CN108701508B

CN108701508B - Conductive particle, insulation-coated conductive particle, anisotropic conductive adhesive, connection structure, and method for producing conductive particle

Info

Publication number: CN108701508B
Application number: CN201780010792.2A
Authority: CN
Inventors: 赤井邦彦; 江尻芳则; 中川昌之; 山崎将平; 渡边靖
Original assignee: Hitachi Chemical Co Ltd
Current assignee: Lishennoco Co ltd
Priority date: 2016-02-10
Filing date: 2017-02-06
Publication date: 2020-03-24
Anticipated expiration: 2037-02-06
Also published as: JP6737293B2; TW201740391A; KR102649652B1; KR20180110021A; CN108701508A; JPWO2017138485A1; WO2017138485A1; TWI721096B

Abstract

Provided is a conductive particle which can achieve both excellent conduction reliability and insulation reliability when used as a conductive particle to be mixed in an anisotropic conductive adhesive. The conductive particle (100a) is provided with a composite particle (103) and a metal layer covering the composite particle (103), wherein the composite particle (103) comprises a resin particle (101) and a non-conductive inorganic particle (102) disposed on the surface of the resin particle (101). The metal layer has protrusions (109) on the outer surface thereof, the protrusions being formed by using the non-conductive inorganic particles (102) as cores. On the surface within a concentric circle of 1/2 diameters having the diameter of the resin particle (101), the non-conductive inorganic particles (102) have 40 or more and 200 or less first non-conductive inorganic particles (102a) having a diameter of less than 70nm, and have 5 or more and 50 or less second non-conductive inorganic particles (102b) having a diameter of 90nm or more and 150nm or less.

Description

Conductive particle, insulation-coated conductive particle, anisotropic conductive adhesive, connection structure, and method for producing conductive particle

Technical Field

The present invention relates to conductive particles, insulating coated conductive particles, anisotropic conductive adhesives, connection structures, and methods for producing conductive particles.

Background

The method of mounting the liquid crystal driving IC on the Glass panel for liquid crystal display can be roughly classified into two types, i.e., Chip-on-Glass (COG) mounting and Chip-on-Flex (COF) mounting. In COG mounting, a liquid crystal driving IC is directly bonded to a glass panel using an anisotropic conductive adhesive containing conductive particles. On the other hand, in COF mounting, a liquid crystal driving IC is bonded to a flexible tape having metal wiring, and these are bonded to a glass panel using an anisotropic conductive adhesive containing conductive particles. The term "anisotropic" as used herein means conducting in the direction of pressure and maintaining insulation in the direction of non-pressure.

Conventionally, as conductive particles, conductive particles having a gold layer on the surface have been used. The conductive particles having a gold layer on the surface are advantageous in that the resistance value is low. Since gold is less likely to be oxidized, even when the conductive particles having a gold layer on the surface thereof are stored for a long period of time, the conductive particles can be prevented from increasing in resistance value.

In recent years, in order to suppress power consumption during liquid crystal driving in response to energy saving, it has been studied to reduce the amount of current flowing through a liquid crystal driving IC. Therefore, conductive particles that can achieve a lower resistance value than ever are required. In recent years, the price of noble metals has increased, and therefore, it has been demanded to reduce the resistance value by using conductive particles not using noble metals.

For example, patent documents 1 to 3 listed below disclose conductive particles that use only nickel without using a noble metal and have a low resistance value. Specifically, patent document 1 describes the following method: conductive particles having conductive protrusions on the surface are produced by forming fine protrusions of nickel and a nickel coating film simultaneously on nonconductive particles by self-decomposition of a nickel plating solution in an electroless nickel plating method. Patent document 2 describes the following method: after a conductive material serving as a core material is attached to the surface of base fine particles, electroless nickel plating is performed on the base fine particles, thereby producing conductive particles having conductive protrusions on the surface. Patent document 3 describes the following method: after a non-conductive substance serving as a core material is adsorbed on the surface of base fine particles by chemical bonding, electroless nickel plating is performed on the base fine particles, thereby producing conductive particles having conductive protrusions on the surface.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5184612

Patent document 2: japanese patent No. 4674096

Patent document 3: japanese patent No. 4640531

Disclosure of Invention

Problems to be solved by the invention

When a chip is mounted by using an anisotropic conductive adhesive, it is necessary to reduce the on-resistance between electrodes connected and sufficiently increase the insulation resistance between adjacent electrodes of the chip. In recent years, the pad area of the electrode has become smaller, and the number of particles trapped between the electrodes has become smaller, so that it has been required to uniformly reduce the on-resistance of the particles one by one. The connection structure using the anisotropic conductive adhesive containing the conductive particles described in patent documents 1 to 3 exhibits a sufficient connection resistance value at the initial stage of connection. However, when these connection structures are stored under high temperature and high humidity conditions, the connection resistance value may increase. Further, in the connection structure using the anisotropic conductive adhesive containing the conductive particles described in patent documents 1 to 3, although a sufficient insulation resistance value is exhibited at the initial stage of connection, the insulation resistance value may be lowered after a migration test of conduction is performed for a long period of time under high temperature and high humidity.

An object of one aspect of the present invention is to provide conductive particles that can achieve both excellent conduction reliability and insulation reliability when used as conductive particles to be mixed in an anisotropic conductive adhesive, and a method for producing the same. Another object of the present invention is to provide an insulating coated conductive particle using the conductive particle, an anisotropic conductive adhesive, and a connection structure.

Means for solving the problems

The conductive particle according to one aspect of the present invention includes a composite particle including a resin particle and a nonconductive inorganic particle disposed on a surface of the resin particle, and a metal layer covering the composite particle, the metal layer having protrusions on an outer surface thereof with the nonconductive inorganic particle as a core, the nonconductive inorganic particle having 40 or more and 200 or less first nonconductive inorganic particles having a diameter of 70nm or less and 5 or more and 50 or more second nonconductive inorganic particles having a diameter of 90nm or more and 150nm or less on a surface within a concentric circle of 1/2 diameters of the resin particle.

According to the conductive particles, the size and number of the protrusions formed using the non-conductive inorganic particles as cores can be controlled within an appropriate range. Therefore, the protrusions of the conductive particles have a size (height) to be able to stably contact with an electrode surface or the like to be connected. In addition, the number of extremely large (tall) protrusions in the conductive particles can be reduced, and the distance between the conductive particles can be kept constant. Further, the nonconductive inorganic particles serving as the core of the protrusions suppress aggregation of the resin particles, and the conductive particles have good dispersibility. Therefore, by blending the conductive particles in the anisotropic conductive adhesive, excellent conduction reliability and insulation reliability can be highly achieved at the same time.

The number of the first non-conductive inorganic particles may be greater than or equal to 2 times the number of the second non-conductive inorganic particles at the surface within a concentric circle of 1/2 diameters having the diameter of the resin particle. In this case, the presence of the second nonconductive inorganic particles larger than the first nonconductive inorganic particles makes it easy to suppress the aggregation of the resin particles with each other. Thus, conductive particles having excellent monodispersity are easily obtained, and conductive particles having more stable insulation reliability tend to be obtained. Further, the larger protrusions formed of the second nonconductive inorganic particles tend to ensure more stable connection reliability.

The first non-conductive inorganic particles may have an average particle size in a range of 25 to 70nm and a coefficient of variation of less than 20%, and the second non-conductive inorganic particles may have an average particle size in a range of 90 to 130nm and a coefficient of variation of less than 20%. In this case, the performance required for each of the first nonconductive inorganic particles and the second nonconductive inorganic particles can be sufficiently exhibited. In addition, since the non-conductive inorganic particles have small variations in average particle diameter, the shapes (height, area, etc.) of the protrusions on the surfaces of the conductive particles are easily uniform. Thus, for example, when the conductive particles are deformed between the counter electrodes, the protrusions are likely to be in uniform contact with the electrodes, and more stable conduction reliability tends to be obtained. Further, since the variation in height of the protrusions is reduced, the variation in distance between the conductive particles present between adjacent electrodes is reduced, and more stable insulation reliability tends to be obtained.

The conductive particle according to another aspect of the present invention is a conductive particle including a composite particle and a metal layer covering the composite particle, the composite particle comprises a resin particle and a non-conductive inorganic particle disposed on the surface of the resin particle, wherein the metal layer has a protrusion on the outer surface thereof with the non-conductive inorganic particle as a core, a surface within a concentric circle of 1/2 diameters having a diameter of the conductive particle, a surface within a concentric circle of 1/2 diameters having a diameter of the conductive particle, the protrusions having greater than or equal to 20 first protrusions of 50nm or greater and less than 100nm in diameter, having greater than or equal to 20 second protrusions of 100nm or greater and less than 200nm in diameter, and has 5 or more and 20 or less third protrusions having a diameter of 200nm or more and 350nm or less.

The surface of the non-conductive inorganic particle may be coated with a hydrophobic treatment agent. In this case, the interfacial potential of the surface of the non-conductive inorganic particle is shifted to the negative side by hydrophobization. Thus, for example, when the interfacial potential on the surface of the resin particle is a positive number, electrostatic force acts between the resin particle and the non-conductive inorganic particle, and the non-conductive inorganic particle is less likely to fall off from the resin particle.

The hydrophobizing agent may be selected from the group consisting of a silicon nitride-based hydrophobizing agent, a silicone-based hydrophobizing agent, a silane-based hydrophobizing agent, and a titanate-based hydrophobizing agent.

The hydrophobizing treatment agent may be selected from the group consisting of hexamethyldisilazane, polydimethylsiloxane, and N, N-dimethylaminotrimethylsilane.

The degree of hydrophobization of the non-conductive inorganic particles obtained by the methanol titration method may be 30% or more. In this case, a sufficient electrostatic force acts between the nonconductive inorganic particles and the resin particles.

The difference in the interfacial potential between the resin particles and the non-conductive inorganic particles may be greater than or equal to 30mV at a pH greater than or equal to 1 and a pH less than or equal to 11. In this case, the resin particles and the non-conductive inorganic particles are strongly bonded by electrostatic force. Therefore, the non-conductive inorganic particles can be suitably inhibited from falling off from the resin particles in a pretreatment step for forming the metal layer in the conductive particles, a step for forming the metal layer, and the like.

The surface of the resin particle may be coated with a cationic polymer. In this case, electrostatic force acts between the resin particles and the non-conductive inorganic particles, so that the non-conductive inorganic particles are less likely to fall off from the resin particles.

The cationic polymer may be selected from the group consisting of polyamine, polyimine, polyamide, polydiallyldimethylammonium chloride, polyvinylamine, polyvinylpyridine, polyvinylimidazole, and polyvinylpyrrolidone.

The cationic polymer may also be polyethyleneimine. In this case, since the charge density of the cationic polymer is high, the non-conductive inorganic particles can be favorably prevented from falling off.

The non-conductive inorganic particles may be adhered to the resin particles by electrostatic force.

The average particle diameter of the resin particles may be 1 μm or more and 10 μm or less. In this case, for example, when a connection structure is produced using an anisotropic conductive adhesive containing conductive particles, the conductivity and the like of the anisotropic conductive adhesive are less likely to change due to variations in the shape (height) of the electrodes of the connection structure.

The non-conductive inorganic particles may be selected from the group consisting of silica, zirconia, alumina, and diamond.

The metal layer may have a first layer containing nickel. In this case, the hardness of the conductive particles can be increased. Thus, even when the conductive particles are compressed, the first layer formed on the non-conductive inorganic particles and serving as the protruding portion is not easily crushed. Therefore, the conductive particles can obtain a low on-resistance.

The metal layer may also have a second layer disposed on the first layer, and the second layer contains a metal selected from the group consisting of noble metals and cobalt. In this case, the conductive particles can obtain a lower on-resistance.

An insulation-coated conductive particle according to another aspect of the present invention includes the conductive particle and an insulation coating portion that coats at least a part of an outer surface of a metal layer of the conductive particle.

According to the insulated coated conductive particle, the metal layers of the insulated coated conductive particle are less likely to contact each other by the insulating coating portion provided on the outer surface of the metal layer. Thus, when the insulating coated conductive particles are mixed in the anisotropic conductive adhesive, the insulating coated conductive particles are less likely to conduct electricity with each other, and the insulation reliability of a connection structure or the like using the insulating coated conductive particles is suitably improved. Therefore, by blending the insulating coated conductive particles with an anisotropic conductive adhesive, more excellent conduction reliability and insulation reliability can be achieved at the same time.

A connection structure according to another aspect of the present invention includes: the first circuit member includes a first circuit electrode, a second circuit member facing the first circuit member and including a second circuit electrode, and a connecting portion disposed between the first circuit member and the second circuit member and including the conductive particles, the connecting portion connecting the first circuit member and the second circuit member to each other in a state where the first circuit electrode and the second circuit electrode are disposed to face each other, the first circuit electrode and the second circuit electrode being electrically connected to each other by the conductive particles in a deformed state.

According to this connection structure, the protrusions having an appropriate size are formed, the nonconductive inorganic particles suppress aggregation of the resin particles, and the first circuit electrode and the second circuit electrode are electrically connected to each other by the conductive particles dispersed well in the connection portion, so that excellent conduction reliability and insulation reliability can be highly achieved at the same time.

A connection structure according to another aspect of the present invention includes: the first circuit member has a first circuit electrode, a second circuit member facing the first circuit member and having a second circuit electrode, and a connecting portion disposed between the first circuit member and the second circuit member and containing the insulating coated conductive particles, wherein the connecting portion connects the first circuit member and the second circuit member to each other in a state where the first circuit electrode and the second circuit electrode are disposed so as to face each other, and the first circuit electrode and the second circuit electrode are electrically connected to each other by the insulating coated conductive particles in a deformed state.

According to this connection structure, the protrusions having an appropriate size are formed, and the nonconductive inorganic particles suppress aggregation of the resin particles with each other, and the first circuit electrode and the second circuit electrode are electrically connected to each other by the insulating coated conductive particles which are well dispersed in the connection portion. In addition, the insulating coating portion provided on the outer surface of the metal layer in the insulating coated conductive particle further improves the insulation reliability of the connection portion, and thus, excellent conduction reliability and insulation reliability can be more highly satisfied.

An anisotropic conductive adhesive according to another aspect of the present invention includes the conductive particles and an adhesive in which the conductive particles are dispersed.

According to the anisotropic conductive adhesive, the conductive particles having the protrusions formed therein with an appropriate size are well dispersed in the adhesive while suppressing aggregation by the non-conductive inorganic particles, and therefore, excellent conduction reliability and insulation reliability can be highly satisfied at the same time.

An anisotropic conductive adhesive according to another aspect of the present invention includes the insulating coated conductive particles and an adhesive in which the insulating coated conductive particles are dispersed.

According to the anisotropic conductive adhesive, the conductive particles formed with the protrusions having an appropriate size are well dispersed in the adhesive while suppressing aggregation by the non-conductive inorganic particles. Further, the insulating reliability is further improved by the insulating coating portion provided on the outer surface of the metal layer, and therefore, excellent conduction reliability and insulating reliability can be more highly satisfied.

In the anisotropic conductive adhesive, the adhesive may be in the form of a film.

A connection structure according to another aspect of the present invention includes: the adhesive for bonding the first circuit member and the second circuit member to each other is characterized by comprising a first circuit member having a first circuit electrode, a second circuit member facing the first circuit member and having a second circuit electrode, and the anisotropic conductive adhesive bonding the first circuit member and the second circuit member to each other.

According to this connection structure, the first circuit member and the second circuit member are electrically connected to each other by the anisotropic conductive adhesive, whereby excellent conduction reliability and insulation reliability can be achieved at the same time.

A method for producing conductive particles according to another aspect of the present invention is a method for producing conductive particles including composite particles and a metal layer covering the composite particles, the composite particles including resin particles and non-conductive inorganic particles disposed on surfaces of the resin particles, the method for producing conductive particles including: disposing nonconductive inorganic particles on the surface of the resin particles to form composite particles; and a step of covering the composite particles with a metal layer, wherein in the step of forming the composite particles, 40 or more and 200 or less first nonconductive inorganic particles having a diameter of 70nm or less are arranged on the surface of a concentric circle having a diameter of 1/2 of the diameter of the resin particles, and 5 or more and 50 or less second nonconductive inorganic particles having a diameter of 90nm or more and 150nm or less are arranged.

The number of the first non-conductive inorganic particles may be greater than or equal to 2 times the number of the second non-conductive inorganic particles at the surface within a concentric circle of 1/2 diameters having the diameter of the resin particle. In this case, the presence of the second nonconductive inorganic particles larger than the first nonconductive inorganic particles makes it easy to suppress the aggregation of the resin particles with each other. Thus, conductive particles having excellent monodispersity are easily obtained, and conductive particles having more stable insulation reliability tend to be obtained. Further, by using larger protrusions formed of the second nonconductive inorganic particles, it is also easy to ensure more stable connection reliability.

In the step of covering the composite particles with the metal layer, protrusions having the non-conductive inorganic particles as cores are formed on the outer surface of the metal layer, and on the surface of the metal layer within a concentric circle of 1/2 diameters having the diameter of the conductive particles, there may be 20 or more first protrusions having a diameter of 50nm or more and less than 100nm, 20 or more second protrusions having a diameter of 100nm or more and less than 200nm, and 5 or more and less than 20 third protrusions having a diameter of 200nm or more and 350nm or less. In this case, the protrusions of the conductive particles are formed to have a size (height) sufficient to stably contact an electrode surface or the like to be connected, and more excellent conduction reliability tends to be obtained. Further, the number of extremely large (high) protrusions can be reduced, the distance between the conductive particles can be kept constant, and more stable insulation reliability tends to be obtained.

The above manufacturing method may further include: a first coating step of coating resin particles with a cationic polymer; and a second coating step of coating the non-conductive inorganic particles with a hydrophobizing agent, wherein in the step of forming the composite particles, the non-conductive inorganic particles are bonded to the surfaces of the resin particles by electrostatic force, and the difference in the interfacial potential between the resin particles and the non-conductive inorganic particles is 30mV or more at a pH of 1 or more and 11 or less. In this case, the resin particles and the non-conductive inorganic particles are strongly bonded by electrostatic force. Therefore, in the step of covering the composite particles with the metal layer, the non-conductive inorganic particles can be suitably prevented from falling off from the resin particles.

In the step of covering the composite particles with the metal layer, the composite particles may be covered with the first layer containing nickel by electroless plating. Thus, even when the conductive particles are compressed, the first layer formed on the non-conductive inorganic particles and serving as the protruding portion is not easily crushed. Therefore, the conductive particles can obtain a low on-resistance.

In the step of covering the composite particles with the metal layer, the composite particles covered with the first layer may be covered with a second layer containing a metal selected from the group consisting of noble metals and cobalt. In this case, the conductive particles can obtain a lower on-resistance.

Effects of the invention

According to an aspect of the present invention, there is provided conductive particles capable of achieving both excellent conduction reliability and insulation reliability when used as conductive particles to be blended in an anisotropic conductive adhesive, and a method for producing the same. In addition, according to an aspect of the present invention, there are provided an insulating coated conductive particle using the conductive particle, an anisotropic conductive adhesive, and a connection structure.

Drawings

Fig. 1 is a schematic cross-sectional view showing conductive particles according to embodiment 1.

Fig. 2 is a schematic enlarged cross-sectional view illustrating the conductive particle according to embodiment 1.

Fig. 3 is a schematic cross-sectional view showing conductive particles according to embodiment 2.

Fig. 4 is a schematic enlarged cross-sectional view illustrating the conductive particle according to embodiment 2.

Fig. 5 is a schematic cross-sectional view showing the insulated coated conductive particle according to embodiment 3.

Fig. 6 is a schematic cross-sectional view showing a connection structure according to embodiment 5.

Fig. 7 is a schematic cross-sectional view for explaining an example of the method of manufacturing the connection structure according to embodiment 5.

Fig. 8 is an SEM image of particles obtained in step d in the production of conductive particles of example 1.

Fig. 9 is an SEM image of the surface of the particle obtained in step d in the production of the conductive particle of example 1.

Fig. 10 is an SEM image of particles obtained in step f in the production of conductive particles of example 1.

Fig. 11 is an SEM image of the surface of the particle obtained in step f in the production of the conductive particle of example 1.

Fig. 12 is a schematic view for explaining the trimming process.

Fig. 13 is a schematic diagram for explaining a method of preparing a thin film slice for TEM measurement.

FIG. 14 is a schematic view for explaining an abnormal precipitation portion.

Fig. 15 is an SEM image of particles obtained by impregnating resin particles to which a palladium catalyst is fixed and ultrasonically dispersing the resin particles in comparative example 6.

Fig. 16 is an SEM image of conductive particles observed after the b layer of the first layer was formed in comparative example 6.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and redundant description thereof is omitted. The positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios of the drawings are not limited to the illustrated ratios.

(embodiment 1)

The conductive particles according to embodiment 1 will be described below.

< conductive particles >

Fig. 1 is a schematic cross-sectional view showing conductive particles according to embodiment 1. The conductive particle 100a shown in fig. 1 includes a composite particle 103 and a first layer 104 covering the composite particle 103, and the composite particle 103 includes a resin particle 101 constituting a core of the conductive particle and a nonconductive inorganic particle 102 disposed on a surface of the resin particle 101. The protrusions 109 are formed on the outer surface of the first layer 104 so as to reflect the shape of the non-conductive inorganic particles 102 adhering to the resin particles 101. The resin particles 101 are coated with a cationic polymer described later. The non-conductive inorganic particles 102 are coated with a hydrophobic treatment agent described later, and include first non-conductive inorganic particles 102a and second non-conductive inorganic particles 102 b. The first layer 104 is a conductive layer containing at least a metal. The first layer 104 may be a metal layer or an alloy layer.

The average particle diameter of the conductive particles 100a may be, for example, 1 μm or more, or 2 μm or more. The average particle diameter of the conductive particles 100a may be, for example, 10 μm or less, or 5 μm or less. That is, the conductive particles 100a have an average particle diameter of, for example, 1 to 10 μm. When the average particle diameter of the conductive particles 100a is within the above range, for example, in the case of manufacturing a connection structure using an anisotropic conductive adhesive containing the conductive particles 100a, the conductivity and the like of the anisotropic conductive adhesive are less likely to change due to variations in the shape (height) of the electrode of the connection structure. The average particle diameter of the conductive particles 100a may be an average value obtained by: the particle size of 300 arbitrary conductive particles was measured by observation using a scanning electron microscope (hereinafter referred to as "SEM"). Since the conductive particles 100a have the protrusions 109, the particle diameter of the conductive particles 100a is set to the diameter of a circle circumscribing the conductive particles 100a in an image captured by SEM. In order to measure the average particle diameter of the conductive particles 100a with improved accuracy, a commercially available device such as a coulter counter can be used. In this case, if the particle size of 50000 conductive particles is measured, the average particle size can be measured with high accuracy. For example, the average particle diameter of the conductive particles 100a can be measured by measuring 50000 conductive particles using coulter mulisizer II (product name, manufactured by beckmann coulter corporation).

< resin particles >

The resin particles 101 are made of an organic resin. As the organic resin, there may be mentioned: (meth) acrylic resins such as polymethyl methacrylate and polymethyl acrylate; polyolefin resins such as polyethylene and polypropylene; a polyisobutylene resin; polybutadiene resins, and the like. As the resin particles 101, particles obtained by crosslinking an organic resin, such as crosslinked (meth) acrylic acid particles and crosslinked polystyrene particles, may be used. The resin particles may be composed of one of the organic resins described above, or may be composed of a combination of two or more of the organic resins described above. The organic resin is not limited to the above resins.

The resin particles 101 are spherical. The average particle diameter of the resin particles 101 may be, for example, 1 μm or more and 10 μm or less. The average particle diameter of the resin particles 101 may be, for example, 1 μm or more, or 2 μm or more. The deformation amount of the conductive particles 100a can be sufficiently secured by setting the average particle diameter of the resin particles 101 to 1 μm or more. The average particle diameter of the resin particles 101 may be, for example, 10 μm or less, or 5 μm or less. By setting the average particle diameter of the resin particles 101 to 10 μm or less, variation in particle diameter can be suppressed, and variation in connection resistance value of the conductive particles 100a can be suppressed. The average particle diameter of the resin particles 101 is an average value obtained by: the particle size of 300 resin particles was arbitrarily determined by observation using SEM.

< surface treatment of resin particles >

As described above, the resin particles 101 are coated with a cationic polymer as a surface treatment. The cationic polymer is generally a polymer compound having a functional group capable of positively charging, such as polyamine. The cationic polymer may be selected from the group consisting of polyamine, polyimine, polyamide, polydiallyldimethylammonium chloride, polyvinylamine, polyvinylpyridine, polyvinylimidazole, and polyvinylpyrrolidone, for example. From the viewpoint of high charge density and strong bonding force with a surface and a material having negative charges, polyimide is preferable, and polyethyleneimine is more preferable. The cationic polymer is preferably soluble in water or a mixed solution of water and an organic solvent. The molecular weight of the cationic polymer varies depending on the kind of the cationic polymer to be used, and is, for example, about 500 to 200000.

The coating rate of the non-conductive inorganic particles 102 on the resin particles 101 can be controlled by adjusting the kind and molecular weight of the cationic polymer. Specifically, when the resin particles 101 are coated with a cationic polymer having a high charge density such as polyethyleneimine, the coating rate of the non-conductive inorganic particles 102 (the ratio of the non-conductive inorganic particles 102 to the resin particles 101) tends to be high. On the other hand, when the resin particles 101 are coated with a cationic polymer having a low charge density, the coverage of the non-conductive inorganic particles 102 tends to decrease. When the molecular weight of the cationic polymer is large, the coverage of the non-conductive inorganic particles 102 tends to be high, and when the molecular weight of the cationic polymer is small, the coverage of the non-conductive inorganic particles 102 tends to be low.

The cationic polymer may be substantially free of alkali metal (Li, Na, K, Rb, Cs) ions, alkaline earth metal (Ca, Sr, Ba, Ra) ions, and halide ions (fluoride, chloride, bromide, iodide). In this case, electromigration and corrosion of the resin particles 101 coated with the cationic polymer can be suppressed.

The resin particle 101 before being coated with the cationic polymer has a functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an alkoxy group, a glycidyl group, and an alkoxycarbonyl group on the surface. This allows the cationic polymer to be easily adsorbed on the surface of the resin particle 101.

The interfacial potential of the resin particle 101 coated with the cationic polymer is preferably positive (positive) in all of water, an organic solvent, or a mixed solution containing water and an organic solvent. Generally, the lower the pH, the more positive the interfacial potential of the particles. Therefore, the pH of the plating solution for forming the first layer 104 and the pretreatment solution used in the pretreatment step for plating is preferably controlled to 6 or less.

The interface potential of the resin particle 101 can be measured, for example, by: the colloidal vibration potential was measured using a Dada potential probe (trade name "DT 300" manufactured by Dispersion Technologies), or the electrophoretic mobility was measured by laser Doppler velocimetry using a Zetasizer ZS (trade name manufactured by Malvern Instruments).

< non-conductive inorganic particles >

As described later, the non-conductive inorganic particles 102 are strongly adhered to the resin particles 101 by electrostatic force. The shape of the non-conductive inorganic particles 102 is not particularly limited, and is an ellipsoid, a sphere, a hemisphere, a substantially ellipsoid, a substantially sphere, a substantially hemisphere, or the like. Of these shapes, an ellipsoid or a sphere is preferable.

The coating rate of the non-conductive inorganic particles 102 with respect to the resin particles 101 may be 20% to 80% before the first layer 104 is formed and after a pretreatment (described in detail later) in the formation of the first layer 104 is completed. From the viewpoint of more reliably obtaining the effects of the insulation property and the conductivity of the conductive particles 100a, the coverage may be 25% or more, 30% or more, 70% or less, or 60% or less. In the present embodiment, the "coverage" refers to a ratio of the surface area of the non-conductive inorganic particles 102 in a concentric circle having a diameter of 1/2 of the diameter of the resin particle 101 on the orthographic projection surface of the resin particle 101. Specifically, the image obtained by observing the resin particle 101 on which the non-conductive inorganic particles 102 are formed by SEM at 3 ten thousand times was analyzed, and the ratio of the non-conductive inorganic particles 102 to the surface of the resin particle 101 was calculated.

The non-conductive inorganic particles 102 may be disposed in a direction (surface) perpendicular to the radial direction of the conductive particles 100a in a scattered manner from the viewpoint of forming a sufficient number of protrusions 109 on the outer surface of the first layer 104 and further reducing the on-resistance when the conductive particles 100a are connected to an electrode or the like. The non-conductive inorganic particles 102 may be disposed in a direction (surface) perpendicular to the radial direction of the conductive particles 100a in a dispersed manner without contacting each other. The number of the non-conductive inorganic particles 102 that are in contact with each other may be, for example, 20 or less, 7 or less, or 0 in one conductive particle 100 a. The number 0 means that the non-conductive inorganic particles 102 disposed on the surface of one conductive particle 100a do not contact each other, and all the non-conductive inorganic particles 102 are disposed in a scattered manner.

The material forming the non-conductive inorganic particles 102 may be harder than the material forming the first layer 104. This makes it easy for the conductive particles to penetrate the electrode and the like, thereby improving conductivity. Namely, the idea is: instead of hardening the entire conductive particles, a part of the conductive particles is hardened. For example, the material forming the non-conductive inorganic particles 102 has a mohs hardness greater than the mohs hardness of the metal forming the first layer 104. Specifically, the material forming the non-conductive inorganic particles 102 has a mohs hardness of 5 or more. Also, the difference between the mohs hardness of the material forming the non-conductive inorganic particles 102 and the mohs hardness of the metal forming the first layer 104 may be greater than or equal to 1.0. In the case where the first layer 104 contains a plurality of metals, the mohs hardness of the non-conductive inorganic particles 102 may also be higher than the mohs hardness of all the metals. As a specific example, the material forming the non-conductive inorganic particles 102 may be selected from silicon dioxide (SiO)₂) 6-7 Mohs hardness), zirconia (8-9 Mohs hardness), alumina (9 Mohs hardness) and diamond (10 Mohs hardness). Hydroxyl groups (-OH) are formed on the surfaces of the nonconductive inorganic particles 102, and are coated with the hydrophobizing agent as described above. The above Mohs hardness is referred to "chemical dictionary" (published by Kyoto Press).

As the non-conductive inorganic particles 102, silica particles may also be used. The particle diameter of the silica particles is preferably controlled. The type of the silica particles is not particularly limited, and examples thereof include colloidal silica, fumed silica, and sol-gel silica. The silica particles may be used alone or in combination of two or more. As the silica particles, commercially available products or synthetic products may be used.

As a method for producing colloidal silica, a known method can be cited. Specific examples thereof include: the method of hydrolysis using an alkoxysilane described in "science of sol-gel method" (published by AGNE Kagaku corporation, pp.154 to 156); a method of adding methyl silicate or a mixture of methyl silicate and methanol dropwise to a mixed solvent containing water, methanol, and ammonia or a mixture of ammonia and an ammonium salt to react methyl silicate with water, as described in japanese unexamined patent publication No. 11-60232; a method of hydrolyzing an alkylsilicate with an acid catalyst, adding an alkali catalyst, heating, and polymerizing silicic acid to grow particles, which is described in Japanese patent laid-open No. 2001-48520; a method of using a specific type of hydrolysis catalyst in a specific amount in the hydrolysis of alkoxysilane described in Japanese patent laid-open No. 2007-153732. Alternatively, a method of producing sodium silicate by ion exchange may be mentioned. Commercially available products of water-dispersible colloidal silica include: snowtex, Snowtex UP (trade name, manufactured by Nissan chemical industries Co., Ltd.), Quartron PL series (trade name, manufactured by Hibiscus chemical industries Co., Ltd.), and the like.

Examples of the method for producing fumed silica include: a known method of gas phase reaction in which silicon tetrachloride is gasified and burned in an oxyhydrogen flame is used. Further, the fumed silica can be made into an aqueous dispersion by a known method. As a method for preparing an aqueous dispersion, there can be mentioned the methods described in, for example, Japanese patent application laid-open Nos. 2004-43298, 2003-176123 and 2002-309239. From the viewpoint of insulation reliability of fumed silica, the concentration of alkali metal ions and alkaline earth metal ions in the aqueous dispersion is preferably 100ppm or less. The fumed silica can have a mohs hardness of greater than or equal to 5 and can also have a mohs hardness of greater than or equal to 6.

< hydrophobizing agent >

Examples of the hydrophobizing agent for coating the non-conductive inorganic particles 102 include (1) a silazane-based hydrophobizing agent, (2) a siloxane-based hydrophobizing agent, (3) a silane-based hydrophobizing agent, and (4) a titanate-based hydrophobizing agent, which are described below. From the viewpoint of reactivity, (1) a silazane-based hydrophobizing agent is preferable. The hydrophobizing agent may contain at least one selected from the group consisting of the above (1) to (4).

(1) Silicon-nitrogen-alkane-based hydrophobizing agent

Examples of the silazane-based hydrophobizing agent include organic silazane-based hydrophobizing agents. Examples of the organic silazane-based hydrophobizing agent include: hexamethyldisilazane, trimethyldisilazane, tetramethyldisilazane, hexamethylcyclotrisilazane, heptamethyldisilazane, diphenyltetramethyldisilazane, divinyltetramethyldisilazane, and the like. The organic silazane-based hydrophobizing agent may be a compound other than the above.

(2) Silicone-based hydrophobizing agent

Examples of the silicone-based hydrophobizing agent include: polydimethylsiloxane, methylhydrogen disiloxane, dimethyldisiloxane, hexamethyldisiloxane, 1, 3-divinyltetramethyldisiloxane, 1, 3-diphenyltetramethyldisiloxane, methylhydrogen polysiloxane, dimethylpolysiloxane, amino-modified siloxane and the like. The silicone-based hydrophobizing agent may be a compound other than the above.

(3) Silane-based hydrophobizing agent

Examples of the silane-based hydrophobizing agent include N, N-dimethylaminotrimethylsilane, trimethylmethoxysilane, trimethylethoxysilane, trimethylpropoxysilane, phenyldimethylmethoxysilane, chloropropyldimethylmethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, ethyltrimethoxysilane, dimethyldiethoxysilane, propyltriethoxysilane, N-butyltrimethoxysilane, N-hexyltrimethoxysilane, N-octyltriethoxysilane, N-octylmethyldiethoxysilane, N-octadecyltrimethoxysilane, phenyltrimethoxysilane, phenylmethyldimethoxysilane, phenylethyltrimethoxysilane, dodecyltrimethoxysilane, N-octadecyltriethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β methoxyethoxy) silane, gamma-methacryloxypropyltrimethoxysilane, gamma-acryloyloxypropyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, gamma- (methacryloxypropyl) methyldimethoxysilane, gamma-methacryloxypropylmethyldiethoxysilane, gamma-methacryloxypropyltrimethoxysilane, gamma-methacryloxypropyltriethoxysilane, gamma-glycidyloxypropyltriethoxysilane, gamma-3- (3, gamma-aminopropyl) trimethoxysilane, gamma-aminopropyltrimethoxysilane, gamma-glycidyloxypropyltrimethoxysilane, gamma-ethoxytrimethoxysilane, gamma-3- (3-aminopropyl) trimethoxysilane, gamma-glycidyloxypropyltrimethoxysilane, gamma-ethoxysilane, gamma-N-aminopropyltrimethoxysilane, N-ethoxyethoxyethoxysilane, N-aminopropyl-ethoxysilane, N-3-glycidyloxypropyltrimethoxysilane, N-ethoxyethoxyn-ethoxyn.

(4) Titanate-based hydrophobizing agent

Examples of the titanate-based hydrophobizing agent include: KRTTS, KR46B, KR55, KR41B, KR38S, KR138S, KR238S, 338X, KR44, KR9SA (all trade names available from Kudzein Kogyo Co., Ltd.).

Among the above-mentioned hydrophobizing agents, hexamethyldisilazane, polydimethylsiloxane and N, N-dimethylaminotrimethylsilane are preferable. Therefore, the hydrophobizing treatment agent may also contain at least one selected from the group consisting of hexamethyldisilazane, polydimethylsiloxane, and N, N-dimethylaminotrimethylsilane. The more hydrophobic the surface of the non-conductive inorganic particles 102 is, the more negative the interfacial potential of the non-conductive inorganic particles 102 increases. Therefore, the potential difference between the nonconductive inorganic particles 102 and the resin particles 101 coated with the cationic polymer increases. Therefore, the resin particles 101 and the non-conductive inorganic particles 102 are strongly bonded by electrostatic force. For example, the difference between the interface potential of the non-conductive inorganic particles 102 and the interface potential of the resin particles 101 may be 30mV or more or 50mV or more at a pH of 1 or more and 11 or less.

The zeta potential of the hydrophobized nonconductive inorganic particles 102 is preferably negative (negative) in all of water, an organic solvent, and a mixed solution containing water and an organic solvent. Generally, the higher the pH, the more negative the zeta potential. Therefore, it is preferable to select a pH at which the difference between the interfacial potential of the resin particles 101 and the nonconductive inorganic particles 102 increases.

The interfacial potential of the non-conductive inorganic particles 102 can be determined, for example, by: the colloidal vibration potential was measured using a Dada potential probe (trade name "DT 300" manufactured by Dispersion Technologies), or the electrophoretic mobility was measured by laser Doppler velocimetry using a Zetasizer ZS (trade name manufactured by Malvern Instruments).

The following describes an examination of the reason why the resin particles 101 coated with the cationic polymer and the non-conductive inorganic particles 102 coated with the hydrophobizing agent are strongly bonded to each other by electrostatic force rather than chemical bonding force. For example, as shown in chemical formula 1 below, silica particles to which hydroxyl groups have been added are subjected to a hydrophobic treatment with hexamethyldisilazane. In this case, the silica particles are coated with methyl groups as shown in the following chemical formula 2. Since the silica particles are coated with methyl groups, the non-conductive inorganic particles 102 are strongly bonded to the resin particles 101 even though there are no sites where the cationic polymer coated on the surface of the resin particles 101 and the silica particles are chemically bonded to each other. When the particle diameters of the non-conductive inorganic particles are made to be the same, the interfacial potential of the non-conductive inorganic particles 102 coated with the hydrophobizing agent by hexamethyldisilazane exhibits the most negative potential among the non-conductive inorganic particles. At this time, it is found that the potential difference between the non-conductive inorganic particles 102 and the cationic polymer is the largest. For this reason: in order to enhance the adhesion between the resin particles 101 and the non-conductive inorganic particles 102, an electrostatic force generated by a difference in the interface potential, that is, a potential difference between the resin particles 101 and the non-conductive inorganic particles 102 is an important factor for determining the adhesion.

[ solution 1]

[ solution 2]

The hydrophobizing agent may have at least one selected from the group consisting of an amino group, a carboxylic acid group, a hydroxyl group, a sulfonic acid group, a glycidyl group, and a nitrile group, within a range that does not interfere with the hydrophobicity of the nonconductive inorganic particles 102, maintains the interfacial potential of the nonconductive inorganic particles 102 on the negative side, and does not interfere with the electrostatic adhesion of the resin particles 101 to the nonconductive inorganic particles 102. In addition to the hydrophobizing agent, a treating agent having at least one selected from the group consisting of an amino group, a carboxylic acid group, a hydroxyl group, a sulfonic acid group, a glycidyl group, and a nitrile group and not inhibiting the effect of hydrophobizing may be added. The following description will explain the advantages of the hydrophobizing agent including at least one selected from the group consisting of an amino group, a carboxylic acid group, a hydroxyl group, a sulfonic acid group, a glycidyl group, and a nitrile group, and the hydrophobizing agent additionally including at least one selected from the group consisting of an amino group, a carboxylic acid group, a hydroxyl group, a sulfonic acid group, a glycidyl group, and a nitrile group, without hindering the hydrophobizing effect. When the composite particles 103 are subjected to a palladium catalyst treatment described later as a pretreatment step for forming the first layer 104, the adsorption of the palladium catalyst on the surfaces of the non-conductive inorganic particles 102 can be promoted by using the above-described treatment agent. This increases the amount of palladium adsorbed on the surface of the composite particle 103, and thus the first layer 104 can be uniformly formed on the surface of the composite particle 103 where the palladium catalyst is present.

The non-conductive inorganic particles 102 have first non-conductive inorganic particles 102a and second non-conductive inorganic particles 102b having different average particle diameters from each other. The average particle diameter of the first non-conductive inorganic particles 102a and the second non-conductive inorganic particles 102b is, for example, about 1/120 to 1/10 nm, in the present embodiment 25 to 120nm, of the average particle diameter of the resin particles 101. The average particle diameter of the first non-conductive inorganic particles 102a is smaller than the average particle diameter of the second non-conductive inorganic particles 102 b. In the present embodiment, the average particle diameter of the first nonconductive inorganic particles 102a may be, for example, 25nm or more, may be 35nm or more, may be less than 70nm, and may be 65nm or less. The average particle diameter of the second nonconductive inorganic particles 102b may be, for example, 90nm or more, or 95nm or more, or 150nm or less, or 130nm or less, or 125nm or less. The particle diameters of the first nonconductive inorganic particles 102a and the second nonconductive inorganic particles 102b are measured by a specific surface area conversion method using a BET method or an X-ray small angle scattering method. The coefficient of variation of the average particle diameter of each of the first non-conductive inorganic particles 102a and the second non-conductive inorganic particles 102b is less than 20%. When the coefficient of variation is less than 20%, the performance required for each of the first non-conductive inorganic particles 102a and the second non-conductive inorganic particles 102b can be sufficiently exhibited. When the coefficient of variation is less than 20%, the shape variation of the protrusion 109 becomes small, and thus the conductive particles 100a easily achieve both more stable conduction reliability and insulation reliability.

When the average particle diameter of the non-conductive inorganic particles 102 is 25nm to 120nm (or about 1/120 to 1/10 of the average particle diameter of the resin particles 101), the conductive particles 100a can have a plurality of dense protrusions 109, and the non-conductive inorganic particles 102 are less likely to fall off from the resin particles 101. If the average particle size of the non-conductive inorganic particles 102 is 25nm or more (or 1/120 which is equal to or more than the average particle size of the resin particles 101), the protrusions 109 of the first layer 104 tend to have an appropriate size and lower resistance. The following are found: the interface potential of the non-conductive inorganic particles 102 varies depending on the particle diameter, and the interface potential moves further to the negative side as the particle diameter decreases. Therefore, if the average particle diameter of the non-conductive inorganic particles 102 is 120nm or less (or 1/10 which is the average particle diameter of the resin particles 101 or less), the potential difference between the non-conductive inorganic particles 102 and the resin particles 101 becomes sufficient, and the non-conductive inorganic particles 102 are less likely to fall off when the first layer 104 is formed. This makes the number of the protrusions 109 sufficient, and the resistance tends to be low. The metal of the first layer 104 may be coated on the aggregated non-conductive inorganic particles 102 that have come off, and become foreign metal. The metal foreign matter may adhere to the resin particle 101 again to form an excessively long protrusion (for example, a protrusion having a length of more than 500 nm) as an abnormal deposition portion. In this case, the insulation reliability of the conductive particles 100a may be reduced. Further, the metal foreign matter itself may cause a reduction in insulation reliability. Therefore, it is preferable to suppress the non-conductive inorganic particles 102 from falling off from the resin particles 101.

The "diameter of the non-conductive inorganic particles 102" means the diameter of a perfect circle having the same area as the area of the non-conductive inorganic particles 102 on the orthographic projection plane of the non-conductive inorganic particles 102. Specifically, the image obtained by observing the nonconductive inorganic particles at 10 ten thousand times by SEM was analyzed to define the contour of the nonconductive inorganic particles. Then, the area of any non-conductive inorganic particle is calculated, and the diameter of the non-conductive inorganic particle 102 is obtained from the area.

The "average particle diameter of the non-conductive inorganic particles 102" refers to an average particle diameter calculated from the diameter of a perfect circle having the same area as the area of the non-conductive inorganic particles 102 on the orthographic projection surface of the non-conductive inorganic particles 102. Specifically, the image obtained by observing the nonconductive inorganic particles at 10 ten thousand times by SEM was analyzed to define the contour of the nonconductive inorganic particles. Then, the area of each of 500 nonconductive inorganic particles was calculated, the average particle diameter was calculated from the diameter when the area was converted into a circle, and the calculated average particle diameter was set as the average particle diameter of the nonconductive inorganic particles 102.

In the case where only the first non-conductive inorganic particles 102a are used among the non-conductive inorganic particles 102, the protrusions 109 having a diameter of, for example, 200nm or more are not formed or hardly formed on the conductive particles 100 a. In this case, the size of the protrusion 109 is reduced or the height of the protrusion 109 is reduced, so that the effect of improving the conductivity of the conductive particle 100a by the protrusion 109 is insufficient. On the other hand, in the case where only the second nonconductive inorganic particles 102b are used in the nonconductive inorganic particles 102, the average particle diameter of the nonconductive inorganic particles 102 becomes large. In this case, the difference in the interfacial potential between the non-conductive inorganic particles 102 and the resin particles 101 is small, and the non-conductive inorganic particles 102 are easily detached from the resin particles 101. As a result, the first layer 104 is formed in the portion of the resin particle 101 where the non-conductive inorganic particle 102 is not bonded, and the conductive particles 100a are likely to aggregate together through this portion when the first layer 104 is formed, and the insulation reliability is likely to deteriorate. In addition, the detached nonconductive inorganic particles 102 become foreign matter, and insulation reliability is easily deteriorated.

< degree of hydrophobization of non-conductive inorganic particles >

The hydrophobization degree of the non-conductive inorganic particles 102 obtained by the methanol titration method is, for example, 30% or more. In this case, the non-conductive inorganic particles 102 can be strongly adhered to the resin particles 101 by electrostatic force. The degree of hydrophobization may be 50% or more, or 60% or more. As the degree of hydrophobization increases, the interfacial potential of the non-conductive inorganic particles 102 moves further to the negative side, and the non-conductive inorganic particles 102 can be strongly adhered to the resin particles 101 by electrostatic force.

The methanol titration method is a method of measuring the degree of hydrophobization of a powder using methanol. For example, 0.2g of powder whose degree of hydrophobicity is to be measured is first floated on 50ml of water surface. Subsequently, methanol was added little by little to the water while gently stirring the water. Methanol is added dropwise, for example, using a burette. Next, the amount of methanol used at the time when all the powder on the water surface had settled into the water was measured. Then, the percentage of the volume of methanol to the total volume of water and methanol was calculated, and this value was calculated as the degree of hydrophobization of the powder.

< method for bonding non-conductive inorganic particles to resin particles >

The bonding of the nonconductive inorganic particles 102 to the resin particles 101 can be performed using an organic solvent or a mixed solution of water and a water-soluble organic solvent. Examples of the water-soluble organic solvent that can be used include methanol, ethanol, propanol, acetone, dimethylformamide, acetonitrile, and the like. When only the organic solvent is used, the interface potential of the resin particles 101 tends to move further to the positive side, and the interface potential of the non-conductive inorganic particles 102 tends to move further to the negative side. In the case of using only the organic solvent, the potential difference between the resin particles 101 and the non-conductive inorganic particles 102 tends to increase as compared with the case of using a mixed solution of the organic solvent and water. Therefore, when only the organic solvent is used, the non-conductive inorganic particles 102 tend to be strongly adhered to the resin particles 101 by strong electrostatic force. As a result, the non-conductive inorganic particles 102 are less likely to fall off from the resin particles 101, for example, when the first layer 104 is formed.

Regarding the number of the first nonconductive inorganic particles 102a adhering to the resin particle 101, it is preferable that the number of surfaces in a concentric circle having a diameter of 1/2 of the diameter of the resin particle 101 in the orthographic projection plane of the resin particle 101 is in a range of 40 or more and 200 or less. When the number of the first nonconductive inorganic particles 102a is 40 or more, a portion where the nonconductive inorganic particles 102 are not bonded to the resin particles 101 becomes small, and thus a smooth portion is not easily formed on the surface of the conductive particle 100 a. In this case, since the conductive particles 100a are less likely to aggregate together through the smooth portions when the first layer 104 is formed, the monodispersity of the conductive particles 100a tends to be good, and the insulation reliability tends to be improved. In the case where the number of the first nonconductive inorganic particles 102a is 200 or less, the surface of the resin particle 101 is appropriately covered with the nonconductive inorganic particles 102, and the first layer 104 is in good contact with the surface of the resin particle 101 when the first layer 104 is formed. This can suppress a decrease in adhesion between the first layer 104 and the resin particle 101, prevent the first layer 104 from being peeled off from the resin particle 101 when the conductive particle 100a is deformed, and suppress a decrease in conduction reliability. Further, the nonconductive inorganic particles 102 are less likely to be multilayered, aggregated, or associated on the resin particles 101. In this case, the possibility that the nonconductive inorganic particles 102 fall off from the resin particles 101 and become foreign matter can be reduced.

The number of the second nonconductive inorganic particles 102b adhering to the resin particle 101 is preferably in the range of 5 or more and 50 or less on the surface of the concentric circle having a diameter of 1/2 of the diameter of the resin particle 101 in the orthographic projection plane of the resin particle 101. When the number of the second nonconductive inorganic particles 102b is 5 or more, for example, when the conductive particles 100a are interposed between the opposing electrodes and the electrodes are connected by pressure bonding, the increase in the connection resistance value of the electrodes in which the conductive particles 100a are present tends to be suppressed when stored under high temperature and high humidity. In the case where the number of the second non-conductive inorganic particles 102b is 50 or less, the average particle diameter of the non-conductive inorganic particles 102 becomes moderate. In this case, the potential difference between the non-conductive inorganic particles 102 and the resin particles 101 can be made appropriate, and the non-conductive inorganic particles 102 can be prevented from falling off from the resin particles 101. This improves the monodispersity of the conductive particles 100a, and improves the insulation reliability of the conductive particles 100 a. More preferably, the number of the first nonconductive inorganic particles 102a is greater than or equal to 2 times the number of the second nonconductive inorganic particles 102b on the surface within a concentric circle having a diameter 1/2 of the diameter of the resin particle 101 in the orthographic projection plane of the resin particle 101.

< first layer >

The first layer 104 is a conductive layer containing nickel as a main component. The thickness of the first layer 104 is, for example, 40nm to 200 nm. If the thickness of the first layer 104 is within the above range, cracking of the first layer 104 can be suppressed even in the case where the conductive particles 100a are compressed. In addition, the surface of the composite particle 103 can be sufficiently coated with the first layer 104. This can fix the non-conductive inorganic particles 102 to the resin particles 101, thereby suppressing the non-conductive inorganic particles 102 from falling off. As a result, the protrusions 109 having an appropriate size can be formed on the obtained conductive particles 100a at a high density one by one. The first layer 104 may have a thickness of greater than or equal to 60 nm. The thickness of the first layer 104 may be 150nm or less, or 120nm or less. The first layer 104 may have a single-layer structure or a stacked structure. In this embodiment, the first layer 104 has a two-layer structure.

The thickness of the first layer 104 is calculated using a photograph taken with a transmission electron microscope (hereinafter referred to as "TEM"). As a specific example, first, a cross section of the conductive particle 100a is cut out so as to pass through the vicinity of the center of the conductive particle 100a by a thin section method. Next, the cut cross section was observed at a magnification of 25 ten thousand times using a TEM to obtain an image. The thickness of the first layer 104 may then be calculated from the cross-sectional area of the first layer 104 (FIG. 2) estimated from the resulting image. At this time, when it is difficult to distinguish the first layer 104, the resin particles 101, and the non-conductive inorganic particles 102, the composition analysis is performed by an energy dispersion type X-ray detector (hereinafter, referred to as "EDX") attached to the TEM. This clearly distinguishes the first layer 104, the resin particles 101, and the non-conductive inorganic particles 102, and calculates only the thickness of the first layer 104. The thickness of the first layer 104 was set as an average of the thicknesses of 10 conductive particles.

The first layer 104 may contain at least one selected from the group consisting of phosphorus and boron in addition to a metal containing nickel as a main component. This can increase the hardness of the nickel-containing first layer 104, and can easily keep the on-resistance of the conductive particles at a low level when compressed. The first layer 104 may also contain a metal that eutectoid with phosphorus or boron. The first layer 104 contains a metal such as cobalt, copper, zinc, iron, manganese, chromium, vanadium, molybdenum, palladium, tin, tungsten, and rhenium. The first layer 104 can increase the hardness of the first layer 104 by containing nickel and the metal. Thus, even when the conductive particles 100a are compressed, the portions (protrusions 109) formed on the upper portions of the non-conductive inorganic particles 102 can be prevented from being crushed. The metal may also contain tungsten having high hardness. As a constituent material of the first layer 104, for example, a combination of nickel (Ni) and phosphorus (P), a combination of nickel (Ni) and boron (B), a combination of nickel (Ni) and tungsten (W) and boron (B), and a combination of nickel (Ni) and palladium (Pd) are preferable.

When the first layer 104 is formed by electroless nickel plating described later, a phosphorus-containing compound such as sodium hypophosphite can be used as a reducing agent. In this case, phosphorus can be eutectoid, and the first layer 104 containing a nickel-phosphorus alloy can be formed. Boron-containing compounds such as dimethylamine borane, sodium borohydride, potassium borohydride and the like can also be used as the reducing agent. In this case, boron can be eutectoid, and the first layer 104 containing a nickel-boron alloy can be formed. The hardness of the nickel-boron alloy is higher than that of the nickel-phosphorus alloy. Therefore, in the case where the boron-containing compound is used as the reducing agent, even in the case where the conductive particles 100a are compressed, the protrusions 109 formed on the upper portions of the non-conductive inorganic particles 102 can be favorably suppressed from being crushed.

The first layer 104 may have a concentration gradient in which the concentration (content) of nickel increases with distance from the surface of the composite particle 103. With this configuration, even when the conductive particles 100a are compressed, the on-resistance can be kept low. The concentration gradient may be continuous or discontinuous. In the case where the concentration gradient of nickel is discontinuous, a plurality of layers having different nickel contents may be provided as the first layer 104 on the surface of the composite particle 103. In this case, the nickel concentration of the layer provided on the side away from the composite particle 103 increases.

The content of nickel in the first layer 104 increases as approaching the surface in the thickness direction of the first layer 104. The content of nickel in the layer on the surface side of the first layer 104 is, for example, 99 to 97 mass%. The thickness of the layer on the front surface side is, for example, 5 to 60 nm. The thickness of the layer may be 10 to 50nm, or 15 to 40 nm. When the thickness of the layer on the front surface side is 5nm or more, the connection resistance value of the first layer 104 tends to be reduced. On the other hand, when the thickness of the layer on the front surface side is 60nm or less, the monodispersity of the conductive particles 100a tends to be further improved. Therefore, when the content of nickel in the layer on the front surface side of the first layer 104 is 99 to 97 mass%, and the thickness of the layer on the front surface side is 5 to 60nm, the resistance of the first layer 104 can be easily further lowered. Further, it is easy to further suppress aggregation of the conductive particles 100a and obtain high insulation reliability.

A layer having a nickel content of 97 mass% or less may be formed on the composite particle 103 side in the thickness direction of the first layer 104. The nickel content of the layer on the composite particle 103 side may be 95% by mass or less, or 94% by mass or less. The thickness of the layer on the composite particle 103 side may be 20nm or more, 40nm or more, or 50nm or more. In particular, if a layer of 94 mass% or less is formed on the composite particle 103 side of the first layer 104 at 20nm or more, the conductive particles 100a are less susceptible to magnetic influence, and the conductive particles 100a tend to be inhibited from agglomerating with each other.

The kind of the element and the content of the element in the first layer 104 can be measured by, for example, cutting out a cross section of the conductive particle by an ultrathin section method, and then performing composition analysis by EDX with a TEM.

< electroless Nickel plating >

In this embodiment, the first layer 104 is formed by electroless nickel plating. In this case, the electroless nickel plating solution contains a water-soluble nickel compound. The electroless nickel plating solution may further contain at least one compound selected from the group consisting of a stabilizer (e.g., bismuth nitrate), a complexing agent, a reducing agent, a pH adjuster, and a surfactant.

As the water-soluble nickel compound, there can be used: water-soluble nickel inorganic salts such as nickel sulfate, nickel chloride, and nickel hypophosphite; water-soluble nickel organic salts such as nickel acetate and nickel malate. The water-soluble nickel compound may be used singly or in combination of two or more.

The concentration of the water-soluble nickel compound in the electroless nickel plating solution is preferably 0.001 to 1mol/L, and more preferably 0.01 to 0.3 mol/L. When the concentration of the water-soluble nickel compound is within the above range, the deposition rate of the plating film can be sufficiently obtained, and the uniformity of nickel deposition can be improved by suppressing the viscosity of the plating solution from becoming too high.

The complexing agent may be a compound that functions as a complexing agent, and specific examples thereof include: ethylene diamine tetraacetic acid; sodium salts of ethylenediaminetetraacetic acid (e.g., 1-sodium salt, 2-sodium salt, 3-sodium salt, and 4-sodium salt); ethylene diamine triacetic acid; nitrotetraacetic acid, alkali salts thereof; aldonic acid (glyconic acid), tartaric acid, gluconate, citric acid, gluconic acid (glyconic acid), succinic acid, pyrophosphoric acid, glycolic acid, lactic acid, malic acid, malonic acid, alkali salts (e.g., sodium salts) of these acids; triethanolamine glucono (γ) -lactone, and the like. Other materials than those described above may be used as the complexing agent. The complexing agents may be used singly or in combination of two or more.

The concentration of the complexing agent in the electroless nickel plating solution is preferably 0.001 to 2mol/L, and more preferably 0.002 to 1 mol/L. When the concentration of the complexing agent is within the above range, precipitation of nickel hydroxide in the plating solution and decomposition of the plating solution can be suppressed, a sufficient deposition rate of the plating film can be obtained, and the uniformity of nickel deposition can be improved by suppressing the viscosity of the plating solution from becoming too high. The concentration of the complexing agent may also vary depending on the species.

As the reducing agent, a known reducing agent used in an electroless nickel plating solution can be used. As the reducing agent, there may be mentioned: hypophosphorous acid compounds such as sodium hypophosphite and potassium hypophosphite; boron hydrides such as sodium borohydride, potassium borohydride, and dimethylamine borane; hydrazines, and the like.

The concentration of the reducing agent in the electroless nickel plating solution is preferably 0.001 to 1mol/L, and more preferably 0.002 to 0.5 mol/L. If the concentration of the reducing agent is within the above range, the reduction rate of nickel ions in the plating solution can be sufficiently obtained, and decomposition of the plating solution can be suppressed. The concentration of the reducing agent may be different depending on the kind of the reducing agent.

Examples of the pH adjuster include an acidic pH adjuster and a basic pH adjuster. Examples of acidic pH regulators include: hydrochloric acid; sulfuric acid; nitric acid; phosphoric acid; acetic acid; formic acid; copper chloride; iron compounds such as iron sulfate; an alkali metal chloride; ammonium persulfate; aqueous solutions containing more than one of these compounds; and acidic hexavalent chromium-containing aqueous solutions such as chromic acid, chromic acid-sulfuric acid, chromic acid-hydrofluoric acid, dichromic acid-fluoroboric acid, and the like. Examples of the basic pH adjuster include: alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and sodium carbonate; hydroxides of alkaline earth metals; amino group-containing compounds such as ethylenediamine, methylamine, and 2-aminoethanol; solutions containing more than one of these compounds, and the like.

As the surfactant, a cationic surfactant, an anionic surfactant, an amphoteric surfactant, a nonionic surfactant, a mixture of these surfactants, and the like can be used.

< pretreatment for electroless Nickel plating >

When the first layer 104 is formed by electroless nickel plating, the composite particles 103 may be pretreated with a palladium catalyst in advance. The palladium catalyst treatment can be carried out by a known method. The method is not particularly limited, and examples thereof include a catalyst treatment method using a catalyst treatment liquid called an alkaline liquid (seed) or an acidic liquid.

The catalyst treatment method using the alkaline liquid may be, for example, the following method. First, resin particles are immersed in a solution containing palladium ions to which 2-aminopyridine is coordinated, so that the palladium ions are adsorbed on the surfaces of the resin particles. After washing with water, the resin particles having palladium ions adsorbed thereon are dispersed in a solution containing a reducing agent such as sodium hypophosphite, sodium borohydride, dimethylamine borane, hydrazine, formalin, or the like, and subjected to reduction treatment. This reduces the palladium ions adsorbed on the surface of the resin particles to metallic palladium.

The catalyst treatment method using the acidic liquid solution includes, for example, the following methods. First, resin particles are dispersed in a stannous chloride solution, and after a sensitizing treatment in which tin ions are adsorbed to the surfaces of the resin particles, water washing is performed. Next, the resin particles are dispersed in a solution containing palladium chloride, and activation treatment is performed to capture palladium ions on the surfaces of the resin particles. After washing with water, the resulting mixture is dispersed in a solution containing a reducing agent such as sodium hypophosphite, sodium borohydride, dimethylamine borane, hydrazine, or formalin, and then subjected to reduction treatment. This reduces the palladium ions adsorbed on the surface of the resin particles to metallic palladium.

When the basic liquid is compared with the acidic liquid, the acidic liquid is preferable from the viewpoint of the pH of the solution. As described above, the lower the pH, the more the interfacial potential of the resin particle 101 itself shifts to a positive value, and therefore, it is preferable to use an acidic liquid. On the other hand, the higher the pH, the more negative the interfacial potential of the non-conductive inorganic particles 102 is, and therefore, it is preferable to use an alkaline liquid. Here, if the difference in the interfacial potential between the resin particles 101 and the non-conductive inorganic particles 102 is considered, the difference in interfacial potential tends to increase as the pH is lower. By using the acidic liquid, the state in which the nonconductive inorganic particles 102 are strongly adhered to the resin particles 101 by the electrostatic force tends to be maintained.

In the case of using the basic liquid, it is preferable that the hydrophobizing treatment agent has at least one selected from the group consisting of an amino group, a carboxylic acid group, a hydroxyl group, a sulfonic acid group, a glycidyl group, and a nitrile group. For example H of carboxylic acid groups and hydroxyl groups⁺When the pH is 7 or more, the dissociation proceeds, and the interfacial potential of the non-conductive inorganic particles 102 further shifts to the negative side. However, since the interface potential of the resin particles 101 also varies depending on pH, it is preferable to select the type of the seed solution so that the difference between the interface potentials of the resin particles 101 and the nonconductive inorganic particles 102 can be kept large.

In these methods of treating with a palladium catalyst, palladium ions are adsorbed on the surface and then washed with water, and further dispersed in a solution containing a reducing agent. This reduces palladium ions adsorbed on the surface of the composite particle 103, thereby forming palladium precipitation nuclei having an atomic level size.

< protrusions >

The area of the protrusion 109 of the conductive particle 100a refers to the area of the protrusion 109 in a concentric circle having a diameter 1/2 of the diameter of the conductive particle 100a or the area of the outline of each protrusion 109 separated by a recess between adjacent protrusions 109 on the orthographic projection plane of the conductive particle 100 a. The diameter (outer diameter) of the protrusion 109 is a diameter of a perfect circle having the same area as the area of the protrusion 109, which is calculated for the protrusion 109 existing in a concentric circle having a diameter 1/2 of the diameter of the conductive particle 100a on the orthographic projection surface of the conductive particle 100 a. Specifically, the area of each protrusion is determined by analyzing an image obtained by observing the conductive particle 100a at a magnification of 3 ten thousand by SEM and defining the outline of the protrusion 109. Then, the diameter is calculated from the area.

The ratio of the area of the protrusion 109 (coverage) can be expressed as a percentage calculated by taking the total area of the concentric circles having a diameter of 1/2 and the diameter of the conductive particle 100a on the orthographic projection surface of the conductive particle 100a as a denominator and the total area of the protrusion 109 in the concentric circle having a diameter of 1/2 and the diameter of the conductive particle 100a as a numerator. The ratio of the area (coverage) of the protrusion 109 may be 50% or more, 65% or more, or 80% or more. If the coverage of the protrusions 109 is within the above range, the on-resistance of the conductive particles 100a is not easily increased even when the particles are left under high humidity.

The optimum diameter (outer diameter) of the protrusion 109 and the optimum ratio of the coverage of the protrusion 109 are different depending on the diameters of the resin particle 101 and the nonconductive inorganic particle 102. In any of the non-conductive inorganic particles 102 (the first non-conductive inorganic particle 102a and the second non-conductive inorganic particle 102b), the coating rate of the protrusion 109 can be set to 50% or more by setting the coating rate of the non-conductive inorganic particle 102 to the resin particle 101 to 20 to 80%.

The protrusions 109 of the conductive particles 100a are classified into, for example, first protrusions having a diameter of 50nm or more and less than 100nm, second protrusions having a diameter of 100nm or more and less than 200nm, and third protrusions having a diameter of 200nm or more and less than 350 nm. In this case, the conductive particles 100a have the first protrusions and the second protrusions each of which is 20 or more (40 or more in total) on the surface within the concentric circle having the 1/2 diameter of the conductive particles 100a in the orthographic projection plane of the conductive particles 100 a. The conductive particles 100a may have 40 or more (80 or more in total) first protrusions and second protrusions, respectively. The conductive particle 100a has, on a surface within a concentric circle having an 1/2 diameter of the conductive particle 100a in an orthographic projection plane of the conductive particle 100a, a third protrusion of greater than or equal to 5 and less than or equal to 20. Preferably, all or almost all of the portions other than the portions where the third protrusions having a diameter of 200nm or more and 350nm or less are formed in the range of 5 to 20 in number on the surface of the conductive particle 100a are formed by the first protrusions or the second protrusions having a diameter of 200nm or less.

The total number of the first protrusions and the second protrusions having a diameter of less than 200nm included in the conductive particles 100a is 40 or more, and thus the portion of the resin particle 101 to which the non-conductive inorganic particle 102 is not bonded is reduced to a suitable degree. Thus, if the first layer 104 is formed, a smooth surface is not easily formed on the conductive particle 100 a. In this case, the conductive particles 100a are less likely to aggregate through the above portions when the first layer 104 is formed. Therefore, when the total number of the first protrusions and the second protrusions is 40 or more, the decrease in monodispersity of the conductive particles 100a is suppressed, and the decrease in insulation reliability tends to be prevented. When the number of the third protrusions having a diameter of 200nm or more and 350nm or less is 5 or more, for example, when the conductive particles 100a are interposed between the opposing electrodes and the electrodes are pressure-bonded to each other, the connection resistance value of the electrodes of the conductive particles 100a tends to be less likely to increase if the electrodes are stored under high temperature and high humidity.

In order to form more than 20 third protrusions having a diameter of 200nm or more and 350nm or less on the conductive particles 100a, it is necessary to bond more than 50 non-conductive inorganic particles 102 having a diameter of 90nm or more and 150nm or less to the resin particles 101. In this case, as described above, the non-conductive inorganic particles 102 are easily detached from the resin particles 101, and therefore the conductive particles 100a are easily aggregated with each other when the first layer 104 is formed.

Here, in the case where the first non-conductive inorganic particles 102a or the second non-conductive inorganic particles 102b are used alone as the non-conductive inorganic particles 102, the following problems are likely to occur in the conductive particles 100 a.

When the first nonconductive inorganic particles 102a having an average particle diameter in the range of 25 to 70nm and a coefficient of variation of less than 20% are used alone, the ratio of the first protrusions and the second protrusions to the entire protrusions 109 is 95% or more, the third protrusions are not formed, or the number of the third protrusions is less than 5. In this case, since the number of the protrusions 109 having a small height is large, it is difficult to ensure the conduction reliability. For example, even if the average particle diameter of the first nonconductive inorganic particles 102a is 70nm and 5 or more third protrusions having a diameter of 200nm or more and 350nm or less can be formed, the first layer 104 to be the protrusions formed on the upper portions of the first nonconductive inorganic particles 102a is deformed when the conductive particles 100a are compressed. In this case, although a connection structure or the like using an anisotropic conductive adhesive containing conductive particles 100a exhibits a low connection resistance value in an initial state, the connection resistance value tends to increase if the connection structure or the like is stored at high temperature and high humidity. For this reason, the second nonconductive inorganic particles 102b having an average particle diameter of 90nm or more and 150nm or less in the conductive particles 100a serve as cores, and 5 or more and 20 or less protrusions having a diameter of 200nm or more are formed. This can suppress collapse of the protrusion 109 even when compressed, and can suppress an increase in the connection resistance value even when the connection structure or the like is stored under high temperature and high humidity conditions.

When the second nonconductive inorganic particles 102b having an average particle diameter in the range of 90nm or more and 150nm or less and a coefficient of variation of less than 20% are used alone, the average particle diameter of the entire nonconductive inorganic particles 102 becomes large, and as described above, the nonconductive inorganic particles 102 are easily detached from the resin particles 101. This causes a problem that the monodispersity of the conductive particles 100a is reduced and the insulation reliability of the conductive particles 100a is reduced because the conductive particles 100a are easily aggregated in a portion where the smooth first layer 104 is formed when the first layer 104 is formed. Further, even if the third protrusions are formed in an amount of 5 or more and less than 20, the diameter of the protrusions 109 on the surface of the conductive particle 100a is likely to vary. In this case, if the number of particles captured between the electrodes of the connection structure or the like using the anisotropic conductive adhesive containing the conductive particles 100a is reduced, the number of protrusions 109 in contact with the electrodes varies among the conductive particles 100 a. Therefore, the connection resistance value tends to increase similarly to the case of using only the first nonconductive inorganic particles 102 a.

On the other hand, if the first non-conductive inorganic particles 102a and the second non-conductive inorganic particles 102b are used in combination, the smooth portions are almost eliminated on the composite particles 103 when the first layer 104 is formed, and therefore, the aggregation of the conductive particles 100a with each other can be suppressed. Therefore, the monodispersity of the conductive particles 100a is improved, and good insulation reliability can be obtained. In particular, the first nonconductive inorganic particles 102a are bonded to the resin particle 101 in a range of 40 or more and 200 or less on the surface of the concentric circle having a diameter of 1/2 of the diameter of the resin particle 101 in the orthographic projection plane of the resin particle 101. Accordingly, the first protrusions can be stably formed in a range of 20 or more and the second protrusions can be stably formed in a range of 20 or more with the first nonconductive inorganic particles 102a as cores. The second nonconductive inorganic particles 102b are bonded to the resin particle 101 in a range of 5 or more and 50 or less within a concentric circle having a diameter 1/2 of the diameter of the resin particle 101 in an orthographic projection plane of the resin particle 101. Thus, the third protrusions formed with the second nonconductive inorganic particles 102b as cores can be stably formed in a range of 5 or more and 20 or less. In this case, the above-described problem can be solved, and when the conductive particles 100a are interposed between opposing electrodes and the electrodes are pressure-bonded to each other, for example, sufficiently low on-resistance can be obtained, and excellent on-reliability and insulation reliability can be highly achieved at the same time.

< monodispersion ratio of conductive particles >

The monodispersion ratio of the conductive particles 100a may be 96.0% or more, or 98.0% or more. When the monodispersion ratio of the conductive particles 100a is within the above range, for example, high insulation reliability can be obtained after a moisture absorption test. The monodispersity of the conductive particles 100a can be measured by coulter multizer II (product name, manufactured by beckmann coulter corporation) using, for example, 50,000 conductive particles.

< method for producing conductive particles >

Next, a method for producing the conductive particles 100a according to embodiment 1 will be described. First, as a first step, the resin particles 101 are coated with a cationic polymer (first coating step). In the first step, resin particles 101 having hydroxyl groups or the like on the surface are dispersed in a cationic polymer solution, and the resin particles 101 are coated with a cationic polymer.

Next, as a second step, the surfaces of the first non-conductive inorganic particles 102a and the second non-conductive inorganic particles 102b (hereinafter, simply referred to as non-conductive inorganic particles 102) are coated with a hydrophobic treatment agent (second coating step). The coating of the non-conductive inorganic particles 102 with the hydrophobizing agent is performed in water, an organic solvent, or a mixed solution of water and a water-soluble organic solvent, or in a gas phase. Examples of the water-soluble organic solvent that can be used include methanol, ethanol, propanol, acetone, dimethylformamide, and acetonitrile. Non-conductive inorganic particles coated with a hydrophobizing agent in advance may be purchased and used as the non-conductive inorganic particles 102.

Next, as a third step, the non-conductive inorganic particles 102 are arranged and bonded to the surface of the resin particle 101 to form the composite particle 103. The adhesion of the nonconductive inorganic particles 102 to the resin particles 101 is performed, for example, by an organic solvent or a mixed solution of water and a water-soluble organic solvent. The nonconductive inorganic particles 102 are preferably bonded to the resin particles 101 using only an organic solvent. When the difference in the interface potential between the resin particles 101 and the non-conductive inorganic particles 102 is considered, the difference in the interface potential between the non-conductive inorganic particles 102 and the resin particles 101 increases in the case where only the organic solvent is used, as compared with the case where the organic solvent containing water is used. If a stronger electrostatic force acts between the non-conductive inorganic particles 102 and the resin particles 101, the non-conductive inorganic particles 102 can be strongly adhered to the resin particles 101. As a result, the non-conductive inorganic particles 102 are less likely to fall off in the pretreatment step for performing electroless nickel plating and the electroless nickel plating step.

In the third step, on the surface of the concentric circle having a diameter of 1/2 of the diameter of the resin particle 101 in the orthographic projection plane of the resin particle 101, the first nonconductive inorganic particles 102a are bonded to the resin particle 101 in the range of 40 or more and 200 or less, and the second nonconductive inorganic particles 102b are bonded to the resin particle 101 in the range of 5 or more and 50 or less. At this time, on the surface, the number of the first non-conductive inorganic particles 102a may be greater than or equal to 2 times the number of the second non-conductive inorganic particles 102 b.

Next, as a fourth step, the composite particles 103 are coated with a metal layer by electroless plating, thereby forming conductive particles 100 a. In the fourth step, the first layer 104 containing nickel is used as a metal layer, and the entire surface of the composite particle 103 (that is, the entire surface where the resin particle 101 and the nonconductive inorganic particle 102 are exposed) is covered with the first layer 104. At this time, the conductive particle 100a has, on the surface within a concentric circle having a diameter 1/2 of the diameter of the resin particle 101 in the orthographic projection plane of the resin particle 101, a first protrusion and a second protrusion each of which is 20 or more, and has a third protrusion of which is 5 or more and 20 or less.

In the fourth step, the composite particles 103 may be subjected to a palladium catalyst treatment as a pretreatment step for forming the first layer 104 by electroless nickel plating. The palladium catalyst treatment can be carried out by a known method, for example, by the above-described catalyst treatment method using a catalyst treatment liquid called an alkaline liquid or an acidic liquid. Even if the non-conductive inorganic particles 102 are arranged on the surface of the resin particle 101 in advance, the interface potential between the resin particle 101 and the non-conductive inorganic particles 102 changes under the influence of the surrounding pH.

When an acidic liquid is used, the pH of the catalyst treatment liquid is about 1. In this case, the absolute value of the difference between the measured value of the interfacial potential of the resin particles 101 and the measured value of the interfacial potential of the non-conductive inorganic particles 102 is 50mV or more. Therefore, the non-conductive inorganic particles 102 coated with the hydrophobic property-imparting agent are less likely to fall off. On the other hand, when a commonly used alkaline liquid is used, the pH of the catalyst treatment liquid is 10 to 11. In this case, the absolute value of the difference between the measured value of the interfacial potential of the resin particles 101 and the measured value of the interfacial potential of the non-conductive inorganic particles 102 is about 30 to 50 mV. Therefore, in the pretreatment step, the nonconductive inorganic particles 102 are easily detached from the resin particles 101.

The operation and effects of the conductive particles 100a according to embodiment 1 described above will be described in comparison with patent documents 1 to 3. When the conductive particles are formed by the methods described in patent documents 1 and 2, it is difficult to control the number, size, and shape of the protrusions of the conductive particles, and the resistance value of an adhesive or the like using the conductive particles tends to be high. Therefore, when the conductive particles described in patent documents 1 and 2 are intended to have improved conductivity, projections (abnormal projections) having an abnormal size and a length of more than 500nm tend to be formed on the surface of the conductive particles. An adhesive using such conductive particles having abnormal protrusions (abnormal precipitation portions) tends to have a reduced insulation reliability. In particular, when the conductive particles are formed according to the method described in patent document 2, a sufficient amount of the core material must be attached to the surface of the fine particles serving as the base material in order to reduce the resistance value of the conductive particles. However, if the amount of the core material attached is increased, the core material itself tends to agglomerate on the surface of the fine particles, and abnormal protrusions tend to be formed.

In the method described in patent document 3, a non-conductive substance serving as a core substance is chemically bonded to the surface of a resin particle to form a composite particle. If a pretreatment step for electroless nickel plating or an electroless nickel plating step is performed to coat the composite particles with a metal layer, the nonconductive material will fall off from the resin particles. Therefore, it is difficult to control the number, size, and shape of the protrusions of the composite particles, and the resistance value of an adhesive or the like using these conductive particles tends to be high. Further, in the electroless nickel plating step, if the non-conductive substance from which nickel has been precipitated falls off, it becomes a source of generation of foreign metal. When the metal foreign matter is reattached to the composite particle, an abnormal protrusion (abnormal precipitation portion) may be formed. Further, the metal foreign matter itself is contained in the adhesive, and may cause a reduction in insulation reliability.

In contrast to patent documents 1 to 3, the conductive particle 100a formed by the manufacturing method according to embodiment 1 includes a composite particle 103 and a first layer 104 covering the composite particle 103, the composite particle 103 includes a resin particle 101 and a non-conductive inorganic particle 102 disposed on a surface of the resin particle 101, and the first layer 104 includes a protrusion 109 having the non-conductive inorganic particle 102 as a core on an outer surface thereof. In addition, on the surface within a concentric circle having a diameter of 1/2 of the diameter of the resin particle 101 in the orthographic projection plane of the resin particle 101, the nonconductive inorganic particles 102 have 40 or more and 200 or less first nonconductive inorganic particles 102a having a diameter of less than 70nm, and have 5 or more and 50 or less second nonconductive inorganic particles 102b having a diameter of 90nm or more and 150nm or less. In other words, the protrusions 109 have 20 or more first protrusions having a diameter of 50nm or more and less than 100nm, 20 or more second protrusions having a diameter of 100nm or more and less than 200nm, and 5 or more and less than 20 third protrusions having a diameter of 200nm or more and less than 350nm on the surface within a concentric circle of 1/2 diameters having the diameter of the conductive particle 100 a.

According to the conductive particle 100a, the size and number of the protrusion 109 formed by using the non-conductive inorganic particle 102 as a core can be controlled within an appropriate range. Therefore, the protrusions 109 of the conductive particles 100a have a size (height) to be stably in contact with an electrode surface or the like to be connected. In addition, the number of extremely large (tall) protrusions 109 in the conductive particles 100a can be reduced, and the distance between the conductive particles 100a can be kept constant. Further, the nonconductive inorganic particles 102 serving as the cores of the protrusions 109 suppress aggregation of the resin particles 101, and the conductive particles 100a have good dispersibility. Therefore, by blending the conductive particles 100a in the anisotropic conductive adhesive, excellent conduction reliability and insulation reliability can be highly achieved at the same time.

The number of the first non-conductive inorganic particles 102a may be greater than or equal to 2 times the number of the second non-conductive inorganic particles 102b on the surface within the concentric circle having the 1/2 diameter of the resin particle 101 in the orthographic projection plane of the resin particle 101. In this case, the presence of the second nonconductive inorganic particles 102b larger than the first nonconductive inorganic particles 102a easily suppresses the aggregation of the resin particles 101. Thus, conductive particles 100a having excellent monodispersity are easily obtained, and conductive particles 100a having more stable insulation reliability tend to be obtained. Further, the larger protrusion 109 formed of the second nonconductive inorganic particle 102b tends to easily ensure more stable connection reliability.

The first non-conductive inorganic particles 102a may have an average particle size in a range of 25 to 70nm and a coefficient of variation of less than 20%, and the second non-conductive inorganic particles 102b may have an average particle size in a range of 90 to 130nm and a coefficient of variation of less than 20%. In this case, the performance required for each of the first non-conductive inorganic particles 102a and the second non-conductive inorganic particles 102b can be sufficiently exhibited. In addition, since the non-conductive inorganic particles 102 have small variations in average particle size, the shape (height, area, and the like) of the protrusions 109 on the surface of the conductive particles 100a is easily uniform. Thus, for example, when the conductive particles 100a between the counter electrodes are deformed, the protrusions 109 are likely to be uniformly in contact with the electrodes, and more stable conduction reliability tends to be obtained. Further, since the height variation of the protrusions 109 is reduced, the distance variation between the conductive particles 100a existing between the adjacent electrodes is reduced, and more stable insulation reliability tends to be obtained. The coefficient of variation is also referred to as CV in the present specification. The coefficient of variation is a ratio of a standard deviation of the particle diameter to an average particle diameter expressed as a percentage.

The surfaces of the non-conductive inorganic particles 102 may be coated with a hydrophobic treatment agent, and the resin particles 101 may be coated with a cationic polymer. In this case, the interfacial potential of the surface of the non-conductive inorganic particle 102 moves to a negative number by hydrophobization, and the interfacial potential of the surface of the resin particle 101 moves to a positive number. Thus, electrostatic force acts between the resin particles 101 and the nonconductive inorganic particles 102, and the nonconductive inorganic particles 102 are less likely to fall off from the resin particles 101. Therefore, the generation of abnormal precipitation portions can be suppressed, and the generation of metallic foreign matter can be reduced in the production of the conductive particles 100 a.

The hydrophobizing agent is selected from the group consisting of a silicon nitride-based hydrophobizing agent, a silicone-based hydrophobizing agent, a silane-based hydrophobizing agent, and a titanate-based hydrophobizing agent.

The hydrophobization degree of the non-conductive inorganic particles 102 obtained by the methanol titration method is, for example, 30% or more. In this case, a sufficient electrostatic force acts between the nonconductive inorganic particles 102 and the resin particles 101.

The difference in the interfacial potential between the resin particles 101 and the non-conductive inorganic particles 102 is, for example, 30mV or more at a pH of 1 or more and 11 or less. In this case, the resin particles 101 and the non-conductive inorganic particles 102 are strongly bonded by electrostatic force. Therefore, the non-conductive inorganic particles 102 can be suitably prevented from falling off from the resin particles 101 in a pretreatment step for forming the first layer 104 in the conductive particles 100a, a step of forming the first layer 104, and the like.

The cationic polymer is selected from the group consisting of polyamine, polyimine, polyamide, polydiallyldimethylammonium chloride, polyvinylamine, polyvinylpyridine, polyvinylimidazole, and polyvinylpyrrolidone.

The cationic polymer may also be polyethyleneimine. In this case, since the charge density of the cationic polymer is increased, the non-conductive inorganic particles 102 can be favorably prevented from falling off.

The average particle diameter of the resin particles is, for example, 1 μm or more and 10 μm or less. For example, when a connection structure is produced using an anisotropic conductive adhesive containing conductive particles 100a, the conductivity and the like of the anisotropic conductive adhesive are less likely to change due to variations in the shape (height) of the electrodes of the connection structure.

The non-conductive inorganic particles 102 are selected from the group consisting of silica, zirconia, alumina, and diamond.

The metal layer has a first layer 104 comprising nickel. The first layer 104 is a layer that covers the composite particles 103 by electroless plating. In this case, the hardness of the conductive particles 100a can be increased. Thus, even when the conductive particles 100a are compressed, the first layer 104 formed as a protruding portion on the non-conductive inorganic particles 102 is not easily crushed. Therefore, the conductive particles 100a can obtain low on-resistance.

The first layer 104 of metal layers may also have multiple conductive layers. At least one of the thickness, composition, and shape of the conductive layers may be different from each other. For example, the content of the metal that becomes the main component in the first layer 104 may increase as approaching the surface in the thickness direction of the first layer 104. In order to form the first layer 104 having a plurality of conductive layers, a plurality of plating solutions may be used. For example, by using plating solutions having different concentrations of deposited metals, the first layer 104 having a plurality of conductive layers can be easily formed.

The first layer 104 may be formed, for example, by: after the first plating solution is fed or before the feeding of the first plating solution is completed, a second plating solution having a concentration of a metal to be precipitated different from (higher than) that of the first plating solution is fed. In this case, the first layer 104 in which the metal concentration in the thickness direction gradually changes (rises) toward the surface can be formed. Further, since a step of forming a plurality of conductive layers having different compositions is not required, the first layer 104 can be formed in a short time.

(embodiment 2)

The conductive particles according to embodiment 2 will be described below. In the description of embodiment 2, redundant description with embodiment 1 is omitted, and portions different from embodiment 1 are described. That is, the description of embodiment 1 can be used as appropriate in embodiment 2 within the technical range.

Fig. 3 is a schematic cross-sectional view showing conductive particles according to embodiment 2. The conductive particle 100b shown in fig. 3 has the same configuration as the conductive particle 100a shown in fig. 1, except that it has the second layer 105 provided on the first layer 104. The second layer 105 may be a metal layer or an alloy layer.

< second layer >

The second layer 105 is a conductive layer provided so as to cover the first layer 104. The thickness of the second layer 105 is, for example, 5nm to 100 nm. The thickness of the second layer 105 may be 5nm or more, or 10nm or more. The thickness of the second layer 105 may also be less than or equal to 30 nm. When the thickness of the second layer 105 is within the above range, the thickness of the second layer 105 can be made uniform when the second layer 105 is formed, and thus, the element (e.g., nickel) contained in the first layer 104 can be favorably prevented from diffusing to the surface on the side opposite to the second layer 105.

The thickness of the second layer 105 was calculated using a photograph taken by TEM. As a specific example, first, a cross section of the conductive particle 100b is cut out so as to pass through the vicinity of the center of the conductive particle 100b by a thin section method. Next, the cut cross section was observed at a magnification of 25 ten thousand times using a TEM to obtain an image. The thickness of the second layer 105 may then be calculated from the cross-sectional area of the second layer 105 (FIG. 4) estimated from the resulting image. At this time, when it is difficult to distinguish the second layer 105, the first layer 104, the resin particles 101, and the non-conductive inorganic particles 102, the composition analysis is performed by EDX attached to TEM. This clearly distinguishes the second layer 105, the first layer 104, the resin particles 101, and the nonconductive inorganic particles 102, and calculates only the thickness of the second layer 105. The thickness of the second layer 105 was set as an average of the thicknesses of the 10 conductive particles.

The second layer 105 contains at least one selected from the group consisting of a noble metal and cobalt. The noble metal is palladium, rhodium, iridium, ruthenium, platinum, silver and gold. When the second layer 105 contains gold, the on-resistance of the surface of the conductive particle 100b can be reduced, and the conductive characteristics of the conductive particle 100b can be improved. In this case, the second layer 105 functions as an antioxidation layer of the first layer 104 containing nickel. Thus, the second layer 105 is formed on the first layer 104. The thickness of the second layer 105 in the case of containing gold may also be 30nm or less. In this case, the effect of reducing the on-resistance of the surface of the conductive particle 100b is excellent in balance with the manufacturing cost. However, the thickness of the second layer 105 in the case of gold may also exceed 30 nm.

The second layer 105 is preferably composed of at least one selected from the group consisting of palladium, rhodium, iridium, ruthenium, and platinum. In this case, the surface oxidation of the conductive particles 100b can be suppressed, and the insulation reliability of the conductive particles 100b can be improved. The second layer 105 is more preferably composed of at least one selected from the group consisting of palladium, rhodium, iridium, and ruthenium. In this case, even in the case of compressing the conductive particles 100b, the first layer 104 to be the protrusion 109 formed on the non-conductive inorganic particles 102 is suppressed from being crushed, and the resistance of the compressed conductive particles 100b is suppressed from increasing. The second layer 105 is formed on the composite particle 103 covered with the first layer 104 by electroless plating after the first layer 104 is formed by, for example, the fourth step of embodiment 1.

< Palladium >

In the case where the second layer 105 contains palladium, the second layer 105 can be formed by electroless palladium plating, for example. The electroless palladium plating can be performed by using either a substitution type using no reducing agent or a reduction type using a reducing agent. Examples of the substitution type of such an electroless palladium plating solution include MCA (product name, manufactured by World Metal Co., Ltd.). Examples of the reducing form include APP (product name, manufactured by Shigaku K.K.). When the substitution type is compared with the reduction type, the reduction type is preferable from the viewpoint of less generation of voids and easy securing of the coating area.

In the case where the second layer 105 contains palladium, the lower limit of the content of palladium in the second layer 105 may be 90% by mass or more, 93% by mass or more, or 94% by mass or more, based on the total amount of the second layer 105. The upper limit of the content of palladium in the second layer 105 may be 99% by mass or less, or 98% by mass or less, based on the total amount of the second layer 105. In the case where the content of palladium in the second layer 105 is within the above range, the hardness of the second layer 105 is increased. Therefore, even in the case of compressing the conductive particles 100b, the protrusion 109 can be suppressed from being crushed.

In order to adjust the palladium content in the second layer 105 (for example, to 93 to 99 mass%), there is no particular limitation on the reducing agent used in the electroless palladium plating solution, and it is possible to use: phosphorus-containing compounds such as hypophosphorous acid, phosphorous acid, and alkali salts of these acids; boron-containing compounds, and the like. In this case, the resulting second layer 105 contains a palladium-phosphorus alloy or a palladium-boron alloy. Therefore, it is preferable to adjust the concentration of the reducing agent, pH, temperature of the plating solution, and the like so that the palladium content in the second layer 105 falls within a desired range.

< rhodium >

In the case where the second layer 105 contains rhodium, the second layer 105 can be formed by electroless plating of rhodium, for example. Examples of the rhodium supply source used in the electroless rhodium plating solution include rhodium ammine hydroxide, rhodium ammine nitrate, rhodium ammine acetate, rhodium ammine sulfate, rhodium ammine sulfite, rhodium ammine bromide, and rhodium ammine compound.

Examples of the reducing agent used in the electroless rhodium plating solution include hydrazine, sodium hypophosphite, dimethylamine borate, diethylamine borate, and sodium borohydride. As the reducing agent, hydrazine is preferable. A stabilizer or a complexing agent (ammonium hydroxide, hydroxylamine salt, hydrazine dichloride, or the like) may be added to the electroless rhodium plating solution.

The temperature (bath temperature) of the electroless rhodium plating solution may be 40 ℃ or higher, or 50 ℃ or higher, from the viewpoint of obtaining a sufficient plating rate. The temperature of the plating solution may be 90 ℃ or lower, or 80 ℃ or lower, from the viewpoint of stably holding the electroless rhodium plating solution.

< Iridium >

In the case where the second layer 105 contains iridium, the second layer 105 can be formed by electroless plating of iridium, for example. Examples of the supply source of iridium used in the electroless iridium plating solution include iridium trichloride, iridium tetrachloride, iridium tribromide, iridium tetrabromide, iridium tripotassium hexachloride, iridium dipotassium hexachloride, iridium trisodium hexachloride, iridium disodium hexachloride, iridium tripotassium hexabromide, iridium dipotassium hexabromide, iridium tripotassium hexaiodide, iridium diselenide and iridium diselenide.

Examples of the reducing agent used in the electroless iridium plating solution include hydrazine, sodium hypophosphite, dimethylamine borate, diethylamine borate, and sodium borohydride. As the reducing agent, hydrazine is preferable. A stabilizer or a complexing agent may be added to the electroless iridium plating solution.

As the stabilizer or complexing agent, at least one selected from the group consisting of monocarboxylic acid, dicarboxylic acid, and salts of these acids may be added. Specific examples of the monocarboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, and lactic acid. Specific examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, and malic acid. Examples of the salt include compounds in which sodium, potassium, lithium, and the like are bonded to the carboxylic acid as counter ions. The stabilizer or the complexing agent may be used singly or in combination of two or more.

The pH of the electroless iridium plating solution may be 1 or more, or 2 or more, from the viewpoint of suppressing corrosion of the plating object and obtaining a sufficient plating rate. The pH of the electroless iridium plating solution may be 6 or less, or may be 5 or less, from the viewpoint of easily suppressing inhibition of the plating reaction.

The temperature (bath temperature) of the electroless iridium plating solution may be 40 ℃ or higher or 50 ℃ or higher from the viewpoint of obtaining a sufficient plating rate. The temperature (bath temperature) of the electroless iridium plating solution may be 90 ℃ or lower, or 80 ℃ or lower, from the viewpoint of stably maintaining the electroless iridium plating solution.

< ruthenium >

In the case where the second layer 105 contains ruthenium, the second layer 105 can be formed by electroless ruthenium plating, for example. As the electroless ruthenium plating solution, for example, commercially available plating solutions can be used, and electroless ruthenium Ru (trade name, product of osye pharmaceutical industries, ltd.) can be used.

< platinum >

In the case where the second layer 105 contains platinum, the second layer 105 can be formed by, for example, electroless platinum plating. As a supply source of platinum used in the electroless platinum plating solution, for example, Pt (NH) can be mentioned₃)₄(NO₃)₂、Pt(NH₃)₄(OH)₂、PtCl₂(NH₃)₂、Pt(NH₃)₂(OH)₂、(NH₄)₂PtCl₆、(NH₄)₂PtCl₄、Pt(NH₃)₂Cl₄、H₂PtCl₆And PtCl₂。

Examples of the reducing agent used in the electroless platinum plating solution include hydrazine, sodium hypophosphite, dimethylamine borate, diethylamine borate, and sodium borohydride. As the reducing agent, hydrazine is preferable. A stabilizer or a complexing agent (hydroxylamine chloride, hydrazine dichloride, ammonium hydroxide, EDTA, etc.) may be added to the electroless platinum plating solution.

The temperature (bath temperature) of the electroless platinum plating solution may be 40 ℃ or higher, or 50 ℃ or higher, from the viewpoint of obtaining a sufficient plating rate. The temperature (bath temperature) of the electroless platinum plating solution may be 90 ℃ or lower, or 80 ℃ or lower, from the viewpoint of stably maintaining the electroless platinum plating solution.

When the electroless platinum plating solution is used for plating platinum, the pH of the electroless platinum plating solution is only required to be 8-12. If the pH is 8 or more, platinum is likely to be sufficiently precipitated. If the pH is 12 or less, a good working environment can be easily ensured.

< silver >

In the case where the second layer 105 contains silver, the second layer 105 can be formed by electroless silver plating, for example. The source of silver used in the electroless silver plating solution is not particularly limited as long as it is soluble in the plating solution. For example, it is possible to use: silver nitrate, silver oxide, silver sulfate, silver chloride, silver sulfite, silver carbonate, silver acetate, silver lactate, silver sulfosuccinate, silver sulfonate, silver sulfamate, and silver oxalate. The water-soluble silver compound may be used singly or in combination of two or more.

The reducing agent used in the electroless silver plating solution is not particularly limited as long as it has an ability to reduce a water-soluble silver compound in the electroless silver plating solution to metallic silver and is a water-soluble compound. For example, it is possible to use: hydrazine derivatives, formaldehyde compounds, hydroxylamines, sugars, Rochelle salts (Rochelle salt), boron hydrides, hypophosphites, DMAB and ascorbic acid. The reducing agent may be used singly or in combination of two or more.

A stabilizer or a complexing agent may also be added to the electroless silver plating solution. As stabilizers or complexing agents, for example, it is possible to use: sulfites, succinimides, hydantoin derivatives, ethylenediamine and ethylenediaminetetraacetic acid (EDTA). The stabilizer or the complexing agent may be used singly or in combination of two or more.

In addition to the above components, additives such as a known surfactant, a pH adjuster, a buffer, a leveler, a stress moderator, and the like may be added to the electroless silver plating solution.

The electroless silver plating solution may have a solution temperature in the range of 0 to 80 ℃. If the temperature of the electroless silver plating solution is 0 ℃ or higher, the silver deposition rate is sufficiently high, and the time for obtaining a predetermined amount of deposited silver can be shortened. If the temperature of the electroless silver plating solution is 80 ℃ or lower, the loss of the reducing agent due to the self-decomposition reaction and the reduction in the stability of the electroless silver plating solution can be suppressed. If the temperature is set to 10 to 60 ℃, the stability of the electroless silver plating solution can be further improved.

The pH of the electroless silver plating solution (e.g., reduced electroless silver plating solution) is, for example, 1 to 14. The stability of the plating solution can be further improved by adjusting the pH of the plating solution to about 6 to 13. As the pH adjustment of the plating solution, in general, when the pH is lowered, an acid having the same kind of anion moiety as that of the water-soluble silver salt is used (for example, sulfuric acid in the case of using silver sulfate as the water-soluble silver salt, and nitric acid in the case of using silver nitrate as the water-soluble silver salt). In the case of raising the pH of the electroless silver plating solution, alkali metal hydroxide, ammonia, or the like is used.

< gold >

In the case where the second layer 105 contains gold, the second layer 105 can be formed by electroless gold plating, for example. As the electroless gold plating solution, a displacement type gold plating solution (for example, manufactured by Hitachi chemical Co., Ltd., trade name "HGS-100"), a reduction type gold plating solution (for example, manufactured by Hitachi chemical Co., Ltd., trade name "HGS-2000"), or the like can be used. When the substitution type is compared with the reduction type, the reduction type is preferably used from the viewpoint of less voids and easy securing of the coating area.

< cobalt >

In the case where the second layer 105 contains cobalt, the second layer 105 can be formed by electroless cobalt plating, for example. Examples of the cobalt supply source used in the electroless cobalt plating solution include cobalt sulfate, cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt carbonate.

As the reducing agent used in the electroless cobalt plating solution, for example, there can be used: hypophosphites such as sodium hypophosphite, ammonium hypophosphite, and nickel hypophosphite, and hypophosphorous acid. A stabilizer or a complexing agent (aliphatic carboxylic acid or the like) may be added to the electroless cobalt plating solution. The stabilizer or the complexing agent may be used singly or in combination of two or more.

The temperature (bath temperature) of the electroless cobalt plating solution may be 40 ℃ or higher, or 50 ℃ or higher, from the viewpoint of obtaining a sufficient plating rate. From the viewpoint of stably holding the electroless cobalt plating solution, the temperature (bath temperature) of the electroless cobalt plating solution may be 90 ℃ or lower, or may be 80 ℃ or lower.

The conductive particles 100b according to embodiment 2 described above also exhibit the same operational advantages as those of embodiment 1. In embodiment 1, the first layer 104 is an outermost layer of the conductive particle 100 a. When the conductive particles 100a are dispersed in an anisotropic conductive adhesive, for example, nickel contained in the first layer 104 may be eluted into the adhesive and migrate. The transferred nickel may lower the insulation reliability of the anisotropic conductive adhesive. In contrast, the metal layer of embodiment 2 has the second layer 105 provided on the first layer 104, and the second layer 105 contains a metal selected from the group consisting of a noble metal and cobalt. In this case, the outermost layer of the conductive particles 100b becomes the second layer 105. Since the second layer 105 has a function of preventing nickel from being eluted from the first layer 104, the occurrence of migration of nickel can be suppressed. Further, the second layer 105 is less likely to be oxidized, and thus the conductive property of the conductive particles 100b is less likely to be deteriorated. By having the second layer 105 of the conductive particles 100b, the number, size, and shape of the protrusions 109 can be highly controlled.

(embodiment 3)

The following describes the insulated coated conductive particle according to embodiment 3. In the description of embodiment 3, redundant description with embodiment 1 and embodiment 2 is omitted, and portions different from embodiment 1 and embodiment 2 are described. That is, the descriptions of embodiment 1 and embodiment 2 may be used as appropriate in embodiment 3 within the technical range.

< insulation coated conductive particle >

Fig. 5 is a schematic cross-sectional view showing the insulating coated conductive particle according to the present embodiment. An insulating coated conductive particle 200 shown in fig. 5 includes a conductive particle 100a according to embodiment 1 and an insulating particle (insulating coated portion) 210 that coats at least a part of the surface of the first layer 104.

The average particle diameter of the insulating particles 210 is an average particle diameter calculated from the diameter of a perfect circle having the same area as the area of the insulating particles 210 on the orthographic projection surface of the insulating particles 210. The average particle diameter of the insulating particles 210 is, for example, 20 to 500 nm. When the average particle diameter of the insulating particles 210 is within the above range, the insulating particles 210 adsorbed to the conductive particles 100a, for example, easily function effectively as an insulating film. Further, the electrical conductivity in the direction of pressurization of the connection is likely to be good. The average particle diameter of the insulating particles 210 can be measured by, for example, a specific surface area conversion method using a BET method or an X-ray small angle scattering method.

From the viewpoint of easily reducing the resistance and easily suppressing the increase in the resistance with time, the average particle diameter of the insulating particles 210 may be 1/10 or 1/15 or less with respect to the average particle diameter of the conductive particles 100 a. From the viewpoint of obtaining more excellent insulation reliability, the average particle diameter of the insulating particles 210 may be greater than or equal to 1/20 with respect to the average particle diameter of the conductive particles 100 a.

The insulating particles 210 coat the surface of the conductive particles 100a so that the coverage of the conductive particles 100a with the insulating particles 210 is, for example, 20 to 70%. From the viewpoint of more reliably obtaining the effects of insulation and conductivity, the coverage may be 20 to 60%, 25 to 60%, or 28 to 55%. The "coverage ratio" is a ratio of the surface area of the insulating particles 210 in concentric circles having a diameter of 1/2 of the diameter of the insulating coated conductive particle 200 on the orthographic projection surface of the insulating coated conductive particle 200. Specifically, the image obtained by observing the insulating coated conductive particles 200 on which the insulating particles 210 are formed with an SEM at a magnification of 3 ten thousand was analyzed, and the ratio of the insulating particles 210 to the surface of the insulating coated conductive particles 200 was calculated.

Examples of the insulating particles 210 that coat the conductive particles 100a include organic polymer compound fine particles and inorganic oxide fine particles. When inorganic oxide fine particles are used as the insulating particles 210, insulation reliability can be easily improved, and when organic polymer compound fine particles are used, on-resistance can be easily reduced.

The organic polymer compound may be any compound having thermal softening properties, and specifically, the following compounds may be used: polyethylene, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylate copolymer, polyester, polyamide, polyurethane, polystyrene, styrene-divinylbenzene copolymer, styrene-isobutylene copolymer, styrene-butadiene copolymer, styrene- (meth) acrylic acid copolymer, ethylene-propylene copolymer, (meth) acrylate-based rubber, styrene-ethylene-butylene copolymer, phenoxy resin, solid epoxy resin, and the like. The organic polymer compound may be used alone or in combination of two or more.

Examples of the inorganic oxide include those containing a metal selected from the group consisting of silicon, aluminum, zirconium, titanium, niobium, zinc, tin, cerium and magnesiumAn oxide of at least one element of the group. The inorganic oxide may be used singly or in combination of two or more. Among the inorganic oxides, silica is also preferable. Of the silicas, aqueous dispersion colloidal Silica (SiO)₂) Since the surface has hydroxyl groups, the composition is particularly suitable because it has excellent bondability to conductive particles, and can easily be made uniform in particle size and inexpensive. Examples of commercially available products of such fine particles of inorganic oxide include Snowtex, Snowtex UP (trade name, manufactured by Nissan chemical industries Co., Ltd.), and Quartron PL series (trade name, manufactured by Hibiscus chemical industries Co., Ltd.).

When the inorganic oxide fine particles have a hydroxyl group on the surface, the hydroxyl group can be modified to an amino group, a carboxyl group, an epoxy group, or the like by a silane coupling agent or the like. However, when the average particle diameter of the inorganic oxide fine particles is 500nm or less, modification may be difficult. In this case, the conductive particles 100a may be coated without modification.

Generally, the inorganic oxide fine particles have hydroxyl groups on the surface thereof, and can be bonded to hydroxyl groups, carboxyl groups, alkoxy groups, alkoxycarbonyl groups, and the like of a surface treatment agent such as a silane coupling agent. Examples of the bonding form include a covalent bond, a hydrogen bond, and a coordinate bond obtained by dehydration condensation.

When the outer surface of the conductive particle 100a contains gold or palladium, it is preferable to use a compound having a mercapto group, a thioether group, a disulfide group, or the like in a molecule, which forms a coordinate bond with these metals, so as to form a functional group such as a hydroxyl group, a carboxyl group, an alkoxy group, or an alkoxycarbonyl group on the surface of the inorganic oxide fine particle. As the above-mentioned compounds, there may be mentioned, for example, thioglycolic acid, 2-mercaptoethanol, methyl thioglycolate, mercaptosuccinic acid, thioglycerol and cysteine.

Noble metals such as gold and palladium, and copper are likely to react with thiol. Nickel and other base metals are difficult to react with mercaptans. Therefore, when the outermost layer of the conductive particles 100a contains a noble metal, copper, or the like, the reaction with thiol is easier than when the outermost layer of the conductive particles 100a contains a base metal.

For example, the method for treating the compound on the surface of gold is not particularly limited, and the compound such as mercaptoacetic acid may be dispersed in an organic solvent such as methanol or ethanol at a concentration of about 10 to 100mmol/L, and the conductive particles 100a having gold as the outermost layer may be dispersed therein.

Next, an example of a method for producing the insulating coated conductive particle 200 according to embodiment 3 from the conductive particle 100a according to embodiment 1 will be described. As a method of coating the surface of the conductive particle 100a with the insulating particle 210, for example, a method of alternately laminating a polymer electrolyte and an insulating particle is cited.

First, (1) a step of dispersing conductive particles 100a in a polymer electrolyte solution, adsorbing a polymer electrolyte on the surfaces of the conductive particles 100a, and then rinsing the particles is performed. Next, (2) a step of dispersing the conductive particles 100a in a dispersion solution of insulating particles, adsorbing the insulating particles on the surfaces of the conductive particles 100a, and then rinsing the conductive particles is performed. Through these steps, the insulating coated conductive particle 200 having a surface coated with the insulating particle 210 in which the polymer electrolyte and the insulating particle are laminated can be produced. (1) The step (1) and the step (2) may be performed in the order of (1) and (2), or may be performed in the order of (2) and (1). (1) The step (2) may be alternately repeated.

As the polymer electrolyte, for example, there can be used: a polymer which is ionized in an aqueous solution and has a charged functional group in the main chain or side chain. For example, a polymer compound having a functional group capable of positively charging such as polyamine or the like may be used, or the same polymer as the above-described cationic polymer used for the surface treatment of the resin particles 101 may be used. Specifically, there may be used: polyethyleneimine (PEI), polyallylamine hydrochloride (PAH), polydiallyldimethylammonium chloride (PDDA), polyvinylpyridine (PVP), polylysine, polyacrylamide, and copolymers obtained by polymerizing one or more monomers that form these polymers. From the viewpoint of high charge density and strong bonding force with a surface and a material having negative charges, polyethyleneimine is preferably used.

A method of repeating the above steps (1) and (2) is called a Layer-by-Layer method (Layer-by-Layer). The alternating lamination method is a method of forming an organic Thin film (Solid Films, 210/211, p831(1992)) published by g. According to the method disclosed in g.decher et al, a base material (e.g., a substrate) is alternately immersed in an aqueous solution of a positively charged polymer electrolyte (polycation) and a negatively charged polymer electrolyte (polyanion), and a group of the polycation and the polyanion adsorbed on the base material by electrostatic attraction is stacked to obtain a composite film (alternately stacked film).

In the alternating lamination method, the charge of the material formed on the substrate and the oppositely charged material in the solution are attracted to each other by electrostatic attraction, and film growth is performed. Therefore, if the adsorption proceeds and neutralization of the charge occurs, no further adsorption occurs. Therefore, as long as a certain saturation point is reached, the film thickness does not further increase. Lvov et al reported the following methods: an alternating lamination method is applied to fine particles, and a polymer electrolyte having a charge opposite to the surface charge of the fine particles is laminated by the alternating lamination method using a dispersion of each fine particle of silica, titanium oxide, cerium oxide, or the like (Langmuir, vol.13, (1997) p 6195-6203). When the method reported by lvo is used, a microparticle-laminated film in which silica microparticles and a polymer electrolyte are alternately laminated can be formed by alternately laminating silica microparticles having a negative surface charge and polydiallyldimethylammonium chloride (PDDA), Polyethyleneimine (PEI), or the like, which is a polycation having a charge opposite to that of the silica microparticles.

The insulating coated conductive particle 200 according to embodiment 3 described above also exhibits the same operational advantages as embodiment 1. The insulating particles 210 provided on the outer surface of the first layer 104 make the first layers 104 of the conductive particles 100a less likely to contact each other. Further, the metal foreign matter formed by coating the detached nonconductive inorganic particles 102 with a metal is less likely to be present in the adhesive. Therefore, it is difficult to make the insulating coated conductive particles 200 conduct well, and the insulation reliability of a connection structure or the like using the insulating coated conductive particles 200 is also improved suitably.

In particular, in recent years, anisotropic conductive adhesives for COG mounting and the like are required to have insulation reliability at a narrow pitch of about 10 μm. Such insulation reliability can be achieved by using the insulation-coated conductive particles 200 according to embodiment 3.

As the conductive particles in the insulation-coated conductive particles 200 according to embodiment 3, for example, the conductive particles 100b according to embodiment 2 or the like may be used instead of the conductive particles 100 a. In this case, the insulating coated conductive particles 200 can exhibit the operational effects of the conductive particles 100b according to embodiment 2 in addition to the above operational effects.

(embodiment 4)

The anisotropic conductive adhesive according to embodiment 4 will be described below. In the description of embodiment 4, descriptions overlapping with those of embodiments 1 to 3 are omitted, and descriptions are provided for differences from embodiments 1 to 3. That is, the descriptions of embodiment 1 to embodiment 3 may be appropriately used in embodiment 4 within a technically possible range.

< Anisotropic conductive adhesive >

The anisotropic conductive adhesive according to embodiment 4 contains the conductive particles 100a according to embodiment 1 and an adhesive in which the conductive particles 100a are dispersed.

As the adhesive, for example, a mixture of a heat-reactive resin and a curing agent can be used. Examples of the adhesive include a mixture of an epoxy resin and a latent curing agent, and a mixture of a radical polymerizable compound and an organic peroxide.

As the adhesive, a paste-like or film-like adhesive can be used. In order to form the anisotropic conductive adhesive into a film shape, a thermoplastic resin such as a phenoxy resin, a polyester resin, a polyamide resin, a polyester resin, a polyurethane resin, (meth) acrylic resin, or a polyester polyurethane resin may be blended in the adhesive.

The anisotropic conductive adhesive according to embodiment 4 described above also exhibits the same operational advantages as embodiment 1.

As the conductive particles in the anisotropic conductive adhesive according to embodiment 4, for example, the conductive particles 100b according to embodiment 2 or the like may be used instead of the conductive particles 100 a. In this case, the anisotropic conductive adhesive can exhibit the action and effect of the conductive particles 100b according to embodiment 2. Instead of the conductive particles 100a, the insulating coated conductive particles 200 may be used. In this case, the anisotropic conductive adhesive can exhibit the action and effect of the conductive particles 100b according to embodiment 3.

(embodiment 5)

A connection structure according to embodiment 5 will be described below. In the description of embodiment 5, descriptions overlapping with those of embodiments 1 to 4 are omitted, and descriptions of portions different from those of embodiments 1 to 4 are omitted. That is, the descriptions of embodiments 1 to 4 can be used as appropriate in embodiment 5 within the technical range.

< connection Structure >

A connection structure according to embodiment 5 will be described. The connection structure according to the present embodiment includes: the insulating coating layer includes a first circuit member having a first circuit electrode, a second circuit member having a second circuit electrode, and a connecting portion disposed between the first circuit member and the second circuit member and containing at least one of the conductive particles and the insulating coating conductive particles. The connecting portion connects the first circuit member and the second circuit member to each other in a state where the first circuit electrode and the second circuit electrode are arranged to face each other. The first circuit electrode and the second circuit electrode are electrically connected to each other by the conductive particles or the insulating coated conductive particles in a deformed state.

Next, a connection structure according to embodiment 5 will be further described with reference to fig. 6. Fig. 6 is a schematic cross-sectional view showing a connection structure according to embodiment 5. The connection structure 300 shown in fig. 6 includes: a first circuit member 310 and a second circuit member 320 facing each other, and a connection portion 330 disposed between the first circuit member 310 and the second circuit member 320. Examples of the connection structure 300 include portable products such as a liquid crystal display, a personal computer, a mobile phone, a smartphone, and a tablet computer.

The first circuit member 310 includes a circuit board (first circuit board) 311 and a circuit electrode (first circuit electrode) 312 disposed on a main surface 311a of the circuit board 311. The second circuit member 320 includes a circuit board (first circuit board) 321, and a circuit electrode (second circuit electrode) 322 disposed on a main surface 321a of the circuit board 321.

Specific examples of one of the

circuit members

310 and 320 include: chip components such as IC chips (semiconductor chips), resistor chips, capacitor chips, and driver ICs; a rigid (rigid) type package substrate, and the like. These circuit members include circuit electrodes, and generally include a plurality of circuit electrodes. Specific examples of the other of the circuit member 310 and the circuit member 320 (the circuit member connected to the one circuit member) include: a flexible tape substrate having a metal wiring, a flexible printed wiring board, a wiring substrate such as a glass substrate on which Indium Tin Oxide (ITO) is deposited, and the like. For example, by using a film-like anisotropic conductive adhesive, these circuit members can be connected to each other efficiently and with high connection reliability. For example, the anisotropic conductive adhesive according to embodiment 4 is suitable for COG mounting or COF mounting of a chip component having a plurality of fine circuit electrodes on a wiring board.

The connection portion 330 includes a cured material 332 of an adhesive and insulating coated conductive particles 200 dispersed in the cured material 332. As the connection portion 330, for example, the film-shaped anisotropic conductive adhesive described in embodiment 4 can be used. In the connection structure 300, the circuit electrode 312 and the circuit electrode 322 facing each other are electrically connected to each other through the insulating coated conductive particles 200. More specifically, as shown in fig. 6, the conductive particles 100a in the insulating coated conductive particles 200 are deformed by compression and electrically connected to both the

circuit electrodes

312 and 322. On the other hand, the insulating particles 210 are interposed between the conductive particles 100a in the direction intersecting the compression direction with respect to the conductive particles 100a, so that the insulating property between the insulating coated conductive particles 200 can be maintained. Therefore, the insulation reliability at a narrow pitch (for example, a pitch on the order of 10 μm) can be further improved. Depending on the application, the insulating-coated conductive particles 200 may be replaced with the

conductive particles

100a and 100b that are not coated with an insulating material.

The connection structure 300 is obtained by: the first circuit member 310 having the circuit electrode 312 and the second circuit member 320 having the circuit electrode 322 are arranged so that the circuit electrode 312 and the circuit electrode 322 face each other, an anisotropic conductive adhesive is interposed between the first circuit member 310 and the second circuit member 320, and the circuit electrode 312 and the circuit electrode 322 are electrically connected by heating and pressing them. The first circuit member 310 and the second circuit member 320 are bonded by a cured product 332 of the adhesive.

< method for producing connection Structure >

A method for manufacturing the connection structure according to embodiment 5 will be described with reference to fig. 7. Fig. 7 is a schematic cross-sectional view for explaining an example of the method of manufacturing the connection structure shown in fig. 6. In embodiment 5, the anisotropic conductive adhesive is thermally cured to produce a connection structure.

First, the first circuit member 310 and the anisotropic conductive adhesive 330a are prepared. In the present embodiment, an adhesive film (anisotropic conductive adhesive film) formed into a film shape is used as the anisotropic conductive adhesive 330 a. The anisotropic conductive adhesive 330a contains insulating coated conductive particles 200 and an insulating adhesive 332 a.

Next, the anisotropic conductive adhesive 330a is placed on the main surface 311a (the surface on which the circuit electrodes 312 are formed) of the first circuit member 310. Then, as shown in fig. 7(a), the anisotropic conductive adhesive 330a is pressed in the directions a and B. As a result, as shown in fig. 7(b), the anisotropic conductive adhesive 330a is laminated on the first circuit member 310.

Next, as shown in fig. 7(c), the second circuit member 320 is placed on the anisotropic conductive adhesive 330a so that the circuit electrodes 312 face the circuit electrodes 322. Then, while heating the anisotropic conductive adhesive 330a, the entire (the first circuit member 310 and the second circuit member 320) is pressed along the direction a and the direction B shown in fig. 7 c.

The anisotropic conductive adhesive 330a is cured by heating to form the connection portion 330, and the connection structure 300 as shown in fig. 6 is obtained. The anisotropic conductive adhesive may be in the form of a paste.

In the connection structure 300 according to embodiment 5 described above, the connection portion 330 contains the insulating coated conductive particles 200 according to embodiment 3. According to the connection structure 300, the circuit electrode 312 and the circuit electrode 322 are electrically connected to each other well by the insulating-coated conductive particles 200. Therefore, even when the area of the circuit electrode 312 and the circuit electrode 322 is small and the number of the insulating coated conductive particles 200 trapped between the

circuit electrodes

312 and 322 is small, excellent conduction reliability is exhibited for a long period of time. Further, since the insulating coated conductive particles 200 include the insulating particles 210, the first layers 104 of the insulating coated conductive particles 200 in the connection portion 330 are less likely to contact each other. Therefore, even when the pitch between the electrodes provided in the circuit electrode 312 (in the circuit electrode 322) is, for example, 10 μm or less, the insulating coated conductive particles 200 in the connection portion 330 are not easily electrically connected to each other, and the insulation reliability of the connection structure 300 is suitably improved.

The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. For example, in the above embodiment, the coefficient of variation of the first non-conductive inorganic particles 102a and the second non-conductive inorganic particles 102b is less than 20%, but the present invention is not limited thereto. Similarly, the number of the first nonconductive inorganic particles 102a may not necessarily be greater than or equal to 2 times the number of the second nonconductive inorganic particles 102b on the surface within a concentric circle having a diameter 1/2 of the diameter of the resin particle 101 in the orthographic projection plane of the resin particle 101. In the conductive particles, the number of the first protrusions may not be necessarily greater than or equal to 20, the number of the second protrusions may not be necessarily greater than or equal to 20, and the number of the third protrusions may not be necessarily greater than or equal to 5 and less than or equal to 20. The non-conductive inorganic particles 102 may not be subjected to the hydrophobic treatment, and the resin particles 101 may not be coated with the cationic polymer.

Examples

The present invention will be described in more detail below with reference to examples and comparative examples. The present invention is not limited to the following examples.

< example 1>

[ production of conductive particles ]

(step a) coating of the surface of the resin particle with a cationic polymer

2g of crosslinked polystyrene particles having an average particle diameter of 3.0 μm (trade name "Soliostar", manufactured by Kabushiki Kaisha Co., Ltd.) were added to an aqueous solution prepared by dissolving 3g of a 30 mass% polyethyleneimine aqueous solution having an average molecular weight of 7 ten thousand (M.W. 7 ten thousand) (manufactured by Wako pure chemical industries, Ltd.) in 100ml of pure water, and the mixture was stirred at room temperature for 15 minutes. Subsequently, the resin particles were removed by filtration using a membrane filter (manufactured by Merck Millipore) of Φ 3 μm. The resin particles on the membrane filter were washed 2 times with 200g of ultrapure water to remove non-adsorbed polyethyleneimine, thereby obtaining polyethyleneimine-adsorbed resin particles.

(step b-1) coating of the surfaces of the first non-conductive inorganic particles with the hydrophobizing agent

As the first nonconductive inorganic particles, vapor phase hydrophilic spherical silica powder having an average particle diameter of 60nm was used. 100g of the spherical silica powder was contained in a vibration fluidized bed apparatus (product of Central chemical engineering Co., Ltd., trade name "model VUA-15 of vibration fluidized bed apparatus"). Next, while the spherical silica was fluidized by air circulated by a suction fan, 1.5g of water was sprayed and fluidized for 5 minutes. Next, 2.5g of HMDS (hexamethyldisilazane) (product name "TSL-8802" manufactured by Meiji Seiko Seisakusho Co., Ltd.) was sprayed and mixed by fluidization for 30 minutes. The hydrophobization degree of the obtained hydrophobic spherical silica fine powder was measured by a methanol titration method. The degree of hydrophobization of the first nonconductive inorganic particles was measured by the following method, and the degree of hydrophobization was 70%.

(step b-2) coating of the surfaces of the second nonconductive inorganic particles with the hydrophobizing agent

As the second nonconductive inorganic particles, 100g of spherical silica powder was stored in a vibration fluidized bed apparatus (product of Central chemical engineering Co., Ltd., trade name "vibration fluidized bed apparatus VUA-15 type") using a vapor phase hydrophilic spherical silica powder having an average particle diameter of 120nm, and 1.5g of water was sprayed and mixed for 5 minutes while making the spherical silica powder flow by air circulated by a suction fan. Next, 2.5g of HMDS (product name "TSL-8802" manufactured by Meiji Gaoxin materials Japan contract Co., Ltd.) was sprayed and mixed for 30 minutes by fluidization. The hydrophobization degree of the obtained hydrophobic spherical silica fine powder was measured by a methanol titration method. The degree of hydrophobization of the second nonconductive inorganic particles was measured by the following method, and the degree of hydrophobization was 70%.

(step c) step of electrostatically bonding the first nonconductive inorganic particles and the second nonconductive inorganic particles to the surfaces of the resin particles

2g of resin particles having polyethylene imine adsorbed thereon were added to methanol, and the mixture was stirred at room temperature for 5 minutes while being irradiated with ultrasonic waves having a resonance frequency of 28kHz and an output of 100W. Then, 0.025g of the first nonconductive inorganic particles hydrophobized with HMDS and 0.025g of the second nonconductive inorganic particles hydrophobized with HMDS were added to the methanol, and the mixture was further stirred at room temperature for 5 minutes while being irradiated with ultrasonic waves having a resonance frequency of 28kHz and an output of 100W. Thus, resin particles (particles a) having the first nonconductive inorganic particles and the second nonconductive inorganic particles electrostatically adsorbed thereon are obtained. The amount of the particles a having the first nonconductive inorganic particles and the second nonconductive inorganic particles electrostatically adsorbed thereto was 2.05 g.

(step d) Palladium catalyst imparting step

2.05g of the particles A were added to 100mL of a palladium catalyst solution adjusted to pH 1.0 and containing 20 mass% of a palladium catalyst (product of Hitachi chemical Co., Ltd., trade name: HS 201). Then, the mixture was stirred at 30 ℃ for 30 minutes while ultrasonic waves having a resonance frequency of 28kHz and an output of 100W were irradiated. Subsequently, the mixture was filtered through a 3 μm-diameter membrane filter (manufactured by merck millipore corporation), and then washed with water, thereby adsorbing the palladium catalyst on the surface of the particles a. Then, the particles a were added to a 0.5 mass% dimethylamine borane solution adjusted to pH 6.0, and stirred at 60 ℃ for 5 minutes while irradiating ultrasonic waves having a resonance frequency of 28kHz and an output of 100W, to obtain 2.05g of particles B having a palladium catalyst fixed thereto. Then, 2.05g of the particles B having the palladium catalyst fixed thereto were immersed in 20mL of distilled water, and then the particles B were ultrasonically dispersed, thereby obtaining a resin particle dispersion liquid.

(step e) formation of layer a of the first layer

The particle B dispersion obtained in step d was diluted with 1000mL of water heated to 80 ℃ and 1mL of a 1g/L aqueous bismuth nitrate solution was added as a plating stabilizer. Subsequently, 80mL of an electroless nickel plating solution for forming a layer a having the following composition (which is an aqueous solution containing the following components, and 1g/L of a bismuth nitrate aqueous solution was added to 1L of the plating solution, in the same manner as below) was added dropwise to the particle B dispersion at a dropping rate of 5 mL/min. After the completion of the dropwise addition, the dispersion to which the plating solution was added was filtered after 10 minutes. After washing the filtrate with water, the filtrate was dried by a vacuum drier at 80 ℃. Particles C having a layer a containing a nickel-phosphorus alloy coating having a film thickness of 80nm as shown in Table 1-1 were formed. The amount of the particles C obtained by forming the layer a was 4.05 g. The composition of the electroless nickel plating solution for forming the layer a of the first layer was as follows.

Nickel sulfate … … … … … … 400g/L

… … … … 150g/L sodium hypophosphite

Sodium citrate … … … … … … 120g/L

Aqueous bismuth nitrate solution (1g/L) … 1mL/L

(step f) formation of layer b as the first layer

4.05g of the particles C obtained in step e were washed with water and filtered, and then dispersed in 1000mL of water heated to 70 ℃. To this dispersion, 1mL of a 1g/L aqueous bismuth nitrate solution was added as a plating stabilizer. Subsequently, 20mL of an electroless nickel plating solution for forming a layer b having the following composition was added dropwise at a dropping rate of 5 mL/min. After the completion of the dropwise addition, the dispersion to which the plating solution was added was filtered after 10 minutes. After washing the filtrate with water, the filtrate was dried by a vacuum drier at 80 ℃. Particles D (conductive particles) having a layer b containing a nickel-phosphorus alloy coating film having a film thickness of 20nm as shown in Table 1-1 were formed. The particle D obtained by forming the b layer was 4.55 g. The composition of the electroless nickel plating solution for forming the layer b of the first layer was as follows.

Nickel sulfate … … … … … … 400g/L

… … … … 150g/L sodium hypophosphite

… 60g/L sodium tartrate dihydrate

Aqueous bismuth nitrate solution (1g/L) … 1mL/L

[ evaluation of conductive particles ]

The conductive particles, or the resin particles and the non-conductive inorganic particles (first non-conductive inorganic particles and second non-conductive inorganic particles) contained in the conductive particles were evaluated based on the following items. The results are shown in tables 1-1 and 1-2.

(degree of hydrophobization (%))

The hydrophobization degree of the conductive particles was measured by the following method. First, 50ml of ion-exchanged water and 0.2g of a sample (conductive particles) were put into a beaker, and methanol was added dropwise from a burette while stirring with a magnetic stirrer. As the methanol concentration in the beaker increases, the powder gradually settles down, and the mass fraction of methanol in the methanol-water mixed solution at the end point of the total amount precipitation is defined as the degree of hydrophobization (%) of the conductive particles.

(average particle diameter of non-conductive inorganic particles)

Regarding the particle size of the non-conductive inorganic particles, first, an image obtained by observation at a magnification of 10 ten thousand times by SEM (product name "S-4800" manufactured by hitachi high and new technologies, ltd.) was analyzed, and the area of each of 500 particles was measured. Next, the diameter of the particles when converted into circles was calculated as the average particle diameter of the nonconductive inorganic particles. The average particle diameter of the first non-conductive inorganic particles and the average particle diameter of the second non-conductive inorganic particles are determined. Further, the ratio of the standard deviation of the particle diameter to the obtained average particle diameter was calculated as a percentage and used as a Coefficient of Variation (CV).

(measurement of the Borda potential)

The interface potentials of various particles to be measured are measured by the following method. For measuring the landed potential, Zetasizer ZS (product name, manufactured by Malvern Instruments) was used. First, the dispersion was diluted so that each particle to be measured became about 0.02 mass%. Then, the interfacial potential was measured under four conditions of methanol alone, a mixed solvent of methanol having a pH of 1, a pH of 7, and a pH of 10.5 and ion-exchanged water in total. In the mixed solvent of methanol and ion-exchanged water, the ratio of methanol was set to 10 mass%, and the pH was adjusted by sulfuric acid or potassium hydroxide. The above-mentioned interfacial potential is measured for each particle to be measured.

(evaluation of film thickness and composition)

A cross section was cut by a microtome method so as to pass through the vicinity of the center of the obtained conductive particle. The cross section was observed at a magnification of 25 ten thousand times using a TEM (product name "JEM-2100F" manufactured by Nippon electronics Co., Ltd.). The sectional areas of the a layer, the b layer, and the second layer of the first layer were estimated from the obtained images, and the film thicknesses of the a layer, the b layer, and the second layer of the first layer were calculated from the sectional areas (in example 1, since the second layer was not formed, only the film thicknesses of the a layer and the b layer of the first layer were measured). When calculating the film thickness of each layer based on the cross-sectional area, the cross-sectional area of each layer in the cross-section having a width of 500nm was read by image analysis, and the height when converted into a rectangle having a width of 500nm was calculated as the film thickness of each layer. The average value of the film thickness calculated for 10 conductive particles is shown in Table 1-1. In this case, when it is difficult to distinguish the a layer and the b layer of the first layer, the a layer and the b layer of the first layer are clearly distinguished by the compositional analysis by EDX (product name "JED-2300" manufactured by japan electronics corporation) attached to TEM, and the sectional areas of the layers are estimated to measure the film thickness. The content (purity) of the elements in the a-layer and the b-layer of the first layer was calculated from the EDX plot data. Details of a method for producing a sample (a cross-sectional sample of conductive particles) in the form of a film cut piece, details of a drawing method by EDX, and details of a method for calculating the element content in each layer will be described later.

(evaluation of non-conductive inorganic particles adsorbed on the surface of resin particles)

{ coverage ratio of non-conductive inorganic particles }

The coverage of the non-conductive inorganic particles present in the concentric circles having a diameter of 1/2, which is the diameter of the particles a and the particles B, on the orthographic projection surfaces of the particles a and the particles B obtained after the steps c and d, respectively, was calculated. Specifically, the non-conductive inorganic particles and the resin particles are distinguished by image analysis within a concentric circle of 1/2 diameter, which is the diameter of the particle A, B, in the orthographic projection surfaces of the particle a and the particle B. Then, the area ratio of the non-conductive inorganic particles present in the concentric circles was calculated, and this ratio was used as the coverage of the non-conductive inorganic particles. The coating rates of the silica particles in the particles a and the particles B were calculated, respectively, and the influence of the step d (palladium catalyst application step) on the adsorption property of the nonconductive inorganic particles on the surface of the resin particles was evaluated. The coverage of the non-conductive inorganic particles is the sum of the coverage of the first non-conductive inorganic particles and the coverage of the second non-conductive inorganic particles.

Specifically, the coverage of the non-conductive inorganic particles was evaluated based on images obtained by observing the particles a and the particles B at 3 ten thousand times by SEM, respectively. Fig. 8 shows an SEM image of the particles B observed after the step d in example 1.

{ diameter and number of non-conductive inorganic particles }

In the orthographic projection surfaces of the particles a and B obtained after the steps c and d, the diameters and the numbers of the nonconductive inorganic particles present in the concentric circles having 1/2 diameters which are the diameters of the particles a and B were calculated, respectively. The influence of the adsorption property of the non-conductive inorganic particles on the surface of the resin particles in the step d (palladium catalyst application step) was evaluated by calculating the number of the non-conductive inorganic particles in each of the particles a and B.

Specifically, the number of silica particles was evaluated based on an image obtained by observing the particles a and B by 10 ten thousand times by SEM. The area of each of the nonconductive inorganic particles was measured, and the diameter of a perfect circle having the same area as the area was calculated as the diameter of the nonconductive inorganic particle. The nonconductive inorganic particles were classified based on the diameter ranges shown in table 1-2, and the number of nonconductive inorganic particles in each range was determined. Fig. 9 shows an SEM image of the particles B observed after the step d in example 1. Fig. 9 is a portion within a concentric circle of 1/2 diameter with the diameter of particle B.

(evaluation of protrusions formed on the surface of conductive particles)

{ coverage of protrusions }

The coverage (area ratio) of the protrusions on the surface of the conductive particles was calculated based on SEM images obtained by observing the conductive particles at 3 ten thousand times by SEM. Specifically, the projection forming portion and the flat portion are distinguished by image analysis within a concentric circle having a diameter of 1/2 which is the diameter of the conductive particle in the orthographic projection plane of the conductive particle. Then, the area ratio of the protrusion forming portions existing in the concentric circles was calculated, and the ratio was defined as the coverage of the protrusions. Fig. 10 shows the results of observation of the particles D in example 1 by SEM.

{ diameter and number of protrusions }

On the orthographic projection surface of the conductive particles, the diameter and the number of protrusions existing within a concentric circle having a diameter of 1/2 which is the diameter of the conductive particles were calculated.

Specifically, the image obtained by observing the conductive particles at 10 ten thousand times by SEM was analyzed to define the outline of the protrusion. Next, the area of the protrusion (the area of the outline of the protrusion partitioned by the recess between the protrusions) is measured, and the diameter of a perfect circle having the same area as the area is calculated as the diameter (outer diameter) of the protrusion. Fig. 11 shows the result of observing the particles D in example 1 by SEM.

The protrusions were classified based on the range of diameters shown in Table 1-2, and the number of protrusions in each range was determined. Fig. 11 is a portion within a concentric circle of 1/2 diameter with the diameter of particle D.

(method of producing a sample of a section of conductive particle)

The method for producing the cross-sectional sample of the conductive particles will be described in detail. A cross-sectional sample having a thickness of 60nm ± 20nm (hereinafter referred to as a "thin film slice for TEM measurement") for TEM analysis and STEM/EDX analysis of a cross section of a conductive particle was prepared by the microtomy method as follows.

In order to stably perform the film forming process, conductive particles are dispersed in a casting resin. Specifically, 1.0g of diethylenetriamine (trade name "epomout curing agent 27-772", manufactured by Refine Tec corporation) was mixed with 10g of a mixture of bisphenol a type liquid epoxy resin, butyl glycidyl ether and other epoxy resins (trade name "epomout main agent 27-771", manufactured by Refine Tec corporation). Stirring was carried out using a spatula and it was confirmed by visual inspection that the mixture was homogeneous. After 0.5g of the dried conductive particles was added to 3g of the mixture, stirring was performed using a spatula until uniform. The mixture containing the conductive particles was poured into a mold for resin casting (manufactured by d.s.k. sakazam corporation, trade name "silicone-embedded plate type II"), and allowed to stand at normal temperature (room temperature) for 24 hours. It was confirmed that the casting resin had solidified, and a resin cast of conductive particles was obtained.

A thin film slice for TEM measurement was prepared from a resin casting containing conductive particles using a microtome (product of Leica Microsystems, Ltd., trade name "EM-UC 6"). In order to prepare a thin film slice for TEM measurement, first, the tip of the resin cast is trimmed to a shape that enables cutting out a thin film slice for TEM measurement, as shown in fig. 12(a), using a glass-made knife fixed to the main body of the microtome.

More specifically, as shown in FIG. 12(b), the resin cast product is trimmed so that the cross-sectional shape of the tip end thereof is a substantially rectangular parallelepiped shape having a length of 200 to 400 μm in the vertical direction and 100 to 200 μm in the horizontal direction. The reason why the transverse length of the cross section is set to 100 to 200 μm is to reduce friction generated between the diamond blade and the sample when a thin film slice for TEM measurement is cut out from a resin cast. This makes it easy to prevent wrinkles and bends in the thin film slice for TEM measurement, and to produce the thin film slice for TEM measurement.

Next, a diamond knife (product name "Cryo Wet" manufactured by DIATONE corporation, width of 2.0mm, angle of 35 ℃) with a boat-shaped dish (boat) was fixed to a predetermined portion of the body of the microtome apparatus. Then, the boat-shaped dish was filled with ion-exchanged water, the setting angle of the knife was adjusted, and the tip of the knife was wetted with ion-exchanged water.

Here, adjustment of the setting angle of the knife will be described with reference to fig. 13. When the setting angle of the knife is adjusted, the angle in the vertical direction, the angle in the left-right direction and the clearance angle can be adjusted. As shown in fig. 13, the term "adjusting the vertical angle" means adjusting the vertical angle of the sample holder so that the sample surface is parallel to the direction of travel of the knife. As shown in fig. 13, the term "adjusting the angle in the left-right direction" means adjusting the angle in the left-right direction of the knife so that the cutting edge of the knife is parallel to the sample surface. As shown in fig. 13, the "clearance angle adjustment" means a minimum angle formed by a surface of the cutting edge of the adjustment blade on the sample side and the direction of travel of the blade. The preferred clearance angle is 5 ~ 10. If the clearance angle is in the above range, the friction between the edge of the knife and the surface of the sample can be reduced, and the knife can be prevented from rubbing the surface of the sample after cutting a thin film slice from the sample.

The distance between the sample and the diamond knife was set to be close to each other while confirming the optical microscope attached to the microtome apparatus main body, and the set value of the microtome apparatus was set so that the knife speed was 0.3 mm/sec and the cut thickness of the thin film became 60 nm. + -. 20nm, and the thin film was cut out from the resin cast. Subsequently, the thin film slice for TEM measurement was floated on the water surface of ion-exchanged water. A copper mesh for TEM measurement (a copper mesh with fine meshes) was pressed from the upper surface of the thin film slice for TEM measurement floating on the water surface, and the thin film slice for TEM measurement was adsorbed on the copper mesh to prepare a TEM sample. The slice of the thin film for TEM measurement obtained by the microtome does not exactly match the set value of the cut thickness of the microtome, and therefore the set value for obtaining a desired thickness is obtained in advance.

(drawing method Using EDX)

The details of the drawing method by EDX will be described. The thin film slice for TEM measurement was fixed to a sample holder (product name "beryllium sample biaxial inclined holder, EM-31640", manufactured by japan electronics corporation) together with a copper mesh, and inserted into a TEM. After the irradiation of the sample with the electron beam was started at an acceleration voltage of 200kV, the electron beam irradiation system was switched to the STEM mode.

The scanning Image observation device was inserted into the position for STEM observation, and after activating software for STEM observation "JEOLSimple Image Viewer" (Version 1.3.5) "(manufactured by japan electronics corporation), thin film slices for TEM measurement were observed. In the cross section of the conductive particles observed therein, a site suitable for EDX measurement was searched and photographed. Here, the "portion suitable for measurement" refers to a portion where the cross section of the metal layer can be observed by cutting the conductive particle near the center thereof. The portion having the inclined cross section and the portion cut at a position deviated from the vicinity of the center of the conductive particle are excluded from the measurement object. In the imaging, the observation magnification is 25 ten thousand times, and the number of pixels of the STEM observation image is 512 dots in the vertical direction and 512 dots in the horizontal direction. If observed under this condition, an observed image with a viewing angle of 600nm can be obtained, but if the apparatus is changed, the viewing angle sometimes changes even at the same magnification, so care must be taken.

In the STEM/EDX analysis, when a thin film slice for TEM measurement is irradiated with an electron beam, the resin particles of the conductive particles and the casting resin contract and thermally expand, and the sample deforms or moves during the measurement. In order to suppress the deformation and movement of the sample in the EDX measurement, the measurement site is irradiated with electron beams for about 30 minutes to 1 hour in advance, and the deformation and movement are confirmed and analyzed.

For STEM/EDX analysis, EDX was moved to a measurement position, and EDX measurement software "analysis station" (manufactured by Nippon electronics Co., Ltd.) was started. In the case of drawing with EDX, since it is necessary to obtain sufficient resolution in drawing, a focus diaphragm device for focusing an electron beam on a target portion is used.

In STEM/EDX analysis, the dot diameter of an electron beam is adjusted within the range of 0.5 to 1.0nm so that the count of characteristic X-rays to be detected (CPS: Counts Per Second) becomes 10,000CPS or more, and after measurement, it is confirmed that the height of the peak of K α ray derived from nickel becomes at least 5,000Counts in an EDX spectrum obtained simultaneously with plotting measurement, and when data is acquired, the number of pixels is set to 256 points in the vertical direction and 256 points in the horizontal direction at the same view angle as that in the STEM observation, and the measurement is performed 1 time in the number of accumulations with the accumulation time Per point set to 20 milliseconds.

The EDX spectra of the first layer, the electroless nickel plating precipitation nuclei and the second layer were extracted as necessary from the obtained EDX mapping data, and the element presence ratio of each portion was calculated. In the calculation of the quantitative values, the total ratio of the noble metal, nickel and phosphorus was defined as 100% by mass, and the mass% concentration of each element was calculated.

Elements other than those described above are not included in the calculation of the quantitative values because the ratio is likely to vary for the following reasons. The proportion of carbon is increased or decreased by the influence of a carbon support film used for the net for TEM measurement or impurities adsorbed on the sample surface during electron beam irradiation. The oxygen ratio may increase due to air oxidation during the period from the time when the TEM sample is prepared to the time when the measurement is performed. Copper will be detected from the copper mesh used for TEM measurements.

{ metallic foreign matter having an outer diameter of 1 μm or more }

Regarding the measurement of the number of metallic foreign matters having an outer diameter of 1 μm or more, 1000 conductive particles were observed at 5 kXmagnification by SEM, and the number of metallic foreign matters having an outer diameter of 1 μm or more, which were found in the process of observing 1000 conductive particles, was counted.

{ Presence or absence of abnormal precipitation section }

The presence or absence of a protrusion (abnormal precipitation portion) having a length of more than 500nm is determined by a method schematically shown in fig. 14. Specifically, 1000 conductive particles 400 were observed at 3 ten thousand times by SEM, and the length 402 of the abnormal deposition portion 401 was obtained by measuring the distance from a straight line connecting both ends in the diameter direction of the base end of the abnormal deposition portion 401 (a straight line connecting the concave portion and the concave portion on both sides of the abnormal deposition portion 401) to the apex of the abnormal deposition portion 401 in the vertical direction. Then, the number of conductive particles having an abnormal deposition portion with a length exceeding 500nm was counted.

(measurement of monodispersion ratio)

0.05g of conductive particles was dispersed in electrolytic water, and a surfactant was added thereto to carry out ultrasonic dispersion for 5 minutes (trade name "US-4R" manufactured by AS-One corporation, high-frequency output: 160W, oscillation frequency: 40kHz mono-frequency). The dispersion of conductive particles was poured into a sample cup of coulter mulisizer II (trade name, manufactured by beckmann coulter corporation), and the monodispersion rate of 50000 conductive particles was measured. The monodispersion ratio is calculated by the following formula, and the particle aggregation in the water solvent is determined based on the value thereof based on the following criteria.

Monodispersion ratio (%) { first peak particle number (s)/total particle number(s) } × 100

[ production of insulating particles ]

The monomer was added to 400g of pure water in a 500ml flask in the molar ratio of the insulating particles shown below. The total amount of all monomers was 10 mass% based on pure water. After the replacement with nitrogen, the mixture was heated for 6 hours while stirring at 70 ℃. Stirring speed is 300min^-1(300 rpm). KBM-503 (trade name, product of shin-Etsu chemical Co., Ltd.) was 3-methacryloxypropyltrimethoxysilane.

(molar ratio of insulating particles)

The average particle diameter of the synthesized insulating particles was measured by analyzing the image captured by the SEM. The average particle diameter of the insulating particles was 315 nm.

The Tg (glass transition point) of the insulating particles synthesized was measured using DSC (product name "DSC-7" manufactured by perkin elmer) under conditions that the sample amount was 10mg, the temperature increase rate was 5 ℃/min, and the measurement atmosphere was air.

(preparation of Silicone oligomer)

A glass flask equipped with a stirrer, a condenser and a thermometer was charged with a solution prepared by mixing 118g of 3-glycidoxypropyltrimethoxysilane and 5.9g of methanol. Further, 5g of activated clay and 4.8g of distilled water were added thereto, and the mixture was stirred at 75 ℃ for a certain period of time to obtain an organosilicon oligomer having a weight-average molecular weight of 1300. The resulting silicone oligomer has methoxy or silanol groups as terminal functional groups that react with hydroxyl groups. Methanol was added to the obtained silicone oligomer solution to prepare a treatment solution having a solid content of 20 mass%.

The weight average molecular weight of the silicone oligomer was calculated by measuring it by a Gel Permeation Chromatography (GPC) method and converting it using a calibration curve of standard polystyrene. For the measurement of the weight average molecular weight of the silicone oligomer, a pump (trade name "L-6000" manufactured by Hitachi, Ltd.), a column (Gelpack GL-R420, Gelpack GL-R430, Gelpack GL-R440 (trade name "manufactured by Hitachi chemical Co., Ltd."), and a detector (trade name "L-3300 type RI" manufactured by Hitachi, Ltd.) were used. Tetrahydrofuran (THF) was used as an eluent, and the measurement was carried out at a measurement temperature of 40 ℃ and a flow rate of 2.05 mL/min.

[ production of insulating coated conductive particles ]

A reaction solution was prepared by dissolving 8mmol of mercaptoacetic acid in 200ml of methanol. Then, 2g of conductive particles (particles D in example 1) were added to the above reaction solution, and stirred at room temperature for 2 hours using a Three-One Motor (Three-One Motor) and a stirring blade having a diameter of 45 mm. After washing with methanol, the mixture was filtered through a membrane filter (manufactured by Merck Millipore) having a pore size of 3 μm, whereby 2g of conductive particles having carboxyl groups on the surface thereof were obtained.

Then, a 30% polyethyleneimine aqueous solution having a weight-average molecular weight of 70,000 (Wako pure chemical industries, Ltd.) was diluted with ultrapure water to obtain a 0.3% polyethyleneimine aqueous solution. 2g of the conductive particles having carboxyl groups on the surface thereof were added to a 0.3 mass% polyethyleneimine aqueous solution, and the mixture was stirred at room temperature for 15 minutes. Then, the conductive particles were filtered using a membrane filter (manufactured by merck millipore) having a pore size of 3 μm, and the filtered conductive particles were added to 200g of ultrapure water and stirred at room temperature for 5 minutes. The conductive particles were further filtered by using a membrane filter (manufactured by Merck Millipore) having a pore size of 3 μm, and the membrane filter was washed 2 times with 200g of ultrapure water. By performing these operations, non-adsorbed polyethyleneimine is removed, and conductive particles having surfaces coated with an amino group-containing polymer are obtained.

Next, the insulating particles were treated with a silicone oligomer to prepare a methanol dispersion medium having insulating particles containing a glycidyl oligomer on the surface (methanol dispersion medium of insulating particles).

The conductive particles having surfaces coated with the amino group-containing polymer are immersed in methanol, and a methanol dispersion medium of insulating particles is dropped into the methanol to prepare insulating coated conductive particles. The obtained insulating coated conductive particles were treated with a condensing agent and octadecylamine, and the surfaces thereof were washed and hydrophobized. Then, the resultant was dried by heating at 80 ℃ for 1 hour to prepare insulating coated conductive particles. The average coverage of the insulating particles with respect to the conductive particles was measured by analyzing the image captured by the SEM, and was about 30%.

[ production of Anisotropic conductive adhesive film and connection Structure ]

100g of phenoxy resin (product name "PKHC" of Union carbide Co., Ltd.), 75g of acrylic rubber (a copolymer of 40 parts by mass of butyl acrylate, 30 parts by mass of ethyl acrylate, 30 parts by mass of acrylonitrile and 3 parts by mass of glycidyl methacrylate, molecular weight: 85 ten thousand) was dissolved in 400g of ethyl acetate to obtain a solution. To this solution, 300g of a liquid epoxy resin (product name of Asahi Kasei epoxy Co., Ltd. "NOVACURE HX-3941", epoxy equivalent 185) containing a microcapsule-type latent curing agent was added and stirred to obtain an adhesive solution.

The insulating coated conductive particles were dispersed in the adhesive solution so as to be 9 vol% based on the total amount of the adhesive solution, thereby obtaining a dispersion liquid. The obtained dispersion was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) using a roll coater, and dried by heating at 90 ℃ for 10 minutes to produce an anisotropic conductive adhesive film having a thickness of 25 μm on the separator.

Next, using the produced anisotropic conductive adhesive film, the steps of i) to iii) shown below were performed to form 362 gold bumps (1) (area: about 20 μm by about 40 μm, height: 15 μm), gold bump (2) (area: about 30 μm by about 40 μm, height: 15 μm) and gold bump (3) (area: about 40 μm by about 40 μm, height: 15 μm) (1.7mm × 20mm, thickness: 0.5 μm) and a glass substrate with IZO circuit (thickness: 0.7mm) to obtain a connected structure. The gap of the gold bump (1) is set to 6 μm, the gap of the gold bump (2) is set to 8 μm, and the gap of the gold bump (3) is set to 10 μm. The gap corresponds to the distance between the gold bumps.

i) At 80 ℃ and 0.98MPa (10 kgf/cm)²) An anisotropic conductive adhesive film (2 mm. times.24 mm) was attached to the IZO circuit-equipped glass substrate.

ii) peeling the diaphragm to align the bumps of the chip with the glass substrate with the IZO circuit.

iii) heat and pressure were applied from above the chip at 190 ℃ and 40 gf/bump for 10 seconds to bond the chip and the glass substrate, and to electrically connect the bumps of the chip and the IZO circuit.

[ evaluation of connection Structure ]

The connection structure obtained was subjected to an on-resistance test and an insulation resistance test as follows.

(on-resistance test)

In the connection between the chip electrode (bump) and the IZO circuit, the initial value of the on-resistance and the values of the on-resistance after the moisture absorption heat resistance test (standing at 85 ℃ and 85% humidity for 100 hours, 300 hours, 500 hours, 1000 hours, 2000 hours) were measured. The connection regions of the chip electrodes (bumps) and the IZO circuit are set to about 20 μm × about 40 μm, about 30 μm × about 40 μm, and about 40 μm × about 40 μm. In the connection region of about 20 μm × about 40 μm, the chip electrode and the IZO circuit are set to be connected by 3 conductive particles (trapping conductive particles). In the connection region of about 30 μm × about 40 μm, the chip electrode and the IZO circuit are set to be connected by 6 conductive particles. In the connection region of about 40 μm × about 40 μm, the chip electrode and the IZO circuit are set to be connected by 10 conductive particles. The 20 samples were measured, and the average value thereof was calculated. The on-resistance was evaluated based on the average values obtained according to the following criteria, and the evaluation results are shown in Table 3-1. When the number of bumps was 6, the on-resistance was evaluated to be good when the following a criterion was satisfied 500 hours after the hygroscopic heat resistance test.

A: average value of on-resistance is less than 2 omega

B: the average value of the on-resistances is 2 Ω to 5 Ω

C: the average value of the on-resistances is 5 Ω -10 Ω

D: the average value of the on-resistances is 10 Ω -20 Ω

E: the average value of the on-resistances is greater than or equal to 20 omega

(insulation resistance test)

As the insulation resistance between the chip electrodes (bumps), the initial value of the insulation resistance and the values of the insulation resistance after the migration test (standing for 100 hours, 300 hours, 1000 hours, 2000 hours under the conditions of a temperature of 60 ℃, a humidity of 90%, and an applied voltage of 20V) were measured. Measuring 20 samples, and calculating insulation resistance value of 10 or more in all 20 samples⁹The proportion of the sample of Ω. The measurement was performed for each of the gold bumps (1) to (3). That is, insulation resistance tests were performed for the gold bumps having gaps of 6 μm, 8 μm, and 10 μm, respectively. The insulation resistance was evaluated according to the following criteria based on the obtained ratio. The results are shown in Table 3-1. When the gap was 8 μm, the insulation resistance was evaluated to be good when the following A criteria were satisfied after 1000 hours of the hygroscopic heat resistance test.

A: insulation resistance value of 10 or more⁹The proportion of omega is 100 percent

B: insulation resistance value of 10 or more⁹The proportion of omega is more than or equal to 90 percent and less than 100 percent

C: insulation resistance value of 10 or more⁹The proportion of omega is more than or equal to 80 percent and less than 90 percent

D: insulation resistance value of 10 or more⁹The proportion of omega is more than or equal to 50 percent and less than 80 percent

E: insulation resistance value of 10 or more⁹The proportion of omega is less than 50 percent

< example 2>

The preparation of the conductive particles, the insulating coated conductive particles, the anisotropic conductive adhesive film, and the connection structure, and the evaluation of the conductive particles and the connection structure were carried out in the same manner as in example 1 except that the second nonconductive inorganic particles were changed to the vapor phase hydrophilic spherical silica powder having an average particle diameter of 100nm in (step b-2) of example 1. The results are shown in Table 1-1, Table 1-2 and Table 3-1.

< example 3>

The production of conductive particles, insulation-coated conductive particles, anisotropic conductive adhesive film, and connection structure, and the evaluation of conductive particles and connection structure were carried out in the same manner as in example 1, except that in example 1 (step b-1), the first nonconductive inorganic particles were changed to vapor-phase hydrophilic spherical silica powder having an average particle diameter of 40nm, and in example 2, the second nonconductive inorganic particles were changed to vapor-phase hydrophilic spherical silica powder having an average particle diameter of 100 nm. The results are shown in Table 1-1, Table 1-2 and Table 3-1.

< example 4>

The preparation of conductive particles, insulating coated conductive particles, anisotropic conductive adhesive film, and connection structure, and the evaluation of conductive particles and connection structure were carried out in the same manner as in example 1 except that the amount of the second nonconductive inorganic particles charged in example 1 (step c) was changed to 0.02 g. The results are shown in tables 1 to 3, tables 1 to 4 and tables 3 to 2.

< example 5>

The production of conductive particles, insulating coated conductive particles, anisotropic conductive adhesive film, and connection structure, and the evaluation of conductive particles and connection structure were carried out in the same manner as in example 1 except that the amount of the second nonconductive inorganic particles charged in example 1 (step c) was changed to 0.015 g. The results are shown in tables 1 to 3, tables 1 to 4 and tables 3 to 2.

< example 6>

The preparation of conductive particles, insulating coated conductive particles, anisotropic conductive adhesive film, and connection structure, and the evaluation of conductive particles and connection structure were carried out in the same manner as in example 1 except that the amount of the first nonconductive inorganic particles charged in example 1 (step c) was changed to 0.02 g. The results are shown in tables 1 to 3, tables 1 to 4 and tables 3 to 2.

< example 7>

The production of conductive particles, insulating coated conductive particles, anisotropic conductive adhesive film, and connection structure, and the evaluation of conductive particles and connection structure were carried out in the same manner as in example 1 except that the amount of the first nonconductive inorganic particles charged in example 1 (step c) was changed to 0.015 g. The results are shown in tables 1 to 5, tables 1 to 6 and tables 3 to 3.

< example 8>

4.55g of the particles D prepared in the steps (a) to (f) of example 1 were immersed in 1L of an electroless palladium plating solution (pH: 6) having the following composition to form a second layer. The treatment was carried out at a reaction time of 10 minutes and a temperature of 50 ℃. The average thickness of the second layer was 10nm, and the palladium content in the second layer was 100 mass%. In the same manner as in example 1 except for using the conductive particles, the insulating coated conductive particles, the anisotropic conductive adhesive film, and the connection structure were produced, and the conductive particles and the connection structure were evaluated. The results are shown in tables 1 to 5, tables 1 to 6 and tables 3 to 3. The composition of the electroless palladium plating solution is as follows.

Palladium chloride … … … 0.07.07 g/L

EDTA disodium … 1g/L

… 1g/L of disodium citrate

Sodium formate … … … 0.2.2 g/L

pH……………6

< example 9>

A second layer was formed by immersing 4.55g of the particles D prepared in example 1 (steps a to f) in 100mL/L of a 1L displacement gold plating solution (product of Hitachi chemical Co., Ltd., trade name: HGS-100) at 85 ℃ for 2 minutes and further washing with water for 2 minutes. The treatment was carried out at a reaction time of 10 minutes and a temperature of 60 ℃. The average thickness of the second layer was 10nm, and the gold content in the second layer was almost 100 mass%. In the same manner as in example 1 except for using the conductive particles, the insulating coated conductive particles, the anisotropic conductive adhesive film, and the connection structure were produced, and the conductive particles and the connection structure were evaluated. The results are shown in tables 1 to 5, tables 1 to 6 and tables 3 to 3.

< comparative example 1>

First, example 1 (step a) was performed. Next, in example 1 (step b-1), the first nonconductive inorganic particles were changed to a vapor phase hydrophilic spherical silica powder having an average particle diameter of 25nm, to obtain a spherical silica powder hydrophobized with HMDS. In example 1 (step c), only 0.05g of spherical silica powder having an average particle diameter of 25nm and hydrophobized with HMDS was used instead of 0.025g of the first non-conductive inorganic particles and 0.025g of the second non-conductive inorganic particles. Thereafter, the conductive particles, the insulating coated conductive particles, the anisotropic conductive adhesive film, and the connection structure were produced, and the conductive particles and the connection structure were evaluated in the same manner as in example 1 (step d) and thereafter. The results are shown in Table 2-1, Table 2-2 and Table 4-1.

< comparative example 2>

First, example 1 (step a) was performed. Next, in example 1 (step b-1), the first nonconductive inorganic particles were changed to a vapor phase hydrophilic spherical silica powder having an average particle diameter of 40nm, and a spherical silica powder hydrophobized with HMDS was obtained. In example 1 (step c), only 0.05g of spherical silica powder having an average particle diameter of 40nm and hydrophobized with HMDS was used instead of 0.025g of the first non-conductive inorganic particles and 0.025g of the second non-conductive inorganic particles. Thereafter, the conductive particles, the insulating coated conductive particles, the anisotropic conductive adhesive film, and the connection structure were produced, and the conductive particles and the connection structure were evaluated in the same manner as in example 1 (step d) and thereafter. The results are shown in Table 2-1, Table 2-2 and Table 4-1.

< comparative example 3>

In the same manner as in example 1 except that in example 1 (step c), only 0.05g of spherical silica powder having an average particle diameter of 60nm and hydrophobized with HMDS was changed instead of 0.025g of the first nonconductive inorganic particles and 0.025g of the second nonconductive inorganic particles, the conductive particles, the insulating coated conductive particles, the anisotropic conductive adhesive film, and the connection structure were produced, and the conductive particles and the connection structure were evaluated. The results are shown in Table 2-1, Table 2-2 and Table 4-1.

< comparative example 4>

First, example 1 (step a) was performed. Next, in example 1 (step b-1), the first nonconductive inorganic particles were changed to a vapor phase hydrophilic spherical silica powder having an average particle diameter of 100nm, and a spherical silica powder hydrophobized with HMDS was obtained. In example 1 (step c), only 0.05g of spherical silica powder having an average particle diameter of 100nm and hydrophobized with HMDS was used instead of 0.025g of the first non-conductive inorganic particles and 0.025g of the second non-conductive inorganic particles. Thereafter, the conductive particles, the insulating coated conductive particles, the anisotropic conductive adhesive film, and the connection structure were produced, and the conductive particles and the connection structure were evaluated in the same manner as in example 1 (step d) and thereafter. The results are shown in tables 2-3, 2-4 and 4-2.

< comparative example 5>

In the same manner as in example 1 except that in example 1 (step c), only 0.05g of spherical silica powder having an average particle diameter of 120nm, which was hydrophobized with HMDS, was changed to 0.025g of the first nonconductive inorganic particles and 0.025g of the second nonconductive inorganic particles instead of 0.025g of the first nonconductive inorganic particles and 0.025g of the second nonconductive inorganic particles, the conductive particles, the insulating coated conductive particles, the anisotropic conductive adhesive film, and the connection structure were produced, and the conductive particles and the connection structure were evaluated. The results are shown in tables 2-3, 2-4 and 4-2.

< comparative example 6>

First, example 1 (step a) was performed. Next, the colloidal silica dispersion having an average particle diameter of 100nm was diluted with ultrapure water to obtain a 0.33 mass% silica particle dispersion (0.05 g of the total amount of silica). To this dispersion, the resin particles adsorbed with polyethyleneimine prepared in step (a) were added, and the mixture was stirred at room temperature for 15 minutes. Then, the resin particles were removed by filtration using a membrane filter (manufactured by Merck Millipore) of Φ 3 μm. Since silica was not extracted from the filtrate, it was confirmed that substantially all of the silica particles were adsorbed to the resin particles. The resin particles adsorbed with the silica particles were added to 200g of ultrapure water and stirred at room temperature for 5 minutes. Then, the resin particles were taken out by filtration using a membrane filter (manufactured by Merck Millipore) of Φ 3 μm, and the resin particles on the membrane filter were washed 2 times with 200g of ultrapure water. The washed resin particles were dried by heating at 80 ℃ for 30 minutes and at 120 ℃ for 1 hour, thereby obtaining 2.05g of resin particles having silica particles adsorbed on the surface.

2.05g of the resin particles were irradiated with ultrasonic waves having a resonance frequency of 28kHz and an output of 100W for 15 minutes, and then added to 100mL of a palladium catalyst solution containing 8 mass% of a palladium catalyst (trade name "Atotech Neogenath 834" manufactured by Ato Tech Japan) and stirred at 30 ℃ for 30 minutes while being irradiated with ultrasonic waves. Then, the resin particles were removed by filtration using a membrane filter (manufactured by merck Millipore) of Φ 3 μm, and the resin particles thus removed were washed with water. The washed resin particles were added to a 0.5 mass% dimethylamine borane solution having a pH adjusted to 6.0, to obtain 2.01g of resin particles having a palladium catalyst fixed thereto. Then, 2.01g of the resin particles having the palladium catalyst fixed thereto were immersed in 20mL of distilled water, and then subjected to ultrasonic dispersion, thereby obtaining a resin particle dispersion liquid. Fig. 15 shows the results of observation of the particles dispersed by ultrasonic waves by SEM.

Thereafter, the conductive particles, the insulating coated conductive particles, the anisotropic conductive adhesive film, and the connection structure were produced, and the conductive particles and the connection structure were evaluated in the same manner as in (step e) and thereafter of example 1. The results are shown in tables 2-3, 2-4 and 4-2. Fig. 16 shows the results of observation of the conductive particles after (step f) in SEM comparative example 6.

< comparative example 7>

Crosslinked polystyrene particles having an average particle diameter of 3.0 μm (trade name "Soliostar" manufactured by Japan catalyst Co., Ltd.) were used as the resin particles. While stirring 400mL of an aqueous solution of the cleaning conditioner 231 (manufactured by Rohm and Haas electronic materials Co., Ltd., concentration 40mL/L), 30g of resin particles were put into the solution. Subsequently, the aqueous solution was heated to 60 ℃ and stirred for 30 minutes while applying ultrasonic waves, thereby performing surface modification and dispersion treatment of the resin particles.

The aqueous solution was filtered, and the obtained particles were washed with water 1 time, and then 30g of the particles were dispersed in water to obtain 200mL of slurry. To this slurry, 200mL of an aqueous stannous chloride solution (concentration: 1.5g/L) was added, and the mixture was stirred at room temperature for 5 minutes to perform sensitization treatment for adsorbing tin ions on the particle surfaces. Subsequently, the aqueous solution was filtered, and the obtained particles were washed with water 1 time. Then, 30g of the particles were dispersed in water to prepare 400mL of a slurry, which was then heated to 60 ℃. While stirring the slurry with ultrasonic waves, 2mL of a 10g/L aqueous solution of palladium chloride was added. In this state, the mixture was stirred for 5 minutes to carry out an activation treatment for capturing palladium ions on the surface of the particles. Subsequently, the aqueous solution was filtered, and the obtained particles were washed with water 1 time.

Next, 3L of an electroless plating solution containing an aqueous solution in which 20g/L of sodium tartrate, 10g/L of nickel sulfate and 0.5g/L of sodium hypophosphite were dissolved was heated to 60 ℃. 10g of the above particles were put into the electroless plating solution. This was stirred for 5 minutes, and it was confirmed that hydrogen bubbling was stopped.

Then, 400mL of 200g/L nickel sulfate aqueous solution and 400mL of 200g/L mixed aqueous solution of sodium hypophosphite and 90g/L sodium hydroxide were continuously added to the plating solution containing the particles by a metering pump. The addition rate was set to 3 mL/min. Subsequently, the solution was stirred for 5 minutes while keeping the temperature at 60 ℃, and then the solution was filtered. The filtrate was washed 3 times and dried by a vacuum drier at 100 ℃ to obtain conductive particles having a nickel-phosphorus alloy coating. The obtained conductive particles were observed with a TEM at a magnification of 25 ten thousand times, with a cross section cut by a microtome method so as to pass through the vicinity of the center of the particles. Based on the obtained sectional images, the film thickness was calculated from the average value of the sectional areas, and as a result, the average film thickness of the nickel-phosphorus alloy coating was 105 nm.

In the same manner as in example 1 except for using the conductive particles, the insulating coated conductive particles, the anisotropic conductive adhesive film, and the connection structure were produced, and the connection structure was evaluated. As for the evaluation of the conductive particles, a part of the evaluation was performed in the same manner as in example 1. The results are shown in tables 2 to 5, tables 2 to 6 and tables 4 to 3.

< comparative example 8>

Crosslinked polystyrene particles having an average particle diameter of 3.0 μm (trade name "Soliostar" manufactured by Japan catalyst Co., Ltd.) were used as the resin particles. While stirring 400mL of an aqueous solution of the cleaning conditioner 231 (manufactured by Rohm and Haas electronic materials Co., Ltd., concentration 40mL/L), 7g of resin particles were charged into the aqueous solution. Subsequently, the aqueous solution was heated to 60 ℃ and stirred for 30 minutes while applying ultrasonic waves, thereby performing surface modification and dispersion treatment of the resin particles.

The aqueous solution was filtered, the obtained particles were washed with water 1 time, and 7g of the particles were dispersed in pure water to obtain 200mL of slurry. To this slurry, 200mL of an aqueous stannous chloride solution (concentration: 1.5g/L) was added, and the mixture was stirred at room temperature for 5 minutes to perform sensitization treatment for adsorbing tin ions on the particle surfaces. Subsequently, the aqueous solution was filtered, and the obtained particles were washed with water 1 time. Subsequently, 7g of the particles were dispersed in water to prepare 400mL of a slurry, which was then heated to 60 ℃. While stirring the slurry with ultrasonic waves, 2mL of a 10g/L aqueous palladium chloride solution was added. In this state, the mixture was stirred for 5 minutes to carry out an activation treatment for capturing palladium ions on the surface of the particles. Subsequently, the aqueous solution was filtered, and the obtained particles were washed with water 1 time.

7g of the resulting particles were added to 300mL of pure water, and stirred for 3 minutes to disperse the particles. Then, 2.25g of nickel particles (product name "2007 SUS" manufactured by Mitsui Metal mining Co., Ltd., average particle diameter 50nm) were added as a core material to the dispersion liquid, to obtain particles to which the core material was attached.

The dispersion was further diluted with 1200mL of water, and 4mL of an aqueous bismuth nitrate solution (concentration: 1g/L) was added as a plating stabilizer. Subsequently, 120mL of a mixed solution of 450g/L nickel sulfate, 150g/L sodium hypophosphite, 116g/L sodium citrate, and 6mL of a plating stabilizer (aqueous bismuth nitrate solution (concentration: 1g/L)) was added to the dispersion at an addition rate of 81 mL/min by a metering pump. Then, stirring was carried out until the pH stabilized, and it was confirmed that hydrogen bubbling was stopped.

Then, 650mL of a mixed solution of 450g/L nickel sulfate, 150g/L sodium hypophosphite, 116g/L sodium citrate, and 35mL of a plating stabilizer (aqueous bismuth nitrate solution (concentration: 1g/L)) was added by a quantitative pump at an addition rate of 27 mL/min. Then, stirring was carried out until the pH stabilized, and it was confirmed that hydrogen bubbling was stopped.

Next, the plating solution was filtered, and the filtrate was washed with water. Then, the resultant was dried by a vacuum drier at 80 ℃ to obtain conductive particles having a nickel-phosphorus alloy coating. The obtained conductive particles were observed with a TEM at a magnification of 25 ten thousand times, with a cross section cut by a microtome method so as to pass through the vicinity of the center of the particles. Based on the obtained sectional images, the film thickness was calculated from the average value of the sectional areas, and as a result, the average film thickness of the nickel-phosphorus alloy coating was 101 nm.

In the same manner as in example 1 except that the conductive particles were used, the insulating coated conductive particles, the anisotropic conductive adhesive film, and the connection structure were produced, and the connection structure was evaluated. As for the evaluation of the conductive particles, a part of the evaluation was performed in the same manner as in example 1. The results are shown in tables 2 to 5, tables 2 to 6 and tables 4 to 3.

The conductive particles of comparative example 6 correspond to the conductive particles of patent document 3 described above. The conductive particles of comparative example 7 correspond to the conductive particles of patent document 1 described above. The conductive particles of comparative example 8 correspond to the conductive particles of patent document 2 described above.

[ tables 1-1]

[ tables 1-2]

[ tables 1 to 3]

[ tables 1 to 4]

[ tables 1 to 5]

[ tables 1 to 6]

[ Table 2-1]

[ tables 2-2]

[ tables 2 to 3]

[ tables 2 to 4]

[ tables 2 to 5]

[ tables 2 to 6]

[ Table 3-1]

[ tables 3-2]

[ tables 3 to 3]

[ Table 4-1]

[ tables 4-2]

[ tables 4 to 3]

Description of the symbols

100a, 100b, 400: conductive particles; 101: resin particles; 102: non-conductive inorganic particles; 102 a: first non-conductive inorganic particles; 102 b: second non-conductive inorganic particles; 103: composite particles; 104: a first layer; 105: a second layer; 109: a protrusion; 200: insulating coated conductive particles; 210: insulating particles (insulating coating portion); 300: a connecting structure; 310: a first circuit member; 311. 321: a circuit substrate; 311a, 321 a: a main face; 312. 322: a circuit electrode; 320: a second circuit member; 330: a connecting portion; 330 a: an anisotropic conductive adhesive; 332: curing the product; 332 a: an adhesive; 401: an abnormal precipitation part.

Claims

1. A conductive particle comprising a composite particle having a resin particle and a non-conductive inorganic particle disposed on the surface of the resin particle, and a metal layer covering the composite particle,

the metal layer has protrusions on an outer surface thereof with the non-conductive inorganic particles as cores,

a surface within a concentric circle of 1/2 diameters having a diameter of the resin particle, the non-conductive inorganic particles having greater than or equal to 40 and less than or equal to 200 first non-conductive inorganic particles having a diameter less than 70nm, and having greater than or equal to 5 and less than or equal to 50 second non-conductive inorganic particles having a diameter greater than or equal to 90nm and less than or equal to 150 nm.

2. The conductive particle according to claim 1, the number of the first nonconductive inorganic particles being greater than or equal to 2 times the number of the second nonconductive inorganic particles at a surface within a concentric circle of 1/2 diameters of the diameter of the resin particle.

3. The conductive particle according to claim 1 or 2, wherein the first non-conductive inorganic particle has an average particle diameter in the range of 25 to 70nm and a coefficient of variation of less than 20%,

the second non-conductive inorganic particles have an average particle diameter in the range of 90 to 130nm and a coefficient of variation of less than 20%.

4. The conductive particle according to claim 1 or 2, wherein the surface of the non-conductive inorganic particle is coated with a hydrophobic treatment agent.

5. The conductive particle according to claim 4, wherein the hydrophobizing agent is selected from the group consisting of a silicon nitride-based hydrophobizing agent, a silicone-based hydrophobizing agent, a silane-based hydrophobizing agent, and a titanate-based hydrophobizing agent.

6. The conductive particle according to claim 5, wherein the hydrophobizing agent is selected from the group consisting of hexamethyldisilazane, polydimethylsiloxane, and N, N-dimethylaminotrimethylsilane.

7. The conductive particle according to claim 4, the non-conductive inorganic particle obtained by a methanol titration method has a degree of hydrophobization of 30% or more.

8. The conductive particle according to claim 4, wherein the difference between the interfacial potentials of the resin particle and the non-conductive inorganic particle is greater than or equal to 30mV at a pH of greater than or equal to 1 and a pH of less than or equal to 11.

9. The conductive particle according to claim 1 or 2, wherein the surface of the resin particle is coated with a cationic polymer.

10. The conductive particle according to claim 9, wherein the cationic polymer is selected from the group consisting of polyamine, polyimine, polyamide, polydiallyldimethylammonium chloride, polyvinylamine, polyvinylpyridine, polyvinylimidazole, and polyvinylpyrrolidone.

11. The conductive particle according to claim 10, wherein the cationic polymer is polyethyleneimine.

12. The conductive particle according to claim 9, wherein the non-conductive inorganic particle is adhered to the resin particle by an electrostatic force.

13. The conductive particle according to claim 1 or 2, an average particle diameter of the resin particle is greater than or equal to 1 μm and less than or equal to 10 μm.

14. The conductive particle according to claim 1 or 2, the non-conductive inorganic particle being selected from the group consisting of silica, zirconia, alumina and diamond.

15. The conductive particle according to claim 1 or 2, the metal layer having a first layer containing nickel.

16. The conductive particle according to claim 15, the metal layer having a second layer provided on the first layer,

the second layer contains a metal selected from the group consisting of noble metals and cobalt.

17. A conductive particle comprising a composite particle having a resin particle and a non-conductive inorganic particle disposed on the surface of the resin particle, and a metal layer covering the composite particle,

the protrusions have, on a surface within a concentric circle of 1/2 diameters having the diameter of the conductive particle, 20 or more first protrusions having a diameter of 50nm or more and less than 100nm, 20 or more second protrusions having a diameter of 100nm or more and less than 200nm, and 5 or more and less than 20 third protrusions having a diameter of 200nm or more and less than 350 nm.

18. The conductive particle according to claim 17, wherein the surface of the non-conductive inorganic particle is coated with a hydrophobic treatment agent.

19. The conductive particle according to claim 18, wherein the hydrophobizing agent is selected from the group consisting of a silicon nitride-based hydrophobizing agent, a silicone-based hydrophobizing agent, a silane-based hydrophobizing agent, and a titanate-based hydrophobizing agent.

20. The conductive particle according to claim 19, wherein the hydrophobizing agent is selected from the group consisting of hexamethyldisilazane, polydimethylsiloxane, and N, N-dimethylaminotrimethylsilane.

21. The conductive particle according to any one of claims 18 to 20, wherein a degree of hydrophobization of the non-conductive inorganic particle obtained by a methanol titration method is 30% or more.

22. The conductive particle according to any one of claims 18 to 20, wherein a difference between the interfacial potentials of the resin particle and the non-conductive inorganic particle is greater than or equal to 30mV at a pH of greater than or equal to 1 and a pH of less than or equal to 11.

23. The conductive particle according to any one of claims 17 to 20, wherein the surface of the resin particle is coated with a cationic polymer.

24. The conductive particle according to claim 23, wherein the cationic polymer is selected from the group consisting of polyamine, polyimine, polyamide, polydiallyldimethylammonium chloride, polyvinylamine, polyvinylpyridine, polyvinylimidazole, and polyvinylpyrrolidone.

25. The conductive particle according to claim 24, wherein the cationic polymer is polyethyleneimine.

26. The conductive particle according to claim 23, wherein the non-conductive inorganic particle is adhered to the resin particle by an electrostatic force.

27. The conductive particle according to any one of claims 17 to 20, wherein an average particle diameter of the resin particle is 1 μm or more and 10 μm or less.

28. The conductive particle according to any one of claims 17 to 20, wherein the non-conductive inorganic particle is selected from the group consisting of silica, zirconia, alumina and diamond.

29. The conductive particle according to any one of claims 17 to 20, the metal layer having a first layer containing nickel.

30. The conductive particle of claim 29, the metal layer having a second layer disposed on the first layer,

31. An insulation-coated conductive particle comprising:

the conductive particle as claimed in any one of claims 1 to 30, and

and an insulating coating portion for coating at least a part of an outer surface of the metal layer of the conductive particle.

32. A connection structure body is provided with:

a first circuit member having a first circuit electrode;

a second circuit member opposed to the first circuit member and having a second circuit electrode; and

a connecting portion disposed between the first circuit member and the second circuit member and containing the conductive particle according to any one of claims 1 to 30,

the connecting portion connects the first circuit member and the second circuit member to each other in a state where the first circuit electrode and the second circuit electrode are arranged to face each other,

the first circuit electrode and the second circuit electrode are electrically connected to each other by the conductive particles in a deformed state.

33. A connection structure body is provided with:

a first circuit member having a first circuit electrode;

a connecting portion disposed between the first circuit member and the second circuit member and containing the insulation-coated conductive particle according to claim 31,

the first circuit electrode and the second circuit electrode are electrically connected to each other by the insulating coated conductive particles in a deformed state.

34. An anisotropic conductive adhesive comprising:

the conductive particle as claimed in any one of claims 1 to 30, and

and an adhesive in which the conductive particles are dispersed.

35. The anisotropically conductive adhesive according to claim 34, which is in the form of a film.

36. An anisotropic conductive adhesive comprising:

the insulation-coated conductive particle as defined in claim 31, and

an adhesive in which the insulating coated conductive particles are dispersed.

37. The anisotropically conductive adhesive according to claim 36, which is in the form of a film.

38. A connection structure body is provided with:

a first circuit member having a first circuit electrode;

the anisotropically conductive adhesive according to claim 34 to 37, bonding the first circuit member and the second circuit member,

the first circuit electrode and the second circuit electrode are opposed to each other and electrically connected to each other by the anisotropic conductive adhesive.

39. A method for producing conductive particles, which comprises composite particles and a metal layer covering the composite particles, wherein the composite particles comprise resin particles and non-conductive inorganic particles disposed on the surfaces of the resin particles, the method comprising:

disposing the non-conductive inorganic particles on the surface of the resin particle to form the composite particle; and

a step of covering the composite particles with the metal layer,

in the step of forming the composite particles, 40 or more and 200 or less first nonconductive inorganic particles having a diameter of 70nm or less are disposed on the surface of a concentric circle having a diameter of 1/2 of the diameter of the resin particles, and 5 or more and 50 or less second nonconductive inorganic particles having a diameter of 90nm or more and 150nm or less are disposed.

40. The method for manufacturing a conductive particle according to claim 39, configured in such a manner that: the number of the first non-conductive inorganic particles is greater than or equal to 2 times the number of the second non-conductive inorganic particles at the surface within a concentric circle of 1/2 diameters having the diameter of the resin particle.

41. The method for producing conductive particles according to claim 39 or 40, wherein the first nonconductive inorganic particles have an average particle diameter in the range of 25 to 70nm and a coefficient of variation of less than 20%,

42. The method for producing conductive particles according to claim 39 or 40, wherein in the step of covering the composite particles with the metal layer, a protrusion having the non-conductive inorganic particle as a core is formed on an outer surface of the metal layer,

the protrusions have, on a surface within a concentric circle of 1/2 diameters having the diameter of the conductive particle, 20 or more first protrusions having a diameter of 50nm or more and less than 100nm, 20 or more second protrusions having a diameter of 100nm or more and less than 200nm, and 5 or more and 20 or less third protrusions having a diameter of 200nm or more and 350nm or less.

43. The method for producing conductive particles according to claim 39 or 40, further comprising:

a first coating step of coating the resin particles with a cationic polymer; and

a second coating step of coating the non-conductive inorganic particles with a hydrophobizing agent,

in the step of forming the composite particles, the non-conductive inorganic particles are bonded to the surfaces of the resin particles by electrostatic force,

the difference in the interfacial potential between the resin particles and the non-conductive inorganic particles is greater than or equal to 30mV at a pH of greater than or equal to 1 and a pH of less than or equal to 11.

44. The method for producing conductive particles according to claim 39 or 40, wherein in the step of covering the composite particles with the metal layer, the composite particles are covered with a first layer containing nickel by electroless plating.

45. The method for manufacturing conductive particles according to claim 44, wherein in the step of covering the composite particles with the metal layer, the composite particles covered with the first layer are covered with a second layer containing a metal selected from the group consisting of noble metals and cobalt.