Conductive particles, method for manufacturing conductive particles, conductive material, and connection structure

Abstract

Provided are conductive particles with which is it possible to make a crack in a conductive layer less likely to occur, and enhance the conduction reliability of an obtainable connection structure even when mounted at low pressure.　Conductive particle according to the present invention each have a base material particle, and a conductive layer having a crystal structure including grain boundaries, and having protrusions on the outer surface thereof. The conductive layer is disposed on the outer surface of the base material particle, and the grain boundaries in the conductive layer are oriented in the thickness direction of the conductive layer.

Description

Conductive particles, method for producing conductive particles, conductive material, and connection structure

[0001] The present invention relates to conductive particles and a method for producing the conductive particles, and also to a conductive material and a connection structure using the conductive particles.

[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 materials are used to electrically connect electrodes of various connection target components such as flexible printed circuit boards (FPCs), glass substrates, glass epoxy substrates, and semiconductor chips to obtain connection structures. In recent years, as connection target components have become more flexible, there has been a demand for mounting at lower pressures during the manufacture of connection structures in order to prevent damage to the connection target components.

[0004] In conventional conductive particles, the particles themselves deform to increase the contact area between the conductive particles and the electrode in order to improve the electrical conductivity reliability. However, particularly in mounting at low pressure, it is difficult to form sufficient depressions (indentations) on the surface of the electrode, which reduces the contact area between the conductive particles and the electrode, and the connection resistance of the resulting connection structure may increase.

[0005] In general, an oxide film is often formed on the surface of electrodes connected by conductive particles, which prevents sufficient contact between the electrodes and the conductive particles (conductive layer), and the oxide film increases the connection resistance between the electrodes.

[0006] In order to reduce the connection resistance of the resulting connection structure and increase the connection reliability, protrusions may be formed on the outer surfaces of the conductive particles.

[0007] Patent Document 1 listed below discloses a conductive particle (conductive particle) including a composite particle having a resin particle and a non-conductive inorganic particle disposed on the surface of the resin particle, and a metal layer covering the composite particle. In the conductive particle, the metal layer has protrusions on the outer surface of the metal layer, with the non-conductive inorganic particle as a core.

[0008] Furthermore, Patent Document 2 listed below discloses a conductive electroless plated powder (conductive particles) in which relatively tall protrusions are formed on the surfaces of spherical core particles (substrate particles) by autolysis of a plating solution. In this conductive electroless plated powder, minute protrusions of 0.05 μm to 4 μm are formed on the surface of a nickel or nickel alloy coating (conductive layer).

[0009] WO2017 / 138485A1 JP 2000-243132 A

[0010] However, in conductive particles having protrusions formed using a core material (non-conductive inorganic particles) as described in Patent Document 1, the grain boundaries tend to be oriented along the boundary between the core material and the conductive layer, which makes the conductive layer more likely to crack when electrically connecting electrodes. As a result, recesses (indentations) are not sufficiently formed on the surfaces of the electrodes, which can reduce the connection reliability of the resulting connection structure.

[0011] Furthermore, in the conductive particles having protrusions formed by decomposing a plating solution as described in Patent Document 2, the violent chemical reaction that occurs when the plating solution decomposes causes voids to form inside the protrusions, which makes the protrusions prone to becoming brittle, which can result in a decrease in the connection reliability of the resulting connection structure.

[0012] An object of the present invention is to provide conductive particles and a method for manufacturing the conductive particles that can reduce cracking of the conductive layer and improve the connection reliability of the resulting connection structure even when mounted at low pressure. Another object of the present invention is to provide a conductive material and a connection structure using the conductive particles.

[0013] According to a broad aspect of the present invention, there is provided a conductive particle comprising a base particle and a conductive layer having a crystal structure including grain boundaries and having protrusions on its outer surface, the conductive layer being disposed on the outer surface of the base particle, and the grain boundaries in the conductive layer being oriented in the thickness direction of the conductive layer.

[0014] In a specific aspect of the conductive particle according to the present invention, the conductive particle does not include a core material inside the protrusions.

[0015] In a particular aspect of the conductive particle according to the present invention, the grain boundary present in the portion of the conductive layer where the protrusion is located has one end located on the outer surface side of the conductive layer and the other end located on the inner surface side of the conductive layer, and the grain boundary is oriented at an angle to the line connecting the one end of the grain boundary and the center of the conductive particle so that the other end of the grain boundary is located inside the protrusion with respect to the intersection of the line and the inner surface of the conductive layer.

[0016] In a specific aspect of the conductive particle according to the present invention, the outer surface area of ​​the portion where the protrusions are present is 3% or more of 100% of the outer surface area of ​​the conductive layer.

[0017] In a specific aspect of the conductive particles according to the present invention, the conductive particles have a compressive modulus of elasticity of 1000 N / mm when compressed by 20% at 25°C. ２ More than 30000N / mm ２ The following is the result.

[0018] In a specific aspect of the conductive particle according to the present invention, the conductive layer contains tin, nickel, copper, palladium, or gold.

[0019] In a specific aspect of the conductive particle according to the present invention, the conductive particle includes an insulating material disposed on an outer surface of the conductive layer.

[0020] According to a broad aspect of the present invention, there is provided a method for producing the above-mentioned conductive particles, which comprises a step of forming the conductive layer on the outer surface of the base particle, and which forms the protrusions without placing a core material on the outer surface of the base particle.

[0021] In a specific aspect of the method for producing conductive particles according to the present invention, the protrusions are formed without causing decomposition of the plating solution.

[0022] According to a broad aspect of the present invention, there is provided a conductive material including the conductive particles described above and a binder resin.

[0023] According to a broad aspect of the present invention, there is provided 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 the material of the connection portion contains the above-mentioned conductive particles, 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 having a crystal structure including grain boundaries and having protrusions on its outer surface. In the conductive particle according to the present invention, the conductive layer is disposed on the outer surface of the base particle. In the conductive particle according to the present invention, the grain boundaries in the conductive layer are oriented in the thickness direction of the conductive layer. Because the conductive particle according to the present invention has the above configuration, cracks in the conductive layer are less likely to occur, and the connection reliability of the resulting connection structure can be improved even when mounted at low pressure.

[0025] FIG. 1 is a cross-sectional view showing a conductive particle according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a conductive particle according to a second embodiment of the present invention. FIG. 3 is a cross-sectional view showing a conductive particle according to a third embodiment of the present invention. FIG. 4 is a schematic diagram for explaining the inclination angle θ of a grain boundary in a conductive layer. FIG. 5 is a cross-sectional view schematically showing a connection structure using a conductive particle according to the first embodiment of the present invention. FIG. 6 is a transmission electron microscope photograph of a cross-section of a conductive particle obtained in Example 1. FIG. 7 is a transmission electron microscope photograph of a cross-section of a conductive particle obtained in Comparative Example 2. FIG. 8 is a transmission electron microscope photograph of a cross-section of a conductive particle obtained in Comparative Example 3.

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

[0027] (Conductive Particle) The conductive particle according to the present invention comprises a base particle and a conductive layer having a crystal structure including grain boundaries and having protrusions on the outer surface. In the conductive particle according to the present invention, the conductive layer is disposed on the outer surface of the base particle. In the conductive particle according to the present invention, the grain boundaries in the conductive layer are oriented in the thickness direction of the conductive layer.

[0028] After extensive research, the inventors discovered that controlling the orientation of grain boundaries in the conductive layer can reduce cracking in the conductive layer and improve the connection reliability of the resulting connection structure, even when mounted at low pressure. In the conductive particles according to the present invention, the conductive layer has a crystalline structure including grain boundaries, and the grain boundaries in the conductive layer are oriented in the thickness direction of the conductive layer. This reduces cracking in the conductive layer and improves the connection reliability of the resulting connection structure, even when mounted at low pressure. Furthermore, in the conductive particles according to the present invention, the conductive layer has protrusions on the outer surface, which effectively form recesses (indentations) on the surface of the electrode, even when mounted at low pressure, thereby effectively eliminating oxide coatings. As a result, the connection reliability of the resulting connection structure can be further improved.

[0029] The present inventors have found that the combination of grain boundaries of a conductive layer having a specific orientation and protrusions formed on the outer surface of the conductive layer significantly reduces the likelihood of cracking in the conductive layer, and significantly improves the connection reliability of the resulting connection structure even when mounted at low pressure. Furthermore, since the conductive particles according to the present invention have the above-mentioned configuration, they can improve gap controllability.

[0030] Furthermore, the inventors have discovered that by combining grain boundaries of a conductive layer having a specific orientation, protrusions formed on the outer surface of the conductive layer, and a configuration in which the conductive particles do not have a core material inside the protrusions, it is possible to make cracks in the conductive layer even less likely to occur, and to further significantly improve the connection reliability of the resulting connection structure even when mounted at low pressure.

[0031] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. Note that in Fig. 1 and the figures described below, the size and thickness of each component may differ from the actual size and thickness for convenience of illustration.

[0032] FIG. 1 is a cross-sectional view showing a conductive particle according to a first embodiment of the present invention.

[0033] The conductive particle 1 shown in Figure 1 comprises a base particle 2 and a conductive layer 3 having a crystal structure including grain boundaries and having protrusions 3a on its outer surface. In the conductive particle 1, the conductive layer 3 has a crystal structure including grain boundaries. In the conductive particle 1, the conductive layer 3 has protrusions 3a on its outer surface. The conductive particle 1 has protrusions on its outer surface. In the conductive particle 1, the conductive layer 3 is disposed on the outer surface of the base particle 2 and is in contact with the base particle 2.

[0034] The conductive layer 3 covers the outer surface of the base particle 2. The conductive particle 1 is a coated particle in which the outer surface of the base particle 2 is coated with the conductive layer 3. The conductive particle 1 has the conductive layer 3 on its surface.

[0035] The conductive particle 1 does not have a core material inside the protrusions 3 a. The conductive particle 1 does not have a core material disposed inside the protrusions 3 a. The conductive particle 1 does not have a core material disposed on the outer surface of the base particle 2.

[0036] In the conductive particles, the conductive layer may cover the entire outer surface of the base particle, or the conductive layer may cover only a portion of the outer surface of the base particle.

[0037] FIG. 2 is a cross-sectional view showing a conductive particle according to a second embodiment of the present invention.

[0038] The conductive particle 11 shown in FIG. 2 includes a base particle 2 and a conductive layer 13 having protrusions 13a on its outer surface. In the conductive particle 11, the conductive layer 13 is disposed on the outer surface of the base particle 2. In the conductive particle 11, the conductive layer 13 is a two-layer conductive layer. In the conductive particle 11, the conductive layer 13 includes a first conductive layer 13A and a second conductive layer 13B. In the conductive layer 13, the first conductive layer 13A is disposed on the outer side of the base particle 2, and the second conductive layer 13B is disposed on the outer side of the first conductive layer 13A. In the conductive layer 13, the first conductive layer 13A is laminated on the outer surface of the base particle 2, and the second conductive layer 13B is laminated on the outer surface of the first conductive layer 13A.

[0039] In the conductive particle 11, the conductive layer 13 includes a first conductive layer 13A having a crystal structure including grain boundaries and having protrusions 13Aa on its outer surface, and a second conductive layer 13B having no crystal structure including grain boundaries and having protrusions 13Ba on its outer surface. In the conductive particle 11, the first conductive layer 13A has a crystal structure including grain boundaries. In the conductive particle 11, the second conductive layer 13B does not have a crystal structure including grain boundaries. In the conductive particle 11, the conductive layer 13 has protrusions 13a on its outer surface. The first conductive layer 13A has protrusions 13Aa on its outer surface. The second conductive layer 13B has protrusions 13Ba on its outer surface. Note that when the first conductive layer has a crystal structure including grain boundaries and has protrusions on its outer surface, the second conductive layer may or may not have a crystal structure including grain boundaries. Furthermore, when the second conductive layer has a crystal structure including grain boundaries and has protrusions on its outer surface, the first conductive layer does not have to have a crystal structure including grain boundaries and does not have protrusions on its outer surface.

[0040] The conductive particle 11 does not have a core material inside the protrusions 13a. The conductive particle 11 does not have a core material inside the protrusions 13Aa. The conductive particle 11 does not have a core material inside the protrusions 13Ba. In the conductive particle 11, a core material is not arranged inside the protrusions 13a. In the conductive particle 11, a core material is not arranged inside the protrusions 13Aa. In the conductive particle 11, a core material is not arranged inside the protrusions 13Ba. In the conductive particle 11, a core material is not arranged on the outer surface of the base particle 2.

[0041] FIG. 3 is a cross-sectional view showing a conductive particle according to a third embodiment of the present invention.

[0042] The conductive particle 21 shown in Fig. 3 comprises a base particle 2 and a conductive layer 23 having a crystal structure including grain boundaries and having protrusions 23a on the outer surface. In the conductive particle 21, the conductive layer 23 has a crystal structure including grain boundaries. In the conductive particle 21, the conductive layer 23 has protrusions 23a on the outer surface. The conductive particle 21 has protrusions on the outer surface. In the conductive particle 21, the conductive layer 23 is disposed on the outer surface of the base particle 2 and is in contact with the base particle 2.

[0043] The conductive particles 21 include an insulating material 24 disposed on the outer surface of the conductive layer 23. At least a portion of the outer surface of the conductive layer 23 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 include the insulating material disposed on the outer surface of the conductive layer.

[0044] The conductive particle 21 does not have a core material inside the protrusions 23 a. In the conductive particle 21, a core material is not disposed inside the protrusions 23 a. In the conductive particle 21, a core material is not disposed on the outer surface of the base particle 2.

[0045] Other details of the conductive particles will be described below.

[0046] 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.

[0047] The particle diameter of the conductive particles is preferably 1.0 μm or more, more preferably 2.0 μm or more, and preferably 50 μm or less, more preferably 25 μm or less. If the particle diameter of the conductive particles is above the lower limit and below the upper limit, when electrodes are connected using the conductive particles, the contact area between the conductive particles and the electrodes is sufficiently large, and agglomerated conductive particles are less likely to form when forming a conductive layer. In addition, the gap between the electrodes connected via the conductive particle body is not too large, and the conductive layer is less likely to peel off from the surface of the base particle.

[0048] The particle diameter of the conductive particles is preferably an average particle diameter, and the average particle diameter indicates 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 an optical microscope and calculating the average particle diameter of each conductive particle, or by performing laser diffraction particle size distribution measurement.

[0049] From the viewpoint of improving the reliability of conduction between electrodes, the coefficient of variation (CV value) of the particle diameter of the conductive particles is preferably 10% or less, and more preferably 5% or less.

[0050] The coefficient of variation (CV value) can be measured as follows.

[0051] CV value (%) = (ρ / Dn) × 100, where ρ: standard deviation of particle diameter of conductive particles, and Dn: average particle diameter of conductive particles.

[0052] The shape of the conductive particles is not particularly limited, and may be spherical, may be a shape other than spherical, or may be flat or the like.

[0053] The compressive elastic modulus (20% K value) of the conductive particles when compressed by 20% at 25° C. is preferably 1000 N / mm ２ More preferably, 3000 N / mm ２ More preferably, 5000 N / mm ２ or more, preferably 30,000 N / mm ２ or less, more preferably 20,000 N / mm ２ When the 20% K value of the conductive particles is equal to or greater than the lower limit and equal to or less than the upper limit, damage to the connection target component can be suppressed, and the connection resistance can be further effectively reduced even when mounted at low pressure. Furthermore, when a conductive layer is formed on the surface, aggregation can be effectively suppressed, making it less likely for the conductive layer to crack.

[0054] The compressive elastic modulus (20% K value) of the conductive particles can be measured as follows.

[0055] Using a micro-compression tester, one conductive particle is compressed with the end face of a smooth cylindrical indenter (diameter 50 μm, made of diamond) under conditions of 25°C, a compression speed of 0.3 mN / sec, and a maximum test load of 20 mN. The load value (N) and compression displacement (mm) at this time are measured. From the obtained measured values, the compressive modulus (20% K value) of the conductive particle can be calculated using the following formula. As the micro-compression tester, for example, a "Fisherscope H-100" manufactured by Fischer is used. The compressive modulus (20% K value) of the conductive particle is preferably calculated by arithmetically averaging the compressive modulus (20% K value) of 50 arbitrarily selected conductive particles.

[0056] 20% 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 20%; S: Compression displacement (mm) when the conductive particle is compressed and deformed by 20%; R: Radius of the conductive particle (mm).

[0057] The compressive elastic modulus universally and quantitatively represents the hardness of the conductive particles. By using the compressive elastic modulus, the hardness of the conductive particles can be quantitatively and unambiguously represented.

[0058] <Base Particles> Examples of the base particles include resin particles, inorganic particles excluding metal particles, organic-inorganic hybrid particles, and metal particles. The base particles are preferably base particles excluding metal particles, and more preferably resin particles, inorganic particles excluding metal particles, or organic-inorganic hybrid particles. The base particles may be core-shell particles having a core and a shell disposed on the surface of the core. The core may be an organic core, and the shell may be an inorganic shell.

[0059] Examples of materials for the resin particles include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; polycarbonate, polyamide, phenol-formaldehyde resin, melamine-formaldehyde resin, benzoguanamine-formaldehyde resin, urea-formaldehyde resin, phenolic resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polyethylene terephthalate, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyamide-imide, polyether ether ketone, polyether sulfone, and divinylbenzene polymer. The divinylbenzene polymer may be a divinylbenzene copolymer. Examples of the divinylbenzene copolymer include a divinylbenzene-styrene copolymer and a divinylbenzene-(meth)acrylic acid ester copolymer. The material of the resin particles is preferably a polymer obtained by polymerizing one or more polymerizable monomers having an ethylenically unsaturated group, since this allows the hardness of the resin particles to be easily controlled within a suitable range.

[0060] When the resin particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, the polymerizable monomer having an ethylenically unsaturated group may be a non-crosslinkable monomer or a crosslinkable monomer.

[0061] 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)acrylate compounds 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; and alkyl (meth)acrylate compounds such as 2-hydroxyethyl (meth)acrylate and glycerol (meth)acrylate. nitrile-containing monomers such as (meth)acrylonitrile; vinyl ether compounds such as methyl vinyl ether, ethyl vinyl ether, and propyl vinyl ether; vinyl acid ester compounds 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, vinyl chloride, vinyl fluoride, and chlorostyrene.

[0062] 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, dipentaerythritol poly(meth)acrylate, pentaerythritol tetra(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, (poly)ethylene glycol Examples of suitable crosslinkable monomers include polyfunctional (meth)acrylate compounds such as 1,4-butanediol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate; triallyl (iso)cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, and silane-containing monomers such as γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane. From the viewpoint of maintaining the shape of the flux-containing particles even at the glass transition temperature of the resin particles, the crosslinkable monomer is preferably (poly)ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, or dipentaerythritol poly(meth)acrylate.

[0063] The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group by a known method, such as a suspension polymerization method in the presence of a radical polymerization initiator, or a method in which non-crosslinked seed particles are used to swell and polymerize the monomer together with the radical polymerization initiator.

[0064] When the base particles are inorganic particles other than metals or organic-inorganic hybrid particles, the inorganic materials for forming the base particles include silica, alumina, barium titanate, zirconia, and carbon black.The inorganic materials are preferably not metals.The particles formed by silica include, for example, particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, and then optionally baking the particles.The organic-inorganic hybrid particles include, for example, organic-inorganic hybrid particles formed by crosslinked alkoxysilyl polymers and acrylic resins.

[0065] The organic-inorganic hybrid particles are preferably core-shell organic-inorganic hybrid particles having a core and a shell disposed on the surface of the core. The core is preferably an organic core. The shell is preferably an inorganic shell. From the viewpoint of effectively reducing the connection resistance between electrodes, the base particle is preferably an organic-inorganic hybrid particle having an organic core and an inorganic shell disposed on the surface of the organic core.

[0066] Examples of the material for the organic core include the materials for the resin particles described above.

[0067] Examples of materials for the inorganic shell include the inorganic substances listed as materials for the base particle described above. The material for the inorganic shell is preferably silica. The inorganic shell is preferably formed by forming a shell-like substance from a metal alkoxide on the surface of the core by a sol-gel method and then firing the shell-like substance. The metal alkoxide is preferably a silane alkoxide. The inorganic shell is preferably formed from a silane alkoxide.

[0068] When the base particles are metal particles, examples of the metal that is the material of the metal particles include silver, copper, nickel, silicon, gold, and titanium.

[0069] The particle diameter of the base particle is preferably 0.5 μm or more, more preferably 1.5 μm or more, and preferably 49.95 μm or less, more preferably 39.95 μm or less. When the particle diameter of the base particle is equal to or greater than the lower limit and equal to or less than the upper limit, the distance between the electrodes becomes small, and even if the thickness of the conductive layer is increased, small conductive particles can be obtained. Furthermore, when the conductive layer is formed on the outer surface of the base particle, aggregation is difficult, and aggregated conductive particles are difficult to form.

[0070] The shape of the base particles is not particularly limited, and may be spherical, or may be a shape other than spherical, such as flat.

[0071] The particle diameter of the base particle is preferably an average particle diameter, and the average particle diameter is preferably a number average particle diameter. The particle diameter of the base particle is determined using a particle size distribution measuring device or the like. The particle diameter of the base particle is preferably determined by observing 50 random base particles with an electron microscope or 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.

[0072] 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 conductive particles. An ion milling machine (Hitachi High-Technologies Corporation's IM4000) was used to cut out a cross section of the conductive particles so that it passed 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.

[0073] <Conductive Layer> The conductive particle has a crystal structure including grain boundaries and includes a conductive layer (hereinafter sometimes referred to as "conductive layer X") having protrusions on its outer surface. The conductive layer X is disposed on the outer surface of the base particle. In this specification, the term "grain boundary" refers to the boundary between crystal grains.

[0074] The grain boundaries and crystalline structure of the conductive layer X can be observed by imaging the cross section of the conductive particles using, for example, a transmission electron microscope (TEM).

[0075] From the viewpoint of making it more difficult for cracks to occur in the conductive layer, the cross-sectional area of ​​the conductive layer X in the thickness direction is set to 1 μm ２ The number of grain boundaries per unit area is preferably 2 or more, more preferably 8 or more, and even more preferably 20 or more, and is preferably 400 or less, more preferably 300 or less, and even more preferably 200 or less.

[0076] In the conductive particles, the grain boundaries in the conductive layer X are oriented in the thickness direction of the conductive layer X. The grain boundaries preferably include both grain boundaries present in portions of the conductive layer X where the protrusions are not present and grain boundaries present in portions of the conductive layer X where the protrusions are present.

[0077] The grain boundary present in the portion of the conductive layer X where there is no protrusion has one end located on the outer surface side of the conductive layer X and the other end located on the inner surface side of the conductive layer X. From the viewpoint of making it more difficult for cracks to occur in the conductive layer, it is preferable that the grain boundary present in the portion of the conductive layer X where there is no protrusion be perpendicular to a tangent to the outer surface of the conductive layer X at the one end of the grain boundary. From the viewpoint of making it more difficult for cracks to occur in the conductive layer, it is preferable that the grain boundary present in the portion of the conductive layer X where there is no protrusion be perpendicular to a tangent to the inner surface of the conductive layer X at the other end of the grain boundary. From the viewpoint of making it more difficult for cracks to occur in the conductive layer, it is preferable that the grain boundary present in the portion of the conductive layer X where there are no protrusions is perpendicular to a tangent to the outer surface of the conductive layer X at one end of the grain boundary, and is perpendicular to a tangent to the inner surface of the conductive layer X at the other end of the grain boundary at the other end of the grain boundary. From the viewpoint of making it more difficult for cracks to occur in the conductive layer, it is preferable that the grain boundary present in the portion of the conductive layer X where there are no protrusions is perpendicular to the outer surface and the inner surface of the conductive layer X. From the viewpoint of making it more difficult for cracks to occur in the conductive layer, it is preferable that the grain boundary present in the portion of the conductive layer X where there are no protrusions is present on an extension of a straight line connecting the other end of the grain boundary and the center of the conductive particle (substrate particle). Furthermore, it is preferable that the grain boundary present in the portion of the conductive layer X where there are no protrusions is part of a straight line connecting the one end of the grain boundary and the center of the conductive particle (substrate particle).

[0078] From the viewpoint of making it more difficult for cracks to occur in the conductive layer, the number of grain boundaries that intersect perpendicularly with the outer and inner surfaces of the conductive layer X out of 100% of the grain boundaries present in the portion of the conductive layer X where no protrusions are present is preferably 30% or more, more preferably 50% or more, even more preferably 80% or more, and most preferably 100% (total amount). There is no particular limitation on the upper limit of the number of grain boundaries that intersect perpendicularly with the outer and inner surfaces of the conductive layer X out of 100% of the grain boundaries present in the portion of the conductive layer X where no protrusions are present. The number of grain boundaries that intersect perpendicularly with the outer and inner surfaces of the conductive layer X out of 100% of the grain boundaries present in the portion of the conductive layer X where no protrusions are present may be 90% or less, 80% or less, or 50% or less.

[0079] Furthermore, the grain boundary present in the portion of the conductive layer X where the protrusion is present has one end located on the outer surface side of the conductive layer X and the other end located on the inner surface side of the conductive layer X. From the viewpoint of making it more difficult for cracks to occur in the conductive layer, it is preferable that the grain boundary present in the portion of the conductive layer X where the protrusion is present is not perpendicular to the tangent to the outer surface of the conductive layer X at the one end of the grain boundary, and is not perpendicular to the tangent to the inner surface of the conductive layer X at the other end of the grain boundary. From the viewpoint of making it more difficult for cracks to occur in the conductive layer, it is preferable that the grain boundary present in the portion of the conductive layer X where the protrusion is present is oriented at an angle with respect to a straight line connecting the one end of the grain boundary and the center of the conductive particle. From the viewpoint of making it more difficult for cracks to occur in the conductive layer, it is preferable that the other end of the grain boundary is oriented at an angle with respect to the straight line connecting the one end of the grain boundary and the center of the conductive particle so that the other end of the grain boundary is located inside the protrusion with respect to the intersection of the straight line connecting the one end of the grain boundary and the center of the conductive particle with the inner surface of the conductive layer X.

[0080] The boundary between the portion of the conductive layer X with the protrusion and the portion without the protrusion on the outer surface of the conductive layer X is the base of the protrusion. The base of the protrusion is the starting point of the rise of the conductive layer X. The portion without the protrusion of the conductive layer X is the portion of the conductive layer X located outside the protrusion with respect to a line connecting the base of the protrusion and the center of the conductive particle. The portion of the conductive layer X with the protrusion is the portion of the conductive layer X located inside the protrusion with respect to a line connecting the base of the protrusion and the center of the conductive particle. The grain boundary present in the portion of the conductive layer X with the protrusion includes a grain boundary whose one end is the boundary between the portion of the conductive layer X with the protrusion and the portion without the protrusion. It is preferable that the one end of the grain boundary present in the portion of the conductive layer X with the protrusion is located at the base of the protrusion. In other words, the grain boundary present in the portion of the conductive layer X with the protrusion includes a grain boundary whose one end is the base of the protrusion. From the viewpoint of making it more difficult for cracks to occur in the conductive layer, it is preferable that the grain boundary in the conductive layer X includes, as a grain boundary present in a portion of the conductive layer X where the protrusion is present, a grain boundary having, as one end thereof, a boundary (a base of the protrusion) between a portion of the conductive layer X where the protrusion is present and a portion of the conductive layer X where the protrusion is not present. From the viewpoint of making it more difficult for cracks to occur in the conductive layer, it is preferable that the grain boundary present in a portion of the conductive layer X where the protrusion is present is a grain boundary having, as one end thereof, a boundary (a base of the protrusion) between a portion of the conductive layer X where the protrusion is present and a portion of the conductive layer X where the protrusion is not present.

[0081] FIG. 4 is a schematic diagram illustrating the inclination angle θ of a grain boundary in a conductive layer X. FIG. 4 shows a portion of the conductive particle 1 shown in FIG. 1. In FIG. 4, grain boundaries K and L in the conductive layer 3 (conductive layer X) are oriented in the thickness direction of the conductive layer 3. The grain boundary K is a grain boundary that exists in a portion of the conductive layer 3 where there are no protrusions 3a. The grain boundary K is perpendicular to the outer and inner surfaces of the conductive layer 3. The grain boundary L is a grain boundary that exists in a portion of the conductive layer 3 where there are protrusions 3a. The grain boundary L is a grain boundary whose one end is the boundary (the base of the protrusion) between the portion of the conductive layer 3 where there are protrusions 3a and the portion where there are no protrusions 3a. The grain boundary L is oriented at an angle with respect to a straight line (shown by a dotted line) connecting one end of the grain boundary L and the center of the conductive particle. The grain boundary L is oriented at an angle to a line (shown by a dotted line) connecting one end of the grain boundary L and the center of the conductive particle so that the other end of the grain boundary L is located inside the protrusion 3a from the intersection of the line and the inner surface of the conductive layer 3. In Fig. 4, the grain boundary is shown as a straight line for convenience of illustration.

[0082] When a grain boundary (grain boundary L) exists, with one end of the grain boundary being the boundary (the base of the protrusion) between a portion of the conductive layer with the protrusion and a portion without the protrusion, the angle formed by the grain boundary and a straight line (shown by a dotted line in Figure 4) connecting the one end of the grain boundary and the center of the conductive particle (substrate particle) is defined as the inclination angle θ of the grain boundary in the conductive layer X.

[0083] From the viewpoint of making it even more difficult for cracks to occur in the conductive layer, the inclination angle θ of the grain boundary (grain boundary L) having the base of the protrusion as one end of the grain boundary is preferably 0° or more, more preferably 3° or more, even more preferably 5° or more, and is preferably 90° or less, more preferably 60° or less, even more preferably 40° or less.

[0084] The inclination angle θ of the grain boundary (grain boundary L) with the base of the protrusion as one end of the grain boundary can be measured by observing the cross section of the conductive particle using, for example, a transmission electron microscope (TEM).

[0085] The conductive layer X preferably contains a metal. The metal constituting the conductive layer X is not particularly limited. Examples of the metal include tin, gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, ruthenium, germanium, and cadmium, as well as alloys thereof. Furthermore, tin-doped indium oxide (ITO) may be used as the metal. Only one of the metals may be used, or two or more of them may be used in combination.

[0086] From the viewpoint of improving the conduction reliability, the conductive layer X preferably contains tin, nickel, copper, palladium, or gold, more preferably contains gold or nickel, and further preferably contains nickel.

[0087] The area covered by the conductive layer X (coverage by the conductive layer X) of the 100% outer surface area of ​​the base particle is preferably 80% or more, more preferably 90% or more. There is no particular upper limit to the coverage by the conductive layer X. The coverage by the conductive layer X may be 100%. When the coverage by the conductive layer X is equal to or greater than the lower limit, the electrical connection reliability can be effectively improved when electrodes are electrically connected.

[0088] The thickness of the conductive layer X is preferably 50 nm or more, more preferably 100 nm or more, and preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less. When the thickness of the conductive layer X is equal to or greater than the above lower limit and equal to or less than the above upper limit, the electrical connection reliability is improved, and the conductive particles do not become too hard, allowing the conductive particles to be sufficiently deformed when connecting electrodes.

[0089] The thickness of the conductive layer X can be measured by observing the cross section of the conductive particles using, for example, a transmission electron microscope (TEM).

[0090] The conductive layer may be a single layer or multiple layers. The conductive layer may include multiple conductive layers X, or may include the conductive layer X and a conductive layer other than the conductive layer X. The conductive particles may include a conductive layer other than the conductive layer X. The conductive particles (conductive layers) may include a conductive layer that does not have a crystal structure including grain boundaries, a conductive layer that does not have protrusions on its outer surface, or a conductive layer that does not have a crystal structure including grain boundaries and does not have protrusions on its outer surface. When the conductive particles (conductive layers) include a conductive layer other than the conductive layer X, the conductive layer other than the conductive layer X may be disposed on the inner surface side of the conductive layer X or on the outer surface side of the conductive layer X. When the conductive layer other than the conductive layer X is disposed on the inner surface side of the conductive layer X, the coverage rate of the conductive layer can be increased, and the connection reliability of the resulting connection structure can be further effectively improved. When the conductive layer other than the conductive layer X is disposed on the outer surface side of the conductive layer X, the connection reliability of the resulting connection structure can be further improved. From the viewpoint of further enhancing the connection reliability of the resulting connection structure, when the conductive particles (conductive layer) include a conductive layer other than the conductive layer X, it is preferable that the conductive layer other than the conductive layer X is disposed on the outer surface of the conductive layer X.

[0091] From the viewpoint of further improving the connection reliability of the resulting connection structure, the conductive layer other than the conductive layer X preferably contains palladium, nickel, gold, silver, copper, tin, or ruthenium, more preferably contains palladium or gold, even more preferably contains gold, and particularly preferably is gold. Furthermore, when the metal constituting the outer surface of the conductive layer other than the conductive layer X is gold, corrosion resistance is further improved.

[0092] The thickness of the conductive layer other than the conductive layer X is preferably 1.0 nm or more, more preferably 5.0 nm or more, and preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 50 nm or less. When the thickness of the conductive layer other than the conductive layer X is equal to or greater than the above lower limit and equal to or less than the above upper limit, the coverage rate of the conductive layer can be increased, and when electrodes are electrically connected, the conduction reliability can be effectively improved.

[0093] The conductive layer X has protrusions on its outer surface. It is preferable that there are multiple protrusions. Generally, an oxide film is often formed on the surface of an electrode that contacts the conductive particles. Since the conductive layer X has protrusions on its outer surface, the protrusions can effectively remove the oxide film during conductive connection. Furthermore, the protrusions can effectively form recesses (indentations) on the surface of the electrode. This ensures reliable contact between the electrode and the conductive layer, sufficiently increasing the contact area between the conductive particles and the electrode, and effectively reducing the connection resistance. Furthermore, when the conductive particles have an insulating material on their surfaces, or when the conductive particles are dispersed in a binder and used as a conductive material, the protrusions of the conductive particles can effectively remove the insulating material or binder between the conductive particles and the electrode. This allows the contact area between the conductive particles and the electrode to be sufficiently increased, effectively reducing the connection resistance.

[0094] From the viewpoint of more effectively exerting the effects of the present invention, it is preferable that the conductive particles do not have a core material inside the protrusions, that the conductive particles do not have a core material outside the base particle, and that the conductive particles do not have a core material on the outer surface of the base particle.

[0095] The average height of the plurality of protrusions is preferably 10 nm or more, more preferably 30 nm or more, preferably 900 nm or less, more preferably 200 nm or less, and even more preferably 100 nm 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 electrodes can be effectively reduced. The average height of the protrusions can be calculated by the following method. 50 conductive particles of the present invention are observed under an electron microscope or optical microscope, and the height of all the protrusions on the periphery of the observed conductive particles is measured. The height of the convex portions is measured using a surface on which no protrusions are formed as a reference surface, and the average height is calculated.

[0096] From the viewpoint of further improving the connection reliability, the outer surface area of ​​the portion where the protrusions are present (protrusion formation rate) of 100% of the surface area of ​​the conductive layer X is preferably 3% or more, more preferably 10% or more, and preferably 70% or less, more preferably 40% or less.

[0097] The outer surface area of ​​the portion where the protrusions are present relative to 100% of the outer surface area of ​​the conductive layer X (protrusion formation rate) can be measured by the following method, regardless of whether the conductive particles are spherical or non-spherical: When 50 conductive particles are viewed in plan using an electron microscope, the proportion (%) of the area of ​​the portion where the protrusions are present relative to 100% of the area of ​​a circle whose diameter is 70% of the particle diameter of the conductive particles is measured, and the average value is calculated.

[0098] (Insulating Material) The conductive particles may comprise 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 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 removed even more easily. The insulating material is preferably an insulating resin layer or insulating particles, more preferably insulating particles. The insulating particles are preferably insulating resin particles.

[0099] (Method for manufacturing conductive particles) The method for manufacturing conductive particles according to the present invention is a method for manufacturing the above-mentioned conductive particles. The method for manufacturing conductive particles according to the present invention includes a step of forming the conductive layer on the outer surface of the base particle. In the method for manufacturing conductive particles according to the present invention, protrusions are formed without disposing a core material inside the protrusions. In the method for manufacturing conductive particles according to the present invention, it is preferable to form the protrusions without a core material being present inside the protrusions.

[0100] The method for manufacturing conductive particles according to the present invention has the above-mentioned configuration, which makes it possible to make the conductive layer less susceptible to cracking, and also to improve the connection reliability of the resulting connection structure even when mounted at low pressure.

[0101] In conventional methods for producing conductive particles, in order to improve the connection reliability of the resulting connection structure, a core material is sometimes attached to the outer surface of a base particle to produce conductive particles having the core material inside the protrusions. However, in such conductive particles, the grain boundaries tend to be oriented along the boundary between the core material and the conductive layer, which makes the conductive layer more likely to crack when electrically connecting electrodes. As a result, the connection reliability of the resulting connection structure may be reduced.

[0102] Furthermore, in a manufacturing method in which protrusions are formed on the outer surface of a conductive layer by decomposing a plating solution, there is a problem in that voids are generated inside the protrusions due to the violent chemical reaction that occurs when the plating solution decomposes, making the protrusions prone to becoming brittle. As a result, the connection reliability of the resulting connection structure may be reduced. Furthermore, when protrusions are formed by decomposing a plating solution, the protrusions tend to stack or connect, making it difficult to control the gap between the electrodes of the resulting connection structure. Therefore, in the manufacturing method of conductive particles according to the present invention, it is preferable to form protrusions without causing decomposition of the plating solution.

[0103] Methods for forming the conductive layer X on the outer surface of the base particle 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 X 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.).

[0104] Methods for forming protrusions on the outer surface of the conductive layer X include electroless plating, electroplating, physical vapor deposition, physical adsorption, etc. From the viewpoint of more effectively exerting the effects of the present invention, it is preferable to form protrusions on the outer surface of the conductive layer X by electroless plating.

[0105] Examples of a method for forming the conductive layer X so that the grain boundaries in the conductive layer X are oriented in the thickness direction of the conductive layer X include a method using electroless plating and a method using electroplating.

[0106] Examples of methods for forming the conductive layer X (protrusions) so that the grain boundaries present in the portions of the conductive layer X where the protrusions are present satisfy the above-mentioned preferred aspects include the following methods: A method of adjusting the pH of the electroless plating solution; A method of adding an arbitrary chemical solution to the electroless plating solution; A method of adjusting the pH of the electroless plating solution and adding an arbitrary chemical solution to the electroless plating solution.

[0107] The electroless plating solution used to form the conductive layer X and the protrusions preferably contains a metal salt. Examples of the metal salt include nickel sulfate, nickel chloride, nickel hydroxide, and nickel carbonate. From the viewpoint of improving the coverage rate of the conductive layer, the metal ion concentration of the electroless plating solution is preferably 0.1 mol / L or more, more preferably 0.3 mol / L or more, and even more preferably 0.5 mol / L or more, and is preferably 10.0 mol / L or less, more preferably 5.0 mol / L or less, and even more preferably 2.0 mol / L or less.

[0108] The pH of the electroless plating solution is preferably 8.0 or higher, more preferably 9.0 or higher, and preferably 12.0 or lower, more preferably 11.0 or lower. When the pH of the electroless plating solution is equal to or higher than the lower limit, the conductive layer X (protrusions) can be effectively formed so that the grain boundaries present in the portions of the conductive layer X where the protrusions are present satisfy the above-mentioned preferred aspects. When the pH of the electroless plating solution is equal to or lower than the upper limit, the productivity of the conductive particles can be increased.

[0109] The electroless plating solution may contain a complexing agent, a reducing agent, a dispersing agent, or the like.

[0110] The complexing agent is not particularly limited. Examples of the complexing agent include ammonia, trimethylamine, succinic acid, sodium citrate, boric acid, and glycine. From the viewpoint of more effectively exerting the effects of the present invention, the complexing agent preferably contains sodium citrate, boric acid, or glycine.

[0111] The reducing agent is not particularly limited. Examples of the reducing agent include sodium borohydride, hydrazine, sodium hypophosphite, and dimethylamine borane. From the viewpoint of successfully forming the conductive layer and the protrusions, the reducing agent preferably contains sodium hypophosphite or dimethylamine borane.

[0112] The dispersant is not particularly limited. From the viewpoint of more effectively exerting the effects of the present invention, the dispersant is preferably a nonionic dispersant, and more preferably polyethylene glycol. The weight-average molecular weight of the dispersant is preferably 200 or more, more preferably 1,000 or more, and preferably 200,000 or less, more preferably 10,000 or less. The concentration of the dispersant in the electroless plating solution is preferably 0.01 g / L or more, more preferably 0.1 g / L or more, even more preferably 1.0 g / L or more, and preferably 100 g / L or less, more preferably 50 g / L or less, and even more preferably 10 g / L or less. When the molecular weight and concentration of the dispersant are above the lower limit, the productivity of the conductive particles can be improved. When the molecular weight and concentration of the dispersant are below the upper limit, the conductive layer X (protrusions) can be effectively formed so that the grain boundaries present in the portion of the conductive layer X where the protrusions are present satisfy the above-mentioned preferred embodiment. The weight-average molecular weight indicates the weight-average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

[0113] (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 and used to obtain 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 circuit connection material.

[0114] The binder resin is not particularly limited. Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, and elastomers. Only one type of the binder resin may be used, or two or more types may be used in combination.

[0115] 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.

[0116] 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.

[0117] The conductive material according to the present invention can be used as a conductive paste, a conductive film, or the like. When the conductive material according to the present invention is a conductive film, a film not containing conductive particles may be laminated on a conductive film containing conductive particles. The conductive paste is preferably an anisotropic conductive paste. The conductive film is preferably an anisotropic conductive film.

[0118] 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 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.

[0119] 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 preferably 40% by weight or less, more preferably 20% by weight or less, and even more preferably 10% by weight or less. When the content of the conductive particles is equal to or more than the lower limit and equal to or less than the upper limit, the reliability of conduction between electrodes can be improved.

[0120] (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.

[0121] FIG. 5 is a cross-sectional view that schematically shows a connection structure using conductive particles according to the first embodiment of the present invention.

[0122] The connection structure 51 shown in Fig. 5 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 from a conductive material containing conductive particles 1. The connection portion 54 is preferably formed by curing a conductive material containing a plurality of conductive particles 1. Note that in Fig. 5, the conductive particles 1 are shown schematically for convenience of illustration. Instead of the conductive particles 1, conductive particles 11 or conductive particles 21 may be used.

[0123] 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 one or more conductive particles 1. Therefore, the first connection target member 52 and the second connection target member 53 are electrically connected by the conductive particles 1.

[0124] The method for manufacturing the connection structure is not particularly limited. One example of a method for manufacturing a connection structure is a method in which the conductive material is placed between a first connection target member and a second connection target member to obtain a laminate, and then the laminate is heated and pressurized (a method of compression bonding (thermocompression bonding)). The pressure of the compression bonding (thermocompression bonding) is preferably 5 MPa or more, more preferably 10 MPa or more, and preferably 90 MPa or less, more preferably 70 MPa or less. The heating temperature of the compression bonding (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 heating temperature of the compression bonding (thermocompression bonding) are above the lower limit and below the upper limit, the connection reliability can be further improved. Furthermore, by using the conductive particles according to the present invention, the connection reliability can be sufficiently improved even when the compression bonding pressure is below the upper limit. The conductive particles are preferably used by compression bonding at a pressure below the upper limit, and more preferably by compression bonding at a pressure above the lower limit and below the upper limit.

[0125] 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 circuit boards 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. As connection target members become more flexible, there is a demand for lower mounting pressures during the manufacture of connection structures to prevent damage to the connection target members. Since the use of the conductive particles according to the present invention enables mounting at lower pressures, the conductive particles are preferably used for conductive connections of flexible printed circuit boards. At least one of the first and second connection target members is preferably a flexible printed circuit board.

[0126] 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.

[0127] 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.

[0128] The following materials were prepared:

[0129] Base particles: Base particle A (divinylbenzene copolymer resin particles, Sekisui Chemical Co., Ltd. "Micropearl SP-20375", particle diameter 3.75 μm) Base particle B (divinylbenzene copolymer resin particles, Sekisui Chemical Co., Ltd. "Micropearl EX-0015", particle diameter 1.5 μm) Base particle C (divinylbenzene copolymer resin particles, Sekisui Chemical Co., Ltd. "Micropearl SP-230", particle diameter 30 μm) Base particle D (organic-inorganic hybrid particles, particle diameter 3.75 μm)

[0130] (Example 1) (1) Preparation of conductive particles 10 parts by weight of base particles A were dispersed in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution using an ultrasonic disperser, and then the solution was filtered to extract base particles A. Next, base particles A were added to 100 parts by weight of a 1% by weight solution of dimethylamine borane to activate the surfaces of base particles A. The surface-activated base particles A were thoroughly washed with water, and then added to 500 parts by weight of distilled water and dispersed to obtain a suspension (1A).

[0131] Also, a nickel plating solution (2A) (pH 10) containing 150 g / L of nickel sulfate, 70 g / L of sodium citrate, 30 g / L of boric acid, 10 g / L of dimethylamine borane, and 1 g / L of polyethylene glycol (weight average molecular weight 1000) was prepared.

[0132] While stirring the suspension (1A) at 60° C., the nickel plating solution (2A) was gradually added dropwise to perform electroless pure nickel plating. Thereafter, the mixture was stirred until the pH stabilized, and it was confirmed that hydrogen bubbling had ceased, yielding a suspension (3A) after electroless nickel plating.

[0133] The suspension (3A) was then filtered to remove the particles, which were then washed with water and dried to obtain conductive particles having a conductive layer (thickness 150 nm) with protrusions formed on the outer surface. These conductive particles are conductive particles that do not have a core material inside the protrusions.

[0134] (2) Preparation of conductive material (anisotropic conductive paste) 7 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 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).

[0135] (3) Fabrication of Connection Structure A printed circuit board was prepared on the top surface of which was formed an Au electrode pattern (first electrode, electrode: Ni / Au thin film on Cu) with an L / S of 200 μm / 200 μm. Also, a flexible printed circuit board was prepared on the bottom surface of which was formed an Au electrode pattern (second electrode, electrode: Ni / Au thin film on Cu) with an L / S of 200 μm / 200 μm.

[0136] The anisotropic conductive paste thus obtained was applied to the printed circuit board to a thickness of 30 μm to form an anisotropic conductive paste layer. Next, the flexible printed circuit board was laminated on the anisotropic conductive paste layer so that the electrodes faced each other. Thereafter, a pressure heating head was placed on the upper surface of the flexible printed circuit board while adjusting the temperature of the head so that the temperature of the anisotropic conductive paste layer was 100°C, and a pressure of 40 MPa was applied to cure the anisotropic conductive paste layer at 100°C, thereby obtaining a connection structure.

[0137] (Example 2) The outer surfaces of the conductive particles of Example 1 were gold-plated to form a second conductive layer (thickness 30 nm) on the outer surface of the conductive layer (first conductive layer). A conductive material and a connection structure were obtained in the same manner as in Example 1, except that the obtained conductive particles were used.

[0138] (Example 3) The outer surfaces of the conductive particles of Example 1 were plated with palladium to form a second conductive layer (thickness 30 nm) on the outer surface of the conductive layer (first conductive layer). A conductive material and a connection structure were obtained in the same manner as in Example 1, except that the obtained conductive particles were used.

[0139] Example 4 Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that base particle A was changed to base particle B.

[0140] Example 5 Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that base particle A was changed to base particle C.

[0141] Example 6 Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that the nickel plating solution (2A) was changed to a nickel plating solution (pH 10) containing 150 g / L of nickel sulfate, 70 g / L of sodium citrate, 30 g / L of boric acid, 10 g / L of dimethylamine borane, and 0.1 g / L of polyethylene glycol (weight average molecular weight 1000).

[0142] Example 7 Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that base particle A was changed to base particle D.

[0143] Example 8 Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that the nickel plating solution (2A) was changed to a nickel plating solution (pH 10) containing 150 g / L of nickel sulfate, 70 g / L of sodium citrate, 30 g / L of boric acid, 30 g / L of sodium hypophosphite, and 10 g / L of polyethylene glycol (weight average molecular weight 1000).

[0144] Example 9: A first conductive layer-forming nickel plating solution (1B) containing 150 g / L of nickel sulfate, 70 g / L of sodium citrate, 30 g / L of boric acid, and 30 g / L of sodium hypophosphite was prepared. Furthermore, a second conductive layer-forming nickel plating solution (pH 10) (2B) containing 150 g / L of nickel sulfate, 70 g / L of sodium citrate, 30 g / L of boric acid, 10 g / L of dimethylamine borane, and 1 g / L of polyethylene glycol (weight-average molecular weight 1000) was prepared. While stirring the suspension (1A) of Example 1 at 60°C, the first conductive layer-forming nickel plating solution (1B) was gradually added dropwise to perform electroless nickel plating. The mixture was then stirred until the pH stabilized at 7.0, and the cessation of hydrogen bubbling was confirmed. Conductive particles having a first conductive layer (50 nm thick) without a crystal structure containing grain boundaries and without protrusions on the outer surface were obtained, as well as a suspension (3B) containing the conductive particles after electroless nickel plating. While stirring the suspension (3B) at 60 ° C., the nickel plating solution (2B) for forming the second conductive layer was gradually added dropwise to perform electroless nickel plating, resulting in conductive particles having a second conductive layer (150 nm thick) formed on the outer surface of the first conductive layer, which has a crystal structure containing grain boundaries and has protrusions on the outer surface. A conductive material and a connection structure were obtained in the same manner as in Example 1, except that the obtained conductive particles were used.

[0145] Example 10 (1) Preparation of Insulating Particles The following monomer composition was placed in a 1000 mL separable flask equipped with a four-neck separable cover, a stirring blade, a three-way stopcock, a condenser, and a temperature probe. Distilled water was then added so that the solids content of the following monomer composition was 10 wt %. The mixture was stirred at 200 rpm and polymerized at 60°C for 24 hours under a nitrogen atmosphere. The monomer composition contained 360 mmol of methyl methacrylate, 45 mmol of glycidyl methacrylate, 20 mmol of parastyryldiethylphosphine, 13 mmol of ethylene glycol dimethacrylate, 0.5 mmol of polyvinylpyrrolidone, and 1 mmol of 2,2'-azobis{2-[N-(2-carboxyethyl)amidino]propane}. After the reaction was completed, the mixture was freeze-dried to obtain insulating particles (particle diameter 360 nm) having phosphorus atoms derived from parastyryldiethylphosphine on their surfaces.

[0146] (2) Preparation of Conductive Particles with Insulating Particles The insulating particles obtained in (1) above were dispersed in distilled water under ultrasonic irradiation to obtain a 10 wt% aqueous dispersion of insulating particles. 10 g of the conductive particles obtained in Example 8 were dispersed in 500 mL of distilled water, and 1 g of the 10 wt% aqueous dispersion of insulating particles was added and stirred at room temperature for 8 hours. After filtering through a 3 μm mesh filter, the mixture was further washed with methanol and dried to obtain conductive particles with insulating particles. A conductive material and a connection structure were obtained in the same manner as in Example 1, except that the obtained conductive particles with insulating particles were used.

[0147] Comparative Example 1 Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that no protrusions were formed on the outer surface of the conductive layer.

[0148] Comparative Example 2 One part by weight of metallic nickel slurry (average particle diameter 150 nm) was added over 3 minutes to the suspension (1A) of Example 1 to obtain a particle mixture suspension (1C) containing base particles A to which a core material was attached. A nickel plating solution (pH 7.0) containing 150 g / L of nickel sulfate, 70 g / L of sodium citrate, 30 g / L of boric acid, and 10 g / L of dimethylamine borane was prepared.

[0149] While stirring the suspension (1C) at 60° C., the nickel plating solution was gradually added dropwise to perform electroless pure nickel plating. Thereafter, stirring was continued until the pH stabilized at 7.0, and it was confirmed that hydrogen bubbling had ceased, yielding a suspension (2C) after electroless pure nickel plating.

[0150] The suspension (2C) was then filtered to remove the particles, which were then washed with water and dried to obtain conductive particles having a conductive layer (thickness 150 nm) with protrusions formed on the outer surface. These conductive particles have a core material inside the protrusions.

[0151] Comparative Example 3: A nickel plating solution (1D) for forming a conductive layer containing 150 g / L of nickel sulfate, 30 g / L of sodium tartrate, and 10 g / L of sodium hypophosphite, and a plating solution (2D) for forming protrusions containing 150 g / L of nickel sulfate, 150 g / L of sodium hypophosphite, and 80 g / L of sodium hydroxide were prepared. While stirring the suspension (1A) of Example 1 at 60°C, the nickel plating solution (1D) for forming a conductive layer was gradually added dropwise to perform electroless nickel plating, forming a conductive layer (thickness 150 nm) on the outer surface of the base particle. At the same time, autolysis of the nickel plating solution (1D) for forming a conductive layer was initiated. The plating solution (2D) for forming protrusions was then gradually added dropwise to form protrusions on the outer surface of the conductive layer. The mixture was stirred until the pH stabilized, and the cessation of hydrogen bubbling was confirmed, yielding a suspension (3D) after electroless nickel plating. The suspension (3D) was then filtered to extract the particles, which were then washed with water and dried to obtain conductive particles having a conductive layer (thickness 150 nm) formed on their outer surfaces with protrusions formed by decomposition of the plating solution. A conductive material and a connection structure were obtained in the same manner as in Example 1, except that the obtained conductive particles were used.

[0152] (Evaluation) (1) Particle diameter of conductive particles, thickness of first conductive layer and second conductive layer, and height of protrusions For the obtained conductive particles, the particle diameter of the conductive particles, the thickness of the first conductive layer and second conductive layer, and the height of the protrusions were measured using the methods described above, and the average was calculated.

[0153] (2) Presence or absence of conductive layer X and inclination angle θ of grain boundary with base of protrusion as one end of grain boundary The obtained conductive particles were observed using a transmission electron microscope (TEM) for the presence or absence of a conductive layer (conductive layer X) having a crystalline structure including grain boundaries and having protrusions on the outer surface. Furthermore, the inclination angle θ was measured by the above-described method for three grain boundaries with the base of the protrusion of the conductive layer X as one end of the grain boundary, and the average was calculated. In Examples 2 and 3, the first conductive layer was a conductive layer (conductive layer X) having a crystalline structure including grain boundaries and having protrusions on the outer surface. In Example 9, the second conductive layer was a conductive layer (conductive layer X) having a crystalline structure including grain boundaries and having protrusions on the outer surface.

[0154] (3) Protrusion Formation Rate For the obtained conductive particles, the outer surface area of ​​the portion having protrusions (protrusion formation rate) out of 100% of the outer surface area of ​​the conductive layer X (first conductive layer in Comparative Examples 2 and 3) was determined by the method described above.

[0155] (4) 20% K Value The 20% K value of the conductive particles was measured at 25° C. by the method described above using a microcompression tester (Fisherscope H-100 manufactured by Fisher).

[0156] (5) Cracks in the Conductive Layers The connection structures obtained were evaluated using a transmission electron microscope (TEM) to determine whether or not cracks were present in the conductive layers (first conductive layer and second conductive layer) of the conductive particles. Cracks in the conductive layers were evaluated according to the following criteria.

[0157] [Evaluation criteria for cracks in the conductive layer] ◯: The proportion of the number of conductive particles in which cracks occurred in the conductive layer is less than 30%. ◯: The proportion of the number of conductive particles in which cracks occurred in the conductive layer is 30% or more and less than 60%. ×: The proportion of the number of conductive particles in which cracks occurred in the conductive layer is 60% or more.

[0158] (6) Connection reliability The connection resistance between the upper and lower electrodes of the 20 connection structures obtained was measured using a four-terminal method. The average value of the connection resistance was calculated. Note that, based on the relationship voltage = current x resistance, the connection resistance can be determined by measuring the voltage when a constant current is passed. The connection reliability was evaluated according to the following criteria.

[0159] [Criteria for determining connection reliability] ○○: Average connection resistance is 2.0Ω or less ○: Average connection resistance is greater than 2.0Ω and less than 5.0Ω △: Average connection resistance is greater than 5.0Ω and less than 10.0Ω ×: Average connection resistance is greater than 10.0Ω

[0160] The results are shown in Tables 1 to 3 below.

[0161]

[0162]

[0163]

[0164] FIG. 6 is a transmission electron microscope photograph of the cross section of the conductive particle of Example 1. FIG. 7 is a transmission electron microscope photograph of the cross section of the conductive particle of Comparative Example 2. FIG. 8 is a transmission electron microscope photograph of the cross section of the conductive particle of Comparative Example 3. As shown in FIG. 6 , in the conductive particles of Examples 1 to 10, the grain boundaries in the conductive layer were oriented in the thickness direction of the conductive layer, and the grain boundaries present in the protrusions of the conductive layer were oriented at an angle with respect to a line connecting one end of the grain boundary and the center of the conductive particle, such that the other end of the grain boundary was located inside the protrusion relative to the intersection of the line connecting the inner surface of the conductive layer with the one end of the grain boundary. As shown in FIG. 7 , in the conductive particle of Comparative Example 2, the grain boundaries in the conductive layer were oriented along the boundary between the core material and the conductive layer. As shown in FIG. 8 , in the conductive particle of Comparative Example 3, the grain boundaries in the conductive layer were not uniform in orientation, and voids were generated within the conductive layer and the protrusions.

[0165] REFERENCE SIGNS LIST 1...Conductive particle 2...Base particle 3...Conductive layer 3a...Protrusion 11...Conductive particle 13...Conductive layer 13A...First conductive layer 13B...Second conductive layer 13a, 13Aa, 13Ba...Protrusion 21...Conductive particle 23...Conductive layer 23a...Protrusion 24...Insulating material 51...Connection structure 52...First connection target member 52a...First electrode 53...Second connection target member 53a...Second electrode 54...Connection portion

Claims

1. Substrate particles and It comprises a conductive layer having a crystalline structure including grain boundaries and having protrusions on its outer surface, The conductive layer is disposed on the outer surface of the substrate particles, Conductive particles in which the grain boundaries in the conductive layer are oriented in the thickness direction of the conductive layer.

2. The conductive particle according to claim 1, wherein the inner surface of the projection is not provided with a core material.

3. The grain boundary present in the portion of the conductive layer having the protrusion has one end located on the outer surface side of the conductive layer and the other end located on the inner surface side of the conductive layer. The conductive particle according to claim 1 or 2, wherein the grain boundary is oriented inclined with respect to a straight line such that the other end of the grain boundary is located inside the protrusion, below the intersection of the straight line connecting the one end of the grain boundary and the center of the conductive particle and the inner surface of the conductive layer.

4. The grain boundary present in the portion of the conductive layer having the protrusion includes grain boundary A, The grain boundary A has one end located on the outer surface side of the conductive layer and the other end located on the inner surface side of the conductive layer, and the base of the projection is the one end of the grain boundary A. The grain boundary A is oriented inclined with respect to a straight line such that the other end of the grain boundary A is located inside the protrusion, beyond the intersection point of the straight line connecting the one end of the grain boundary A and the center of the conductive particle, and the inner surface of the conductive layer. The conductive particle according to claim 1 or 2, wherein the angle of inclination between the grain boundary A and the straight line connecting one end of the grain boundary A and the center of the conductive particle is 3° or more.

5. The grain boundary present in the portion of the conductive layer having the protrusion includes grain boundary A, The grain boundary A has one end located on the outer surface side of the conductive layer and the other end located on the inner surface side of the conductive layer, and the base of the projection is the one end of the grain boundary A. The grain boundary A is oriented inclined with respect to a straight line such that the other end of the grain boundary A is located inside the protrusion, beyond the intersection point of the straight line connecting the one end of the grain boundary A and the center of the conductive particle, and the inner surface of the conductive layer. The conductive particle according to claim 1 or 2, wherein the angle of inclination between the grain boundary A and the straight line connecting one end of the grain boundary A and the center of the conductive particle is 10° or more.

6. The average height of the protrusions is 10 nm or more, The grain boundary present in the portion of the conductive layer having the protrusion includes grain boundary A. The grain boundary A has one end located on the outer surface side of the conductive layer and the other end located on the inner surface side of the conductive layer, and the base of the projection is the one end of the grain boundary A. The grain boundary A is oriented inclined with respect to a straight line such that the other end of the grain boundary A is located inside the protrusion, beyond the intersection point of the straight line connecting the one end of the grain boundary A and the center of the conductive particle, and the inner surface of the conductive layer. The conductive particle according to claim 1 or 2, wherein the angle of inclination between the grain boundary A and the straight line connecting one end of the grain boundary A and the center of the conductive particle is 3° or more.

7. The average height of the protrusions is 30 nm or more, The grain boundary present in the portion of the conductive layer having the protrusion includes grain boundary A. The grain boundary A has one end located on the outer surface side of the conductive layer and the other end located on the inner surface side of the conductive layer, and the base of the projection is the one end of the grain boundary A. The grain boundary A is oriented inclined with respect to a straight line such that the other end of the grain boundary A is located inside the protrusion, beyond the intersection point of the straight line connecting the one end of the grain boundary A and the center of the conductive particle, and the inner surface of the conductive layer. The conductive particle according to claim 1 or 2, wherein the angle of inclination between the grain boundary A and the straight line connecting one end of the grain boundary A and the center of the conductive particle is 3° or more.

8. The average height of the protrusions is 30 nm or more, Of the total outer surface area of ​​the conductive layer, the outer surface area of ​​the portion with the protrusion is 3% or more and 29% or less. The grain boundary present in the portion of the conductive layer having the protrusion includes grain boundary A. The grain boundary A has one end located on the outer surface side of the conductive layer and the other end located on the inner surface side of the conductive layer, and the base of the projection is the one end of the grain boundary A. The grain boundary A is oriented inclined with respect to a straight line such that the other end of the grain boundary A is located inside the protrusion, beyond the intersection point of the straight line connecting the one end of the grain boundary A and the center of the conductive particle, and the inner surface of the conductive layer. The conductive particle according to claim 1 or 2, wherein the angle of inclination between the grain boundary A and the straight line connecting one end of the grain boundary A and the center of the conductive particle is 3° or more.

9. The average height of the protrusions is 30 nm or more, Of the total outer surface area of ​​the conductive layer, the outer surface area of ​​the portion with the protrusion is 3% or more and 29% or less. The grain boundary present in the portion of the conductive layer having the protrusion includes grain boundary A. The grain boundary A has one end located on the outer surface side of the conductive layer and the other end located on the inner surface side of the conductive layer, and the base of the projection is the one end of the grain boundary A. The grain boundary A is oriented inclined with respect to a straight line such that the other end of the grain boundary A is located inside the protrusion, beyond the intersection point of the straight line connecting the one end of the grain boundary A and the center of the conductive particle, and the inner surface of the conductive layer. The conductive particle according to claim 1 or 2, wherein the angle of inclination between the grain boundary A and the straight line connecting one end of the grain boundary A and the center of the conductive particle is 10° or more.

10. The conductive particle according to claim 1 or 2, wherein the outer surface area of ​​the portion having the protrusions is 3% or more of the outer surface area of ​​100% of the outer surface area of ​​the conductive layer.

11. The compressive modulus when compressed by 20% at 25°C is 1000 N / mm². ２ More than 30000N / mm ２ The conductive particles according to claim 1 or 2, which are as follows:

12. The conductive particle according to claim 1 or 2, wherein the conductive layer comprises tin, nickel, copper, palladium, or gold.

13. The conductive particle according to claim 1 or 2, comprising an insulating material disposed on the outer surface of the conductive layer.

14. A method for producing conductive particles according to claim 1 or 2, The process includes forming the conductive layer on the outer surface of the substrate particles, A method for producing conductive particles, comprising forming the protrusions on the outer surface of the base particles without arranging a core material on the outer surface of the base particles.

15. A method for producing conductive particles according to claim 14, wherein the protrusions are formed without causing decomposition of the plating solution.

16. A conductive material comprising conductive particles according to claim 1 or 2 and a binder resin.

17. A first connection target member having a first electrode on its surface, A second connection target member having a second electrode on its surface, The device comprises a connecting portion that connects the first member to be connected and the second member to be connected, The material of the connecting portion includes the conductive particles described in claim 1 or 2. A connecting structure in which the first electrode and the second electrode are electrically connected by the conductive particles.