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

Abstract

To provide an anisotropic conductive film formed from a radical polymerizable resin composition containing an organic peroxide as a radical polymerization initiator, in which even when an organic peroxide with a 1-minute half-life temperature of 120°C or higher is used as the radical polymerization initiator from the viewpoint of storage stability, the low-temperature rapid curing properties are not impaired, the reaction rate after anisotropic conductive connection does not fall below 80%, and problems do not occur in the conductive properties and adhesive strength of the anisotropic conductive film.SOLUTION: In an anisotropic conductive film having a conductive particle-containing layer that contains a film-forming resin, a radical polymerizable compound, a radical polymerization initiator, conductive particles, and a filler, an organic peroxide with a one-minute half-life temperature of 132°C or more is used as the radical polymerization initiator, and non-conductive particles with a thermal conductivity of 30 W / m K or more and an average particle size equal to or smaller than the average particle size of the conductive particles are used as the filler in an amount of 5 mass% or more and 24 mass% or less in the conductive particle-containing layer.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] As a connection material for electronic components, an anisotropic conductive film having a conductive particle-containing layer formed by dispersing or regularly arranging conductive particles in an insulating resin layer is widely used. As such an anisotropic conductive film, from the viewpoint of curing at low temperature for a short time (low-temperature rapid curability), a film-forming resin such as phenoxy resin, conductive particles, a radically polymerizable compound such as (meth)acrylates, and an organic peroxide having a half-life temperature of less than 120°C for 1 minute as a radical polymerization initiator are used. A film formed from a resin composition containing the above is used.

[0003] However, an anisotropic conductive film using an organic peroxide having a half-life temperature of less than 120°C for 1 minute has a problem of reduced storage stability. To solve this problem, if an organic peroxide having a half-life temperature of 120°C or higher for 1 minute is used as a radical polymerization initiator for the anisotropic conductive film, the storage stability of the anisotropic conductive film can be improved, but there may be a problem of "reduction in low-temperature rapid curability of the anisotropic conductive film" occurring reflexively. Therefore, in order to solve such a problem, it has been proposed to incorporate non-conductive particles having a thermal conductivity of 10 W / m·K or higher into the anisotropic conductive film (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technology of Patent Document 1, it may not be possible to achieve the same level of low-temperature rapid curability as when an organic peroxide with a half-life temperature of less than 120 °C is used in the anisotropic conductive film. In addition, there is a concern that the reaction rate of the anisotropic conductive film after pressure bonding (after anisotropic conductive connection) may not reach 80% or more, which may have an adverse effect on the conduction characteristics and adhesive strength.

[0006] An object of the present invention is to solve the conventional problems. Regarding 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 (meth)acrylates, and an organic peroxide as a radical polymerization initiator, from the viewpoint of storage stability, even when an organic peroxide with a half-life temperature of 120 °C or higher is used as the radical polymerization initiator, it exhibits low-temperature rapid curability comparable to that when an organic peroxide with a half-life temperature of less than 120 °C is used. Also, the reaction rate after anisotropic conductive connection does not fall below 80%, so that there are no problems with the conduction characteristics and adhesive strength of the anisotropic conductive film.

Means for Solving the Problems

[0007] The present inventors have found that 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, as the radical polymerization initiator, an organic peroxide with a half-life temperature of 132 °C or higher, which is even higher than 120 °C, is used, and as the filler, non-conductive particles having a thermal conductivity of 30 W / m·K or higher, which greatly exceeds 10 W / m·K, and an average particle diameter equal to or smaller than the average particle diameter of the conductive particles are used in a specific amount range, whereby the above object of the present invention can be achieved, and the present invention has been completed.

[0008] That is, the present invention relates to 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 half-life temperature of 132 °C or higher, The filler is a non-conductive particle having a thermal conductivity of 30 W / m·K or more and an average particle diameter equal to or less than the average particle diameter of the conductive particles, and provides an anisotropic conductive film in which 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. Further, the present invention provides a method for manufacturing a connection structure in which an anisotropic conductive connection is made by sandwiching and pressing the anisotropic conductive film of the present invention between a first electronic component and a second electronic component.

Advantages of the Invention

[0010] The anisotropic conductive film of the present invention having a conductive particle-containing layer containing a film-forming resin, a radically polymerizable compound, a radical polymerization initiator, conductive particles, and a filler uses, as the radical polymerization initiator, an organic peroxide having a half-life temperature of 132° C. or more in one minute. For this reason, the storage stability is improved. Further, as the filler, non-conductive particles having a thermal conductivity of more than 10 W / m·K and 30 W / m·K or more are used so as to be 5% by mass or more and 24% by mass or less in the conductive particle-containing layer. For this reason, during anisotropic conductive connection, thermal energy can be efficiently distributed throughout the anisotropic conductive film, and anisotropic conductive connection can be performed at a relatively low temperature that does not greatly exceed the one-minute half-life temperature, and a reaction rate of 80% or more can be ensured. Moreover, since the average particle diameter of the non-conductive particles is equal to or less than the average particle diameter of the conductive particles, the pushability of the conductive particles during anisotropic conductive connection is not impaired. Therefore, problems do not occur in the conduction resistance characteristics and adhesive strength not only immediately after the production of the anisotropic conductive film of the present invention but also after normal storage (for example, exposure storage in an environment of 30° C. and 60% RH), and further in the conduction characteristics and adhesive strength after their pressure cooker tests.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

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

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

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

[0015] (Film-Forming Resin) The conductive particle-containing layer 1 of the present invention preferably contains a phenoxy resin excellent in impact resistance as the 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, preferably 80,000 or less, and more preferably 60,000 or less. The weight average molecular weight can be measured by a normal gel permeation chromatography method.

[0016] If the content of the film-forming resin in the conductive particle-containing layer 1 is too small, the anisotropic conductive film is likely to bend. If it is too large, the fluidity of the resin during anisotropic conductive connection decreases, making it difficult to obtain good conductivity, and the flexibility also decreases, so the adhesive strength tends to be low. Therefore, it is preferably 20.0% by mass or more, more preferably 25.0% by mass or more, preferably 50.0% by mass or less, and more preferably 35.0% by mass or less.

[0017] Such phenoxy resins can be selected and used from known phenoxy resins. Generally, they are epoxy group-free polyhydroxy polyethers (thermoplastic resins) synthesized from bisphenols and epichlorohydrin. From the perspective of easy availability, bisphenol A can be preferably cited as the bisphenol component.

[0018] Note that as long as the effects of the present invention are not impaired, the conductive particle-containing layer 1 of the present invention can contain general film-forming components other than phenoxy resins, such as epoxy resins, polyester resins, urethane resins, butadiene resins, polyamide resins, polyimide resins, polyolefin resins, polyvinyl butyral resins, ethylene vinyl acetate copolymer resins, etc.

[0019] (Radical polymerizable compound) The conductive particle-containing layer 1 of the present invention preferably contains, as radical polymerizable compounds, monofunctional (meth)acrylates such as known alkyl (meth)acrylates, polyfunctional (meth)acrylates such as polypropylene glycol di(meth)acrylate, and acrylic compounds such as urethane (meth)acrylate. Among them, from the viewpoint of improving the adhesion to polyimide of a flexible printed circuit board (FPC) in order to improve the cohesion of the cured product and the conduction reliability, urethane (meth)acrylate, which is a reaction product of hydroxyalkyl (meth)acrylates and diisocyanates, can be preferably cited. These acrylic compounds may be monomers, oligomers or polymers. Note that polyfunctional (meth)acrylates can also function as crosslinking agents, and isocyanuric acid EO-modified di- or tri(meth)acrylate can be cited as a preferred crosslinking agent. Note that (meth)acrylate is a term meaning both acrylate and methacrylate.

[0020] If the content of the radically polymerizable compound in the conductive particle-containing layer 1 is too small, there is a concern that the cohesive force of the conductive particle-containing layer 1 will weaken and the desired adhesive strength of the anisotropic conductive film cannot be achieved. If it is too large, the liquid component will relatively increase, the conductive particle-containing layer 1 itself will become soft, and there is a concern that it will adhere to the slit blade when the anisotropic conductive film is slit. Therefore, it is preferably 20.0% by mass or more, more preferably 30.0% by mass or more, preferably 50.0% by mass or less, and more preferably 40.0% by mass or less. As long as the effects of the present invention are not impaired, a radically polymerizable component other than the acrylic compound, for example, an alkene compound, can be contained.

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

[0022] Specific examples of the organic peroxide (half-life temperature for 1 minute) are shown below. * 1,1,3,3-Tetramethylbutyl peroxy-2-ethylhexanoate (124.3°C) * Dibenzoyl peroxide (130.0°C) * Di(3-methylbenzoyl)peroxide, benzoyl(3-methylbenzoyl)peroxide and dibenzoyl peroxide mixture (131.1°C) * Disuccinic peroxide (131.8°C) * t-Hexyl peroxy-2-ethylhexanoate (132.6°C) * t-Butyl peroxy-2-ethylhexanoate (134.0°C) * Di-t-butyl peroxyhexahydroterephthalate (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-Butylperoxybenzoate (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 - mentioned organic peroxides, di - t - butyl peroxyhexahydroterephthalate (142.0 °C) can be preferably used because good characteristics such as conductivity and adhesiveness can be obtained even when pressure - bonding is carried out under low - temperature conditions 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 radically polymerizable compound increases, the adhesiveness of the conductive particle - containing layer 1 decreases, and the push - in property of the conductive particles decreases. On the contrary, if it is too large, the average molecular weight of the polymer of the radically polymerizable compound decreases, and the impact resistance of the conductive particle - containing layer 1 tends to decrease. Therefore, it 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, with respect to 100 parts by mass of the radically polymerizable compound.

[0025] (Conductive particles) The conductive particle - containing layer 1 contains conductive particles 2 in order to impart anisotropic conductivity to the anisotropic conductive film 10. As the conductive particles 2, the same known conductive particles used in general anisotropic conductive films can be used. For example, metal particles, alloy particles, metal - coated resin particles, etc. can 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 small, and if it is too large, the insulation reliability between wirings tends to deteriorate. Therefore, it is preferably 1.5 μm or more, more preferably 2.0 μm or more, and preferably not more than the thickness of the conductive particle - containing layer, more preferably 5.0 μm or less. This average particle diameter can be measured by a commercially available particle size distribution measuring device using the laser diffraction / scattering method.

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

[0028] The conductive particles 2 may be randomly dispersed and held in the conductive particle-containing layer 1, or may be regularly arranged by a known method, for example, in a lattice pattern. Further, 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 plan view of the film. Note that if the number density of the conductive particles in a plan view of the film is too low, it is difficult to capture the particles on the terminals, and there is a possibility that it will not be possible to cope with the narrowing of the bezel of the image display device or the fine pitch of the electrodes of the circuit board. If it is too high, the insulation reliability between the wirings tends to decrease. Therefore, it is preferably 3,500 particles / mm 2 or more, more preferably 5,000 particles / mm 2 or more, and preferably 25,000 particles / mm 2 or less, more preferably 20,000 particles / mm 2 or less.

[0029] (Filler) In order to improve the decrease in low-temperature rapid curability due to the use of an organic peroxide having a half-life temperature of 132°C or higher for 1 minute 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. There is a concern that non-conductive particles with a thermal conductivity of less than 30 W / m·K cannot improve the reaction rate in the conductive particle-containing layer 1 to 80% or more during heating at the time of anisotropic conductive connection.

[0030] In addition, the average particle diameter of the non-conductive particles is equal to or less than the average particle diameter of the conductive particles 2, preferably 30% or more and 70% or less. If it becomes larger than the average particle diameter of the conductive particles 2, it becomes difficult to obtain good conduction characteristics. The average particle diameter of the non-conductive particles can be measured by a commercially available particle diameter distribution measuring device using the laser diffraction / scattering method.

[0031] As such non-conductive particles, those having a thermal conductivity of 30 W / m·K or more and an average particle diameter equal to or less than the average particle diameter of the conductive particles 2 can be appropriately selected. Examples of such non-conductive particles include non-conductive nitrides and carbides, preferably metal nitrides, metal carbides, etc. Specifically, aluminum nitride (320 W / m·K), silicon carbide (270 W / m·K), etc. can be mentioned. Particularly preferred non-conductive particles are aluminum nitride in terms of high thermal conductivity and low acquisition cost.

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

[0033] Similar to the conductive particles 2, the non-conductive particles may be randomly dispersed and held in the conductive particle-containing layer 1, or may be regularly arranged by a known method, for example, in a lattice pattern. Further, 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 be held so as not to overlap in the film thickness direction in a plan view of the film. Note that if the number density of the non-conductive particles in a plan view of the film is too low, electrical connection becomes difficult, and if it is too high, there is a tendency for an electrical short circuit to occur between adjacent wirings. Therefore, it is preferably 100 particles / mm 2 or more, more preferably 4000 particles / mm 2 or more, preferably 20000 particles / mm 2 or less, more preferably 12000 particles / mm 2 or less.

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

[0035] (Layer thickness of the conductive particle-containing layer) Regarding the layer thickness of the conductive particle-containing layer 1 constituting the anisotropic conductive film of the present invention, if it is too thin, it is difficult to obtain sufficient adhesive strength, and if it is too thick, there is a tendency that a stable slit cannot be formed. Therefore, it is preferably 10 μm or more, more preferably 15 μm or more, preferably 25 μm or less, and more preferably 20 μm or less.

[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 as necessary. The release base film can function as a film on which the composition for forming the conductive particle-containing layer is applied when the conductive particle-containing layer 1 is formed. Also, a release base film may be provided as a cover film on the opposite surface of the conductive particle-containing layer 1. As such a release base film, a known release base film applied to a normal anisotropic conductive film can be adopted. For example, a polyethylene terephthalate film subjected to a silicone release treatment can be used as the release base film.

[0037] <<Anisotropic conductive film with the laminated structure of 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 radically polymerizable compound, a radical polymerization initiator, conductive particles 22, and a filler, similar to the anisotropic conductive film having a single-layer structure in FIG. 1.

[0038] The insulating resin layer 24 is a layer that flows during anisotropic conductive connection to fill the space between the opposing objects to be connected and firmly bond them, and is a layer that does not contain conductive particles. The insulating resin layer 24 can be composed of a film-forming resin, a radically polymerizable compound, a radical polymerization initiator, and a filler, as described for the anisotropic conductive film in FIG. 1.

[0039] Also, if the layer thickness of the insulating resin layer 24 is too thin, the resin filling in the mounting part will be insufficient, and if it is too thick, it will prevent the pushing-in of the mounting part. Therefore, it is preferably 4 μm or more, more preferably 6 μm or more, preferably 20 μm or less, and more preferably 10 μm or less.

[0040] In addition, when the layer thickness of the insulating resin layer 24 is thicker than that of the conductive particle-containing layer 21, there is a concern that the pushability will deteriorate due to an increase in viscosity. Therefore, it is preferable that the insulating resin layer 24 does not contain non-conductive particles.

[0041] <<Manufacture of Anisotropic Conductive Film>> The anisotropic conductive film of FIG. 1 can be manufactured by uniformly mixing a film-forming resin, a radically polymerizable compound, a radical polymerization initiator, conductive particles, and a filler, and, if necessary, a general-purpose solvent to obtain a composition for forming a conductive particle-containing layer, and applying the composition to one side of a release base film such as a release-treated polyethylene terephthalate film by a conventional method, for example, a bar coater, and drying to form a conductive particle-containing layer. Similarly, the anisotropic conductive film of FIG. 2 is obtained by uniformly mixing a film-forming resin, a radically polymerizable compound, a radical polymerization initiator, and a filler, and, if necessary, a general-purpose solvent to obtain a composition for forming an insulating resin layer, applying the composition to one side of another release base film by a conventional method, and drying to form an insulating resin layer. Next, the conductive particle-containing layer and the insulating resin layer are laminated with each other facing each other, and an anisotropic conductive film having a laminated structure of release base film / conductive particle-containing layer / insulating resin layer / release base film (cover film) can be manufactured.

[0042] The anisotropic conductive film of the present invention thus manufactured can be slit into narrow widths and then wound around a reel and distributed as a wound body. The film length in such a wound body is preferably 5 m or more, more preferably 50 m or more, preferably 5000 m or less, and more preferably 1000 m or less from the viewpoint of practicality. Further, the release force between the insulating resin layer 24 and the release base film in the anisotropic conductive film of the present invention is preferably 200 to 400 mN / 5 cm, more preferably 250 to 350 mN / 5 cm by a T-type release test according to JIS K 6854. If it is below this range, the anisotropic conductive film tends to float from the release base film during slitting and blocking tends to occur. If it exceeds this range, when using the anisotropic conductive film, the anisotropic conductive film tends to be difficult to stick to glass.

[0043] <<Applications of Anisotropic Conductive Film>> The anisotropic conductive film of the present invention can be preferably applied when anisotropically conducting connection between a first electronic component such as an FPC, an IC chip, and an IC module and a second electronic component such as an FPC, a rigid substrate, a ceramic substrate, a glass substrate, and a plastic substrate. The connection structure thus obtained, that is, the connection structure in which the first electronic component and the second electronic component are anisotropically conductively connected via the anisotropic conductive film of the present invention is also a part of the present invention. Further, a method for manufacturing 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 anisotropically conductive connection is performed by pressure bonding, is also a part of the present invention.

Example

[0044] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

[0045] Regarding the composition for forming a conductive particle-containing layer and the composition for forming an insulating resin layer prepared in the following Examples and Comparative Examples, the product names and sources of the resin composition components shown in Table 1 (anisotropic conductive film with a single-layer structure) and Table 2 (anisotropic conductive film 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 acrylate oligomer: Aronix M-1600, Toagosei Co., Ltd. * Rubber component: SG80H, Nagase ChemteX Corporation * Phosphoric acid acrylic monomer: Light Ester P-1M, Kyoeisha Chemical Co., Ltd. * Radical polymerization initiator 1: Perkadox 62-W65, Kayaku Nouryon Co., Ltd. (half-life temperature for 1 minute: 142.0 °C) * Radical polymerization initiator 2: Peroyl L, NOF Corporation (half-life temperature for 1 minute: 116.4 °C) * Radical polymerization initiator 3: Niper BMТ-K40, NOF Corporation (half-life temperature for 1 minute: 131.0 °C) *Conductive particles: Ni / Au-plated acrylic resin particles, Nippon Kagaku Kogyo Co., Ltd., average particle diameter 3 μm *Aluminum nitride 1: Thermal conductivity 320 W / m·K, average particle diameter 2 μm *Aluminum nitride 2: Thermal conductivity 320 W / m·K, average particle diameter 5 μm *Boron nitride: Thermal conductivity 30 W / m·K, average particle diameter 1.7 μm *Zirconium oxide: Thermal conductivity 3 W / m·K, average particle diameter 0.01 μm

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

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

[0049]

Table 1

[0050]

Table 2

[0051] <Examples 1 to 5, Comparative Examples 1 to 8> (Creation of an anisotropic conductive film with a single-layer structure) The composition for forming a conductive particle-containing layer in Table 1 was applied using a bar coater onto a 25-μm-thick polyethylene terephthalate release base film having a silicone release-treated surface so as to have a dry thickness of 10 ± 0.5 μm, and dried in an oven at 55°C for 3 minutes to form a conductive particle-containing layer on the release base film. A general cover film was laminated onto the exposed surface of the conductive particle-containing layer at 45°C 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> (Fabrication of an anisotropic conductive film with a two-layer structure) · Formation of a conductive particle-containing layer The composition for forming a conductive particle-containing layer in Table 2 was applied using a bar coater onto a 25-μm-thick polyethylene terephthalate release base film having a silicone release-treated surface so as to have a dry thickness of 4 ± 0.5 μm, and 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 an insulating resin layer The composition for forming an insulating resin layer in Table 2 was applied using a bar coater onto a 50-μm-thick polyethylene terephthalate release base film having a silicone release-treated surface so as to have a dry thickness of 6 ± 0.5 μm, and dried in an oven at 70°C for 4 minutes to form an insulating resin layer on the release base film.

[0054] · Fabrication of an anisotropic conductive film The obtained insulating resin layer and the conductive particle-containing layer were opposed to each other and laminated under the 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> For the anisotropic conductive films of the examples and comparative examples, the "reaction rate", initial characteristics (specifically, "initial conduction resistance", "conduction resistance after PCT (85°C, 85% RH, 500 Hr)", "adhesion strength"), and characteristics after storage (30°C, 60% RH, 48 Hr) (specifically, "conduction resistance after storage", "conduction resistance after PCT after storage", "adhesion strength after storage") were tested or inspected and evaluated as described below. The obtained results are shown in Table 3 for the anisotropic conductive film with a single-layer structure and in Table 4 for the anisotropic conductive film with a two-layer structure.

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

[0057] (Initial characteristics) 1. Initial conduction resistance · Conduction resistance after PCT Each anisotropic conductive film prepared in the examples and comparative examples was cut into strips with 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 adhered to the edge of a SiN glass substrate (0.7 mm thick) on which an indium zinc oxide transparent electrode was formed, placed on a hot plate at 45 °C, and uniformly pressed from the release base film side of the insulating resin layer. Then, the release base film was released, and the metal wiring portion of the FPC (thickness 50 μm) for evaluation was bonded so that the exposed conductive particle-containing layer or the insulating resin layer side was completely covered. Further, a crimping tool head with a width of 1.5 mm and a length of 60 mm was used to thermocompression bond (135 °C, 3 MPa, 10 seconds) the FPC and the glass substrate through a 0.15 mm thick Teflon (registered trademark) film, thereby joining the opposing electrodes of the FPC and the glass substrate with a cured product of the anisotropic conductive film. Thus, a connection structure with anisotropic conductive connection was obtained. 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 obtained connection structure was measured by the four-terminal method immediately after manufacturing the connection structure (initial). Practically, it is preferably 3 Ω or less. Also, from the viewpoint of connection reliability, the connection structure was subjected to a pressure cooker test (PCT) in which it was held in a thermostatic and humid chamber (85 °C, 85% RH) for 500 hours, and the conduction resistance after PCT was measured by the four-terminal method after the test. Practically, it is preferably 4 Ω or less.

[0059] 2. Initial Adhesion Strength Similar to the case of the initial conduction resistance test, a connection structure was obtained by anisotropically conducting the connection between the glass substrate and the FPC using each anisotropic conductive film prepared in the examples and comparative examples. However, as the FPC, instead of using one with a specification of 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), one with a specification of a polyimide film thickness of 66 μm, a copper circuit thickness of 20 μm, and a copper circuit line width of 60 μm (pitch 120 μm, L / S = 1 / 1) was used.

[0060] The obtained connection structure including the FPC for evaluation was cut at a width of 1 cm, and using a tensile tester (RTC1201, A&D Company, Limited), the adhesive strength was measured when the FPC for evaluation was pulled up at an angle of 90° and a speed of 50 mm / second. Practically, it is preferably 6.5 N / cm or more.

[0061] (Properties after storage) 3. Conduction resistance after storage, conduction resistance after PCT, adhesive strength after storage Each anisotropic conductive film prepared in the examples and comparative examples was stored in a thermo-hygrostat at 30 °C and 60% Rh for 48 hours. Using the anisotropic conductive film after storage, the same connection structure as that created during the evaluation of the initial characteristics was created, and similar to the initial characteristics, the conduction resistance after storage, the conduction resistance after PCT, and the initial adhesive strength after storage were measured. Practically, preferably, the conduction resistance after storage is 3 Ω or less, the conduction resistance after PCT is 4 Ω or less, and the initial adhesive strength after storage is 4 N / cm or more.

[0062] [Table 3]

[0063] [Table 4]

[0064] (Consideration of evaluation results) In the anisotropic conductive films of Examples 1 to 9, an organic peroxide having a half-life temperature of 142.0 °C for 1 minute was used as a radical polymerization initiator. Moreover, as a filler, non-conductive aluminum nitride particles having a thermal conductivity of 30 W / m·K or more and an average particle diameter smaller than the average particle diameter of the conductive particles were contained in the conductive particle-containing layer at 5% by mass or more and 24% by mass or less. Therefore, it was possible to evaluate that it was preferable for practical use in any evaluation items of reaction rate, initial characteristics, and characteristics after storage. On the other hand, as will be described below, the anisotropic conductive films of Comparative Examples 1 to 17 could not be evaluated as preferable for practical use in any evaluation items of reaction rate, initial characteristics, or characteristics after storage.

[0065] In the case of the single-layer structure anisotropic conductive film of Comparative Example 1, since an organic peroxide having a half-life temperature of 116.4 °C for 1 minute was used as a radical polymerization initiator, the reactivity was relatively high, so there were no problems with the reaction rate and initial characteristics. However, since it did not contain non-conductive particles, any of the characteristics after storage was not preferably evaluated.

[0066] In the case of the single-layer structure anisotropic conductive film of Comparative Example 2, an organic peroxide having a half-life temperature of 131.0 °C for 1 minute was used as a radical polymerization initiator in the conductive particle-containing layer. However, since it did not contain non-conductive particles, any of the characteristics after storage was not preferably evaluated.

[0067] In the case of the single-layer structure anisotropic conductive film of Comparative Example 3, although the conductive particle-containing layer contained non-conductive particles, the reactivity of the organic peroxide having a half-life temperature of 131.0 °C for 1 minute used as a radical polymerization initiator was not sufficiently suppressed. Therefore, any of the characteristics after storage was not preferably evaluated.

[0068] In the case of the single-layer structure anisotropic conductive film of Comparative Example 4, although an organic peroxide having a half-life temperature of 142.0 °C for 1 minute was used as a radical polymerization initiator, since it did not contain non-conductive particles, any of the reaction rate, initial characteristics, and characteristics after storage was not preferably evaluated.

[0069] In the case of the anisotropic conductive film with a single-layer structure of Comparative Example 5, although an organic peroxide having a half-life temperature of 142.0 °C for 1 minute was used as a 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 is less than 5%. Therefore, none of the initial properties and properties after storage other than the adhesive strength after storage received favorable evaluations.

[0070] In the case of the anisotropic conductive film with a single-layer structure of Comparative Example 6, although an organic peroxide having a half-life temperature of 142.0 °C for 1 minute was used as a radical polymerization initiator, the average particle diameter of the aluminum nitride particles used as non-conductive particles was 5 μm which exceeds the average particle diameter of 3 μm of the conductive particles. Therefore, none of the initial properties and properties after storage received favorable evaluations.

[0071] In the case of the anisotropic conductive film with a single-layer structure of Comparative Example 7, although an organic peroxide having a half-life temperature of 142.0 °C for 1 minute was used as a 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 is more than 24%. Therefore, none of the initial properties and properties after storage received favorable evaluations.

[0072] In the case of the anisotropic conductive film with a single-layer structure of Comparative Example 8, although an organic peroxide having a half-life temperature of 142.0 °C for 1 minute was used as a radical polymerization initiator, zirconium oxide with a thermal conductivity of 3 W / m·K which is much lower than 30 W / m·K was used as the non-conductive particle. Therefore, none of the reaction rate, initial properties, and properties after storage received favorable evaluations.

[0073] In the case of the anisotropic conductive film with a two-layer structure of Comparative Example 9, an organic peroxide having a half-life temperature of 116.4 °C for 1 minute was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer. Therefore, there were no problems with the initial properties. However, since non-conductive particles were not contained in both the conductive particle-containing layer and the insulating resin layer, none of the properties after storage received favorable evaluations.

[0074] In the case of the anisotropic conductive film with a two-layer structure of Comparative Example 10, an organic peroxide with a half-life temperature of 131.0 °C for 1 minute was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer. However, since no non-conductive particles were contained in the conductive particle-containing layer, although there were no problems with the initial characteristics, none of the characteristics after storage received favorable evaluations.

[0075] In the case of the anisotropic conductive film with a two-layer structure of Comparative Example 11, non-conductive particles were contained in the conductive particle-containing layer. However, in both the conductive particle-containing layer and the insulating resin layer, the reactivity of the organic peroxide with a half-life temperature of 131.0 °C for 1 minute used as a radical polymerization initiator was not sufficiently suppressed, so none of the characteristics after storage received favorable evaluations.

[0076] In the case of the anisotropic conductive film with a two-layer structure of Comparative Example 12, an organic peroxide with a half-life temperature of 142.0 °C for 1 minute was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer. However, since no non-conductive particles were contained in both the conductive particle-containing layer and the insulating resin layer, none of the characteristics such as the reaction rate, initial characteristics, and characteristics after storage received favorable evaluations.

[0077] In the case of the anisotropic conductive film with a two-layer structure of Comparative Example 13, an organic peroxide with a half-life temperature of 142.0 °C for 1 minute was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer. However, since 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 is less than 5%, none of the initial characteristics and characteristics after storage other than the adhesive strength after storage received favorable evaluations.

[0078] In the case of the anisotropic conductive film with a two-layer structure of Comparative Example 14, although an organic peroxide with a half-life temperature of 142.0 °C for 1 minute was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer, since 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 exceeded 24% and was 25%, none of the characteristics of the initial characteristics and the characteristics after storage, excluding the initial conductive resistance, received favorable evaluations.

[0079] In the case of the anisotropic conductive film with a two-layer structure of Comparative Example 15, although an organic peroxide with a half-life temperature of 142.0 °C for 1 minute was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer, since zirconium oxide with a thermal conductivity of 3 W / m·K, which is much lower than 30 W / m·K, was used as non-conductive particles in the conductive particle-containing layer, none of the characteristics of the reaction rate, the initial characteristics, and the characteristics after storage received favorable evaluations.

[0080] In the case of the anisotropic conductive film with a two-layer structure of Comparative Example 16, although an organic peroxide with a half-life temperature of 142.0 °C for 1 minute was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer, since no non-conductive particles were contained in the conductive particle-containing layer and non-conductive particles were contained only in the insulating resin layer, none of the characteristics of the initial adhesive strength and the adhesive strength after storage received favorable evaluations.

[0081] In the case of the anisotropic conductive film with a two-layer structure of Comparative Example 17, although an organic peroxide with a half-life temperature of 142.0 °C for 1 minute was used as a radical polymerization initiator in both the conductive particle-containing layer and the insulating resin layer, since no non-conductive particles were used in the conductive particle-containing layer and a small amount (2%) of non-conductive particles was used only in the insulating resin layer compared to the case of Comparative Example 16, none of the characteristics of the initial characteristics and the characteristics after storage received favorable evaluations.

Industrial Applicability

[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, since an organic peroxide having a half-life temperature of 132°C or higher for 1 minute is used as the radical polymerization initiator, the storage stability of the anisotropic conductive film can be improved. Further, as the filler, non-conductive particles having a thermal conductivity of 30 W / m·K or higher, which greatly exceeds 10 W / m·K, are used in the conductive particle-containing layer at 5% by mass or more and 24% by mass or less. Therefore, during anisotropic conductive connection, thermal energy can be efficiently distributed throughout the anisotropic conductive film, and anisotropic conductive connection is possible even at a relatively low temperature that does not greatly exceed the 1-minute half-life temperature, and a reaction rate of 80% or more can be ensured. Moreover, since the average particle diameter of the non-conductive particles is equal to or smaller than the average particle diameter of the conductive particles, the push-in property of the conductive particles during anisotropic conductive connection is not impaired. Therefore, the anisotropic conductive film of the present invention does not cause problems in the conduction resistance characteristics and adhesive strength immediately after production or after normal storage, and further in the conduction characteristics and adhesive strength after the pressure cooker test thereof, and is useful for manufacturing connection structures composed of various electronic components.

Explanation of Signs

[0083] 1, 21 Conductive particle-containing layer 2, 22 Conductive particles 3, 23 Filler 24 Insulating resin layer 10, 20 Anisotropic conductive film

Claims

1. 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, the radical polymerization initiator is an organic peroxide having a half-life temperature of 132°C or higher for 1 minute, the filler is a non-conductive particle having a thermal conductivity of 30 W / m·K or higher and an average particle diameter equal to or smaller than the average particle diameter of the conductive particles, An anisotropic conductive film in which 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 half-life temperature of the organic peroxide for 1 minute is 135°C or higher.

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

4. The anisotropic conductive film according to claim 1, wherein the organic peroxide is ditert-butyl peroxyhexahydroterephthalate having a half-life temperature of 142.0°C for 1 minute.

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 layer thickness of the insulating resin layer is thicker than the layer thickness of the conductive particle-containing layer, the insulating resin layer does not contain the non-conductive particles.

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

8. The anisotropic conductive film according to claim 7, wherein the 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 anisotropic conductive film according to claim 1.

10. A method for manufacturing a connection structure, in which the anisotropic conductive film according to claim 1 is sandwiched between a first electronic component and a second electronic component and pressure-bonded to perform anisotropic conductive connection.

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