Adhesive film for circuit connection, circuit connection structure, and method for manufacturing the same.

Abstract

Disclosed is an adhesive film for circuit connection which includes an electroconductive-particle layer comprising electroconductive particles, a cationically polymerizable compound, and an initiator for thermal cationic polymerization. The electroconductive-particle layer contains, as the cationically polymerizable compound, a compound having an alicyclic epoxy structure and an oxetane ring structure in the molecule.

Description

[Technical Field]

[0001] This disclosure relates to an adhesive film for circuit connection, a circuit connection structure, and a method for manufacturing the same. [Background technology]

[0002] Conventionally, various adhesive materials have been used for circuit connections. For example, a circuit connection adhesive film in which conductive particles are dispersed in the adhesive has been used as an adhesive material for connecting a liquid crystal display to a liquid crystal driving integrated circuit, a liquid crystal display to a tape carrier package (TCP), a flexible printed circuit board (FPC) to a TCP, or an FPC to a printed circuit board (see, for example, Patent Documents 1 and 2).

[0003] In recent years, in the field of precision electronic equipment where adhesive films for circuit connections are used, the density of circuits has been increasing, resulting in extremely narrow electrode widths and spacings. Therefore, adhesive films for circuit connections are required to efficiently capture conductive particles on minute electrodes to achieve high connection reliability. Furthermore, to reduce costs, it is necessary to improve throughput, and adhesive films for circuit connections that can be cured at low temperatures (100-170°C) are required. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2005 / 054388 [Patent Document 2] Japanese Patent Publication No. 2017-214472 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Incidentally, according to the inventors' studies of this disclosure, it has been found that conventional adhesive films for circuit connections may exhibit phenomena such as decreased adhesiveness and difficulty in achieving low-temperature curing when left for a long period (e.g., 3 days or more) at room temperature (25°C) under conditions of exposure to air and visible light. When such phenomena occur, the adhesive film becomes less effective as an adhesive film for circuit connections.

[0006] Therefore, the main objective of this disclosure is to provide an adhesive film for circuit connections that can maintain adhesiveness and low-temperature curing properties over a long period of time and can be used to manufacture circuit connection structures with high connection reliability. [Means for solving the problem]

[0007] One aspect of this disclosure relates to an adhesive film for circuit connections. This adhesive film for circuit connections comprises a conductive particle layer containing conductive particles, a cationic polymerizable compound, and a thermal cationic polymerization initiator. The conductive particle layer contains a compound having both an alicyclic epoxy structure and an oxetane ring structure in its molecule as the cationic polymerizable compound. The inventors of this disclosure have found that by containing a compound having both an alicyclic epoxy structure and an oxetane ring structure in its molecule as the cationic polymerizable compound, the adhesive properties and low-temperature curing properties can be maintained over a long period of time. Furthermore, according to the adhesive film for circuit connections, by containing a compound having both an alicyclic epoxy structure and an oxetane ring structure in its molecule as the cationic polymerizable compound, it is possible to manufacture a circuit connection structure with high connection reliability.

[0008] Compounds having an alicyclic epoxy structure and an oxetane ring structure within the molecule may be compounds represented by the following formula (I-1).

[0009] [ka]

[0010] The conductive particle layer of the circuit connection adhesive film may further contain, as a cationic polymerizable compound, a compound having an alicyclic epoxy structure within the molecule and not having an oxetane ring structure, or a compound having an oxetane ring structure within the molecule and not having an alicyclic epoxy structure. By further using these compounds as cationic polymerizable compounds, it becomes possible to manufacture a circuit connection structure with superior connection resistance in the circuit connection adhesive film.

[0011] Another aspect of this disclosure relates to a circuit connection structure. The circuit connection structure comprises a first circuit member having a first electrode, a second circuit member having a second electrode, and a circuit connection portion disposed between the first circuit member and the second circuit member and electrically connecting the first electrode and the second electrode to each other. The circuit connection portion includes a cured product of the above-mentioned adhesive film for circuit connection.

[0012] Another aspect of this disclosure relates to a method for manufacturing a circuit connection structure. The method for manufacturing the circuit connection structure includes the steps of interposing the above-mentioned circuit connection adhesive film between a first circuit member having a first electrode and a second circuit member having a second electrode, and then heat-pressing the first circuit member and the second circuit member together to electrically connect the first electrode and the second electrode. [Effects of the Invention]

[0013] This disclosure provides an adhesive film for circuit connections that can maintain adhesive properties and low-temperature curing properties over a long period of time and can be used to manufacture circuit connection structures with high connection reliability. Furthermore, this disclosure provides a circuit connection structure using such an adhesive film and a method for manufacturing the same. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a schematic cross-sectional view showing one embodiment of an adhesive film for circuit connection. [Figure 2]FIG. 2 is a schematic cross-sectional view showing an embodiment of a method for manufacturing a circuit connection structure. FIGS. 2(a) and 2(b) are schematic cross-sectional views showing each step.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiments.

[0016] In this specification, a numerical range indicated by "~" means a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described step by step in this specification, the upper limit value or the lower limit value of a certain step may be replaced by the upper limit value or the lower limit value of another step. Also, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced by the value shown in the examples. Further, the individually described upper limit value and lower limit value can be arbitrarily combined. In the notation of the numerical range "A~B", the numerical values A and B at both ends are included in the numerical range as the lower limit value and the upper limit value, respectively. In this specification, for example, the description "10 or more" means "10" and "numerical values exceeding 10", and the same applies when the numerical values are different. Also, for example, the description "10 or less" means "10" and "numerical values less than 10", and the same applies when the numerical values are different. Also, in this specification, "(meth)acrylate" means at least one of acrylate and the corresponding methacrylate. The same applies to other similar expressions such as "(meth)acryloyl". Also, "(poly)" means both cases with and without the prefix "poly". Also, "A or B" means that either A or B may be included, and both may be included. Also, the materials exemplified below may be used alone or in combination of two or more, unless otherwise specified. The content of each component in the composition means the total amount of the plurality of substances corresponding to each component in the composition, unless otherwise specified when there are a plurality of substances corresponding to each component in the composition.

[0017] [Adhesive Film for Circuit Connection] FIG. 1 is a schematic cross-sectional view showing an embodiment of an adhesive film for circuit connection. As shown in FIG. 1, the adhesive film 10 for circuit connection (hereinafter sometimes simply referred to as "adhesive film 10") includes a conductive particle layer 3 containing conductive particles 1 (hereinafter sometimes referred to as "(A) component") and an adhesive component 2 (hereinafter sometimes referred to as "(B) component") for dispersing the conductive particles 1. The adhesive component 2 in the conductive particle layer 3 is defined as a solid content other than the conductive particles 1.

[0018] In the adhesive film 10, the conductive particles 1 are dispersed in the conductive particle layer 3. Therefore, the adhesive film 10 can be an anisotropic conductive adhesive film for circuit connection (anisotropic conductive adhesive film). The adhesive film 10 may be interposed between a first circuit member having a first electrode and a second circuit member having a second electrode, and the first circuit member and the second circuit member may be thermocompression bonded to electrically connect the first electrode and the second electrode to each other.

[0019] <(A) Component: Conductive Particle> (A) component is not particularly limited as long as it is a conductive particle, and may be metal particles composed of metals such as Au, Ag, Pd, Ni, Cu, solder, or conductive carbon particles composed of conductive carbon. (A) component may be a coated conductive particle including a core containing non-conductive glass, ceramic, plastic (such as polystyrene), etc. and a coating layer containing the above metal or conductive carbon and covering the core. Among these, (A) component may be a coated conductive particle including a core containing a metal or plastic formed of a heat-melting metal and a coating layer containing a metal or conductive carbon and covering the core. Such coated conductive particles are easy to deform the cured product of the thermosetting resin component by heating or pressurization, so when electrically connecting electrodes, the contact area between the electrode and (A) component can be increased, and the conductivity between the electrodes can be further improved.

[0020] Component (A) may be insulating coated conductive particles comprising the above-mentioned metal particles, conductive carbon particles, or coated conductive particles, and an insulating layer comprising an insulating material such as resin that covers the surface of the particles. When component (A) is insulating coated conductive particles, even if the content of component (A) is high, the surface of the particles is covered with resin, so the occurrence of short circuits due to contact between components (A) can be suppressed, and the insulation between adjacent electrode circuits can also be improved. Component (A) may be used alone or in combination of multiple types.

[0021] (A) The maximum particle size of component (A) must be smaller than the minimum electrode spacing (the shortest distance between adjacent electrodes). From the viewpoint of excellent dispersibility and conductivity, the maximum particle size of component (A) may be 1.0 μm or more, 2.0 μm or more, or 2.5 μm or more. From the viewpoint of excellent dispersibility and conductivity, the maximum particle size of component (A) may be 20 μm or less, 10 μm or less, or 5 μm or less. In this specification, the particle size of any 300 conductive particles (pcs) is measured by observation using a scanning electron microscope (SEM), and the largest value obtained is taken as the maximum particle size of component (A). If component (A) has protrusions or is not spherical, the particle size of component (A) is taken as the diameter of the circle circumscribing the conductive particle in the SEM image.

[0022] The average particle size of component (A) may be 1.0 μm or larger, 2.0 μm or larger, or 2.5 μm or larger, from the viewpoint of excellent dispersibility and conductivity. The average particle size of component (A) may be 20 μm or smaller, 10 μm or smaller, or 5 μm or smaller, from the viewpoint of excellent dispersibility and conductivity. In this specification, the particle size of any 300 conductive particles (pcs) is measured by observation using a scanning electron microscope (SEM), and the average value of the obtained particle sizes is defined as the average particle size.

[0023] The content of component (A) may be 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more, based on the total amount of components (A) and (B), and may be 70% by mass or less, 60% by mass or less, 50% by mass or less, or 40% by mass or less, based on the total amount of components (A) and (B). When the content of component (A) is within the above range, the effects of this disclosure tend to be significantly more pronounced. The content of component (A) in the adhesive film (conductive particle layer) (based on the total mass of the adhesive film or conductive particle layer) may be the same as the above range.

[0024] <(B) component: adhesive component> Component (B) may be a thermosetting component that hardens when heated. Component (B) (or the conductive particle layer) may consist of a cationic polymerizable compound (hereinafter sometimes referred to as "component (B1)"), a thermal cationic polymerization initiator (hereinafter sometimes referred to as "component (B2)"), a thermoplastic resin (hereinafter sometimes referred to as "component (B3)"), a coupling agent (hereinafter sometimes referred to as "component (B4)"), a filler (hereinafter sometimes referred to as "component (B5)"), etc. Component (B) (or the conductive particle layer) contains at least components (B1) and (B2).

[0025] (B1) Component: Cationic polymerizable compound Component (B1) is a compound that crosslinks upon reaction with a cationic polymerization initiator (such as a thermal cationic polymerization initiator or a photocatalytic cationic polymerization initiator). Component (B) (or the conductive particle layer) contains, as component (B1), a compound having an alicyclic epoxy structure and an oxetane ring structure in its molecule (hereinafter sometimes referred to as "component (B1a)"). By containing component (B1a) as component (B1) in component (B) (or the conductive particle layer), the adhesive film for circuit connections can maintain its adhesiveness and low-temperature curing properties over a long period of time, and furthermore, it becomes possible to manufacture a circuit connection structure with high connection reliability.

[0026] Component (B1a) can be used without particular limitations as long as it is a compound having one or more alicyclic epoxy structures and one or more oxetane ring structures in its molecule. Component (B1a) can also be defined as a compound having one or more groups obtained by removing one or more hydrogen atoms from an alicyclic epoxy compound, and one or more groups obtained by removing one or more hydrogen atoms from an oxetane, in its molecule. Here, the alicyclic epoxy structure may be an epoxycyclohexane (cyclohexene oxide) structure. Component (B1a) may also be a compound having two alicyclic epoxy structures and one oxetane ring structure in its molecule. These may be used individually or in combination.

[0027] Component (B1a) may be, for example, a compound represented by general formula (I).

[0028] [ka]

[0029] In general formula (I), R 1 , R 2 , R 3 , and R 4 Each of these independently represents a hydrogen atom or a methyl group, and m and n independently represent 1 or 2.

[0030] Component (B1a) may be, for example, a compound represented by formula (I-1) (3,3-bis[(3,4-epoxycyclohexyl-1-methoxy)methyl]oxetane).

[0031] [ka]

[0032] The following compounds are examples of components (B1a) other than those represented by the general formula (I-1).

[0033] [ka]

[0034] The content of component (B1a) may be 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more, based on the total amount of component (B1), and may be 100% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less. When the content of component (B1a) is within the above range, the effects of this disclosure tend to be significantly exhibited.

[0035] Component (B) (or the conductive particle layer) is superior in terms of adhesiveness, long-term maintenance of low-temperature curing properties, and connection reliability, and therefore may further contain as component (B1) a compound having an alicyclic epoxy structure in the molecule but not an oxetane ring structure (hereinafter sometimes referred to as "component (B1b)"), or a compound having an oxetane ring structure in the molecule but not an alicyclic epoxy structure (hereinafter sometimes referred to as "component (B1c)"). Among these, it is preferable that component (B) (or the conductive particle layer) further contains component (B1c) as component (B1).

[0036] Component (B1b) can be used without particular limitations as long as it has one or more (preferably two or more) alicyclic epoxy structures within the molecule and does not have an oxetane ring structure. Examples of commercially available components of (B1b) include CEL2021P and CEL8010 (trade names, manufactured by Daicel Corporation). These may be used individually or in combination.

[0037] Component (B1c) can be used without particular limitations as long as it is a compound having one or more (preferably two or more) oxetane ring structures within the molecule and not having an alicyclic epoxy structure. Examples of commercially available components of (B1c) include ETERNACOLL OXBP (trade name, manufactured by Ube Industries, Ltd.), OXSQ, OXT-121, OXT-221, OXT-101, and OXT-212 (trade names, manufactured by Toagosei Co., Ltd.). These may be used individually or in combination.

[0038] The total content of component (B1b) and component (B1c) may be 0% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more, based on the total amount of component (B1), and may be 95% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less. When the total content of component (B1b) and component (B1c) is within the above range, the effects of this disclosure tend to be significantly more pronounced.

[0039] Component (B) (or conductive particle layer) may further contain, as component (B1), compounds other than components (B1a), (B1b), and (B1c) (hereinafter sometimes referred to as "component (B1d)"). Examples of component (B1d) include compounds that have an oxirane ring structure other than an alicyclic epoxy structure in their molecule and do not have an oxetane ring structure.

[0040] Examples of component (B1d) include bisphenol-type epoxy resins derived from epichlorohydrin and bisphenol compounds such as bisphenol A, bisphenol F, and bisphenol AD; epoxy novolac resins derived from epichlorohydrin and novolac resins such as phenol novolac or cresol novolac; and various epoxy compounds having two or more glycidyl groups in one molecule, such as glycidylamines, glycidyl ethers, biphenyls, and alicyclic compounds. These may be used individually or in combination.

[0041] (B1) component content ((total content of (B1a) component, (B1b) component, (B1c) component, and (B1d) component) may be 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more, and may be 60% by mass or less, 50% by mass or less, 45% by mass or less, or 40% by mass or less, based on the total amount of (A) component and (B) component, from the viewpoint of ensuring the curability of the adhesive film. When the content of (B1) component is within the above range, the effects of the present disclosure tend to be significantly exhibited. Note that the content of (B1) component in the adhesive film (conductive particle layer) (based on the total mass of the adhesive film or conductive particle layer) may be the same as the above range.

[0042] (B2) component: Thermal cationic polymerization initiator (B2) component is a thermal polymerization initiator that generates an acid or the like by heating to initiate polymerization. (B2) component may be a salt compound composed of a cation and an anion. (B2) component may be, for example, BF4 - , BR4 - (R represents a phenyl group substituted with two or more fluorine atoms or two or more trifluoromethyl groups.), PF6 - , SbF6 - , AsF6 - and the like, and examples include onium salts such as sulfonium salts, phosphonium salts, ammonium salts, diazonium salts, iodonium salts, anilinium salts, and pyridinium salts having anions. These may be used alone or in combination of a plurality.

[0043] (B2) component may be, from the viewpoint of storage stability, for example, a salt compound having an anion containing boron as a constituent element, that is, BF4 - or BR4 - (R represents a phenyl group substituted with two or more fluorine atoms or two or more trifluoromethyl groups.). The anion containing boron as a constituent element may be BR4 - and more specifically, may be tetrakis[tris(pentafluorophenyl)]borate.

[0044] The onium salt as component (B2) may be, for example, a quaternary ammonium salt, as it has resistance to substances that can inhibit cationic hardening.

[0045] Component (B2) may contain a quaternary ammonium salt, and may also contain a quaternary ammonium salt having a boron-containing anion as a constituent element. Examples of commercially available salt compounds of this type include CXC-1821 (trade name, manufactured by King Industries).

[0046] The content of component (B2) may be, for example, 1 to 40 parts by mass, 5 to 35 parts by mass, 10 to 30 parts by mass, or 15 to 25 parts by mass per 100 parts by mass of component (B1), from the viewpoint of ensuring the formation and curability of the adhesive film. When the content of component (B2) is within the above range, the effects of this disclosure tend to be significantly exhibited. The content of component (B2) in the composition or composition layer (based on the total mass of the composition or composition layer) may be the same as the above range.

[0047] (B3) Component: Thermoplastic resin Examples of component (B3) include phenoxy resin, polyester resin, polyamide resin, polyurethane resin, polyester urethane resin, acrylic rubber, epoxy resin (solid at 25°C), etc. These may be used individually or in combination. By further containing component (B3) in component (B), the film-forming properties can be improved. Among these, component (B3) may be, for example, phenoxy resin. The content of component (B3) may be 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more, and may be 60% by mass or less, 50% by mass or less, 45% by mass or less, or 40% by mass or less, based on the total amount of components (A) and (B). When the content of component (B3) is within the above range, the effects of this disclosure tend to be significantly exhibited. The content of component (B3) in the adhesive film (conductive particle layer) (based on the total mass of the adhesive film or conductive particle layer) may be the same as the above range.

[0048] (B4) Ingredients: Coupling agent Examples of component (B4) include silane coupling agents having organic functional groups such as (meth)acryloyl groups, mercapto groups, amino groups, imidazole groups, and epoxy groups; silane compounds such as tetraalkoxysilanes; tetraalkoxytitanate derivatives; and polydialkyltitanate derivatives. These may be used individually or in combination. The adhesion can be further improved by further containing component (B4) in component (B). Component (B4) may be, for example, a silane coupling agent. The content of component (B4) may be 0.1 to 10% by mass, based on the total amount of components (A) and (B). When the content of component (B4) is within the above range, the effects of this disclosure tend to be significantly exhibited. The content of component (B4) in the adhesive film (conductive particle layer) (based on the total mass of the adhesive film or conductive particle layer) may be the same as the above range.

[0049] (B5) Components: Filler Component (B5) may include, for example, non-conductive fillers (e.g., non-conductive particles). Component (B5) may be either an inorganic filler or an organic filler. Examples of inorganic fillers include metal oxide nanoparticles such as silica nanoparticles, alumina nanoparticles, silica-alumina nanoparticles, titania nanoparticles, and zirconia nanoparticles; and inorganic nanoparticles such as metal nitride nanoparticles. Examples of organic fillers include silicone nanoparticles, (meth)acrylate-butadiene-styrene nanoparticles, acrylic-silicone nanoparticles, polyamide nanoparticles, and polyimide nanoparticles. These may be used individually or in combination. The content of component (B5) may be 0.1 to 10% by mass, based on the total amount of components (A) and (B). When the content of component (B5) is within the above range, the effects of this disclosure tend to be significantly exhibited. The content of component (B5) in the adhesive film (conductive particle layer) (based on the total mass of the adhesive film or conductive particle layer) may be the same as the above range.

[0050] Component (B) may further contain other additives such as softeners, accelerators, degradation inhibitors, colorants, flame retardants, and thixotropic agents. The content of these other additives may be 0.1 to 10% by mass, based on the total amount of components (A) and (B). The content of other additives in the adhesive film (conductive particle layer) (based on the total mass of the adhesive film or conductive particle layer) may be in the same range as described above.

[0051] The content of component (B) may be 40% by mass or more, 50% by mass or more, 55% by mass or more, or 60% by mass or more, and 95% by mass or less, 90% by mass or less, 85% by mass or less, or 80% by mass or less, based on the total amount of components (A) and (B), from the viewpoint of ensuring the formation and curing properties of the adhesive film. When the content of component (B) is within the above range, the effects of this disclosure tend to be significantly exhibited. The content of component (B) in the adhesive film (conductive particle layer) (based on the total mass of the adhesive film or conductive particle layer) may be the same as the above range.

[0052] The thickness of the conductive particle layer 3 (adhesive film 10 consisting of a single layer of conductive particle layer 3) may be, for example, 3 to 20 μm. When the thickness of the conductive particle layer 3 is 3 μm or more, the fluidity of the conductive particles is more sufficiently ensured during bonding, and insulation tends to be better maintained. When the thickness of the conductive particle layer 3 is 20 μm or less, the conductive particles are more easily captured by the electrodes between opposing circuits during bonding, and connectivity tends to be better maintained. The thickness of the conductive particle layer 3 may be 4 μm or more, 5 μm or more, or 7 μm or more, and may also be 18 μm or less, 16 μm or less, or 15 μm or less.

[0053] Although the adhesive film of this embodiment has been described above, this disclosure is not limited to the above embodiment.

[0054] The adhesive film may consist of a single layer of conductive particle layer 3, as shown in the adhesive film 10 in Figure 1, or it may consist of two layers: a conductive particle layer and an insulating adhesive layer containing component (B). Furthermore, the adhesive film may consist of three or more layers, including two layers of conductive particle layer and an insulating adhesive layer containing component (B). For example, the adhesive film may comprise an insulating adhesive layer, a conductive particle layer 3, and an insulating adhesive layer in this order.

[0055] The thickness of the adhesive film, which consists of two or more layers (the sum of the thicknesses of all layers constituting the adhesive film), may be, for example, 5 to 30 μm. The thickness of the adhesive film may be 7 μm or more, or 10 μm or more, or 25 μm or less, or 20 μm or less.

[0056] The adhesive film for circuit connections of this embodiment makes it possible to manufacture circuit connection structures that maintain adhesiveness and low-temperature curing properties over a long period of time, and that have high connection reliability.

[0057] The adhesive film for circuit connection in this embodiment may have anisotropic conductivity. That is, the adhesive film for circuit connection may be an anisotropic conductive film. The adhesive film for circuit connection may also be a conductive adhesive film that does not have anisotropic conductivity.

[0058] Adhesive films are formed in a film shape on a support (separator) such as PET (polyethylene terephthalate) film, slit into tape-like strips, and then wound around a core material in a circular fashion to be manufactured as a reel-shaped, narrow, long tape (winding unit). The circuit connection adhesive film of this embodiment tends to develop surface irregularities due to freezing during storage, and this tends to suppress the formation of such irregularities that can cause compositional inconsistencies when the film is made into a reel shape, thus preventing problems during reel winding. In particular, when the adhesive film is made thin (for example, 5 μm or less), the effect of irregularities that occur during freezing storage tends to be greater, but the adhesive film of this disclosure tends to prevent such phenomena from occurring.

[0059] [Method for manufacturing adhesive film for circuit connections] A method for manufacturing an adhesive film according to one embodiment may include, for example, a conductive particle layer formation step of forming a conductive particle layer containing component (A) and component (B). The manufacturing method may also include an insulating adhesive layer formation step of forming an insulating adhesive layer on at least one surface of the conductive particle layer.

[0060] In the conductive particle layer formation process, for example, first, a composition containing component (A) and component (B), as well as other additives added as needed, is dissolved or dispersed in an organic solvent by stirring, mixing, kneading, etc., to prepare a varnish composition. Then, the varnish composition is applied to a substrate that has been treated with a mold release agent using a knife coater, roll coater, applicator, comma coater, die coater, etc., and the organic solvent is evaporated by heating to form a conductive particle layer (adhesive film) made of the composition on the substrate. At this time, the thickness of the final conductive particle layer (adhesive film) can be adjusted by adjusting the amount of varnish composition applied.

[0061] The organic solvent used in the preparation of the varnish composition is not particularly limited as long as it has the property of uniformly dissolving or dispersing each component. Examples of such organic solvents include toluene, acetone, methyl ethyl ketone (2-butanone), methyl isobutyl ketone, ethyl acetate, propyl acetate, and butyl acetate. These organic solvents can be used individually or in combination of two or more. Stirring, mixing, or kneading during the preparation of the varnish composition can be carried out using, for example, a stirrer, a 3-roll mill, a ball mill, a bead mill, a homodisper, etc.

[0062] The substrate is not particularly limited as long as it has heat resistance that can withstand the heating conditions when volatilizing organic solvents. Examples of such substrates include stretched polypropylene (OPP), polyethylene terephthalate (PET), polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, polyimide, cellulose, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, liquid crystal polymers, etc. (for example, films).

[0063] The heating conditions for volatilizing the organic solvent from the varnish composition applied to the substrate can be appropriately set according to the organic solvent used. For example, the heating conditions may be 40 to 120°C for 0.1 to 10 minutes.

[0064] The insulating adhesive layer formation step is the same as the conductive particle layer formation step, except that component (B) and other additives added as needed are used to form an insulating adhesive layer on the substrate. Then, the insulating adhesive layer can be formed on at least one surface of the conductive particle layer by bonding the conductive particle layer and the insulating adhesive layer together. Alternatively, in the insulating adhesive layer formation step, for example, an insulating adhesive layer can also be formed on at least one surface of the conductive particle layer by applying a varnish composition obtained using component (B) and other additives added as needed to at least one surface of the conductive particle layer and volatilizing the organic solvent.

[0065] Methods for bonding the conductive particle layer and the insulating adhesive layer include, for example, heat pressing, roll lamination, and vacuum lamination. Lamination can be carried out, for example, under temperature conditions of 0 to 80°C.

[0066] [Circuit connection structure and method for manufacturing the same] The following describes a circuit connection structure using the adhesive film 10 described above and a method for manufacturing the same.

[0067] Figure 2 is a schematic cross-sectional view showing one embodiment of a method for manufacturing a circuit connection structure. The method for manufacturing a circuit connection structure includes the step of interposing the adhesive film 10 between a first circuit member 13 having a first electrode 12 and a second circuit member 23 having a second electrode 22, and then heat-pressing the first circuit member 13 and the second circuit member 23 together to electrically connect the first electrode 12 and the second electrode 22 to each other. The method for manufacturing a circuit connection structure will be described in more detail below.

[0068] In the method for manufacturing a circuit connection structure, first, as shown in Figure 2(a), a first circuit member 13 (first circuit member 13 having the first electrode 12) having a first substrate 11 and a first electrode 12 provided on the first substrate 11, and a second circuit member 23 (second circuit member 23 having the second electrode 22) having a second substrate 21 and a second electrode 22 provided on the second substrate 21 are prepared.

[0069] Next, the first circuit member 13 and the second circuit member 23 are arranged so that the first electrode 12 and the second electrode 22 face each other, and the adhesive film 10 is placed between the first circuit member 13 and the second circuit member 23.

[0070] Then, the adhesive film 10 is cured by heating while applying pressure to the entire structure in the directions of arrows A and B. The pressure applied during pressurization may be, for example, 0.1 MPa or more and 100 MPa or less in terms of area-converted pressure at the bump electrodes. The heating temperature may be, for example, 50°C or more and 170°C or less. The time for pressurization and heating may be, for example, 0.5 seconds or more and 120 seconds or less. In this way, the first circuit member 13 and the second circuit member 23 are heat-pressed together via the adhesive film 10 (cured adhesive film 10).

[0071] The circuit connection structure 100 obtained in this way, as shown in Figure 2(b), comprises a first substrate 11 and a first circuit member 13 (first circuit member 13 having the first electrode 12) having a first electrode 12 provided on the first substrate 11, a second substrate 21 and a second circuit member 23 (second circuit member 23 having the second electrode 22) having a second electrode 22 provided on the second substrate 21, and a circuit connection portion 30 disposed between the first circuit member 13 and the second circuit member 23, which electrically connects the first electrode 12 and the second electrode 22 to each other. The circuit connection portion 30 includes a cured adhesive film 10c. More specifically, it may consist of a cured adhesive component 2c and conductive particles 1 dispersed in the cured adhesive component 2c. In the circuit connection structure 100, conductive particles 1 are interposed between the first electrode 12 and the second electrode 22, thereby electrically connecting the first electrode 12 and the second electrode 22, and the first circuit member 13 and the second circuit member 23 are bonded to each other.

[0072] The first substrate 11 and the second substrate 21 may be formed from inorganic materials such as semiconductors, glass, or ceramics, organic materials such as polyimide or polycarbonate, or composite materials such as glass / epoxy. The first substrate 11 and the second substrate 21 may be substrates formed from the same components, or they may be substrates formed from different components.

[0073] The first electrode 12 and the second electrode 22 may be electrodes containing metals such as gold, silver, tin, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, aluminum, molybdenum, titanium, neodymium, or oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), and indium gallium zinc oxide (IGZO). The first electrode 12 and the second electrode 22 may also be electrodes formed by stacking two or more of these metals, oxides, etc. The electrodes formed by stacking two or more types may have two or more layers, or three or more layers. The first electrode 12 and the second electrode 22 may be the same electrode or different electrodes.

[0074] The first circuit member 13 and the second circuit member 23 may be a glass substrate or plastic substrate, a printed circuit board, a ceramic circuit board, a flexible circuit board, an IC chip, etc., on which electrodes are formed. [Examples]

[0075] The present disclosure will be described in more detail below with reference to examples. However, the present disclosure is not limited to these examples.

[0076] [Fabrication of adhesive film (conductive particle layer)] <Synthesis of materials> Synthesis of B1a-1 4.71 g (42.0 mmol) of 3-cyclohexene-1-methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 50 mL of dimethylformamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were placed in a 300 mL round-bottom flask and cooled to 5°C with stirring. Subsequently, 4.71 g (42.0 mmol) of potassium tert-butoxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added at 5°C, and 4.87 g (20.0 mmol) of 3,3-bis(bromomethyl)oxetane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added dropwise. The mixture was then heated to room temperature (25°C) and stirred for 14 hours. Toluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was then added to the reaction mixture, washed with water, and the organic solvent was removed from the resulting organic layer by distillation. The obtained concentrate was purified by distillation to obtain 3,3-bis[(3-cyclohexen-1-ylmethoxy)methyl]oxetane) as a colorless, transparent liquid, yielding 3.98 g (13.0 mol / yield 65%).

[0077] In a 300 mL round-bottom flask, 3.98 g (13.0 mmol) of 3,3-bis[(3-cyclohexen-1-ylmethoxy)methyl]oxetane, 0.53 g (3.90 mmol) of potassium carbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 4 mL of acetonitrile (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 6 mL of methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added and the mixture was stirred at room temperature (25°C). Then, 5.19 g (45.5 mmol) of 30% aqueous hydrogen peroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added dropwise, and the mixture was stirred for 18 hours. 50 g of toluene was added to the reaction mixture, and the product was extracted and washed with water. The organic solvent was removed from the obtained organic layer by distillation, and the resulting concentrate was purified by silica gel column chromatography (ethyl acetate / hexane = 2 / 8 (volume ratio)) to obtain 2.54 g (7.50 mmol / yield 58%) of 3,3-bis[(3,4-epoxycyclohexyl-1-methoxy)methyl]oxetane as a colorless, transparent liquid.

[0078] <Preparing the materials> The following materials were used in the preparation of the adhesive film (conductive particle layer).

[0079] (A) Component: Conductive particles A-1: Conductive particles in which a nickel layer with a thickness of 0.2 μm is formed on the surface of polystyrene particles with an average particle size of 3 μm.

[0080] (B) Component: Adhesive component (B1) Component: Cationic polymerizable compound • (B1a) Component: A compound having an alicyclic epoxy structure and an oxetane ring structure within its molecule. B1a-1: 3,3-bis[(3,4-epoxycyclohexyl-1-methoxy)methyl]oxetane synthesized above • (B1b) Component: A compound that has an alicyclic epoxy structure within the molecule and does not have an oxetane ring structure. B1b-1: CEL2021P (Product name, manufactured by Daicel Corporation) B1b-2: CEL8010 (Product name, manufactured by Daicel Corporation) • (B1c) Component: A compound that has an oxetane ring structure within the molecule and does not have an alicyclic epoxy structure. B1c-1: ETERNACOLL OXBP (product name, manufactured by Ube Industries, Ltd.) B1c-2: OXT-121 (product name, manufactured by Toagosei Co., Ltd.) (B2) Ingredient: Thermal cationic polymerization initiator B2-1: Use CXC-1821 (product name, quaternary ammonium salt type thermoacid generator, manufactured by King Industries), diluted with organic solvent (methyl ethyl ketone) to a non-volatile content of 50% by mass. (B3) Component: Thermoplastic resin B3-1: YP-70 (product name, copolymer phenoxy resin of bisphenol A and bisphenol F, weight-average molecular weight: 55,000, glass transition temperature: 70°C, manufactured by Nippon Steel Chemical & Material Co., Ltd.), diluted with organic solvent (methyl ethyl ketone) to a non-volatile content of 50% by mass. (B4) Ingredients: Coupling agent B4-1: SH-6040 (Product name, 3-glycidoxypropyltrimethoxysilane, manufactured by Toray Dow Corning Co., Ltd.) (B5) Components: Filler B5-1: Use the hydrolysis product of trimethoxyoctylsilane and silica, diluted to 10% by mass of non-volatile content with an organic solvent (a 1:1 mixed solvent of toluene / ethyl acetate).

[0081] <Fabrication of adhesive film (conductive particle layer)> The materials shown in Table 1 were mixed in the composition ratios shown in Table 1 (the values ​​in Table 1 (unit: parts by mass) represent the non-volatile content). First, component (B) was mixed, and then component (A) was dispersed to obtain a varnish composition. Subsequently, the varnish was coated onto a release-treated substrate film (PET (polyethylene terephthalate) film, thickness: 38 μm), and an organic solvent was applied and hot-air dried at 60°C for 3 minutes to obtain adhesive films of Examples 1-3 and Comparative Examples 1-4, each having a 15 μm thick conductive particle layer containing each component.

[0082] [Evaluation of adhesive films] <Evaluation of adhesiveness> The adhesive properties were evaluated using the adhesive films of Examples 1-3 and Comparative Examples 1-4. For the evaluation of adhesive properties, two types of adhesive films were prepared: the adhesive film immediately after formation (initial adhesive film) and the adhesive film after being exposed to air and then to visible light under fluorescent lighting, in a room temperature (25°C) and 60% humidity environment for 4 days (adhesive film after standing).

[0083] As an evaluation substrate, a substrate was prepared by forming an electrode wiring pattern (pattern width: 19 μm, electrode spacing: 5 μm) consisting of three layers of AlNd (thickness: 100 nm) / Mo (thickness: 50 nm) / ITO (thickness: 100 nm) on the surface of an alkali-free glass substrate (OA-11, manufactured by Nippon Electric Glass Co., Ltd., dimensions: 38 mm x 28 mm, thickness: 0.3 mm). Next, a 2.0 mm x 25 mm adhesive film was placed so that the conductive particle layer was in contact with the wiring pattern on the alkali-free glass substrate. A thermocompression bonding apparatus (LD-06, manufactured by Ohashi Seisakusho Co., Ltd.) consisting of a ceramic heater stage and a tool (8 mm x 50 mm) was used at 50°C and 0.98 MPa (10 kgf / cm²). 2 The evaluation substrate was heated and pressurized for 2 seconds under the specified conditions, and an adhesive film was attached to it. The base film of the adhesive film was then peeled off. Subsequently, the evaluation substrate was observed from the side opposite to the side to which the adhesive film was attached using an FPD / LSI inspection microscope (ECLIPSE L300ND, manufactured by Nikon Instec Co., Ltd.). If no lifting occurred between the evaluation substrate and the adhesive film, it was evaluated as "A," and if lifting occurred, it was evaluated as "B." The results are shown in Table 1.

[0084] <Measuring connection resistance> The adhesive properties were evaluated using the adhesive films of Examples 1-3 and Comparative Examples 1-4. For the evaluation of adhesive properties, two types of adhesive films were prepared: the adhesive film immediately after formation (initial adhesive film) and the adhesive film after being exposed to air and then to visible light under fluorescent lighting, in a room temperature (25°C) and 60% humidity environment for 4 days (adhesive film after standing).

[0085] (Preparation of circuit components) As the first circuit component, a substrate was prepared on which a wiring pattern of electrodes consisting of three layers of AlNd (thickness: 100 nm) / Mo (thickness: 50 nm) / ITO (thickness: 100 nm) was formed on the surface of an alkali-free glass substrate (OA-11, manufactured by Nippon Electric Glass Co., Ltd., external dimensions: 38 mm x 28 mm, thickness: 0.3 mm). The pattern (pattern width: 19 μm, inter-electrode space: 5 μm) was formed. As the second circuit component, an IC chip (external dimensions: 0.9 mm x 20.3 mm, thickness: 0.3 mm, bump electrode size: 70 μm x 12 μm, inter-bump electrode space: 12 μm, bump electrode thickness: 8 μm) was prepared with bump electrodes arranged in a staggered pattern in two rows.

[0086] (Fabrication of circuit connection structures) The adhesive film was placed on the first circuit component. A thermocompression bonding device (LD-06, manufactured by Ohashi Seisakusho Co., Ltd.) consisting of a ceramic heater stage and a tool (8 mm x 50 mm) was used at 50°C and 0.98 MPa (10 kgf / cm²). 2 The adhesive film was attached to the first circuit member by heating and pressurizing for 2 seconds under the specified conditions, and the base film of the adhesive film was peeled off. Next, the circuit electrodes of the first circuit member and the bump electrodes of the second circuit member were aligned, and then the circuit connection structure was fabricated by heating and pressurizing for 5 seconds at 120°C and 60 MPa on a base heated to 80°C. The temperature during the fabrication of the circuit connection structure represents the measured maximum temperature reached by the adhesive film, and the pressure represents the area-converted pressure at the bump electrodes, calculated by the total area of ​​the surfaces of the bump electrodes of the second circuit member facing the first circuit member. In addition, 120°C is considered a low temperature for curing conditions.

[0087] (Measurement of connection resistance) The connection resistance was measured using the four-terminal measurement method. Two types of circuit connection structures were prepared for the measurement: one immediately after fabrication (circuit connection structure after low-temperature curing) and another after being left in a constant temperature and humidity chamber at 85°C and 85%RH for 500 hours (circuit connection structure after high temperature and high humidity). In other words, for each adhesive film, circuit connection structures treated under four different conditions were prepared and their connection resistance was measured. The connection resistance was measured at 14 points on each circuit connection structure, and the maximum value was taken as the connection resistance value. A connection resistance value of less than 2.5Ω was evaluated as "A", a connection resistance value of 2.5Ω or more and less than 5.0Ω as "B", a connection resistance value of 5.0Ω or more and less than 7.5Ω as "C", a connection resistance value of 7.5Ω or more and less than 10.0Ω as "D", and a connection resistance value of 10.0Ω or more as "E". The results are shown in Table 1.

[0088] [Table 1]

[0089] As shown in Table 1, the adhesive films of Examples 1 to 3, which have a conductive particle layer containing a cationic polymerizable compound that includes a compound having an alicyclic epoxy structure and an oxetane ring structure in its molecule, exhibited superior adhesion and low-temperature curing properties compared to the adhesive films of Comparative Examples 1 to 4, which have a conductive particle layer that does not contain the predetermined compound, even when left for a long period (e.g., 3 days or more) at room temperature (25°C) under conditions of exposure to air and visible light. These results confirm that the adhesive film for circuit connections of this disclosure can maintain adhesion and low-temperature curing properties for a long period and can be used to manufacture circuit connection structures with high connection reliability. [Explanation of Symbols]

[0090] 1...conductive particles, 2...adhesive component, 2c...cured adhesive component, 3...conductive particle layer, 10...adhesive film for circuit connection (adhesive film), 10c...cured adhesive film for circuit connection (adhesive film), 11...first substrate, 12...first electrode, 13...first circuit member, 21...second substrate, 22...second electrode, 23...second circuit member, 30...circuit connection part, 100...circuit connection structure.

Claims

1. The device comprises a conductive particle layer containing conductive particles, a cationic polymerizable compound, and a thermal cationic polymerization initiator. The conductive particle layer contains, as the cationic polymerizable compound, a compound having an alicyclic epoxy structure and an oxetane ring structure in its molecule. Adhesive film for circuit connections.

2. The compound having an alicyclic epoxy structure and an oxetane ring structure within the molecule is the compound represented by the following formula (I-1). The adhesive film for circuit connection according to claim 1. 【Chemistry 1】

3. The conductive particle layer further contains, as the cationic polymerizable compound, a compound having an alicyclic epoxy structure in its molecule and not having an oxetane ring structure, or a compound having an oxetane ring structure in its molecule and not having an alicyclic epoxy structure. The adhesive film for circuit connection according to claim 1 or 2.

4. A first circuit member having a first electrode, A second circuit member having a second electrode, A circuit connection portion is disposed between the first circuit member and the second circuit member and electrically connects the first electrode and the second electrode to each other, Equipped with, The circuit connection portion includes a cured product of the circuit connection adhesive film described in any one of claims 1 to 3. Circuit connection structure.

5. The method comprises the steps of interposing a circuit connection adhesive film according to any one of claims 1 to 3 between a first circuit member having a first electrode and a second circuit member having a second electrode, and then heat-pressing the first circuit member and the second circuit member together to electrically connect the first electrode and the second electrode to each other. A method for manufacturing a circuit connection structure.

Images