Conductive particles, conductive material, and connection structure

Abstract

Provided are conductive particles capable of exhibiting low dielectric properties.　These conductive particles comprise base material particles, and a conductive layer disposed on the surface of the base material particles. The base material particles are a polymer of polymerizable components. The polymerizable components include a polymerizable compound having one or more maleimide groups. Of the 100 wt% of the polymerizable components, the content of the polymerizable compound having one or more maleimide groups is 10 wt% or more and 80 wt% or less. The dielectric constant of the base material particles is 2.80 F / m or less, and the dielectric loss tangent of the base material particles is 0.01 or less.

Description

Conductive particles, conductive materials and connection structures

[0001] The present invention relates to a conductive particle including a base particle and a conductive layer disposed on the surface of the base particle. The present invention also relates to a conductive material and a connection structure using the conductive particle.

[0002] Anisotropic conductive materials, such as anisotropic conductive pastes and anisotropic conductive films, are widely known, and in such anisotropic conductive materials, conductive particles are dispersed in a binder resin.

[0003] The anisotropic conductive material is used to obtain various connection structures, such as a connection between a flexible printed circuit board and a glass substrate (FOG (Film on Glass)), a connection between a semiconductor chip and a flexible printed circuit board (COF (Chip on Film)), a connection between a semiconductor chip and a glass substrate (COG (Chip on Glass)), and a connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)).

[0004] Furthermore, as the conductive particles, conductive particles comprising a base particle and a conductive layer disposed on the surface of the base particle may be used.

[0005] As an example of a base particle used in the conductive particles, Patent Document 1 listed below describes a base particle having a 5% weight loss temperature of 350°C or higher and a 10% K value at 25°C of 100 N / mm ２ More than 2500N / mm ２ or less, and the 30% K value at 25°C is 100 N / mm ２ More than 1500N / mm ２ The following resin particles are disclosed.

[0006] WO2021 / 193911A1

[0007] When a connection structure is produced by electrically connecting electrodes using conductive particles obtained using conventional base particles as described in Patent Document 1, the connection resistance between the electrodes can be reduced to a certain extent. However, conductive particles, conductive materials, and connection structures using conventional base particles can have a high dielectric constant or dielectric loss tangent, resulting in large dielectric loss. As a result, there is a problem that the energy of electrical signals is attenuated in communication circuits.

[0008] In particular, in recent years, as communication speeds and capacities have increased, research is underway to utilize high frequency bands (e.g., 30 GHz to 300 GHz) for high-speed, large-capacity communications such as 5G and Beyond 5G (6G). Generally, the higher the frequency band, the greater the dielectric loss, making the above-mentioned problem more pronounced.

[0009] An object of the present invention is to provide a conductive particle, a conductive material, and a connection structure that can exhibit low dielectric properties.

[0010] The present specification discloses the following conductive particles, conductive materials, and connection structures.

[0011] Item 1. A conductive particle comprising a base particle and a conductive layer disposed on a surface of the base particle, wherein the base particle is a polymer of a polymerizable component, the polymerizable component includes a polymerizable compound having one or more maleimide groups, the content of the polymerizable compound having one or more maleimide groups is 10% by weight or more and 80% by weight or less relative to 100% by weight of the polymerizable component, the dielectric constant of the base particle is 2.80 F / m or less, and the dielectric loss tangent of the base particle is 0.01 or less.

[0012] Item 2. The conductive particles according to Item 1, wherein the polymerizable component includes a polymerizable compound having one or more ethylenically unsaturated groups other than a maleimide group.

[0013] Item 3. The conductive particles according to Item 1 or 2, wherein the polymerizable component contains divinylbenzene.

[0014] Item 4. The conductive particles according to Item 3, wherein the content of divinylbenzene is 20% by weight or more based on 100% by weight of the polymerizable component.

[0015] Item 5. The conductive particles according to any one of Items 1 to 4, wherein the polymerizable component does not contain a (meth)acrylic compound or contains the (meth)acrylic compound in an amount of 35% by weight or less.

[0016] Item 6. The conductive particles according to any one of Items 1 to 5, wherein the polymer of the polymerizable component has a residual amount of ethylenically unsaturated groups of 500 ppm or less.

[0017] Item 7. The conductive particle according to any one of Items 1 to 6, wherein the conductive layer contains nickel.

[0018] Item 8. The conductive particles according to any one of Items 1 to 7, wherein the conductive particles have a core substance, the conductive particles have protrusions formed by the core substance on their surfaces, and the core substance does not contain an inorganic oxide.

[0019] Item 9. The conductive particles according to any one of Items 1 to 8, wherein the particle diameter of the conductive particles is 1.0 μm or more and 50 μm or less.

[0020] Item 10. The conductive particles according to any one of Items 1 to 9, wherein the CV value of the particle diameter of the conductive particles is 10% or less.

[0021] Item 11. The conductive particle according to any one of Items 1 to 10, further comprising an insulating material disposed on the outer surface of the conductive layer.

[0022] Item 12. A conductive material comprising the conductive particles according to any one of items 1 to 11 and a binder resin.

[0023] Item 13. A connection structure comprising a first connection-target member having a first electrode on its surface, a second connection-target member having a second electrode on its surface, and a connection portion connecting the first connection-target member and the second connection-target member, wherein a material of the connection portion contains the conductive particles according to any one of Items 1 to 11, and the first electrode and the second electrode are electrically connected by the conductive particles.

[0024] The conductive particle according to the present invention comprises a base particle and a conductive layer disposed on the surface of the base particle. In the conductive particle according to the present invention, the base particle is a polymer of a polymerizable component, and the polymerizable component contains a polymerizable compound having one or more maleimide groups. In the conductive particle according to the present invention, the content of the polymerizable compound having one or more maleimide groups is 10% by weight or more and 80% by weight or less, based on 100% by weight of the polymerizable component. In the conductive particle according to the present invention, the base particle has a dielectric constant of 2.80 F / m or less. In the conductive particle according to the present invention, the base particle has a dielectric loss tangent of 0.01 or less. Because the conductive particle according to the present invention has the above-described configuration, it can exhibit low dielectric properties.

[0025] Fig. 1 is a cross-sectional view schematically showing a conductive particle according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view schematically showing a conductive particle according to a second embodiment of the present invention. Fig. 3 is a cross-sectional view schematically showing a connection structure using the conductive particle according to the first embodiment of the present invention.

[0026] The present invention will be described in detail below.

[0027] (Conductive Particles) The conductive particle according to the present invention comprises a base particle and a conductive layer disposed on the surface of the base particle. In the conductive particle according to the present invention, the base particle is a polymer of a polymerizable component, and the polymerizable component contains a polymerizable compound having one or more maleimide groups. In the conductive particle according to the present invention, the content of the polymerizable compound having one or more maleimide groups is 10% by weight or more and 80% by weight or less, based on 100% by weight of the polymerizable component. In the conductive particle according to the present invention, the base particle has a dielectric constant of 2.80 F / m or less. In the conductive particle according to the present invention, the base particle has a dielectric loss tangent of 0.01 or less.

[0028] The conductive particles according to the present invention have the above-described structure, and therefore can exhibit low dielectric properties. As a result, it is possible to suppress attenuation of the energy of an electrical signal in a communication circuit. Furthermore, because the conductive particles according to the present invention have the above-described structure, when used for electrical connection between electrodes, the electrodes and the conductive particles can be in sufficient contact with each other, and the connection resistance between the electrodes can be sufficiently low.

[0029] The compressive elastic modulus when the conductive particles are compressed by 10% at 25°C (10% K value of the conductive particles at 25°C) is preferably 500 N / mm ２ More preferably, 1000 N / mm ２ More preferably, 2000 N / mm ２ More preferably, 3000 N / mm ２ or more, preferably 20,000 N / mm ２ or less, more preferably 15,000 N / mm ２ or less, more preferably 10,000 N / mm ２ Below 6000 N / mm ２ When the 10% K value of the conductive particles at 25°C is equal to or greater than the lower limit, the hardness of the conductive particles (particularly the conductive layer) becomes appropriate, and the electrodes and the conductive particles can be firmly connected, thereby further reducing the connection resistance between the electrodes and improving the conduction reliability. When the 10% K value of the conductive particles at 25°C is equal to or less than the upper limit, the electrodes and the conductive particles can maintain sufficient contact without being broken when pressure is applied to them during mounting.

[0030] The 10% K value of the conductive particles at 25° C. can be measured as follows.

[0031] Using a micro-compression tester, the conductive particles are compressed with the end face of a smooth cylindrical indenter (diameter 50 μm, made of diamond) at 25°C under the condition of applying a maximum test load of 90 mN for 30 seconds. The load value (N) and compression displacement (mm) at this time are measured. From the obtained measured values, the compressive elastic modulus can be calculated using the following formula. As the micro-compression tester, for example, a Fischerscope H-100 manufactured by Fischer can be used.

[0032] 10% K value (N / mm ２ ) = (3 / 2 １／２ ) F.S. －３／２ ・R －１／２ F: Load value (N) when the conductive particle is compressed and deformed by 10%; S: Compression displacement (mm) when the conductive particle is compressed and deformed by 10%; R: Radius of the conductive particle (mm).

[0033] From the viewpoint of more effectively exerting the effects of the present invention, the compression recovery rate of the conductive particles at 25°C is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more, and is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less.

[0034] The compression recovery rate can be measured as follows. Conductive particles are scattered on a sample stage. For each scattered conductive particle, a load (reversed load value) is applied at 25°C toward the center of the conductive particle with the end face of a smooth cylindrical indenter (diameter 100 μm, made of diamond) using a micro-compression tester until the conductive particle is compressed and deformed by 40%. The load is then released to the origin load value (0.40 mN). The load-compression displacement during this period is measured, and the compression recovery rate can be calculated using the following formula. The loading rate is 0.33 mN / sec. As the micro-compression tester, for example, a Fischerscope H-100 manufactured by Fischer is used.

[0035] Compression recovery rate (%) = [L2 / L1] x 100 L1: Compression displacement from the load value for origin when applying a load to the reverse load value L2: Unloading displacement from the reverse load value when releasing the load to the load value for origin

[0036] The particle diameter of the conductive particles is preferably 0.5 μm or more, more preferably 1.0 μm or more, even more preferably 5.0 μm or more, and preferably 300 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and particularly preferably 30 μm or less. When the particle diameter of the conductive particles is above the above lower limit and below the above upper limit, when electrodes are connected using the conductive particles, the electrodes and the conductive particles can be in more effective contact, and agglomerated conductive particles are less likely to be formed when forming a conductive layer. In addition, the gap between the electrodes connected via the conductive particles is not too large, and the conductive layer is less likely to peel off from the surface of the base particle. In addition, when the particle diameter of the conductive particles is above the above lower limit and below the above upper limit, the conductive particles can be suitably used for conductive material applications.

[0037] The particle diameter of the conductive particles is preferably an average particle diameter, and more preferably a number average particle diameter. The particle diameter of the conductive particles can be determined, for example, by observing 50 random conductive particles with an electron microscope or optical microscope and calculating the average particle diameter of each conductive particle, or by performing laser diffraction particle size distribution measurement. In observation with an electron microscope or optical microscope, the particle diameter of each conductive particle is determined as the particle diameter in equivalent circle diameter. In observation with an electron microscope or optical microscope, the average particle diameter in equivalent circle diameter of 50 random conductive particles is approximately equal to the average particle diameter in equivalent sphere diameter. In laser diffraction particle size distribution measurement, the particle diameter of each conductive particle is determined as the particle diameter in equivalent sphere diameter. The particle diameter of the conductive particles is preferably calculated by laser diffraction particle size distribution measurement.

[0038] From the viewpoint of more effectively exerting the effects of the present invention, the coefficient of variation (CV value) of the particle diameter of the conductive particles is preferably 20% or less, more preferably 10% or less, and even more preferably 8% or less. The lower limit of the coefficient of variation (CV value) of the particle diameter of the conductive particles is not particularly limited. The coefficient of variation (CV value) of the particle diameter of the conductive particles may be 0% or more, or may be 1% or more. The range of the coefficient of variation (CV value) of the particle diameter of the conductive particles can be set by appropriately selecting the lower limit value and the upper limit value.

[0039] The coefficient of variation (CV value) of the particle diameter of the conductive particles can be measured as follows.

[0040] CV value (%) of particle diameter of conductive particles = (ρ / Dn) × 100, where ρ: standard deviation of particle diameter of conductive particles, and Dn: average particle diameter of conductive particles.

[0041] The shape of the conductive particles is not particularly limited. The shape of the conductive particles may be spherical, may be a shape other than spherical, or may be flat, etc. From the viewpoint of improving the dispersibility of the conductive particles in the binder resin, the shape of the conductive particles is preferably spherical.

[0042] The conductive particles are dispersed in a binder resin and are suitably used to obtain a conductive material.

[0043] The present invention will be specifically described below with reference to the drawings.

[0044] FIG. 1 is a cross-sectional view schematically showing a conductive particle according to a first embodiment of the present invention.

[0045] 1 has a base particle 1 and a conductive layer 2 disposed on the surface of the base particle 1. The conductive layer 2 coats the surface of the base particle 1. The conductive particle 11 is a coated particle in which the surface of the base particle 1 is coated with the conductive layer 2.

[0046] FIG. 2 is a cross-sectional view schematically showing a conductive particle according to a second embodiment of the present invention.

[0047] The conductive layer 22 is disposed on the surface of the base particle 1. The conductive particle 21 has a plurality of protrusions 21a on its surface. The conductive layer 22 has a plurality of protrusions 22a on its outer surface. In this way, the conductive particle may have protrusions on its surface, or may have protrusions on the outer surface of the conductive layer. In the conductive particle 21, a plurality of core materials 23 are disposed on the surface of the base particle 1. The plurality of core materials 23 are embedded in the conductive layer 22. The core materials 23 are disposed inside the protrusions 21a, 22a. The conductive layer 22 covers the plurality of core materials 23. The outer surface of the conductive layer 22 is raised by the plurality of core materials 23, forming the protrusions 21a, 22a.

[0048] The conductive particles 21 have an insulating material 24 disposed on the outer surface of the conductive layer 22. At least a portion of the outer surface of the conductive layer 22 is coated with the insulating material 24. The insulating material 24 is formed from a material having insulating properties and is an insulating particle. In this way, the conductive particles may have an insulating material disposed on the outer surface of the conductive layer.

[0049] Other details of the conductive particles will be described below. In this specification, "(meth)acrylate" refers to acrylate and methacrylate, "(meth)acrylic" refers to acrylic and methacrylic, and "(meth)acryloyl" refers to acryloyl and methacryloyl.

[0050] <Base Particle> In the conductive particle, the base particle is a polymer of a polymerizable component. The polymerizable component includes a polymerizable compound having one or more ethylenically unsaturated groups. Specifically, the polymerizable component includes a polymerizable compound having one or more maleimide groups. In the conductive particle, since the polymerizable component includes the polymerizable compound having one or more maleimide groups, low dielectric properties can be exhibited.

[0051] The polymerizable compound having one or more maleimide groups may have one maleimide group, two or more maleimide groups, 100 or less maleimide groups, or 10 or less maleimide groups. The maleimide group is an ethylenically unsaturated group. The polymerizable compound having one or more maleimide groups may be used alone or in combination of two or more.

[0052] Examples of the polymerizable compound having one maleimide group include N-alkyl group-substituted maleimides, N-aryl group-substituted maleimides, N-acyl group-substituted maleimides, etc. From the viewpoint of more effectively exhibiting the effects of the present invention, the polymerizable compound having one maleimide group preferably includes an N-alkylbismaleimide compound.

[0053] Examples of the polymerizable compound having two or more maleimide groups include a compound represented by the following formula (1), a compound represented by the following formula (2), a compound represented by the following formula (3), BMI-1700 (manufactured by DESIGNER MOLECULES), BMI-2500 (manufactured by DESIGNER MOLECULES), BMI-3000 (manufactured by DESIGNER MOLECULES), BMI-5000 (manufactured by DESIGNER MOLECULES), and BMI-6000 (manufactured by DESIGNER MOLECULES). MOLECULES), 1,2-bis(maleimido)ethane, 1,4-bis(maleimido)butane, 4,4'-bismaleimidodiphenylmethane, 4,4'-diphenylmethane bismaleimide, bis-(3-ethyl-4-maleimidophenyl)methane, 2,2'-bis-[4-(4-maleimidophenoxy)phenyl]propane, 4,4'-diphenylmethane bismaleimide, 1,4-phenylene bismaleimide, 1,3-phenylene bismaleimide, bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 1,6'-bismaleimido-(2,2,4-trimethyl)hexane ... Examples thereof include phenyl ether bismaleimide, 4,4'-diphenylsulfone bismaleimide, 1,3-bis(3-maleimidophenoxy)benzene, 1,3-bis(4-maleimidophenoxy)benzene, 1-maleimido-3-maleimidomethyl-3,5,5-trimethylcyclohexane, 1,1'-(cyclohexane-1,3-diylbis(methylene))bis(1H-pyrrole-2,5-dione), 1,1'-(4,4'-methylenebis(cyclohexane-4,1-diyl))bis(1H-pyrrole-2,5-dione), 1,1'-(3,3'-(piperazine-1,4-diyl)bis(propane-3,1-diyl))bis(1H-pyrrole-2,5-dione), and 2,2'-(ethylenedioxy)bis(ethylmaleimide).

[0054] From the viewpoint of more effectively exerting the effects of the present invention, the polymerizable component preferably contains a polymerizable compound having two or more maleimide groups, more preferably a bismaleimide compound, and from the viewpoint of more effectively exerting the effects of the present invention, the base particle preferably contains a polymer of a polymerizable compound having two or more maleimide groups, more preferably a bismaleimide compound.

[0055] From the viewpoint of more effectively exerting the effects of the present invention, the polymerizable compound having two or more maleimide groups preferably includes a compound represented by the following formula (1), a compound represented by the following formula (2), or a compound represented by the following formula (3):

[0056] An example of a commercially available product of the compound represented by the following formula (1) is BMI-689 (manufactured by Designer Molecules).

[0057] An example of a commercially available product of the compound represented by the following formula (2) is BMI-1400 (manufactured by Designer Molecules).

[0058] An example of a commercially available product of the compound represented by the following formula (3) is BMI-1500 (manufactured by Designer Molecules).

[0059]

[0060]

[0061] In the above formula (2), n is 1 or more and 10 or less.

[0062]

[0063] In the above formula (3), m is 1 or more and 2 or less.

[0064] From the viewpoint of effectively achieving the effects of the present invention, the polymerizable component includes a polymerizable compound that does not have a maleimide group (hereinafter, may be referred to as polymerizable compound (X)). From the viewpoint of effectively achieving the effects of the present invention, the polymerizable component includes a polymerizable compound different from polymerizable compounds that have one or more maleimide groups. The polymerizable compound (X) is a polymerizable compound other than polymerizable compounds that have one or more maleimide groups.

[0065] From the viewpoint of more effectively exerting the effects of the present invention, it is preferable that the polymerizable compound (X) has one or more ethylenically unsaturated groups. From the viewpoint of more effectively exerting the effects of the present invention, it is preferable that the polymerizable compound (X) is a polymerizable compound (monomer) having one or more ethylenically unsaturated groups. It is preferable that the polymerizable compound (X) has one or more ethylenically unsaturated groups other than a maleimide group. From the viewpoint of more effectively exerting the effects of the present invention, it is preferable that the polymerizable component contains a polymerizable compound having one or more ethylenically unsaturated groups other than a maleimide group. This polymerizable compound having one or more ethylenically unsaturated groups other than a maleimide group does not have a maleimide group.

[0066] Examples of the ethylenically unsaturated group include a vinyl group, an allyl group, a propenyl group, a cyclohexenyl group, and a 3-(methacryloyloxy)propyl group.

[0067] The polymerizable compound (monomer) having one or more ethylenically unsaturated groups includes a non-crosslinkable monomer and a crosslinkable monomer. The polymerizable compound (X) may be used alone or in combination of two or more.

[0068] Examples of the non-crosslinkable monomer include styrene-based monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, and polyoxyethylene (meth)acrylate. Examples of suitable monomers include oxygen atom-containing (meth)acrylates such as ethylene (meth)acrylate and glycidyl (meth)acrylate; nitrile-containing monomers such as (meth)acrylonitrile; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and propyl vinyl ether; acid vinyl esters such as vinyl acetate, vinyl butyrate, vinyl laurate and vinyl stearate; unsaturated hydrocarbons such as ethylene, propylene, isoprene and butadiene; and halogen-containing monomers such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, (perfluorohexyl)ethyl (meth)acrylate, vinyl chloride, vinyl fluoride and chlorostyrene.

[0069] Examples of the crosslinkable monomer include tetramethylolmethane tetra(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propane tri ... Examples of suitable monomers include polyfunctional (meth)acrylates such as propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate; and silane-containing monomers such as triallyl (iso)cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane.

[0070] From the viewpoint of more effectively exerting the effects of the present invention, the polymerizable component preferably contains divinylbenzene or styrene, and more preferably contains divinylbenzene. From the viewpoint of more effectively exerting the effects of the present invention, the polymerizable compound (X) preferably contains divinylbenzene or styrene, and more preferably contains divinylbenzene. The polymer of the polymerizable compound may contain a copolymer of styrene and divinylbenzene. The base particle may contain a copolymer of styrene and divinylbenzene.

[0071] The base particles can be obtained by polymerizing the polymerizable component by a known method, such as a suspension polymerization method in the presence of a radical polymerization initiator, or a method in which a polymerizable compound is swelled and polymerized together with a radical polymerization initiator using non-crosslinked seed particles.

[0072] The dielectric constant of the base particle is 2.80 F / m or less. From the viewpoint of more effectively exerting the effects of the present invention, the dielectric constant of the base particle is preferably 2.75 F / m or less, more preferably 2.70 F / m or less, even more preferably 2.65 F / m or less, even more preferably 2.60 F / m or less, even more preferably 2.55 F / m or less, even more preferably 2.50 F / m or less, particularly preferably 2.45 F / m or less, and most preferably 2.40 F / m or less. The lower limit of the dielectric constant of the base particle is not particularly limited. The dielectric constant of the base particle may be 1.50 F / m or more, 1.80 F / m or more, or 1.90 F / m or more. The range of the dielectric constant of the base particle can be set by appropriately selecting the lower limit and the upper limit.

[0073] The dielectric loss tangent of the base particle is 0.01 or less. From the viewpoint of more effectively exhibiting the effects of the present invention, the dielectric loss tangent of the base particle is preferably 0.009 or less, more preferably 0.008 or less, even more preferably 0.007 or less, even more preferably 0.006 or less, even more preferably 0.005 or less, even more preferably 0.004 or less, particularly preferably 0.003 or less, and most preferably 0.002 or less. When the dielectric loss tangent of the base particle is equal to or less than the above upper limit, low dielectric properties can be more effectively exhibited. The lower limit of the dielectric loss tangent of the base particle is not particularly limited. The dielectric loss tangent of the base particle may be 0.0001 or more, or may be 0.0005 or more. The range of the dielectric loss tangent of the base particle can be set by appropriately selecting the above lower limit and upper limit.

[0074] The dielectric constant and dielectric loss tangent of the base particles can be measured, for example, as follows: A quartz tube is filled with base particles and placed in a powder measurement resonator. The dielectric constant and dielectric loss tangent of the base particles at 1 GHz are measured using a dielectric constant measuring device (manufactured by AET).

[0075] Examples of methods for adjusting the dielectric constant of the base particle within the preferred range include a method of adjusting the content of the polymerizable compound having one or more maleimide groups, a method of using divinylbenzene as the polymerizable compound (X), a method of adjusting the content of divinylbenzene, a method of adjusting the content of a (meth)acrylic compound described below, a method of adjusting the type of crosslinking agent, polymerization temperature, polymerization time, etc., a method of adjusting the type and thickness of the metal of the conductive layer, a method of adjusting the type of core substance, a method of adjusting the porosity (specific surface area) of the base particle, and a method of washing away unreacted monomers.

[0076] Methods for adjusting the dielectric loss tangent of the base particle within the preferred range include adjusting the content of the polymerizable compound having one or more maleimide groups, using divinylbenzene as the polymerizable compound (X), adjusting the content of divinylbenzene, adjusting the content of a (meth)acrylic compound described below, adjusting the type of crosslinking agent, polymerization temperature, polymerization time, etc., adjusting the type and thickness of the metal of the conductive layer, adjusting the type of core substance, adjusting the porosity (specific surface area) of the base particle, and washing away unreacted monomers.

[0077] From the viewpoint of adjusting the dielectric constant and dielectric loss tangent of the base particle to fall within the above-mentioned preferred ranges and further effectively exerting the effects of the present invention, the polymerization temperature when polymerizing the polymerizable component is preferably 60°C or higher, more preferably 80°C or higher, and is preferably 150°C or lower, more preferably 110°C or lower.

[0078] From the viewpoint of adjusting the dielectric constant and dielectric loss tangent of the base particle to fall within the above-mentioned preferred ranges and further effectively exerting the effects of the present invention, the polymerization time for polymerizing the polymerizable component is preferably 60 minutes or more, more preferably 180 minutes or more, and is preferably 1,440 minutes or less, more preferably 1,080 minutes or less.

[0079] The compressive modulus of the base particle when compressed by 10% at 25°C (10% K value of the base particle at 25°C) is preferably 500 N / mm ２ More preferably, 1000 N / mm ２More preferably, 2000 N / mm ２ More preferably, 3000 N / mm ２ or more, preferably 20,000 N / mm ２ or less, more preferably 15,000 N / mm ２ or less, more preferably 10,000 N / mm ２ Below 6000 N / mm ２ When the 10% K value at 25°C of the base particle is equal to or greater than the lower limit, the hardness of the conductive particles (particularly the conductive layer) becomes appropriate, and the electrodes and the conductive particles can be firmly connected, thereby further reducing the connection resistance between the electrodes and further improving the conduction reliability. When the 10% K value at 25°C of the base particle is equal to or less than the upper limit, the electrodes and the conductive particles can maintain sufficient contact without being broken when pressure is applied to them during mounting.

[0080] The 10% K value at 25° C. of the above-mentioned base particles can be measured as follows.

[0081] Using a microcompression tester, the base particles are compressed with a cylindrical (diameter 50 μm, made of diamond) smooth indenter end face at 25°C under the condition of applying a maximum test load of 90 mN for 30 seconds. The load value (N) and compression displacement (mm) at this time are measured. From the obtained measured values, the compressive elastic modulus can be calculated using the following formula. As the microcompression tester, for example, a Fischerscope H-100 manufactured by Fischer can be used.

[0082] 10% K value (N / mm ２ ) = (3 / 2 １／２ ) F.S. －３／２ ・R －１／２ F: Load value (N) when the base particle is compressed and deformed by 10%; S: Compression displacement (mm) when the base particle is compressed and deformed by 10%; R: Radius of the base particle (mm)

[0083] The particle diameter of the base particle is preferably 0.4 μm or more, more preferably 0.9 μm or more, even more preferably 2.5 μm or more, particularly preferably 3.5 μm or more, most preferably 4.9 μm or more, and preferably 300 μm or less, more preferably 100 μm or less, even more preferably 49.9 μm or less, particularly preferably 24.9 μm or less. When the particle diameter of the base particle is above the above lower limit and below the above upper limit, when electrodes are connected using the obtained conductive particles, the electrodes and the conductive particles can be in more effective contact, and when a conductive layer is formed, agglomerated conductive particles are less likely to be formed. In addition, the gap between the electrodes connected via the conductive particles is not too large, and the conductive layer is less likely to peel off from the surface of the base particle. In addition, when the particle diameter of the base particle is above the above lower limit and below the above upper limit, the conductive particles can be suitably used for conductive material applications.

[0084] The particle diameter of the base particle is preferably an average particle diameter, and more preferably a number average particle diameter. The particle diameter of the base particle is determined, for example, using a particle size distribution measuring device. The particle diameter of the base particle is preferably determined by observing 50 random base particles with an electron microscope or an optical microscope and calculating the average value. When measuring the particle diameter of the base particle of the conductive particle, for example, it can be measured as follows.

[0085] The conductive particles were added to Kulzer's Technovit 4000 so that the content was 30 wt % and dispersed to prepare an embedding resin for testing containing base particles. An ion milling machine (Hitachi High-Technologies Corporation's IM4000) was used to cut out a cross section of the conductive particles so as to pass through the vicinity of the center of the base particles dispersed in the embedding resin for testing. Then, using a field emission scanning electron microscope (FE-SEM) with an image magnification set to 25,000x, 50 conductive particles were randomly selected and the base particles of each conductive particle were observed. The particle diameter of the base particles in each conductive particle was measured, and the arithmetic average was calculated to determine the particle diameter of the base particles.

[0086] From the viewpoint of more effectively exerting the effects of the present invention, the coefficient of variation (CV value) of the particle diameter of the base particles is preferably 20% or less, more preferably 10% or less, and even more preferably 8% or less. The lower limit of the coefficient of variation (CV value) of the particle diameter of the base particles is not particularly limited. The coefficient of variation (CV value) of the particle diameter of the base particles may be 0% or more, or may be 1% or more. The range of the coefficient of variation (CV value) of the particle diameter of the base particles can be set by appropriately selecting the lower limit value and the upper limit value.

[0087] The coefficient of variation (CV value) of the particle diameter of the base particles can be measured as follows.

[0088] CV value (%) of particle diameter of base particles = (ρ / Dn) × 100, where ρ: standard deviation of particle diameter of base particles, and Dn: average particle diameter of base particles.

[0089] The shape of the base particle is not particularly limited. The shape of the base particle may be spherical, may be a shape other than spherical, or may be flat. From the viewpoint of improving the dispersibility of the conductive particles in the binder resin, the shape of the base particle is preferably spherical.

[0090] The content of the polymer of the polymerizable component in 100% by weight of the base particle is preferably 80% by weight or more, more preferably 85% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. When the content of the polymer of the polymerizable component is equal to or greater than the lower limit, solvent resistance and chemical resistance can be improved. The upper limit of the content of the polymer of the polymerizable component is not particularly limited. The content of the polymer of the polymerizable component in 100% by weight of the base particle may be 100% by weight (total amount), 100% by weight or less, or even less than 100% by weight. The range of the content of the polymer of the polymerizable component in 100% by weight of the base particle can be set by appropriately selecting the lower limit and the upper limit.

[0091] The content of the polymerizable compound having one or more ethylenically unsaturated groups in 100% by weight of the polymerizable component is preferably 20% by weight or more, more preferably 30% by weight or more, even more preferably 40% by weight or more, even more preferably 80% by weight or more, even more preferably 85% by weight or more, particularly preferably 90% by weight or more, and most preferably 95% by weight or more. When the content of the polymerizable compound having one or more ethylenically unsaturated groups is equal to or greater than the lower limit, solvent resistance and chemical resistance can be improved. The upper limit of the content of the polymerizable compound having one or more ethylenically unsaturated groups is not particularly limited. The content of the polymerizable compound having one or more ethylenically unsaturated groups in 100% by weight of the polymerizable component may be 100% by weight (total amount), 100% by weight or less, or less than 100% by weight. The content of the polymerizable compound having one or more ethylenically unsaturated groups in 100% by weight of the polymerizable component may be 90% by weight or less, 85% by weight or less, 80% by weight or less, 75% by weight or less, or 70% by weight or less. The range of the content of the polymerizable compound having one or more ethylenically unsaturated groups in 100% by weight of the polymerizable component can be set by appropriately selecting the lower limit and the upper limit.

[0092] The content of the polymerizable compound having one or more maleimide groups in 100% by weight of the polymerizable component is 10% by weight or more and 80% by weight or less. The content of the polymerizable compound having one or more maleimide groups in 100% by weight of the polymerizable component is preferably 15% by weight or more, more preferably 20% by weight or more, even more preferably 25% by weight or more, particularly preferably 30% by weight or more, and preferably 70% by weight or less, more preferably 60% by weight or less. When the content of the polymerizable compound having one or more maleimide groups is equal to or greater than the lower limit, the effects of the present invention can be more effectively exhibited. When the content of the polymerizable compound having one or more maleimide groups is equal to or less than the upper limit, the dielectric constant and dielectric loss tangent of the base particle can be further reduced.

[0093] The content of the polymerizable compound having two or more maleimide groups in 100% by weight of the polymerizable component is preferably 15% by weight or more, more preferably 20% by weight or more, even more preferably 30% by weight or more, and is preferably 70% by weight or less, more preferably 60% by weight or less. When the content of the polymerizable compound having two or more maleimide groups is equal to or greater than the lower limit, the effects of the present invention can be more effectively exhibited. When the content of the polymerizable compound having two or more maleimide groups is equal to or less than the upper limit, the reaction rate of the polymerizable component is improved, and the amount of residual ethylenically unsaturated groups in the polymer can be reduced.

[0094] The content of the bismaleimide compound in 100% by weight of the polymerizable component is preferably 15% by weight or more, more preferably 20% by weight or more, even more preferably 30% by weight or more, and is preferably 70% by weight or less, more preferably 60% by weight or less. When the content of the bismaleimide compound is equal to or greater than the lower limit, the effects of the present invention can be more effectively exhibited. When the content of the bismaleimide compound is equal to or less than the upper limit, the reaction rate of the polymerizable component is improved, and the amount of residual ethylenically unsaturated groups in the polymer can be reduced.

[0095] The total content of the polymerizable compound having one or more maleimide groups and the polymerizable compound (X) in 100% by weight of the polymerizable component is preferably 80% by weight or more, more preferably 85% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. When the total content of the polymerizable compound having one or more maleimide groups and the polymerizable compound (X) is equal to or greater than the lower limit, solvent resistance and chemical resistance can be improved. There is no particular upper limit for the total content of the polymerizable compound having one or more maleimide groups and the polymerizable compound (X). The total content of the polymerizable compound having one or more maleimide groups and the polymerizable compound (X) in 100% by weight of the polymerizable component may be 100% by weight (total amount), 100% by weight or less, or less than 100% by weight. The total content of the polymerizable compound having one or more maleimide groups and the polymerizable compound (X) in 100% by weight of the polymerizable component may be 90% by weight or less, 85% by weight or less, 80% by weight or less, 75% by weight or less, or 70% by weight or less. The range of the total content of the polymerizable compound having one or more maleimide groups and the polymerizable compound (X) in 100% by weight of the polymerizable component can be set by appropriately selecting the lower limit and the upper limit.

[0096] In 100% by weight of the polymerizable component, the content of the polymerizable compound (X) is preferably 20% by weight or more, more preferably 30% by weight or more, even more preferably 40% by weight or more, and is preferably 90% by weight or less, more preferably 85% by weight or less, even more preferably 80% by weight or less, particularly preferably 75% by weight or less, and most preferably 70% by weight or less. When the content of the polymerizable compound (X) is above the lower limit, low thermal expansion can be exhibited. When the content of the polymerizable compound (X) is below the upper limit, the reactivity of the polymerizable component is improved, and the amount of residual ethylenically unsaturated groups in the polymer can be reduced.

[0097] When the polymerizable component (polymerizable compound (X)) contains a polymerizable compound having one or more ethylenically unsaturated groups other than a maleimide group, it is preferable that the following content is satisfied. The content of the polymerizable compound having one or more ethylenically unsaturated groups other than a maleimide group, based on 100% by weight of the polymerizable component, is preferably 20% by weight or more, more preferably 30% by weight or more, even more preferably 40% by weight or more, and is preferably 90% by weight or less, more preferably 85% by weight or less, even more preferably 80% by weight or less, particularly preferably 75% by weight or less, and most preferably 70% by weight or less. When the content of the polymerizable compound having one or more ethylenically unsaturated groups other than a maleimide group is above the lower limit, low thermal expansion properties can be exhibited. When the content of the polymerizable compound having one or more ethylenically unsaturated groups other than a maleimide group is below the upper limit, the reactivity of the polymerizable component is improved, and the amount of residual ethylenically unsaturated groups in the polymer can be reduced.

[0098] When the polymerizable component (polymerizable compound (X)) contains divinylbenzene, it is preferable that the following content is satisfied. The content of the divinylbenzene in 100% by weight of the polymerizable component is preferably 10% by weight or more, more preferably 20% by weight or more, even more preferably 30% by weight or more, and is preferably 85% by weight or less, more preferably 80% by weight or less, even more preferably 75% by weight or less. When the content of the divinylbenzene is equal to or greater than the lower limit, low thermal expansion properties can be exhibited. When the content of the divinylbenzene is equal to or less than the upper limit, the reaction rate of the polymerizable component is improved, and the amount of residual ethylenically unsaturated groups in the polymer can be reduced.

[0099] The polymerizable component (polymerizable compound (X)) may or may not contain a (meth)acrylic compound. From the viewpoint of more effectively exerting the effects of the present invention, it is preferable that the polymerizable component does not contain a (meth)acrylic compound or contains 35% by weight or less of a (meth)acrylic compound. From the viewpoint of more effectively exerting the effects of the present invention, the content of the (meth)acrylic compound in 100% by weight of the polymerizable component is preferably 35% by weight or less, more preferably 30% by weight or less, even more preferably 20% by weight or less, even more preferably 10% by weight or less, particularly preferably 5% by weight or less, and most preferably 0% by weight (not contained). From the viewpoint of more effectively exerting the effects of the present invention, the content of the (meth)acrylic compound in 100% by weight of the polymerizable component may be 1% by weight or more, or may be 5% by weight or more. The range of the content of the (meth)acrylic compound in 100% by weight of the polymerizable component can be set by appropriately selecting the lower limit and the upper limit.

[0100] From the viewpoint of further reducing the dielectric constant and dielectric loss tangent of the base particle, the residual amount of ethylenically unsaturated groups in the polymer of the polymerizable component is preferably 500 ppm or less, more preferably 400 ppm or less, even more preferably 300 ppm or less, and particularly preferably 200 ppm or less. The lower limit of the residual amount of ethylenically unsaturated groups in the polymer of the polymerizable component is not particularly limited. The residual amount of ethylenically unsaturated groups in the polymer of the polymerizable component may be 0 ppm or more, 10 ppm or more, 30 ppm or more, or 40 ppm or more. The range of the residual amount of ethylenically unsaturated groups in the polymer of the polymerizable component can be set by appropriately selecting the lower limit and the upper limit.

[0101] The amount of the remaining ethylenically unsaturated group in the polymer of the polymerizable component can be measured, for example, by the following method.

[0102] <Solid-state NMR measurement conditions> Nuclear magnetic resonance apparatus: JEOL "ECZ-400R" Temperature: Room temperature Observation nucleus: 13C Observation frequency: 100.5253 MHz Probe: 4 mm CPMAS probe Reference substance: Adamantane (external reference: 28.46 ppm) Pulse width: 2.40 μsec Acquisition time: 20.27 msec Pulse repetition time: 10 sec Magic angle spinning number: 10 kHz Number of accumulations: 4096 Measurement mode: Single pulse (DD / MAS) TOSS method Sample amount: Approximately 50 mg

[0103] Examples of a method for adjusting the amount of remaining ethylenically unsaturated groups in the polymer of the polymerizable component to fall within the preferred range include a method for adjusting the content of the polymerizable compound having one or more maleimide groups, a method for using divinylbenzene as the polymerizable compound (X), a method for adjusting the content of a (meth)acrylic compound, a method for adjusting the type of crosslinking agent, polymerization temperature, polymerization time, and the like, and a method for washing away unreacted monomers.

[0104] <Other Components> The base particles may contain other components as necessary. Examples of the other components include dispersants, preservatives, polymerization inhibitors, polymerization initiators, colorants, and surfactants. Only one type of the other components may be used, or two or more types may be used in combination.

[0105] The base particles may or may not contain a surfactant. Examples of the surfactant include anionic surfactants such as carboxylates, sulfonates, sulfates, and phosphates, cationic surfactants such as amine salts and ammonium salts, amphoteric surfactants, ester- or ether-type nonionic surfactants, and fluorine-based surfactants such as per(poly)fluoroalkyls.

[0106] From the viewpoint of reducing the environmental load, it is preferable that the base particles contain a surfactant in an amount of 1 wt% or less, or contain no surfactant, based on 100 wt% of the base particles. When the base particles contain the surfactant, the content of the surfactant is preferably 0.5 wt% or less, more preferably 0.1 wt% or less, and even more preferably 0.01 wt% or less, based on 100 wt% of the base particles. From the viewpoint of reducing the environmental load, it is more preferable that the base particles do not contain a surfactant.

[0107] <Core Material and Protrusions> The conductive particles may have protrusions on their surfaces. The conductive particles may have protrusions on the outer surface of the conductive layer. Preferably, there are multiple protrusions. An oxide film is often formed on the surface of the conductive layer and on the surface of the electrodes connected by the conductive particles. When conductive particles having protrusions are used, the oxide film is effectively removed by placing the conductive particles between the electrodes and pressing them together. This allows for more reliable contact between the electrodes and the conductive layer of the conductive particles, thereby reducing the connection resistance between the electrodes. Furthermore, when the conductive particles have an insulating material on their surfaces or when the conductive particles are dispersed in a binder resin and used as a conductive material, the protrusions of the conductive particles can effectively remove the insulating material or binder resin between the conductive particles and the electrodes. This further improves the reliability of conduction between the electrodes.

[0108] Methods for forming protrusions on the surface of the conductive particles include a method of adhering a core material to the surface of a base particle and then forming a conductive layer by electroless plating, and a method of forming a conductive layer on the surface of a base particle by electroless plating, then adhering a core material, and then further forming a conductive layer by electroless plating. Furthermore, the core material need not be used to form the protrusions. From the viewpoint of further improving the conduction reliability, it is preferable that the conductive particles have a core material and protrusions. From the viewpoint of further improving the conduction reliability, it is preferable that the conductive particles have protrusions formed by the core material on their surfaces.

[0109] Examples of methods for adhering a core substance to the surface of a base particle include a method of adding a core substance to a dispersion of the base particle and accumulating and adhering the core substance to the surface of the base particle by, for example, van der Waals forces, and a method of adding a core substance to a container containing the base particle and adhering the core substance to the surface of the base particle by mechanical action such as rotating the container. Among these, the method of adhering a core substance to the surface of the base particle in a dispersion is preferred because it is easy to control the amount of core substance to be adhered.

[0110] The conductive particle may have a first conductive layer on the surface of the base particle and a second conductive layer on the surface of the first conductive layer. In this case, a core material may be attached to the surface of the base particle, or may be attached to the surface of the first conductive layer. The core material is preferably coated with the second conductive layer, and more preferably coated with the first conductive layer and the second conductive layer. The conductive particle is preferably obtained by attaching a core material to the surface of the base particle, forming a first conductive layer on the surfaces of the base particle and the core material, and then forming a second conductive layer on the surface of the first conductive layer.

[0111] The core material may be made of conductive or non-conductive materials. Examples of the conductive material include conductive non-metals such as metals, metal oxides, and graphite, as well as conductive polymers. Examples of the conductive polymer include polyacetylene. Examples of the non-conductive material include inorganic oxides such as silica, alumina, and zirconia. From the viewpoint of more effectively exhibiting low dielectric properties and further reducing the connection resistance between electrodes, when the conductive particles have a core material and protrusions, the core material preferably does not contain an inorganic oxide and preferably does not contain a non-conductive material. From the viewpoint of more effectively exhibiting low dielectric properties and further reducing the connection resistance between electrodes, the core material is preferably made of a conductive material, more preferably a metal. From the viewpoint of more effectively exhibiting low dielectric properties and further reducing the connection resistance between electrodes, the core material is preferably a metal particle. When the core material is a metal, an oxide film (passivation) may be formed on the surface of the core material.

[0112] Examples of the metal include gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys composed of two or more metals such as tin-lead alloys, tin-copper alloys, tin-silver alloys, tin-lead-silver alloys, and tungsten carbide. Of these, nickel, copper, silver, and gold are preferred. The metal constituting the core material may be the same as or different from the metal constituting the conductive layer.

[0113] The shape of the core material is not particularly limited. The core material is preferably in the form of a mass. Examples of the core material include a particulate mass, an aggregate of multiple microparticles, and an amorphous mass.

[0114] The average height of the plurality of protrusions is preferably 0.001 μm or more, more preferably 0.05 μm or more, and is preferably 0.9 μm or less, more preferably 0.2 μm or less. When the average height of the protrusions is equal to or greater than the lower limit and equal to or less than the upper limit, the connection resistance between the electrodes can be effectively reduced.

[0115] <Conductive Layer> The conductive layer preferably contains a metal. The metal constituting the conductive layer is not particularly limited. Examples of the metal include gold, silver, copper, tin, platinum, palladium, zinc, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys thereof. Tin-doped indium oxide (ITO) may also be used as the metal. Only one of the metals may be used, or two or more may be used in combination. From the viewpoint of more effectively exerting the effects of the present invention, it is preferable that the metal constituting the conductive layer is a metal different from the metal contained in the coating film described below.

[0116] From the viewpoint of further improving the conduction reliability, the conductive layer preferably contains tin, nickel, palladium, copper or gold, more preferably contains tin or nickel, and even more preferably contains nickel.

[0117] From the viewpoint of further improving the conduction reliability, it is preferable that the conductive layer contains nickel as the main metal. From the viewpoint of further improving the conduction reliability, the content of nickel in 100% by weight of the conductive layer is preferably 15% by weight or more, more preferably 20% by weight or more, even more preferably 25% by weight or more, even more preferably 30% by weight or more, particularly preferably 40% by weight or more, and most preferably 50% by weight or more. From the viewpoint of further improving the conduction reliability, the content of nickel in 100% by weight of the conductive layer may be 100% by weight (total amount), may be 100% by weight or less, or may be less than 100% by weight. The range of the nickel content in 100% by weight of the conductive layer can be set by appropriately selecting the lower limit and the upper limit.

[0118] From the viewpoint of further improving the conduction reliability, the conductive layer preferably has a conductive layer containing nickel. From the viewpoint of further improving the conduction reliability, the nickel content in 100 wt% of the nickel-containing conductive layer is preferably 15 wt% or more, more preferably 20 wt% or more, even more preferably 25 wt% or more, even more preferably 30 wt% or more, particularly preferably 40 wt% or more, and most preferably 50 wt% or more. From the viewpoint of further improving the conduction reliability, the nickel content in 100 wt% of the nickel-containing conductive layer may be 100 wt% (total amount), 100 wt% or less, or less than 100 wt%. The range of the nickel content in 100 wt% of the nickel-containing conductive layer can be set by appropriately selecting the lower limit and the upper limit.

[0119] The conductive layer may be formed of a single layer. The conductive layer may be formed of multiple layers. That is, the conductive layer may have a laminated structure of two or more layers. When the conductive layer is formed of multiple layers, the metal constituting the outermost layer is preferably tin, nickel, palladium, copper, or gold, more preferably tin, nickel, palladium, or copper, even more preferably tin or nickel, and particularly preferably nickel. When the metal constituting the outermost layer is one of these preferred metals, the electrical connection between electrodes can be further improved, and the electrical connection reliability can be improved when used for a long period of time under high temperature and high humidity. Furthermore, when the metal constituting the outermost layer is gold, corrosion resistance is further improved.

[0120] From the viewpoint of improving the conduction reliability when used under high temperature and high humidity conditions for a long period of time, it is preferable that the outer surface portion of the conductive layer contains palladium or gold. From the viewpoint of improving the conduction reliability when used under high temperature and high humidity conditions for a long period of time, when the conductive layer has a laminated structure of two or more layers, it is preferable that the outermost layer contains palladium or gold, and when the conductive layer has a laminated structure of one layer, it is preferable that one conductive layer contains palladium or gold.

[0121] From the viewpoint of further improving the conduction reliability, the conductive layer preferably has a conductive layer containing palladium or gold. From the viewpoint of further improving the conduction reliability, the total content of palladium and gold in 100% by weight of the conductive layer containing palladium or gold is preferably 15% by weight or more, more preferably 20% by weight or more, even more preferably 25% by weight or more, even more preferably 30% by weight or more, particularly preferably 40% by weight or more, and most preferably 50% by weight or more. The total content of palladium and gold in 100% by weight of the conductive layer containing palladium or gold may be 100% by weight (total amount), 100% by weight or less, or less than 100% by weight. The range of the total content of palladium and gold in 100% by weight of the conductive layer containing palladium or gold can be set by appropriately selecting the above lower limit and upper limit.

[0122] From the viewpoint of further improving the reliability of conduction when the electrodes are electrically connected, it is preferable that the outer surface portion of the conductive layer contains nickel. From the viewpoint of further improving the reliability of conduction when the electrodes are electrically connected, when the conductive layer has a laminated structure of two or more layers, it is preferable that the outermost layer contains nickel, and when the conductive layer has a laminated structure of one layer, it is preferable that one conductive layer contains nickel.

[0123] The area of ​​the portion covered by the conductive layer (coverage by the conductive layer) of the total surface area of ​​the base particle (100%) is preferably 80% or more, more preferably 90% or more. The upper limit of the coverage by the conductive layer is not particularly limited. The coverage by the conductive layer may be 100%, less than 100%, or 99% or less. When the coverage by the conductive layer is equal to or greater than the lower limit and equal to or less than the upper limit, the electrical connection reliability can be further improved when electrodes are electrically connected. The range of the coverage by the conductive layer can be set by appropriately selecting the lower limit and the upper limit.

[0124] The thickness of the conductive layer is preferably 0.005 μm or more, more preferably 0.01 μm or more, and preferably 1 μm or less, more preferably 0.5 μm or less, and even more preferably 0.3 μm or less. When the thickness of the conductive layer is equal to or greater than the above lower limit and equal to or less than the above upper limit, the electrical connection reliability can be more effectively improved when electrodes are electrically connected. The thickness of the conductive layer is the thickness of the entire conductive layer. That is, when the conductive layer has a single-layer structure, the thickness of the conductive layer is the thickness of a single conductive layer. When the conductive layer has a laminated structure of two or more layers, the thickness is the thickness of the entire multi-layer conductive layer.

[0125] When the conductive layer is formed of a plurality of layers, the thickness of the outermost conductive layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, and preferably 0.5 μm or less, more preferably 0.3 μm or less. When the thickness of the outermost conductive layer is equal to or greater than the above lower limit and equal to or less than the above upper limit, the outermost conductive layer becomes uniform and has sufficiently high corrosion resistance, and when electrodes are electrically connected, the electrical connection reliability can be further improved.

[0126] When the conductive layer is formed of a plurality of layers, the thickness of the innermost conductive layer is preferably 0.005 μm or more, more preferably 0.01 μm or more, and is preferably 0.5 μm or less, more preferably 0.3 μm or less. When the thickness of the innermost conductive layer is equal to or greater than the lower limit and equal to or less than the upper limit, corrosion resistance is sufficiently high and connection resistance between electrodes can be sufficiently low.

[0127] The thickness of the conductive layer can be measured by observing the cross section of the conductive particle using, for example, a transmission electron microscope (TEM).

[0128] The method for forming the conductive layer on the surface of the base particle is not particularly limited. Examples of methods for forming the conductive layer include electroless plating, electroplating, physical collision, mechanochemical reaction, physical vapor deposition or physical adsorption, and coating the surface of the base particle with a metal powder or a paste containing a metal powder and a binder. The method for forming the conductive layer is preferably electroless plating, electroplating, or physical collision. Examples of physical vapor deposition methods include vacuum deposition, ion plating, and ion sputtering. Furthermore, the physical collision method uses, for example, a sheeter composer (manufactured by Tokuju Manufacturing Co., Ltd.).

[0129] <Insulating Material> The conductive particles may have an insulating material disposed on the outer surface of the conductive layer. In this case, using the conductive particles to connect electrodes can prevent short circuits between adjacent electrodes. Specifically, when multiple conductive particles come into contact with each other, an insulating material is present between the multiple electrodes, preventing short circuits between laterally adjacent electrodes rather than between upper and lower electrodes. When connecting the electrodes, applying pressure to the conductive particles with two electrodes can easily remove the insulating material between the conductive layer of the conductive particles and the electrode. When the conductive particles have protrusions on the surface of the conductive layer, the insulating material between the conductive layer of the conductive particles and the electrode can be even more easily removed. The insulating material is preferably an insulating resin layer or insulating particles, more preferably insulating particles. The insulating particles are preferably insulating resin particles.

[0130] Examples of the insulating material include polyolefins, (meth)acrylate polymers, (meth)acrylate copolymers, block polymers, thermoplastic resins, crosslinked thermoplastic resins, thermosetting resins, and water-soluble resins.

[0131] (Conductive Material) The conductive material according to the present invention includes the conductive particles described above and a binder resin. The conductive particles are preferably dispersed in the binder resin when used. The conductive particles are preferably dispersed in the binder resin when used as a conductive material. The conductive material is preferably an anisotropic conductive material. The conductive material is preferably used for electrical connection between electrodes. The conductive material is preferably a conductive material for circuit connection. Since the conductive material uses the conductive particles described above, particle aggregation in the binder resin can be suppressed. Furthermore, when electrodes are electrically connected, the connection resistance between the electrodes can be reduced, effectively improving conduction reliability.

[0132] The binder resin is not particularly limited. A known insulating resin is used as the binder resin. The binder resin preferably contains a thermoplastic component (thermoplastic compound) or a curable component, and more preferably contains a curable component. Examples of the curable component include a photocurable component and a thermosetting component. The photocurable component preferably contains a photocurable compound and a photopolymerization initiator. The thermosetting component preferably contains a thermosetting compound and a thermosetting agent.

[0133] Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, elastomers, etc. The binder resins may be used alone or in combination of two or more.

[0134] Examples of the vinyl resin include vinyl acetate resin, acrylic resin, and styrene resin. Examples of the thermoplastic resin include polyolefin resin, ethylene-vinyl acetate copolymer, and polyamide resin. Examples of the curable resin include epoxy resin, urethane resin, polyimide resin, and unsaturated polyester resin. The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin, or a moisture curable resin. The curable resin may be used in combination with a curing agent. Examples of the thermoplastic block copolymer include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, a hydrogenated product of styrene-butadiene-styrene block copolymer, and a hydrogenated product of styrene-isoprene-styrene block copolymer. Examples of the elastomer include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.

[0135] In addition to the conductive particles and the binder resin, the conductive material may contain various additives such as fillers, extenders, softeners, plasticizers, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents, and flame retardants.

[0136] The method for dispersing the conductive particles in the binder resin can be a conventionally known dispersion method and is not particularly limited. Examples of the method for dispersing the conductive particles in the binder resin include the following methods: A method in which the conductive particles are added to the binder resin and then kneaded and dispersed using a planetary mixer or the like; A method in which the conductive particles are uniformly dispersed in water or an organic dispersion medium using a homogenizer or the like, then added to the binder resin and then kneaded and dispersed using a planetary mixer or the like; A method in which the binder resin is diluted with water or an organic dispersion medium or the like, then the conductive particles are added, and then kneaded and dispersed using a planetary mixer or the like.

[0137] The viscosity (η25) of the conductive material at 25°C is preferably 30 Pa·s or more, more preferably 50 Pa·s or more, and preferably 400 Pa·s or less, more preferably 300 Pa·s or less. When the viscosity (η25) is equal to or greater than the lower limit and equal to or less than the upper limit, the insulation reliability between laterally adjacent electrodes can be more effectively improved, and the conduction reliability between upper and lower electrodes can be more effectively improved. The viscosity (η25) can be appropriately adjusted by changing the types and amounts of the components.

[0138] The viscosity (η25) can be measured, for example, using an E-type viscometer ("TVE22L" manufactured by Toki Sangyo Co., Ltd.) under conditions of 25° C. and 5 rpm.

[0139] The conductive material can be used as a conductive paste, a conductive film, or the like. When the conductive material is a conductive film, a film not including the conductive particle bodies may be laminated on a conductive film including the conductive particle bodies. The conductive paste is preferably an anisotropic conductive paste. The conductive film is preferably an anisotropic conductive film.

[0140] The content of the binder resin in 100% by weight of the conductive material is preferably 10% by weight or more, more preferably 30% by weight or more, even more preferably 50% by weight or more, particularly preferably 70% by weight or more, and is preferably 99.99% by weight or less, more preferably 99.9% by weight or less. When the content of the binder resin is equal to or more than the lower limit and equal to or less than the upper limit, the conductive particles are efficiently arranged between the electrodes, and the connection reliability of the connection target members connected by the conductive material can be further improved.

[0141] The content of the conductive particles in 100% by weight of the conductive material is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and is preferably 80% by weight or less, more preferably 60% by weight or less, even more preferably 40% by weight or less, particularly preferably 20% by weight or less, and most preferably 10% by weight or less. When the content of the conductive particles is equal to or more than the above lower limit and equal to or less than the above upper limit, the electrical conductivity reliability and the insulation reliability between the electrodes can be further improved.

[0142] (Connection structure) A connection structure according to the present invention comprises a first connection-target member having a first electrode on its surface, a second connection-target member having a second electrode on its surface, and a connection portion connecting the first connection-target member and the second connection-target member. In the connection structure according to the present invention, the material of the connection portion contains the conductive particles described above. In the connection structure according to the present invention, the first electrode and the second electrode are electrically connected by the conductive particles.

[0143] The connection structure can be obtained through a step of disposing the conductive particles between the first connection target member and the second connection target member, and a step of electrically connecting the first and second connection target members by thermocompression bonding. Alternatively, the conductive material may be disposed instead of the conductive particles.

[0144] FIG. 3 is a cross-sectional view that schematically shows a connection structure using conductive particles according to the first embodiment of the present invention.

[0145] The connection structure 51 shown in Fig. 3 includes a first connection target member 52, a second connection target member 53, and a connection portion 54 connecting the first connection target member 52 and the second connection target member 53. The connection portion 54 is formed of a conductive material containing conductive particles 11 and a binder resin. In Fig. 3, the conductive particles 11 are shown schematically for convenience of illustration. Instead of the conductive particles 11, other conductive particles such as conductive particles 21 may be used.

[0146] The first connection target member 52 has a plurality of first electrodes 52a on its surface (upper surface). The second connection target member 53 has a plurality of second electrodes 53a on its surface (lower surface). The first electrodes 52a and the second electrodes 53a are electrically connected by the conductive particles 11. Therefore, the first and second connection target members 52 and 53 are electrically connected by the conductive particles 11.

[0147] The method for manufacturing the connection structure is not particularly limited. One example of a method for manufacturing a connection structure is to place the conductive material between a first connection target member and a second connection target member, obtain a laminate, and then heat and pressurize the laminate. The pressure of the thermocompression bonding is preferably 40 MPa or more, more preferably 60 MPa or more, and preferably 90 MPa or less, more preferably 70 MPa or less. The temperature (heating temperature) of the thermocompression bonding is preferably 80°C or more, more preferably 100°C or more, and preferably 140°C or less, more preferably 120°C or less. When the pressure and temperature of the thermocompression bonding are above the lower limit and below the upper limit, the conductive particles arranged between the electrodes are effectively compressed, and the adhesion between the electrodes can be improved.

[0148] The first and second connection target members are not particularly limited. Specific examples of the first and second connection target members include electronic components such as semiconductor chips, semiconductor packages, LED chips, LED packages, capacitors, and diodes, as well as electronic components such as resin films, printed circuit boards, flexible printed circuit boards, flexible flat cables, rigid-flexible boards, glass epoxy boards, and glass boards. The first and second connection target members are preferably electronic components.

[0149] Examples of the electrodes provided on the connection target members include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, SUS electrodes, and tungsten electrodes. When the connection target members are flexible printed circuit boards, the electrodes are preferably gold electrodes, nickel electrodes, tin electrodes, silver electrodes, or copper electrodes. When the connection target members are glass substrates, the electrodes are preferably aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, or tungsten electrodes. When the electrodes are aluminum electrodes, they may be formed solely from aluminum, or may be electrodes in which an aluminum layer is laminated on the surface of a metal oxide layer. Examples of materials for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal element include Sn, Al, and Ga.

[0150] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0151] The following materials were prepared:

[0152] (Polymerizable component) N-alkylbismaleimide compound ("BMI-689" manufactured by DESIGNER MOLECULES, maleimide groups: 2) Styrene ("Styrene Monomer" manufactured by NS Styrene Monomer) Divinylbenzene ("DVB960" manufactured by NS Styrene Monomer) Ethylene glycol dimethacrylate ("Acryester ED" manufactured by Mitsubishi Chemical Corporation)

[0153] (Polymerization initiator) Benzoyl peroxide ("BPO" manufactured by Tokyo Chemical Industry Co., Ltd.)

[0154] Example 1 Preparation of Base Particles: 79.8 parts by weight of divinylbenzene (79.8% by weight of 100% by weight of polymerizable components) was added to 20.2 parts by weight of an N-alkylbismaleimide compound (20.2% by weight of 100% by weight of polymerizable components) and stirred to obtain a monomer liquid. Next, 1 part by weight of a polymerization initiator (benzoyl peroxide) was added to the obtained monomer liquid and stirred until homogeneous, to obtain a monomer mixture. 200 parts by weight of a 1.0 wt% aqueous solution of polyvinyl alcohol having a molecular weight of approximately 2000 dissolved in pure water was placed in a reactor. The obtained monomer mixture was added thereto and stirred until the monomer droplets reached the specified particle size. Next, the mixture was heated at 90°C for 9 hours to polymerize the monomer droplets, thereby obtaining particles. The obtained particles were washed three times with hot water and acetone, respectively, and then classified to recover the base particles.

[0155] Preparation of conductive particles: 100 parts by weight of the obtained base particles were added to 500 parts by weight of distilled water and dispersed to obtain a dispersion. A nickel plating solution (pH 8.5) containing 0.14 mol / L of nickel sulfate, 0.46 mol / L of dimethylamine borane, and 0.2 mol / L of sodium citrate was prepared as a nickel plating solution. While stirring the obtained dispersion at 60 ° C, the nickel plating solution was added dropwise to the dispersion at a dropping rate of 30 mL / min for 10 minutes to perform electroless nickel plating. The dispersion was then filtered to remove the particles, which were then washed with water and dried to obtain conductive particles having a conductive layer (Ni layer, thickness 100 nm) disposed on the surface of the base particles.

[0156] Preparation of conductive material (anisotropic conductive paste): 10 parts by weight of the obtained conductive particles, 25 parts by weight of bisphenol A type phenoxy resin, 4 parts by weight of fluorene type epoxy resin, 30 parts by weight of phenol novolac type epoxy resin, and 0.5 parts by weight of SI-60L (manufactured by Sanshin Chemical Industry Co., Ltd.) were blended, and the mixture was degassed and stirred for 3 minutes to obtain a conductive material (anisotropic conductive paste).

[0157] Fabrication of connection structure: A glass-epoxy substrate was prepared, on the top surface of which was formed a Cu electrode pattern (first electrode) with an L / S of 100 μm / 100 μm, and a polyimide substrate was prepared, on the bottom surface of which was formed a Au electrode pattern (second electrode) with an L / S of 100 μm / 100 μm.

[0158] The obtained conductive material (anisotropic conductive paste) was applied to the glass-epoxy substrate to a thickness of 30 μm to form an anisotropic conductive paste layer. Next, the polyimide substrate was laminated on the anisotropic conductive paste layer so that the electrodes faced each other. Thereafter, a pressure heating head was placed on the top surface of the polyimide substrate while adjusting the temperature of the head so that the temperature of the anisotropic conductive paste layer was 120°C, and a pressure of 60 MPa was applied to cure the anisotropic conductive paste layer at 120°C, thereby obtaining a connection structure.

[0159] (Examples 2 to 14 and Comparative Examples 1 to 5) Base particles and conductive particles were obtained in the same manner as in Example 1, except that the type, content (parts by weight), and polymerization temperature (polymerization conditions) of the material of the base particle, the type and thickness of the conductive layer, and the type of core substance were set as shown in Tables 1 to 4. Conductive materials and connection structures were produced in the same manner as in Example 1, except that the obtained conductive particles were used. In Example 11, a conductive particle was produced in which a first conductive layer (Ni layer, 50 nm thick) was disposed on the surface of the base particle, and a second conductive layer (Au layer, 50 nm thick) was disposed on the surface of the first conductive layer. In Example 12, a conductive particle was produced in which a first conductive layer (Ni layer, 50 nm thick) was disposed on the surface of the base particle, and a second conductive layer (Pd layer, 50 nm thick) was disposed on the surface of the first conductive layer.

[0160] (Comparative Example 6) Base particles and conductive particles were obtained in the same manner as in Example 1, except that the heating time during preparation of the base particles was changed from 9 hours to 24 hours, and the type, content (parts by weight) and polymerization temperature (polymerization conditions) of the material of the base particles, the type and thickness of the conductive layer, and the type of core substance were set as shown in Table 4. A conductive material and a connection structure were produced in the same manner as in Example 1, except that the obtained conductive particles were used.

[0161] (Evaluation) (1) Average Particle Diameter The particle diameters of approximately 100,000 particles of the obtained base particles and conductive particles were measured using a particle size distribution measuring device (Multisizer 4 manufactured by Beckman Coulter Inc.) to determine the average particle diameter.

[0162] (2) CV Value of Particle Diameter The CV value of the particle diameter of the obtained base particles and conductive particles was calculated by the method described above.

[0163] (3) Dielectric Constant The dielectric constant of the obtained base particles at 1 GHz was calculated using a dielectric constant measuring device ("Powder Measuring Resonator" manufactured by AET Co., Ltd.).

[0164] (4) Dielectric Loss Tangent The dielectric loss tangent at 1 GHz of the obtained base particles was calculated using a dielectric constant measuring device ("Powder Measuring Resonator" manufactured by AET Co., Ltd.).

[0165] (5) Low Dielectric Property of Film 10 parts by weight of the obtained conductive particles were dispersed in a mixture of 50 parts by weight of epoxy resin (bisphenol A type epoxy resin, "jER" manufactured by Mitsubishi Chemical Corporation), 50 parts by weight of glycidyl ether, and 1 part by weight of SI-60L (manufactured by Sanshin Chemical Industry Co., Ltd.) to obtain a composition. The obtained composition was applied to a substrate to a thickness of 100 μm and heated at 100°C for 2 hours to obtain a film. The dielectric loss tangent of the obtained film was measured using a dielectric constant measuring device (manufactured by AET Co., Ltd., using a cavity resonator). The low dielectric property of the film was evaluated according to the following criteria.

[0166] [Criteria for determining low dielectric properties of films] ○○○: Dielectric loss tangent is 0.003 or less ○○: Dielectric loss tangent is greater than 0.003 and less than 0.006 ○: Dielectric loss tangent is greater than 0.006 and less than 0.01 ×: Dielectric loss tangent is greater than 0.01

[0167] (6) Connection Resistance Between Electrodes The connection resistance between the upper and lower electrodes of the resulting connection structure was measured by a four-terminal method. The connection resistance between the electrodes was evaluated according to the following criteria.

[0168] [Criteria for determining connection resistance between electrodes] ○○○: Connection resistance is 2.0Ω or less ○○: Connection resistance is greater than 2.0Ω and less than 3.0Ω ○: Connection resistance is greater than 3.0Ω and less than 10.0Ω ×: Connection resistance is greater than 10.0Ω

[0169] The compositions of the conductive particles and the results are shown in Tables 1 to 4 below.

[0170]

[0171]

[0172]

[0173]

[0174] REFERENCE SIGNS LIST 1... Base particle 2, 22... Conductive layer 11, 21... Conductive particle 21a, 22a... Protrusion 23... Core material 24... Insulating material 51... Connection structure 52... First connection target member 52a... First electrode 53... Second connection target member 53a... Second electrode

Claims

1. A conductive particle comprising a base particle and a conductive layer disposed on the surface of the base particle, wherein the base particle is a polymer of a polymerizable component, the polymerizable component contains a polymerizable compound having one or more maleimide groups, the content of the polymerizable compound having one or more maleimide groups is 10% by weight or more and 80% by weight or less in 100% by weight of the polymerizable component, the dielectric constant of the base particle is 2.80 F / m or less, and the dielectric loss tangent of the base particle is 0.01 or less.

2. The conductive particle according to claim 1, wherein the polymerizable component comprises a polymerizable compound having one or more ethylenically unsaturated groups other than a maleimide group.

3. The conductive particle according to claim 1 or 2, wherein the polymerizable component comprises divinylbenzene.

4. The conductive particles according to claim 3, wherein the content of divinylbenzene is 20% by weight or more in 100% by weight of the polymerizable component.

5. The conductive particles according to any one of claims 1 to 4, wherein the polymerizable component does not contain a (meth)acrylic compound or contains 35% by weight or less of the (meth)acrylic compound.

6. The conductive particles according to any one of claims 1 to 5, wherein the amount of residual ethylenically unsaturated groups in the polymer of the polymerizable component is 500 ppm or less.

7. The conductive particle according to any one of claims 1 to 6, wherein the conductive layer comprises nickel.

8. The conductive particles according to any one of claims 1 to 7, wherein the conductive particles have a core substance, the conductive particles have protrusions formed on the surface by the core substance, and the core substance does not contain an inorganic oxide.

9. The conductive particles according to any one of claims 1 to 8, wherein the particle diameter of the conductive particles is 1.0 μm or more and 50 μm or less.

10. The conductive particles according to any one of claims 1 to 9, wherein the CV value of the particle diameter of the conductive particles is 10% or less.

11. The conductive particle according to any one of claims 1 to 10, further comprising an insulating material disposed on the outer surface of the conductive layer.

12. A conductive material comprising the conductive particles according to any one of claims 1 to 11 and a binder resin.

13. A connection structure comprising: a first member to be connected having a first electrode on its surface; a second member to be connected having a second electrode on its surface; and a connection part connecting the first member to be connected and the second member to be connected, wherein the material of the connection part contains the conductive particles described in any one of claims 1 to 11, and the first electrode and the second electrode are electrically connected by the conductive particles.

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