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 an adhesive film for circuit connection which contains satisfactorily dispersed conductive particles and can improve insulation properties between adjacent electrodes in a connection structure and capturing properties of the conductive particles, and conductive particles which are used in the adhesive film for circuit connection.SOLUTION: Conductive particles P that are used in manufacture of an adhesive film for circuit connection having a mono-dispersion rate of 90.0% or more include a conductive mother particle 31, and child particles 32 coating the surface of the mother particle 31, wherein 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 less. 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 considered to improve the insulation between adjacent electrodes and the capture ability of conductive particles (connectivity between opposing electrodes) by applying an external force to conductive particles within an adhesive film to separate the conductive particles from each other. For example, Patent Document 1 proposes a method in which a conductive particle-attached film is prepared, having a laminate on which an adhesive layer is provided on a biaxially stretchable film, and conductive particles with an average particle size of 1 to 8 μm are densely packed on the laminate, and the conductive particle-attached film is biaxially stretched to separate the conductive particles from each other. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2011-091049 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the method described in Patent Document 1 above tends to result in insufficient dispersion of conductive particles in the adhesive film, making it difficult to accommodate further reductions in electrode spacing and electrode area. Therefore, there is a need to develop a method for manufacturing adhesive films for circuit connections that can better disperse conductive particles in the adhesive film and achieve higher conductive particle capture capabilities.

[0007] Therefore, the main objectives of the present invention are to provide a circuit connection adhesive film containing well-dispersed conductive particles and capable of improving insulation between adjacent electrodes in a connection structure and the capture ability of conductive particles, a method for manufacturing the same, conductive particles used in the circuit connection adhesive film, and a connection structure obtained using the circuit connection adhesive film and a method for manufacturing the same. [Means for solving the problem]

[0008] In several aspects, the present invention provides the following [1] to

[17] .

[0009] [1] Conductive particles used in the manufacture of an adhesive film for circuit connections having a monodisperse ratio of 90.0% or more, comprising conductive mother particles and daughter particles that cover the surface of the mother particles, wherein the particle radius and particle diameter of the daughter particles, as determined by observation at a magnification of 30,000 by 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, is d YWhen the irregularity degree of the sub-particles obtained by the following formula (1) is 2.0 or less, conductive particles. Irregularity degree = D / r Y ×100 (1) [In formula (1), r Y represents the radius of a virtual sphere equal to the diameter d Y , D is the particle radius r of the sub-particle X and the radius r of the virtual sphere Y and represents the average value of the absolute difference therebetween.]

[0010] [2] The conductive particles according to [1], wherein the coverage rate of the surface of the mother particle by the sub-particles is 40.0% or more.

[0011] [3] The conductive particles according to [1] or [2], wherein the C.V. value of the coverage rate of the surface of the mother particle by the sub-particles is 10.0% or less.

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

[0013] [5] The conductive particles according to any one of [1] to [4], wherein the ratio of the average particle diameter of the sub-particles obtained by observing at a magnification of 30,000 times by SEM to the particle diameter of the mother particle obtained by observing at a magnification of 25,000 times by SEM is 8.0 to 20.0.

[0014] [6] The conductive particles according to any one of [1] to [5], wherein when a film is formed from the conductive particles, the contact angle of the surface of the film with respect to water is 130° or more.

[0015] [7] The conductive particles according to any one of [1] to [6], wherein the sub-particles contain a copolymer containing an aromatic crosslinkable monomer and a non-crosslinkable monomer as monomer units.

[0016] [8] The conductive particles according to [7], wherein the aromatic crosslinkable monomer is divinylbenzene.

[0017] [9] The conductive particle according to [7] or [8], wherein the non-crosslinkable monomer is styrene.

[0018]

[10] The conductive particle according to any one of [7] to [9], wherein the content of polar group-containing monomers included as monomer units in the copolymer is 2.0 mol% or less based on the total amount of monomer units contained in the copolymer.

[0019]

[11] The conductive particle according to any one of [7] to

[10] , wherein the copolymer is an emulsion polymer.

[0020]

[12] Conductive particles according to any one of [1] to

[11] , used in a method for manufacturing an adhesive film for circuit connection, comprising the step of dispersing conductive particles by applying an external force to the conductive particles in a film containing an adhesive component and the conductive particles.

[0021]

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

[12] , wherein the monodisperse ratio of the conductive particles in the conductive adhesive layer is 90.0% or more.

[0022]

[14] A method for manufacturing an adhesive film for circuit connection, comprising the step of dispersing conductive particles in a film containing an adhesive component and conductive particles described in any of [1] to

[12] by applying an external force to the conductive particles.

[0023]

[15] The method for manufacturing an adhesive film for circuit connection according to

[14] , wherein in the step, a magnetic field is applied to the conductive particles to disperse them by applying a magnetic force.

[0024]

[16] 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] .

[0025]

[17] 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]

[0026] According to the present invention, it is possible to provide a circuit connection adhesive film containing well-dispersed conductive particles, which can improve the insulation between adjacent electrodes in a connection structure and the capture ability of the conductive particles, as well as a method for manufacturing the same. Furthermore, according to the present invention, it is possible to provide conductive particles used in the circuit connection adhesive film. Furthermore, according to the present invention, it is possible to provide a connection structure obtained using the circuit connection adhesive film and a method for manufacturing the same. [Brief explanation of the drawing]

[0027] [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] Figure 2 is a schematic diagram showing the manufacturing process of the adhesive film used for circuit connections. [Figure 4] This is a schematic diagram showing the magnetic field application process. [Figure 5] This is a schematic cross-sectional view showing the state of the adhesive film for circuit connection after the magnetic field application process and the drying process. [Figure 6] This is a schematic cross-sectional view showing the lamination process. [Figure 7] This is a micrograph showing the dispersion of conductive particles in a conventional manufacturing method. [Figure 8] This is a micrograph showing the dispersion of conductive particles in this manufacturing method. [Figure 9] This is a schematic cross-sectional view showing one embodiment of the connection structure according to the present invention. [Figure 10] Figure 9 is a schematic cross-sectional view showing the manufacturing process of the connecting structure. [Figure 11] This is a schematic cross-sectional view showing the subsequent process after Figure 10. [Modes for carrying out the invention]

[0028] 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, "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.

[0029] 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.

[0030] <Conductive particles> Figure 1 is a schematic cross-sectional view showing a conductive particle of one embodiment. The conductive particle P comprises a conductive mother particle 31 and a daughter particle 32 that covers the surface of the mother particle 31. Hereinin 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.

[0031] In the conductive particle P of this embodiment, the degree of deformation of the sub-particle 32 is 2.0 or less. Here, the degree of deformation 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.

[0032] Since the conductive particles P described above comprise sub-particles 32 having a degree of irregularity within the above range, they are suitably used in the manufacture of circuit connection adhesive films with a high monodispersity (for example, 90.0% or more). Circuit connection adhesive films with a high monodispersity are usually manufactured by a method that includes a step of dispersing the conductive particles in a film containing adhesive components and conductive particles by applying an external force (for example, magnetic force) to the conductive particles (external force application step). Since the conductive particles P exhibit good dispersibility in this external force application step, they are particularly suitably used in a method of manufacturing circuit connection adhesive films that includes such an external force application step. In this specification, a circuit connection adhesive film manufactured by the method of dispersing conductive particles using the above external force is referred to as an "external force-dispersed circuit connection adhesive film." Details of the method for manufacturing an external force-dispersed circuit connection adhesive film will be described later.

[0033] 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 generally used. The effect of the subatomic particles 32 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 ethyl acetate.

[0034] The reasons for obtaining the above effects are presumed to be as follows. First, if the sub-particles of the conductive particles have a property of easily swelling with the solvent (organic solvent) in the coating liquid, it is presumed that the sub-particles that swell in the coating liquid will aggregate by intertwining during drying, making them difficult to disperse even when the above external force is applied. Also, generally, organic solvents used to form films have a high affinity for the adhesive components (resins, etc.) that form the film. Therefore, if the sub-particles have a high affinity for the organic solvent, they tend to have a high affinity for the adhesive components as well. For this reason, it is presumed that when the conductive particles are dispersed by external force in the above external force application step, the flow of the sub-particles is suppressed by the adhesive components in the film. On the other hand, the small degree of irregularity of the sub-particles 32 means that the sub-particles 32 are inorganic particles, or organic particles with low polarity or organic-inorganic hybrid particles. These particles have a low affinity for organic solvents with an SP value of 8.5 to 10.0 and are not easily swollen in the coating liquid. Therefore, it is presumed that the conductive particles P exhibit good dispersibility because they are less prone to entanglement with other particles during drying, and less prone to flow inhibition by the adhesive components.

[0035] The degree of irregularity of the above-mentioned subparticles 32 may be 1.5 or less, 1.3 or less, or 1.2 or less, from the viewpoint of achieving higher dispersibility of the conductive particles P. The lower limit of the degree of irregularity is 0.1. 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.

[0036] When the above external force is a magnetic force (i.e., when the above external force application step is a magnetic field application step), the conductive particles P preferably contain at least one selected from the group consisting of iron, cobalt, and nickel, and more preferably contain nickel, from the viewpoint of dispersing by the magnetic field application step with higher efficiency. Generally, iron, cobalt, and nickel are ferromagnetic materials and are known to be magnetized by an external magnetic field. Among these, when nickel is used, both conductivity and dispersibility by magnetic field application can be achieved at a higher level. The magnetism of the conductive particles P can be confirmed by saturation magnetization. Saturation magnetization can be measured, for example, by a vibrating sample magnetometer (VSM). From the viewpoint of better dispersing the conductive particles P by an external magnetic field, it is preferable that the saturation magnetization obtained by VSM measurement is in the range of 5.0 emu / g to 50 emu / g.

[0037] 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.

[0038] (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.

[0039] 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.

[0040] 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.

[0041] 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.).

[0042] 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).

[0043] 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.

[0044] 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.

[0045] 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).

[0046] (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.

[0047] The subparticles 32 preferably contain a copolymer that includes an aromatic crosslinkable monomer and a non-crosslinkable monomer as monomer units. When the subparticles 32 contain such a copolymer, the degree of morphology of the subparticles 32 tends to fall within the range described above.

[0048] Aromatic crosslinkable monomers refer to monomers containing an aromatic hydrocarbon group and two or more crosslinkable groups. Examples of crosslinkable groups include vinyl groups and ethylenically unsaturated groups such as (meth)acryloyl groups.

[0049] Examples of aromatic crosslinkable monomers include divinylbenzene, divinylbiphenyl, divinylnaphthalene, and ethoxylated bisphenol A di(meth)acrylate. These monomers may be used individually or in combination of two or more. Divinylbenzene is preferred as the aromatic crosslinkable monomer from the viewpoints of insulating properties, dispersibility on film, ease of synthesis, cost, and reducing the degree of misformation of subparticles. In addition to aromatic crosslinkable monomers, conjugated dienes (non-aromatic crosslinkable monomers) such as butadiene and isoprene may also be used.

[0050] The content (degree of crosslinking) of aromatic crosslinkable monomers included as monomer units in the copolymer may be 2.0 to 10.0% by mass, or 2.0 to 5.0% by mass or 5.0 to 10.0% by mass, based on the total amount of monomer units contained in the copolymer, from the viewpoint of easily obtaining the above degree of heteromorphism. When the content of aromatic crosslinkable monomers is 2.0% by mass or more, the sub-particles tend to have better solvent resistance and tend to become relatively hard and resilient sub-particles. When the content of aromatic crosslinkable monomers is 10.0% by mass or less, the sub-particles tend to become more flexible particles, and the conductivity resistance of the resulting connected structure tends to be improved.

[0051] 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.

[0052] 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.

[0053] As non-crosslinkable monomers, monomers having aromatic hydrocarbon groups (aromatic non-crosslinkable monomers) are preferred from the viewpoints of insulating properties, dispersibility in films, ease of synthesis, and cost, with styrene being more preferred. Furthermore, styrene is preferably used from the viewpoint of further reducing the degree of misformation of subparticles.

[0054] 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 monomers 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 agent described later. From the viewpoint of making it easier to obtain the above degree of irregularity and increasing the contact angle, it is preferable to use dimethoxysilanes such as 3-methacryloxypropylmethyldimethoxysilane.

[0055] The content of non-crosslinkable monomers included as monomer units in the copolymer may be 90.0 to 98.0% by mass, based on the total amount of monomer units contained in the copolymer, from the viewpoint of easily obtaining the above degree of heteromorphism. When the content of non-crosslinkable monomers is 90.0% by mass or more, the sub-particles tend to become more flexible, and the conductivity resistance of the resulting connected structure tends to be improved. When the content of non-crosslinkable monomers is 98.0% by mass or less, the sub-particles tend to have better solvent resistance and tend to become relatively hard and resilient.

[0056] The copolymer contained in the child particles 32 may contain polar group-containing monomers as monomer units. For example, one or both of the aromatic crosslinkable monomer and the non-crosslinkable monomer may have polar groups. In particular, when some of the non-crosslinkable monomers contained in the copolymer are polar group-containing monomers, the child particles 32 can be synthesized stably, and it tends to be easier to control the particle size.

[0057] 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. Specific examples of polar group-containing monomers include (meth)acrylic acid and its salts, styrene sulfonic acid and its salts, (meth)acryloyl group-containing epoxy monomers, (meth)acryloyl group-containing carboxylic acid esters, and the aforementioned alkoxysilanes.

[0058] 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.

[0059] Examples of epoxy monomers containing a (meth)acryloyl group include glycidyl (meth)acrylate and 3,4-epoxycyclohexyl (meth)acrylate.

[0060] Examples of (meth)acryloyl group-containing carboxylic acid esters include (meth)acryloyloxyethyl succinic acid, (meth)acryloyloxyethyl phthalic acid, and (meth)acryloyloxypropyl phthalic acid.

[0061] 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 copolymer be as small as possible. From this viewpoint, the content of polar group-containing monomers included as monomer units in the copolymer may be 2.0 mol% or less, 1.5 mol% or less, or 1.0 mol% or less, based on the total amount of monomer units contained in the copolymer. From the viewpoint of securing bonding points with the mother particles and increasing the coverage rate of the mother particles by the child particles, the content of polar group-containing monomers included as monomer units in the copolymer may be 0.1 mol% or more, 0.3 mol% or more, or 1.0 mol% or more, based on the total amount of monomer units contained in the copolymer. From these viewpoints, the content of polar group-containing monomers included as monomer units in the copolymer may be 0.1 to 2.0 mol%, 0.3 to 2.0 mol%, 0.3 to 0.5 mol%, 0.5 to 1.0 mol%, 1.0 to 2.0 mol%, or 1.0 to 1.5 mol%, based on the total amount of monomer units contained in the copolymer.

[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, as determined by observation at 30,000x magnification using a scanning electron microscope (SEM), to the particle diameter of the mother particles 31, as determined by observation at 25,000x magnification using an SEM, is preferably 8.0 to 20.0. In this case, the conductive particles P become closer to a perfect sphere, and steric hindrance of the conductive particles during the external force application process becomes less likely. From a similar viewpoint, the above particle diameter ratio may be 8.0 or more, 10.0 or more, 20.0 or less, 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 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 mother particle 31. From this viewpoint, the average particle diameter may be 250 nm or more or 300 nm or more, or 350 nm or less or 280 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 40.0% 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 45.0% or more or 50.0% or more. The upper limit of the above coverage rate is, for example, 75.0%. That is, the above coverage rate may be 40.0 to 75.0%. 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 8000x. 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 10.0% 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 5.0% or less or 4.0% or less. The lower limit of the above CV value is, for example, 0.5%. That is, the above CV value may be between 0.5% and 10.0%. 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 into 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. The functional groups in the silicone oligomer may be in a state where they have reacted with the polymer electrolyte or functional groups introduced into 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 ethyl acetate to the average particle diameter in water (hereinafter referred to as the "swelling ratio") may be 1.20 or less. Here, the average particle diameter in water and the average particle diameter in ethyl acetate 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. When the swelling ratio of subparticles 32 is 1.20 or less, it can be said that subparticles 32 are particles that do not swell easily not only with ethyl acetate but also with organic solvents having an SP value close to that of ethyl acetate (e.g., acetone, methyl ethyl ketone, toluene, etc.). From the viewpoint of making it easier to obtain the above-mentioned effects, the swelling ratio may be 1.15 or less or 1.10 or less. From the viewpoint of manufacturing stability of subparticles and adsorption stability to mother particles, the swelling ratio may be 1.05 or more, and may be 1.10 or more or 1.15 or more. From these perspectives, the above swelling ratio may be 1.05-1.20, 1.05-1.15, 1.05-1.10, 1.10-1.15, or 1.15-1.20.

[0079] The conductive particles P comprising the parent particles 31 and child particles 32 described above preferably have a hydrophobic (water-repellent) 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 be 130° or more. The above contact angle may be 135° or more or 137° or more. The upper limit of the above contact angle is, for example, 140°. That is, the above contact angle may be 130° to 140°. It is preferable that the above contact angle is 20° 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 is constructed by laminating a release film 12, a conductive adhesive layer 13 consisting of an adhesive layer in which conductive particles P are dispersed, and an insulating adhesive layer 14 consisting of an adhesive layer in which conductive particles P are not dispersed, in this order. For the sake of explanation, the layer in which conductive particles P are dispersed will be referred to as the conductive adhesive layer, and the layer in which conductive particles P are not dispersed will be referred to as the insulating adhesive layer, but the adhesive components that make up both layers are insulating. Note that the release film 12 and the insulating adhesive layer 14 are not essential components. Furthermore, for the sake of explanation, a circuit connection adhesive film without a release film may also be referred to as the circuit connection adhesive film 11 below.

[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] Both the conductive adhesive layer 13 and the insulating adhesive layer 14 contain adhesive components. Here, adhesive components refer to the components contained 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), a curing agent, and a film-forming agent. 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 may be an epoxy resin monomer. Examples of epoxy resin monomers include bisphenol-type epoxy resins derived from epichlorohydrin with bisphenol A, bisphenol F, bisphenol AD, etc., epoxy novolac resins derived from epichlorohydrin with phenol novolac, cresol novolac, etc., and various epoxy compounds having two or more glycidyl groups in one molecule, such as glycidylamine, glycidyl ether, biphenyl, and alicyclic compounds.

[0104] The monomer may be a radical polymerizable monomer. Examples of radical polymerizable monomers include (meth)acrylic monomers such as (meth)acrylates, as well as maleimide compounds and styrene derivatives.

[0105] The curing agent can be any component that contributes to curing by polymerization of monomers. The curing agent can be a component incorporated into the molecular skeleton after curing, and may also be a so-called polymerization initiator.

[0106] When epoxy resin monomers are used, the curing agent may be an imidazole-based, hydrazide-based, boron trifluoride-amine complex, sulfonium salt, amineimide, polyamine salt, dicyandiamide, etc. From the viewpoint of extending the pot life, the curing agent may be coated with a polyurethane-based or polyester-based polymer compound and microencapsulated.

[0107] When epoxy monomers are used, the curing agent is appropriately selected depending on the desired bonding temperature, bonding time, storage stability, etc. From the viewpoint of high reactivity, it is preferable that the curing agent has a gel time with the epoxy resin composition of 10 seconds or less at a predetermined temperature, and from the viewpoint of storage stability, it is preferable that there is no change in the gel time with the epoxy resin composition after being stored in a constant temperature bath at 40°C for 10 days. For these reasons, the curing agent is preferably a sulfonium salt.

[0108] When using radical polymerizable monomers, curing agents that decompose upon heating to generate free radicals, such as peroxide compounds and azo compounds, may be used.

[0109] When using radical polymerizable monomers (particularly (meth)acrylic monomers), the curing agent is appropriately selected based on the desired bonding temperature, bonding time, storage stability, etc. From the viewpoint of high reactivity and storage stability, organic peroxides or azo compounds with a half-life of 10 hours at 40°C or higher and a half-life of 1 minute at 180°C or lower are preferred, and organic peroxides or azo compounds with a half-life of 10 hours at 60°C or higher and a half-life of 1 minute at 170°C or lower are more preferred. These curing agents can be used alone or in combination. The curing agent may also be used in combination with a decomposition accelerator, inhibitor, etc.

[0110] When the connection time is 10 seconds or less, from the viewpoint of improving the reaction rate, the amount of curing agent may be 0.1 to 40 parts by mass, or 1 to 35 parts by mass, per 100 parts by mass of the total of the monomer and the film-forming material described later.

[0111] The film-forming material is a polymer that facilitates the handling of the low-viscosity composition containing the above-mentioned curing agent and monomer. By using the film-forming material, the film is less likely to tear, crack, or become sticky, resulting in an easy-to-handle adhesive film 11 for circuit connections.

[0112] Thermoplastic resins are preferably used as film-forming materials. Examples of thermoplastic resins include phenoxy resin, polyvinyl formal resin, polystyrene resin, polyvinyl butyral resin, polyester resin, polyamide resin, xylene resin, polyurethane resin, polyacrylic resin, and polyester urethane resin. These polymers may contain siloxane bonds, fluorine substituents, etc. These resins can be used individually or in mixtures of two or more types. Among the above resins, phenoxy resin is preferred from the viewpoint of adhesive strength, compatibility, heat resistance, and mechanical strength.

[0113] The larger the molecular weight of the thermoplastic resin, the easier it is to obtain film formation properties, and the wider the range of melt viscosity that affects the fluidity of the adhesive film for circuit connection. The molecular weight of the thermoplastic resin may be 5,000 to 150,000 or 10,000 to 80,000 in weight-average molecular weight. Setting the weight-average molecular weight to 5,000 or higher makes it easier to obtain good film formation properties, while setting it to 150,000 or lower makes it easier to obtain good compatibility with other components. The weight-average molecular weight is the value measured using a calibration curve with standard polystyrene from gel permeation chromatography (GPC) according to the following conditions. (Measurement conditions) Equipment: GPC-8020 manufactured by Tosoh Corporation Detector: RI-8020 manufactured by Tosoh Corporation Column: Gelpack GLA160S + GLA150S manufactured by Showa Denko Materials Co., Ltd. Sample concentration: 120mg / 3mL Solvent: tetrahydrofuran Injection volume: 60μL Pressure: 2.94 × 10⁶ Pa (30 kgf / cm²) 2 ) Flow rate: 1.00mL / min

[0114] The content of the film-forming agent may be 5 to 80% by mass, or 15 to 70% by mass, based on the total amount of monomer, curing agent, and film-forming agent. When the content is 5% by mass or more, good film-forming properties tend to be obtained. When the content is 80% by mass or less, the curable composition tends to exhibit good fluidity.

[0115] Both the conductive adhesive layer 13 and the insulating adhesive layer 14 may further contain additives such as fillers, softeners, accelerators, antioxidants, colorants, flame retardants, thixotropic agents, and coupling agents.

[0116] If the adhesive layer contains a filler, further improvement in connection reliability can be expected. The maximum diameter of the filler is preferably less than the particle size of the conductive particles. The filler content is preferably 5 to 60 parts per 100 parts per volume of the adhesive layer. A sufficient improvement in reliability tends to be obtained when the filler content is 60 parts per volume or less. Furthermore, the effect of the filler is easily obtained when the filler content is 5 parts per volume or more.

[0117] The conductive particles P exist in a dispersed state within the conductive adhesive layer 13. The proportion of conductive particles P that exist in a state of separation from other conductive particles P (monodispersion ratio) is preferably 90.0% or more, and may be 93.0% or more, 95.0% or more, 98.0% or more, or 99.0% or more. The upper limit of the monodispersion ratio is 100%. The higher the monodispersion ratio, the easier it is to obtain a connection structure with excellent insulation reliability. Such a dispersed state is formed by the external force application process described later. The monodispersion ratio can be measured by the method described in the examples.

[0118] The content of conductive particles P may be 1 to 100 parts by volume, or 10 to 50 parts by volume, per 100 parts by volume of components other than conductive particles P in the conductive adhesive layer, from the viewpoint of achieving a higher level of both insulation between adjacent electrodes and capture of conductive particles.

[0119] Regarding the relationship between the average particle diameter of the conductive particles P and the thickness of the conductive adhesive layer 13, it is preferable that the thickness of the conductive adhesive layer 13 is 0.6 times or more and less than 1.0 times the average particle diameter of the conductive particles P. When the thickness of the conductive adhesive layer 13 is 0.6 times or more the average particle diameter of the conductive particles P, better connectivity is more likely to be obtained. When the thickness of the conductive adhesive layer 13 is less than 1.0 times the average particle diameter of the conductive particles P, better insulation is more likely to be obtained. From a similar viewpoint, the thickness of the conductive adhesive layer 13 may be 0.7 times or more and 0.9 times or less the average particle diameter of the conductive particles P.

[0120] When the above relationship is satisfied, a portion of the conductive particles P protrudes toward the insulating adhesive layer 14, and the boundary S between the insulating adhesive layer 14 and the conductive adhesive layer 13 is located in the spaced portion between adjacent conductive particles P, P. Furthermore, the conductive particles P are not exposed on the opposite side of the insulating adhesive layer 14 in the conductive adhesive layer 13 (i.e., the side toward the release film 12), and the opposite side is a flat surface. The shortest distance between the conductive particles P and the surface of the conductive adhesive layer 13 in the thickness direction of the conductive adhesive layer 13 may be greater than 0 μm and less than or equal to 1 μm.

[0121] The boundary S between the insulating adhesive layer 14 and the conductive adhesive layer 13 can be confirmed by cross-sectional observation of the circuit connection adhesive film 11. It is also possible to determine the boundary S between the insulating adhesive layer 14 and the conductive adhesive layer 13 by observing the differences in the observed images in processing observation devices such as FIB, SEM, and TEM, which are due to differences in the composition of the insulating adhesive layer 14 and the conductive adhesive layer 13.

[0122] If the insulating adhesive layer 14 and the conductive adhesive layer 13 are not compatible with each other, the boundary S can be identified as an interface. If the compositions of the insulating adhesive layer 14 and the conductive adhesive layer 13 are similar and the interface disappears during the lamination process described later, the boundary layer may be observed as a mixture of the insulating adhesive layer 14 and the conductive adhesive layer 13.

[0123] The thickness of the conductive adhesive layer 13 is, for example, 1.5 to 6.0 μm. The thickness of the insulating adhesive layer 14 can be set as appropriate. The sum of the thicknesses of the conductive adhesive layer 13 and the insulating adhesive layer 14 is, for example, 5 μm to 30 μm.

[0124] 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.

[0125] <Method for manufacturing adhesive film for circuit connections> The circuit connection adhesive film 11 shown in Figure 2 may be an external force-dispersing type circuit connection adhesive film. That is, the circuit connection adhesive film 11 may be manufactured by a method that includes a step (external force application step) in which an external force (e.g., magnetic force) is applied to the conductive particles P in a film containing adhesive components and conductive particles P, thereby dispersing the conductive particles P. The manufacturing method of the circuit connection adhesive film shown in Figure 2 will be described in detail below.

[0126] Figure 3 is a schematic diagram showing the manufacturing process of the circuit connection adhesive film shown in Figure 2. As shown in the figure, first, an adhesive paste W, which will be the material for forming the conductive adhesive layer 13, is applied to the release film 12 (coating process). In the example shown in the figure, a long piece of release film 12 is conveyed at a predetermined speed by a feed roller 21 and a winding roller 22. A coater 23 for applying the adhesive paste W, which will be the material for forming the conductive adhesive layer 13, is placed on the conveying path of the release film 12, and the adhesive paste W is applied to the release film 12 by the coater 23. The thickness of the film (coating) made of the adhesive paste W applied to the release film 12 by the coater 23 varies as needed depending on the proportion of solvent contained in the resin composition, but it is preferable that it is less than 1.6 times the average particle diameter of the conductive particles P.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] Next, a magnetic force is applied as an external force to the conductive particles P in the film (adhesive paste W) containing the adhesive component and conductive particles, thereby dispersing the conductive particles P (magnetic field application step). As shown in Figure 4, a pair of magnets 24 and 25 are arranged opposite each other vertically on the downstream side of the coater 23, sandwiching the release film 12. The magnet 24 positioned on the upper side is the N pole, and the magnet 25 positioned on the lower side is the S pole, so a magnetic field is formed in a direction approximately perpendicular to the direction from magnet 24 to magnet 25. Therefore, when the release film 12 is transported between magnets 24 and 25, the conductive particles P in the film (adhesive paste W) are magnetized, and a state is formed in which the conductive particles P, P are separated from each other in the in-plane direction of the film (adhesive paste W) due to the repulsive force (magnetic field application step).

[0131] Next, while the release film 12 passes between the magnets 24 and 25, the adhesive paste W is dried by hot air or the like (drying step). As a result, the viscosity of the adhesive paste W increases, maintaining the separated state of the conductive particles P during the magnetic field application step, and a conductive adhesive layer 13 is formed on the release film 12, as shown in Figure 5. Furthermore, the thickness of the film (adhesive paste W) decreases during the drying step, and as described above, by keeping the thickness of the film (adhesive paste W) to less than 1.6 times the average particle diameter of the conductive particles P, it is possible to set the thickness of the conductive adhesive layer 13 to between 0.6 times and less than 1.0 times the average particle diameter of the conductive particles P.

[0132] The drying temperature of the adhesive paste W is, for example, 20 to 80°C. The transport speed of the release film 12 is, for example, 30 to 160 mm / s. The thickness of the film (adhesive paste W) is, for example, 5 to 10 μm.

[0133] Next, after forming the conductive adhesive layer 13, a separately prepared insulating adhesive layer 14 is laminated onto the conductive adhesive layer 13, as shown in Figure 6 (lamination process). This yields the circuit connection adhesive film 11 shown in Figure 2. For laminating the insulating adhesive layer 14, for example, a hot roll laminator can be used. Furthermore, the lamination method is not limited to lamination; it may also be a method in which the adhesive paste that will be the material for the insulating adhesive layer 14 is applied onto the conductive adhesive layer 13 and dried.

[0134] Figure 7 is a micrograph showing the dispersion of conductive particles in a conventional manufacturing method, and Figure 8 is a micrograph showing the dispersion of conductive particles in the present manufacturing method. As shown in Figure 7, in the conventional manufacturing method, although some conductive particles are scattered in a spaced-out state, the majority of conductive particles are in contact with other conductive particles and are aggregated. In contrast, as shown in Figure 8, in the present manufacturing method, almost all conductive particles maintain a spaced-out state from other conductive particles.

[0135] In the method for manufacturing the adhesive film for circuit connections described above, magnetic force is used as the external force. However, the method is not limited to magnetic force. By using the conductive particles P of the above embodiment, an adhesive film for circuit connections in which conductive particles are well dispersed can also be obtained by dispersing conductive particles using centrifugal force or the like.

[0136] <Connection Structure> Figure 9 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 2 having a first electrode 6, a second member 3 having a second electrode 8, and a connecting portion 4 disposed between the first member 2 and the second member 3, which electrically connects the first electrode 6 and the second electrode 8 to each other. The first member 2 and the second member 3 are arranged so that the first electrode 6 and the second electrode 8 face each other.

[0137] The first component 2 is, for example, a circuit component, and may be a tape carrier package (TCP), a printed circuit board, a semiconductor silicon chip, etc. Multiple first electrodes 6 of the first component 2 are arranged on the mounting surface 5a side of the main body 5. The first electrodes 6 are, for example, bump electrodes. The first electrodes 6 are, for example, rectangular in shape when viewed from above. The thickness of the first electrodes 6 is, for example, 3 μm or more and less than 18 μm. The material used to form the first electrodes 6 is, for example, Au, and is more easily deformable than conductive particles P. An insulating layer may be formed on the mounting surface 5a where the first electrodes 6 are not formed.

[0138] The second component 3 is, for example, a circuit component, and may be a circuit board used in a liquid crystal display. The second component 3 may be, for example, a glass substrate or plastic substrate on which a circuit is formed using ITO, IZO, metal, etc., and may also be a flexible printed circuit board (FPC) or a ceramic wiring board. As shown in Figure 9, the second component 3 has a plurality of second electrodes 8 corresponding to the first electrode 6 on the mounting surface 7a side of the main body 7. The second electrodes 8 are, for example, circuit electrodes. The second electrodes 8 are, for example, rectangular in shape in a plan view. The thickness of the second electrodes 8 is, for example, about 100 nm. The surface of the second electrodes 8 is composed of one or more materials selected from the group consisting of, for example, gold, silver, copper, tin, ruthenium, rhodium, palladium, osmium, iridium, platinum, indium tin oxide (ITO), and indium zinc oxide (IZO). An insulating layer may also be formed on the mounting surface 7a in areas where the second electrodes 8 are not formed.

[0139] The connecting portion 4 is a portion formed by curing the circuit connection adhesive film 11, and includes the cured product of the circuit connection adhesive film 11. The connecting portion 4 may consist only of the cured product of the circuit connection adhesive film 11. The connecting portion 4 has a first region 9 formed by curing the conductive adhesive layer 13, and a second region 10 formed by curing the insulating adhesive layer 14. The first region 9 and the second region 10 spread in layers along the mounting surface 5a of the first member 2 and the mounting surface 7a of the second member 3. In this embodiment, the first region 9 is located on the second member 3 side, and the second region 10 is located on the first member 2 side. The boundary between the first region 9 and the second region 10 does not necessarily have to be clearly defined.

[0140] The conductive particles P are predominantly located on the second member 3 side, with some of them interposed between the first electrode 6 and the second electrode 8. Between the first electrode 6 and the second electrode 8, some of the child particles 32 are detached by compression, and the mother particles 31 are slightly flattened and in contact with the first electrode 6 and the second electrode 8. This achieves an electrical connection between the first electrode 6 and the second electrode 8. Furthermore, the conductive particles P are spaced apart between adjacent first electrodes 6,6 and between adjacent second electrodes 8,8, thus achieving electrical insulation between adjacent first electrodes 6,6 and adjacent second electrodes 8,8.

[0141] <Method for manufacturing a connecting structure> The manufacturing method for the connecting structure 1 includes the steps of heat-pressing a first member 2 and a second member 3 with a circuit connection adhesive film 11 interposed between the first member 2 and the second member 3, and electrically connecting the first electrode 6 and the second electrode 8 to each other. The manufacturing method for the connecting structure 1 will be described below with reference to Figures 10 and 11.

[0142] Figures 10 and 11 are schematic cross-sectional views showing the manufacturing process of the connection structure 1 shown in Figure 9. In manufacturing the connection structure 1, first, the release film 12 is peeled off the circuit connection adhesive film 11, and the circuit connection adhesive film 11 is laminated onto the second member 3 so that the conductive adhesive layer 13 side faces the mounting surface 7a. Next, as shown in Figure 11, the first member 2 is placed on the second member 3, to which the circuit connection adhesive film 11 has been laminated, so that the first electrode 6 and the second electrode 8 face each other. Then, while heating the circuit connection adhesive film 11, the first member 2 and the second member 3 are pressed in the thickness direction.

[0143] As a result, the adhesive component of the circuit connection adhesive film 11 flows, reducing the distance between the first electrode 6 and the second electrode 8, causing the conductive particles P to interlock, and the conductive adhesive layer 13 and the insulating adhesive layer 14 to harden. The hardening of the conductive adhesive layer 13 and the insulating adhesive layer 14 forms a connection portion 4 in which the first electrode 6 and the second electrode 8 are electrically connected, and adjacent first electrodes 6,6 and adjacent second electrodes 8,8 are electrically insulated from each other, resulting in the connection structure 1 shown in Figure 9. In the obtained connection structure 1, the connection portion 4 sufficiently prevents changes in the distance between the first electrode 6 and the second electrode 8 over time, and also ensures the long-term reliability of the electrical characteristics.

[0144] 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]

[0145] 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.

[0146] <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.

[0147] (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.

[0148] 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 (absolute difference) was calculated. The average of these absolute differences was taken as the average strain D of the particle, and the radius r of the virtual circle was calculated as the average strain D. Y Using the following formula, the degree of particle irregularity was calculated. Deformity = Mean distortion D / Radius of virtual circle r 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.

[0149] (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 ethyl acetate and treated for 5 minutes in an ultrasonic bath with an ultrasonic frequency of 40 kHz and an output of 120 W. The average particle size d3 of insulating particles 1-8 in ethyl acetate 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.

[0150] The particles to be measured (any of insulating microparticles 1 to 8) were added to a solvent (water or ethyl acetate) in a range of 0.1 to 1.0 mass% so that the pH of the sample solution was 7.3 to 7.8. The particles were then dispersed by vibrating in a 120W ultrasonic bath for 5.0 minutes. Next, the particle size distribution was measured at 25 to 27°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 diameter at 50% of the cumulative value (by volume) in the obtained particle size distribution was defined as the average particle diameter.

[0151] (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.

[0152] [Table 1]

[0153] [Table 2]

[0154] [Table 3]

[0155] 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

[0156] <Examples 1-4 and Comparative 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.

[0157] 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.

[0158] [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

[0159] [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.

[0160] 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 pure water 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.

[0161] 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 liquid and filtered using a 3 μm pore size membrane filter (Millipore). The filtered particles were placed in 200 g of pure water and stirred at room temperature for 5 minutes. The particles were then removed from this methanol and filtered using a 3 μm pore size membrane filter (Millipore), and washed twice on the membrane filter with 200 g of pure water. This removed polyethyleneimine that was not adsorbed on particle 1A, and particles coated with an amino group-containing polymer (particle 1B) were obtained.

[0162] Next, insulating microparticles 1 to 8 were treated with silicone oligomer 1 to prepare an ethyl acetate dispersion of microparticles (microparticles 1A to 8A) having glycidyl group-containing oligomers on their surface.

[0163] Next, after immersing particle 1B in ethyl acetate, conductive particles were obtained in which one of the insulating fine particles 1 to 8 was used as a subparticle. In this process, the amount of ethyl acetate dispersion added was sufficient to completely cover the surface of the mother particle with subparticles (including unadsorbed subparticles).

[0164] Next, the obtained conductive particles were treated with 315 g of a solution (solid content concentration: 1.9% by 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.

[0165] (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 8000x magnification 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. The results are shown in Table 4.

[0166] [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 parent particles were determined for conductive particles 1 to 8 using the following method. First, carbon tape was attached to the SEM sample stage, and conductive particles (conductive particles 1 to 8) were scattered on it. The scattered conductive particles were observed with an SEM to determine the conductive particle to be measured, and the particle diameter of the parent particle in that conductive particle was measured at a magnification of 25,000x. Next, in order to measure the particle diameter of the child particles, the SEM magnification was changed to 30,000x, and the particle diameter of the child particles in the conductive particle whose parent particle diameter had been measured was measured. For each conductive particle, the particle diameters of 5 child particles were measured, and the average of these was taken as the average particle diameter of the child particles in that conductive particle. In addition, the ratio of the average particle diameter of the child particles to the particle diameter of the parent particles was determined from the obtained measurement values. The above measurements were repeated for 25 conductive particles to determine the average particle diameter of the child particles and the average ratio of the average particle diameter of the child particles to the particle diameter of the parent particles (average of 25 values). These were then used 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 parent particles for conductive particles 1 to 8. The results are shown in Table 4.

[0167] [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 using an air blower (product name: Air Duster AHSze300, manufactured by Air Water Sol Co., Ltd.) with a spray time of 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.

[0168] Next, using the above 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 made 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 results are shown in Table 4. The above contact angle measurements were performed at room temperature (25°C).

[0169] [Table 4]

[0170] (Preparation of adhesive film for circuit connection) 45 g of 4,4'-(9-fluorenylidene)-diphenol (manufactured by Sigma-Aldrich Japan Co., Ltd.) and 50 g of 3,3',5,5'-tetramethylbiphenol diglycidyl ether (manufactured by Mitsubishi Chemical Corporation: YX-4000H) were dissolved in 1000 mL of N-methylpyrrolidone in a 3000 mL three-necked flask equipped with a Liebig condenser, a calcium chloride tube, and a Teflon stirring rod ("Teflon" is a registered trademark) connected to a stirring motor, to prepare the reaction solution. 21 g of potassium carbonate was added to this, and the mixture was stirred while heating to 110 °C with a mantle heater. After stirring for 3 hours, the reaction solution was added dropwise to a beaker containing 1000 mL of methanol, and the resulting precipitate was filtered by suction filtration. The filtered precipitate was further washed three times with 300 mL of methanol to obtain 75 g of phenoxy resin a.

[0171] Subsequently, the molecular weight of phenoxy resin a was measured using a high-performance liquid chromatograph GP8020 manufactured by Tosoh Corporation (column: Gerpak GLA150S and GLA160S manufactured by Hitachi Chemical Co., Ltd., solvent: tetrahydrofuran, flow rate: 1.0 mL / min). As a result, the number-average molecular weight (Mn) was 15769, the weight-average molecular weight (Mw) was 38045, and the Mw / Mn ratio was 2.413, all calculated on a polystyrene basis.

[0172] Next, 50 parts by mass of bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation: jER828) as the epoxy compound, 5 parts by mass of 4-hydroxyphenylmethylbenzylsulfonium hexafluoroantimonate as the curing agent, 50 parts by mass of the above-mentioned phenoxy resin a as the film-forming material, and 80 parts by mass of conductive particles were blended to obtain conductive adhesive compositions (adhesive pastes) 1 to 8. In this case, conductive particles 1 to 8 were used as the conductive particles, respectively. Ethyl acetate was used as the solvent.

[0173] Next, conductive adhesive layers 1 to 8 with a thickness of 2.7 μm were obtained on a PET resin film using the conductive adhesive compositions 1 to 8 described above. Specifically, first, the conductive adhesive composition was applied to a 50 μm thick PET resin film using a coater to form a coating film, and then the coating film was dried while a magnetic field was applied. The thickness of conductive adhesive layers 1 to 8 was adjusted by the amount of conductive adhesive composition applied.

[0174] Next, an insulating adhesive composition was obtained by blending 45 parts by mass of bisphenol F type epoxy resin (manufactured by Mitsubishi Chemical Corporation: jER807) as the epoxy compound, 5 parts by mass of 4-hydroxyphenylmethylbenzylsulfonium hexafluoroantimonate as the curing agent, and 55 parts by mass of phenoxy resin b with Mw (weight-average molecular weight) 50,000 and Tg (glass transition temperature) 70°C as the film-forming material.

[0175] Next, the insulating adhesive composition was applied to a 50 μm thick PET resin film using a coater to form a coating film, and then the coating film was dried with hot air at 70°C for 5 minutes to obtain an insulating adhesive layer with a thickness of 16 μm.

[0176] Next, each of the conductive adhesive layers 1 to 8 and the insulating adhesive layer were heated to 40°C and bonded together using a hot roll laminator to obtain the circuit connection adhesive films of Examples 1 to 4 and Comparative Examples 1 to 4.

[0177] (Rating 2) [Monodispersion of conductive particles] Using a metallurgical microscope, the circuit connection adhesive films of Examples 1-4 and Comparative Examples 1-4 were observed from the conductive adhesive layer side at 200x magnification, and the monodispersion ratio of conductive particles was determined by measuring the number of conductive particles in the conductive adhesive layer. The results are shown in Table 5. The monodispersion ratio is the ratio of conductive particles that exist in a state of separation from other conductive particles (monodispersion state), and was calculated using the following formula. Monodispersion rate (%) = (2500 μm 2 Number of monodisperse conductive particles in the substrate / 2500 μm 2 (Number of conductive particles inside) × 100

[0178] [Evaluation of conductive particle trapping ability and insulating properties] (1) Fabrication of connecting structures As the first component, an IC chip was prepared with a structure in which two rows of straight-aligned 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 and second rows was 25 μm). As the second component, a wiring board was prepared with an ITO wiring pattern (pattern width: 19 μm, space between electrodes: 5 μm) formed on the surface of a glass substrate (Corning #1737, outer dimensions: 38 mm × 28 mm, thickness: 0.3 mm).

[0179] Using the circuit connection adhesive films of Examples 1-4 and Comparative Examples 1-4, a first component (IC chip) and a second component (wiring board) were connected according to the procedure shown below, and multiple connection structures of Examples 1-4 and Comparative Examples 1-4 were obtained. A thermocompression bonding apparatus consisting of a stage (150 mm x 150 mm) made of a ceramic heater and a tool (3 mm x 20 mm) was used for the connection.

[0180] First, peel off the PET resin film from the conductive adhesive layer of the circuit connection adhesive film (outer dimensions: 2.5 mm x 25 mm), and then apply the conductive adhesive layer side to the side of the second component (wiring board) where the wiring pattern is formed, at 80°C and 0.98 MPa (10 kgf / cm²). 2 It was attached by heating and pressing for 2 seconds under the following conditions.

[0181] Next, the PET resin film on the insulating adhesive layer of the circuit connection adhesive film was peeled off, and the bump electrodes of the first component (IC chip) and the circuit electrodes of the second component (wiring board) were aligned. Then, under conditions of a measured maximum temperature of 170°C for the circuit connection adhesive film and an area-converted pressure of 70 MPa at the bump electrodes, the insulating adhesive layer was heated and pressurized for 5 seconds to adhere to the first component (IC chip), thereby obtaining the connection structure.

[0182] (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 Examples 1-4 and Comparative 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.

[0183] (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) from their insulation resistance values. 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 Examples 1-4 and Comparative 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.

[0184] [Table 5] [Explanation of Symbols]

[0185] 1...connecting structure, 2...first member, 3...second member, 4...connecting part, 6...first electrode (bump electrode), 8...second electrode (circuit electrode), 11...adhesive film for circuit connection, 13...conductive adhesive layer, 14...insulating adhesive layer, 31...mother particle, 32...child particle, P...conductive particle.

Claims

1. A conductive adhesive layer comprising an adhesive component and conductive particles, The conductive particle comprises a conductive mother particle and daughter particles that cover the surface of the mother particle. 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, the degree of misformation of the subparticles, as calculated by the following formula (1), is 2.0 or less. A circuit connection adhesive film wherein the monodispersity of the conductive particles in the conductive adhesive layer is 99.0% or more. 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 circuit connection adhesive film according to claim 1, wherein the coverage rate of the surface of the mother particle by the child particles is 40.0% or more.

3. The circuit connection adhesive film 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 10.0% or less.

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

5. The circuit connection adhesive film according to any one of claims 1 to 4, wherein the ratio of the average particle diameter of the child particles, as determined by observation at a magnification of 30,000 times by SEM, to the particle diameter of the mother particles, as determined by observation at a magnification of 25,000 times by SEM, is 8.0 to 20.

0.

6. The circuit connection adhesive film according to any one of claims 1 to 5, wherein when a film made of the conductive particles is formed, the contact angle of the surface of the film with respect to water is 130° or more.

7. The circuit connection adhesive film according to any one of claims 1 to 6, wherein the subparticles contain a copolymer comprising an aromatic crosslinkable monomer and a non-crosslinkable monomer as monomer units.

8. The circuit connection adhesive film according to claim 7, wherein the aromatic crosslinkable monomer is divinylbenzene.

9. The circuit connection adhesive film according to claim 7 or 8, wherein the non-crosslinked monomer is styrene.

10. The circuit connection adhesive film according to any one of claims 7 to 9, wherein the content of polar group-containing monomers contained as monomer units in the copolymer is 2.0 mol% or less based on the total amount of monomer units contained in the copolymer.

11. The circuit connection adhesive film according to any one of claims 7 to 10, wherein the copolymer is an emulsion polymer.

12. A method for manufacturing an adhesive film for circuit connection according to any one of claims 1 to 11, A method for manufacturing an adhesive film for circuit connection, comprising the step of dispersing the conductive particles in a film containing the adhesive component and the conductive particles by applying an external force to the conductive particles.

13. The method for manufacturing an adhesive film for circuit connection according to claim 12, wherein in the above step, a magnetic field is applied to disperse the conductive particles by applying a magnetic force to them.

14. 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 any one of claims 1 to 11.

15. A method for manufacturing a connection structure, comprising the steps of: thermocompressing a first member having a first electrode and a second member having a second electrode with a circuit connection adhesive film according to any one of claims 1 to 11 interposed between the first member and the second member; and electrically connecting the first electrode and the second electrode to each other.

Images