Conductive particles, adhesive film for circuit connection and method for manufacturing the same, and connection structure and method for manufacturing the same.

Abstract

To provide conductive particles of an adhesive film for circuit connection which can improve insulation properties between adjacent electrodes in a connection structure and capturing properties of the conductive particles.SOLUTION: Conductive particles P for an adhesive film for circuit connection include a conductive mother particle 31, and child particles 32 coating the surface of the mother particle 31, when the particle radius and the particle diameter of the child particles 32 determined through observation at a magnitude of 30,000 times by SEM are represented by rX and dX, and the average particle diameter of the child particles 32 that is the average value of the particle diameter dX is represented by dY, the modified profile of the child particles 32 determined by the following expression (1) is 2.0 or more. Modified profile=D / rY×100. In the expression (1), rY represents a radius of a virtual ball with a diameter equal to dY, and D represents an average value of an absolute difference between the particle radius rX of the child particles 32 and the radius rY of the virtual ball.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to conductive particles, adhesive films for circuit connections, and methods for manufacturing the same, as well as connection structures and methods for manufacturing the same. [Background technology]

[0002] Conventionally, for example, anisotropic conductive adhesive films, which contain conductive particles dispersed in the adhesive, have been used as adhesive materials for connecting liquid crystal displays to tape carrier packages (TCPs), flexible printed circuit boards (FPCs) to TCPs, or FPCs to printed circuit boards. Also, when mounting semiconductor silicon chips to substrates, so-called chip-on-glass (COG) mounting, where semiconductor silicon chips are directly mounted to the substrate, has been adopted as an alternative to conventional wire bonding, and here too, anisotropic conductive adhesive films are used. Here, "anisotropic conductivity" means that it conducts in the direction of pressure and maintains insulating properties in the direction of non-pressure.

[0003] In recent years, with the development of electronic devices, wiring density has increased and circuits have become more sophisticated. As a result, connection structures with narrower spacing between connecting electrodes are required, and the bump electrodes of connecting components have also been reduced in size. In order to obtain a stable electrical connection in a small-area bump connection, a sufficient number of conductive particles must be interposed between the bump electrode and the circuit electrode on the substrate side.

[0004] In response to this, methods are being investigated to improve the insulation between adjacent electrodes and the capture ability of conductive particles (connectivity between opposing electrodes) by applying a magnetic force to conductive particles within a circuit connection adhesive film to separate the aggregated conductive particles. For example, Patent Document 1 proposes a method of separating conductive particles by applying a magnetic field in the thickness direction of the circuit connection adhesive film. [Prior art documents] [Patent Documents]

[0005] Japanese Patent Document 1 Japanese Patent Application Laid-Open No. 2015-167186 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] The inventors of the present invention studied a method for improving the insulation between adjacent electrodes and the capture property of conductive particles (connectivity between opposing electrodes) without using the method described in the above Patent Document 1.

[0007] The main objects of the present invention are to provide conductive particles for a circuit connection adhesive film that can improve the insulation between adjacent electrodes and the capture property of conductive particles in a connection structure, to provide a circuit connection adhesive film using the conductive particles and a manufacturing method thereof, and to provide a connection structure obtained by using the circuit connection adhesive film and a manufacturing method thereof. MEANS FOR SOLVING THE PROBLEMS

[0008] The present invention provides the following [1] to

[15] in some aspects.

[0009] [1] Conductive particles for a circuit connection adhesive film, comprising conductive mother particles and child particles covering the surface of the mother particles, and the particle radius and particle diameter of the child particles obtained by observing with SEM at a magnification of 30,000 times are r X and d X respectively, and when the average particle diameter of the child particles, which is the average value of the particle diameter d X , is d Y , the following formula (1) is used to determine that the degree of irregularity of the child particles is greater than 2.0. Conductive particles. Degree of irregularity = D / r Y ×100 (1) [In formula (1), r Y represents the radius of a virtual sphere having a diameter equal to d Y , and D represents the average value of the absolute difference between the particle radius r X of the child particles and the radius r Y of the virtual sphere.]

[0010] [2] The coverage rate of the surface of the mother particle by the daughter particles is 30.0% or more, the conductive particles according to [1].

[0011] [3] The C.V. value of the coverage rate of the surface of the mother particle by the daughter particles is 20.0% or less, the conductive particles according to [1] or [2].

[0012] [4] The average particle diameter of the daughter particles determined by observing at a magnification of 30,000 times by SEM is 200 to 400 nm, the conductive particles according to any one of [1] to [3].

[0013] [5] When a film is formed from the conductive particles, the contact angle of the surface of the film with respect to water is 85 to 115°, the conductive particles according to any one of [1] to [4].

[0014] [6] The daughter particles contain a polymer containing a polar group-containing monomer as a monomer unit, the conductive particles according to any one of [1] to [5].

[0015] [7] The polar group-containing monomer contains at least one selected from the group consisting of (meth)acrylic acid and its salts, styrenesulfonic acid and its salts, (meth)acryloyl group-containing phosphoric acid monoesters and their salts, (meth)acryloyl group-containing epoxy monomers, (meth)acryloyl group-containing carboxylic acid esters, and (meth)acryloyl group-containing alkoxysilanes and their hydrolyzates, the conductive particles according to [6].

[0016] [8] The content of the polar group-containing monomer contained as a monomer unit in the polymer is 9.0 to 15.0 mol% based on the total amount of the monomer units contained in the polymer, the conductive particles according to [6] or [7].

[0017] [9] The polymer contains a non-aromatic crosslinkable monomer and a non-crosslinkable monomer as monomer units, the conductive particles according to any one of [6] to [8].

[0018]

[10] The conductive particle according to [9], wherein the non-aromatic crosslinkable monomer is a polyfunctional (meth)acrylate monomer having a hydrocarbon chain which may have an ether linkage and a plurality of (meth)acryloyloxy groups bonded to the hydrocarbon chain.

[0019]

[11] The conductive particle according to [9] or

[10] , wherein the non-crosslinkable monomer is a methacrylic acid ester.

[0020]

[12] Conductive particles according to any one of [6] to

[11] , wherein the polymer is an emulsion polymer.

[0021]

[13] A circuit connection adhesive film comprising a conductive adhesive layer containing an adhesive component and conductive particles according to any one of [1] to

[12] .

[0022]

[14] A connection structure comprising a first member having a first electrode, a second member having a second electrode, and a connecting portion disposed between the first member and the second member for electrically connecting the first electrode and the second electrode, wherein the connecting portion includes a cured product of the circuit connection adhesive film described in

[13] .

[0023]

[15] A method for manufacturing a connection structure, comprising the steps of: heat-pressing a first member having a first electrode and a second member having a second electrode with a circuit connection adhesive film described in

[13] interposed between the first member and the second member, and electrically connecting the first electrode and the second electrode to each other. [Effects of the Invention]

[0024] According to the present invention, conductive particles for a circuit connection adhesive film can be provided that can improve the insulation between adjacent electrodes in a connection structure and the capture ability of conductive particles. Furthermore, according to the present invention, a circuit connection adhesive film using the conductive particles and a method for manufacturing the same can be provided. Furthermore, according to the present invention, a connection structure obtained using the circuit connection adhesive film and a method for manufacturing the same can be provided. [Brief explanation of the drawing]

[0025] [Figure 1] This is a schematic cross-sectional view showing one embodiment of conductive particles according to the present invention. [Figure 2] This is a schematic cross-sectional view showing one embodiment of the adhesive film for circuit connection according to the present invention. [Figure 3] This is a schematic cross-sectional view showing one embodiment of the connection structure according to the present invention. [Figure 4] Figure 3 is a schematic cross-sectional view showing the manufacturing process of the connecting structure. [Modes for carrying out the invention]

[0026] In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise in this specification, the upper or lower limit of one step in the numerical range may be replaced with the upper or lower limit of another step in the numerical range. Also, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples. Furthermore, the upper and lower limits described individually can be combined in any way. In this specification, "(meth)acrylate" means at least one of acrylate and its corresponding methacrylate. The same applies to other similar expressions such as "(meth)acryloyl". Furthermore, "(poly)" means both with and without the prefix "poly". Furthermore, "A or B" means that either A or B is included, or both are included. Furthermore, unless otherwise specified, the materials exemplified below may be used individually or in combination of two or more. The content of each component in a composition refers to the total amount of any multiple substances present in the composition, unless otherwise specified, if multiple substances corresponding to each component exist in the composition.

[0027] The embodiments of the present invention will be described in detail below, with reference to the drawings as appropriate. However, the present invention is not limited to the following embodiments.

[0028] <Conductive particles> Figure 1 is a schematic cross-sectional view showing conductive particles of one embodiment. The conductive particles P are conductive particles used in an adhesive film for circuit connections, and comprise conductive mother particles 31 and daughter particles 32 that cover the surface of the mother particles 31. Here, in this specification, conductive means not insulating, and insulating means that the resistance value measured by a powder resistance measuring device is greater than 1.0E+09Ω. As a special manufacturing method for adhesive films for circuit connections, a method for manufacturing an adhesive film for circuit connections is known that includes a step (external force application step) in which an external force (e.g., magnetic force) is applied to the conductive particles in a film containing adhesive components and conductive particles to disperse the conductive particles. However, the conductive particles P of this embodiment are suitably used in adhesive films for circuit connections other than the so-called "external force dispersion type adhesive film for circuit connections" described above.

[0029] In the conductive particle P of this embodiment, the degree of irregularity of the sub-particle 32 is greater than 2.0. Here, the degree of irregularity is an index that indicates the degree of distortion relative to a perfect sphere of similar particle size, and the particle radius and particle diameter of the sub-particle, obtained by observation at a magnification of 30,000x using SEM, are respectively r X and d X The particle diameter d X The average particle diameter of the subparticle 32, which is the average value, is d Y In this case, it can be calculated using the following formula (1). Anomaly degree=D / r Y ×100 (1) [In formula (1), r Y The diameter is d Y This indicates the radius of a virtual sphere equal to r, where D is the particle radius of the subparticle r. X and the radius r of the virtual sphere Y This shows the average of the absolute differences between the two values.

[0030] Since the conductive particles P described above comprise sub-particles 32 having a degree of irregularity within the above range, when used as conductive particles for adhesive films for circuit connections, they have the effect of improving the insulation between adjacent electrodes in the connection structure and the capture ability of conductive particles. Generally, in the manufacture of adhesive films for circuit connections, a coating solution (paste) using an organic solvent with an SP value (Hildebrand solubility parameter) of 8.5 to 10.0 is used as the solvent. The effect of the sub-particles 32 described above is particularly pronounced when an organic solvent with such an SP value (e.g., acetone, methyl ethyl ketone, ethyl acetate, toluene, etc.) is used as the solvent for the coating solution, and is especially pronounced when the solvent is methyl ethyl ketone.

[0031] The reasons for obtaining the above effects are presumed to be as follows. First, the high degree of heteromorphism of the sub-particles 32 means that the sub-particles 32 are highly polar organic particles or organic-inorganic hybrid particles. These particles have a high affinity for organic solvents with an SP value of 8.5 to 10.0 and are prone to swelling in the coating solution. On the other hand, in the case of conductive particles as described above, the higher the affinity of the sub-particles to the solvent (organic solvent) in the coating solution, that is, the more easily the sub-particles swell in the coating solution, the greater the steric hindrance of the conductive particles. Based on Stokes' sedimentation theorem, the sedimentation rate of the conductive particles in the coating solution slows down, and thus the conductive particles are thought to exhibit higher dispersibility. Furthermore, adhesive components (resins, etc.) used in adhesive films for circuit connections usually have a high affinity for solvents. Therefore, if the sub-particles have a high affinity for the solvent (organic solvent) in the coating solution, they tend to have a high affinity for the adhesive components as well. For this reason, when the adhesive components flow due to the mounting pressure during connection, self-aggregation is less likely to occur, and the sub-particles are more likely to be removed from between electrodes along with the adhesive components. For these reasons, it is presumed that the above effects can be obtained.

[0032] The degree of irregularity of the above-mentioned subparticles 32 may be 2.3 or higher, 2.5 or higher, 2.7 or higher, or 3.0 or higher, from the viewpoint of achieving higher dispersibility of the conductive particles P. The degree of irregularity may be 5.0 or lower, 4.5 or lower, or 4.0 or lower, from the viewpoint of manufacturing stability of the subparticles and adsorption stability to the mother particles. The degree of irregularity can be adjusted by the constituent material of the subparticles, for example, by the amount of polar group-containing monomer (such as alkoxysilane having an ethylenically unsaturated group) added.

[0033] With the conductive particles P described above, the sub-particles act as spacers, which has the effect of making it difficult for the conductive particles to bind and aggregate before and after film formation. Furthermore, if the sub-particles 32 are insulating, even if the conductive particles connect to each other during connection, the insulating effect can be ensured. Moreover, since the sub-particles 32 detach from the surface of the parent particle 31 between opposing electrodes, connection reliability can be ensured even if the sub-particles 32 are insulating.

[0034] (base particle) The mother particle 31 is a conductive particle. For example, the mother particle 31 can be a metal particle composed of metals such as gold, silver, palladium, ruthenium, iridium, nickel, tungsten, molybdenum, copper, tin, or solder, or a conductive carbon particle composed of conductive carbon. The mother particle 31 may also be a core-shell particle, as shown in Figure 1, comprising an insulating core particle 31a and a conductive coating layer (shell) 31b covering the core particle 31a. Among these, a core-shell particle is preferred because, by making the core particle 31a an elastically deformable particle, the conductive particles can be elastically deformed during connection, resulting in improved capture of conductive particles and reduced load on electrodes, etc.

[0035] The core particle 31a of the core-shell particle may be a particle containing insulating glass, ceramic, plastic, etc. Preferably, the core particle 31a is an insulating organic core particle. The organic core particle is a particle composed of an organic compound (e.g., plastic), and usually contains 40% by mass or more of the organic compound. Examples of organic compounds that constitute the organic core particle include acrylic resin, which is a polymer of acrylic monomer, and olefin resin, which is a polymer of olefin monomer. Examples of acrylic monomers include alkyl (meth)acrylate and alkanediol di(meth)acrylate. Examples of olefin monomers include ethylene, propylene, isobutylene, and butadiene.

[0036] The core particles 31a may be hard or soft. The preferred hardness (modulus of elasticity) of the core particles 31a varies depending on the application. The modulus of elasticity (compression modulus, hereinafter referred to as the "20%K value") when the core particles 31a are compressed at room temperature (e.g., 25°C) and deformed by 20% may be 0.5 to 40.0 GPa, and may be 1.0 to 10.0 GPa or 10.0 to 25.0 GPa. The 20%K value can be measured using a Fischerscope HM2000 (manufactured by Fischer Instruments) by the following method. 1) Place the particle sample on a glass slide at room temperature (20-27°C) and apply pressure towards the center of the particle. 2) The compressive deformation modulus (K20, 20%K value) of the particle sample when it is deformed by 20% is measured while applying a load of 50 mN for 50 seconds, and then calculated according to the following formula. K20 (compressive deformation modulus) = (3 / √2) × F20 × S20 -3 / 2 ×R -1 / 2 F20: Load (N) required to deform a particle by 20% S20: Amount of particle deformation (m) at 20% deformation.

[0037] The core particle 31a is preferably spherical. The average particle diameter of the core particle 31a is, for example, 1.5 to 10.0 μm, and may be 2.0 to 5.0 μm or 5.0 to 10.0 μm. This average particle diameter is the average particle diameter measured by a wet flow particle size analyzer (FPIA-3000S manufactured by Spectris Co., Ltd.).

[0038] The material constituting the coating layer 31b may be a metal or conductive carbon. Preferably, the coating layer 31b is a metal layer (a layer containing metal as a constituent material). The metal layer may be composed of materials containing metals such as gold, silver, copper, platinum, zinc, iron, palladium, ruthenium, iridium, nickel, tin, chromium, titanium, aluminum, cobalt, germanium, cadmium, tungsten, and molybdenum, as well as metal compounds such as ITO and solder. From the viewpoint of corrosion resistance, nickel, palladium, or gold are preferably used as constituent materials for the metal layer. Preferably, the metal layer contains 95.0% by mass or more of metal or metal compounds. From the viewpoint of imparting conductivity and hardness, the metal layer may also contain carbon compounds such as carbon nanotubes and carbon black. Core-shell particles having a metal layer as the coating layer 31b can be obtained, for example, by forming the metal layer on the surface of a core particle by methods such as sputtering or plating (e.g., electroless plating).

[0039] The coating layer 31b may be a single-layer structure or a laminated structure consisting of multiple layers. If it is a single-layer structure, the coating layer 31b preferably contains nickel from the viewpoint of cost, conductivity and corrosion resistance.

[0040] The thickness of the coating layer 31b may be 70 nm or more, and may be 100 nm or more, or 150 nm or more, from the viewpoint of improving the conductivity reliability between opposing electrodes. The thickness of the coating layer 31b may be 150 nm or less, 170 nm or less, or 200 nm or less, from the viewpoint of making it easier to obtain the effect originating from the nucleus particles. The thickness of the coating layer 31b is the average value of the thickness at five locations measured by preparing a cast sample by dispersing conductive particles in a casting resin and casting it, then polishing the surface of the cast sample using ion milling or the like to expose the cross-section of the particles, and observing the cross-section of the particles using an SEM.

[0041] The surface of the mother particle 31 may be smooth, but it is preferable that it has irregularities. Furthermore, it is preferable that the mother particle 31 is spherical. The average particle diameter of the mother particle 31 is, for example, 1.7 to 10.5 μm, and may be 2.0 to 5.5 μm or 5.5 to 10.5 μm. This average particle diameter is measured using a wet flow particle size analyzer (FPIA-3000S, manufactured by Spectris Corporation).

[0042] (child particle) The subparticles 32 are, for example, fine particles containing an organic compound as a constituent material (organic fine particles), and preferably fine particles containing an insulating organic compound as a constituent material. The subparticles 32 may also be fine particles containing both an organic compound and an inorganic compound (organic-inorganic hybrid fine particles). The subparticles 32 are preferably insulating fine particles, and more preferably insulating organic fine particles.

[0043] The child particles 32 are preferably polymers containing polar group-containing monomers as monomer units, from the viewpoint of easily obtaining the above degree of irregularity and securing bonding points with the mother particles to increase the coverage rate of the mother particles by the child particles. Such polymers have polar groups derived from polar group-containing monomers. The polymer may be a homopolymer or a copolymer.

[0044] Examples of polar groups include functional groups such as silanol groups, carboxyl groups, amino groups, hydroxyl groups, sulfonic acid groups, cyano groups, epoxy groups, and phosphate groups, as well as functional groups (alkoxysilyl groups) that generate these polar groups through hydrolysis. Epoxy groups may be included as part of glycidyl groups.

[0045] From the viewpoint of easily obtaining the above-mentioned degree of morphology of offshoots, monomers having a (meth)acryloyl group or a styryl group are preferred as polar group-containing monomers. As polar group-containing monomers having a (meth)acryloyl group, at least one selected from the group consisting of (meth)acrylic acid and its salts, (meth)acryloyl group-containing phosphate monoesters and their salts, (meth)acryloyl group-containing epoxy monomers, (meth)acryloyl group-containing carboxylic acid esters, and (meth)acryloyl group-containing alkoxysilanes and their hydrolysates is preferably used. As polar group-containing monomers having a styryl group, styrene sulfonic acid and its salts are preferred.

[0046] Examples of (meth)acrylic acid salts and styrene sulfonic acid salts include sodium salts such as sodium (meth)acrylate and sodium styrene sulfonate.

[0047] Examples of (meth)acryloyl group-containing phosphate monoesters include mono(2-hydroxyethyl (meth)acrylate) phosphate. Mono(2-hydroxyethyl (meth)acrylate) phosphate may be provided as a mixture with other components.

[0048] Examples of epoxy monomers containing a (meth)acryloyl group include glycidyl (meth)acrylate and 3,4-epoxycyclohexyl (meth)acrylate.

[0049] Examples of (meth)acryloyl group-containing carboxylic acid esters include (meth)acryloyloxyethyl succinic acid, (meth)acryloyloxyethyl phthalic acid, and (meth)acryloyloxypropyl phthalic acid.

[0050] Examples of (meth)acryloyl group-containing alkoxysilanes include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane. From the viewpoint of further reducing the degree of misformation of subparticles, it is preferable to use dimethoxysilane.

[0051] From the viewpoint of reducing the degree of misformation of the child particles, it is preferable that the number of units derived from polar group-containing monomers in the polymer be as small as possible. From this viewpoint, the content of polar group-containing monomers included as monomer units in the polymer may be 15.0 mol% or less, or 12.0 mol% or less, based on the total amount of monomer units contained in the polymer. From the viewpoint of increasing the degree of misformation of the child particles, it is preferable that the number of units derived from polar group-containing monomers in the polymer be as large as possible. From this viewpoint, the content of polar group-containing monomers included as monomer units in the polymer may be 9.0 mol% or more, or 12.0 mol% or more, based on the total amount of monomer units contained in the polymer. From these viewpoints, the content of polar group-containing monomers included as monomer units in the polymer may be 9.0 to 15.0 mol%, 9.0 to 12.0 mol%, or 12.0 to 15.0 mol%, based on the total amount of monomer units contained in the polymer.

[0052] The above polymer may contain non-aromatic crosslinkable monomers and non-crosslinkable monomers as monomer units. In this case, one or both of the non-aromatic crosslinkable monomers and non-crosslinkable monomers may have polar groups. In particular, when some of the non-crosslinkable monomers contained in the above polymer are monomers containing polar groups, it tends to be possible to stably synthesize subparticles 32 and to easily control the particle size.

[0053] Non-aromatic crosslinkable monomers are monomers that do not contain aromatic hydrocarbon groups and contain two or more crosslinkable groups. Examples of crosslinkable groups include vinyl groups and ethylenically unsaturated groups such as (meth)acryloyl groups. The (meth)acryloyl group may be part of a (meth)acryloyloxy group.

[0054] As non-aromatic crosslinkable monomers, from the viewpoint of moderately increasing the degree of heteromorphism, polyfunctional monomers having a hydrocarbon chain which may have ether bonds and a plurality of crosslinkable groups bonded to the hydrocarbon chain are preferred, and polyfunctional (meth)acrylate monomers having a hydrocarbon chain which may have ether bonds and a plurality of (meth)acryloyloxy groups bonded to the hydrocarbon chain are more preferred. Examples of hydrocarbon chains having ether bonds include (poly)oxyalkylene chains such as (poly)oxyethylene chains (EO chains) and (poly)oxypropylene chains (PO chains). When the hydrocarbon chain having ether bonds is a (poly)oxyalkylene chain, the number of oxyalkylenes constituting the (poly)oxyalkylene chain is preferably 1 to 4. From the viewpoint of preventing the degree of heteromorphism of the child particles from becoming too high, at least one selected from the group consisting of di(meth)acrylates having EO chains with 1 to 4 oxyethylenes and di(meth)acrylates having PO chains with 1 to 4 oxypropylenes is preferably used.

[0055] Examples of non-aromatic crosslinkable monomers include diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, 2-hydroxy-1,3-di(meth)acryloxypropane, 1,4-butanediol di(meth)acrylate, butadiene, isoprene, and other conjugated dienes. These monomers may be used individually or in combination of two or more types.

[0056] The content (degree of crosslinking) of non-aromatic crosslinkable monomers contained in the polymer as monomer units may be 0.1 to 1.0% by mass, or 0.1 to 0.5% by mass or 0.5 to 1.0% by mass, based on the total amount of monomer units contained in the polymer. When the content of non-aromatic crosslinkable monomers is 1.0% by mass or less, aggregation during polymerization is easily suppressed. When the content of non-aromatic crosslinkable monomers is 0.1% by mass or more, the degree of crosslinking is insufficient, and dissolution in organic solvents is less likely to occur.

[0057] Non-crosslinkable monomers are monomers that contain one polymerizable group. Examples of polymerizable groups include ethylenically unsaturated groups such as vinyl groups and (meth)acryloyl groups.

[0058] Examples of non-crosslinkable monomers include (i) styrene or its derivatives such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, pt-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, etc., (ii) methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and methacrylic acid. (iii) (meth)acrylic acid esters such as n-butyl, isobutyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, stearyl methacrylate, glycidyl methacrylate, etc., (iv) vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, etc., (iv) N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone, etc., (v) fluoride Examples include (meth)acrylic acid esters containing alkyl fluorides such as vinyl, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, trifluoroethyl acrylate, and tetrafluoropropyl acrylate, and alkoxysilanes having a (meth)acryloyl group such as (vi)3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane. These can be used individually or in combination of two or more.

[0059] The non-crosslinkable monomer may be a non-aromatic non-crosslinkable monomer that does not contain an aromatic hydrocarbon group. The non-crosslinkable monomer may be a monomer having a hydrocarbon group, such as a (meth)acrylic acid ester, from the viewpoint of insulating properties, dispersibility on film, ease of synthesis, and cost. The non-crosslinkable monomer is preferably a methacrylic acid ester.

[0060] When using two or more non-crosslinkable monomers in combination, it is preferable to use a non-crosslinkable monomer without functional groups and a monomer having functional groups. As the monomer having functional groups, it is preferable to use alkoxysilanes such as (vi)p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane. Such alkoxysilanes produce silanol groups upon hydrolysis, which tends to improve the surface treatability of the subparticles by the surface treatment agents described later.

[0061] The content of non-crosslinkable monomers included in the polymer as monomer units may be 50 to 70% by mass, 50 to 60% by mass, or 60 to 70% by mass, based on the total amount of monomer units in the polymer. When the content of non-crosslinkable monomers is 50% by mass or more, the sub-particles tend to be more flexible, and the conductivity resistance of the resulting connection structure tends to be improved. When the content of non-crosslinkable monomers is 70% by mass or less, the sub-particles tend to have better solvent resistance and tend to be relatively hard and resilient.

[0062] Methods for synthesizing the sub-particles 32 include precipitation polymerization and emulsion polymerization, but emulsion polymerization is preferred from the viewpoint of controlling the degree of irregularity, controlling the particle size, and ease of synthesis. In other words, it is preferable that the sub-particles 32 be an emulsion polymer.

[0063] In emulsion polymerization, polymerization is carried out by heating an emulsion composed of monomers and an aqueous medium while stirring. The emulsion can be obtained, for example, by adding monomers to an aqueous medium and emulsifying with a dispersant, or by adding monomers to an aqueous medium and dispersing them mechanically (for example, using a microemulsifier such as a homogenizer, ultrasonic processor, or nanomizer). The stirring speed may be in the range of 100 to 500 rpm (revolutions / minute). The polymerization temperature may be in the range of 40 to 90°C. The polymerization time may be in the range of 2 to 24 hours. The concentration of total monomers may be 1 to 30% by mass relative to the aqueous medium.

[0064] Examples of aqueous media used in emulsion polymerization include water, and mixed media of water and water-soluble solvents (e.g., lower alcohols). From the viewpoint of preventing unintended dissolution of monomers into the medium, the aqueous medium may be water.

[0065] A polymerization initiator may be added to the above emulsion as needed. The polymerization initiator and monomer may be mixed beforehand and then dispersed in an aqueous medium, or the polymerization initiator and monomer may be dispersed separately in an aqueous medium. The polymerization initiator is, for example, a radical polymerization initiator. Examples of radical polymerization initiators include benzoyl peroxide, t-butyl benzoate, potassium peroxodisulfate, 1,1-azobis(cyclohexane-1-carbonitride), 2,2-azobisisobutyronitrile, and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]. These compounds may be used in hydrate form. The polymerization initiator may be used in an amount of 0.1 to 7.0 parts by mass per 100 parts by mass of the total monomer.

[0066] The above emulsified solution may contain surfactants such as anionic, cationic, nonionic, or amphoteric surfactants as emulsifiers.

[0067] Examples of anionic surfactants include fatty acid oils such as sodium oleate and potassium castor oil, alkyl sulfate esters such as sodium lauryl sulfate, ammonium lauryl sulfate, and triethanolamine lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, alkylnaphthalene sulfonates, alkanesulfonates, dialkyl sulfosuccinates such as sodium dioctyl sulfosuccinate, alkenyl succinates (dipotassium salts), alkyl phosphate esters, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkylphenyl ether sulfates, polyoxyethylene alkyl ether sulfates such as sodium polyoxyethylene lauryl ether sulfate, and polyoxyethylene alkyl sulfates.

[0068] Cationic surfactants include alkylamine salts such as laurylamine acetate and stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride. Amphoteric surfactants include lauryldimethylamine oxide, phosphate esters, and phosphite esters.

[0069] The above surfactants may be used individually or in combination of two or more. From the viewpoint of dispersion stability during polymerization, it is preferable to use anionic surfactants.

[0070] The shape of the particle 32 may be spherical, flattened, red blood cell-shaped (bowl-shaped), semicircular, etc., but a spherical shape is preferred.

[0071] The particle diameter of the child particles 32 is smaller than that of the mother particles 31. The ratio of the average particle diameter of the child particles 32 to the particle diameter of the mother particles 31, as determined by observation at a magnification of 30,000x using a scanning electron microscope (SEM), may be between 8.0 and 20.0 from the viewpoint of the adsorption of child particles to the mother particles 31. The above particle diameter ratio may be 10.0 or greater, or 15.0 or less. The specific method for measuring the above ratio is shown in the examples.

[0072] The average particle diameter of the sub-particles 32, as determined by observation at a magnification of 30,000x using a scanning electron microscope (SEM), is preferably 200 to 400 nm. When the average particle diameter is 200 nm or more, the sub-particles 32 are more likely to function as spacers. When the average particle diameter is 400 nm or less, the sub-particles 32 are less likely to detach from the parent particle 31. From this viewpoint, the average particle diameter may be 300 nm or more, or 370 nm or less. The specific method for measuring the average particle diameter is shown in the examples.

[0073] The coverage rate of the surface of the mother particle 31 by the child particle 32 is preferably 30.0% or more. When the coverage rate is within this range, the uncovered parts of the mother particle 31 become bonding points, preventing or suppressing adhesion between conductive particles, thus making defects due to short circuits less likely and improving the dispersibility of the conductive particles. From a similar viewpoint, the above coverage rate may be 50.0% or more. The upper limit of the above coverage rate is, for example, 60.0%. That is, the above coverage rate may be 30.0 to 60.0%. Here, the above coverage rate is the average of the coverage rates of multiple conductive particles, and is an area ratio obtained by analyzing SEM images obtained by observing the conductive particles with an SEM (scanning electron microscope) at a magnification of 5000x. A specific method for measuring the above coverage rate is shown in the examples.

[0074] The Coefficient of Variation (CV) value of the above coverage rate is preferably 25.0% or less. With such a CV value, it is unlikely that there will be excessively insufficiently covered particles, thus reducing the likelihood of problems caused by adhesion between conductive particles. From a similar viewpoint, the above CV value may be 20.0% or less or 15.0% or less. The lower limit of the above CV value is, for example, 8.0%. That is, the above CV value may be between 8.0% and 25.0%. Here, the CV value of the coverage rate is the value obtained by dividing the standard deviation of the coverage rate by the above coverage rate (mean value).

[0075] The child particle 32 may be attached to the mother particle 31 via a polymer electrolyte. The polymer electrolyte will be described later.

[0076] The subparticles 32 may be surface-treated. For example, the surface of the subparticles 32 may be covered with a silicone oligomer. The weight-average molecular weight of the silicone oligomer is preferably 500 to 4000. The silicone oligomer preferably has functional groups that react with the polymer electrolyte or functional groups introduced to the subparticles, as described later. Examples of such functional groups include silanol groups, glycidyl groups, carboxyl groups, amino groups, and isocyanate groups. Among these, silanol groups or glycidyl groups are preferred. In the silicone oligomer coating the subparticles, the above functional groups may be in a state of reaction with the polymer electrolyte or functional groups introduced to the subparticles.

[0077] The surface treatment method for the subparticles 32 is not particularly limited, but a convenient method is to mix a 5-100% by mass solution of silicone oligomer with a dispersion of particles (e.g., fine particles) that will become the subparticles 32 while stirring in a heated nitrogen atmosphere, and then stir.

[0078] The ratio of the average particle diameter of subparticles 32 in methyl ethyl ketone to the average particle diameter in water (hereinafter referred to as the "swelling ratio") may be greater than 1.15 and less than or equal to 1.30. Here, the average particle diameter in water and the average particle diameter in methyl ethyl ketone are the particle diameters at 50% of the cumulative value (by volume) in the particle size distribution determined by laser diffraction particle size distribution measurement. If the above swelling ratio of subparticles 32 is greater than 1.15, the subparticles 32 swell with methyl ethyl ketone. Subparticles 32 with a swelling ratio greater than 1.15 tend to swell not only with methyl ethyl ketone but also with organic solvents having an SP value close to that of methyl ethyl ketone (e.g., acetone, ethyl acetate, toluene, etc.). From the viewpoint of making it easier to obtain the above-mentioned effects, the above swelling ratio may be 1.17 or greater or 1.20 or greater. From the viewpoint of manufacturing stability of subparticles and adsorption stability to mother particles, the above swelling ratio may be 1.25 or less or 1.20 or less. From these perspectives, the above swelling ratio may be greater than 1.15 and less than or equal to 1.25, greater than 1.15 and less than or equal to 1.20, 1.17 to 1.30, 1.17 to 1.25, 1.17 to 1.20, 1.20 to 1.30, or 1.20 to 1.25.

[0079] The conductive particles P comprising the parent particles 31 and child particles 32 described above preferably have a moderately hydrophilic surface from the viewpoint of obtaining a connection structure with superior conductivity and insulation resistance. Specifically, when a film made of conductive particles P is formed, it is preferable that the contact angle of the surface of the film with respect to water is 85 to 115°. The above contact angle may be 90° or more or 100° or more. The above contact angle may be 110° or less or 105° or less. It is preferable that the above contact angle is not 15° or more greater than the contact angle of the surface of the circuit connection adhesive film (surface of the conductive adhesive layer) with respect to water in which the conductive particles P are used. The above contact angle can be measured by the method described in the examples.

[0080] The conductive particles P described above are obtained by coating a conductive particle, which serves as the mother particle, with a particle that serves as the daughter particle (e.g., a fine particle). As a coating method, it is preferable to use the method described below from the viewpoint of eliminating aggregation between particles.

[0081] First, the surface of the conductive particles that will become the mother particles 31 is treated with a compound having a specific functional group.

[0082] When conductive particles have a gold or palladium layer on their surface, they may be treated with a compound having at least one group selected from the group consisting of mercapto groups, sulfide groups, and disulfide groups, and at least one group selected from the group consisting of hydroxyl groups, carboxyl groups, alkoxy groups, and alkoxycarbonyl groups. By treating conductive particles with such a compound, the mercapto group, sulfide group, or disulfide group forms a coordination bond with the gold or palladium, thereby imparting a hydroxyl group, carboxyl group, alkoxy group, or alkoxycarbonyl group to the conductive particles. Examples of such compounds include mercaptoacetic acid, 2-mercaptoethanol, methyl mercaptoacetate, mercaptosuccinic acid, thioglycerin, and cysteine.

[0083] When conductive particles have a nickel layer on their surface, they may be treated with a compound having at least one group selected from the group consisting of mercapto groups, sulfide or disulfide groups, carboxyl groups, silanol groups, hydroxyl groups, and nitrogen-containing groups, and at least one group selected from the group consisting of hydroxyl groups, carboxyl groups, alkoxy groups, and alkoxycarbonyl groups. By treating conductive particles with such a compound, the silanol group, hydroxyl group, or nitrogen-containing group forms a strong bond with nickel, thereby imparting hydroxyl groups, carboxyl groups, alkoxy groups, or alkoxycarbonyl groups to the conductive particles. Examples of such compounds include carboxybenzotriazole.

[0084] One method for treating conductive particles with the above-mentioned compounds is to prepare a 10-100 mmol / l solution of a compound such as mercaptoacetic acid or carboxybenzotriazole in an organic solvent such as methanol or ethanol, and then disperse the conductive particles in the solution.

[0085] Next, the treated conductive particles are coated with fine particles. When the pH is in the neutral range, the surface potential (zeta potential) of conductive particles having hydroxyl groups, carboxyl groups, alkoxy groups, alkoxycarbonyl groups, etc., is negative. On the other hand, the surface potential of fine particles having hydroxyl groups is also usually negative. Since it is difficult to coat particles with a negative surface potential with particles that also have a negative surface potential, a method of coating conductive particles with fine particles via a polymer electrolyte is preferred.

[0086] A method for coating conductive particles with fine particles via a polymer electrolyte includes, for example, the steps of (1) dispersing treated conductive particles in a polymer electrolyte solution and adsorbing the polymer electrolyte onto the surface of the conductive particles, and (2) dispersing the conductive particles with the adsorbed polymer electrolyte in a fine particle dispersion solution and adsorbing the fine particles onto the surface of the polymer electrolyte.

[0087] When implementing the above method, you may refer to the layer-by-layer assembly method. The layer-by-layer assembly method is a method for forming organic thin films that was published by G. Decher et al. in 1992 (Thin Solid Films, 210 / 211, p831 (1992)).

[0088] Excess polymer electrolyte or fine particles can be washed away by rinsing with a solvent after adsorbing a polymer electrolyte onto the surface of conductive particles, or after adsorbing fine particles onto the surface of a polymer electrolyte. Examples of solvents that can be used include water, alcohol, and acetone.

[0089] As the polymer electrolyte, a polymer can be used that ionizes in aqueous solution and has a charged functional group in its main chain or side chain. Such a polymer electrolyte is preferably a polycation. As the polycation, those that can carry a positive charge, such as polyamines, can be used. Specifically, examples include polyethyleneimine (PEI), polyallylamine hydrochloride (PAH), polydiallyldimethylammonium chloride (PDDA), polyvinylpyridine (PVP), polylysine, polyacrylamide, and copolymers containing at least one of these. Among polymer electrolytes, polyethyleneimine (PEI) has a high charge density and strong bonding force.

[0090] From the viewpoint of avoiding electromigration and corrosion, the polymer electrolyte may not contain alkali metal (Li, Na, K, Rb, Cs) ions, alkaline earth metal (Ca, Sr, Ba, Ra) ions, or halide ions (fluoride ions, chloride ions, bromide ions, iodide ions).

[0091] The polymer electrolyte may be soluble in water or an organic solvent such as alcohol. The molecular weight of the polymer electrolyte may be between 1,000 and 200,000. When the molecular weight is 1,000 or higher, the dispersibility of conductive particles is sufficient, and aggregation tends to be less likely.

[0092] A polymer electrolyte solution is prepared by dissolving a polymer electrolyte in a mixed solvent of water and a water-soluble organic solvent. Examples of water-soluble organic solvents include methanol, ethanol, propanol, acetone, dimethylformamide, and acetonitrile. The concentration of the polymer electrolyte in the solution may be 0.001 to 10% by mass. The pH of the polymer electrolyte solution is not particularly limited.

[0093] By using this polymer electrolyte, the coverage rate and the CV value of the coverage rate can be increased. As a result, it becomes easier to ensure insulation even with a narrow electrode pitch, and it becomes easier to reduce the connection resistance between electrically connected electrodes.

[0094] The coverage rate and its coefficient of variation (CV) can also be adjusted by controlling the type, molecular weight, and concentration of the polymer electrolyte. Specifically, when using polymer electrolytes with high charge density, such as polyethyleneimine, the coverage rate by subparticles tends to be high, while when using polymer electrolytes with low charge density, such as polydiallyldimethylammonium chloride, the coverage rate by subparticles tends to be low. Furthermore, when the molecular weight of the polymer electrolyte is large, the coverage rate by subparticles tends to be high, while when the molecular weight of the polymer electrolyte is small, the coverage rate by subparticles tends to be low.

[0095] The bonding between the child particles and the mother particles can also be strengthened by coating the conductive particles with fine particles and then performing heat drying. The heating temperature may be between 60 and 120°C, and the heating time may be between 60 and 180 minutes. When the heating temperature is 60°C or higher, or the heating time is 60 minutes or higher, peeling of the child particles during heat drying is less likely to occur. When the heating temperature is 120°C or lower, or the heating time is 180 minutes or lower, deformation of the mother particles during heat drying is less likely to occur.

[0096] The conductive particles P may be surface-treated with a silane coupling agent, silicone, or other surface treatment agent.

[0097] <Adhesive film for circuit connections> Figure 2 is a schematic cross-sectional view showing one embodiment of a circuit connection adhesive film containing the conductive particles P described above (hereinafter simply referred to as "conductive particles P"). As shown in the figure, the circuit connection adhesive film 11 comprises a release film 12 and a conductive adhesive layer 13 consisting of an adhesive layer in which conductive particles P are dispersed. The circuit connection adhesive film 11 does not necessarily have a release film 12. Although not shown, the circuit connection adhesive film 11 may further have an insulating adhesive layer on the conductive adhesive layer 13, consisting of an adhesive layer in which conductive particles P are not dispersed. For convenience of explanation, a circuit connection adhesive film without a release film may also be referred to as a circuit connection adhesive film 11 below. Note that the adhesive components constituting the conductive adhesive layer are insulating.

[0098] The release film 12 is formed from, for example, polyethylene terephthalate (PET), polyethylene, polypropylene, etc. The release film 12 may contain any filler. The surface of the release film 12 may also be treated with a release treatment, plasma treatment, or the like.

[0099] The conductive adhesive layer 13 contains adhesive components and conductive particles P. Here, adhesive components refer to the components in the adhesive layer that contribute to adhesion. The adhesive components are, for example, thermosetting.

[0100] The adhesive component preferably mainly contains components soluble in organic solvents with an SP value of 8.5 to 10.0. That is, preferably, the component with the highest content ratio among the components included in the adhesive component is soluble in the organic solvent with the above SP value. Specifically, it is more preferable that one or both of the monomer and film-forming material described later are soluble in the organic solvent with the above SP value. Here, "soluble" in an organic solvent means that it dissolves in the organic solvent at 25°C at a concentration of 50% by mass or more.

[0101] The adhesive components include, for example, monomers (polymerizable compounds), curing agents (polymerization initiators, etc.), and film-forming materials. If the adhesive components are thermosetting, the monomers harden by reacting with the curing agent due to heat.

[0102] The monomer can be any polymerizable compound, and may be either a low-molecular-weight compound or a high-molecular-weight compound. For example, the monomer may be an oligomer. The monomer may be used alone or in combination of two or more types. A low-molecular-weight compound and a high-molecular-weight compound may be used in combination as the monomer, or a nonpolymer and a polymer may be used in combination.

[0103] The monomer is, for example, a cationic polymerizable compound. Cationic polymerizable compounds have cationic polymerizable groups such as epoxy groups, oxetanyl groups, and vinyl ether groups. Hereinafter, cationic polymerizable compounds having these polymerizable groups will be referred to as epoxy compounds, oxetane compounds, and vinyl ether compounds, respectively. From the viewpoint of achieving a high crosslink density when cured, it is preferable for cationic polymerizable compounds to have two or more cationic polymerizable groups.

[0104] Examples of epoxy compounds include glycidyl ether-type epoxy compounds and alicyclic epoxy compounds.

[0105] Glycidyl ether type epoxy compounds are compounds having a glycidyl ether group. Examples of glycidyl ether type epoxy compounds include bisphenol type epoxy resins derived from epichlorohydrin and bisphenol compounds (bisphenol A, bisphenol F, etc.); polyglycidyl ethers; novolac type epoxy compounds such as cresol novolac type epoxy resins and phenol novolac type epoxy resins; biphenyl diglycidyl ethers, glycidyl alkyl isocyanurates, polyglycidyl methacrylates, copolymers of glycidyl methacrylates with vinyl monomers copolymerizable thereto, and the like. Glycidyl ether type epoxy compounds may be used individually or in combination of multiple types.

[0106] Alicyclic epoxy compounds are compounds having an alicyclic epoxy group. Examples of alicyclic epoxy compounds include cyclohexene oxide or cyclopentene oxide-containing compounds obtained by oxidizing cyclohexene ring-containing compounds or cyclopentene ring-containing compounds. Specific examples of alicyclic epoxy compounds include 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-methadioxane, 3,4-epoxy-1-methylcyclohexyl-3,4-epoxy-1-methylhexanecarboxylate, 3,4-epoxy-3-methylcyclohexylmethyl-3,4-epoxy-3-methylcyclohexanecarboxylate, 3,4-epoxy-5-methylcyclohexylmethyl-3,4-epoxy-5-methylcyclohexanecarboxylate, and 3,4 Examples include epoxy-6-methylcycloexylcarboxylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 6-methyl-3,4-epoxycyclohexylmethyl-6-methyl-3,4-epoxycyclohexanecarboxylate, ethylenebis(3,4-epoxycyclohexanecarboxylate), dicyclopentadiene diepoxide, bis(3,4-epoxycyclohexylmethyl) adipate, and methylenebis(3,4-epoxycyclohexane). Alicyclic epoxy compounds may be used individually or in combination of multiple types.

[0107] Oxetane compounds are compounds having oxetanyl groups. From the viewpoint of even better curability, oxetane compounds are preferably aliphatic or alicyclic compounds having 2 to 6 oxetanyl groups and 1 to 6 hydroxyl groups. Examples of oxetane compounds include 1,4-di[(3-oxetanyl-n-butoxy)methyl]benzene, 4,4'-bis[(3-oxetanyl-n-butoxy)methyl]biphenyl, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, 3-ethyl-3-hydroxymethyloxetane, and 2-ethylhexyloxetane. Oxetane compounds may be used individually or in combination of multiple types.

[0108] Vinyl ether compounds are compounds containing a vinyl ether group. Examples of vinyl ether compounds include 1,4-butanediol divinyl ether, cyclohexanedimethanol divinyl ether, diethylene glycol divinyl ether, and triethylene glycol divinyl ether. Vinyl ether compounds may be used individually or in combination of multiple types.

[0109] The content of the cationic polymerizable compound may be 10% by mass or more or 25% by mass or more, based on the total mass of the conductive adhesive layer, from the viewpoint of obtaining even better physical properties (glass transition temperature, elastic modulus, etc.) after curing of the conductive adhesive layer. The content of the cationic polymerizable compound may be 90% by mass or less or 75% by mass or less, based on the total mass of the conductive adhesive layer, from the viewpoint of suppressing shrinkage of the conductive adhesive layer during curing and maintaining adhesive strength. In this specification, the total mass of the conductive adhesive layer means the total mass of the adhesive composition constituting the conductive adhesive layer.

[0110] If the monomer is a cationic polymerizable compound, the curing agent is a cationic polymerization initiator. If the adhesive component is thermosetting, the cationic polymerization initiator is a thermal cationic polymerization initiator.

[0111] Examples of cationic polymerization initiators include onium salts. From the viewpoint of even better storage stability, compounds that exhibit activity at temperatures of 80 to 250°C are preferred, and more specifically, at least one selected from the group consisting of anilinium salts (anilinium salt compounds) and pyridinium salts (pyridinium salt compounds) is more preferred.

[0112] As an anilinium salt, N-alkylanilinium salts, N,N-dialkylanilinium salts, and N,N,N-trialkylanilinium salts are preferred from the viewpoint of lowering the decomposition temperature and further improving curability. Specific examples of anilinium salts include N-benzyl-N,N-dimethylanilinium hexafluoride antimony, N-(4-nitrobenzyl)-N,N-dimethylanilinium hexafluoride antimony, N-(4-methoxybenzyl)-N,N-dimethylanilinium hexafluoride antimony, N-(α-phenylbenzyl)-N,N-dimethylanilinium hexafluoride antimony, N-(α-methylbenzyl)-N,N-dimethylanilinium hexafluoride antimony, N-(1-naphthylmethyl)-N,N-dimethylanilinium hexafluoride antimony, N-cinnamyl-N,N-dimethylanilinium hexafluoride antimony, and onium salts having substituted benzylanilinium cations (e.g., K-PURE CXC-1612 (manufactured by KING Industries, counter anion: SbF6), K-PURE CXC-1738 (KING Examples include K-PURE CXC-1740 (manufactured by KING Industries, counter anion: PF6), K-PURE CXC-1741 (manufactured by KING Industries, counter anion: SbF6), and K-PURE CXC-1821 (manufactured by KING Industries, counter anion: B(C6F5)4). In these compounds, the aromatic ring bonded to the nitrogen atom may be unsubstituted or substituted. Examples of anilinium salts with substituted aromatic rings include N-(1-naphthylmethyl)-N,N-dimethyl(4-bromophenyl)anilinium hexafluoride antimony.

[0113] As an anilinium salts, N-benzyl-N,N-dialkylanilinium salt and N-naphthylmethyl-N,N-dialkylanilinium salt are preferred from the viewpoint of lowering the decomposition temperature and further improving curability, and N-benzyl-N,N-dimethylanilinium salt and N-naphthylmethyl-N,N-dimethylanilinium salt are more preferred. As counter anions for these anilinium salts, SbF6 is preferred from the viewpoint of improving the reaction rate of the cationic polymerization reaction and further improving curability. - It is preferable.

[0114] As pyridinium salts, N-benzylpyridinium salt, N-naphthylmethylpyridinium salt, and N-cinnamylpyridinium salt are preferred from the viewpoint of lowering the decomposition temperature and further improving curability. As counteranions for these pyridinium salts, SbF6 is preferred from the viewpoint of improving the reaction rate of the cationic polymerization reaction and further improving curability. - This is preferred. Specific examples of pyridinium salts include N-benzylpyridinium hexafluoride antimony, N-(4-nitrobenzyl)pyridinium hexafluoride antimony, N-(4-methoxybenzyl)pyridinium hexafluoride antimony, N-(α-phenylbenzyl)pyridinium hexafluoride antimony, N-(α-methylbenzyl)pyridinium hexafluoride antimony, N-(1-naphthylmethyl)pyridinium hexafluoride antimony, and N-cinnamylpyridinium hexafluoride antimony. The pyridinium ring in these compounds may be unsubstituted or substituted. Examples of pyridinium salts with substituted pyridinium rings include N-(α-phenylbenzyl)-4-cyanopyridinium hexafluoride antimony, naphthylmethyl-2-cyanopyridinium hexafluoride antimony, and cinnamyl-2-cyanopyridinium hexafluoride antimony.

[0115] From the viewpoint of ensuring that the adhesive composition hardens easily, the content of the cationic polymerization initiator is preferably 0.05 parts by mass or more, and more preferably 0.1 parts by mass or more, per 100 parts by mass of the cationic polymerizable compound. From the viewpoint of improving compatibility, the content of the cationic polymerization initiator is preferably 30 parts by mass or less, and more preferably 15 parts by mass or less, per 100 parts by mass of the cationic polymerizable compound.

[0116] Cationic polymerization initiators may be used alone or in combination of multiple types. Furthermore, to increase the cation generation efficiency of the cationic polymerization initiator and the reaction rate of the cationic polymerizable compound, a chain transfer agent may be used in addition to the cationic polymerizable compound and the cationic polymerization initiator as appropriate. The chain transfer agent is not particularly limited as long as it is a protic compound; known compounds can be used. Examples of chain transfer agents include alcohols such as cyclohexendiol, 2,3-butanediol, ethylene glycol, diethylene glycol, and triethylene glycol, and their derivatives.

[0117] Film-forming materials are materials used for the purpose of increasing viscosity or improving film-forming properties, and are, for example, polymers. Examples of film-forming materials include polyimide, polyamide, phenoxy resin, polymethacrylate, polyacrylate, polyurethane, polyester, polyester urethane, polyvinyl butyral, SBS (styrene-butadiene-styrene copolymer) and its epoxy modified form, SEBS (styrene-ethylene-butylene-styrene copolymer) and its modified form, NBR (acrylonitrile-butadiene copolymer) and its hydrogenated form, etc. These polymers may have siloxane bonds or fluorine substituents. Such polymers can be suitably used as adhesive compositions if the resins being mixed are completely miscible or if microphase separation occurs, resulting in turbidity. Film-forming materials may be used individually or in combination of multiple types.

[0118] The weight-average molecular weight of the film-forming material may be 5,000 or more, or 10,000 or more, from the viewpoint of easily improving film-forming properties and being able to set a wide range of melt viscosity that affects the fluidity of the conductive adhesive layer. The weight-average molecular weight of the film-forming material may be 150,000 or less, or 80,000 or less, from the viewpoint of good compatibility with other components. The weight-average molecular weight of the film-forming material can be calculated by using gel permeation chromatography (GPC) and converting from a calibration curve using standard polystyrene. For example, the following conditions can be used as measurement conditions. (Measurement conditions) Equipment: GPC-8020 manufactured by Tosoh Corporation Detector: RI-8020 manufactured by Tosoh Corporation Column: Gelpack GL-A-160-S + GL-A150 manufactured by Showa Denko Materials Co., Ltd. Sample concentration: 120mg / 3ml Solvent: tetrahydrofuran Injection volume: 60μl Pressure: 30 kgf / cm² 2 Flow rate: 1.00ml / min

[0119] The content of the film-forming material may be 20 to 320 parts by mass per 100 parts by mass of monomer (e.g., cationic polymerizable compound), from the viewpoint of fluidity and adhesion of the conductive adhesive layer.

[0120] The content of conductive particles P may be 0.1 to 30 volume percent or 0.1 to 10 volume percent relative to the total volume of the conductive adhesive layer. When the content is 0.1 volume percent or more, conductivity tends to improve further. When the content is 30 volume percent or less, the effect of suppressing short circuits in the circuit tends to be more pronounced. In this specification, the total volume of the conductive adhesive layer refers to the total volume of the adhesive composition constituting the conductive adhesive layer. The above content (volume %) can be determined, for example, based on the volume of each component contained in the conductive adhesive layer at 23°C. The volume of each component can be converted from mass to volume using specific gravity. The volume of each component can also be determined as the increase in volume when the component is placed in a graduated cylinder or the like containing a solvent (water, alcohol, etc.) that thoroughly wets the component without dissolving or swelling it.

[0121] The conductive adhesive layer 13 may further contain various known additives, as long as they do not impair the effects of the invention. Examples of additives include inorganic fillers, reinforcing agents, colorants, stabilizers (heat stabilizers, weather resistance improvers, etc.), bulking agents, viscosity modifiers, tackifiers such as terpene phenol copolymers, terpene resins, rosin derivatives, and alicyclic hydrocarbon resins, flame retardants, ultraviolet absorbers, antioxidants, discoloration inhibitors, antibacterial agents, antifungal agents, anti-aging agents, antistatic agents, plasticizers, lubricants, foaming agents, and mold release agents.

[0122] The thickness of the conductive adhesive layer 13 may be, for example, 10 to 50 μm. If the conductive adhesive layer 13 is 10 μm or thicker, when used as a circuit connection material, the circuit connection material can fill the spaces between circuit electrodes well. If the thickness of the conductive adhesive layer 13 is 50 μm or less, when used as a circuit connection material, leakage of the circuit connection material from between circuit electrodes can be suppressed.

[0123] The circuit connection adhesive film 11 described above is an adhesive film used for connecting circuits. The circuit connection adhesive film 11 may or may not have anisotropic conductivity. That is, the circuit connection adhesive film 11 may be an anisotropic conductive adhesive film or a non-anisotropic conductive (for example, isotropic conductive) adhesive film. The circuit connection adhesive film 11 may be used to electrically connect a first member having a first electrode and a second member having a second electrode by heat-pressing them together with the circuit connection adhesive film 11 interposed between the first member and the second member.

[0124] <Method for manufacturing adhesive film for circuit connections> The circuit connection adhesive film 11 shown in Figure 2 can be manufactured by a method comprising the steps of applying an adhesive paste W, which will be the material for forming the conductive adhesive layer 13, onto a release film 12 (coating step), and drying the coating obtained by the coating.

[0125] The adhesive paste W contains an adhesive component, conductive particles P dispersed in the adhesive component, and an organic solvent. The adhesive paste W is prepared, for example, by dissolving or dispersing the adhesive component (monomer, curing agent, film-forming material, etc.) and conductive particles P in an organic solvent by stirring, mixing, kneading, etc. The organic solvent may be, for example, an organic compound with an SP value of 8.5 to 10.0. Examples of such organic solvents include acetone, methyl ethyl ketone, ethyl acetate, and toluene.

[0126] The viscosity of the adhesive paste W can be adjusted according to the application, application method, etc. The viscosity of the adhesive paste W may be 10 mPa·s to 10,000 mPa·s, and from the viewpoint of suppressing separation of the components in the adhesive paste W and improving compatibility, it may be 50 mPa·s to 5,000 mPa·s. From the viewpoint of improving the appearance of the adhesive film 11 for circuit connection, the viscosity of the adhesive paste W may be 100 mPa·s to 3,000 mPa·s.

[0127] The coating method for the adhesive paste W is not limited to the above, and known methods can be used. Examples of coating methods include spin coating, roller coating, bar coating, dip coating, microgravure coating, curtain coating, die coating, spray coating, doctor coating, kneader coating, flow coating, screen printing, and casting. Among these, bar coating, die coating, and microgravure coating are suitable for producing the adhesive film 11 for circuit connection. From the viewpoint of accuracy of film thickness, the microgravure coating method is particularly suitable.

[0128] The drying method for the coating film is not particularly limited and may be, for example, hot air drying. The drying temperature of the adhesive paste W is, for example, 20 to 80°C. The conductive adhesive layer 13 is formed when the coating film is dried.

[0129] If the circuit connection adhesive film 11 further comprises an insulating adhesive layer, for example, the insulating adhesive layer may be formed on the conductive adhesive layer 13 after the conductive adhesive layer 13 has been formed. The insulating adhesive layer may be formed on the conductive adhesive layer 13 by laminating a separately prepared insulating adhesive layer onto the conductive adhesive layer 13, or the insulating adhesive layer may be formed on the conductive adhesive layer 13 by applying an adhesive paste, which will be the material for the insulating adhesive layer, onto the conductive adhesive layer 13 and drying it.

[0130] <Connection Structure> Figure 3 is a schematic cross-sectional view showing one embodiment of the connection structure. As shown in the figure, the connection structure 1 comprises a first member 4 having a first electrode 42, a second member 5 having a second electrode 52, and a connecting portion 6 disposed between the first member 4 and the second member 5, which electrically connects the first electrode 42 and the second electrode 52 to each other. The first member 4 and the second member 5 are arranged such that the first electrode 42 and the second electrode 52 face each other.

[0131] The first component 4 is, for example, a circuit component. The first component 4 comprises, for example, a first substrate 41 (for example, a circuit board) and a first electrode 42 (for example, a circuit electrode) formed on the main surface 41a of the first substrate 41. An insulating layer (not shown) may be formed on the main surface 41a of the first substrate 41.

[0132] The second component 5 is, for example, a circuit component. The second component 5 comprises, for example, a second substrate 51 (e.g., a circuit board) and a second electrode 52 (e.g., a bump electrode) formed on the main surface 51a of the second substrate 51. An insulating layer (not shown) may also be formed on the main surface 51a of the second substrate 51.

[0133] The first member 4 and the second member 5 are not particularly limited as long as they are members on which electrodes requiring electrical connection are formed. Examples of members on which electrodes are formed include inorganic substrates such as semiconductors, glass, and ceramics; polyimide substrates represented by TCP, FPC, COF, etc.; substrates on which electrodes are formed on films such as polycarbonate, polyester, and polyethersulfone; and printed circuit boards. Multiple combinations of these can also be used.

[0134] The connecting portion 6 is a part formed by curing the circuit connection adhesive film 11, and contains cured material of the circuit connection adhesive film 11. The connecting portion 6 contains, for example, conductive particles P and an insulating substance 7 formed by curing components other than the conductive particles (such as adhesive components) in the circuit connection adhesive film 11. The connecting portion 6 spreads in layers along the main surface 41a of the first member 4 and the main surface 51a of the second member 5.

[0135] The conductive particles P are placed between the first electrode 42 and the second electrode 52. Due to compression, some of the child particles 32 of the conductive particles P are detached, and the mother particles 31 are slightly flattened and in contact with the first electrode 42 and the second electrode 52. This achieves an electrical connection between the first electrode 42 and the second electrode 52. The conductive particles P may be placed not only between the opposing first electrode 42 and second electrode 52, but also between the main surface 41a of the first substrate 41 and the main surface 51a of the second substrate 51.

[0136] <Method for manufacturing a connecting structure> The manufacturing method for the connecting structure 1 includes, for example, the step of heat-pressing a first member 4 and a second member 5 with a circuit connection adhesive film 11 interposed between the first member 4 and the second member 5, and electrically connecting the first electrode 42 and the second electrode 52 to each other. The manufacturing method for the connecting structure 1 will be described below with reference to Figure 4.

[0137] Figure 4 is a schematic cross-sectional view showing the manufacturing process of the connecting structure 1. In the example shown in the figure, first, the first member 4 and the adhesive film 11 for circuit connection are prepared (see Figure 4(a)).

[0138] Next, the circuit connection adhesive film 11 is placed on the main surface 41a of the first member 4. If the circuit connection adhesive film 11 is a laminate of a release film 12 and a conductive adhesive layer 13, as shown in Figure 1, the laminate is placed on the first member 4 with the conductive adhesive layer 13 side of the laminate facing the first member 4.

[0139] Next, the circuit connection adhesive film 11 is pressed in the directions of arrows A and B in Figure 4(a) to temporarily connect the circuit connection adhesive film 11 to the first member 4 (see Figure 4(b)). At this time, heating may be performed along with the pressurization.

[0140] Next, as shown in Figure 4(c), the second member 5 is placed on the circuit connection adhesive film 11 placed on the first member 4, with the second electrode 52 facing the first member 4 (i.e., the first electrode 42 and the second electrode 52 are positioned opposite each other). If the circuit connection adhesive film 11 is laminated on a support (not shown), the support is peeled off before placing the second member 5 on the circuit connection adhesive film 11.

[0141] Then, while heating the circuit connection adhesive film 11, pressure is applied in the directions of arrows A and B in Figure 4(c). This hardens the circuit connection adhesive film 11, and the connection is made. As a result, a connection structure 1 as shown in Figure 3 is obtained.

[0142] The heating temperature of the circuit connection adhesive film 11 is preferably above the temperature at which polymerization-active species are generated in the curing agent and polymerization of monomers (polymerizable compounds) begins. This heating temperature is, for example, 80°C to 200°C, and preferably 100°C to 180°C. The heating time is, for example, 0.1 seconds to 30 seconds, and preferably 1 second to 20 seconds. [Examples]

[0143] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0144] <Manufacturing Examples 1-8> (Preparation of insulating microparticles 1-8) The monomers shown in Tables 1-3 were polymerized using emulsion polymerization. Specifically, 400 g of pure water was first added to a synthesis flask, and then the materials shown in Tables 1-3 were added to the flask all at once according to the molar amounts shown in Tables 1-3. These were heated at 70°C for 8 hours while stirring. The stirring speed was 300 rpm. This produced insulating fine particles 1-8, respectively.

[0145] (Measurement of average particle size and morphology using SEM) Using a field emission scanning electron microscope (SU-8020, Hitachi High-Tech Corporation), insulating particles 1-8 were observed at a magnification of 30,000x. The obtained SEM images were analyzed using XG VisionEditor (image analysis software from Keyence Corporation) to determine the average particle size (SEM average particle size d1) and degree of irregularity of insulating particles 1-8 based on SEM observation.

[0146] Specifically, first, the insulating microparticles were dried, and then SEM images of the dried insulating microparticles were obtained. Next, using latex particles (CLINTEX series, particle size: 0.3 μm) manufactured by JSR Life Sciences Co., Ltd. as a standard sample, one particle similar to the standard sample was extracted from the SEM image. Then, between the center point of the extracted particle and a point on the edge of the particle, 10 to 36 intersection points were identified, and between 5 and 18 diameters d were selected. X (The distance between the two intersection points on the above line), and a maximum of 36 radii r X The distance between the center point and the intersection point was calculated. Then, the obtained diameter d X The average value d Y Find d Y Radius r of a virtual circle (true circle) with diameter Y (d Y ( / 2) and the radius r of the above particle X The absolute value of the difference was calculated. The average value of this difference was taken as the average strain D of the particle, and the average strain D and the radius r of the virtual circle were calculated. Y Using the following formula, the degree of particle irregularity was calculated. Deformation degree = average strain D / radius r of virtual circle Y ×100 The above procedure was performed on 100 arbitrarily selected particles, and the calculated d Y The average values ​​of the particle size and shape deviation were used as the SEM average particle size d1 and shape deviation for insulating fine particles 1-8. The results are shown in Tables 1-3.

[0147] (Measurement of swelling ratio) After measuring the average particle size d2 of insulating particles 1-8 in water, insulating particles 1-8 were immersed in methyl ethyl ketone and treated in an ultrasonic bath with an ultrasonic frequency of 40 kHz and an output of 120 W for 5 minutes. The average particle size d3 of insulating particles 1-8 in methyl ethyl ketone was then measured. Based on the obtained average particle sizes d2 and d3, the swelling ratio (ratio of average particle size d3 to average particle size d2, d3 / d2) of insulating particles 1-8 was determined. The specific method for measuring the average particle size is shown below.

[0148] The particles to be measured (any of insulating microparticles 1 to 8) were added to a solvent (water or methyl ethyl ketone) in an amount ranging from 0.1 to 15.0% by mass so that the pH of the sample solution was 7.0 to 8.0, and then dispersed. Next, the particle size distribution was measured at 25.0°C using a laser diffraction particle size analyzer Microtrac MT3300EXII (manufactured by Microtrac-Bell Co., Ltd., product name). The refractive index was set to 1.59 for insulating microparticles 1 to 6 (polystyrene microparticles) and to 1.49 for insulating microparticles 7 to 8 (polymethyl methacrylate microparticles). The particle size at 50% of the cumulative value (by volume) in the obtained particle size distribution was defined as the average particle size.

[0149] (Measurement of glass transition temperature) The glass transition temperatures (Tg) of insulating fine particles 1-8 were measured using a differential scanning calorimeter (DSC) Q1000 (manufactured by TA Instruments Japan Co., Ltd.). The results are shown in Tables 1-3.

[0150] [Table 1]

[0151] [Table 2]

[0152] [Table 3]

[0153] The details of the materials shown in Tables 1-3 are as follows: (Non-crosslinkable monomers) • Styrene: Manufactured by Fujifilm Wako Pure Chemical Corporation Butyl acrylate: Manufactured by Fujifilm Wako Pure Chemical Corporation • Methyl methacrylate: Manufactured by Mitsubishi Gas Chemical Company, Inc. • Glycidyl methacrylate: Manufactured by Fujifilm Wako Pure Chemical Corporation • 3-Methacryloxypropylmethyldimethoxysilane: Manufactured by Shin-Etsu Chemical Co., Ltd., Product name: KBM-502 • 3-Methacryloxypropyltrimethoxysilane: Manufactured by Shin-Etsu Chemical Co., Ltd., Product name: KBM-503 • Sodium methacrylate: Manufactured by Sigma-Aldrich Co., Ltd. • Sodium styrene sulfonate: Manufactured by Fujifilm Wako Pure Chemical Corporation • Mono(2-hydroxyethyl methacrylate) phosphate: Manufactured by Johoku Chemical Industry Co., Ltd., Product name: JAMP-514 (Cross-linkable monomer) • Divinylbenzene: Manufactured by Nippon Steel Chemical Co., Ltd., Product name: Divinylbenzene (DVB-960) • Diethylene glycol dimethacrylate: Manufactured by Tokyo Chemical Industry Co., Ltd. Made (Radical polymerization initiator) • Potassium peroxodisulfate: Manufactured by Fujifilm Wako Pure Chemical Corporation • 2,2'-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate: Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Product name: VA-057 (emulsifier) • 30% solution of triethanolamine lauryl sulfate: Manufactured by Kao Corporation, product name: Emal TD

[0154] <Comparative Examples 1-4 and Examples 1-4> (Preparation of conductive particles 1-8) [Preparation of parent particle 1] Plastic particles with an average particle size of 3.0 μm were prepared, consisting of polymers of monomers having two acryloyl groups (bifunctional acrylic monomers). The hardness of the plastic particles was evaluated by the elastic modulus (hereinafter referred to as the "20% K value") when the particles were compressed at room temperature (25°C) and deformed by 20%. The 20% K value was 2.0 GPa.

[0155] A nickel metal layer with a thickness of 100 nm was formed on the surface of the above-mentioned plastic particles by electroless plating. This resulted in conductive master particles 1 (particle diameter: approximately 3.1 μm) consisting of plastic particles and a nickel metal layer covering the surface of the plastic particles. The thickness of the nickel metal layer was measured by dispersing the particles in a casting resin to prepare a casting sample, polishing the surface of the obtained casting sample to expose the cross-section of the particles, and observing the cross-section of the particles using a SEM (SU-8020, Hitachi High-Tech Corporation). The thickness is the average of five measurements.

[0156] [Preparation of Silicone Oligomer 1] A solution containing 118 g of 3-glycidoxypropyltrimethoxysilane and 5.9 g of methanol was added to a glass flask equipped with a stirrer, condenser, and thermometer. 5 g of activated clay and 4.8 g of distilled water were further added to this glass flask, and the mixture was stirred at 75°C for a set period of time to obtain silicone oligomer 1 with a weight-average molecular weight of 1300. The obtained silicone oligomer 1 has either a methoxy group or a silanol group as a terminal functional group that reacts with a hydroxyl group. Methanol was added to the solution of the obtained silicone oligomer 1 to prepare a treatment solution with a solid content of 20% by mass. The weight-average molecular weight of silicone oligomer 1 was measured by gel permeation chromatography (GPC) and calculated by conversion using a calibration curve for standard polystyrene. The GPC conditions are shown below. -GPC conditions Equipment: GPC-8020 manufactured by Tosoh Corporation Detector: RI-8020 manufactured by Tosoh Corporation Column: Gelpack GL-A-160-S + GL-A150 manufactured by Showa Denko Materials Co., Ltd. Sample concentration: 120mg / 3ml Solvent: tetrahydrofuran Injection volume: 60μl Pressure: 30 kgf / cm² 2 Flow rate: 1.00ml / min

[0157] [Preparation of conductive particles 1-8] A reaction solution was prepared by dissolving 8 mmol of mercaptoacetic acid in 200 ml of methanol. Next, 10 g of mother particle 1 was added to the reaction solution, and the surface of mother particle 1 was treated (first treatment) by stirring at room temperature for 2 hours using a three-one motor and a 45 mm diameter stirring blade. Subsequently, the treated particles were removed from the stirred solution, washed with methanol, and then filtered using a 3 μm pore size membrane filter (Millipore). This yielded 10 g of particles (particle 1A) having carboxyl groups on their surface.

[0158] Next, a 30% by mass polyethyleneimine aqueous solution with a weight-average molecular weight of 70,000 (manufactured by Wako Pure Chemical Industries, Ltd.) was diluted with methanol to obtain 0.1% by mass polyethyleneimine aqueous solution and 0.01% by mass polyethyleneimine aqueous solution. The 0.1% by mass polyethyleneimine aqueous solution was used when preparing conductive particles 1-6 and 8, and the 0.01% by mass polyethyleneimine aqueous solution was used when preparing conductive particle 7.

[0159] Next, 10 g of particle 1A was added to a 0.1% by mass polyethyleneimine aqueous solution or a 0.01% by mass polyethyleneimine aqueous solution and stirred at room temperature for 15 minutes to perform surface treatment (second treatment) of particle 1A. Then, the treated particles were removed from the stirred solution and filtered using a 3 μm pore size membrane filter (Millipore). The filtered particles were placed in 450 g of methanol and stirred at room temperature for 5 minutes. The particles were then removed from the methanol and filtered using a 3 μm pore size membrane filter (Millipore), and washed twice on the membrane filter with 450 g of methanol. This removed polyethyleneimine that was not adsorbed on particle 1A, and particles coated with an amino group-containing polymer (particle 1B) were obtained.

[0160] Next, insulating microparticles 1 to 8 were treated with silicone oligomer 1 to prepare methanol dispersions of microparticles (microparticles 1A to 8A) having glycidyl group-containing oligomers on their surface.

[0161] Next, particle 1B was immersed in methyl ethyl ketone, and then a methyl ethyl ketone dispersion of fine particles 1A to 8A was added to this solution to obtain conductive particles in which any of the insulating fine particles 1 to 8 were used as subparticles. In this process, the amount of methyl ethyl ketone dispersion added was sufficient to completely cover the surface of the mother particle with subparticles (including unadsorbed subparticles).

[0162] Next, the obtained conductive particles were treated with 315 g of a solution (solid content concentration: 3.0 mass%) prepared by dissolving poly(dimethyldimethoxylane) (weight-average molecular weight Mw: 800-1200) in IPA (isopropyl alcohol), and washed to hydrophobize the surface of the conductive particles. Subsequently, conductive particles 1-8 were prepared by heating and drying under vacuum conditions at 100°C for 90 minutes.

[0163] (Rating 1) [Measurement of coverage and its CV value] The coverage and CV values ​​of conductive particles 1 to 8 were measured using the following method. First, the conductive particles were observed at a magnification of 5000x using a field emission scanning electron microscope (SU-8020, Hitachi High-Tech Corporation) to obtain SEM images. Next, the SEM images were binarized using XG VisionEditor (image analysis software manufactured by Keyence Corporation). Then, one conductive particle was extracted from the binarized SEM image, and a circle with a diameter equal to the radius of the outer circle of the conductive particle (a circle concentric with the outer circle) was defined as the measurement circle. The area S1 of the measurement circle and the sum of the areas S2 representing the insulating fine particles within the measurement circle were determined, and the coverage of the extracted particle (coverage of the parent particle by the child particles) was calculated using the following formula. Coverage rate (%)=S2 / S1×100 This operation was performed on 100 arbitrarily selected conductive particles, and the coverage rates of the calculated 100 conductive particles were averaged to obtain the coverage rate of conductive particle 1. Furthermore, the CV value of the coverage rate was obtained by dividing the standard deviation of the coverage rates calculated using the above formula by the average value.

[0164] [Measurement of particle size] The average particle diameter of the child particles and the ratio of the average particle diameter of the child particles to the particle diameter of the mother particles were determined for conductive particles 1 to 8 using the following method. For each conductive particle, the particle diameters of five child particles were measured, and the average of these measurements was taken as the average particle diameter of the child particles in that conductive particle. The ratio of the average particle diameter of the child particles to the particle diameter of the mother particles was also determined from the obtained measurements. The above measurement was repeated for 25 conductive particles, and the average values ​​of the average particle diameter of the child particles and the ratio of the average particle diameter of the child particles to the particle diameter of the mother particles (average of 25 values) were determined. These were then taken as the average particle diameter of the child particles and the ratio of the average particle diameter of the child particles to the particle diameter of the mother particles for conductive particles 1 to 8.

[0165] [Measuring contact angle] The contact angles of conductive particles 1-8 with respect to water were measured using the following method. First, double-sided tape (product name: Hybon 11-583 (manufactured by Showa Denko Materials Co., Ltd.), width 10.0 mm, length 76.0 mm, thickness 0.14 mm) was attached to the surface of a glass plate. Next, 1.0 g of conductive particles was placed on the double-sided tape, and the conductive particles were spread on the double-sided tape so that the entire surface of the double-sided tape was covered with conductive particles (minimizing gaps between conductive particles as much as possible). Then, excess conductive particles accumulated on the double-sided tape were removed by air blowing (product name: Air Duster AHSze300, Air Water Sol Co., Ltd., spraying time: 30 seconds). This resulted in a laminate composed of glass, double-sided tape, and conductive particles. This laminate was used as a test piece for contact angle measurement.

[0166] Next, using the above-mentioned test specimen, the contact angle with water was measured according to the static testing method described in Section 6 of JIS R 3257 (1999) "Test Method for Wettability of Substrate Glass Surfaces". Specifically, using a contact angle meter "DM-701" manufactured by Kyowa Interface Science Co., Ltd., 6 μL of pure water was dropped onto the film of conductive particles on the sample specimen. The contact angle was measured 2000 ms after dropping. The above procedure was performed a total of 10 times (at 10 locations) at intervals of 7 to 10 mm, and the average value obtained was calculated. This average value was taken as the contact angle of the conductive particles. The above contact angle measurement was performed at room temperature (25°C).

[0167] [Table 4]

[0168] (Preparation of adhesive film for circuit connection) A mixture of K-PURE CXC-1821 (manufactured by KING Industries, counter anion: B(C6F5)4), a thermal cationic polymerization initiator, an alicyclic epoxy compound (product name GT401, manufactured by Daicel Corporation), an oxetane compound (product name OXT-121, manufactured by Toagosei Co., Ltd.), and a phenoxy resin (product name YP-70, manufactured by Toto Kasei Co., Ltd.) was prepared. The mixing ratio (mass ratio) of each component was 5:25:25:50 (thermal cationic polymerization initiator: alicyclic epoxy compound: oxetane compound: phenoxy resin). Conductive particles were then added and dispersed at 8% by volume to obtain an adhesive composition. Conductive particles 1 to 8 described above were used as the conductive particles. Methyl ethyl ketone was used as the solvent.

[0169] Next, the adhesive composition was applied to a 40 μm thick PET (polyethylene terephthalate) film using a coating apparatus, and circuit connection adhesive films 1 to 8 with an adhesive layer thickness of 20 μm were obtained by hot air drying at 70°C for 5 minutes.

[0170] (Rating 2) [Evaluation of conductive particle trapping ability and insulating properties] (1) Fabrication of connecting structures A connection structure was fabricated using the circuit connection adhesive films obtained in Comparative Examples 1-4 and Examples 1-4. Specifically, first, an IC chip was prepared as the first component, having a structure in which two rows of straight-arranged bump electrodes were arranged (outer dimensions: 0.9 mm × 20.3 mm, thickness: 0.3 mm, bump electrode size: 75 μm × 12 μm (for particle capture number evaluation) or 100 μm × 12 μm (for insulation evaluation), distance between bump electrodes: 24 μm, thickness of bump electrodes: 8 μm, bump electrode arrangement: the bump electrodes of the second row were positioned 12 μm offset in the longitudinal direction of the IC chip from the center of the bump electrodes of the first row, and the distance between the bump electrodes of the first row and the bump electrodes of the second row was 25 μm). As a second component, a wiring board was prepared by forming an ITO wiring pattern (pattern width: 19 μm, electrode spacing: 5 μm) on the surface of a glass substrate (Corning #1737, outer dimensions: 38 mm x 28 mm, thickness: 0.3 mm).

[0171] Next, the adhesive film for circuit connection was cut to a size of 2 x 20 mm and transferred from the PET film to the second component. Then, by applying a load of 80 MPa (calculated based on bump area) and heating and pressurizing at 130°C for 5 seconds, the first component was mounted on the second component via the adhesive film for circuit connection. This obtained a connection structure. Multiple connection structures were fabricated for each comparative example and each embodiment using the same procedure as described above.

[0172] (2) Evaluation of conductive particle trapping ability The number of conductive particles trapped between the bump electrodes and the circuit electrodes in the connection structures of Comparative Examples 1-4 and Examples 1-4 (number of trapped particles) was measured using an optical microscope. The conductive particle trapping performance was evaluated based on the number of trapped particles per bump electrode (number of trapped particles / number of bump electrodes) and its CV value. The results are shown in Table 5.

[0173] (3) Evaluation of insulating properties The insulation performance was evaluated based on the percentage of connection structures determined to have poor insulation resistance (insulation resistance failure rate) based on their insulation resistance value. The connection resistance value was measured by connecting the terminals of an insulation resistance measuring device to terminals provided at the ends of the connection structures, applying a voltage of 50V to the connection structures, and measuring the insulation resistance all at once. An insulation resistance value of 1.0E+09Ω or less, as indicated by the insulation resistance measuring device, was determined to be poor insulation resistance. In both Comparative Examples 1-4 and Examples 1-4, the above evaluation was performed with N (number of connection structures to be evaluated) = 10, the number of connection structures determined to have poor insulation resistance was counted, and the insulation resistance failure rate was calculated. The results are shown in Table 5.

[0174] [Table 5] [Explanation of symbols]

[0175] 1...connecting structure, 4...first member, 5...second member, 6...connecting part, 42...first electrode, 52...second electrode, 11...adhesive film for circuit connection, 13...conductive adhesive layer, 31...mother particle, 32...child particle, P...conductive particle.

Claims

1. Conductive particles for adhesive films used for circuit connections, It comprises conductive mother particles and daughter particles that cover the surface of the mother particles, The aforementioned subparticles contain a polymer that includes polar group-containing monomers as monomer units, The content of the polar group-containing monomer contained in the polymer as monomer units is 9.0 to 15.0 mol%, based on the total amount of monomer units contained in the polymer. The particle radius and particle diameter of the aforementioned subparticles, obtained by observation at a magnification of 30,000x using SEM, are respectively r Ｘ and d Ｘ The particle diameter d Ｘ The average particle diameter of the subparticles, which is the average value of d, is Ｙ Therefore, conductive particles whose degree of irregularity, as calculated by the following formula (1), is greater than 2.

0. Irregularity = D / r Ｙ ×100 (1) [In formula (1), r Ｙ represents the radius of a virtual sphere having a diameter equal to d Ｙ , D represents the average value of the absolute difference between the particle radius r Ｘ of the sub-particle and the radius r Ｙ of the virtual sphere.]

2. The conductive particle according to claim 1, wherein the coverage rate of the surface of the mother particle by the child particles is 30.0% or more.

3. The conductive particle according to claim 1 or 2, wherein the C.V. value of the coverage rate of the surface of the mother particle by the child particles is 20.0% or less.

4. The conductive particle according to any one of claims 1 to 3, wherein the average particle diameter of the subparticles, as determined by observation at a magnification of 30,000x using a SEM, is 200 to 400 nm.

5. The conductive particles according to any one of claims 1 to 4, wherein when a film is formed from the conductive particles, the contact angle of the surface of the film with respect to water is 85 to 115°.

6. The conductive particle according to any one of claims 1 to 5, wherein the polar group-containing monomer comprises at least one selected from the group consisting of (meth)acrylic acid and its salts, styrene sulfonic acid and its salts, (meth)acryloyl group-containing phosphate monoesters and their salts, (meth)acryloyl group-containing epoxy monomers, (meth)acryloyl group-containing carboxylic acid esters, and (meth)acryloyl group-containing alkoxysilanes and their hydrolysates.

7. The conductive particle according to any one of claims 1 to 6, wherein the polymer comprises a non-aromatic crosslinkable monomer and a non-crosslinkable monomer as monomer units.

8. The conductive particle according to claim 7, wherein the non-aromatic crosslinkable monomer is a polyfunctional (meth)acrylate monomer having a hydrocarbon chain which may have an ether linkage and a plurality of (meth)acryloyloxy groups bonded to the hydrocarbon chain.

9. The conductive particle according to claim 7 or 8, wherein the non-crosslinked monomer is a methacrylic acid ester.

10. The conductive particle according to any one of claims 1 to 9, wherein the polymer is an emulsion polymer.

11. A circuit connection adhesive film comprising a conductive adhesive layer containing an adhesive component and conductive particles according to any one of claims 1 to 10.

12. The device comprises a first member having a first electrode, a second member having a second electrode, and a connecting portion disposed between the first member and the second member, which electrically connects the first electrode and the second electrode to each other. A connection structure wherein the connection portion includes a cured product of the circuit connection adhesive film described in claim 11.

13. A method for manufacturing a connection structure, comprising the steps of: heat-pressing a first member having a first electrode and a second member having a second electrode with a circuit connection adhesive film according to claim 12 interposed between the first member and the second member; and electrically connecting the first electrode and the second electrode to each other.

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