conductive Particle-Containing Layer 1> The conductive particle-containing layer 1 contains a film-forming resin, a radical polymerizable compound, a radical polymerization initiator, conductive particles, and a filler. Each component will be described in detail below.

[0015] (Film-forming resin) The conductive particle-containing layer 1 of the present invention preferably contains a phenoxy resin having excellent impact resistance as a film-forming resin. The weight-average molecular weight of such a phenoxy resin is preferably 30,000 or more, more preferably 50,000 or more, and preferably 80,000 or less, more preferably 60,000 or less. The weight-average molecular weight can be measured by a conventional gel permeation chromatography method.

[0016] If the content of the film-forming resin in the conductive particle-containing layer 1 is too low, the anisotropic conductive film will be prone to bending, and if it is too high, the fluidity of the resin will decrease during anisotropic conductive connection, making it difficult to obtain good conductivity. In addition, flexibility will also decrease, and adhesive strength will tend to be low. Therefore, the content is preferably 20.0 mass % or more, more preferably 25.0 mass % or more, and preferably 50.0 mass % or less, more preferably 35.0 mass % or less.

[0017] Such a phenoxy resin can be selected from known phenoxy resins and is generally an epoxy group-free polyhydroxypolyether (thermoplastic resin) synthesized from bisphenols and epichlorohydrin, and bisphenol A is preferably used as the bisphenol component from the viewpoint of availability.

[0018] The conductive particle-containing layer 1 of the present invention may contain other general film-forming components besides phenoxy resin, such as epoxy resin, polyester resin, urethane resin, butadiene resin, polyamide resin, polyimide resin, polyolefin resin, polyvinyl butyral resin, and ethylene-vinyl acetate copolymer resin, as long as the effects of the present invention are not impaired.

[0019] (Radical Polymerizable Compound) The conductive particle-containing layer 1 of the present invention preferably contains, as the radical polymerizable compound, a monofunctional (meth)acrylate such as a known alkyl (meth)acrylate, a polyfunctional (meth)acrylate such as polypropylene glycol di(meth)acrylate, or an acrylic compound such as urethane (meth)acrylate. Among these, urethane (meth)acrylate, which is a reaction product of hydroxyalkyl (meth)acrylates and diisocyanates, is preferred from the viewpoint of improving the adhesion of flexible printed circuit boards (FPCs) to polyimide, thereby improving the cohesive strength of the cured product and improving electrical conductivity reliability. These acrylic compounds may be monomers, oligomers, or polymers. Polyfunctional (meth)acrylates can also function as crosslinking agents, and isocyanuric acid EO-modified di- or tri(meth)acrylates are preferred crosslinking agents. The term "(meth)acrylate" refers to both acrylate and methacrylate.

[0020] If the content of the radical polymerizable compound in the conductive particle-containing layer 1 is too low, the cohesive force of the conductive particle-containing layer 1 will be weakened, and there is a concern that the desired adhesive strength will not be achieved in the anisotropic conductive film, while if the content is too high, the liquid component will increase relatively, making the conductive particle-containing layer 1 itself soft and causing a concern that it will adhere to the slitting blade when slitting the anisotropic conductive film. Therefore, the content is preferably 20.0 mass % or more, more preferably 30.0 mass % or more, and preferably 50.0 mass % or less, more preferably 40.0 mass % or less. Note that, as long as the effects of the present invention are not impaired, radical polymerizable components other than acrylic compounds, such as alkene compounds, may be contained.

[0021] (Radical Polymerization Initiator) The conductive particle-containing layer 1 contains, as a radical polymerization initiator, an organic peroxide having a one-minute half-life temperature of 132°C or higher, preferably 135°C or higher, and more preferably 140°C or higher. This can improve the storage stability of the anisotropic conductive film. Note that the upper limit of the one-minute half-life temperature of the organic peroxide is preferably 155°C or lower, from the viewpoints of the polymerization reaction rate and polymerization rate.

[0022] Specific examples of organic peroxides (one-minute half-life temperature) are shown below: * 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (124.3°C) * Dibenzoyl peroxide (130.0°C) * Mixture of di(3-methylbenzoyl) peroxide, benzoyl(3-methylbenzoyl) peroxide and dibenzoyl peroxide (131.1°C) * Disuccinic acid peroxide (131.8°C) * t-Hexylperoxy-2-ethylhexanoate (132.6°C) * t-Butylperoxy-2-ethylhexanoate (134.0°C) * Di-t-butylperoxyhexahydroterephthalate (142.0°C) * 1,1-di(t-hexylperoxy)cyclohexane (149.2°C) * 1,1-di(t-butylperoxy)cyclohexane (153.8°C) * 2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane (153.8°C) * t-Hexylperoxyisopropyl monocarbonate (155.0°C) * t-Butylperoxy-3,5,5-trimethylhexanoate (166.0°C) * t-Butylperoxylaurate (159.4°C) * t-Butylperoxyisopropyl monocarbonate (158.8°C) * t-Butylperoxy 2-ethylhexyl monocarbonate (161.4°C) * t-Hexylperoxybenzoate (160.3°C) * 2,5-dimethyl-2,5-di(benzoylperoxy)hexane (158.2°C) * t-Butylperoxyacetate (159.9°C) * 2,2-di(t-butylperoxy)butane (159.9°C) * t-Butyl peroxybenzoate (166.8°C) * n-Butyl 4,4-di(t-butylperoxy)valerate (172.5°C) * Di(2-t-butylperoxyisopropyl)benzene (175.4°C) * Dicumyl peroxide (175.2°C) * Di-t-hexyl peroxide (176.7°C) * 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (179.8°C) * t-Butylcumyl peroxide (173.3°C) * Di-t-butyl peroxide (185.9°C) * p-Menthane hydroperoxide (199.5°C) * 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 (194.3°C) *diisopropylbenzene hydroperoxide (232.5°C) *1,1,3,3-tetramethylbutyl hydroperoxide (246.6°C) *cumene hydroperoxide (254.0°C) *t-butyl hydroperoxide (260.7°C),

[0023] Among the above organic peroxides, di-t-butylperoxyhexahydroterephthalate (142.0°C) can be preferably used because it provides good properties such as conductivity and adhesiveness even when pressure-bonded at a low temperature of 150°C.

[0024] If the content of the radical polymerization initiator in the conductive particle-containing layer 1 is too small, the average molecular weight of the polymer of the radical polymerizable compound increases, reducing the adhesiveness of the conductive particle-containing layer 1 and the ability to push the conductive particles in. Conversely, if the content is too large, the average molecular weight of the polymer of the radical polymerizable compound decreases, tending to reduce the impact resistance of the conductive particle-containing layer 1. Therefore, the content is 5 parts by mass or more, preferably 10 parts by mass or more, and 24 parts by mass or less, preferably 20 parts by mass or less, relative to 100 parts by mass of the radical polymerizable compound.

[0025] (Conductive Particles) The conductive particle-containing layer 1 contains conductive particles 2 to impart anisotropic conductivity to the anisotropic conductive film 10. The conductive particles 2 may be the same as known conductive particles used in general anisotropic conductive films. For example, metal particles, alloy particles, metal-coated resin particles, etc. may be appropriately selected and used.

[0026] If the average particle diameter of the conductive particles 2 is too small, the indentation strength tends to be low, and if it is too large, the insulation reliability between wirings tends to deteriorate, so it is preferably 1.5 μm or more, more preferably 2.0 μm or more, and is preferably not more than the thickness of the conductive particle-containing layer, more preferably not more than 5.0 μm. This average particle diameter can be measured using a commercially available particle size distribution measuring device using a laser diffraction / scattering method.

[0027] If the content of conductive particles 2 in the conductive particle-containing layer 1 is too small, the connection reliability of the anisotropic conductive film will be insufficient, and if it is too large, there is a concern that a short circuit will occur. Therefore, the content is preferably 5.0 mass % or more, more preferably 7.5 mass % or more, and preferably 45.0 mass % or less, more preferably 35.0 mass % or less.

[0028] The conductive particles 2 may be randomly dispersed and held in the conductive particle-containing layer 1, or may be arranged regularly, for example, in a lattice pattern, by a known method. The conductive particles 2 may be held so as to be exposed on the surface of the conductive particle-containing layer 1, or may be embedded. They may be held so as not to overlap in the film thickness direction in a planar view of the film. If the number density of the conductive particles in a planar view of the film is too low, it may be difficult for the particles to be captured on the terminals, which may make it impossible to accommodate narrower picture frames of image display devices or finer pitches of electrodes on circuit boards. If the number density is too high, the reliability of insulation between wirings tends to decrease. Therefore, the number density is preferably 3500 particles / mm. ２ More preferably, 5000 pieces / mm ２ or more, and preferably 25,000 pieces / mm ２ Less than or equal to 20,000 pieces / mm ２ The following is the result.

[0029] (Filler) In order to improve the reduced low-temperature, rapid curing properties caused by the use of an organic peroxide having a one-minute half-life temperature of 132°C or higher as a radical polymerization initiator, the conductive particle-containing layer 1 contains non-conductive particles having a thermal conductivity of 30 W / m·K or higher, preferably 300 W / m·K or higher, as the filler 3. If non-conductive particles having a thermal conductivity of less than 30 W / m·K are added, there is a concern that the reaction rate in the conductive particle-containing layer 1 may not be able to be increased to 80% or higher when heated during anisotropic conductive connection.

[0030] The average particle size of the non-conductive particles is set to be equal to or smaller than the average particle size of the conductive particles 2, preferably 30% to 70% of that of the conductive particles 2. If the average particle size is larger than the average particle size of the conductive particles 2, it becomes difficult to obtain good electrical conductivity. The average particle size of the non-conductive particles can be measured using a commercially available particle size distribution measuring device that uses a laser diffraction / scattering method.

[0031] Such non-conductive particles can be appropriately selected from those having a thermal conductivity of 30 W / m·K or more and an average particle size equal to or less than the average particle size of the conductive particles 2. Examples of such non-conductive particles include non-conductive nitrides and carbides, preferably metal nitrides and metal carbides. Specific examples include aluminum nitride (320 W / m·K) and silicon carbide (270 W / m·K). A particularly preferred non-conductive particle is aluminum nitride, due to its high thermal conductivity and low acquisition cost.

[0032] If the content of the non-conductive particles as a filler in the conductive particle-containing layer 1 is too small, it becomes difficult to sufficiently improve the low-temperature rapid curing properties of the anisotropic conductive film, and if it is too large, the pressing ability of the conductive particles 2 decreases. Therefore, the content is preferably 5 mass % or more, more preferably 10 mass % or more, preferably 24 mass % or less, and more preferably 20 mass % or less.

[0033] The non-conductive particles may be randomly dispersed and held in the conductive particle-containing layer 1, similar to the conductive particles 2, but may also be arranged regularly, for example, in a lattice pattern, by a known method. The non-conductive particles may be held so as to be exposed on the surface of the conductive particle-containing layer 1, or may be embedded. They may also be held so as not to overlap in the film thickness direction in plan view of the film. Note that if the number density of the non-conductive particles in plan view of the film is too low, electrical connection becomes difficult, and if it is too high, electrical short circuits tend to occur between adjacent wirings, so it is preferably 100 particles / mm ２ More preferably, 4000 pieces / mm ２ or more, and preferably 20,000 pieces / mm ２ Less than or equal to 12,000 pieces / mm, more preferably ２ The following is the result.

[0034] The filler 3 contains non-conductive particles having a thermal conductivity of 30 W / m·K or more and an average particle size equal to or smaller than that of the conductive particles 2. However, various additives used in conventional anisotropic conductive films, such as softeners such as butadiene rubber, fillers (viscosity modifiers) such as silica filler, coloring pigments such as carbon black, adhesion improvers such as silane coupling agents and phosphate ester compounds, and internal mold release agents such as calcium stearate, may also be contained as fillers within a range that does not impair the effects of the present invention. A preferred phosphate ester compound is a reaction product of a 6-hexanolide addition polymer of 2-hydroxyethyl methacrylate with phosphoric anhydride.

[0035] (Thickness of Conductive Particle-Containing Layer) The thickness of the conductive particle-containing layer 1 constituting the anisotropic conductive film of the present invention is preferably 10 μm or more, more preferably 15 μm or more, and preferably 25 μm or less, more preferably 20 μm or less, since if it is too thin, it becomes difficult to obtain sufficient adhesive strength, and if it is too thick, stable slits tend not to be formed.

[0036] <Release Base Film> In the anisotropic conductive film 10 of the present invention, a release base film (not shown) may be provided on one side of the conductive particle-containing layer 1, if necessary. The release base film can function as a film onto which the conductive particle-containing layer-forming composition is applied when the conductive particle-containing layer 1 is formed. In addition, a release base film may also be provided as a cover film on the opposite side of the conductive particle-containing layer 1. As such a release base film, a known release base film that is applied to ordinary anisotropic conductive films can be used. For example, a polyethylene terephthalate film that has been treated with a silicone release agent can be used as the release base film.

[0037] <<Anisotropic conductive film having a laminated structure shown in Fig. 2>> Fig. 2 is a schematic cross-sectional view of an anisotropic conductive film 20 having a laminated structure in which an insulating resin layer 24 is further laminated on a conductive particle-containing layer 21. The conductive particle-containing layer 21 constituting the anisotropic conductive film 20 contains a film-forming resin, a radical polymerizable compound, a radical polymerization initiator, conductive particles 22, and a filler 23, similar to the anisotropic conductive film having a single-layered structure shown in Fig. 1 .

[0038] The insulating resin layer 24 is a layer that flows during anisotropic conductive connection to fill the space between opposing connection objects and firmly bond them, and does not contain conductive particles. The insulating resin layer 24 can be composed of a film-forming resin, a radical-polymerizable compound, a radical polymerization initiator, and a filler, as described for the anisotropic conductive film in FIG.

[0039] Furthermore, if the thickness of the insulating resin layer 24 is too thin, the mounting portion will not be sufficiently filled with resin, and if it is too thick, it will hinder the mounting portion from being pressed in, so the thickness is preferably 4 μm or more, more preferably 6 μm or more, and preferably 20 μm or less, and more preferably 10 μm or less. In the embodiment of Fig. 2, the thickness of the conductive particle-containing layer can be made thinner than the thickness of the conductive particle-containing layer in the embodiment of Fig. 1. For example, it can be preferably 2 μm or more and 10 μm or less.

[0040] If the thickness of the insulating resin layer 24 is thicker than the thickness of the conductive particle-containing layer 21, there is a concern that the pressing ability will deteriorate due to an increase in viscosity, and therefore it is preferable that the insulating resin layer 24 does not contain non-conductive particles.

[0041] <<Production of Anisotropic Conductive Films>> The anisotropic conductive film of Fig. 1 can be produced by applying a conductive particle-containing layer-forming composition obtained by uniformly mixing a film-forming resin, a radical polymerizable compound, a radical polymerization initiator, conductive particles, and a filler, together with a general-purpose solvent as needed, to one side of a release base film such as a release-treated polyethylene terephthalate film by a conventional method, for example, with a bar coater, and drying the composition to form a conductive particle-containing layer. The anisotropic conductive film of Fig. 2 can be produced by similarly applying an insulating resin layer-forming composition obtained by uniformly mixing a film-forming resin, a radical polymerizable compound, a radical polymerization initiator, and a filler, together with a general-purpose solvent as needed, to one side of another release base film by a conventional method, and drying the composition to form an insulating resin layer. Next, the conductive particle-containing layer and the insulating resin layer are laminated facing each other, thereby producing an anisotropic conductive film having a laminate structure of release base film / conductive particle-containing layer / insulating resin layer / release base film (cover film).

[0042] The anisotropic conductive film of the present invention produced in this manner can be slit into narrow widths, wound onto a reel, and distributed as a wound body. From the viewpoint of practicality, the film length of such a wound body is preferably 5 m or more, more preferably 50 m or more, and preferably 5,000 m or less, more preferably 1,000 m or less. Furthermore, the peel strength between the insulating resin layer 24 and the release base film in the anisotropic conductive film of the present invention, as measured by a T-peel test according to JIS K 6854, is preferably 200 to 400 mN / 5 cm, more preferably 250 to 350 mN / 5 cm. If the peel strength is below this range, the anisotropic conductive film tends to lift from the release base film during slitting, resulting in blocking. If the peel strength is above this range, the anisotropic conductive film tends to be difficult to adhere to glass.

[0043] <<Uses of Anisotropic Conductive Film>> The anisotropic conductive film of the present invention can be preferably used to anisotropically conductively connect a first electronic component such as an FPC, IC chip, or IC module to a second electronic component such as an FPC, rigid substrate, ceramic substrate, glass substrate, or plastic substrate. The connection structure thus obtained, i.e., a connection structure in which a first electronic component and a second electronic component are anisotropically conductively connected via the anisotropic conductive film of the present invention, also constitutes part of the present invention. The present invention also constitutes a method for producing a connection structure in which an anisotropic conductive connection is achieved by sandwiching the anisotropic conductive film of the present invention between the first electronic component and the second electronic component and then crimping them together.

[0044] The present invention will be specifically described below with reference to examples and comparative examples.

[0045] For the compositions for forming conductive particle-containing layers and compositions for forming insulating resin layers prepared in the following examples and comparative examples, the product names and sources of the resin composition components shown in Table 1 (anisotropic conductive films with a single-layer structure) and Table 2 (anisotropic conductive films with a two-layer structure) are as follows:

[0046] *Phenoxy resin: YP-50, Nippon Steel Chemical & Material Co., Ltd. *Acrylic monomer: Aronix M-315, Toagosei Co., Ltd. *Urethane acrylic oligomer: Aronix M-1600, Toagosei Co., Ltd. *Rubber component: SG80H, Nagase ChemteX Corporation *Acrylic phosphate monomer: Light Ester P-1M, Kyoeisha Chemical Co., Ltd. *Radical polymerization initiator 1: Perkadox 62-W65, Kayaku Nouryon Co., Ltd. (1-minute half-life temperature: 142.0°C) *Radical polymerization initiator 2: Perloyl L, NOF Corporation (1-minute half-life temperature: 116.4°C) *Radical polymerization initiator 3: Niper BMT-K40, NOF Corporation (1-minute half-life temperature: 131.0°C) *Conductive particles: Ni / Au plated acrylic resin particles, Nippon Chemical Industry Co., Ltd., average particle size 3 μm *Aluminum nitride 1: Thermal conductivity 320 W / m·K, average particle size 2 μm *Aluminum nitride 2: Thermal conductivity 320 W / m·K, average particle size 5 μm *Boron nitride: Thermal conductivity 30 W / m·K, average particle size 1.7 μm *Zirconium oxide: Thermal conductivity 3 W / m·K, average particle size 0.01 μm

[0047] <Preparation of composition for forming conductive particle-containing layer> PMA (propylene glycol monomethyl ether acetate) was added to the blending components in Tables 1 and 2 so that the solid content was 45 mass %, and the mixture was mixed uniformly to prepare a composition for forming a conductive particle-containing layer for producing an anisotropic conductive film (ACF) with a single layer or two layer structure.

[0048] <Preparation of composition for forming insulating resin layer> PMA was added to the components shown in Table 2 so that the solid content was 42 mass %, and the mixture was mixed uniformly to prepare a composition for forming an insulating resin layer for producing an anisotropic conductive film (ACF) with a two-layer structure.

[0049]

[0050]

[0051] Examples 1 to 5, Comparative Examples 1 to 8 (Preparation of anisotropic conductive films with a single-layer structure) The conductive particle-containing layer-forming composition shown in Table 1 was applied to a 25 μm-thick polyethylene terephthalate release base film having a silicone release-treated surface using a bar coater to a dry thickness of 10±0.5 μm, and the applied film was dried for 3 minutes in an oven at 55° C. to form a conductive particle-containing layer on the release base film. A general cover film was laminated at 45° C. onto the exposed surface of the conductive particle-containing layer to obtain a single-layer anisotropic conductive film sandwiched between the release base film and the cover film.

[0052] Examples 6 to 9, Comparative Examples 9 to 17 (Preparation of anisotropic conductive films with a two-layer structure) Formation of conductive particle-containing layer The conductive particle-containing layer-forming composition shown in Table 2 was applied to a 25 μm-thick polyethylene terephthalate release base film having a silicone release-treated surface using a bar coater so as to give a dry thickness of 4±0.5 μm, and the applied composition was dried in an oven at 55° C. for 3 minutes to form a conductive particle-containing layer on the release base film.

[0053] Formation of insulating resin layer The composition for forming an insulating resin layer shown in Table 2 was applied using a bar coater to a 50 μm thick polyethylene terephthalate release base film having a silicone release treated surface so as to give a dry thickness of 6±0.5 μm, and the applied composition was dried in an oven at 70° C. for 4 minutes to form an insulating resin layer on the release base film.

[0054] Preparation of Anisotropic Conductive Film The obtained insulating resin layer and conductive particle-containing layer were placed opposite each other and laminated under conditions of 45°C and 0.5 MPa to obtain an anisotropic conductive film having a two-layer structure of release base film / insulating resin layer / conductive particle-containing layer / release base film (cover film).

[0055] <Evaluation> The anisotropic conductive films of the Examples and Comparative Examples were tested or inspected and evaluated as follows for the "reaction rate" after application of the anisotropic conductive connection conditions, initial characteristics (specifically, "initial conduction resistance," "conduction resistance after pressure cooker test (PCT) (85°C, 85% RH, 500 hours)," and "initial adhesive strength"), and characteristics after storage (30°C, 60% RH, 48 hours) (specifically, "conduction resistance after storage," "conduction resistance after PCT" after storage, and "adhesion strength after storage"). The results obtained are shown in Table 3 for the anisotropic conductive films with a single layer structure and in Table 4 for the anisotropic conductive films with a two-layer structure.

[0056] (Reaction Rate) Using an infrared spectrometer (Fourier transform infrared spectroscopy (FT-IR)), the vinyl groups (polymerizable groups) of the anisotropic conductive film were measured before and after connection, and the reaction rate was measured from the change. Specifically, IR analysis was performed immediately after the anisotropic conductive film was produced, and the reaction rate was calculated as the ratio of the absorption intensity of the vinyl groups in the anisotropic conductive film portion of the connection structure after compression bonding produced during the initial characteristic evaluation described below to the reference absorption intensity at 1,640 cm-1. In practice, the reaction rate is preferably 80% or higher.

[0057] (Initial Properties) 1. Initial Conduction Resistance / Conduction Resistance After PCT Each anisotropic conductive film prepared in Examples and Comparative Examples was cut to a width of 1.5 mm and a length of 40 mm, and the cover film was peeled off to obtain a tape-shaped anisotropic conductive film. Next, the tape-shaped anisotropic conductive film was temporarily attached to the edge of a SiN glass substrate (0.7 mm thick) on which an indium zinc oxide transparent electrode was formed, with the conductive particle-containing layer facing up, and placed on a hot plate at 45°C, and uniformly pressed from the release base film side on the insulating resin layer side. The release base film was then released, and the metal wiring portion of the evaluation FPC (50 μm thick) was bonded so that the exposed conductive particle-containing layer or insulating resin layer side was completely covered. Furthermore, using a 1.5 mm wide, 60 mm long crimping tool head, the FPC and the glass substrate were thermocompressed (135 ° C, 3 MPa, 10 seconds) via a 0.15 mm thick Teflon (registered trademark) film, thereby bonding the opposing electrodes of the FPC and the glass substrate with the cured anisotropic conductive film. This resulted in an anisotropically conductive connection structure. The FPC specifications were a polyimide film thickness of 44 μm, a copper circuit thickness of 20 μm, and a copper circuit line width of 60 μm (pitch 120 μm, L / S = 1 / 1).

[0058] The conduction resistance value between the anisotropically conductively connected electrodes of the resulting connection structure was measured by the four-terminal method immediately (initial stage) after the connection structure was manufactured. From a practical standpoint, it is preferable that the resistance be 3 Ω or less. From the viewpoint of connection reliability, the connection structure was subjected to a pressure cooker test (PCT) in which it was held in a constant temperature and humidity chamber (85°C, 85% RH) for 500 hours, and after the test, the conduction resistance after PCT was measured by the four-terminal method. From a practical standpoint, it is preferable that the resistance be 4 Ω or less.

[0059] 2. Initial adhesive strength As in the case of the initial conduction resistance test, a connection structure was obtained by anisotropically conductively connecting a glass substrate and an FPC using each anisotropic conductive film produced in Examples and Comparative Examples. However, instead of an FPC with a polyimide film thickness of 44 μm, a copper circuit thickness of 20 μm, and a copper circuit line width of 60 μm (pitch of 120 μm, L / S=1 / 1), an FPC with a polyimide film thickness of 66 μm, a copper circuit thickness of 20 μm, and a copper circuit line width of 60 μm (pitch of 120 μm, L / S=1 / 1) was used.

[0060] The resulting connection structure including the FPC for evaluation was cut into a 1 cm width, and the FPC for evaluation was pulled up at an angle of 90° at a speed of 50 mm / sec using a tensile tester (RTC1201, A&D Co., Ltd.) to measure the adhesive strength. In practice, a value of 6.5 N / cm or more is preferred.

[0061] (Characteristics after storage) 3. Conduction resistance after storage, conduction resistance after PCT, and adhesive strength after storage Each anisotropic conductive film produced in the examples and comparative examples was stored for 48 hours in a constant temperature and humidity chamber at 30°C and 60% RH. Using the anisotropic conductive film after storage, a connection structure identical to that produced when evaluating the initial characteristics was produced, and the conduction resistance after storage, the conduction resistance after PCT, and the adhesive strength after storage were measured in the same manner as for the initial characteristics. In practice, it is preferable that the conduction resistance after storage is 3Ω or less, the conduction resistance after PCT is 4Ω or less, and the adhesive strength after storage is 4 N / cm or more, respectively.

[0062]

[0063]

[0064] (Discussion of Evaluation Results) The anisotropic conductive films of Examples 1 to 9 used an organic peroxide with a 1-minute half-life temperature of 142.0°C as the radical polymerization initiator, and contained non-conductive aluminum nitride particles or boron nitride particles with a thermal conductivity of 30 W / m·K or more and an average particle size smaller than the average particle size of the conductive particles in the conductive particle-containing layer in an amount of 5% by mass to 24% by mass. Therefore, they could be evaluated as being practically preferable in terms of all the evaluation items of reaction rate, initial characteristics, and post-storage characteristics. In contrast, the anisotropic conductive films of Comparative Examples 1 to 17 could not be evaluated as being practically preferable in terms of any of the evaluation items of reaction rate, initial characteristics, or post-storage characteristics, as described below.

[0065] In the case of the anisotropic conductive film having a single layer structure in Comparative Example 1, an organic peroxide with a one-minute half-life temperature of 116.4°C was used as the radical polymerization initiator, and since it was relatively highly reactive, there were no problems with the reaction rate or initial characteristics. However, since it did not contain non-conductive particles, it was not rated favorably in any of the evaluation items of the characteristics after storage.

[0066] In the case of the anisotropic conductive film having a single layer structure in Comparative Example 2, an organic peroxide having a one-minute half-life temperature of 131.0°C was used as a radical polymerization initiator in the conductive particle-containing layer, but since it did not contain non-conductive particles, it was not rated favorably in any of the evaluation items of the post-storage properties.

[0067] In the case of the anisotropic conductive film having a single layer structure in Comparative Example 3, non-conductive particles were contained in the conductive particle-containing layer, but the reactivity was not sufficiently suppressed by the organic peroxide with a 1-minute half-life temperature of 131.0°C used as the radical polymerization initiator, and therefore, the film was not rated favorably in any of the evaluation items of the post-storage properties.

[0068] In the case of the single-layer anisotropic conductive film of Comparative Example 4, although an organic peroxide with a one-minute half-life temperature of 142.0°C was used as the radical polymerization initiator, it did not contain non-conductive particles, and therefore, the evaluation items of the reaction rate, initial characteristics, and characteristics after storage were not favorable.

[0069] In the case of the single-layer anisotropic conductive film of Comparative Example 5, although an organic peroxide with a 1-minute half-life temperature of 142.0°C was used as the radical polymerization initiator, the content of aluminum nitride particles, which are non-conductive particles with an average particle diameter of 2 μm, was 4%, which was below 5%, and therefore the film was not rated favorably for any of the evaluation items, including the initial characteristics and the post-storage characteristics other than the post-storage adhesive strength.

[0070] In the case of the single-layer anisotropic conductive film of Comparative Example 6, although an organic peroxide with a 1-minute half-life temperature of 142.0°C was used as the radical polymerization initiator, the average particle diameter of the aluminum nitride particles used as the non-conductive particles was 5 μm, which exceeds the average particle diameter of 3 μm of the conductive particles, and therefore, the film was not rated favorably for either the initial characteristics or the characteristics after storage.

[0071] In the case of the single-layer anisotropic conductive film of Comparative Example 7, although an organic peroxide with a 1-minute half-life temperature of 142.0°C was used as the radical polymerization initiator, the content of aluminum nitride particles, which are non-conductive particles with an average particle diameter of 2 μm, was 25%, which was higher than 24%, and therefore the film was not rated favorably for either the initial characteristics or the characteristics after storage.

[0072] In the case of the single-layer anisotropic conductive film of Comparative Example 8, an organic peroxide with a one-minute half-life temperature of 142.0°C was used as the radical polymerization initiator, but zirconium oxide with a thermal conductivity of 3 W / m·K, which is significantly lower than 30 W / m·K, was used as the non-conductive particles, and therefore the evaluation items of reaction rate, initial characteristics, and characteristics after storage were not favorable.

[0073] In the case of the two-layer anisotropic conductive film of Comparative Example 9, an organic peroxide with a one-minute half-life temperature of 116.4°C was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer, and therefore there were no problems with the initial characteristics. However, since neither the conductive particle-containing layer nor the insulating resin layer contained non-conductive particles, the film was not rated favorably for any of the evaluation items of the characteristics after storage.

[0074] In the case of the two-layer anisotropic conductive film of Comparative Example 10, an organic peroxide with a one-minute half-life temperature of 131.0°C was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer, but the conductive particle-containing layer did not contain non-conductive particles. Therefore, although there were no problems with the initial characteristics, none of the evaluation items for the characteristics after storage were favorably evaluated.

[0075] In the case of the two-layer anisotropic conductive film of Comparative Example 11, non-conductive particles were contained in the conductive particle-containing layer, but the reactivity of the organic peroxide with a 1-minute half-life temperature of 131.0°C used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer was not sufficiently suppressed, and therefore, none of the evaluation items of the post-storage properties were evaluated favorably.

[0076] In the case of the two-layer anisotropic conductive film of Comparative Example 12, an organic peroxide with a one-minute half-life temperature of 142.0°C was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer, but since neither the conductive particle-containing layer nor the insulating resin layer contained non-conductive particles, the film was not evaluated favorably in any of the evaluation items of reaction rate, initial characteristics, and characteristics after storage.

[0077] In the case of the two-layer anisotropic conductive film of Comparative Example 13, an organic peroxide with a one-minute half-life temperature of 142.0°C was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer. However, the content of aluminum nitride particles, which are non-conductive particles with an average particle diameter of 2 μm, in the conductive particle-containing layer was 4%, which was below 5%, and therefore the film was not rated favorably for any of the evaluation items of the initial characteristics and the post-storage characteristics other than the post-storage adhesive strength.

[0078] In the case of the two-layer anisotropic conductive film of Comparative Example 14, an organic peroxide with a one-minute half-life temperature of 142.0°C was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer. However, the content of aluminum nitride particles, which are non-conductive particles with an average particle diameter of 2 μm, in the conductive particle-containing layer was 25%, which was higher than 24%, and therefore, the film was not rated favorably in any of the evaluation items of the initial characteristics and the characteristics after storage, except for the initial conductive resistance.

[0079] In the case of the two-layer anisotropic conductive film of Comparative Example 15, an organic peroxide with a one-minute half-life temperature of 142.0°C was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer, but zirconium oxide with a thermal conductivity of 3 W / m K, which is significantly lower than 30 W / m K, was used as a non-conductive particle in the conductive particle-containing layer, and therefore the film was not rated favorably in any of the evaluation items, namely, reaction rate, initial characteristics, and characteristics after storage.

[0080] In the case of the two-layer anisotropic conductive film of Comparative Example 16, an organic peroxide with a one-minute half-life temperature of 142.0°C was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer, but non-conductive particles were not contained in the conductive particle-containing layer, and only in the insulating resin layer. Therefore, the initial adhesive strength and adhesive strength after storage were not evaluated favorably.

[0081] In the case of the two-layer anisotropic conductive film of Comparative Example 17, an organic peroxide with a one-minute half-life temperature of 142.0°C was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer, but non-conductive particles were not used in the conductive particle-containing layer, and a small amount (2%) of non-conductive particles were used only in the insulating resin layer compared to Comparative Example 16. Therefore, the evaluation items of the reaction rate, initial characteristics, and characteristics after storage were not favorable.

[0082] The anisotropic conductive film of the present invention has a conductive particle-containing layer containing a film-forming resin, a radically polymerizable compound, a radical polymerization initiator, conductive particles, and a filler. In the present invention, an organic peroxide with a one-minute half-life temperature of 132°C or higher is used as the radical polymerization initiator, thereby improving the storage stability of the anisotropic conductive film. Furthermore, non-conductive particles with a thermal conductivity of 30 W / m·K or higher (significantly exceeding 10 W / m·K) are used as the filler in the conductive particle-containing layer at a concentration of 5% by mass to 24% by mass. This allows for efficient distribution of thermal energy throughout the anisotropic conductive film during anisotropic conductive connection, enabling anisotropic conductive connection even at relatively low temperatures not significantly exceeding the one-minute half-life temperature, and ensuring a reaction rate of 80% or higher. Furthermore, the average particle size of the non-conductive particles is equal to or smaller than the average particle size of the conductive particles, thereby preventing the conductive particles from being easily pushed into the anisotropic conductive connection. Therefore, the anisotropic conductive film of the present invention has no problems with its conductivity and adhesive strength immediately after production or after normal storage, and further with its conductivity and adhesive strength after a pressure cooker test, and is therefore useful for producing connection structures consisting of various electronic components.

[0083] REFERENCE SIGNS LIST 1, 21 conductive particle-containing layer 2, 22 conductive particles 3, 23 filler 24 insulating resin layer 10, 20 anisotropic conductive film

Claims

1. An anisotropic conductive film having a conductive particle-containing layer containing a film-forming resin, a radical polymerizable compound, a radical polymerization initiator, conductive particles, and a filler, wherein the radical polymerization initiator is an organic peroxide having a one-minute half-life temperature of 132°C or higher, the filler is non-conductive particles having a thermal conductivity of 30 W / m·K or higher and an average particle size equal to or smaller than the average particle size of the conductive particles, and the content of the non-conductive particles in the conductive particle-containing layer is 5% by mass or more and 24% by mass or less.

2. The anisotropic conductive film according to claim 1, wherein the organic peroxide has a one-minute half-life temperature of 135° C. or higher.

3. The anisotropic conductive film according to claim 1, wherein the organic peroxide has a one-minute half-life temperature of 140° C. or higher.

4. The anisotropic conductive film according to claim 1, wherein the organic peroxide is di-t-butylperoxyhexahydroterephthalate having a one-minute half-life temperature of 142.0°C.

5. The anisotropic conductive film according to claim 1 or 2, wherein an insulating resin layer is further laminated on the conductive particle-containing layer.

6. The anisotropic conductive film according to claim 5, wherein when the thickness of said insulating resin layer is greater than the thickness of said conductive particle-containing layer, said insulating resin layer does not contain said non-conductive particles.

7. The anisotropic conductive film according to claim 1 or 2, wherein said non-conductive particles are non-conductive nitrides.

8. The anisotropic conductive film according to claim 7, wherein said nitride is aluminum nitride.

9. A connection structure in which a first electronic component and a second electronic component are anisotropically conductively connected via the anisotropically conductive film according to claim 1.

10. A method for producing a connection structure, comprising sandwiching the anisotropic conductive film according to claim 1 between a first electronic component and a second electronic component, and then pressing the components together to achieve an anisotropic conductive connection.

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