JPWO2012115076A1 - Conductive particle, method for producing conductive particle, anisotropic conductive material, and connection structure - Google Patents

Abstract

Provided are a conductive particle and a method for producing a conductive particle that maintain good conduction between electrodes even when exposed to harsh conditions and suppress unexpected malfunctions in a connection structure. The conductive particle 1 according to the present invention includes a base particle 2 and a conductive layer 3 provided on the surface of the base particle 2. The conductive layer 3 has a nickel layer 11 provided on the surface of the base particle 2. The content of alkali metal in the entire nickel layer 11 exceeds 0 μg / g. The content of alkali metal in the 30 nm thick region of the outer surface of the nickel layer 11 is 80 μg / g or less. In the method for producing conductive particles according to the present invention, the alkali metal ion concentration (mol / L) in the electroless plating solution at the end of the electroless plating reaction is the nickel ion concentration (mol / L) in the electroless plating solution. When it is 4 times or less of L), the electroless plating reaction is terminated and the conductive particles 1 are obtained.

Description

  The present invention relates to conductive particles that can be used, for example, for connection between electrodes, and more particularly to conductive particles having base particles and a conductive layer provided on the surface of the base particles. Moreover, this invention relates to the manufacturing method of the said electroconductive particle, the anisotropic conductive material using the said electroconductive particle, and a connection structure.

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

  The anisotropic conductive material is used for connection between an IC chip and a flexible printed circuit board, connection between an IC chip and a circuit board having an ITO electrode, and the like. For example, after disposing an anisotropic conductive material between the electrode of the IC chip and the electrode of the circuit board, these electrodes can be electrically connected by heating and pressing.

  As an example of the conductive particles used in the anisotropic conductive material, the following Patent Document 1 discloses a conductive material having resin fine particles and a metal coating layer formed by electroless plating on the surface of the resin fine particles. Particles are disclosed. Here, the pulverized product obtained by peeling and pulverizing the metal coating layer of 1 g of conductive particles is dispersed in 100 mL of distilled water, placed in a continuous extractor and boiled for 10 hours to obtain an extract, and then the extract is used. The amount of ions contained in the solution filtered through a 0.1 μm membrane filter is defined. Specifically, it is specified that the content of halogen ions per 1 g of conductive particles is 30 μg or less and the content of alkali metal ions is 50 μg or less.

JP 2004-14409 A

  Conductive particles used for connection between electrodes in electronic devices and the like are required to be resistant to thermal degradation even when used in harsh environments. That is, there is a demand for sufficiently ensuring conduction reliability between electrodes connected by conductive particles.

  In Patent Document 1, the content of halogen ions and alkali metal ions per gram of conductive particles is less than the above upper limit, so that even under severe conditions such as high temperature and high humidity and long-term continuous use, the metal It is described that the coating layer does not corrode and the conductivity is difficult to decrease, and that the counter electrode and the semiconductor element are less affected by corrosion and deterioration.

  When the connection structure is formed using the conductive particles described in Patent Document 1 for connection between the electrodes, when the connection structure is exposed to high temperature and high humidity, the conductivity between the electrodes is reduced. The decrease can be suppressed to some extent. On the other hand, development of conductive particles that can further suppress the elution of trace ions derived from conductive particles under high temperature and high humidity is required. For example, in connection structures using conductive particles, development of conductive particles capable of sufficiently suppressing unexpected malfunctions is required.

  Moreover, when manufacturing an anisotropic conductive material using the electroconductive particle of patent document 1, an electroconductive particle may have a bad influence on the sclerosis | hardenability of binder resin. That is, when an anisotropic conductive material is used for connection between electrodes and is thermoset under a predetermined condition, sufficient curability may not be obtained even by heating during thermocompression bonding, and desired curing characteristics may not be obtained. is there.

  An object of the present invention is to maintain good electrical connection between electrodes even when the connection structure is exposed to severe conditions such as high temperature and high humidity when the connection structure is formed by connecting the electrodes. At the same time, it is an object to provide conductive particles that suppress unexpected malfunctions in the connection structure, a method for producing the conductive particles, an anisotropic conductive material using the conductive particles, and a connection structure.

  Further, a limited object of the present invention is to inhibit the curing of the binder resin caused by the conductive particles even if the conductive particles and the binder resin are mixed and coexisted in order to constitute an anisotropic conductive material. It is an object of the present invention to provide conductive particles that are not easily generated, a method for producing the conductive particles, and an anisotropic conductive material and a connection structure using the conductive particles.

According to a wide aspect of the present invention, the substrate includes a base particle and a conductive layer, the conductive layer has a nickel layer provided on the surface of the base particle, and the entire nickel layer contains alkali metal. Conductive particles having an amount of more than 0 μg / g and an alkali metal content of 80 μg / g or less in the region of the outer surface of the nickel layer having a thickness of 30 nm are provided.

  In another specific aspect of the conductive particles according to the present invention, the nickel layer is a nickel layer formed by an electroless plating reaction using an electroless plating solution containing a nickel salt and an alkali metal-containing reducing agent. is there.

  In still another specific aspect of the conductive particle according to the present invention, the alkali metal contains sodium.

  In still another specific aspect of the conductive particles according to the present invention, the nickel layer is formed by an electroless plating reaction using an electroless plating solution containing a nickel salt and sodium hypophosphite. It is.

  In another specific aspect of the conductive particle according to the present invention, the conductive layer further includes a metal layer provided on the surface of the nickel layer.

  In another specific aspect of the conductive particle according to the present invention, the conductive particle has a protrusion on the outer surface of the conductive layer.

  In another specific aspect of the conductive particle according to the present invention, an insulating material disposed on the surface of the conductive layer is further provided.

  In still another specific aspect of the conductive particle according to the present invention, the insulating substance is an insulating particle.

  On the other specific situation of the electroconductive particle which concerns on this invention, content of the said alkali metal in the said whole nickel layer exceeds 0 microgram / g, and is 50 microgram / g or less.

  Further, according to a wide aspect of the present invention, a step of forming a nickel layer by an electroless plating reaction using an electroless plating solution containing a nickel salt and an alkali metal-containing reducing agent on the surface of the substrate particles. And when the alkali metal ion concentration (mol / L) in the electroless plating solution at the end of the electroless plating reaction is not more than 4 times the nickel ion concentration (mol / L) in the electroless plating solution. By terminating the electroless plating reaction, the content of alkali metal in the entire nickel layer exceeds 0 μg / g, and the content of alkali metal in the region of 30 nm thickness on the outer surface of the nickel layer is 80 μg / g. Provided is a method for producing conductive particles, which provides the following conductive particles.

  On the specific situation with the manufacturing method of the electroconductive particle which concerns on this invention, the said alkali metal contains sodium.

  In another specific aspect of the method for producing conductive particles according to the present invention, an electroless plating solution containing a nickel salt and sodium hypophosphite is used as the electroless plating solution.

  In another specific aspect of the method for producing conductive particles according to the present invention, conductive particles in which the content of the alkali metal in the entire nickel layer exceeds 0 μg / g and is 50 μg / g or less are obtained.

  The anisotropic conductive material which concerns on this invention contains the electroconductive particle comprised according to this invention, and binder resin.

  A connection structure according to the present invention includes a first connection target member, a second connection target member, and a connection part that electrically connects the first and second connection target members, The connecting portion is formed of conductive particles configured according to the present invention, or is formed of an anisotropic conductive material including the conductive particles and a binder resin.

  The conductive particles according to the present invention include base particles and a conductive layer, the conductive layer has a nickel layer provided on the surface of the base particles, and the content of alkali metal in the entire nickel layer Is more than 0 μg / g, and the content of alkali metal in the region of 30 nm thickness of the outer surface of the nickel layer is 80 μg / g or less. Therefore, a connection structure using conductive particles for connection between electrodes is provided. When exposed to harsh conditions such as high temperature and high humidity, eluted ions derived from conductive particles can be suppressed. Therefore, the operation reliability of the connection structure can be improved.

  In the method for producing conductive particles according to the present invention, the alkali metal ion concentration (mol / L) in the electroless plating solution at the end of the electroless plating reaction is the nickel ion concentration (mol / L) in the electroless plating solution. L) When the electroless plating reaction is terminated at 4 times or less, the alkali metal content in the entire nickel layer exceeds 0 μg / g, and the outer surface of the nickel layer has a thickness of 30 nm. Conductive particles with an alkali metal content of 80 μg / g or less are obtained, so that when the connection structure is exposed to harsh conditions such as high temperature and high humidity, the ions eluted from the conductive particles are suppressed. It is possible to obtain conductive particles that can improve the operational reliability of the connection structure.

FIG. 1 is a cross-sectional view showing conductive particles according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing conductive particles according to another embodiment of the present invention. FIG. 3 is a front sectional view schematically showing a connection structure using conductive particles according to an embodiment of the present invention.

  Hereinafter, the present invention will be clarified by describing specific embodiments and examples of the present invention with reference to the drawings.

  FIG. 1 is a cross-sectional view showing conductive particles according to an embodiment of the present invention.

  A conductive particle 1 shown in FIG. 1 includes a base particle 2 and a conductive layer 3. The conductive layer 3 is provided on the surface of the base particle 2.

  In addition, the conductive layer 3 includes a nickel layer 11 provided on the surface of the base particle 2 and a metal layer 12 provided on the surface of the nickel layer 11. The conductive particles 1 may further include an insulating material disposed on the surface of the conductive layer 3. The metal layer 12 may not be provided. However, the metal layer 12 is preferably provided from the viewpoint of low resistance and the viewpoint of further suppressing the decrease in conductivity under severe conditions. That is, the conductive particles according to the present invention preferably have a metal layer provided on the surface of the nickel layer. The metal layer is a layer different from the nickel layer. Furthermore, as the metal layer 12, a palladium layer may be formed, or a metal layer other than the palladium layer may be formed. The insulating substance is preferably an insulating resin layer or insulating particles.

  FIG. 2 is a cross-sectional view showing conductive particles according to another embodiment of the present invention.

  As shown in FIG. 2, the conductive particle 21 includes a base particle 2 and a conductive layer 22. The conductive layer 22 is provided on the surface of the base particle 2. The conductive layer 22 has a nickel layer 31 provided on the surface of the base particle 2 and a metal layer 32 provided on the surface of the nickel layer 31. The conductive particle 21 includes a plurality of core substances 23 on the surface of the base particle 2. The nickel layer 31 and the conductive layer 22 cover the core material 23. By covering the core material 23 with the conductive layer 22, the conductive particles 21 have a plurality of protrusions 24 on the surface.

  The conductive particles 21 include a plurality of insulating substances 25 arranged on the surface of the conductive layer 22, that is, on the surface of the metal layer 32. The insulating substance 25 is an insulating particle. The insulating particles are preferably insulating resin particles. Instead of the insulating particles, an insulating resin layer may be arranged on the surface of the conductive layer 22. Thus, the conductive particles may include an insulating material disposed on the surface of the conductive layer. The conductive particles may include an insulating material attached on the surface of the conductive layer. The surface of the conductive layer may be covered with an insulating resin layer.

  The main feature of the conductive particles according to the present invention is that the alkali metal content A in the entire nickel layer exceeds 0 μg / g, and the alkali metal content B in the region of the nickel layer outer surface thickness of 30 nm is 80 μg / g or less. The content B is 0 μg / g or more, and may be 0 μg / g. When the content B of the alkali metal in the vicinity of the outer surface of the nickel layer is 80 μg / g or less, the conductive structure is used when the connection structure using the conductive particles for connection between the electrodes is exposed to severe conditions. Elution ions derived from particles can be suppressed. In particular, when the connection structure is exposed to high temperature and high humidity, the eluted ions derived from the conductive particles can be suppressed. Moreover, in order to constitute an anisotropic conductive material by setting the alkali metal content B in the vicinity of the outer surface of the nickel layer to 80 μg / g or less, the conductive particles and the binder resin are mixed and coexisted. However, it is difficult for the binder resin to be hardened due to the conductive particles. When the anisotropic conductive material is used for connection between the electrodes and thermally cured under predetermined conditions, sufficient curability can be obtained by heating during thermocompression bonding, and desired curing characteristics can be obtained.

  On the other hand, if the content of the alkali metal in the vicinity of the outer surface of the nickel layer is large, the alkali metal migrates to the electrode part or IC that comes into contact with the conductive particles, and the malfunction tends to occur. There exists a tendency for the conduction | electrical_connection reliability of a connection structure to be impaired. Even if a metal layer such as a palladium layer is provided on the surface of the nickel layer, if the content of alkali metal in the vicinity of the outer surface of the nickel layer is large, it becomes difficult to suppress the eluted ions, and malfunctions such as IC Tends to occur. The content B is preferably 60 μg / g or less, more preferably 50 μg / g or less. The content B indicates the content of an alkali metal contained in a region having a thickness of 30 nm on the outer surface of the nickel layer with respect to the weight of the entire region having a thickness of 30 nm on the outer surface of the nickel layer. In addition, the region having a thickness of 30 nm on the outer surface of the nickel layer is, in other words, a region extending from the outer surface of the nickel layer to a distance of 30 nm inward in the thickness direction.

  As a result of intensive studies by the present inventors, it has been discovered that an unexpected malfunction in the connection structure and a decrease in the curability of the binder resin are affected by a small amount of alkali metal ions resulting from the conductive particles. Among them, alkali metal ions existing in the vicinity of the outer surface of the conductive particles are particularly influential, and the above problem is solved by appropriately controlling the amount of alkali metal ions in the vicinity of the outer surface, thereby completing the present invention. It came to.

  In the electroconductive particle which concerns on this invention, it is preferable that it is that content A of the alkali metal in the whole nickel layer exceeds 0 microgram / g and is 50 microgram / g or less. Thus, by reducing the content of sodium in the entire nickel layer, when the connection structure using conductive particles for connection between electrodes is exposed to harsh conditions, the eluted ions derived from the conductive particles Can be further suppressed. In particular, when the connection structure is exposed to high temperature and high humidity, the eluted ions derived from the conductive particles can be further suppressed. Furthermore, by reducing the content of sodium in the entire nickel layer, even if the conductive particles and the binder resin are blended and coexisted, it is difficult for the binder resin to be inhibited from curing due to the conductive particles.

  Examples of the alkali metal include lithium, sodium, potassium, rubidium, and cesium. In particular, sodium ions and potassium ions are likely to be mixed and cause problems. Since the effect of the present invention can be obtained more remarkably, the alkali metal preferably contains sodium or potassium, and more preferably contains sodium.

  From the viewpoint of forming a homogeneous nickel layer, the nickel layer is preferably a nickel layer formed by an electroless plating reaction using an electroless plating solution containing a nickel salt and an alkali metal-containing reducing agent. . From the viewpoint of forming a more uniform nickel layer, the nickel layer is formed by an electroless plating reaction using an electroless plating solution containing a nickel salt and sodium hypophosphite (reducing agent). A layer is preferred.

  Examples of the substrate particles include resin particles, inorganic particles, organic-inorganic hybrid particles, and metal particles.

  The substrate particles are preferably resin particles formed of a resin. When connecting the electrodes, the conductive particles are generally compressed after the conductive particles are arranged between the electrodes. When the substrate particles are resin particles, the conductive particles are easily deformed by compression, and the contact area between the conductive particles and the electrode is increased. For this reason, the conduction | electrical_connection reliability between electrodes can be improved.

  Various organic materials are suitably used as the resin for forming the resin particles. Examples of the resin for forming the resin particles include polyolefins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polypropylene, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; Polymerize one or more of alkylene terephthalate, polysulfone, polycarbonate, polyamide, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, and various polymerizable monomers having ethylenically unsaturated groups. The polymer obtained by the above is used. By polymerizing one or more of various polymerizable monomers having an ethylenically unsaturated group, it is possible to design and synthesize resin particles having any compression property suitable for a conductive material.

  When the resin particles are obtained by polymerizing a monomer having an ethylenically unsaturated group, the monomer having an ethylenically unsaturated group includes a non-crosslinkable monomer and a crosslinkable monomer. And so on.

  Examples of the non-crosslinkable monomer include styrene monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth) acrylic acid, maleic acid, and maleic anhydride; (Meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl ( Alkyl (meth) acrylates such as meth) acrylate and isobornyl (meth) acrylate; oxygen such as 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, polyoxyethylene (meth) acrylate and glycidyl (meth) acrylate (Meth) acrylates; nitrile-containing monomers such as (meth) acrylonitrile; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether; vinyl acids such as vinyl acetate, vinyl butyrate, vinyl laurate, vinyl stearate Esters; Unsaturated hydrocarbons such as ethylene, propylene, isoprene and butadiene; Halogen-containing monomers such as trifluoromethyl (meth) acrylate, pentafluoroethyl (meth) acrylate, vinyl chloride, vinyl fluoride and chlorostyrene Is mentioned.

  Examples of the crosslinkable monomer include tetramethylolmethane tetra (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and dipenta Erythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, glycerol tri (meth) acrylate, glycerol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) Polyfunctional (meth) acrylates such as acrylate, (poly) tetramethylene di (meth) acrylate, 1,4-butanediol di (meth) acrylate; triallyl (iso) cyanurate, tria Rutorimeriteto, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, .gamma. (meth) acryloxy propyl trimethoxy silane, trimethoxy silyl styrene, include silane-containing monomers such as vinyltrimethoxysilane.

  The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group by a known method. Examples of this method include a method of suspension polymerization in the presence of a radical polymerization initiator and a method of polymerizing a non-crosslinked seed particle by swelling a monomer together with a radical polymerization initiator.

  When the substrate particles are inorganic particles or organic-inorganic hybrid particles, examples of the inorganic material for forming the substrate particles include silica and carbon black. Although it does not specifically limit as the particle | grains formed with the said silica, For example, after hydrolyzing the silicon compound which has two or more hydrolysable alkoxysil groups, and forming a crosslinked polymer particle, it calcinates as needed. The particle | grains obtained by performing are mentioned.

  When the substrate particles are metal particles, examples of the metal for forming the metal particles include silver, copper, nickel, silicon, gold, and titanium. However, the substrate particles are preferably not metal particles.

  The average particle diameter of the substrate particles is preferably 1 μm or more, more preferably 2 μm or more, preferably 100 μm or less, more preferably 50 μm or less, still more preferably 30 μm or less, and particularly preferably 5 μm or less. When the average particle diameter of the substrate particles is equal to or more than the above lower limit, the conduction reliability between the electrodes is further enhanced. The space | interval between electrodes can be narrowed as the average particle diameter of a base particle is below the said upper limit.

  The average particle diameter indicates a number average particle diameter. The average particle size can be measured using, for example, a Coulter counter (manufactured by Beckman Coulter).

  The average thickness of the nickel layer is 30 nm or more, preferably more than 30 μm, more preferably 45 nm or more, still more preferably 60 nm or more, preferably 1000 nm or less, more preferably 800 nm or less. When the average thickness of the nickel layer is not less than the above lower limit, the conductivity of the conductive particles is further increased. When the average thickness of the nickel layer is not more than the above upper limit, the stress at the interface due to the difference in thermal expansion coefficient between the base particle and the nickel layer is relaxed, and the nickel layer becomes difficult to peel from the base particle.

  As a method for forming a nickel layer on the surface of the substrate particles, a method for forming a nickel layer by electroless plating is suitable.

  When the metal layer (such as the palladium layer) is formed on the surface of the nickel layer, the average thickness of the metal layer is preferably 5 nm or more, more preferably 10 nm or more, preferably 500 nm or less, more preferably 400 nm. It is as follows. When the average thickness of the metal layer is not less than the above lower limit, the conductivity of the conductive particles is further increased. Furthermore, when the average thickness of the metal layer is not less than the above lower limit, the surface of the nickel layer can be relatively uniformly covered with the metal layer. For this reason, electroconductive particle becomes high tolerance with respect to an external environment, and a nickel layer becomes difficult to deteriorate. Therefore, the conductivity of the entire conductive layer in the conductive particles can be further increased. When the average thickness of the metal layer is not more than the above upper limit, the cost of the conductive particles is reduced.

  As a method for forming the metal layer (the palladium layer or the like) on the surface of the nickel layer, an electroless plating solution containing a metal-containing compound such as a palladium salt and a reducing agent is used, and the metal layer is electrolessly plated. And a method of forming a metal layer by electroplating.

  When a metal layer other than the palladium layer is provided on the surface of the nickel layer, examples of the metal for constituting the metal layer include gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, Examples include cobalt, indium, chromium, titanium, antimony, germanium, cadmium, bismuth, thallium, a tin-lead alloy, a tin-copper alloy, a tin-silver alloy, and a tin-lead-silver alloy. In addition, tin-doped indium oxide (ITO) may be used as the metal. As for the said metal, only 1 type may be used, 2 or more types may be used together, and an alloy may be sufficient as it.

  Like the electroconductive particle 21, it is preferable that the electroconductive particle which concerns on this invention has a processus | protrusion on the surface. The conductive particles preferably have protrusions on the outer surface of the conductive layer, preferably have protrusions on the outer surface of the nickel layer, preferably have protrusions on the outer surface of the metal layer, and the outer surface of the palladium layer. It is preferable to have a protrusion on the surface. It is preferable that there are a plurality of protrusions. An oxide film is often formed on the surface of the electrode connected by the conductive particles. When conductive particles having protrusions are used, the oxide film is effectively eliminated by the protrusions by placing the conductive particles between the electrodes and pressing them. For this reason, an electrode and the conductive layer of electroconductive particle can be contacted still more reliably, and the connection resistance between electrodes can be made low. Further, when the conductive particles have an insulating material on the surface, or when the conductive particles are dispersed in a binder resin and used as an anisotropic conductive material, the conductive particles and the conductive particles The resin between the electrodes can be effectively eliminated. For this reason, the conduction | electrical_connection reliability between electrodes can be improved.

  As a method of forming protrusions on the surface of the conductive particles, a method of forming a conductive layer by electroless plating after attaching a core substance to the surface of the base particles, and electroless plating on the surface of the base particles Examples include a method of forming a conductive layer by, attaching a core substance, and further forming a conductive layer by electroless plating.

  As a method for attaching the core substance to the surface of the base particle, for example, a conductive substance that becomes the core substance is added to the dispersion of the base particle, and the core substance is added to the surface of the base particle, for example, A method of accumulating and adhering by van der Waals force, and adding a conductive substance as a core substance to the container containing the base particle, and then the core on the surface of the base particle by mechanical action such as rotation of the container Examples include a method of attaching a substance. Especially, since the quantity of the core substance to adhere is easy to control, the method of making a core substance accumulate and adhere on the surface of the base particle in a dispersion liquid is preferable.

  Examples of the conductive material constituting the core material include conductive non-metals such as metals, metal oxides, and graphite, and conductive polymers. Examples of the conductive polymer include polyacetylene. Among them, metal is preferable because conductivity can be increased.

  Examples of the metal include gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, and tin-lead. Examples include alloys composed of two or more metals such as alloys, tin-copper alloys, tin-silver alloys, and tin-lead-silver alloys. Of these, nickel, copper, silver or gold is preferable. The metal constituting the core material may be the same as or different from the metal constituting the conductive layer. Examples of the metal oxide include alumina, silica and zirconia.

  Further, as a method of forming the protrusion, the core substance is applied to the surface of the nickel plating metal layer after the nickel plating process or to the surface of the metal plating layer such as palladium on the nickel layer by physical or mechanical impact. You may use the method of making it adhere. In this case, a physical or mechanical hybridization method may be used. In the physical or mechanical hybridization method, a hybridizer or the like is used.

  Like the electroconductive particle 21, it is preferable that the electroconductive particle which concerns on this invention is equipped with the insulating substance arrange | positioned on the surface of the said electroconductive layer (metal layers, such as the said nickel layer or a palladium layer). In this case, when the conductive particles are used for connection between the electrodes, a short circuit between adjacent electrodes can be prevented. Specifically, when a plurality of conductive particles are in contact with each other, an insulating material is present between the plurality of electrodes, so that it is possible to prevent a short circuit between electrodes adjacent in the lateral direction instead of between the upper and lower electrodes. In addition, the insulating substance between the conductive layer of an electroconductive particle and an electrode can be easily excluded by pressurizing electroconductive particle with two electrodes in the case of the connection between electrodes. When the conductive particles have protrusions on the surface of the conductive layer, the insulating substance between the conductive layer of the conductive particles and the electrode can be more easily eliminated. The insulating substance is preferably an insulating resin layer or insulating particles. The insulating particles are preferably insulating resin particles.

  Specific examples of the insulating material include polyolefins, (meth) acrylate polymers, (meth) acrylate copolymers, block polymers, thermoplastic resins, crosslinked thermoplastic resins, thermosetting resins, and water-soluble resins. Etc.

  Examples of the polyolefins include polyethylene, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid ester copolymer. Examples of the (meth) acrylate polymer include polymethyl (meth) acrylate, polyethyl (meth) acrylate, and polybutyl (meth) acrylate. Examples of the block polymer include polystyrene, styrene-acrylic acid ester copolymer, SB type styrene-butadiene block copolymer, SBS type styrene-butadiene block copolymer, and hydrogenated products thereof. Examples of the thermoplastic resin include vinyl polymers and vinyl copolymers. As said thermosetting resin, an epoxy resin, a phenol resin, a melamine resin, etc. are mentioned. Examples of the water-soluble resin include polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyvinyl pyrrolidone, polyethylene oxide, and methyl cellulose.

  The conductive particles according to the present invention more preferably include insulating particles attached to the surface of the conductive layer. In this case, when the conductive particles are used for the connection between the electrodes, not only can the short circuit between the laterally adjacent electrodes be further prevented, but also the connection resistance between the connected upper and lower electrodes can be further reduced. Can do.

  Examples of a method for attaching insulating particles to the surface of the conductive layer include a chemical method and a physical or mechanical method. As the chemical method, for example, as disclosed in WO2003 / 25955A1, insulating particles are attached on the conductive layer of the metal surface particles by a heteroaggregation method using van der Waals force or electrostatic force, and further required. Depending on the case, a chemical bonding method may be mentioned. Examples of the physical or mechanical method include spray drying, hybridization, electrostatic adhesion, spraying, dipping, and vacuum deposition. In particular, a method of attaching an insulating substance to the surface of the conductive layer through a chemical bond is preferable because the insulating substance is difficult to be detached.

  The particle diameter of the insulating particles is preferably 1/5 or less of the particle diameter of the conductive particles. In this case, the particle diameter of the insulating particles does not become too large, and the electrical connection by the conductive layer is more reliably achieved. When the particle diameter of the insulating particles is 1/5 or less of the particle diameter of the conductive particles, the insulating particles are efficiently adsorbed on the surface of the conductive layer when the insulating particles are adhered by the hetero-aggregation method. Can do. The particle diameter of the insulating particles is preferably 5 nm or more, more preferably 10 nm or more, preferably 1000 nm or less, more preferably 500 nm or less. When the particle diameter of the insulating particles is equal to or larger than the lower limit, the distance between adjacent conductive particles becomes larger than the electron hopping distance, and leakage hardly occurs. When the particle diameter of the insulating particles is not more than the above upper limit, the pressure and the amount of heat required for thermocompression bonding are reduced.

  The CV value of the particle diameter of the insulating particles is preferably 20% or less. When the CV value is 20% or less, the thickness of the coating layer of the conductive particles becomes uniform, it becomes easy to apply pressure uniformly when thermocompression bonding between the electrodes, and poor conduction is less likely to occur. The CV value of the particle diameter is calculated by the following formula.

  CV value of particle diameter (%) = standard deviation of particle diameter / average particle diameter × 100

  The particle size distribution can be measured with a particle size distribution meter or the like before coating the metal surface particles, and can be measured by image analysis of an SEM photograph after coating.

  In order to expose the conductive layer of conductive particles, the coverage of the insulating material is preferably 5% or more, and preferably 70% or less. The coverage with the insulating material is the area of the portion covered with the insulating material in the entire surface area of the metal surface particles. When the coverage is 5% or more, adjacent conductive particles are more reliably insulated by an insulating substance. When the coverage is 70% or less, it is not necessary to apply heat and pressure more than necessary when connecting the electrodes, and the performance of the binder resin can be suppressed from being reduced by the excluded insulating substance.

  Although it does not specifically limit as said insulating particle, Well-known inorganic particle | grains and organic polymer particle | grains are applicable. Examples of the inorganic particles include insulating inorganic particles such as alumina, silica, and zirconia.

  The organic polymer particles are preferably resin particles obtained by (co) polymerizing one or more monomers having an unsaturated double bond. Examples of the monomer having an unsaturated double bond include (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth). Acrylate, glycidyl (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, trimethylolpropane tri (meth) acrylate, glycerol tri (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (Meth) acrylates such as (meth) acrylate and 1,4-butanediol di (meth) acrylate; vinyl ethers; vinyl chloride; styrene compounds such as styrene and divinyl benzene, acrylonitrile, and the like. That. Of these, (meth) acrylic acid esters are preferably used.

  The insulating particles preferably have a polar functional group in order to adhere to the conductive layer of the conductive particles by heteroaggregation. Examples of the polar functional group include an ammonium group, a sulfonium group, a phosphate group, and a hydroxysilyl group. The polar functional group can be introduced by copolymerizing a monomer having the polar functional group and an unsaturated double bond.

  Examples of the monomer having an ammonium group include N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropylacrylamide, and N, N, N-trimethyl-N-2-methacryloyloxyethylammonium chloride. It is done. Examples of the monomer having a sulfonium group include phenyldimethylsulfonium methylsulfate methacrylate. Examples of the monomer having a phosphoric acid group include acid phosphooxyethyl methacrylate, acid phosphooxypropyl methacrylate, acid phosphooxypolyoxyethylene glycol monomethacrylate, and acid phosphooxypolyoxypropylene glycol monomethacrylate. Examples of the monomer having a hydroxysilyl group include vinyltrihydroxysilane and 3-methacryloxypropyltrihydroxysilane.

  As another method for introducing a polar functional group onto the surface of the insulating particles, a method using a radical initiator having a polar group as an initiator when the monomer having an unsaturated double bond is polymerized may be mentioned. It is done. Examples of the radical initiator include 2,2′-azobis {2-methyl-N- [2- (1-hydroxy-butyl)]-propionamide}, 2,2′-azobis [2- (2- Imidazolin-2-yl) propane], 2,2′-azobis (2-amidinopropane) and salts thereof.

(Method for producing conductive particles)
The method for producing conductive particles according to the present invention includes a step of forming a nickel layer on the surface of a base particle by an electroless plating reaction using an electroless plating solution containing a nickel salt and an alkali metal-containing reducing agent. (Electroless plating step).

  In the method for producing conductive particles according to the present invention, the alkali metal ion concentration (mol / L) in the electroless plating solution at the end of the electroless plating reaction is the same as that in the electroless plating solution at the end of the electroless plating reaction. When the nickel ion concentration (mol / L) is 4 times or less, the electroless plating reaction is terminated. As a result, conductive particles in which the content of the alkali metal in the entire nickel layer exceeds 0 μg / g and the content B of the alkali metal in the region of 30 nm thickness on the outer surface of the nickel layer is 80 μg / g or less are obtained. . In the method for producing conductive particles according to the present invention, the content A of the alkali metal exceeds 0 μg / g. By reducing the content of alkali metal in the entire nickel layer, when the connection structure using conductive particles for connection between electrodes is exposed to harsh conditions such as high temperature and high humidity, it is derived from conductive particles Elution ions can be suppressed and high reliability can be maintained. The alkali metal ion concentration includes alkali metal ions in the electroless plating solution. The nickel ion concentration includes nickel ions in the electroless plating solution.

  In the manufacturing method of the electroconductive particle which concerns on this invention, Preferably, the electroconductive particle whose content A of the said alkali metal in the whole nickel layer exceeds 0 microgram / g and is 50 microgram / g or less is obtained.

  When the present inventors form a nickel layer using the electroless plating solution, the nickel ion concentration in the electroless plating solution decreases as the thickness of the nickel layer increases. It was noted that the alkali metal ion concentration in the electroless plating solution was increased. As a result, in the nickel layer, the alkali metal ion concentration tends to increase from the inner surface to the outer surface, and the alkali metal content in the vicinity of the outer surface of the nickel layer is particularly high. In the method for producing conductive particles according to the present invention, the electroless plating reaction is terminated before the alkali metal ion concentration (mol / L) in the electroless plating solution at the end of the electroless plating reaction becomes too high. . That is, the inventors have determined that the alkali metal ion concentration (mol / L) in the electroless plating solution at the end of the electroless plating reaction is the nickel ion concentration in the electroless plating solution at the end of the electroless plating reaction. It has been found that the content of alkali metal in the vicinity of the outer surface of nickel can be controlled so as not to increase by terminating the electroless plating reaction when it is 4 times or less (mol / L). As a result, the alkali metal content B in the 30 nm thick region of the outer surface of the nickel layer is reduced. As a result of the content B being reduced, the content A of the alkali metal in the entire nickel layer is also reduced.

  Generally, when performing the electroless plating reaction, the electroless plating reaction is allowed to proceed until the nickel in the plating solution is sufficiently consumed. This is to make effective use of nickel. However, when the electroless plating reaction proceeds to the general nickel consumption in this way, the amount of alkali metal contained in the nickel layer increases. In the method for producing conductive particles according to the present invention, even if nickel is not sufficiently consumed, the plating reaction is actively terminated, and the content B of alkali metal near the outer surface of nickel is reduced. Preferably, the alkali metal content A in the entire nickel layer is also reduced.

  In the method of forming a nickel layer by electroless plating, generally, an etching process and a catalyzing process are performed prior to the electroless plating process. Hereinafter, an example of a method for forming a nickel layer on the surface of the resin particles by electroless plating will be described in more detail.

  In the etching step, an oxidizing agent such as chromic acid, a sulfuric acid-chromic acid mixed solution or a permanganic acid solution, a strong acid such as hydrochloric acid or sulfuric acid, a strong alkaline solution such as sodium hydroxide or potassium hydroxide, and various other commercially available etching agents. Etc. are used to form minute irregularities on the surface of the resin particles. This enhances the adhesion of the nickel layer. When using a liquid agent containing a halogen ion, it is preferable to perform sufficient washing so that no halogen remains.

  In the catalyzing step, a catalyst layer serving as a starting point for forming a plating layer by electroless plating is formed on the surface of the resin particles.

  As a method of forming the catalyst layer on the surface of the resin particle, for example, after adding the resin particle to a solution containing palladium chloride and tin chloride, the surface of the resin particle is activated with an acid solution or an alkali solution, A method for depositing palladium on the surface of the particles, and after adding the resin particles to a solution containing palladium sulfate and aminopyridine, the surface of the resin particles is activated by a solution containing a reducing agent. For example, a method of depositing palladium. As the reducing agent, sodium hypophosphite, potassium hypophosphite, dimethylamine borane or the like is used.

  In the electroless plating step, a nickel plating bath (electroless plating solution) containing a nickel salt and an alkali metal-containing reducing agent is used. By immersing the resin particles in the nickel plating bath, nickel can be deposited on the surface of the resin particles on which the catalyst is formed. From the viewpoint of forming a homogeneous nickel layer, a phosphorus-based reducing agent is preferably used as the alkali metal-containing reducing agent. For example, sodium hypophosphite or potassium hypophosphite is preferably used. The alkali metal-containing reducing agent is preferably a sodium-containing reducing agent or a potassium-containing reducing agent, and is preferably a sodium-containing reducing agent.

  The method for producing conductive particles according to the present invention preferably further includes a step of forming a metal layer (electroless plating step) using an electroless plating solution containing a metal on the surface of the nickel layer. More preferably, the method for producing conductive particles according to the present invention further includes a step of forming a palladium layer on the surface of the nickel layer using an electroless plating solution containing palladium.

(Anisotropic conductive material)
The anisotropic conductive material according to the present invention includes the above-described conductive particles and a binder resin. The binder resin is not particularly limited. As the binder resin, a known insulating resin is used.

  Moreover, when the said binder resin has a reactive functional group, a polymerization catalyst and a curing catalyst are mix | blended. For example, a polymerization initiator or a curing agent is blended with the binder resin. The binder resin is preferably a curable resin. The anisotropic conductive material preferably contains a polymerization initiator or a curing agent. The curable resin is preferably an epoxy resin. The anisotropic conductive material preferably includes a curing agent, and more preferably includes an anionic curing agent.

  Among anisotropic conductive materials, an anisotropic conductive film often uses a curing system including an epoxy resin and an anionic curing agent. Conventional conductive particles that do not control the alkali metal content B in the vicinity of the outer surface tend to cause problems such as curing delay and poor curing in such a curing system. Although the detailed mechanism is unknown, it is considered that the anion component generated in the curing process of these curing systems interacts with alkali metal ions derived from the conductive particles to inhibit the curing reaction. . Even in a curing system other than an anionic system, unexpected curing failure or curing abnormality such as gelation may occur.

  In the conventional conductive particles, since the content B of the alkali metal existing in the vicinity of the outer surface of the nickel layer is not controlled, these metal layers are formed even when a metal layer such as a palladium layer is formed on the outer surface. It is considered that the alkali metal ions are eluted from the pinholes and crevices of the metal, or the portions where the underlying nickel layer is exposed due to non-uniform plating, and the above-described hardening inhibition occurs.

  In addition to the conductive particles and the binder resin, the anisotropic conductive material includes, for example, a filler, an extender, a softener, a plasticizer, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, and a heat stabilizer. Further, various additives such as a light stabilizer, an ultraviolet absorber, a lubricant, an antistatic agent and a flame retardant may be contained.

  The method for dispersing the conductive particles in the binder resin is not particularly limited, and a conventionally known dispersion method can be used. Examples of a method for dispersing the conductive particles in the binder resin include a method in which the conductive particles are added to the binder resin and then kneaded and dispersed with a planetary mixer or the like. The conductive particles are dispersed in water. Alternatively, after uniformly dispersing in an organic solvent using a homogenizer or the like, it is added to the binder resin and kneaded with a planetary mixer or the like, and the binder resin is diluted with water or an organic solvent. Then, the method of adding the said electroconductive particle, kneading with a planetary mixer etc. and disperse | distributing is mentioned.

  The anisotropic conductive material according to the present invention can be used as an anisotropic conductive paste and an anisotropic conductive film. When the anisotropic conductive material according to the present invention is an anisotropic conductive film, a film-like adhesive not containing conductive particles is laminated on the anisotropic conductive film containing conductive particles. Also good. The anisotropic conductive paste and the anisotropic conductive film include anisotropic conductive ink, anisotropic conductive adhesive and anisotropic conductive sheet.

  In 100% by weight of the anisotropic conductive material, the content of the binder resin is preferably 10% by weight or more, more preferably 30% by weight or more, still more preferably 50% by weight or more, particularly preferably 70% by weight or more, preferably It is 99.99 weight% or less, More preferably, it is 99.9 weight% or less. When the content of the binder resin is not less than the above lower limit and not more than the above upper limit, the conductive particles can be efficiently disposed between the electrodes, and the conduction reliability between the electrodes can be further enhanced.

  In 100% by weight of the anisotropic conductive material, the content of the conductive particles is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, preferably 20% by weight or less, more preferably 10% by weight. % Or less. When the content of the conductive particles is not less than the above lower limit and not more than the above upper limit, the conduction reliability between the electrodes is further enhanced.

(Connection structure)
A connection structure can be obtained by connecting the connection target members using the conductive particles according to the present invention or using an anisotropic conductive material containing the conductive particles and a binder resin.

  The connection structure includes a first connection target member, a second connection target member, and a connection part connecting the first and second connection target members, the connection part of the present invention. A connection structure formed of conductive particles or an anisotropic conductive material containing the conductive particles and a binder resin is preferable. In the case where conductive particles are used, the connection portion itself is conductive particles. That is, the first and second connection target members are connected by the conductive particles.

  In FIG. 3, the connection structure using the electroconductive particle which concerns on one Embodiment of this invention is typically shown with front sectional drawing.

  A connection structure 51 shown in FIG. 3 includes a first connection target member 52, a second connection target member 53, and a connection portion 54 connecting the first and second connection target members 52 and 53. Prepare. The connection portion 54 is formed by curing an anisotropic conductive material including the conductive particles 1. In FIG. 3, the conductive particles 1 are schematically shown for convenience of illustration. Instead of the conductive particles 1, conductive particles 21 may be used.

  A plurality of electrodes 52 b are provided on the upper surface 52 a (front surface) of the first connection target member 52. A plurality of electrodes 53 b are provided on the lower surface 53 a (front surface) of the second connection target member 53. The electrode 52 b and the electrode 53 b are electrically connected by one or a plurality of conductive particles 1. Therefore, the first and second connection target members 52 and 53 are electrically connected by the conductive particles 1.

The manufacturing method of the connection structure is not particularly limited. As an example of the manufacturing method of the connection structure, the anisotropic conductive material is disposed between the first connection target member and the second connection target member to obtain a laminate, and then the laminate is heated. And a method of applying pressure. The pressure of the said pressurization is about 9.8 * 10 < ⁴ > -4.9 * 10 < ⁶ > Pa. The temperature of the said heating is about 120-220 degreeC.

  Specific examples of the connection target member include electronic components such as semiconductor chips, capacitors, and diodes, and circuit boards such as printed boards, flexible printed boards, and glass boards.

  Examples of the electrode provided on the connection target member include metal electrodes such as a gold electrode, a nickel electrode, a tin electrode, an aluminum electrode, a copper electrode, a molybdenum electrode, and a tungsten electrode. When the connection object member is a flexible printed board, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, or a copper electrode. When the connection target member is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, or a tungsten electrode. In addition, when the said electrode is an aluminum electrode, the electrode formed only with aluminum may be sufficient and the electrode by which the aluminum layer was laminated | stacked on the surface of the metal oxide layer may be sufficient. Examples of the material for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal element include Sn, Al, and Ga.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited only to the following examples.

Example 1
(1) Electroless nickel plating step Divinylbenzene resin particles having an average particle diameter of 4 μm were treated with a 10 wt% solution of an ion adsorbent for 5 minutes, and then treated with a 0.01 wt% palladium sulfate aqueous solution for 5 minutes. Thereafter, dimethylamine borane was added for reduction treatment, filtration, and washing to obtain resin particles to which palladium was attached.

  Next, a 1% by weight sodium succinate solution in which sodium succinate was dissolved in 500 mL of ion exchange water was prepared. To this solution, 10 g of resin particles with palladium attached were added and mixed to prepare a slurry.

  An electroless plating solution containing 34% by weight of nickel sulfate hexahydrate, 24% by weight of sodium hypophosphite monohydrate, 15% by weight of ammonia and 5% by weight of succinic acid (the concentration of sodium mol in the electroless plating solution is The nickel mol concentration was 2 times or less). After the slurry adjusted to pH 6.5 was heated to 80 ° C., the electroless plating solution was continuously dropped into the slurry and stirred to advance the plating reaction. The plating reaction was completed when the sodium ion concentration in the electroless plating solution was 2.5 times the nickel ion concentration. In this way, a nickel layer was formed on the surface of the resin particles to obtain nickel plated particles. The nickel layer had a thickness of 0.1 μm.

(2) Electroless palladium plating step 10 g of the obtained nickel-plated particles were dispersed in 500 mL of ion-exchanged water using an ultrasonic treatment machine to obtain a particle suspension. While stirring the suspension at 50 ° C., 0.02 mol / L of palladium sulfate, 0.04 mol / L of ethylenediamine as a complexing agent, 0.06 mol / L of sodium formate as a reducing agent, and pH 10.0 containing a crystal modifier. The electroless plating solution was gradually added to perform electroless palladium plating. When the thickness of the palladium layer reached 0.03 μm, the electroless palladium plating was finished. Next, by washing and vacuum drying, conductive particles having a palladium layer formed on the surface of the nickel layer were obtained.

(Example 2)
In the electroless nickel plating step, when the sodium ion concentration in the electroless plating solution at the end of the electroless plating reaction is 3.3 times the nickel ion concentration, Example 1 except that the plating reaction is ended. Similarly, nickel plating particles were obtained.

  Conductive particles in which electroless palladium plating was performed on the surface of the obtained nickel plating particles in the same manner as in Example 1 to form a palladium layer (thickness 0.03 μm) on the surface of the nickel layer (thickness 0.1 μm). Got.

(Example 3)
In the electroless nickel plating step, Example 1 except that the plating reaction was terminated when the sodium ion concentration in the electroless plating solution at the end of the electroless plating reaction was 4.0 times the nickel ion concentration. Similarly, nickel plating particles were obtained.

  Conductive particles in which electroless palladium plating was performed on the surface of the obtained nickel plating particles in the same manner as in Example 1 to form a palladium layer (thickness 0.03 μm) on the surface of the nickel layer (thickness 0.1 μm). Got.

(Example 4)
(1) Electroless nickel plating step (step of forming protrusions on the surface of the nickel layer)
1-1) Palladium adhesion process 10 g of divinylbenzene resin particles having an average particle diameter of 4 μm were prepared. The resin particles were etched and washed with water. Next, resin particles were added to 100 mL of a palladium-catalyzed solution containing 8% by weight of a palladium catalyst and stirred. Thereafter, resin particles were added to a 0.5 wt% dimethylamine borane solution having a pH of 6, filtered, and washed to obtain resin particles having palladium attached thereto.

1-2) Core substance adhesion step The resin particles to which palladium was adhered were stirred and dispersed in 300 mL of ion-exchanged water for 3 minutes to obtain a dispersion. Next, 1 g of a metallic nickel particle slurry (“2020SUS” manufactured by Mitsui Kinzoku Co., Ltd., average particle diameter 200 nm) was added to the dispersion over 3 minutes to obtain resin particles to which a core substance was adhered.

1-3) Electroless nickel plating step 500 mL of ion-exchanged water was added to the resin particles to which the core substance was adhered, and the resin particles were sufficiently dispersed to obtain a suspension. While stirring this suspension, an electroless nickel plating solution having a pH of 5.0 containing nickel sulfate hexahydrate 50 g / L, sodium hypophosphite monohydrate 30 g / L and citric acid 50 g / L was gradually added. And electroless nickel plating. The plating reaction was completed when the sodium ion concentration in the electroless plating solution was 2.5 times the nickel ion concentration. In this way, a nickel layer was formed on the surface of the resin particles, and nickel plated particles having protrusions on the surface were obtained. The nickel layer had a thickness of 0.1 μm.

(2) Electroless palladium plating step Conductive particles having a palladium layer formed on the surface of the nickel layer are obtained by performing the same electroless palladium plating step as in Example 1 using 10 g of the obtained nickel plating particles. Obtained. The obtained conductive particles had protrusions on the surface.

(Example 5)
Divinylbenzene resin particles are copolymerized resin particles of 1,4-butanediol diacrylate and tetramethylolmethane tetraacrylate (1,4-butanediol diacrylate: tetramethylolmethane tetraacrylate = 95 wt%: 5 wt% The conductive particles were obtained in the same manner as in Example 4 except that the change was changed to The obtained conductive particles had protrusions on the surface.

(Example 6)
(1) Production of insulating resin particles In a 1000 mL separable flask equipped with a four-neck separable cover, a stirring blade, a three-way cock, a condenser tube and a temperature probe, 100 mmol of methyl methacrylate and N, N, N- Ion exchange of a monomer composition containing 1 mmol of trimethyl-N-2-methacryloyloxyethylammonium chloride and 1 mmol of 2,2′-azobis (2-amidinopropane) dihydrochloride so that the solid content is 5% by weight After weighing in water, the mixture was stirred at 200 rpm and polymerized at 70 ° C. for 24 hours in a nitrogen atmosphere. After completion of the reaction, freeze drying was performed to obtain insulating resin particles having an ammonium group on the surface, an average particle diameter of 220 nm, and a CV value of 10%.

  Insulating resin particles were dispersed in ion exchange water under ultrasonic vibration to obtain a 10 wt% aqueous dispersion of insulating resin particles.

  10 g of conductive particles having protrusions on the surface obtained in Example 5 were dispersed in 500 mL of ion exchange water, 4 g of an aqueous dispersion of insulating resin particles was added, and the mixture was stirred at room temperature for 6 hours. After filtration with a 3 μm mesh filter, the particles were further washed with methanol and dried to obtain conductive particles having insulating resin particles attached thereto.

  When observed with a scanning electron microscope (SEM), only one coating layer of insulating resin particles was formed on the surface of the conductive particles. When the coated area of the insulating resin particles (that is, the projected area of the particle diameter of the insulating resin particles) with respect to the area of 2.5 μm from the center of the conductive particles was calculated by image analysis, the coverage was 30%.

(Example 7)
Divinylbenzene resin particles are copolymerized resin particles of 1,4-butanediol diacrylate and tetramethylolmethane tetraacrylate (1,4-butanediol diacrylate: tetramethylolmethane tetraacrylate = 95 wt%: 5 wt% The conductive particles were obtained in the same manner as in Example 1 except that the above was changed.

(Example 8)
Except having changed the electroconductive particle obtained in Example 5 into the electroconductive particle obtained in Example 1, it carried out similarly to Example 6, and obtained the electroconductive particle to which the insulating resin particle adhered.

Example 9
Conductive particles with insulating resin particles attached in the same manner as in Example 6 except that the conductive particles obtained in Example 5 were changed to conductive particles having protrusions on the surface obtained in Example 4. Got.

(Example 10)
Except having changed the electroconductive particle obtained in Example 5 into the electroconductive particle obtained in Example 7, it carried out similarly to Example 6, and obtained the electroconductive particle to which the insulating resin particle adhered.

(Example 11)
In the electroless palladium plating step, the same as in Example 1 except that the complexing agent was changed to an electroless plating solution having a pH of 9.0 containing 35 mmol / L of ethylenediamine, 50 mmol / L of sodium formate as a reducing agent, and a crystal modifier. Thus, conductive particles having a palladium layer formed on the surface of the nickel layer were obtained.

(Example 12)
In the same manner as in Example 1, except that sodium hypophosphite monohydrate in the electroless nickel plating step of Example 1 was changed to potassium hypophosphite monohydrate, palladium was deposited on the surface of the nickel layer. The electroconductive particle in which the layer was formed was obtained.

(Example 13)
Conductive particles (nickel plated particles) in which a nickel layer is formed on the surface of the resin particles in the same manner as in Example 1, except that the electroless palladium plating step following the electroless nickel plating step of Example 1 was not performed. Got.

(Example 14)
A nickel layer is formed on the surface of the resin particles in the same manner as in Example 4 except that the electroless palladium plating step following the electroless nickel plating step of Example 4 is not performed. Particles (nickel plating particles) were obtained.

(Comparative Example 1)
In the electroless nickel plating step, when the sodium ion concentration in the electroless plating solution at the end of the electroless plating reaction is 4.2 times the nickel ion concentration, Example 1 is the same as in Example 1 except that the plating reaction is ended. Similarly, nickel plating particles were obtained.

  Conductive particles in which electroless palladium plating was performed on the surface of the obtained nickel plating particles in the same manner as in Example 1 to form a palladium layer (thickness 0.03 μm) on the surface of the nickel layer (thickness 0.1 μm). Got.

(Comparative Example 2)
In the electroless nickel plating step, when the sodium ion concentration in the electroless plating solution at the end of the electroless plating reaction is 10 times the nickel ion concentration, the same as in Example 1 except that the plating reaction is ended. Thus, nickel plating particles were obtained.

  Conductive particles in which electroless palladium plating was performed on the surface of the obtained nickel plating particles in the same manner as in Example 1 to form a palladium layer (thickness 0.03 μm) on the surface of the nickel layer (thickness 0.1 μm). Got.

(Comparative Example 3)
To 800 parts by weight of a 3% aqueous solution of polyvinyl alcohol, add a mixture of 70 parts by weight of divinylbenzene, 30 parts by weight of trimethylolpropane tri (meth) acrylate, and 2 parts by weight of benzoyl peroxide and adjust the particle size by stirring with a homogenizer. went. Thereafter, the mixture was heated to 80 ° C. under a nitrogen stream with stirring, and reacted for 15 hours to obtain particles.

  The obtained particles were washed with distilled water and methanol and then subjected to classification operation to obtain resin particles having an average particle size of 4.1 μm and a coefficient of variation of 5.0%.

  Etching was performed by dispersing 10 g of the obtained resin particles in a pre-dip solution for powder plating (Okuno Pharmaceutical Co., Ltd.) and stirring at 30 ° C. for 30 minutes. After washing with water, the solution was added to 100 ml of a Pd catalyst containing 1% by weight of palladium sulfate and stirred at 30 ° C. for 30 minutes to adsorb palladium ions to the particles. The particles were collected by filtration and washed with water, and then added to a 0.5% by weight dimethylamine borane solution (adjusted to pH 6.0) to obtain resin particles with activated Pd.

  To the obtained Pd activated resin particles, 500 ml of distilled water was added and sufficiently dispersed using an ultrasonic processor to obtain a particle suspension. While stirring this suspension at 50 ° C., an electroless plating solution (pH: 7.5) consisting of nickel sulfate (hexahydrate) 50 g / L, sodium hypophosphite 40 g / L, and citric acid 50 g / L. Was added gradually and electroless nickel plating was performed. When the metal coating layer became approximately 0.10 μm, the addition of the electroless plating solution was stopped, and after substitution with alcohol, the particles were vacuum dried to obtain conductive particles.

  Further, 1 g of the obtained conductive particles was dispersed in 1000 ml of distilled water (specific resistance 18 MΩ), placed in an autoclave equipped with a stirrer, and stirred and washed at 121 ° C. for 10 hours under a pressure of 0.1 MPa. Then, it filtered and dried and obtained the electroconductive particle.

(Comparative Example 4)
After etching 10 g of the resin particles obtained in Comparative Example 3 in the same manner as in Comparative Example 3, a catalyst comprising 10 mL of a Pd catalyst containing tin chloride (Okuno Pharmaceutical Co., Ltd., catalyst), 10 mL of 37% hydrochloric acid, and 10 mL of ethanol. It was added to the liquid and stirred at 30 ° C. for 30 minutes. The particles were collected by filtration, washed with 100 mL of 5% sulfuric acid, and then washed with water to obtain resin particles in which Pd was activated. The particles were electroless nickel-plated in the same manner as in Comparative Example 3, substituted with alcohol, and then vacuum dried to obtain conductive particles. Further, 1 g of the obtained conductive particles was dispersed in 1000 mL of distilled water (specific resistance 18 MΩ) in the same manner as in Comparative Example 3, and washed with stirring at 121 ° C. for 10 hours under a pressure of 0.1 MPa. Then, it filtered and dried and obtained the electroconductive particle.

(Comparative Example 5)
The conductive particles obtained in Comparative Example 4 were dispersed again in 1000 mL of distilled water (specific resistance 18 MΩ), and were stirred and washed at 121 ° C. for 10 hours under a pressure of 0.1 MPa in the same manner as in Comparative Example 3 to obtain conductive particles. Obtained.

(Comparative Example 6)
The conductive particles obtained in Comparative Example 5 were stirred and washed at 121 ° C. for 10 hours under a pressure of 0.1 MPa to obtain conductive particles.

(Evaluation)
(1) Content of alkali metals (including sodium and potassium), sodium and potassium in the nickel layer A thin film slice of the obtained conductive particles was prepared using a focused ion beam. Alkali metal content in the entire nickel layer of the obtained conductive particles using an energy dispersive X-ray analyzer (EDS) using a transmission electron microscope FE-TEM (“JEM-2010FEF” manufactured by JEOL Ltd.) A, sodium content A and potassium content A, and alkali metal content B, sodium content B and potassium content B in the 30 nm thick region of the outer surface of the nickel layer were measured.

(2) Operational reliability [Evaluation of defective IC operation in a connection structure in which the drive part of the STN type liquid crystal display element is connected by conductive particles]
An SiO ₂ film was deposited on one surface of a pair of transparent glass substrates (150 mm × 150 mm thickness 0.4 mm) by a CVD method, and then an ITO film was formed on the entire surface of the SiO ₂ film by sputtering. A drive electrode was formed on the outer periphery of one substrate. After a polyimide alignment film (“SE-3510” manufactured by Nissan Chemical Industries, Ltd.) is applied to the formed glass substrate with an ITO film by spin coating and baked at 280 ° C. for 90 minutes, this alignment film is formed. The glass substrate was rubbed. Next, spacers for a liquid crystal display element are spread on the alignment film side of one glass substrate so that the number of spacers is 100 to 200 per mm ² using a dry-type spreader (manufactured by Nissin Engineering Co., Ltd., DISPA-μR). did. Further, after forming a peripheral sealant around the other glass substrate so as to expose the drive electrode, the glass substrate on which spacers are dispersed is arranged so as to face the rubbing direction at 90 °, and the two glass substrates Were pasted together. Then, it processed at 160 degreeC for 90 minute (s), the sealing agent was hardened, and the empty cell (screen which does not contain a liquid crystal) was produced. An STN type liquid crystal containing a chiral agent (“RDP-95873” manufactured by DIC) was injected into the resulting empty cell, and then the injection port was closed with a sealant to produce an STN type liquid crystal display device. For 30 minutes.

  The drive IC used was a STN-LCD common driver (LC41385KBR) manufactured by Sanyo Semiconductor. An anisotropic conductive material was prepared for mounting the driving IC. That is, an anisotropic conductive paste containing 10 parts by weight of each conductive particle obtained in Examples and Comparative Examples and 90 parts by weight of XAP-0289 (manufactured by Kyocera Chemical Co.) containing a binder resin was prepared.

  The electrode of the drive IC and the drive electrode on the glass substrate were laminated so as to be in contact with each other through conductive particles, and were pressed to obtain a laminate. Then, the anisotropic conductive paste was hardened by heating a laminated body at 180 degreeC for 1 minute, and the connection structure was obtained. The obtained connection structure was left for 100 hours in a non-energized state at 40 ° C. and a humidity of 90%. A lighting test of the connection structure (liquid crystal display element) after being left was performed, and the failure rate of 4000 connection structures was evaluated.

[Criteria for operational reliability]
◎: Failure rate is less than 0.05% ○: Failure rate is 0.05% or more, less than 0.25% ×: Failure rate is 0.25% or more

(3) Curability of Binder Resin In order to evaluate the curability of the binder resin by ions eluted from the conductive particles, 10 parts by weight of each conductive particle obtained in Examples and Comparative Examples, and XAP-0289 (Kyocera Chemical) An anisotropic conductive paste containing 90 parts by weight) was prepared.
The obtained paste is applied to ITO glass, FPC (made by PI, wiring material is Cu / Ni / Au) is bonded, and temperature is 170 ° C. and pressure is 2 Mpa with an ACF crimping machine (“BD-03” manufactured by Ohashi Seisakusho) Thermocompression bonding was performed under conditions of a time of 10 seconds or 20 seconds. After performing the crimping operation, the adhesion state was observed, and the curability of the binder resin was determined according to the following criteria.

[Criteria for determination of curability of binder resin]
○: Completely cured with a crimping time of 10 seconds. △: Cured insufficiently with a crimping time of 10 seconds and easily peeled off, but completely cured with a crimping time of 20 seconds. Insufficient and easy peeling

  The results are shown in Table 1 below.

DESCRIPTION OF SYMBOLS 1 ... Conductive particle 2 ... Base material particle 3 ... Conductive layer 11 ... Nickel layer 12 ... Metal layer 21 ... Conductive particle 22 ... Conductive layer 23 ... Core substance 24 ... Protrusion 25 ... Insulating substance 31 ... Nickel layer 32 ... Metal Layer 51 ... Connection structure 52 ... First connection target member 52a ... Upper surface 52b ... Electrode 53 ... Second connection target member 53a ... Lower surface 53b ... Electrode 54 ... Connection portion

Claims (15)

Comprising substrate particles and a conductive layer;
The conductive layer has a nickel layer provided on the surface of the base particle,
Conductive particles wherein the content of alkali metal in the entire nickel layer exceeds 0 μg / g, and the content of alkali metal in a region of 30 nm thickness on the outer surface of the nickel layer is 80 μg / g or less.   The conductive particles according to claim 1, wherein the nickel layer is a nickel layer formed by an electroless plating reaction using an electroless plating solution containing a nickel salt and an alkali metal-containing reducing agent.   The electroconductive particle of Claim 1 or 2 in which the said alkali metal contains sodium.   4. The nickel layer according to claim 1, wherein the nickel layer is a nickel layer formed by an electroless plating reaction using an electroless plating solution containing a nickel salt and sodium hypophosphite. 5. Conductive particles.   The electroconductive particle of any one of Claims 1-4 in which the said electroconductive layer further has a metal layer arrange | positioned on the surface of the said nickel layer.   The electroconductive particle of any one of Claims 1-5 which has a processus | protrusion on the outer surface of the said conductive layer.   The electroconductive particle of any one of Claims 1-6 further provided with the insulating substance arrange | positioned on the surface of the said electroconductive layer.   The conductive particle according to claim 7, wherein the insulating substance is an insulating particle.   The electroconductive particle of any one of Claims 1-8 whose content of the said alkali metal in the said nickel layer whole exceeds 0 microgram / g and is 50 microgram / g or less. A step of forming a nickel layer by an electroless plating reaction using an electroless plating solution containing a nickel salt and an alkali metal-containing reducing agent on the surface of the substrate particles,
When the alkali metal ion concentration (mol / L) in the electroless plating solution at the end of the electroless plating reaction is not more than 4 times the nickel ion concentration (mol / L) in the electroless plating solution, By terminating the electroplating reaction, the alkali metal content in the entire nickel layer exceeds 0 μg / g, and the alkali metal content in the region of 30 nm thickness on the outer surface of the nickel layer is 80 μg / g or less. A method for producing conductive particles, which obtains certain conductive particles.   The method for producing conductive particles according to claim 10, wherein the alkali metal contains sodium.   The method for producing conductive particles according to claim 10 or 11, wherein an electroless plating solution containing a nickel salt and sodium hypophosphite is used as the electroless plating solution.   The manufacturing method of the electroconductive particle of any one of Claims 10-12 which obtains the electroconductive particle whose content of the said alkali metal in the said nickel layer exceeds 0 microgram / g and is 50 microgram / g or less.   An anisotropic conductive material containing the electroconductive particle of any one of Claims 1-9, and binder resin. A first connection target member, a second connection target member, and a connection portion that electrically connects the first and second connection target members;
The connection structure in which the connecting portion is formed of the conductive particles according to any one of claims 1 to 9, or is formed of an anisotropic conductive material including the conductive particles and a binder resin. body.

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