Conductive particles, conductive materials and connecting structures

Abstract

The present invention provides a conductive particle that can improve the reliability of conduction when electrically connecting electrodes. The conductive particles of the present invention have a substrate particle and a conductive portion disposed on the surface of the substrate particle, and satisfy either configuration A or configuration B below. Configuration A: The conductive portion contains indium or bismuth, and the conductive portion melts when the conductive particles are heated at 160°C for 1 minute in an atmospheric atmosphere. Configuration B: The conductive portion contains three or more metals with different melting points, and the conductive portion melts when the conductive particles are heated at 200°C for 1 minute in an atmospheric atmosphere.

Description

[Technical Field]

[0001] This invention relates to a conductive particle comprising a substrate particle and a conductive portion disposed on the surface of the substrate particle. Furthermore, this invention relates to a conductive material and a connecting structure using the aforementioned conductive particle. [Previous Technology]

[0002] It is well known that there are anisotropic conductive materials such as anisotropic conductive paste and anisotropic conductive film. In such anisotropic conductive materials, conductive particles are dispersed in adhesive resin.

[0003] The above-mentioned anisotropic conductive materials are used to obtain various connection structures. Examples of connections using the above-mentioned anisotropic conductive materials include: connection between a flexible printed circuit board and a glass substrate (FOG (Film on Glass)), connection between a semiconductor wafer and a flexible printed circuit board (COF (Chip on Film)), connection between a semiconductor wafer and a glass substrate (COG (Chip on Glass)), and connection between a flexible printed circuit board and a glass epoxy resin substrate (FOB (Film on Board)).

[0004] In recent years, there has been continuous progress in miniaturization and weight reduction of devices using connecting structures. Along with this, the conductive particles used in the connecting structures require high conductivity properties such as high capacity and low resistivity. Tin particles are sometimes used as these conductive particles, which can improve conductivity by bonding with electrodes through metal melting.

[0005] Patent Document 1 below discloses a conductive particle comprising: substrate microparticles and a metal coating layer covering the substrate microparticles. In the conductive particle, the metal coating layer comprises an inner copper plating layer and an outer tin plating layer, both electrolessly plated. In the conductive particle, the tin plating layer is formed by an electroless tin plating bath containing a reducing agent. In the conductive particle, the thickness of the copper plating layer is 0.040 μm or more, the thickness of the tin plating layer is 0.050 μm or more, and the combined thickness of the copper plating layer and the tin plating layer is 0.090 μm or more and 0.180 μm or less. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2011-134480 [Summary of the Invention]

[0007] [The problem the invention aims to solve]

[0008] In recent years, in order to reduce the burden on substrates, etc., packaging is sometimes carried out in a low temperature environment below 200°C.

[0009] However, the conductive particles described in Patent Document 1, namely conductive particles with a two-layer structure and an outer tin layer, have the following problems: tin metal melting is not easy to occur under packaging conditions that do not reach 200°C, and the conductivity reliability cannot be sufficiently improved when the electrodes are electrically connected (the connection resistance cannot be sufficiently reduced).

[0010] The object of the present invention is to provide a conductive particle that improves the reliability of conduction when electrically connecting electrodes. Furthermore, the object of the present invention is to provide a conductive material and a connection structure using the aforementioned conductive particle. [Technical Means for Solving the Problem]

[0011] According to a general form of the present invention, a conductive particle is provided, which has a substrate particle and a conductive portion disposed on the surface of the substrate particle, and satisfies the following configuration A or the following configuration B.

[0012] Composition A: The conductive part contains indium or bismuth. When the conductive particles are heated at 160°C for 1 minute in an atmospheric environment, the conductive part melts.

[0013] Composition B: The conductive part contains three or more metals with different melting points. When the conductive particles are heated at 200°C in an atmospheric environment for 1 minute, the conductive part melts.

[0014] According to a specific state of the conductive particles of the present invention, the conductive part contains indium or bismuth, and when the conductive particles are heated at 160°C for 1 minute in an atmospheric atmosphere, the conductive part melts.

[0015] According to a specific state of the conductive particles of the present invention, the conductive part contains indium, and when the conductive particles are heated at 160°C for 1 minute in an atmospheric atmosphere, the conductive part melts.

[0016] According to a specific state of the conductive particles of the present invention, the conductive part comprises three or more metals with different melting points, and when the conductive particles are heated in an atmospheric environment at 200°C for 1 minute, the conductive part melts.

[0017] According to a specific state of the conductive particles of the present invention, the conductive part has a conductive layer with a melting point of 200°C or less, and the content of the conductive layer with a melting point of 200°C or less in 100% by weight of the conductive part is 10% by weight or more.

[0018] In a specific state of the conductive particles of the present invention, the conductive portion has a layer containing copper or nickel, and the substrate particles are in contact with the layer containing copper or nickel.

[0019] In a specific state of the conductive particles of the present invention, the conductive portion contains tin, and the tin content in 100% by weight of the conductive portion is 2% by weight or more.

[0020] In a specific state of the conductive particles of the present invention, the conductive portion comprises bismuth.

[0021] In a specific state of the conductive particles of the present invention, the conductive part is a conductive layer of two or more layers, and the conductive layer of two or more layers is deposited in such a way that the melting point of the conductive layer gradually increases from the outer surface of the conductive part toward the inner surface.

[0022] In a specific state of the conductive particles of the present invention, the conductive portion is a conductive layer of 3 or more layers. The conductive portion has a conductive layer P, a conductive layer Q, and a conductive layer R in sequence from the outer surface of the conductive portion toward the inner side of the thickness direction of the conductive portion. The conductive layer P is the outer surface layer of the conductive portion. The conductive layer P, the conductive layer Q, and the conductive layer R are continuously stacked. The conductive portion has no conductive layer or has one or more conductive layers inside the conductive layer R.

[0023] In a specific state of the conductive particles of the present invention, the diffusion coefficient of the conductive layer P relative to the conductive layer Q at 160°C is 1.0×10-20m2 / s or more.

[0024] In a specific state of the conductive particles of the present invention, the diffusion coefficient of the conductive layer R relative to the conductive layer Q at 160°C is less than 1.0×10-25m2 / s.

[0025] In a specific state of the conductive particles of the present invention, the materials of the conductive layer P and the conductive layer Q contain solder components.

[0026] In a specific state of the conductive particles of the present invention, the conductive layer P is an indium layer containing indium, the conductive layer Q is a tin layer containing tin, and the conductive layer R is a nickel layer containing nickel.

[0027] When measuring the X-ray diffraction spectrum of the conductive part in a specific state sample of the conductive particle of the present invention, peaks are present in the region of 32° to 34° and in the region of 55.5° to 57.5°.

[0028] In a specific state of the conductive particles of the present invention, the outer surface of the conductive part is surface treated with flux.

[0029] In a specific state of the conductive particles of the present invention, the particle size of the substrate particles is 0.5 μm or more and 100 μm or less.

[0030] According to a general aspect of the present invention, a conductive material is provided, comprising the above-mentioned conductive particles and an adhesive resin.

[0031] According to a general embodiment of the present invention, a connection structure is provided, comprising: a first connection member having a first electrode on its surface; a second connection member having a second electrode on its surface; and a connection portion connecting the first connection member and the second connection member, wherein the material of the connection portion comprises the conductive particles, and the first electrode and the second electrode are electrically connected by means of the conductive particles. [Effects of the Invention]

[0032] The conductive particles of the present invention have a substrate particle and a conductive portion disposed on the surface of the substrate particle. The conductive particles of the present invention satisfy either configuration A or configuration B below. Configuration A: The conductive portion contains indium or bismuth, and the conductive portion melts when the conductive particles are heated at 160°C for 1 minute in an atmospheric atmosphere. Configuration B: The conductive portion contains three or more metals with different melting points, and the conductive portion melts when the conductive particles are heated at 200°C for 1 minute in an atmospheric atmosphere. Because the conductive particles of the present invention have the above configuration, the conductivity reliability can be improved when electrical connections are made between electrodes.

Implementation Method

[0034] The details of the present invention will be described below.

[0035] (Conductive Particles) The conductive particles of the present invention have a substrate particle and a conductive portion disposed on the surface of the substrate particle. The conductive particles of the present invention satisfy either configuration A or configuration B.

[0036] Composition A: The conductive part contains indium or bismuth. When the conductive particles are heated at 160°C in an atmospheric environment for 1 minute, the conductive part melts.

[0037] Composition B: The conductive part contains three or more metals with different melting points. When the conductive particles are heated at 200°C in an atmospheric environment for 1 minute, the conductive part melts.

[0038] The conductive particles of the present invention can satisfy configuration A, configuration B, or both configuration A and configuration B. In configuration A, the conductive portion of the conductive particles of the present invention can contain indium, bismuth, or both indium and bismuth.

[0039] Specifically, the conductive particles of the present invention are conductive particles A or conductive particles B.

[0040] Regarding the conductive particle A having the above-described configuration A: The conductive particle of the present invention has a substrate particle and a conductive portion disposed on the surface of the substrate particle. In the conductive particle of the present invention, the conductive portion comprises indium or bismuth. In the conductive particle of the present invention, when the conductive particle is heated at 160°C for 1 minute in an atmospheric atmosphere, the conductive portion melts. Because the conductive particle of the present invention (hereinafter, sometimes referred to as "conductive particle A") has the above-described configuration, the conductive portion melts when electrodes are electrically connected, thereby improving the reliability of conduction. That is, the reliability of conduction between the upper and lower electrodes to be connected can be improved. Furthermore, because the conductive portion melts rapidly, the reliability of insulation between electrodes in the lateral direction that cannot be connected can also be ensured.

[0041] Regarding the conductive particle B having the above-described configuration B: The conductive particle of the present invention has a substrate particle and a conductive portion disposed on the surface of the substrate particle. In the conductive particle of the present invention, the conductive portion comprises three or more metals with different melting points. In the conductive particle of the present invention, when the conductive particle is heated at 200°C for 1 minute in an atmospheric atmosphere, the conductive portion melts. Because the conductive particle of the present invention (hereinafter, sometimes referred to as "conductive particle B") has the above-described configuration, the conductive portion melts when the electrodes are electrically connected, thereby improving the reliability of conduction. That is, the reliability of conduction between upper and lower electrodes can be improved. Furthermore, because the conductive portion melts rapidly, the reliability of insulation between electrodes in the lateral direction that cannot be connected can also be ensured.

[0042] Furthermore, in this invention, "conductive part melting" means that at least the surface portion of the conductive part is melted.

[0043] From the viewpoint of effectively exerting the effects of the present invention, the above-mentioned configuration A is preferably the following configuration Aa.

[0044] Composition Aa: The conductive part contains indium, and when the conductive particles are heated at 160°C in an atmospheric atmosphere for 1 minute, the conductive part melts.

[0045] The above-described configuration A can also be the following configuration Ab. Even if the above-described conductive part does not contain bismuth conductive particles, the effects of the present invention can still be achieved by having the overall configuration of the present invention.

[0046] Composition Ab: The conductive part contains indium, the conductive part does not contain bismuth, and when the conductive particles are heated at 160°C for 1 minute in an atmospheric atmosphere, the conductive part melts.

[0047] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0048] FIG1 is a cross-sectional view of the conductive particles of the first embodiment of the present invention.

[0049] The conductive particle 1 shown in FIG1 has a substrate particle 2 and a conductive portion 3 disposed on the surface of the substrate particle 2. The conductive portion 3 covers the surface of the substrate particle 2. The conductive particle 1 is a coated particle formed by covering the surface of the substrate particle 2 with the conductive portion 3.

[0050] In the conductive particle 1, the conductive part 3 is a single-layer conductive layer.

[0051] The conductive part 3 may also contain indium or bismuth in the conductive particle 1. In this case, it is preferable that the conductive part 3 melts when the conductive particle 1 is heated at 160°C for 1 minute in an atmospheric atmosphere.

[0052] In the conductive particles 1, the conductive part 3 may also contain three or more metals with different melting points. In this case, it is preferable that the conductive part 3 melts when the conductive particles 1 are heated at 200°C for 1 minute in an atmospheric atmosphere.

[0053] FIG2 is a cross-sectional view of the conductive particles of the second embodiment of the present invention.

[0054] The conductive particle 21 shown in FIG2 has a substrate particle 2 and a conductive portion 23 disposed on the surface of the substrate particle 2. The conductive portion 23 covers the surface of the substrate particle 2. The conductive particle 21 is a coated particle whose surface of the substrate particle 2 is covered by the conductive portion 23.

[0055] In the conductive particle 21, the conductive portion 23 is a conductive layer with a three-layer structure. The conductive portion 23 has: a first conductive portion 23A, a second conductive portion 23B, and a third conductive portion 23C. The first conductive portion 23A is disposed on the surface of the substrate particle 2. The first conductive portion 23A is in contact with the substrate particle 2. The first conductive portion 23A is disposed between the substrate particle 2 and the second conductive portion 23B. The second conductive portion 23B is disposed on the surface of the first conductive portion 23A. The second conductive portion 23B is in contact with the first conductive portion 23A. The second conductive portion 23B is disposed between the first conductive portion 23A and the third conductive portion 23C. The third conductive portion 23C is disposed on the surface of the second conductive portion 23B. The third conductive portion 23C is in contact with the second conductive portion 23B. The third conductive portion 23C is the outermost conductive portion of the conductive particle 21.

[0056] The conductive portion 23 in the conductive particle 21 may also contain indium or bismuth. The conductive particle 21 may contain indium or bismuth in the first conductive portion 23A, the second conductive portion 23B, or the third conductive portion 23C. When the conductive portion 23 contains indium or bismuth, it is preferable that the conductive portion 23 melts when the conductive particle 21 is heated at 160°C in an atmospheric atmosphere for 1 minute.

[0057] The conductive part 23 may also contain three or more metals with different melting points in the conductive particles 21. In this case, it is preferable that the conductive part 3 melts when the conductive particles 21 are heated at 200°C for 1 minute in an atmospheric atmosphere.

[0058] Figure 3 is a cross-sectional view of the conductive particles according to the third embodiment of the present invention.

[0059] The conductive particle 31 shown in FIG3 has: a substrate particle 2, a conductive part 33 disposed on the surface of the substrate particle 2, a plurality of core materials 34, and a plurality of insulating materials 35.

[0060] In the conductive particle 31, the conductive portion 33 is a single-layer conductive layer. In the aforementioned conductive particle, the conductive portion may cover the entire surface of the substrate particle, or it may cover only a portion of the surface of the substrate particle. In the aforementioned conductive particle, the conductive portion may be a single-layer conductive layer, or it may be a multilayer conductive layer containing two or more layers.

[0061] The conductive particles 31 (especially the conductive portions 33) have a plurality of protrusions 33a on their surface. A plurality of core materials 34 are disposed on the surface of the substrate particles 2. The plurality of core materials 34 are embedded within the conductive portions 33. The core materials 34 are disposed inside the protrusions 33a. The conductive portions 33 are covered by the plurality of core materials 34. The outer surface of the conductive portions 33 is raised due to the plurality of core materials 34, thereby forming the protrusions 33a.

[0062] The conductive particle 31 has an insulating material 35 disposed on the outer surface of the conductive portion 33. At least a portion of the outer surface of the conductive portion 33 is covered by the insulating material 35. The insulating material 35 is formed of an insulating material and is an insulating particle. As described above, the conductive particles of the present invention may also have an insulating material disposed on the outer surface of the conductive portion. However, the conductive particles of the present invention may not necessarily have an insulating material.

[0063] The conductive part 33 in the conductive particle 31 may also contain indium or bismuth. In this case, it is preferable that the conductive part 33 melts when the conductive particle 31 is heated at 160°C for 1 minute in an atmospheric atmosphere.

[0064] The conductive particles 31 may also contain three or more metals with different melting points. In this case, it is preferable that the conductive particles 31 are heated at 200°C for 1 minute in an atmospheric atmosphere until the conductive parts 33 melt.

[0065] The following will explain other details about the conductive particles.

[0066] Furthermore, in this specification, "(meth)acrylate" means acrylate and methacrylate. "(meth)acrylic acid" means acrylic acid and methacrylic acid. "(meth)acryl" means acrylonitrile and methacryl.

[0067] The particle size of the aforementioned conductive particles is preferably 0.8 μm or more, more preferably 3 μm or more, further preferably 5 μm or more, and preferably 105 μm or less, more preferably 50 μm or less, and further preferably 40 μm or less. If the particle size of the aforementioned conductive particles is above the aforementioned lower limit and below the aforementioned upper limit, the conductivity reliability and insulation reliability can be improved.

[0068] Preferably, the particle size of the conductive particles is the average particle size, which represents the number average particle size. The particle size of the conductive particles can be determined, for example, by observing any 50 conductive particles using an electron microscope or an optical microscope and calculating the average particle size of each conductive particle; or by performing laser diffraction particle size distribution measurement.

[0069] From the viewpoint of further effectively exerting the effects of the present invention, the coefficient of variation (CV value) of the particle size of the above-mentioned conductive particles is preferably 10% or less, and more preferably 5% or less.

[0070] The above coefficient of variation (CV value) can be determined in the following manner.

[0071] CV value (%) = (ρ / Dn) × 100 ρ: Standard deviation of the particle size of conductive particles Dn: Average particle size of conductive particles

[0072] The shape of the conductive particles is not particularly limited. The conductive particles may be spherical, or any other shape, or may be flat, etc.

[0073] The above-mentioned conductive particles are dispersed in the adhesive resin, which is suitable for obtaining conductive materials.

[0074] <Substrate Particles> Examples of the aforementioned substrate particles include: resin particles, inorganic particles other than metal particles, organic-inorganic hybrid particles, and metal particles. Preferably, the substrate particles are substrate particles other than metal particles, and more preferably, resin particles, inorganic particles other than metal particles, or organic-inorganic hybrid particles. The aforementioned substrate particles may also be core-shell particles having a core and a shell disposed on the surface of the core. The core may also be an organic core, and the shell may also be an inorganic shell.

[0075] Examples of materials for the aforementioned resin particles include: polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene, etc.; 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, polyurethane, polyphenylene ether, polyacetal, polyimide, polyamide-imide, polyetheretherketone, polyether ether, and divinylbenzene polymers, etc. The aforementioned divinylbenzene polymers may also be divinylbenzene copolymers. Examples of the aforementioned divinylbenzene copolymers include: divinylbenzene-styrene copolymers and divinylbenzene-(meth)acrylate copolymers, etc. The resin particles are preferably made of a polymer formed by polymerizing one or more polymeric monomers having ethylene unsaturated groups, because the hardness of the resin particles can be easily controlled within a suitable range.

[0076] When the above-mentioned resin particles are obtained by polymerizing a polymerizable monomer having an ethylene unsaturated group, examples of the polymerizable monomer having an ethylene unsaturated group include non-crosslinked monomers and crosslinked monomers.

[0077] Examples of the above-mentioned non-crosslinking monomers include: styrene and α-methylstyrene, etc.; carboxyl-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; alkyl methacrylates such as (meth)acrylate, (meth)acrylate, (meth)acrylate, (meth)acrylate, (meth)acrylate, (meth)acrylate, (meth)acrylate, 2-ethylhexyl methacrylate, (meth)acrylate, lauryl acrylate, (meth)acrylate, cetyl acrylate, (meth)acrylate, stearyl acrylate, (meth)acrylate, (meth)acrylate, and (meth)acrylate isobutyl acrylate; (meth)acrylic acid 2-Hydroxyethyl ester, glyceryl (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate, etc., containing oxygen atoms, are meth acrylate compounds; nitrile monomers such as (meth)acrylonitrile; vinyl ether compounds such as methyl vinyl ether, ethyl vinyl ether, and propyl vinyl ether; vinyl ester compounds such as vinyl acetate, vinyl butyrate, vinyl laurate, and vinyl stearate; unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene; halogen-containing monomers such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene.

[0078] Examples of the above-mentioned crosslinking monomers 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 di(meth)acrylate, etc. The resin contains poly(meth)acrylates such as propylene glycol di(meth)acrylate, poly(1,4-butanediol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate; and silane-containing monomers such as triallyl isocyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane. From the viewpoint that flux-containing particles maintain their shape at the glass transfer temperature of the aforementioned resin particles, the aforementioned crosslinking monomers are preferably polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, or dipentaerythritol poly(meth)acrylate.

[0079] The resin particles described above can be obtained by polymerizing the polymerizable monomer having an ethylene unsaturated group using a known method. Examples of such methods include: suspension polymerization in the presence of a free radical polymerization initiator; and polymerization using non-crosslinked seed particles to swell the free radical polymerization initiator and monomer.

[0080] When the aforementioned substrate particles are inorganic particles other than metals or organic-inorganic hybrid particles, examples of inorganic materials used to form the substrate particles include: silicon dioxide, alumina, barium titanate, zirconium oxide, and carbon black. Preferably, the aforementioned inorganic materials are non-metallic. For example, particles formed from silicon dioxide can be obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form cross-linked polymer particles, followed by firing as needed. Examples of organic-inorganic hybrid particles include organic-inorganic hybrid particles formed from a cross-linked alkoxysilyl polymer and acrylic resin.

[0081] The aforementioned organic-inorganic hybrid particles are preferably core-shell type 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 aforementioned substrate particles are preferably organic-inorganic hybrid particles having an organic core and an inorganic shell disposed on the surface of the organic core.

[0082] As materials for the above-mentioned organic core, examples include the above-mentioned resin particle materials, etc.

[0083] Examples of materials for the inorganic shell include inorganic materials used as the base material particles. Silicon dioxide is a preferred material for the inorganic shell. The inorganic shell is preferably formed on the surface of the core by forming a shell-like structure from a metal alkoxide using a sol-gel method, followed by sintering the shell-like structure. Alkyl alkoxide is a preferred metal alkoxide. The inorganic shell is preferably formed from alkyl alkoxide.

[0084] When the above-mentioned substrate particles are metal particles, the metals used as materials for the metal particles can be, for example, silver, copper, nickel, silicon, gold and titanium.

[0085] The particle size of the aforementioned substrate particles is preferably 0.5 μm or more, more preferably 9.5 μm or more, and preferably 100 μm or less, more preferably 49.95 μm or less, and even more preferably 39.95 μm or less. If the particle size of the aforementioned substrate particles is above the lower limit and below the upper limit, the spacing between electrodes becomes smaller, and conductive particles with a smaller particle size can be obtained even if the thickness of the conductive portion is increased. Furthermore, when a conductive portion is formed on the surface of the substrate particles, the particles become difficult to aggregate, and conductive particles that are difficult to aggregate are formed.

[0086] The shape of the above-mentioned substrate particles is not particularly limited. The shape of the above-mentioned substrate particles may be spherical, or may be any other shape other than spherical, or may be flat, etc.

[0087] The particle size of the aforementioned substrate particles is preferably the average particle size, which represents the number average particle size. The particle size of the aforementioned substrate particles can be determined using a particle size distribution measuring device or the like. The particle size of the substrate particles is preferably determined by observing any 50 substrate particles using an electron microscope or an optical microscope and calculating the average value. When measuring the particle size of the aforementioned substrate particles in conductive particles, for example, the measurement can be performed in the following manner.

[0088] Conductive particles were added to "Technovit 4000" manufactured by Kulzer Corporation at a content of 30% by weight and dispersed to create an inspection-grade embedded resin body containing conductive particles. The conductive particles (substrate particles) dispersed near their centers in the aforementioned inspection-grade embedded resin body were cut using an ion milling apparatus ("IM4000" manufactured by Hitachi High-Tech Corporation). Then, using a field emission scanning electron microscope (FE-SEM), with the image magnification set to 1000x, 50 conductive particles were randomly selected, and the substrate particles of each conductive particle were observed. The particle size of the substrate particles in each conductive particle was measured, and the arithmetic mean of these measurements was taken as the particle size of the substrate particle. The image magnification can also be changed to, for example, 100x, depending on the particle size of the conductive particles.

[0089] <Core Material and Protrusions> Preferably, the conductive particles have protrusions on the outer surface of the conductive portion. Preferably, there are multiple protrusions. Generally, an oxide coating is formed on the surface of the electrode in contact with the conductive particles. When using conductive particles with protrusions on their surface, the oxide coating can be effectively removed during conductive connection by means of the protrusions. Therefore, the electrode and the conductive particles can make more reliable contact, and the contact area between the conductive particles and the electrode can be sufficiently increased, thereby further effectively reducing the connection resistance. Furthermore, when the conductive particles are dispersed in an adhesive and used as a conductive material, the adhesive between the conductive particles and the electrode can be further effectively removed by the protrusions of the conductive particles. Therefore, the contact area between the conductive particles and the electrode can be sufficiently increased, thereby further effectively reducing the connection resistance.

[0090] Examples of methods for forming protrusions on the surface of conductive particles include: a method in which a core material is attached to the surface of a substrate particle and a conductive portion is formed by electroless plating; and a method in which a conductive portion is formed on the surface of a substrate particle by electroless plating, a core material is attached, and a conductive layer is formed by electroless plating.

[0091] Examples of methods for attaching a core material to the surface of substrate particles include: adding a core material to a dispersion of substrate particles and agglomerating and attaching the core material to the surface of the substrate particles by means of, for example, van der Waals forces; and adding a core material to a container in which substrate particles are added and attaching the core material to the surface of the substrate particles by means of mechanical action such as container rotation. Among these, a method of agglomerating and attaching the core material to the surface of the substrate particles in the dispersion is preferred for easier control of the amount of core material attached.

[0092] The conductive particles described above may have a first conductive portion on the surface of the substrate particles, a second conductive portion on the surface of the first conductive portion, and a third conductive portion on the surface of the second conductive portion. Alternatively, a core material may be attached to the surface of the substrate particles. In this case, the core material is preferably covered by the first conductive portion, the second conductive portion, and the third conductive portion. Furthermore, the core material may also be attached to the surface of the first conductive portion. In this case, the core material is preferably covered by the second conductive portion and the third conductive portion. Alternatively, the core material may also be attached to the surface of the second conductive portion. In this case, the core material is preferably covered by the third conductive portion.

[0093] Examples of substances constituting the core material include conductive and non-conductive substances. Examples of conductive substances include metals, metal oxides, conductive non-metals such as graphite, and conductive polymers. Examples of conductive polymers include polyacetylene. Examples of non-conductive substances include silicon dioxide, aluminum oxide, and zirconium oxide. From the viewpoint of improving conductivity, the substance constituting the core material is preferably a metal. The core material is preferably metal particles.

[0094] Examples of the aforementioned metals include: gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium; as well as alloys composed of two or more metals, such as tin-lead alloys, tin-copper alloys, tin-silver alloys, tin-lead-silver alloys, and tungsten carbide. Nickel, copper, silver, or gold are preferred. The metal constituting the core material may be the same as or different from the metal constituting the conductive part (conductive layer).

[0095] The shape of the core material is not particularly limited. The shape of the core material is preferably blocky. Examples of core materials include: particle-shaped blocks, aggregates formed by the aggregation of multiple tiny particles, and amorphous blocks.

[0096] The average height of the plurality of the above-mentioned protrusions is preferably 0.001 μm or more, more preferably 0.05 μm or more, and preferably 0.9 μm or less, more preferably 0.2 μm or less. If the average height of the above-mentioned protrusions is above the lower limit and below the upper limit, the connection resistance between the electrodes can be effectively reduced, thereby further improving the conductivity reliability.

[0097] <Conductive Part> In this invention, the conductive particles have conductive parts on their surfaces. The conductive parts are disposed on the surface of the substrate particles.

[0098] Examples of metals constituting the conductive part include: tin, gold, silver, copper, tin, platinum, palladium, zinc, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys thereof. Furthermore, indium oxide (ITO) doped with tin may also be used. Only one of the above metals may be used, or two or more may be used in combination.

[0099] In the above-mentioned conductive particle A, the conductive part contains indium or bismuth. When the conductive particle is heated at 160°C for 1 minute in an atmospheric atmosphere, the conductive part melts.

[0100] In the above-mentioned conductive particle A, the conductive portion may be formed by one layer or by multiple layers. The conductive portion may also have a multilayer structure of two or more layers. From the viewpoint of further effectively exerting the effects of the present invention, when the conductive portion is formed by multiple layers, it is preferable that the outermost layer of the conductive portion contains indium or bismuth.

[0101] In the above-mentioned conductive particles A, the above-mentioned conductive part may not contain three or more metals with different melting points, or may contain two or fewer metals with different melting points, or may contain one metal (indium only or bismuth only).

[0102] In the aforementioned conductive particle A, the conductive portion may contain two or more metals with different melting points, or three or more metals with different melting points, or four or more metals with different melting points, or five or more metals with different melting points. In the aforementioned conductive particle A, the conductive portion may contain ten or fewer metals with different melting points, or five or fewer metals with different melting points, or four or fewer metals with different melting points, or three or fewer metals with different melting points, or two or fewer metals with different melting points.

[0103] In the aforementioned conductive particles A, one layer may contain two or more metals with different melting points, or three or more metals with different melting points, or four or more metals with different melting points, or five or more metals with different melting points. In the aforementioned conductive particles A, one layer may contain ten or fewer metals with different melting points, or five or fewer metals with different melting points, or four or fewer metals with different melting points, or three or fewer metals with different melting points, or two or fewer metals with different melting points.

[0104] From the viewpoint of further effectively exerting the effects of the present invention, the total content of indium and bismuth in 100% by weight of the conductive portion of the conductive particle A is preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 18% by weight or more. From the viewpoint of further effectively exerting the effects of the present invention, the total content of indium and bismuth in 100% by weight of the conductive portion of the conductive particle A is preferably 50% by weight or less, more preferably 35% by weight or less, and even more preferably 25% by weight or less.

[0105] From the viewpoint of further effectively exerting the effects of the present invention, in the 100% by weight of the indium or bismuth-containing layer in the conductive particles A, the total content of indium and bismuth is preferably 10% by weight or more, more preferably 30% by weight or more, and even more preferably 44% by weight or more. From the viewpoint of further effectively exerting the effects of the present invention, in the 100% by weight of the indium or bismuth-containing layer in the conductive particles A, the total content of indium and bismuth is preferably 99.9% by weight or less, more preferably 98% by weight or less, and even more preferably 95% by weight or less. From the viewpoint of further effectively exerting the effects of the present invention, in the 100% by weight of the indium or bismuth-containing layer in the conductive particles A, the total content of indium and bismuth is further preferably 90% by weight or less, particularly preferably 80% by weight or less, and most preferably 72% by weight or less.

[0106] From the viewpoint of further effectively exerting the effects of the present invention, in the conductive part of the conductive particle A, the indium content is preferably 5% by weight or more, more preferably 10% by weight or more, more preferably 18% by weight or more, and preferably 50% by weight or less, more preferably 35% by weight or less, and more preferably 25% by weight or less.

[0107] From the viewpoint of further effectively exerting the effects of the present invention, in 100% by weight of the indium-containing layer (indium layer) in the conductive particle A, the indium content is preferably 10% by weight or more, more preferably 30% by weight or more, and even more preferably 44% by weight or more. From the viewpoint of further effectively exerting the effects of the present invention, in 100% by weight of the indium-containing layer (indium layer) in the conductive particle A, the indium content is preferably 99.9% by weight or less, more preferably 98% by weight or less, and even more preferably 95% by weight or less. From the viewpoint of further effectively exerting the effects of the present invention, in 100% by weight of the indium-containing layer (indium layer) in the conductive particle A, the indium content is further preferably 90% by weight or less, particularly preferably 80% by weight or less, and most preferably 72% by weight or less.

[0108] From the viewpoint of further effectively exerting the effects of the present invention, in the conductive part of the conductive particle A, the bismuth content is preferably 5% by weight or more, more preferably 10% by weight or more, more preferably 18% by weight or more, and preferably 50% by weight or less, more preferably 35% by weight or less, and more preferably 25% by weight or less.

[0109] From the viewpoint of further effectively exerting the effects of the present invention, in the 100% by weight of the bismuth-containing layer (bismuth layer) in the conductive particle A, the bismuth content is preferably 10% by weight or more, more preferably 30% by weight or more, and even more preferably 44% by weight or more. From the viewpoint of further effectively exerting the effects of the present invention, in the 100% by weight of the bismuth-containing layer (bismuth layer) in the conductive particle A, the bismuth content is preferably 99.9% by weight or less, more preferably 98% by weight or less, and even more preferably 95% by weight or less. From the viewpoint of further effectively exerting the effects of the present invention, in the 100% by weight of the bismuth-containing layer (bismuth layer) in the conductive particle A, the bismuth content is further preferably 90% by weight or less, particularly preferably 80% by weight or less, and most preferably 72% by weight or less.

[0110] When the conductive particle A is heated at 160°C in an atmospheric atmosphere for 1 minute (melting test A), the conductive part melts. At least the surface portion of the conductive part melts. Preferably, the entire surface of the conductive part melts. For conductive particles with protrusions on the outer surface of the conductive part, it is preferable that both the surface portion of the conductive part with protrusions and the surface portion of the conductive part without protrusions melt.

[0111] [Melting Test A] The conductive particles A were dispersed on a Cu plate and heated at 160°C for 1 minute under atmospheric conditions. A cross-section of the heated conductive particles A was cut using a FIB-SEM with a focused ion beam (FIB). After cutting the cross-section, the molten state of the conductive portion of the heated conductive particles A was observed near the junction of the conductive particles and the Cu plate using an electron microscope (SEM).

[0112] In the melting test A, the thickness of the conductive portion in the conductive particle A is 100%, and the thickness of the molten conductive portion is preferably 1% or more, more preferably 10% or more, and even more preferably 20% or more. There is no particular upper limit to the thickness of the molten conductive portion in the melting test A. The thickness of the molten conductive portion in the melting test A can also be 100% (overall).

[0113] In the above-mentioned conductive particle B, the conductive part contains three or more metals with different melting points. When the conductive particle is heated for 1 minute in an atmospheric environment at 200°C, the conductive part melts.

[0114] In the above-mentioned conductive particle B, the conductive portion may not contain indium. In the above-mentioned conductive particle B, the conductive portion may not contain bismuth.

[0115] When the conductive particle B is heated for 1 minute in an atmospheric environment at 160°C, the conductive part may not melt. It is preferable that the conductive part melts when the conductive particle B is heated for 1 minute in an atmospheric environment at at least one temperature within a temperature range exceeding 160°C and below 200°C.

[0116] In the above-mentioned conductive particle B, the conductive part may contain four or more metals with different melting points, or five or more metals with different melting points. In the above-mentioned conductive particle B, the conductive part may contain ten or fewer metals with different melting points, or five or fewer metals with different melting points, or four or fewer metals with different melting points.

[0117] In the aforementioned conductive particles B, one layer may contain two or more metals with different melting points, or three or more metals with different melting points, or four or more metals with different melting points, or five or more metals with different melting points. In the aforementioned conductive particles B, one layer may contain ten or fewer metals with different melting points, or five or fewer metals with different melting points, or four or fewer metals with different melting points, or three or fewer metals with different melting points, or two or fewer metals with different melting points.

[0118] In the above-mentioned conductive particle B, the conductive portion may be formed from one layer, two layers, three layers, or four or more layers. In the above-mentioned conductive particle B, the conductive portion may have one conductive layer, two conductive layers, three conductive layers, or four or more conductive layers. In the case where the conductive portion has one or two conductive layers, the material of each conductive layer may also contain an alloy containing two or more metals.

[0119] From the viewpoint of further effectively exerting the effects of the present invention, the conductive particle B is preferably composed of indium or bismuth.

[0120] From the viewpoint of further effectively exerting the effects of the present invention, the total content of indium and bismuth in 100% by weight of the conductive portion of the conductive particle B is preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 18% by weight or more. From the viewpoint of further effectively exerting the effects of the present invention, the total content of indium and bismuth in 100% by weight of the conductive portion of the conductive particle B is preferably 50% by weight or less, more preferably 35% by weight or less, and even more preferably 25% by weight or less.

[0121] From the viewpoint of further effectively exerting the effects of the present invention, in the 100% by weight of the indium or bismuth-containing layer in the conductive particles B, the total content of indium and bismuth is preferably 10% by weight or more, more preferably 30% by weight or more, and even more preferably 44% by weight or more. From the viewpoint of further effectively exerting the effects of the present invention, in the 100% by weight of the indium or bismuth-containing layer in the conductive particles B, the total content of indium and bismuth is preferably 99.9% by weight or less, more preferably 98% by weight or less, and even more preferably 95% by weight or less. From the viewpoint of further effectively exerting the effects of the present invention, in the 100% by weight of the indium or bismuth-containing layer in the conductive particles B, the total content of indium and bismuth is further preferably 90% by weight or less, particularly preferably 80% by weight or less, and most preferably 72% by weight or less.

[0122] From the viewpoint of further effectively exerting the effects of the present invention, in the conductive part of the conductive particle B, the indium content is preferably 5% by weight or more, more preferably 10% by weight or more, more preferably 18% by weight or more, and preferably 50% by weight or less, more preferably 35% by weight or less, and more preferably 25% by weight or less.

[0123] From the viewpoint of further effectively exerting the effects of the present invention, in 100% by weight of the indium-containing layer (indium layer) in the conductive particles B, the indium content is preferably 10% by weight or more, more preferably 30% by weight or more, and even more preferably 44% by weight or more. From the viewpoint of further effectively exerting the effects of the present invention, in 100% by weight of the indium-containing layer (indium layer) in the conductive particles B, the indium content is preferably 99.9% by weight or less, more preferably 98% by weight or less, and even more preferably 95% by weight or less. From the viewpoint of further effectively exerting the effects of the present invention, in 100% by weight of the indium-containing layer (indium layer) in the conductive particles B, the indium content is further preferably 90% by weight or less, particularly preferably 80% by weight or less, and most preferably 72% by weight or less.

[0124] From the viewpoint of further effectively exerting the effects of the present invention, in the conductive part of the conductive particle B, the bismuth content is preferably 5% by weight or more, more preferably 10% by weight or more, more preferably 18% by weight or more, and preferably 50% by weight or less, more preferably 35% by weight or less, and more preferably 25% by weight or less.

[0125] From the viewpoint of further effectively exerting the effects of the present invention, in the 100% by weight of the bismuth-containing layer (bismuth layer) of the conductive particle B, the bismuth content is preferably 10% by weight or more, more preferably 30% by weight or more, and even more preferably 44% by weight or more. From the viewpoint of further effectively exerting the effects of the present invention, in the 100% by weight of the bismuth-containing layer (bismuth layer) of the conductive particle B, the bismuth content is preferably 99.9% by weight or less, more preferably 98% by weight or less, and even more preferably 95% by weight or less. From the viewpoint of further effectively exerting the effects of the present invention, in the 100% by weight of the bismuth-containing layer (bismuth layer) of the conductive particle B, the bismuth content is further preferably 90% by weight or less, particularly preferably 80% by weight or less, and most preferably 72% by weight or less.

[0126] Furthermore, when the aforementioned conductive particle B is heated at 200°C for 1 minute in an atmospheric atmosphere (melting test B), the aforementioned conductive portion melts. At least the surface portion of the aforementioned conductive portion melts. Preferably, the entire surface of the aforementioned conductive portion melts. For conductive particles with protrusions on the outer surface of the conductive portion, it is preferable that both the surface portion of the aforementioned conductive portion with protrusions and the surface portion of the aforementioned conductive portion without protrusions melt.

[0127] [Melting Test B] The conductive particles B described above were dispersed on a Cu plate and heated at 200°C for 1 minute under atmospheric conditions. A cross-section of the heated conductive particles B was cut using a FIB-SEM with a focused ion beam (FIB). After cutting the cross-section, the molten state of the conductive portion of the heated conductive particles B was observed near the junction of the conductive particles and the Cu plate using an electron microscope (SEM).

[0128] In the melting test B, the thickness of the conductive portion in the conductive particle B is 100%, and the thickness of the molten conductive portion is preferably 1% or more, more preferably 10% or more, and even more preferably 20% or more. There is no particular upper limit to the thickness of the molten conductive portion in the melting test B. The thickness of the molten conductive portion in the melting test B can also be 100% (overall).

[0129] From the viewpoint of improving the adhesion between the conductive portion and the substrate particles, the conductive portion of the conductive particles A and B preferably contains copper or nickel. The conductive portion of the conductive particles A and B may contain copper or nickel.

[0130] From the viewpoint of improving the adhesion between the conductive portion and the substrate particles, the conductive portion of the conductive particles A and B preferably has a layer containing copper or nickel. From the viewpoint of improving the adhesion between the conductive layer and the substrate particles, the substrate particles are preferably in contact with the layer containing copper or nickel. From the viewpoint of improving the adhesion between the conductive layer and the substrate particles, the layer containing copper or nickel is preferably the innermost layer of the conductive portion. From the viewpoint of improving the adhesion between the conductive layer and the substrate particles, the metal constituting the innermost layer of the conductive portion is preferably copper or nickel, and more preferably nickel.

[0131] From the viewpoint of increasing the contact area between the conductive particles and the electrode to further improve the conductivity reliability, the conductive part preferably contains tin. From the viewpoint of increasing the contact area with the conductive particles to further improve the conductivity reliability, the tin content in the conductive part is preferably 2% by weight or more, more preferably 10% by weight or more, more preferably 16% by weight or more, and preferably 50% by weight or less, more preferably 30% by weight or less, and more preferably 22% by weight or less.

[0132] From the viewpoint of increasing the contact area between conductive particles and electrodes to further improve conductivity reliability, the tin content in the 100% by weight of the tin-containing layer (tin layer) is preferably 2% by weight or more, more preferably 10% by weight or more, more preferably 18% by weight or more, and preferably 90% by weight or less, more preferably 70% by weight or less, and more preferably 56% by weight or less.

[0133] From the viewpoint of further improving conductivity reliability, the conductive portion preferably has a conductive layer with a melting point of 200°C or lower. From the viewpoint of further improving conductivity reliability, the conductive portion preferably has a conductive layer with a melting point of 190°C or lower, preferably has a conductive layer with a melting point of 180°C or lower, and preferably has a conductive layer with a melting point of 170°C or lower. The conductive portion may have only one conductive layer with a melting point of 200°C or lower, or it may have two or more conductive layers.

[0134] From the viewpoint of improving the bonding and adhesion between the conductive particles and the electrode, the conductive layer with a melting point of 200°C or less is preferably the outer surface layer of the conductive portion. From the viewpoint of improving the bonding and adhesion between the conductive particles and the electrode, the conductive portion has two or more conductive layers, and the conductive layer with a melting point of 200°C or less is preferably the outermost layer of the conductive portion.

[0135] From the viewpoint of ensuring good melting of the conductive part, the content of the conductive layer with a melting point of 200°C or less in 100% by weight of the conductive part is preferably 1% by weight or more, more preferably 3% by weight or more, more preferably 10% by weight or more, and more preferably 80% by weight or less, more preferably 50% by weight or less, and more preferably 30% by weight or less.

[0136] From the viewpoint of ensuring good melting of the conductive portion, it is preferable that the conductive portion consists of two or more conductive layers, and that the two or more conductive layers are stacked (arranged) in such a manner that the melting point of the conductive layer gradually increases from the outer surface of the conductive portion toward the inner surface. From the viewpoint of ensuring good melting of the conductive portion, it is preferable that the conductive portion consists of two or more conductive layers, and that the two or more conductive layers are stacked in such a manner that the melting point of the conductive layer gradually decreases from the outer surface of the conductive portion toward the inner surface. From the viewpoint of ensuring good melting of the conductive portion, it is preferable that, among adjacent two or more conductive layers, the melting point of the outer conductive layer is lower than the melting point of the inner conductive layer.

[0137] Preferably, the conductive part comprises three or more conductive layers, and the conductive part sequentially comprises a conductive layer P, a conductive layer Q, and a conductive layer R from its outer surface toward its thickness direction. Preferably, the conductive layer P is the outermost layer of the conductive part. Preferably, the conductive layer P, the conductive layer Q, and the conductive layer R are continuously stacked (arranged) in the conductive particles. Preferably, the conductive part has no conductive layer or has one or more conductive layers inside the conductive layer R. The conductive part may have a conductive layer inside the conductive layer R, or it may not have a conductive layer. When the conductive particles satisfy the above-mentioned preferred state, the bonding strength between the conductive particles and the electrode can be improved, further enhancing the conductivity reliability.

[0138] That is, from the viewpoint of improving the bonding between the conductive particles and the electrode, and further improving the reliability of conduction, it is preferable that the conductive layer P, the conductive layer Q, and the conductive layer R are sequentially deposited (distributed) from the outer surface of the conductive portion toward the inner side in the thickness direction of the conductive portion. In the conductive particles 21 shown in FIG2, the third conductive portion 23C is the conductive layer P, the second conductive layer 23B is the conductive layer Q, and the first conductive layer 23A is the conductive layer R.

[0139] From the viewpoint of ensuring good melting of the conductive portion, it is preferable that the melting point of the conductive layer P is lower than the melting point of the conductive layer Q, and the melting point of the conductive layer Q is lower than the melting point of the conductive layer R. From the viewpoint of ensuring good melting of the conductive portion, it is preferable that the melting points of the conductive layer P, the conductive layer Q, and the conductive layer R satisfy the following relationship.

[0140] Melting point of conductive layer P < Melting point of conductive layer Q < Melting point of conductive layer R

[0141] Furthermore, when the conductive part has a conductive layer inside the conductive layer R, the melting point of the conductive layer inside the conductive layer R is not particularly limited.

[0142] From the viewpoint of ensuring good melting of the conductive part, the melting point of the conductive layer P is preferably 0°C or higher, more preferably 70°C or higher, more preferably 100°C or higher, more preferably 300°C or lower, more preferably 280°C or lower, and more preferably 240°C or lower.

[0143] From the viewpoint of sufficiently reducing the melting temperature of the conductive part and improving the compatibility of the conductive part, the melting point of the conductive layer P is preferably 5°C or more lower than the melting point of the conductive layer Q, more preferably 10°C or more lower, and preferably 150°C or less lower than the melting point of the conductive layer Q, more preferably 100°C or less lower.

[0144] From the viewpoint of ensuring good melting of the conductive portion, the melting point of the conductive layer Q is preferably at least 200°C lower than the melting point of the conductive layer R, and more preferably at least 500°C lower. The melting point of the conductive layer Q may be at least 2000°C lower than the melting point of the conductive layer R, or at least 1500°C lower, or at least 1000°C lower.

[0145] From the viewpoint of sufficiently reducing the melting temperature of the conductive portion, the material of the conductive portion preferably includes components of solder. From the viewpoint of sufficiently reducing the melting temperature of the conductive portion, the materials of the conductive layer P and the conductive layer Q preferably include components of solder. From the viewpoint of sufficiently reducing the melting temperature of the conductive portion, it is preferable that when the conductive particles are heated at 200°C for 1 minute, the conductive layer P and the conductive layer Q can melt (merge) to form solder; more preferably, when the conductive particles are heated at 160°C for 1 minute, the conductive layer P and the conductive layer Q can melt (merge) to form solder. The conductive layer P and the conductive layer Q may melt only near their interface, or the conductive layer P and the conductive layer Q may melt entirely. From the viewpoint of sufficiently reducing the melting temperature of the conductive portion, a composite material of the two materials, the material of the conductive layer P and the material of the conductive layer Q, preferably includes components of solder. The materials of the conductive layer P and the conductive layer Q are contained in actually different layers. The composite material refers to the material of the conductive layer P and the material of the conductive layer Q as a single composition. The solder containing the above-mentioned solder components is preferably a lead-free solder.

[0146] The solder described above is preferably a metal with a melting point below 450°C (low-melting-point metal). The solder described above is preferably a fusion-additive material with a liquidus temperature below 450°C, as defined in JIS Z3001: Welding Terminology. The solder described above can be a eutectic solder or a lead-free solder. Examples of components of the solder described above include: zinc, gold, silver, lead, copper, tin, bismuth, indium, tin-silver alloys, tin-copper alloys, tin-silver-copper alloys, tin-bismuth alloys, tin-zinc alloys, and tin-indium alloys.

[0147] From the viewpoint of sufficiently reducing the melting temperature of the conductive part, the conductive layer P preferably contains indium (melting point 157°C) or bismuth (melting point 272°C), the conductive layer Q preferably contains tin (melting point 232°C), and the conductive layer R preferably contains nickel (melting point 1455°C). From the viewpoint of sufficiently reducing the melting temperature of the conductive part, it is preferable that the conductive layer P is an indium layer containing indium or a bismuth layer containing bismuth, the conductive layer Q is a tin layer containing tin, and the conductive layer R is a nickel layer containing nickel. From the viewpoint of sufficiently reducing the melting temperature of the conductive part, it is even more preferable that the conductive layer P is an indium layer containing indium, the conductive layer Q is a tin layer containing tin, and the conductive layer R is a nickel layer containing nickel.

[0148] From the viewpoint of further improving the reliability of conduction, in the above-mentioned nickel layer, the nickel content is preferably 10% by weight or more, more preferably 30% by weight or more, more preferably 44% by weight or more, and preferably 90% by weight or less, more preferably 80% by weight or less, and more preferably 72% by weight or less.

[0149] From the viewpoint of sufficiently reducing the melting temperature of the conductive part, the conductive part preferably contains bismuth.

[0150] From the viewpoint of sufficiently reducing the melting temperature of the conductive part, the bismuth content in 100% by weight of the conductive part is preferably 0.5% by weight or more, more preferably 1% by weight or more, more preferably 2% by weight or more, and preferably 50% by weight or less, more preferably 25% by weight or less, and more preferably 10% by weight or less.

[0151] From the viewpoint of sufficiently reducing the melting temperature of the conductive part, in the above-mentioned 100% by weight of the bismuth-containing layer, the bismuth content is preferably 1% by weight or more, more preferably 2% by weight or more, and even more preferably 4% by weight or more, and preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 20% by weight or less.

[0152] From the viewpoint of further effectively exerting the effects of the present invention, the melting point of the conductive portion of the conductive particles A and B as a whole is preferably below 200°C, more preferably below 160°C, and even more preferably below 155°C. The melting point of the conductive portion of the conductive particles A and B as a whole may be above 25°C or above, or above 50°C.

[0153] The melting point of the above-mentioned conductive part as a whole can be determined by the following method.

[0154] Using a differential scanning calorimeter (DSC), 35 mg of particles were measured at a heating rate of 5°C / min. In the case of multiple peaks, the peak with the lowest melting point was taken as the peak of the entire conductive part.

[0155] Preferably, the composition of the conductive layer P diffuses into the conductive layer Q upon heating. The diffusion coefficient of the conductive layer P relative to the conductive layer Q at 160°C is preferably 1.0 × 10⁻²⁰ m² / s or more, more preferably 1.0 × 10⁻¹⁹ m² / s or more, further preferably 1.0 × 10⁻¹⁸ m² / s or more, and even more preferably 1.0 × 10⁻¹⁷ m² / s or more. If the diffusion coefficient of the conductive layer P relative to the conductive layer Q at 160°C is at or above the lower limit mentioned above, then the conductive layer P and the conductive layer Q can form solder well, and the melting temperature of the conductive portion can be sufficiently reduced. There is no particular limitation on the upper limit of the diffusion coefficient of the conductive layer P relative to the conductive layer Q at 160°C. The diffusion coefficient of the conductive layer P relative to the conductive layer Q at 160°C can be less than 1.0×10-10 m2 / s, less than 1.0×10-13 m2 / s, or less than 1.0×10-14 m2 / s.

[0156] From the viewpoint of sufficiently reducing the melting temperature of the conductive part, the diffusion coefficient of the conductive layer R relative to the conductive layer Q at 160°C is preferably 1.0×10-50 m2 / s or more, more preferably 1.0×10-40 m2 / s or more, and preferably 1.0×10-25 m2 / s or less, and more preferably 1.0×10-30 m2 / s or less.

[0157] The diffusion coefficient of the conductive layer P relative to the conductive layer Q at 160°C and the diffusion coefficient of the conductive layer R relative to the conductive layer Q at 160°C can be measured by the following method.

[0158] Conductive particles were prepared by heating them at 160°C for 5 minutes and 15 minutes respectively using a vacuum dryer. The heated conductive particles were added to a "Technovit 4000" manufactured by Kulzer Corporation at a content of 30% by weight and dispersed to prepare an inspection embedding resin body containing conductive particles. The conductive particles were cut into cross-sections using an ion milling device (e.g., "IM4000" manufactured by Hitachi High-Tech Corporation) by dispersing the conductive particles (substrate particles) near their centers in the above-mentioned inspection embedding resin body. Subsequently, using a field emission scanning electron microscope-energy dispersive X-ray spectroscopy (FE-SEM-EDX), with the center of the conductive particles (substrate particles) in each inspection embedding resin body as the origin, the concentration distribution of the constituent components of conductive layer P in conductive layer Q and the concentration distribution of the constituent components of conductive layer R in conductive layer Q were measured. Using the following formula (Fick's second law (diffusion equation)), the diffusion coefficients of the conductive layer P relative to the conductive layer Q at 160°C and the diffusion coefficients of the conductive layer R relative to the conductive layer Q at 160°C can be calculated. Examples of field emission scanning electron microscopes include the "Regulus 8200" manufactured by Hitachi High Technology Co., Ltd.

[0159] (∂C / ∂t)=D(∂2C / ∂x2) C: Concentration of the constituent components of conductive layer Q in conductive layer P or conductive layer R; D: Diffusion coefficient; t: Time; x: Distance

[0160] From the viewpoint of sufficiently reducing the melting temperature of the conductive part, it is preferable that a peak exists in the region of 32° to 34° when measuring the X-ray diffraction spectrum of the conductive part. From the viewpoint of sufficiently reducing the melting temperature of the conductive part, it is preferable that a peak exists in the region of 55.5° to 57.5° when measuring the X-ray diffraction spectrum of the conductive part. From the viewpoint of sufficiently reducing the melting temperature of the conductive part, it is preferable that peaks exist in the region of 32° to 34° and in the region of 55.5° to 57.5° when measuring the X-ray diffraction spectrum of the conductive part.

[0161] When peaks exist in the X-ray diffraction spectrum of the conductive part in the region between 32° and 34° and in the region between 55.5° and 57.5°, it is preferable that the highest peak height in the region between 32° and 34° is higher than the highest peak height in the region between 55.5° and 57.5°. In this case, the content of the alloy with a lower melting point in the conductive part can be kept within a good range, thereby sufficiently reducing the melting temperature of the conductive part.

[0162] The X-ray diffraction spectrum of the above-mentioned conductive part can be measured using an X-ray diffraction device (such as the "RINT2500VHF" manufactured by Rigaku Electric Co., Ltd.).

[0163] From the viewpoint of further improving conductivity reliability by preventing metal oxidation of the conductive part and removing oxide coatings or foreign matter from the surface of the conductive part, the outer surface of the conductive part is preferably treated with flux. The flux is not particularly limited.

[0164] Examples of fluxes mentioned above include: zinc chloride, mixtures of zinc chloride and inorganic halides, mixtures of zinc chloride and inorganic acids, molten salts, phosphoric acid, derivatives of phosphoric acid, organohalides, hydrazine, amine compounds, organic acids, and rosin. Only one type of flux may be used, or two or more may be used in combination.

[0165] Examples of the molten salt mentioned above include ammonium chloride. Examples of the organic acids mentioned above include lactic acid, citric acid, stearic acid, glutamic acid, and glutaric acid. Examples of the rosin mentioned above include activated rosin and unactivated rosin. The flux mentioned above is preferably an organic acid or rosin with two or more carboxyl groups. The flux mentioned above can be an organic acid with two or more carboxyl groups or rosin. By using organic acids or rosin with two or more carboxyl groups, the connection strength and conductivity reliability are further improved.

[0166] Examples of organic acids having two or more carboxyl groups include succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, and sebacic acid.

[0167] Examples of the above-mentioned amine compounds include: cyclohexylamine, dicyclohexylamine, benzylamine, diphenylmethylamine, imidazole, benzimidazole, phenylimidazolium, carboxybenzimidazole, benzotriazole, and carboxybenzotriazole.

[0168] The above-mentioned rosin is a rosin-type resin with arosin acid as the main component. Examples of such rosin-type resins include arosin acid and acrylic acid-modified rosin. The flux is preferably a rosin-type flux, and more preferably arosin acid flux. By using this preferred flux, the flux effect is further improved.

[0169] The activation temperature (melting point) of the above-mentioned flux is preferably above 50°C, more preferably above 70°C, further preferably above 80°C, and preferably below 200°C, more preferably below 190°C, further preferably below 160°C, further preferably below 150°C, and even more preferably below 140°C. If the activation temperature of the above-mentioned flux is above the lower limit and below the upper limit, the flux effect is further improved.

[0170] The melting point of the above flux can be determined by differential scanning calorimetry (DSC). Examples of differential scanning calorimetry (DSC) devices include the "EXSTAR DSC7020" manufactured by SII Corporation.

[0171] Furthermore, the boiling point of the above-mentioned flux is preferably below 200°C.

[0172] Preferably, the flux described above is a flux that releases cationic ions upon heating. By using a flux that releases cationic ions upon heating, the connection strength and conductivity reliability are further improved.

[0173] As a flux that releases cations by heating, the above-mentioned thermal cationic initiator (thermal cationic hardener) can be cited as an example.

[0174] From the viewpoint of further improving the flux effect, the flux is preferably a salt of acid compound and alkali compound.

[0175] The aforementioned acid compound is preferably an organic compound having a carboxyl group. Examples of the aforementioned acid compound include: malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, citric acid, and malic acid, which are aliphatic carboxylic acids; cyclohexylcarboxylic acid and 1,4-cyclohexyldicarboxylic acid, which are cyclic aliphatic carboxylic acids; and terephthalic acid, trimellitic acid, and ethylenediaminetetraacetic acid, which are aromatic carboxylic acids. From the viewpoint of further effectively improving the connection strength and further effectively improving the conductivity reliability, the aforementioned acid compound is preferably glutaric acid, cyclohexylcarboxylic acid, or adipic acid.

[0176] The aforementioned alkaline compound is preferably an organic compound having an amino group. Examples of such alkaline compounds include: diethanolamine, triethanolamine, methyldiethanolamine, ethyldiethanolamine, cyclohexylamine, dicyclohexylamine, benzylamine, diphenylmethylamine, 2-methylbenzylamine, 3-methylbenzylamine, 4-tert-butylbenzylamine, N-methylbenzylamine, N-ethylbenzylamine, N-phenylbenzylamine, N-tert-butylbenzylamine, N-isopropylbenzylamine, N,N-dimethylbenzylamine, imidazole compounds, and triazole compounds. From the viewpoint of further effectively improving connection strength and further effectively improving conductivity reliability, the aforementioned alkaline compound is preferably benzylamine.

[0177] Of the total surface area of ​​the aforementioned substrate particles, the area of ​​the conductive portion (the coverage rate of the conductive portion) is preferably 80% or more, and more preferably 90% or more. There is no particular upper limit to the coverage rate of the conductive portion. The coverage rate of the conductive portion may be 100%, less than 100%, or less than 99%. If the coverage rate of the conductive portion is above the lower limit, the conductivity reliability can be further improved effectively when electrically connecting electrodes.

[0178] The thickness of the conductive portion is preferably 0.005 μm or more, more preferably 0.01 μm or more, and preferably 10 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less. If the thickness of the conductive portion is above the lower limit and below the upper limit, the conductivity reliability can be further improved effectively, and the conductive particles will not become too hard, allowing the conductive particles to deform sufficiently during the connection between electrodes.

[0179] When the conductive portion is formed of multiple layers, the thickness of the outermost layer of the conductive portion is preferably 0.001 μm or more, more preferably 0.01 μm or more, and preferably 0.5 μm or less, more preferably 0.3 μm or less. If the thickness of the outermost layer of the conductive portion is above the lower limit and below the upper limit, the outermost layer of the conductive portion becomes uniform, the corrosion resistance becomes sufficiently high, and the connection resistance between electrodes can be sufficiently reduced.

[0180] The thickness of the conductive part can be measured, for example, by observing the cross-section of the conductive particles using a transmission electron microscope (TEM).

[0181] There is no particular limitation on the method for forming the conductive portion on the surface of the aforementioned substrate particles. Examples of methods for forming the conductive portion include: electroless plating, electroplating, physical impact, mechanochemical reaction, physical vapor deposition or physical adsorption, and methods of applying metal powder or a paste containing metal powder and a binder to the surface of the substrate particles. Preferably, the method for forming the conductive portion is electroless plating, electroplating, or physical impact. Examples of methods using physical vapor deposition include: vacuum vapor deposition, ion plating, and ion sputtering. Furthermore, in the methods using physical impact, for example, Theta Composer (manufactured by Tokusuke Manufacturing Co., Ltd.) can be used.

[0182] <Insulating Particles> The conductive particles of the present invention preferably have a plurality of insulating particles on their surface. In this case, if the conductive particles are used to connect electrodes, short circuits between adjacent electrodes can be prevented. Specifically, when the plurality of conductive particles are in contact with each other, since there are insulating particles between the plurality of electrodes, short circuits between electrodes that are not adjacent in the lateral direction (not between upper and lower electrodes) can be prevented. Furthermore, when connecting electrodes, by applying pressure to the conductive particles using two electrodes, insulating particles between the conductive particles and the electrodes can be easily removed. Moreover, in the case where the conductive part has a plurality of protruding conductive particles on its outer surface, insulating particles between the conductive particles and the electrodes can be removed even more easily.

[0183] The insulating particles described above are preferably polymers of polymeric compounds. There are no particular limitations on the polymeric compounds described above. Examples of polymeric compounds include the aforementioned resin particles. From the viewpoint of improving the adhesion between conductive and insulating particles and further enhancing insulation reliability, the insulating particles are preferably resin particles.

[0184] Examples of methods for depositing the insulating particles on the surface of the conductive portion include chemical methods and physical or mechanical methods. Examples of chemical methods include interfacial polymerization, suspension polymerization in the presence of particles, and emulsion polymerization. Examples of physical or mechanical methods include spray drying, mixing, electrostatic adhesion, spraying, impregnation, and vacuum evaporation. In the case of electrical connection between electrodes, from the viewpoint of further effectively improving insulation reliability and conductivity reliability, a physical method is preferred for depositing the insulating particles on the surface of the conductive portion.

[0185] The particle size of the insulating particles can be appropriately selected according to the particle size of the conductive particles and the intended use of the conductive particles. Preferably, the particle size of the insulating particles is 10 nm or more, more preferably 100 nm or more, further preferably 200 nm or more, especially 300 nm or more, and preferably 4000 nm or less, more preferably 2000 nm or less, further preferably 1500 nm or less, and especially preferably 1000 nm or less. If the particle size of the insulating particles is above or below the lower limit, when the conductive particles are dispersed in the adhesive resin, the plurality of conductive particles become difficult to contact each other. If the particle size of the insulating particles is below the upper limit, it is no longer necessary to excessively increase the pressure to remove the insulating particles between the electrodes and the conductive particles when connecting the electrodes, nor is it necessary to heat to a high temperature.

[0186] The particle size of the aforementioned insulating particles is preferably the average particle size, which represents the number average particle size. The particle size of the aforementioned insulating particles can be determined using a particle size distribution measuring device or the like. The particle size of the aforementioned insulating particles is preferably determined by: observing any 50 insulating particles using an electron microscope or an optical microscope and calculating the average value; or performing a laser diffraction particle size distribution measurement. When measuring the particle size of the aforementioned insulating particles among the aforementioned conductive particles, the measurement can be performed, for example, in the following manner.

[0187] Conductive particles were added to "Technovit 4000" manufactured by Kulzer Corporation at a content of 30% by weight and dispersed to prepare an inspection embedding resin containing conductive particles. The conductive particles were cut into cross-sections using an ion milling apparatus ("IM4000" manufactured by Hitachi High-Tech Co., Ltd.) by passing the conductive particles near their centers in the aforementioned inspection embedding resin. Then, using a field emission scanning electron microscope (FE-SEM), with the image magnification set to 50,000x, 50 conductive particles were randomly selected, and the insulating particles of each conductive particle were observed. The circumference diameter of the insulating particles in each conductive particle was measured as the particle size, and the arithmetic mean of these values ​​was taken as the particle size of the insulating particle.

[0188] The conductive particles of the present invention may also incorporate two or more insulating particles with different particle sizes. By incorporating two or more insulating particles with different particle sizes, the smaller insulating particles will enter the gaps covered by the larger insulating particles, thereby further efficiently depositing insulating particles on the surface of the conductive particles.

[0189] Preferably, the coefficient of variation (CV value) of the particle size of the insulating particles is 20% or less. If the coefficient of variation of the particle size of the insulating particles is below the upper limit, the thickness of the insulating particles in the obtained conductive particles becomes more uniform, pressure can be applied more easily and uniformly during conductive connection, and the connection resistance between electrodes can be further reduced.

[0190] The above coefficient of variation (CV value) can be determined in the following manner.

[0191] CV value (%) = (ρ / Dn) × 100 ρ: Standard deviation of the particle size of insulating particles Dn: Average particle size of insulating particles

[0192] The shape of the insulating particles is not particularly limited. The insulating particles may be spherical, or any other shape other than spherical, or flat, etc.

[0193] From the viewpoint of improving the reliability of insulation, the area of ​​the portion covered by the insulating particles (the coverage rate of the insulating particles) of the total surface area of ​​the conductive part is preferably 30% or more, more preferably 35% or more, and preferably 70% or less, more preferably 60% or less.

[0194] The coverage rate of the insulating particles described above can be determined, for example, by the following method. Using a field emission scanning electron microscope (FE-SEM), with the image magnification set to 50,000x, 20 conductive particles are randomly selected, and the surface of each conductive particle is observed. For the obtained conductive particles, the percentage of the surface area of ​​the portion covered by the insulating particles relative to the projected area of ​​the entire particle is measured, and the arithmetic mean is taken as the coverage rate of the insulating particles.

[0195] Furthermore, the coverage rate of the aforementioned insulating particles can also be determined by mapping and analysis such as EDX attached to SEM.

[0196] The coverage rate of the above-mentioned insulating particles can be adjusted, for example, by the amount of inorganic particles added relative to the substrate particles, the mixing time, etc., and there is no particular limitation on the method of adjusting the coverage rate.

[0197] (Conductive Material) The conductive material of the present invention comprises the above-mentioned conductive particles and an adhesive resin. Preferably, the conductive particles are dispersed in the adhesive resin. Preferably, the conductive particles are dispersed in the adhesive resin to form the conductive material. Preferably, the conductive material is an anisotropic conductive material. Preferably, the conductive material is used for electrical connections between electrodes. Preferably, the conductive material is a conductive material for circuit connections.

[0198] The above-mentioned adhesive resin is not particularly limited. Known insulating resins can be used as the above-mentioned adhesive resin. The above-mentioned adhesive resin preferably contains a thermoplastic component (thermoplastic compound) or a curing component, more preferably it contains a curing component. Examples of the above-mentioned curing component include: a photocurable component and a thermocurable component. The above-mentioned photocurable component preferably contains a photocurable compound and a photopolymerization initiator. The above-mentioned thermocurable component preferably contains a thermocurable compound and a thermosetting agent.

[0199] Examples of adhesive resins mentioned above include: vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, and elastomers. Only one type of adhesive resin may be used, or two or more may be used in combination.

[0200] Examples of the aforementioned ethylene resin include vinyl acetate resin, acrylic resin, and styrene resin. Examples of the aforementioned thermoplastic resin include polyolefin resin, ethylene-vinyl acetate copolymer, and polyamide resin. Examples of the aforementioned curing resin include epoxy resin, urethane resin, polyimide resin, and unsaturated polyester resin. Furthermore, the aforementioned curing resin may also be a room-temperature curing resin, a thermosetting resin, a light-curing resin, or a moisture-curing resin. The aforementioned curing resin may also be used in combination with a curing agent. Examples of the aforementioned thermoplastic block copolymer include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrides of styrene-butadiene-styrene block copolymer, and hydrides of styrene-isoprene-styrene block copolymer. Examples of the aforementioned elastomer include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.

[0201] In addition to the conductive particles and the adhesive resin, the conductive material may also contain various additives such as fillers, extenders, softeners, plasticizers, polymerization catalysts, hardening catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents and flame retardants.

[0202] The method for dispersing the conductive particles in the adhesive resin can use previously known dispersion methods and is not particularly limited. Examples of methods for dispersing the conductive particles in the adhesive resin include: Adding the conductive particles to the adhesive resin and then mixing them using a planetary mixer or the like to disperse them; uniformly dispersing the conductive particles in water or an organic solvent using a homogenizer, then adding them to the adhesive resin and mixing them using a planetary mixer or the like to disperse them; diluting the adhesive resin with water or an organic solvent, then adding the conductive particles and mixing them using a planetary mixer or the like to disperse them.

[0203] The viscosity (η25) of the above-mentioned conductive material at 25°C is preferably 30 Pa·s or more, more preferably 50 Pa·s or more, and preferably 400 Pa·s or less, more preferably 300 Pa·s or less. If the viscosity of the above-mentioned conductive material at 25°C is above the lower limit and below the upper limit, the insulation reliability between electrodes can be further improved effectively, and the conduction reliability between electrodes can be further improved effectively. The above-mentioned viscosity (η25) can be appropriately adjusted by the type and amount of the formulation components.

[0204] The above viscosity (η25) can be measured, for example, using an E-type viscometer ("TVE22L" manufactured by Toki Sangyo Co., Ltd.) at 25°C and 5 rpm.

[0205] The above-mentioned conductive material can be used as a conductive paste and a conductive film, etc. When the conductive material is a conductive film, a film without conductive particles can also be deposited 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.

[0206] Of the aforementioned conductive material, the content of the adhesive resin is preferably 10% by weight or more, more preferably 30% by weight or more, further 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. If the content of the adhesive resin is above the aforementioned lower limit and below the aforementioned upper limit, conductive particles can be efficiently disposed between the electrodes, thereby further improving the connection reliability of the connection object components connected by the conductive material.

[0207] Of the above-mentioned conductive material, the content of the conductive particles is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and preferably 80% by weight or less, more preferably 60% by weight or less, further preferably 40% by weight or less, particularly preferably 20% by weight or less, and most preferably 10% by weight or less. If the content of the conductive particles is above the lower limit and below the upper limit, the conductivity reliability and insulation reliability can be further improved.

[0208] (Connecting Structure) The connecting structure of the present invention comprises: a first connecting member having a first electrode on its surface; a second connecting member having a second electrode on its surface; and a connecting portion connecting the first connecting member and the second connecting member. In the connecting structure of the present invention, the material of the connecting portion comprises the conductive particles. In the connecting structure of the present invention, the first electrode and the second electrode are electrically connected by means of the conductive particles.

[0209] Figure 4 is a cross-sectional view schematically showing the connection structure of the conductive particles using the first embodiment of the present invention.

[0210] The connecting structure 51 shown in FIG4 includes: a first connecting member 52, a second connecting member 53, and a connecting portion 54 connecting the first connecting member 52 and the second connecting member 53. The material of the connecting portion 54 includes conductive particles 1. The connecting portion 54 may also be formed of a conductive material containing conductive particles 1. Preferably, the connecting portion 54 is formed by hardening a conductive material containing a plurality of conductive particles 1. Furthermore, in FIG4, the conductive particles 1 are shown in a simplified diagram for ease of illustration. Conductive particles 21 or conductive particles 31 may also be used instead of conductive particles 1.

[0211] The first connecting member 52 has a plurality of first electrodes 52a on its surface (upper surface). The second connecting 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 connecting member 52 and the second connecting member 53 are electrically connected by the conductive portion 3 in the conductive particle 1.

[0212] The manufacturing method of the above-described connecting structure is not particularly limited. As an example of a manufacturing method for the connecting structure, a method may be given such that after obtaining a laminate by distributing the conductive material between a first connecting member and a second connecting member, the laminate is heated and pressurized. The pressure of the hot-pressing is preferably 40 MPa or more, more preferably 60 MPa or more, and more preferably 90 MPa or less, more preferably 70 MPa or less. The heating temperature of the hot-pressing is preferably 80°C or more, more preferably 100°C or more, and more preferably 140°C or less, more preferably 120°C or less. If the pressure and temperature of the hot-pressing are above the lower limit and below the upper limit, the insulating particles can easily detach from the surface of the conductive particles during conductive connection, thereby further improving the conductivity reliability between the electrodes.

[0213] When the above-mentioned laminate is heated and pressurized, the conductive particles and the insulating particles present between the first electrode and the second electrode can be eliminated. For example, during the heating and pressurization, the conductive particles and the insulating particles present between the first electrode and the second electrode easily detach from the surface of the conductive particles with attached insulating particles. Furthermore, during the heating and pressurization, sometimes a portion of the insulating particles detach from the surface of the conductive particles with attached insulating particles, thereby partially exposing the surface of the conductive portion. The exposed portion of the conductive portion contacts the first electrode and the second electrode, thereby electrically connecting the first electrode and the second electrode via the conductive particles.

[0214] The first and second connecting components described above are not particularly limited. Specifically, examples of the first and second connecting components include: electronic components such as semiconductor wafers, semiconductor packages, LED (Light Emitting Diode) wafers, LED packages, capacitors, and diodes; and electronic components such as circuit boards such as resin films, printed circuit boards, flexible printed circuit boards, flexible flat cables, rigid flexible substrates, glass epoxy resin substrates, and glass substrates. Preferably, the first and second connecting components are electronic components.

[0215] Examples of electrodes disposed on the aforementioned connecting member include: gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, SUS electrodes, and tungsten electrodes. When the connecting member is a flexible printed circuit board, the electrodes are preferably gold, nickel, tin, silver, or copper electrodes. When the connecting member is a glass substrate, the electrodes are preferably aluminum, copper, molybdenum, silver, or tungsten electrodes. Furthermore, when the electrode is an aluminum electrode, it can be an electrode formed solely of aluminum, or an electrode formed by depositing an aluminum layer 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 trivalent metal elements include: Sn, Al, and Ga.

[0216] Hereinafter, embodiments and comparative examples will be given to specifically describe the present invention. The present invention is not limited to the following embodiments.

[0217] (Example 1) (1) Formation of the first conductive part of the conductive particles: The substrate particle A is prepared as acrylic copolymer resin particles ("Micropearl EZ3P-020" manufactured by Sekisui Chemicals Co., Ltd., with an average particle size of 20 μm). Using an ultrasonic disperser, 10 parts by weight of substrate particle A are dispersed in 100 parts by weight of an alkaline solution containing 5% by weight of palladium catalyst solution, and the solution is filtered to remove substrate particle A. Then, substrate particle A is added to 100 parts by weight of a 1% by weight solution of dimethylamine borane to activate the surface of substrate particle A. After the surface-activated substrate particle A is thoroughly washed with water, it is added to 500 parts by weight of distilled water and dispersed to obtain a dispersion A containing substrate particle A. 1 g of nickel particle slurry (average particle size 100 nm) is added to dispersion A for 3 minutes to obtain a suspension A containing substrate particle A with attached core material.

[0218] Furthermore, the nickel plating solution is prepared as a nickel plating solution (pH 8.5) containing 0.14 mol / L nickel sulfate, 0.46 mol / L dimethylamine borane, and 0.2 mol / L sodium citrate.

[0219] The obtained suspension A was stirred at 70°C, and the above-mentioned nickel plating solution was added dropwise to suspension A at a rate of 30 mL / min for 10 minutes. Then, it was added dropwise at a rate of 10 mL / min for 40 minutes, and then at a rate of 4 mL / min for 80 minutes, thereby controlling the boron content absorbed into the plating film while performing electroless nickel-boron alloy plating.

[0220] Subsequently, the particles are removed by filtering the suspension A, washed with water and dried to obtain particles A with a first conductive part (conductive layer R, nickel layer, thickness 250 nm) disposed on the surface of the substrate particles A.

[0221] Formation of the second conductive part: By means of an ultrasonic processor, 10 parts by weight of the obtained particles A are dispersed in 500 parts by weight of ion-exchanged water to obtain suspension B.

[0222] Prepare a tin plating solution containing 15 g / L tin sulfate, 45 g / L ethylenediaminetetraacetic acid, and 1.5 g / L phosphonic acid (adjust the pH to 8.5 using sodium hydroxide). Also, prepare a reducing solution containing 5 g / L sodium borohydride (adjust the pH to 10.0 using sodium hydroxide).

[0223] While stirring the obtained suspension B at 50°C, the aforementioned tin plating solution was slowly added, and reduction was performed using a reducing solution to conduct electroless tin plating, thereby forming the second conductive part. Electroless tin plating was stopped when the thickness of the second conductive part reached 125 nm. Particles B with the second conductive part (conductive layer Q, tin layer, thickness 125 nm) disposed on the surface of the aforementioned first conductive part were obtained.

[0224] Formation of the third conductive part: The obtained particles B are dispersed into 500 parts by weight of ion-exchanged water by an ultrasonic processor to obtain a suspension C.

[0225] Prepare an indium plating solution (pH 10.0) containing 0.02 mol / L palladium sulfate, 0.04 mol / L ethylenediamine as a chelating agent, 5 g / L sodium borohydride as a reducing agent, and a crystallization adjuster.

[0226] While stirring the obtained suspension C at 50°C, the aforementioned indium plating solution was slowly added to perform electroless indium plating, forming the third conductive part. Electroless indium plating was stopped when the thickness of the third conductive part reached 125 nm. Conductive particles (before flux treatment) with the third conductive part (conductive layer P, indium layer, thickness 125 nm) disposed on the surface of the aforementioned second conductive part were obtained.

[0227] Flux Treatment: The obtained conductive particles were dispersed in 200 mL of ethanol to obtain a dispersion. Then, this dispersion was mixed with 300 mL of ethanol containing 0.5 g of flux, and the mixture was ultrasonically stirred at 50°C for 10 minutes. After filtration through a 3 μm sieve filter, the mixture was dried. Thus, conductive particles with a flux-treated outer surface were obtained.

[0228] (2) Preparation of conductive material: The following materials are mixed to obtain a mixture. 10 parts by weight of bisphenol A type epoxy resin (Epikote 1009 manufactured by Mitsubishi Chemical Co., Ltd.). 40 parts by weight of acrylic rubber (weight average molecular weight of about 800,000). 200 parts by weight of methyl ethyl ketone. 50 parts by weight of microencapsulated curing agent (HX3941HP manufactured by Asahi Kasei E-MATERIALS Co., Ltd.). 2 parts by weight of silane coupling agent (SH6040 manufactured by Dow Corning Toray Silicone Co., Ltd.). Conductive particles are added to the mixture until the content reaches 3% by weight, and then dispersed to obtain a conductive material.

[0229] The obtained conductive material was coated onto a 50 μm thick PET (polyethylene terephthalate) film that had undergone release treatment on one side, and dried with hot air at 70°C for 5 minutes to prepare an anisotropic conductive film. The thickness of the obtained anisotropic conductive film was 50 μm.

[0230] (3) Fabrication of the connecting structure: A polyimide substrate (flexible printed circuit board) with an Au electrode pattern (electrode (Au circuit): Ni / Au thin film on Cu) having an L / S of 200 μm / 200 μm is prepared on the upper surface. A printed circuit board with an Au electrode pattern (electrode (Au bump): Ni / Au thin film on Cu) having an L / S of 200 μm / 200 μm is also prepared on the lower surface. After attaching the obtained anisotropic conductive film to the upper surface of the polyimide substrate at 80°C and 0.98 MPa (10 kgf / cm2), the separator is peeled off. Then, the Au bumps of the printed circuit board and the Au circuit of the polyimide substrate are aligned. Subsequently, a pressure heating head is placed on the surface of the semiconductor wafer, applying a low pressure of 1 MPa calculated based on the pressing area, and the anisotropic conductive material layer is hardened at 160°C or the melting point of the conductive part of each conductive particle +20°C to obtain the connection structure.

[0231] (Examples 2-16 and Comparative Examples 1 and 2) The composition of the conductive parts and the presence or absence of flux treatment were modified as shown in Tables 1-4 below. Otherwise, the process was carried out in the same manner as in Example 1 to obtain conductive particles, conductive materials, and connection structures. Furthermore, in the tables, "content of conductive parts in 100% by weight" represents the content (by weight) of each of the first, second, third, and fourth conductive parts in 100% by weight of the conductive parts (total of the first, second, third, and fourth conductive parts), and "content of conductive particles in 100% by weight" represents the content (by weight) of each of the first, second, third, and fourth conductive parts in 100% by weight of the conductive particles.

[0232] (Evaluation) (1) Melting point of the entire conductive part: The melting point of the entire conductive part in the obtained conductive particles was determined by the above method.

[0233] (2) Diffusion coefficient For conductive particles with three or more conductive layers, the diffusion coefficient of conductive layer P relative to conductive layer Q at 160°C and the diffusion coefficient of conductive layer R relative to conductive layer Q at 160°C are obtained using the above method.

[0234] (3) X-ray diffraction spectroscopy: For the obtained conductive particles, the X-ray diffraction spectrum of the conductive part was measured using an X-ray diffraction device (RINT2500VHF manufactured by Rigaku Electric Co., Ltd.), and the presence or absence of peaks in the region between 32° and 34° and between 55.5° and 57.5° was observed. The measurement conditions for X-ray diffraction spectroscopy were set as follows: 45 kV, 50 mA, scan rate of 4.0 deg / min, scan step of 0.02 deg, and measurement range of 5.0 deg to 110.0 deg in terms of 2θ.

[0235] (4) Melting of the conductive part The obtained conductive particles are dispersed on a Cu plate and heated under atmospheric conditions at 1) 155°C for 1 minute, 2) 160°C for 1 minute, and 3) 200°C for 1 minute. The cross-section of the heated conductive particles is cut out using a FIB-SEM with a focused ion beam (FIB). After cutting out the cross-section, the melting state of the conductive part in the heated conductive particles is observed near the junction of the conductive particles and the Cu plate using an electron microscope (SEM). The thickness of the molten conductive part is determined and judged according to the following criteria. Furthermore, regarding the thickness of the molten conductive part, when observing the cross-section near the junction of the conductive particles and the Cu plate, the value obtained by dividing the area of ​​the molten conductive part by the length of the junction of the conductive particles and the Cu plate is the thickness of the molten conductive part.

[0236] [Criteria for Determining Melting of Conductive Parts] A: Melting occurs when the surface thickness of the conductive part is 30 nm or more. B: Melting occurs when the surface thickness of the conductive part exceeds 0 nm but does not reach 30 nm. C: Melting occurs when the surface of the conductive part does not melt.

[0237] (5) Conductivity Reliability (between upper and lower electrodes) For the 20 obtained connection structures (the connection structures were manufactured under conditions of 1) 160°C and 2) the melting point of the conductive part of each conductive particle +20°C, the connection resistance between the upper and lower electrodes was measured by the 4-terminal method. Furthermore, the connection resistance can be determined by measuring the voltage when a certain current flows through it, based on the relationship of voltage = current × resistance. Conductivity reliability was determined according to the following criteria.

[0238] [Conduction Reliability Judgment Criteria] A: Connection resistance is 0.35 Ω or less. B: Connection resistance exceeds 0.35 Ω but is 0.41 Ω or less. C: Connection resistance exceeds 0.41 Ω.

[0239] [Comprehensive Judgment Criteria for Conductivity Reliability] ○○: 1) A connection structure manufactured at 160℃, and 2) A connection structure manufactured at a temperature of +20℃ (the melting point of the conductive parts of each conductive particle). The judgment criterion for conductivity reliability is A or B. ○: 1) A connection structure manufactured at 160℃, and 2) A connection structure manufactured at a temperature of +20℃ (the melting point of the conductive parts of each conductive particle). The judgment criterion for conductivity reliability is A or B. ×: 1) A connection structure manufactured at 160℃, and 2) A connection structure manufactured at a temperature of +20℃ (the melting point of the conductive parts of each conductive particle). The judgment criterion for conductivity reliability is C.

[0240] The composition and results of the conductive particles are shown in Tables 1 to 4 below. In Tables 1 to 4, for example, "E-16" means "×10-16", "E-17" means "×10-17" (the same applies to numbers other than 16 and 17).

[0241] [Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Conductive part First conductive part type - Ni Ni Ni Ni Ni thickness nm 250 250 250 250 250 Melting point ℃ 1455 1455 1455 1455 1455 Content of conductive parts in 100% by weight weight% 52.9 52.9 67.4 67.4 51.9 Content of conductive particles in 100% by weight weight% 27 27 31 31 27 Second conductive part type - Sn Sn Sn Sn Sn thickness nm 125 125 125 125 200 Melting point ℃ 232 232 232 232 232 Content of conductive parts in 100% by weight weight% 23.5 23.5 29.3 29.3 38.5 Content of conductive particles in 100% by weight weight% 12 12 13.5 13.5 20 3rd conductive part type - In In In In In thickness nm 125 125 14 14 50 Melting point ℃ 157 157 157 157 157 Content of conductive parts in 100% by weight weight% 23.5 23.5 3.3 3.3 9.6 Content of conductive particles in 100% by weight weight% 12 12 1.5 1.5 5 4th conductive part type - - - - - - thickness nm - - - - - Melting point ℃ - - - - - Content of conductive parts in 100% by weight weight% - - - - - Content of conductive particles in 100% by weight weight% - - - - - The presence or absence of flux treatment - have none have none have melting point of the conductive part as a whole ℃ 118 118 150 150 190 The diffusion coefficient of conductive layer P relative to conductive layer Q at 160℃ m 2 / s 1.37E-16 1.37E-16 1.37E-16 1.37E-16 1.37E-16 The diffusion coefficient of conductive layer R relative to conductive layer Q at 160°C m 2 / s 2.73E-32 2.73E-32 2.73E-32 2.73E-32 2.73E-32 evaluate X-ray diffraction spectrum Areas between 32° and 34° - have have have have have Areas between 55.5° and 57.5° - have have have have have Melting of conductive parts 1) 1 minute at 155℃ - A A A C C 2) 1 minute at 160℃ - A A A A C 3) 1 minute at 200℃ - A A A A A On-state reliability 1) 160℃ - A B A B C 2) Melting point of the entire conductive part +20℃ - A B A B A Comprehensive judgment - 〇〇 〇〇 〇〇 〇〇 〇

[0242] [Table 2] Example 6 Example 7 Example 8 Example 9 Example 10 Conductive part First conductive part type - Ni Ni Ni Ni Ni thickness nm 250 250 250 250 250 Melting point ℃ 1455 1455 1455 1455 1455 Content of conductive parts in 100% by weight weight% 49.1 49.1 48.1 36.4 60.4 Content of conductive particles in 100% by weight weight% 26 26 26 16 29 Second conductive part type - Sn Sn Sn Sn Au thickness nm 118 118 175 175 20 Melting point ℃ 232 232 232 232 1064 Content of conductive parts in 100% by weight weight% 20.8 20.8 31.5 38.6 12.5 Content of conductive particles in 100% by weight weight% 11 11 17 17 6 3rd conductive part type - Bi Bi Bi Bi In thickness nm 130 130 90 90 125 Melting point ℃ 272 272 272 272 157 Content of conductive parts in 100% by weight weight% 30.2 30.2 20.4 25.0 27.1 Content of conductive particles in 100% by weight weight% 16 16 11 11 13 4th conductive part type - - - - - - thickness nm - - - - - Melting point ℃ - - - - - Content of conductive parts in 100% by weight weight% - - - - - Content of conductive particles in 100% by weight weight% - - - - - The presence or absence of flux treatment - have none have none have melting point of the conductive part as a whole ℃ 139 139 150 150 157 The diffusion coefficient of conductive layer P relative to conductive layer Q at 160℃ m 2 / s 7.77.E-17 7.77.E-17 7.77.E-17 7.77.E-17 7.13E-27 The diffusion coefficient of conductive layer R relative to conductive layer Q at 160°C m 2 / s 2.73E-32 2.73E-32 2.73E-32 2.73E-32 5.32E-28 evaluate X-ray diffraction spectrum Areas between 32° and 34° - none none none none have Areas between 55.5° and 57.5° - have have have have have Melting of conductive parts 1) 1 minute at 155℃ - A A A C C 2) 1 minute at 160℃ - A A A A C 3) 1 minute at 200℃ - A A A A A On-state reliability 1) 160℃ - A B B B C 2) The melting point of the entire conductive part is 20℃. - A B A B B Comprehensive judgment - 〇〇 〇〇 〇〇 〇〇 〇

[0243] [Table 3] Example 11 Example 12 Example 13 Example 14 Conductive part First conductive part type - Ni Ni Cu Cu thickness nm 250 250 250 250 Melting point ℃ 1455 1455 1085 1085 Content of conductive parts in 100% by weight weight% 49.1 45.5 53.8 50.0 Content of conductive particles in 100% by weight weight% 26 25 28 27 Second conductive part type - Au Au Sn Sn thickness nm 20 20 125 118 Melting point ℃ 1064 1064 232 232 Content of conductive parts in 100% by weight weight% 9.4 9.1 23.1 20.4 Content of conductive particles in 100% by weight weight% 5 5 12 11 3rd conductive part type Sn Sn In Bi thickness nm 125 118 125 130 Melting point ℃ 232 232 157 272 Content of conductive parts in 100% by weight weight% 20.8 18.2 23.1 29.6 Content of conductive particles in 100% by weight weight% 11 10 12 16 4th conductive part type - In Bi - - thickness nm 125 130 - - Melting point ℃ 157 272 - - Content of conductive parts in 100% by weight weight% 20.8 27.3 - - Content of conductive particles in 100% by weight weight% 11 15 - - The presence or absence of flux treatment have have have have melting point of the conductive part as a whole ℃ 118 139 118 139 The diffusion coefficient of conductive layer P relative to conductive layer Q at 160℃ m 2 / s 1.37E-16 7.77.E-17 1.37E-16 7.77.E-17 The diffusion coefficient of conductive layer R relative to conductive layer Q at 160°C m 2 / s 1.64E-12 1.64E-12 1.74E-27 1.74E-27 evaluate X-ray diffraction spectrum Areas between 32° and 34° - have none have none Areas between 55.5° and 57.5° - have have have have Melting of conductive parts 1) 1 minute at 155℃ - A A A A 2) 1 minute at 160℃ - A A A A 3) 1 minute at 200℃ - A A A A On-state reliability 1) 160℃ - A A A A 2) Melting point of the entire conductive part +20℃ - A A A A Comprehensive judgment - 〇〇 〇〇 〇〇 〇〇

[0244] [Table 4] Example 15 Example 16 Comparative Example 1 Comparative Example 2 Conductive part First conductive part type - Cu Zn Ni Ni thickness nm 250 250 250 250 Melting point ℃ 1085 420 1455 1455 Content of conductive parts in 100% by weight weight% 42.4 48.9 52.9 52.9 Content of conductive particles in 100% by weight weight% 25 twenty three 27 27 Second conductive part type - Ni Sn Sn Sn thickness nm 250 125 250 213 Melting point ℃ 1455 232 232 232 Content of conductive parts in 100% by weight weight% 39.0 25.5 47.1 39.2 Content of conductive particles in 100% by weight weight% twenty three 12 twenty four 20 3rd conductive part type - In In - In thickness nm 125 125 - 37 Melting point ℃ 157 157 - 157 Content of conductive parts in 100% by weight weight% 18.6 25.5 - 7.8 Content of conductive particles in 100% by weight weight% 11 12 - 4 4th conductive part type - - - - - thickness nm - - - - Melting point ℃ - - - - Content of conductive parts in 100% by weight weight% - - - - Content of conductive particles in 100% by weight weight% - - - - The presence or absence of flux treatment - have have have have melting point of the conductive part as a whole ℃ 157 190 233 210 The diffusion coefficient of conductive layer P relative to conductive layer Q at 160℃ m 2 / s 4.51E-32 1.37E-16 - 1.37E-16 The diffusion coefficient of conductive layer R relative to conductive layer Q at 160°C m 2 / s 4.38E-36 2.90E-17 - 2.73E-32 evaluate X-ray diffraction spectrum Areas between 32° and 34° - none have have have Areas between 55.5° and 57.5° - have have none have Melting of conductive parts 1) 1 minute at 155℃ - C C C C 2) 1 minute at 160℃ - C C C C 3) 1 minute at 200℃ - A A C C On-state reliability 1) 160℃ - C C C C 2) Melting point of the entire conductive part +20℃ - B B C C Comprehensive judgment - 〇 〇 × × [Simplified Explanation of the Diagram]

[0033] FIG1 is a cross-sectional view showing the conductive particles of the first embodiment of the present invention. FIG2 is a cross-sectional view showing the conductive particles of the second embodiment of the present invention. FIG3 is a cross-sectional view showing the conductive particles of the third embodiment of the present invention. FIG4 is a cross-sectional view schematically showing a connection structure using the conductive particles of the first embodiment of the present invention.

Claims

1. A conductive particle having a substrate particle and a conductive portion disposed on the surface of the substrate particle, wherein the conductive portion is a conductive layer of two or more layers, the outermost layer of the conductive portion has a thickness of 0.3 μm or less, the conductive portion contains tin, and the tin content in 100% by weight of the conductive portion is 38.6% by weight or less, and the conductive particle satisfies either configuration A or configuration B below: Configuration A: The conductive portion contains indium or bismuth, and the conductive portion melts when the conductive particle is heated at 160°C for 1 minute in an atmospheric atmosphere; Configuration B: The conductive portion contains three or more metals with different melting points, and the conductive portion melts when the conductive particle is heated at 200°C for 1 minute in an atmospheric atmosphere.

2. The conductive particles of claim 1, wherein the conductive portion comprises indium or bismuth, wherein when the conductive particles are heated at 160°C for 1 minute in an atmospheric atmosphere, the conductive portion melts.

3. The conductive particles of claim 1, wherein the conductive portion comprises indium, wherein when the conductive particles are heated at 160°C for 1 minute in an atmospheric atmosphere, the conductive portion melts.

4. The conductive particles of claim 1, wherein the conductive part comprises three or more metals with different melting points, wherein when the conductive particles are heated at 200°C in an atmospheric atmosphere for 1 minute, the conductive part melts.

5. The conductive particles of any one of claims 1 to 4, wherein the conductive part has a conductive layer with a melting point of 200°C or less, wherein the content of the conductive layer with a melting point of 200°C or less in 100% by weight of the conductive part is 10% by weight or more.

6. The conductive particles of any one of claims 1 to 4, wherein the conductive portion has a layer comprising copper or nickel, and the substrate particles are in contact with the layer comprising copper or nickel.

7. The conductive particles of any one of claims 1 to 4, wherein the tin content in 100% by weight of the aforementioned conductive portion is 2% by weight or more and 38.6% by weight or less.

8. The conductive particles of any one of claims 1 to 4, wherein the conductive portion comprises bismuth.

9. The conductive particles of any one of claims 1 to 4, wherein two or more conductive layers are deposited in such a manner that the melting point of the conductive layer gradually increases from the outer surface of the conductive part toward the inner surface.

10. The conductive particle according to any one of claims 1 to 4, wherein the conductive portion is a conductive layer of 3 or more layers, wherein the conductive portion has a conductive layer P, a conductive layer Q, and a conductive layer R in sequence from the outer surface of the conductive portion toward the inner side of the conductive portion in the thickness direction, wherein the conductive layer P is the outer surface layer of the conductive portion, wherein the conductive layer P, the conductive layer Q, and the conductive layer R are continuously deposited, and wherein the conductive portion has no conductive layer or has one or more conductive layers inside the conductive layer R.

11. The conductive particles of claim 10, wherein the diffusion coefficient of the conductive layer P relative to the conductive layer Q at 160°C is 1.0 × 10⁻²⁰ m² / s or more.

12. The conductive particles of claim 10, wherein the diffusion coefficient of the conductive layer R relative to the conductive layer Q at 160°C is less than 1.0 × 10⁻²⁵ m² / s.

13. The conductive particles of claim 10, wherein the materials of the conductive layer P and the conductive layer Q contain solder components.

14. The conductive particles of claim 10, wherein the conductive layer P is an indium layer containing indium, the conductive layer Q is a tin layer containing tin, and the conductive layer R is a nickel layer containing nickel.

15. The conductive particles of any one of claims 1 to 4, wherein when the X-ray diffraction spectrum of the conductive part is measured, peaks exist in the region between 32° and 34° and in the region between 55.5° and 57.5°.

16. The conductive particles of any one of claims 1 to 4, wherein the outer surface of the conductive part is surface treated with flux.

17. The conductive particles of any one of claims 1 to 4, wherein the particle size of the substrate particles is 0.5 μm or more and 100 μm or less.

18. A conductive material comprising: conductive particles as claimed in any one of claims 1 to 17, and an adhesive resin.

19. A connection structure comprising: a first connection member having a first electrode on its surface; a second connection member having a second electrode on its surface; and a connection portion connecting the first connection member and the second connection member, wherein the material of the connection portion comprises conductive particles as described in any one of claims 1 to 17, and the first electrode and the second electrode are electrically connected by the conductive particles.

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