JP5536634B2 - Conductive fine particles - Google Patents

Description

  The present invention relates to fine conductive fine particles, and particularly relates to conductive fine particles capable of realizing a low resistance value when used for electrical connection.

  In recent years, miniaturization and high functionality of electronic devices have been increasingly progressed. Along with this, electronic components mounted on electric devices are being downsized and mounted with high density, and electrodes and wirings in electronic circuits are becoming finer and narrower. 2. Description of the Related Art Conventionally, in assembling electronic devices, a connection method using an anisotropic conductive material has been adopted to make electrical connection between a large number of opposing electrodes and wirings. An anisotropic conductive material is a material in which a binder resin or the like is mixed with conductive fine particles. For example, anisotropic conductive paste (ACP), anisotropic conductive ink, anisotropic conductive film (ACF), anisotropic conductive There are sheets. In addition, as the conductive fine particles used for the anisotropic conductive material, those obtained by coating the surface of polymer fine particles used as metal particles or base particles with a conductive metal layer are used.

  As described above, with the progress of miniaturization and narrowing of the electrodes and wirings of electronic circuits, conductive fine particles used for anisotropic conductive materials are also required to have a smaller particle diameter. As such conductive particles having a small particle size, for example, a microsphere made of a resin or an inorganic compound and having an average particle size of 0.5 to 2.5 μm and a particle size CV value of 20% or less is used as a base material. The conductive fine particles used have been proposed (see Patent Document 1 (paragraphs 0009 and 0010)).

  Further, the conductive fine particles preferably have a low connection resistance value and a stable connection in making an electrical connection between electrodes and wiring. From such a viewpoint, various studies have been made on conductive metal layers constituting conductive fine particles. For example, Patent Document 2 proposes the use of a low-melting-point metal as the conductive metal layer for the purpose of metal-bonding the electrode and the conductive metal layer in order to stabilize the connection (Patent Document 2). 2 (paragraph 0016)). In addition, it has been proposed to use a specific tin-based alloy plating film as a conductive metal layer in order to increase solder wettability in conductive fine particles used in ball grid array mounting methods and flip chip bonding methods. (See Patent Document 3 (paragraph 0011)).

JP 2000-30526 A JP 2000-1333050 A JP 2001-220691 A

  When the particle diameter of the conductive fine particles is reduced, the connection area obtained by deformation of the conductive fine particles becomes very small at the time of pressure connection, and the connection resistance value in electrical connection tends to increase. In recent years, in particular, in order to reduce physical damage to the substrate or film on which electrodes and wiring are formed, the number of cases in which a low pressure is applied during pressure connection has increased. There was a tendency that the deformation of the conductive fine particles became smaller and the connection resistance value further increased. Moreover, since the conductive metal layer is hard in the electroconductive fine particles which gave nickel plating as a conductive metal layer like patent document 1, the deformation | transformation of base particle will be inhibited with this electroconductive metal layer. Therefore, there is a problem that the deformation amount of the conductive fine particles is further reduced and the connection resistance value is further increased.

  The present invention has been made in view of the above circumstances, and is a very small conductive fine particle having a number average particle diameter of 1.1 μm to 2.8 μm, and realizes a low resistance value when used for electrical connection. An object is to provide conductive fine particles.

  The conductive fine particles of the present invention capable of solving the above problems are conductive fine particles having a base material composed of resin particles and at least one conductive metal layer formed on the surface of the base material, The number average particle diameter of the conductive fine particles itself is 1.1 μm to 2.8 μm, and at least one layer of the conductive metal layer has a low melting point metal layer formed of a low melting point metal having a melting point of 400 ° C. or less. The low melting point metal layer has a thickness of 0.005 μm to 0.10 μm.

  When the conductive metal layer is a multilayer, the outermost layer is preferably the low melting point metal layer. As the low melting point metal, tin and a tin-containing alloy are suitable. The number average particle diameter of the resin particles is preferably 1.0 μm to 2.5 μm.

  According to the present invention, even a very small conductive fine particle having a number average particle diameter of 1.1 μm to 2.8 μm can realize a low resistance value and can be short-circuited when used for electrical connection. Can be reduced.

1. TECHNICAL FIELD The present invention aims to improve fine conductive fine particles. The conductive fine particles to be the subject of the present invention have a number average particle diameter of 1.1 μm or more, preferably 1.2 μm or more, more preferably 1.3 μm or more, and further preferably 1.4 μm or more. It is 8 μm or less, preferably 2.6 μm or less, more preferably 2.4 μm or less, and further preferably 2.2 μm or less. If the number average particle diameter is within this range, it can be suitably used for electrical connection of miniaturized and narrowed electrodes and wirings.

  The fine conductive fine particles of the present invention are composed of a substrate made of resin particles and one or more conductive metal layers formed on the surface of the substrate, and at least one of the conductive metal layers has a melting point. It is formed from a low melting point metal of 400 ° C. or lower. In the case of conductive fine particles having a very small particle diameter, the connection area obtained by deformation of the conductive fine particles during pressure connection is very small. For this reason, in the case where a hard metal such as nickel plating is used as the conductive metal layer as in the prior art, the connection resistance value tends to be higher as the particle diameter of the conductive fine particles is smaller. However, the conductive metal layer made of a low-melting-point metal can be easily melted at the heating temperature at the time of connection by heating and pressurization, and can form a metal bond with an electrode or the like as a connected body. Therefore, the conductive fine particles of the present invention are used when they are used for electrical connection even though they have a small diameter due to surface contact obtained by deformation of the conductive fine particles themselves and metal bonding by melting of the low melting point metal layer. A low resistance value can be realized.

  Examples of the low melting point metal include metals having a melting point of 400 ° C. or lower, such as tin (Sn) (melting point: 232 ° C.), lead (Pb) (melting point: 328 ° C.), bismuth (Bi) (melting point: 271 ° C.). Tin, lead, gold (Au), silver (Ag), zinc (Zn), copper (Cu), iron (Fe), bismuth, aluminum (Al), cobalt (Co), indium (In), nickel (Ni) ), Chromium (Cr), titanium (Ti), antimony (Sb), phosphorus (P), germanium (Ge), tellurium (Te), gallium (Ga), manganese (Mn), molybdenum (Mo), palladium (Pd) 2) or more types of alloys selected from the above. Specific examples of the alloy include Sn / Pb, Sn / Au, Sn / Ag, Sn / Cu, Sn / Zn, Sn / Sb, Sn / Pb / Bi, Sn / Pb / Ag, Sn / Pb / Cu, Tin-containing alloys such as Sn / Bi / Ag, Sn / Bi / In, Sn / Ag / Cu; Pb / Ag, Zn / Al, Au / Si and the like. Among these, as the low melting point metal, tin-containing alloys such as tin and tin-silver alloys are preferable.

  In order to improve the bonding strength between the low melting point metal layer and the electrode, the low melting point metal is nickel, antimony, aluminum, iron, gold, titanium, phosphorus, germanium, tellurium, gallium, cobalt, manganese, chromium. It is preferable to contain molybdenum, palladium, and indium. In particular, the low-melting-point metal preferably contains nickel, antimony, and aluminum because it has an excellent effect of improving the bonding strength between the low-melting-point metal layer and the electrode. In addition, when these metals are contained, the content in the low melting point metal layer is preferably 0.0001% by mass (more preferably 0.0015% by mass, and still more preferably 0.0002% by mass). The greater the content, the higher the bonding strength between the low melting point metal layer and the electrode or the like. On the other hand, if the content is too large, the flexibility of the conductive fine particles may be lowered. Therefore, the content is 2.0% by mass (more preferably 1.9% by mass, and still more preferably 1.8% by mass). %) Or less is preferable.

  The melting point of the low melting point metal is 400 ° C. or less, preferably 300 ° C. or less, more preferably 250 ° C. or less, and further preferably 240 ° C. or less. The lower the melting point, the lower the resistance value can be achieved even at a lower heating temperature in the pressure connection when performing the electrical connection. The lower limit of the melting point of the low melting point metal is not particularly limited, but is usually about 200 ° C.

  The thickness of the low melting point metal layer is 0.005 μm or more, preferably 0.010 μm or more, more preferably 0.015 μm or more, 0.10 μm or less, preferably 0.07 μm or less, more preferably 0.065 μm or less. It is. If the low-melting point metal layer is 0.005 μm or more, the metal junction area by the low-melting point metal layer is increased. Therefore, when used for electrical connection, the connection resistance value can be further reduced, and if it is 0.10 μm or less, By making use of the characteristics of the resin particles that are the base material and making the conductive fine particles more flexible, the connection resistance value can be lowered, and short-circuiting between the electrodes can be suppressed, thereby improving connection reliability. The low melting point metal layer may be provided with a plurality of layers having different compositions. In this case, the total thickness of the low melting point metal layer may be set in the above range.

  The conductive metal layer may be a single layer or multiple layers (two or more layers). When the conductive metal layer is a multilayer, it may have a layer made of a metal other than the low melting point metal. Other metals include, for example, refractory metals having melting points of over 400 ° C. such as nickel, palladium, gold, silver, copper, platinum, iron, cobalt, titanium, zinc, and aluminum; these metals and tin, lead, bismuth 2 or more kinds of alloys selected from metals having a melting point of 400 ° C. or lower, etc., and alloys having a melting point higher than 400 ° C .; In particular, in order to improve the adhesion of the low-melting-point metal layer to the resin particles as the base material, a high-melting-point metal coating layer (preferably a nickel layer or a copper layer) is formed as the base layer of the low-melting-point metal layer. Is preferred. When forming layers other than these low melting point metal layers, it is preferable that the film thickness of the whole electroconductive metal layer is 0.10 micrometer (preferably 0.09 micrometer, more preferably 0.08 micrometer) or less. In addition, when an electroconductive metal layer is a multilayer, it is preferable that an outermost layer is a low melting metal layer.

  The method for forming the conductive metal layer is not particularly limited, for example, a method in which the surface of the substrate is plated by an electroless plating method, an electrolytic plating method, or the like; physical properties such as vacuum deposition, ion plating, ion sputtering on the surface of the substrate A method of forming a conductive metal layer by a general vapor deposition method; Among these, the electroless plating method is particularly preferable in that a conductive metal layer can be easily formed without requiring a large-scale apparatus.

  When forming a conductive metal layer by an electroless plating method, it is preferable to perform an electroless plating step after an etching step and a catalytic step.

Etching treatment step In the etching treatment step, an oxidizing agent such as chromic acid, chromic anhydride-sulfuric acid mixture, permanganic acid; strong acid such as hydrochloric acid, sulfuric acid, hydrofluoric acid and nitric acid; strong alkali such as sodium hydroxide and potassium hydroxide A fine unevenness is formed on the surface of the resin particles using a solution; etc., and the adhesion effect between the electroless plated resin particles described later and the conductive metal layer is improved by the anchor effect of the unevenness.

Catalytic Step In the catalytic step, a palladium catalyst that serves as a base point for plating deposition is adsorbed on the surface of the resin particles. The method for adsorbing the palladium catalyst is not particularly limited, and may be performed using a catalytic reagent commercially available for electroless plating. As a method for catalyzing, for example, a solution containing palladium chloride and stannous chloride is used as a catalyzing reagent, and resin particles are immersed in this solution to adsorb palladium ions on the surface of the resin particles, and then sulfuric acid, hydrochloric acid, etc. A method of depositing palladium on the surface of resin particles by reducing the palladium ions with an alkaline solution such as acid or sodium hydroxide (catalyst-accelerator method) or a solution containing tin ions (Sn ²⁺ ) A method in which tin ions are adsorbed on the surface of resin particles by bringing the particles into contact with each other and then immersed in a solution containing palladium ions (Pd ²⁺ ) to precipitate palladium on the surface of the resin particles (Sensitizing-Activate) Ting method) and the like.

  The liquid temperature and immersion time when the resin particles are immersed in the tin ion-containing solution and the palladium ion-containing solution are not particularly limited as long as each ion can be sufficiently adsorbed to the resin particles, and may be adjusted as appropriate. C. to 60.degree. C. is preferable, and the immersion time is preferably 1 minute to 120 minutes.

Electroless Plating Step In the electroless plating step, a conductive metal layer is formed on the surface of the catalytic resin particles that have adsorbed the palladium catalyst in the catalytic step. Specifically, by immersing catalyzed resin particles in a plating solution in which a reducing agent and a desired metal salt are dissolved, starting from a palladium catalyst, metal ions in the plating solution are reduced with the reducing agent, and resin particles A desired metal is deposited on the surface to form a conductive metal layer.

  In the electroless plating step, first, the catalyzed resin particles are sufficiently dispersed in water to prepare an aqueous slurry of the catalyzed resin particles. Here, in order to develop stable conductive characteristics, it is preferable to sufficiently disperse the catalyzed resin particles in an aqueous medium to be plated. As a means for dispersing the catalyzed resin particles in the aqueous medium, for example, a conventionally known dispersing means such as a normal stirring device, a high-speed stirring device, a shearing dispersion device such as a colloid mill or a homogenizer may be employed, and as necessary. You may use together an ultrasonic wave and a dispersing agent (surfactant etc.).

  Next, an electroless plating solution containing the desired conductive metal salt, reducing agent, complexing agent, various additives, and the like is added to the electroless plating solution prepared above to produce an electroless Causes a plating reaction. The electroless plating reaction starts quickly when an aqueous slurry of catalyzed resin particles is added. Moreover, since this reaction is accompanied by the generation of hydrogen gas, the electroless plating reaction may be terminated when the generation of hydrogen gas is not recognized. After the electroless plating reaction is completed, the resin particles on which the conductive metal layer is formed are taken out from the reaction system, and washed and dried as necessary to obtain conductive fine particles.

  Examples of the conductive metal salt include metal chlorides, sulfates, acetates and the like exemplified as the metal constituting the conductive metal layer. For example, when a tin layer is formed as the conductive metal layer, the metal salt contained in the electroless plating solution includes tin (II) chloride, tin (II) bromide, tin (II) iodide, tin oxide ( II), stannous salts such as tin (II) sulfate (tin salts (II)); and second tin salts (tin salts (IV)) such as sodium stannate and potassium stannate. These tin salts can be used alone or in combination of two or more. In addition, either a divalent first tin salt (tin salt (II)) or a tetravalent second tin salt (IV) having a valence of tin may be used. Is preferably used. For example, when nickel plating is formed as the conductive metal layer, nickel salts such as nickel chloride, nickel sulfate, and nickel acetate may be included in the electroless plating solution. The concentration of the conductive metal salt in the electroless plating solution may be appropriately determined in consideration of the size (surface area) of the resin particles so that a conductive metal layer having a desired film thickness is formed.

  Examples of the reducing agent include titanium compounds such as titanium trichloride, titanium triiodide, titanium tribromide; formaldehyde, sodium hypophosphite, dimethylamine borane, sodium borohydride, potassium borohydride, tetrahydrobora. Examples include potassium acid, glyoxylic acid, hydrazine and the like. Only one reducing agent may be used, or two or more reducing agents may be used. Among these, a titanium compound is suitable for the electroless tin plating solution.

  As the complexing agent, a compound having a complexing action on the conductive metal ions can be used. For example, compounds having a complexing action on tin include glycerol, tartaric acid, iminodiacetic acid, citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid or alkali metal salts thereof (for example, sodium citrate). ) And carboxylic acids (salts) such as ammonium salts; sugars such as D-sorbitol and dulcitol; aminos such as glycine; amine acids such as ethylenediamine, triethanolamine and alkylamine; other ammoniums and EDTA (ethylenediaminetetraacetic acid) Or a salt thereof (for example, EDTA4Na (ethylenediaminetetraacetic acid tetrasodium)), nitrilotriacetic acid (NTA) or a salt thereof (for example, trisodium nitrilotriacetic acid), 2,2′-bipyridine, pyrophosphoric acid (salt); Can be mentioned. Only one type of complexing agent may be used, or two or more types may be used.

  The pH of the electroless plating solution is not limited, but is preferably 4-14.

  The electroless plating process may be repeated as necessary. For example, by repeating the electroless plating process using electroless plating solutions of different metal types, the surface of the resin particles can be coated with several layers of different metals. Specifically, after nickel plating is performed on the resin particles to obtain nickel-coated particles, the nickel-coated particles are further poured into an electroless tin plating solution to perform tin plating, so that the outermost layer is covered with a tin layer. Thus, conductive fine particles having a nickel layer inside are obtained. In addition, for example, a tin-containing alloy layer can be formed by forming a layer made of a metal different from tin (for example, silver) on tin plating and then performing heat treatment to cause metal thermal diffusion. .

  In order to adjust the film thickness of the conductive metal layer, specifically, the resin particle concentration (amount of resin particles per treatment liquid) during electroless plating treatment and the electroless plating used in the electroless plating treatment What is necessary is just to adjust the density | concentration of liquid, pH, the reaction temperature of an electroless-plating process, etc. For example, if the amount of the resin particles with respect to the treatment liquid for the electroless plating treatment is increased or the concentration of the electroless plating liquid used in the electroless plating treatment is reduced, the film thickness of the conductive metal layer is reduced.

  The conductive fine particles use resin particles as a base material for forming the conductive metal layer. The resin particles only need to contain a resin component, and are not limited to particles composed only of organic materials, but may be particles composed of organic-inorganic composite materials. By using resin particles, conductive fine particles having excellent elastic deformation characteristics can be obtained.

  Examples of the organic material constituting the resin particles include polyolefins such as polyethylene, polypropylene, polyvinyl chloride, polytetrafluoroethylene, polyisobutylene, and polybutadiene; vinyl heavy resins such as styrene resins, acrylic resins, and styrene-acrylic resins. Polyesters such as polyethylene terephthalate and polyethylene naphthalate; polycarbonates; polyamides; polyimides; phenol formaldehyde resins; melamine formaldehyde resins; melamine benzoguanamine formaldehyde resins; urea formaldehyde resins; Examples of the organic-inorganic composite material include a material containing the organic material and a polysiloxane skeleton (for example, a material in which a polysiloxane skeleton and a vinyl polymer are combined). The material which comprises these resin particles may be used independently, and 2 or more types may be used together.

  Among the materials constituting the resin particles, those containing a vinyl polymer and / or a polysiloxane skeleton are preferable. A material containing a vinyl polymer has an organic skeleton formed by polymerizing vinyl groups, and is excellent in elastic deformation during pressure connection. In particular, a vinyl polymer containing divinylbenzene as a polymerization component has little decrease in particle strength after coating with a conductive metal. In addition, the material containing the polysiloxane skeleton has excellent contact pressure with respect to the connected body during pressure connection. In particular, a material in which a polysiloxane skeleton and a vinyl polymer are combined is preferable because it is excellent in elastic deformability and contact pressure, and the connection reliability of the obtained conductive fine particles becomes more excellent.

  The vinyl polymer is obtained by polymerizing a vinyl group-containing monomer (radical polymerization), and the “vinyl group” includes not only a carbon-carbon double bond but also a (meth) acryloxy group, an allyl group, isopropenyl. Substituents having a polymerizable carbon-carbon double bond such as a group, vinylphenyl group and isopropenylphenyl group are also included. In this specification, “(meth) acryloxy group”, “(meth) acrylate” and “(meth) acryl” are “acryloxy group and / or methacryloxy group”, “acrylate and / or methacrylate” and “acryl and / Or methacryl ".

  The vinyl group-containing monomer includes a monomer (1) having one vinyl group in the molecule, one vinyl group in the molecule and a functional group other than the vinyl group (a protic hydrogen such as a carboxyl group or a hydroxyl group). Monomer having a terminal group such as a containing group and an alkoxy group) (2) a crosslinkable vinyl group-containing monomer having three or more vinyl groups in one molecule (hereinafter referred to as “crosslinkable vinyl”). Sometimes referred to as a “group-containing monomer”). These monomers (1) to (3) may be used alone or in combination of two or more. Among these, the crosslinkable vinyl group-containing monomer (3) is preferable.

  Examples of the monomer (1) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, Hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. Alkyl (meth) acrylates; cyclopropyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, cycloundecyl (meth) a Cycloalkyl (meth) acrylates such as relate, cyclododecyl (meth) acrylate, isobornyl (meth) acrylate, 4-t-butylcyclohexyl (meth) acrylate; phenyl (meth) acrylate, benzyl (meth) acrylate, tolyl (meth) ) Aromatic ring-containing (meth) acrylates such as acrylate and phenethyl (meth) acrylate; alkyl such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, and pt-butylstyrene And styrene monofunctional monomers such as halogen group-containing styrenes such as styrenes, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene. A monomer (1) may be used independently and may use 2 or more types together. Among these, styrene monofunctional monomers are preferable, and styrene is more preferable.

  Examples of the monomer (2) include monomers having a carboxyl group such as (meth) acrylic acid; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy Monomers having hydroxy groups such as hydroxy group-containing (meth) acrylates such as butyl (meth) acrylate, hydroxy group-containing styrenes such as p-hydroxystyrene; 2-methoxyethyl (meth) acrylate, 3-methoxybutyl Examples include (meth) acrylates, alkoxy group-containing (meth) acrylates such as 2-butoxyethyl (meth) acrylate, and monomers having an alkoxy group such as alkoxystyrenes such as p-methoxystyrene. A monomer (2) may be used independently and may use 2 or more types together. Here, a carboxyl group, a hydroxy group, an alkoxy group, and the like can form a crosslinked structure when a group serving as a reaction (bonding) partner is present in another monomer.

  Examples of the monomer (3) (crosslinkable vinyl group-containing monomer) include allyl (meth) acrylates such as allyl (meth) acrylate; ethylene glycol di (meth) acrylate and 1,4-butanediol. Di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, 1,3-butylene di (meth) Alkanediol di (meth) acrylate such as acrylate; diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, decaethylene glycol di (meth) acrylate, pentadecaethylene glycol di (meth) acrylate, penta contactor ethylene Glycol di (meta Di (meth) acrylates such as polyalkylene glycol di (meth) acrylate such as acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate; trimethylolpropane tri Tri (meth) acrylates such as (meth) acrylate; Tetra (meth) acrylates such as pentaerythritol tetra (meth) acrylate; Hexa (meth) acrylates such as dipentaerythritol hexa (meth) acrylate; Divinylbenzene, divinyl Aromatic hydrocarbon crosslinking agents such as naphthalene and derivatives thereof (preferably styrenic polyfunctional monomers such as divinylbenzene); N, N-divinylaniline, divinyl ether, Vinyl sulfide, hetero atom-containing crosslinking agents such as divinyl sulfonic acid; and the like. These crosslinkable vinyl group-containing monomers may be used alone or in combination of two or more. Among these, a monomer having two or more (meth) acryloyl groups in one molecule and a styrene polyfunctional monomer are preferable. Among the monomers having two or more (meth) acryloyl groups in one molecule, a monomer having two or more acryloyl groups in one molecule is preferable and has two acrylyl groups in one molecule. Monomers (diacrylates) are more preferable, alkanediol diacrylate and polyalkylene glycol diacrylate are more preferable, and alkanediol diacrylate is particularly preferable. Of the styrenic polyfunctional monomers, divinylbenzene is preferred.

  The vinyl polymer includes, as a constituent, the crosslinkable vinyl group-containing monomer (3); the monomer (1) and the crosslinkable vinyl group-containing monomer (3). Is preferred. Specifically, as the former, as a constituent, an embodiment containing a monomer having two or more (meth) acryloyl groups in one molecule; an embodiment containing a styrene polyfunctional monomer; two or more in one molecule An embodiment comprising a monomer having a (meth) acryloyl group and a styrenic polyfunctional monomer is preferred. The latter includes a styrene monofunctional monomer and a monomer having two or more (meth) acryloyl groups in one molecule. And an embodiment containing a styrene monofunctional monomer and a styrene polyfunctional monomer are preferred.

  The polysiloxane skeleton is obtained by hydrolytic condensation of a silane monomer, and examples of the silane monomer include non-crosslinkable silane monomers and crosslinkable silane monomers. Examples of the non-crosslinkable silane monomer include bifunctional silane monomers such as dialkylsilane such as dimethyldimethoxysilane and dimethyldiethoxysilane; and trialkylsilane such as trimethylmethoxysilane and trimethylethoxysilane. And monofunctional silane-based monomers.

  The crosslinkable silane monomer can form a crosslinked structure. The cross-linked structure formed by the cross-linkable silane monomer includes one that cross-links an organic polymer skeleton (for example, a vinyl polymer skeleton) and an organic polymer skeleton (first form); One that crosslinks a polysiloxane skeleton (second form); one that crosslinks an organic polymer skeleton and a polysiloxane skeleton (third form).

  Examples of those that can form the first form include dimethyldivinylsilane, methyltrivinylsilane, and tetravinylsilane. Examples of what can form the second form include tetrafunctional silane monomers such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetrabutoxysilane; methyltrimethoxysilane, methyltriethoxysilane And trifunctional silane monomers such as ethyltrimethoxysilane and ethyltriethoxysilane. Examples of those that can form the third form include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, And those having a vinyl group such as 3-methacryloxyethoxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and p-styryltrimethoxysilane;

  Here, the polysiloxane skeleton preferably has a skeleton derived from a polymerizable polysiloxane having a radical-polymerizable carbon-carbon double bond (for example, a vinyl group or a (meth) acryloyl group). That is, the polysiloxane skeleton is a crosslinkable silane monomer (preferably having a (meth) acryloyl group, more preferably 3-methacryloxy) capable of forming at least the third form of the crosslinked structure as a constituent component. It preferably contains a polysiloxane skeleton formed by hydrolysis and condensation of propyltrimethoxysilane).

  The resin particles have a content of a crosslinkable monomer (crosslinkable vinyl group-containing monomer, crosslinkable silane monomer) of 5% by mass or more in all monomer components constituting the polymer. More preferably, it is 10 mass% or more, More preferably, it is 15 mass% or more, 80 mass% or less is preferable, More preferably, it is 70 mass% or less, More preferably, it is 60 mass% or less.

  The number average particle diameter of the resin particles (base material) is preferably 1.0 μm or more, more preferably 1.1 μm or more, further preferably 1.2 μm or more, particularly preferably 1.3 μm or more, and 2.5 μm. The following is preferable, more preferably 2.3 μm or less, further preferably 2.1 μm or less, and particularly preferably 1.9 μm or less. The number-based variation coefficient (CV value) of the resin particles is preferably 10% or less, more preferably 8% or less, and even more preferably 6% or less.

  As the method for producing the resin particles, emulsion polymerization, suspension polymerization, dispersion polymerization, seed polymerization, sol-gel seed polymerization method and the like can be adopted, but seed polymerization and sol-gel seed polymerization method are preferable because the particle size distribution can be reduced. . The sol-gel seed polymerization method is an embodiment of seed polymerization, and particularly means that seed particles are synthesized by the sol-gel method. For example, the case where polysiloxane obtained by the hydrolysis condensation reaction of alkoxysilane is used as seed particles can be used. Therefore, the seed polymerization includes a case where the seed particles are made of an organic material and a case where the seed particles are made of a material in which an organic material and an inorganic material are combined (in the case of a sol-gel seed polymerization method).

  As described above, the resin particles preferably have a vinyl polymer skeleton and a polysiloxane skeleton. Therefore, as a method for producing resin particles, a crosslinkable silane monomer having a radical polymerizable group is hydrolyzed and subjected to a condensation reaction to prepare polymerizable polysiloxane particles, and then the above-mentioned vinyl is added to the polymerizable polysiloxane particles. The method of absorbing and polymerizing group-containing monomers and the like can be mentioned.

2. Resin-coated conductive fine particles The conductive fine particles of the present invention may further form an insulating resin layer on the surface of the conductive metal layer. The insulating resin layer is not particularly limited as long as the insulating property between the particles of the conductive fine particles can be ensured, and the insulating resin layer can be easily collapsed or peeled off by a constant pressure and / or heating. For example, polyolefins such as polyethylene; (meth) acrylate polymers and copolymers such as polymethyl (meth) acrylate; thermoplastic resins such as polystyrene; and particularly cross-linked products thereof; heat such as epoxy resins, phenol resins, and melamine resins Curable resins; water-soluble resins such as polyvinyl alcohol and mixtures thereof.

  However, when the insulating resin layer is too hard as compared with the resin particles serving as the base material, the resin particles themselves may be destroyed before the insulating resin layer is destroyed. Therefore, it is preferable to use uncrosslinked or relatively low degree of crosslinking resin for the insulating resin layer.

  The insulating resin layer may be a single layer or a plurality of layers. For example, single or multiple film-like layers; layers with insulating particles, spheres, lumps, scales and other shapes attached to the surface of the conductive fine particles; and the surface of the conductive fine particles is chemically modified Or a layer formed by doing so. The thickness of the resin insulation layer is preferably 0.01 μm to 1 μm, more preferably 0.02 μm to 0.5 μm, and still more preferably 0.03 μm to 0.4 μm. When the thickness of the resin insulating layer is within the above range, the electrical insulation between the particles is good while maintaining the conduction characteristics by the conductive fine particles.

3. Anisotropic Conductive Material The conductive fine particle of the present invention is also suitable as a constituent material of the anisotropic conductive material, and the anisotropic conductive material using the conductive fine particle of the present invention is also preferable implementation of the present invention. This is one aspect. The form of the anisotropic conductive material is not particularly limited as long as the conductive fine particles of the present invention are used. For example, an anisotropic conductive film, an anisotropic conductive paste, an anisotropic conductive adhesive is used. And various forms such as anisotropic conductive ink. That is, electrical connection can be achieved by providing these anisotropic conductive materials between opposing substrates or between electrode terminals. The anisotropic conductive material using the conductive fine particles of the present invention includes a conductive material for a liquid crystal display element (conductive spacer and composition thereof).

  The anisotropic conductive material is produced by dispersing the conductive fine particles of the present invention in an insulating binder resin to obtain a desired form. Of course, the insulating binder resin and the conductive fine particles May be used separately to connect between substrates or between electrode terminals. The binder resin is not particularly limited, and is, for example, a thermoplastic resin such as an acrylic resin, an ethylene-vinyl acetate resin, a styrene-butadiene block copolymer; a monomer or oligomer having a glycidyl group, and a curing agent such as isocyanate. Examples thereof include a curable resin composition that is cured by reaction and a curable resin composition that is cured by light and heat.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. All of which are within the scope of the present invention.
1. Evaluation method 1-1. Number average particle size, coefficient of variation (CV value)
<Resin particles>
Measure the particle size of 30000 particles with a particle size distribution analyzer (“Coulter Multisizer III type”, manufactured by Beckman Coulter, Inc.) to obtain the number average particle size and the standard deviation of the particle size. CV value (coefficient of variation) was calculated.
Variation coefficient of particles (%) = 100 × (standard deviation of particle diameter / number average particle diameter)
<Conductive fine particles>
Using a flow type particle image analyzer (manufactured by Sysmex Corporation, “FPIA (registered trademark) -3000”), the particle diameter (μm) of 3000 conductive fine particles was measured, and the number average particle diameter was determined.

1-2. Conductive metal layer thickness Using a flow type particle image analyzer ("FPIA (registered trademark) -3000" manufactured by Sysmex Corporation), particles and conductive metal layer (plating) before forming the conductive metal layer (plating layer) Layer) The number average particle diameter of 3000 particles was measured for each of the formed particles, and the film thickness of the conductive metal layer was calculated from the difference. Specifically, when the conductive metal layer is composed of a nickel plating layer and a low melting point metal layer, the thickness of the nickel plating layer and the thickness of the low melting point metal layer were calculated according to the following formula.
Nickel plating layer thickness (μm) = (Y−X) / 2
X (μm): Number average particle diameter of 3000 resin particles Y (μm): Number average particle diameter of 3000 particles after formation of nickel plating layer Film thickness of low melting point metal layer (μm) = (Z−Y) / 2
Y (μm): number average particle diameter of 3000 particles after forming the nickel plating layer Z (μm): number average particle diameter of 3000 particles after forming the low melting point metal layer

1-3. Initial resistance value 1 part by mass of conductive fine particles, 100 parts by mass of an epoxy resin (manufactured by Mitsubishi Chemical, “JER828”) as a binder resin, a curing agent (“San-Aid (registered trademark) SI-150” manufactured by Sanshin Chemical Co., Ltd.) 2 parts by mass and 100 parts by mass of toluene are added, and further 50 parts by mass of 1 mm zirconia beads are added, and dispersion is performed at 300 rpm for 10 minutes using two stainless steel stirring blades. It was applied onto a release-treated PET film with a bar coater and dried to obtain an anisotropic conductive film.
The obtained anisotropic conductive film was sandwiched between a whole surface aluminum vapor-deposited glass substrate having resistance measurement lines and a polyimide film substrate having a copper pattern formed at a pitch of 30 μm, followed by thermocompression bonding under pressure bonding conditions of 1 MPa and 240 ° C. The resistance value between the electrodes was evaluated in three stages of A, B, and C. The case where the initial resistance value was less than 3Ω was “A”, 3Ω or more and less than 5Ω was “B”, and 5Ω or more was “C”. In addition, the presence or absence of a short circuit was also confirmed.

2. 2. Production of resin particles 2-1. Resin particle No. 1
In a four-necked flask equipped with a condenser, a thermometer, and a dropping port, 1800 parts of ion-exchanged water, 24 parts of 25% aqueous ammonia, and 555 parts of methanol are added, and 3-methacryloxypropyltrimethoxy is added from the dropping port with stirring. Emulsion of polysiloxane particles (polymerizable polysiloxane particles) having a methacryloyl group by adding a mixed solution of 100 parts of silane and 45 parts of methanol and hydrolyzing and condensing 3-methacryloxypropyltrimethoxysilane A liquid was prepared. The number particle average diameter of the polysiloxane particles was 1.25 μm.

  Next, 10 parts of 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd .: “Hytenol (registered trademark) NF-08”) as an emulsifier was dissolved in 400 parts of ion-exchanged water. In the solution, 200 parts of styrene and 200 parts of divinylbenzene (DVB960 manufactured by Nippon Steel Chemical Co., Ltd.) and 2,2′-azobis (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd .: “V-65”) ) A solution in which 4.8 parts were dissolved was added and emulsified and dispersed to prepare an emulsion of monomer components. Two hours after the start of the reaction, the obtained emulsion was added to an emulsion of polysiloxane particles and further stirred. One hour after the addition of the emulsified liquid, the mixed liquid was sampled and observed with a microscope. As a result, it was confirmed that the polysiloxane particles were enlarged by absorbing the monomer.

  Next, 96 parts of a 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ammonium salt and 500 parts of ion-exchanged water were added, and the reaction solution was heated to 65 ° C. under a nitrogen atmosphere and held at 65 ° C. for 2 hours. The radical polymerization of the monomer component was performed. The emulsion after radical polymerization was subjected to solid-liquid separation, and the obtained cake was washed with ion-exchanged water and methanol, and then baked at 230 ° C. for 1 hour in a nitrogen atmosphere. 1 was obtained. This resin particle No. 1 had a number average particle size of 2.50 μm and a coefficient of variation (CV value) of 5.2%.

2-2. Resin particle No. 2-8
The number average particle size of the seed particles was changed as shown in Table 1 by changing the conditions for producing the polysiloxane particles. Next, in the same manner as in Production Example 1, mixing of the emulsified liquid, absorption of the monomer component with respect to the polysiloxane particles, and radical polymerization were performed to obtain resin particle No. 2-4 and 6-8 were obtained. Further, when preparing the emulsion, 200 parts of styrene was changed to 200 parts of 1,6-hexanediol diacrylate, and the mixture of the emulsion and the monomer for the polysiloxane particles were the same as in Production Example 1. Absorption of components and radical polymerization were performed to obtain resin particle No. 5 was obtained.

Production Example 1
Etching treatment process Resin particle no. 1 was immersed in a 10% aqueous sodium hydroxide solution having a liquid temperature of 65 ° C. for 30 minutes for etching treatment.

Electroless plating treatment step Sensitizing is performed by bringing 5 g of the etched resin particles into contact with a tin dichloride solution, and then activating by immersion in a palladium dichloride solution to form a palladium nucleus. It was. Next, 5 g of resin particles carrying a catalyst in 4 L of nickel plating solution having the following composition were dispersed and plated at a liquid temperature of 80 ° C. to form a nickel plating layer on the surface of the substrate particles. The thickness of the nickel plating layer was 0.045 μm.
(Nickel plating solution composition)
Nickel sulfate hexahydrate (30 g / L)
Sodium hypophosphite (10g / L)
Sodium citrate (10 g / L)

Next, the particles on which the nickel plating layer was formed were dispersed in 1 L of the following tin plating solution and plated at a liquid temperature of 50 ° C. to form a tin plating layer. The thickness of the tin plating layer was 0.05 μm. The metal-coated particles thus obtained were washed with pure water and methanol and then dried to obtain conductive fine particles.
(Tin plating solution composition)
Tin dichloride dihydrate (18g / L)
Titanium trichloride (25g / L)
Sodium citrate (50 g / L)
Nitriloacetic acid trisodium monohydrate (35 g / L)
Ethylenediaminetetraacetic acid disodium salt dihydrate (40 g / L)

Production Examples 2-6, 12, 13
Except having changed the resin particle to be used as shown in Table 2, the etching process and the electroless-plating process were performed similarly to manufacture example 1, and the electroconductive fine particle was manufactured.

Production Examples 7 to 11
Etching treatment and electroless plating treatment were performed in the same manner as in Production Example 1 except that the thickness of the tin plating layer was changed as shown in Table 2 by changing the amount of nickel plating particles dispersed in the tin plating solution. Conductive fine particles were produced.

  Table 2 shows the types and evaluation results of the resin particles used for the conductive fine particles obtained in the respective production examples.

In the conductive fine particles of Production Examples 1 to 9, the number average particle diameter is 1.1 μm to 2.8 μm, and the thickness of the low melting point metal layer is 0.005 μm to 0.10 μm. The resistance value was low, there was no short circuit, and the connection reliability was excellent.
In the conductive fine particles of Production Example 10, a short circuit occurred because the film thickness of the low melting point metal layer exceeded 0.10 μm. In the conductive fine particles of Production Example 11, the thickness of the low melting point metal layer was less than 0.005 μm, and the initial resistance value was high. Since the conductive fine particles of Production Example 12 had a number average particle diameter exceeding 2.8 μm, a short circuit occurred. On the other hand, the conductive fine particles of Production Example 13 had a high initial resistance because the number average particle diameter was less than 1.1 μm. The conductive fine particles of Production Example 14 had a high initial resistance value because the conductive metal layer was made of Ni.

  The conductive fine particles of the present invention are suitably used for anisotropic conductive materials such as anisotropic conductive films, anisotropic conductive pastes, anisotropic conductive adhesives, anisotropic conductive inks, and the like.

Claims (4)

Conductive fine particles having a substrate composed of resin particles and at least one conductive metal layer formed on the surface of the substrate,
The number average particle diameter of the conductive fine particles themselves is 1.1 μm to 2.8 μm,
At least one layer of the conductive metal layer has a low melting point metal layer formed of a low melting point metal having a melting point of 400 ° C. or less, and the thickness of the low melting point metal layer is 0.005 μm to 0.10 μm. Conductive fine particles characterized by the above.   The conductive fine particles according to claim 1, wherein the conductive metal layer is a multilayer and the outermost layer is the low-melting-point metal layer.   The conductive fine particles according to claim 1, wherein the low melting point metal is tin or a tin-containing alloy.   The conductive fine particles according to claim 1, wherein the resin particles have a number average particle diameter of 1.0 μm to 2.5 μm.