JP5368760B2 - Insulating coating conductive particles, anisotropic conductive material, and connection structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide insulation coated conductive particles with the insulation particles hardly exfoliated even after a pre-treatment process with severe conditions of adding strong shearing force, and capable of attaining both a sufficiently low resistance value at a connection part and excellent insulation between adjacent circuit electrodes in case of connection of fine circuit electrode members of fine-pitch specifications. <P>SOLUTION: The insulation coated conductive particles are provided with conductive particles with a surface having conductivity, and insulating fine particles adhered on the surface of the conductive particles. The insulating particles have the surface of core particles containing polymer components derived from crosslinking monomers coated with a coating layer containing polymer components derived from crosslinking monomers, with a crosslinking degree of the core particles as defined by a formula (1) below of 7 or more, and a crosslinking degree of the core particles as defined by the formula (1) higher than that of the coating layer as defined by the formula (1). Formula (1): crosslinking degree=polymeric functional group number of crosslinking monomers&times;(mol number of crosslinking monomers/mol number of whole monomers)&times;100. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention makes it difficult for the insulating fine particles to be peeled off even when a pretreatment step under severe conditions in which a strong shearing force is applied, and the resistance of the connection portion is sufficiently low when connecting fine circuit electrode members of fine pitch specifications. The present invention relates to an insulating coated conductive particle capable of achieving both a value and an excellent insulating property between adjacent circuit electrodes.

An anisotropic conductive material in which conductive particles are dispersed in a binder resin is used as a circuit connection material for mounting a liquid crystal driving IC on a glass panel for a liquid crystal display.
With the recent increase in definition of liquid crystal displays, the pitch of bumps, which are electrodes of liquid crystal driving ICs, and metal wirings of flexible printed circuit boards has become narrower, and the area of the electrodes has become smaller. For this reason, in the conventional anisotropic conductive material, since the number of conductive particles interposed between circuit electrodes to be connected is insufficient, there is a problem that the resistance value of the connection portion becomes high.

In order to prevent such problems, it is conceivable to increase the content of conductive particles in the anisotropic conductive material. However, when the content of conductive particles is increased, the insulation between adjacent circuit electrodes may be reduced.
Therefore, in order to reduce the resistance value of the connection portion and ensure the insulation between the adjacent circuit electrodes, the anisotropic conductive material using the insulating coated conductive particles whose surface is coated with an insulator. Has been proposed.

As a method of coating the surface of the conductive particles with an insulator, for example, Patent Document 1 discloses a method in which interfacial polymerization, suspension polymerization, emulsion polymerization, or the like is performed in the presence of conductive particles, and the conductive particles are coated with a resin. Is described.
Patent Document 2 describes a dipping method in which conductive particles are dispersed in a resin solution and then dried.
Patent Documents 3 and 4 describe a method of attaching an insulating resin or insulating fine particles to the surface of conductive particles by a spray drying method or a hybridization method.
In addition, a method of covering the surface of the conductive particles with an insulator by vacuum deposition or the like is conceivable.

However, the methods described in Patent Documents 1 to 4 have a problem that it is difficult to make the thickness of the insulating coating layer constant. For example, in the hybridization methods described in Patent Documents 3 and 4, insulating fine particles serving as a coating layer are attached to the surface of the conductive particles by a physical force. In the hybridization method, the insulating fine particles are adhered to the surface of the conductive particles, the insulating fine particles are melted by frictional heat, or the insulating fine particles are deformed by impact, so that uniform coating is performed. Was difficult.
When conducting conductive connection using coated conductive particles, even if the particle size of the conductive particles is highly controlled, if the thickness of the insulating coating layer is not uniform, the pressure is fixed when fixing between the electrodes by heat or pressure. The connection resistance value is increased evenly.
In addition, in the methods described in Patent Documents 1 to 4, since the contact area between the insulating coating layer and the conductive particles is increased, when used in a device such as a liquid crystal element that is difficult to apply heat or pressure, insulation is performed. There was also a problem that the coating layer was difficult to remove and the connection resistance value increased.

Patent Documents 5 and 6 describe coated conductive particles in which insulating fine particles are weakly adhered to the surface of the conductive particles by electrostatic interaction. According to the methods described in Patent Documents 5 and 6, the thickness of the insulating coating layer can be made uniform to some extent. However, in the coated conductive particles described in Patent Documents 5 and 6, since the bonding force between the insulating fine particles and the conductive particles is caused only by van der Waals force or electrostatic force, the bonding is very weak. For this reason, there is a problem in that the insulating fine particles are peeled off when the coated conductive particles are dispersed in the binder resin or in contact with the adjacent particles, and sufficient insulation cannot be secured.

Patent Document 7 discloses that conductive particles are formed into a single layer by electrically bonding insulating particles to conductive particles having a metal surface via a functional group having a binding property to the metal surface. Insulating coated conductive particles coated with are described. The insulating coated conductive particles described in Patent Document 7 have a constant insulating coating layer thickness, and the insulating fine particles are difficult to peel off when dispersed in a binder resin or by contact with adjacent particles.
However, in recent years, the pitch of metal wiring and the like has become narrower, the area of the electrode has become smaller, and in order to improve the connection reliability in the fine pitch specification, when cleaning and dispersing conductive particles, A pretreatment process under extremely severe conditions such as applying a stronger shear force than before has been required. When the pretreatment process is performed under such severe conditions, the insulating fine particles may be peeled off even with the insulating coated conductive particles described in Patent Document 7.
JP-A-4-362104 JP 62-40183 A JP-A-7-105716 JP 2007-258141 A JP-A-4-259766 Japanese Patent Laid-Open No. 3-112011 International Publication No. 2003/025955 Pamphlet

The present invention makes it difficult for the insulating fine particles to be peeled off even when a pretreatment step under severe conditions in which a strong shearing force is applied, and the resistance of the connection portion is sufficiently low when connecting fine circuit electrode members of fine pitch specifications. An object of the present invention is to provide insulating coated conductive particles capable of satisfying both values and excellent insulation between adjacent circuit electrodes.

The present invention is an insulating coated conductive particle having conductive particles having a conductive surface and insulating fine particles adhering to the surface of the conductive particles,
In the insulating fine particles, the surface of the core particle containing the polymer component derived from the crosslinkable monomer is coated with a coating layer containing the polymer component derived from the crosslinkable monomer,
The degree of cross-linking defined by the following formula (1) of the core particle is 7 or more, and the degree of cross-linking defined by the following formula (1) of the core particle is defined by the following formula (1) of the coating layer. Insulating coated conductive particles having a higher degree of crosslinking.
The present invention is described in detail below.

Crosslinking degree = number of polymerizable functional groups of the crosslinkable monomer
X (number of moles of crosslinkable monomer / number of moles of all monomers) x 100 (1)

The present inventor found that the insulating fine particles peeled off when the pretreatment step under severe conditions for applying a strong shear force was performed. I found out that it took a long time. In order to suppress the swelling of the insulating fine particles, it is conceivable to increase the degree of crosslinking of the insulating fine particles. However, when the degree of crosslinking of the insulating fine particles is increased, the insulating fine particles become harder and the contact area between the conductive particles and the insulating fine particles becomes smaller, and the adhesion force between the conductive particles and the insulating fine particles is reduced. Will become weaker.
The present inventor uses the insulating fine particles in which the surface of the core particle having a high degree of crosslinking is coated with a coating layer having a low degree of crosslinking, so that the insulation can be performed even if a pretreatment step under severe conditions in which a strong shear force is applied. It is found that the conductive fine particles are difficult to peel off, and it is possible to achieve both a sufficiently low resistance value at the connection portion and excellent insulation between adjacent circuit electrodes when connecting fine circuit electrode members with fine pitch specifications. The present invention has been completed.

The insulating coated conductive particles of the present invention have conductive particles whose surfaces are conductive and insulating fine particles attached to the surfaces of the conductive particles.
The conductive particles are not particularly limited as long as the surfaces are conductive particles. For example, vapor deposition, plating, and coating are performed on the surface of conductive metal particles, or base particles formed of an organic compound or an inorganic compound. For example, particles in which a conductive layer is formed by the above, particles in which fine particles of conductive metal adhere to the surface of insulating base particles, and the like can be given. Among them, the conductive particles in which the conductive metal layer is formed on the surface of the substrate particles formed of the resin are formed between the electrodes when the insulating coated conductive particles of the present invention are used as an anisotropic conductive material. This is preferable because it is deformed during the pressure bonding and the bonding area is increased and the connection stability is improved.

Examples of the resin constituting the substrate particles include polyolefins such as polyethylene, polypropylene, polystyrene, polypropylene, polyisobutylene and polybutadiene, acrylic resins such as polymethyl methacrylate and polymethyl acrylate, polyalkylene terephthalate, polysulfone, polycarbonate, Phenolic resins such as polyamide and phenol formaldehyde resin, melamine resins such as melamine formaldehyde resin, benzoguanamine resins such as benzoguanamine formaldehyde resin, urea formaldehyde resin, epoxy resin, (un) saturated polyester resin, polyethylene terephthalate, polysulfone, polyphenylene oxide , Polyacetal, polyimide, polyamideimide, polyetheretherke Emissions, polyether sulfone, and the like. Especially, when using the resin obtained by polymerizing 1 type, or 2 or more types of various polymerizable monomers which have an ethylenically unsaturated group, it is preferable from having easy suitable hardness.

The polymerizable monomer having an ethylenically unsaturated group may be a non-crosslinkable monomer or a crosslinkable monomer.
Examples of the non-crosslinkable monomer include styrene monomers such as styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene, chloromethylstyrene, (meth) acrylic acid, maleic acid, and maleic anhydride. Carboxyl group-containing monomers such as acids, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, cetyl (Meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, ethylene glycol (meth) acrylate, trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate, etc. Oxygen atom-containing (meth) acrylates such as kill (meth) acrylates, 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, polyoxyethylene (meth) acrylate, glycidyl (meth) acrylate, (meta ) Nitrile-containing monomers such as acrylonitrile, vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, vinyl acetate, vinyl butyrate, vinyl laurate, vinyl stearate, vinyl fluoride, vinyl chloride, vinyl propionate, etc. Acid vinyl esters, and unsaturated hydrocarbons such as ethylene, propylene, butylene, methylpentene, isoprene, and butadiene.

Examples of the crosslinkable monomer include tetramethylolmethane tetra (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and dipentaerythritol hexa. Multifunctional (meth) such as (meth) acrylate, dipentaerythritol penta (meth) acrylate, glycerol tri (meth) acrylate, glycerol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate Acrylates, triallyl (iso) cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, etc. Silane-containing monomers such as γ- (meth) acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, vinyltrimethoxysilane, dicarboxylic acids such as phthalic acid, diamines, diallyl phthalate, benzoguanamine, triallyl isocyanate Etc.

The preferable lower limit of the average particle diameter of the substrate particles is 0.5 μm, and the preferable upper limit is 100 μm. When the average particle diameter of the substrate particles is less than 0.5 μm, aggregation is likely to occur when forming the metal layer, and the insulating coated conductive particles produced using the aggregated substrate particles are adjacent to each other. May cause short circuit between electrodes. When the average particle diameter of the substrate particles exceeds 100 μm, the metal layer of the obtained insulating coated conductive particles is likely to be peeled off, and the reliability may be lowered. The more preferable lower limit of the average particle diameter of the substrate particles is 1 μm, and the more preferable upper limit is 20 μm.
The average particle size of the substrate particles can be obtained by statistically processing the particle size measured using an optical microscope, an electron microscope, a coulter counter, or the like.

The coefficient of variation of the average particle diameter of the substrate particles is preferably 10% or less. When the coefficient of variation of the average particle diameter of the substrate particles exceeds 10%, it becomes difficult to arbitrarily control the distance between the opposing electrodes using the obtained insulating coating conductive particles. The coefficient of variation is a percentage (%) of a numerical value obtained by dividing the standard deviation obtained from the particle size distribution by the average particle size.

The preferable lower limit of the 10% K value of the substrate particles is 1000 MPa, and the preferable upper limit is 15000 MPa. If the 10% K value of the substrate particles is less than 1000 MPa, the substrate particles may be destroyed when compressed and deformed, and if it exceeds 15000 MPa, the insulating coated conductive particles may damage the electrode. . The more preferable lower limit of the 10% K value of the substrate particles is 2000 MPa, and the more preferable upper limit is 10,000 MPa.
The above 10% K value is measured by using a micro compression tester (for example, PCT-200 manufactured by Shimadzu Corporation), with a smooth indenter end face of a diamond cylinder having a diameter of 50 μm, a compression speed of 2.6 mN / second, and a maximum. The compression displacement (mm) when compressed under the condition of a test load of 10 g can be measured and determined by the following formula.
K value ^{(N / mm 2) = (} 3 / √2) · F · S -3/2 · R -1/2
F: Load value at 10% compression deformation of particles (N)
S: Compression displacement (mm) in 10% compression deformation of particles
R: radius of particle (mm)

In order to obtain a base particle having a 10% K value satisfying the above conditions, the base particle is formed of a resin obtained by polymerizing the above polymerizable monomer having an ethylenically unsaturated group. Preferably it is. In this case, the proportion of the crosslinkable monomer in the total of the crosslinkable monomer and the non-crosslinkable monomer is more preferably at least 20% by weight.

The recovery rate of the substrate particles is preferably 20% or more. If the recovery rate of the base material particles is less than 20%, the resulting insulation coated conductive particles may not be restored to their original shape even when deformed, and the connection resistance value may increase. The recovery rate of the substrate particles is more preferably 40% or more. In addition, the said recovery rate means the recovery rate of the particle diameter after applying a 9.8 mN load to particle | grains.

The metal is not particularly limited as long as it has conductivity, for example, gold, silver, copper, platinum, zinc, iron, tin, lead, palladium, aluminum, cobalt, indium, nickel, chromium, Examples thereof include metals such as titanium, antimony, bismuth, germanium, cadmium, and silicon, and metal compounds such as ITO and solder.

The metal layer may have a single layer structure or a laminated structure having a plurality of layers. In the case of a laminated structure, the outermost layer is preferably a gold layer, a palladium layer, a nickel layer, or a copper layer, and more preferably a gold layer or a palladium layer. By making the outermost layer a gold layer or a palladium layer, the obtained insulating coated conductive particles have high corrosion resistance and low connection resistance.

The method for forming the conductive metal layer on the surface of the substrate particles formed of the resin is not particularly limited, and examples thereof include known methods such as physical metal vapor deposition and chemical electroless plating. It is done. Of these, the electroless plating method is preferred because of the simplicity of the process.
Examples of the metal layer that can be formed by the electroless plating method include a gold layer, a silver layer, a copper layer, a platinum layer, a palladium layer, a nickel layer, a rhodium layer, a ruthenium layer, a cobalt layer, a tin layer, and an alloy layer thereof. Can be mentioned. In the insulating coated conductive particles of the present invention, it is preferable that the metal layer is formed by electroless nickel plating because a uniform metal layer can be formed at a high density.

A gold layer or a palladium layer may be formed on the surface of the metal layer. The method for forming the gold layer or the palladium layer on the surface of the metal layer is not particularly limited, and examples thereof include known methods such as electroless plating, displacement plating, electroplating, and sputtering.

The preferable lower limit of the thickness of the metal layer is 0.005 μm, and the preferable upper limit is 1 μm. If the thickness of the metal layer is less than 0.005 μm, the conductivity may decrease. If the thickness exceeds 1 μm, the specific gravity of the obtained insulating coated conductive particles may be too high, or the insulating coated conductive particles may be hard. May no longer be hard enough to deform. The more preferable lower limit of the thickness of the metal layer is 0.01 μm, and the more preferable upper limit is 0.3 μm.
Moreover, when forming a gold layer or a palladium layer on the surface of the said metal layer, the minimum with the preferable thickness of a gold layer or a palladium layer is 0.001 micrometer, and a preferable upper limit is 0.5 micrometer. If the thickness of the gold layer or the palladium layer is less than 0.001 μm, it may be difficult to form the gold layer or the palladium layer uniformly, and the effect of improving the corrosion resistance and the connection resistance value may not be expected. Exceeding it is expensive for its effect. The more preferable lower limit of the thickness of the gold layer or the palladium layer is 0.01 μm, and the more preferable upper limit is 0.1 μm.

In the insulating fine particles, the surface of the core particle containing the polymer component derived from the crosslinkable monomer is coated with a coating layer containing the polymer component derived from the crosslinkable monomer.

The lower limit of the degree of crosslinking defined by the above formula (1) of the core particles is 7. When the degree of crosslinking of the core particles is less than 7, the degree of swelling of the insulating fine particles at the time of solvent dispersion increases, and the shear force applied to the insulating fine particles in the pretreatment step such as solvent dispersion under severe conditions increases. Insulating fine particles easily peel off from the conductive particles. A preferred lower limit of the degree of crosslinking of the core particles is 12. A preferred upper limit of the degree of crosslinking of the core particles is 40. When the degree of cross-linking of the core particles exceeds 40, insulating fine particles are difficult to be removed during thermocompression bonding, and the connection resistance value may be increased.

The degree of crosslinking defined by the formula (1) of the core particle is higher than the degree of crosslinking defined by the formula (1) of the coating layer. When the degree of cross-linking of the coating layer is equal to or higher than the degree of cross-linking of the core particles, the contact area between the conductive particles and the insulating fine particles decreases, and the adhesion between the conductive particles and the insulating fine particles decreases. Therefore, the insulating fine particles are easily separated from the conductive particles in the pretreatment step under severe conditions.

The preferable lower limit of the degree of crosslinking defined by the above formula (1) of the coating layer is 2, and the preferable upper limit is 10. If the degree of crosslinking of the coating layer is less than 2, the coating layer dissolves or swells greatly when the solvent is dispersed, which increases the shear force applied to the insulating fine particles in the pretreatment step under severe conditions. Insulating fine particles may be easily peeled off from the conductive particles. In addition, the deformation of the insulating fine particles is large, and the thickness of the coating layer of the obtained insulating coated conductive particles may not be uniform. When the degree of cross-linking of the coating layer exceeds 10, the contact area between the conductive particles and the insulating fine particles becomes small, and the adhesion between the conductive particles and the insulating fine particles may be reduced.

The thickness of the coating layer is preferably 1/50 to 1/4 of the particle diameter of the insulating fine particles. When the thickness of the coating layer is thinner than 1/50 of the particle diameter of the insulating fine particles, the contact area between the conductive particles and the insulating fine particles becomes small, and the fixing force between the conductive particles and the insulating fine particles becomes low. The insulating fine particles may be easily peeled off from the conductive particles in the pretreatment step under severe conditions. When the thickness of the coating layer is thicker than 1/4 of the particle diameter of the insulating fine particles, the degree of swelling at the time of solvent dispersion becomes too large, and the shear force applied to the insulating fine particles in the pretreatment step under severe conditions is large. Therefore, the insulating fine particles may be easily separated from the conductive particles.

The particle diameter of the insulating fine particles varies depending on the particle diameter of the conductive particles and the application of the insulating coated conductive particles, but is preferably 1/10 or less of the particle diameter of the conductive particles. When the particle diameter of the insulating fine particles exceeds 1/10 of the particle diameter of the conductive particles, the particle diameter of the insulating fine particles becomes too large and the effect of insulating coating cannot be expected. In addition, when the particle diameter of the insulating fine particles is 1/10 or less of the particle diameter of the conductive particles, when the insulating coated conductive particles of the present invention are produced by the heteroaggregation method, Insulating fine particles can be adhered to the substrate.

When the insulating coated conductive particles of the present invention are used as an anisotropic conductive material, the preferable lower limit of the particle diameter of the insulating fine particles is 5 nm, and the preferable upper limit is 1000 nm. When the particle diameter of the insulating fine particles is less than 5 nm, the distance between adjacent insulating coated conductive particles becomes smaller than the electron hopping distance, and leakage is likely to occur. When the particle diameter exceeds 1000 nm, it is necessary for thermocompression bonding. Excessive pressure and heat may be too high. The more preferable lower limit of the particle diameter of the insulating fine particles is 10 nm, and the more preferable upper limit is 500 nm.

The insulating coated conductive particles of the present invention may be used in combination with two or more kinds of insulating fine particles having different particle diameters. By using two or more types of insulating fine particles having different particle diameters in combination, small insulating fine particles enter the gaps covered with the large insulating fine particles, and the coating density can be improved. At this time, the particle diameter of the small insulating fine particles is preferably 1/2 or less of the particle diameter of the large insulating fine particles, and the number of small insulating fine particles is 1/4 or less of the number of large insulating fine particles. Preferably there is.

The coefficient of variation of the particle diameter of the insulating fine particles is preferably 20% or less. If the coefficient of variation of the particle size of the insulating fine particles exceeds 20%, the thickness of the coating layer of the obtained insulating coated conductive particles becomes non-uniform, and it is difficult to apply pressure uniformly when thermocompression bonding between electrodes. The connection resistance value may increase.
The particle size distribution of the insulating fine particles can be measured by a particle size distribution meter or the like before coating the conductive particles, and can be measured by image analysis of an SEM photograph after coating.

The method for producing the insulating fine particles is not particularly limited. For example, the core particles are produced by a conventionally known method such as suspension polymerization using a raw material monomer, a crosslinking agent, and a polymerization initiator, and then subsequently. And a method of forming a coating layer on the surface of the core particles by introducing a monomer, a crosslinking agent, or the like as a raw material.
The degree of cross-linking of the resin constituting the core particles and the coating layer is determined by selecting the number of polymerizable functional groups of the cross-linkable monomer, the blending ratio of the cross-linkable monomer in the whole monomer as a raw material, and the like. It can be adjusted easily.

Any non-crosslinkable monomer or crosslinkable monomer can be used as the polymer as a raw material for the resin constituting the core particles and the coating layer. As these non-crosslinkable monomers and crosslinkable monomers, those described above can be used.
In addition, when resin which comprises the said core particle and a coating layer is a (meth) acrylic resin, a crosslinkable monomer means the monomer which has two or more (meth) acryl groups.

The polymer as a raw material for the resin constituting the core particles and the coating layer preferably contains a polymerizable monomer having a positive charge. By using a polymerizable monomer having a positive charge, the insulating fine particles have a positive charge. Such insulating fine particles having a positive charge can be bonded to the conductive particles using a heteroaggregation method described later. In addition, since the insulating fine particles repel each other, aggregation of the insulating fine particles can be suppressed, and a single coating layer can be formed. That is, when the insulating fine particles are positively charged, the insulating fine particles adhere to the conductive particles in a single layer. Further, when such a positive charge is due to an ammonium group or a sulfonium group, it acts as a functional group (A) having a binding property to the conductive particles described later, and the insulating fine particles directly adhere to the surface of the conductive particles. It becomes easier to form chemical bonds with metals.

Examples of the positively charged polymerizable monomer include N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropyl acrylamide, N, N, N-trimethyl-N-2-methacryloyloxyethylammonium chloride, and the like. And a monomer having a sulfonium group such as phenyldimethylsulfonium methylsulfate methacrylate.

As the polymerizable initiator, a conventionally known polymerization initiator can be used. In particular, when a radical initiator having a positive charge is used, a positive charge can be imparted to the resulting insulating fine particles.
Examples of the radical initiator having a positive charge 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.

In the insulating coated conductive particles of the present invention, the insulating fine particles are attached to the surface of the conductive particles.
The insulating fine particles preferably cover the conductive particles with a single layer. When the coating layer is a single layer, the thickness of the coating layer can be made uniform.
It is preferable that the insulating fine particles partially cover the surface of the conductive particles by chemically bonding via the functional group (A) having a binding property to the conductive particles.

The functional group (A) is not particularly limited as long as it is a group capable of forming an ionic bond, a covalent bond, or a coordinate bond with a metal. For example, a silane group, a silanol group, a carboxyl group, an amino group, an ammonium group, a nitro group, Examples include a hydroxyl group, a carbonyl group, a thiol group, a sulfonic acid group, a sulfonium group, a boric acid group, an oxazoline group, a pyrrolidone group, a phosphoric acid group, and a nitrile group. Of these, a functional group capable of coordinate bonding is preferable, and a functional group having an S atom, an N atom, or a P atom is preferably used. For example, when the metal is gold, it is preferably a functional group having an S atom that forms a coordinate bond with gold, particularly a thiol group or a sulfide group.

The method for chemically bonding the conductive particles and the insulating fine particles using the functional group (A) is not particularly limited. For example, 1) the insulating fine particles having the functional group (A) on the surface thereof are provided on the surface of the conductive particles. 2) A compound having a functional group (A) and a reactive functional group (B) is introduced onto the surface of the conductive particles, and then the reactive functional group (B) is reacted by one or more stages. And a method of reacting and bonding the insulating fine particles.

In the method 1), the method for producing the insulating fine particles having the functional group (A) on the surface is not particularly limited. For example, a polymerizable monomer having the functional group (A) is used as a raw material for the insulating fine particles. A method used as one, a method of introducing a functional group (A) into the surface of the insulating fine particles by chemical bonding, a method of chemically treating the surface of the insulating fine particles to modify the functional group (A), an insulating property, Examples thereof include a method of modifying the surface of the fine particles into a functional group (A) with plasma or the like.

As the method of 2), for example, a functional group (A) and a reactive functional group (B) such as a hydroxyl group, a carboxyl group, an amino group, an epoxy group, a silyl group, a silanol group, and an isocyanate group are contained in the same molecule. Examples thereof include a method of reacting a compound having a functional group with conductive particles and then reacting insulating fine particles having a functional group covalently bonded to the reactive functional group (B) on the surface. Examples of such a compound having a functional group (A) and a reactive functional group (B) in the same molecule include 2-aminoethanethiol and p-aminothiophenol. If 2-aminoethanethiol is used, 2-aminoethanethiol is bonded to the surface of the conductive particle via an SH group, and an insulating fine particle having, for example, an epoxy group or a carboxyl group on the surface is reacted with one amino group. By doing so, it is possible to bond the conductive particles and the insulating fine particles.

The insulating fine particles preferably have 10 to 20% of the surface area in contact with the surface of the conductive particles. When the surface area where the insulating fine particles and the conductive particles are in contact is less than 10%, the adhesion between the insulating fine particles and the conductive particles is weak, and the insulating fine particles are peeled off in the pretreatment step under severe conditions. If it exceeds 20%, the deformation of the insulating fine particles is large, and the thickness of the coating layer of the obtained insulating coated conductive particles may be non-uniform.

The preferable lower limit of the coverage of the insulating fine particles, that is, the area of the portion covered with the insulating fine particles in the entire surface area of the conductive particles is 5%, and the preferable upper limit is 50%. When the coverage of the insulating fine particles is less than 5%, insulation between adjacent insulating coated conductive particles may be insufficient. When the coverage of the insulating fine particles exceeds 50%, when used as an anisotropic conductive material, it may be necessary to apply heat or pressure more than necessary to eliminate the insulating fine particles and ensure conduction. In some cases, the insulating fine particles between the conductive particles and the electrodes cannot be excluded and there is a high risk that the conductive particles cannot be conducted.

The method for producing the insulating coated conductive particles of the present invention is not particularly limited as long as the insulating fine particles are brought into contact with and chemically bonded to the surface of the conductive particles. For example, the step 1 of aggregating the insulating fine particles on the conductive particles by van der Waals force or electrostatic interaction, and the step 2 of chemically bonding the conductive particles and the insulating fine particles at least in an organic solvent or water. And the like.

The method of aggregating in the step 1 is a method called heteroaggregation method. If the hetero-aggregation method is used, the chemical reaction between the conductive particles and the insulating fine particles takes place quickly and reliably due to the solvent effect, so there is no need for more pressure than necessary and the temperature of the entire system can be easily controlled. Therefore, the insulating fine particles are not easily deformed by heat.
The organic solvent used in step 1 is not particularly limited as long as it is an organic solvent that does not dissolve insulating fine particles.

An anisotropic conductive material containing the insulating coated conductive particles of the present invention and a binder resin is also one aspect of the present invention.
Examples of the anisotropic conductive material of the present invention include anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive adhesive, anisotropic conductive film, and anisotropic conductive sheet.

Although the said binder resin is not specifically limited, A vinyl resin, a thermoplastic resin, curable resin, a thermoplastic block copolymer, an elastomer, etc. are mentioned.
Although the said vinyl resin is not specifically limited, Vinyl acetate resin, an acrylic resin, a styrene resin etc. are mentioned. Although the said thermoplastic resin is not specifically limited, A polyolefin resin, an ethylene-vinyl acetate copolymer, a polyamide resin etc. are mentioned. Although the said curable resin is not specifically limited, An epoxy resin, a urethane resin, a polyimide resin, an unsaturated polyester resin etc. are mentioned. The thermoplastic block copolymer is not particularly limited, but styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, styrene-isoprene. -Hydrogenated product of a styrene block copolymer. These resins may be used alone or in combination of two or more.
The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin, or a moisture curable resin.

The anisotropic conductive material of the present invention includes, for example, a bulking agent, a plasticizer, an adhesive improver, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, a colorant, if necessary. Various additives such as a flame retardant and an organic solvent may be added.

The method for producing the anisotropic conductive material of the present invention is not particularly limited. For example, the insulating coating conductive particles of the present invention are added to the binder resin, and the mixture is uniformly mixed and dispersed. , Anisotropic conductive ink, anisotropic conductive adhesive, and the like. In addition, as a method for producing the anisotropic conductive material of the present invention, the insulating coated conductive particles of the present invention are added to the binder resin and dispersed uniformly or dissolved by heating to release paper or release paper. A method of applying an anisotropic conductive film, an anisotropic conductive sheet, etc. by coating the release treatment surface of a release material such as a mold film so as to have a predetermined thickness and drying or cooling as necessary. Also mentioned. An appropriate manufacturing method can be selected in accordance with the type of anisotropic conductive material.
Moreover, it is good also as an anisotropic conductive material by using separately, without mixing the said binder resin and the insulation coating electroconductive particle of this invention.

A connection structure in which the first circuit board and the second circuit board are conductively connected using the anisotropic conductive material of the present invention is also one aspect of the present invention.
In the connection structure of the present invention, the anisotropic conductive material of the present invention is filled between the pair of circuit boards, thereby electrically connecting the pair of circuit boards.

According to the present invention, the insulating fine particles are difficult to peel off even if a pretreatment step under severe conditions in which a strong shearing force is applied, and when the fine circuit electrode members with fine pitch specifications are connected to each other, the connection portion is sufficiently formed. Insulating coated conductive particles that can achieve both a low resistance value and excellent insulation between adjacent circuit electrodes can be provided.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
(1) Production of conductive particles Sensitizing tetramethylolmethanetetraacrylate-divinylbenzene copolymer resin particles (tetramethylolmethanetetraacrylate 50% by weight: divinylbenzene 50% by weight) having an average particle diameter of 3 μm as base particles. Then, activating was performed to generate Pd nuclei on the surface of the resin particles, thereby forming electroless plating catalyst nuclei. Next, resin particles were immersed in a heated electroless Ni plating bath to form a Ni plating layer. Next, electroless substitution gold plating was performed to obtain conductive particles.
The obtained conductive particles had a Ni plating thickness of 90 nm and a gold plating thickness of 30 nm.

(2) Production of insulating fine particles 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 was charged with 60 mmol methyl methacrylate, 6.7 mmol glycidyl methacrylate, and phenyl methacrylate. 0.003 mmol of dimethylsulfonium methylsulfate, 2 mmol of tetramethylolmethane tetramethacrylate which is a tetrafunctional crosslinkable monomer, and 2,2′-azobis {2- [N- (2-carboxyethyl) amidino as an initiator ] A composition containing 0.005 mmol of propane was weighed in distilled water so that the solid content was 5% by weight. Thereafter, polymerization was started at 60 ° C. in a nitrogen atmosphere while stirring at 200 rpm. Two hours after the start of polymerization, the obtained particles were washed with distilled water to prepare core particles.

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 was added to 30 ml of methyl methacrylate, 3.3 mmol of glycidyl methacrylate, and a difunctional crosslinkable monomer. Contains 1 mmol of ethylene glycol methacrylate, 0.003 mmol of phenyldimethylsulfonium methylsulfate methacrylate, and 0.005 mmol of 2,2′-azobis {2- [N- (2-carboxyethyl) amidino] propane} as an initiator. The composition was weighed in distilled water so that the solid content was 5% by weight, and the total amount of the obtained core particles was added to distilled water. Thereafter, polymerization was started at 60 ° C. in a nitrogen atmosphere while stirring at 200 rpm. Six hours after the start of polymerization, the obtained particles were washed with distilled water and freeze-dried to produce insulating fine particles.
The average particle diameter of the obtained insulating fine particles was 300 nm, and the coefficient of variation of the particle diameter was 10%.

(3) Preparation of insulating coated conductive particles 10 g of the obtained insulating fine particles were dispersed in distilled water to obtain a 10 wt% aqueous dispersion of insulating fine particles. 10 g of conductive particles were dispersed in 500 mL of distilled water, 4 g of a 10 wt% aqueous dispersion of insulating fine particles was added, and the mixture was stirred at room temperature for 6 hours. The mixture was filtered through a 3 μm mesh filter, further washed with methanol, and then dried to obtain insulating coated conductive particles.

(4) Production of anisotropic conductive material Add 5 parts by weight of insulating coated conductive particles to 100 parts by weight of toluene, disperse with an ultrasonic homogenizer for 30 min, and then filter with a 3 μm mesh filter to insulate after dispersion. Coated conductive particles were obtained. 5 parts by weight of the insulating coated conductive particles after dispersion were dispersed in 100 parts by weight of toluene to obtain an insulating coated conductive particle dispersion.

Insulating coated conductive particle dispersion is added to epoxy resin (“Epicoat 828” manufactured by Yuka Shell Epoxy Co., Ltd.) as a binder resin, sufficiently dispersed and mixed using a planetary stirrer, and then dried on a release film. It was applied at a constant thickness so that the subsequent thickness was 7 μm. Thereafter, toluene was volatilized to obtain an adhesive film containing insulating coated conductive particles.
An anisotropic conductive film having a two-layer structure having a thickness of 17 μm is obtained by laminating an adhesive film containing no insulating coating conductive particles at room temperature on the resulting adhesive film containing insulating coating conductive particles. It was.
In addition, the addition amount of the insulating coating conductive particles was set so that the content in the anisotropic conductive film was 300,000 pieces / cm ² .

(Comparative Example 1)
A 1000 mL separable flask equipped with a four-neck separable cover, stirring blade, three-way cock, condenser, and temperature probe was charged with 90 mmol methyl methacrylate, 10 mmol glycidyl methacrylate, and phenyldimethylsulfonium methyl sulfate 0.003 mmol, 2 A composition containing 1 mmol of ethylene glycol dimethacrylate which is a functional crosslinkable monomer and 0.005 mmol of 2,2′-azobis {2- [N- (2-carboxyethyl) amidino] propane} as an initiator The product was weighed into distilled water so that the solid content was 5% by weight. Then, it superposed | polymerized at 60 degreeC by nitrogen atmosphere for 6 hours, stirring at 200 rpm. After completion of the reaction, it was freeze-dried to obtain insulating fine particles.
The average particle diameter of the obtained insulating fine particles was 300 nm, and the coefficient of variation of the particle diameter was 10%.

Insulating coated conductive particles and anisotropic conductive material were produced in the same manner as in Example 1 except that the obtained insulating fine particles were used.

(Comparative Example 2)
A 1000 mL separable flask equipped with a four-neck separable cover, stirring blade, three-way cock, condenser, temperature probe, methyl methacrylate 60 mmol, glycidyl methacrylate 6.7 mmol, phenyldimethylsulfonium methyl sulfate 0.003 mmol Contains 2 mmol of tetramethylol methane tetramethacrylate, a tetrafunctional crosslinkable monomer, and 0.005 mmol of 2,2′-azobis {2- [N- (2-carboxyethyl) amidino] propane} as an initiator The composition was weighed in distilled water so that the final solid content was 5% by weight. Thereafter, polymerization was started at 60 ° C. in a nitrogen atmosphere while stirring at 200 rpm. Two hours after the start of polymerization, the obtained particles were washed with distilled water to prepare core particles.

A 1000 mL separable flask equipped with a four-neck separable cover, stirring blade, three-way cock, condenser, temperature probe, methyl methacrylate 30 mmol, glycidyl methacrylate 3.3 mmol, and phenyldimethylsulfonium methyl sulfate 0.003 mmol And a composition containing 0.002 mmol of 2,2′-azobis {2- [N- (2-carboxyethyl) amidino] propane} as an initiator in distilled water so that the solid content is 5% by weight. The total amount of the obtained core particles was added to distilled water. Thereafter, polymerization was started at 60 ° C. in a nitrogen atmosphere while stirring at 200 rpm. Six hours after the start of polymerization, the obtained particles were washed with distilled water and freeze-dried to produce insulating fine particles.
The average particle diameter of the obtained insulating fine particles was 300 nm, and the coefficient of variation of the particle diameter was 10%.

Insulating coated conductive particles and anisotropic conductive material were produced in the same manner as in Example 1 except that the obtained insulating fine particles were used.

(Evaluation)
The insulating coated conductive particles and anisotropic conductive materials obtained in Example 1 and Comparative Examples 1 and 2 were evaluated by the following methods.
The results are shown in Table 1.

(1) Peeling test of insulating fine particles Arbitrary 50 insulating coated conductive particles were observed using a scanning electron microscope (SEM) immediately after the production. Further, even after preparing the insulating coating conductive fine particle dispersion during the production of the anisotropic conductive material, arbitrary 50 insulating coating conductive particles were observed using SEM. From the results of these SEM observations, the number of insulating fine particles coated immediately after the production of the insulating coated conductive particles was compared with the number of insulating fine particles coated after the dispersion was adjusted. When the ratio of the coating number of the insulating fine particles after the dispersion adjustment was 80% or more with respect to the coating number of the insulating fine particles immediately after the production of the insulating coated conductive particles was 80% or more, it was “◯”, and was 50% or more and less than 80%. The case where it was less than 50% was evaluated as “X”. In SEM observation, the total number of insulating fine particles observed was defined as the coating number.

(2) Insulation test between adjacent electrodes An anisotropic conductive film cut to a size of 4 × 18 mm was formed from the comb-shaped pattern shown in FIG. 1 (800 lines, overlapping portion length 1 mm, line width 10 μm). A silicon wafer substrate having a line interval of 10 μm and a line height of 15 μm), sandwiched between 2 × 12.5 mm flat glass with a thickness of 1 mm, and heated at 150 ° C. for 30 minutes under a pressure of 20 N (Condition 1) Then, after thermocompression bonding was performed by heating at 200 ° C. for 30 seconds (condition 2) under a pressure of 200 N, the resistance value between adjacent electrodes was measured. Among the tests conducted 20 times, the case where the resistance value was 10 ⁸ Ω or more was 16 times or more, “◯”, and the case where the resistance value was 10 times or more and less than 16 times was “△”, 10 The case where it was less than times was evaluated as “×”.

(3) Vertical conduction test One side of a glass substrate (width 1 cm, length 2.5 cm) having an ITO electrode (width 100 μm, height 0.2 μm, length 2 cm) is provided with an anisotropic conductive film 5 × 5 mm. The glass substrate having the same ITO electrode was aligned and pasted so that the electrodes overlap each other. The glass substrate bonding part was thermocompression-bonded by heating at 150 ° C. for 30 minutes under 20N pressure (condition 1) and by heating at 200N for 30 seconds at 200 ° C (condition 2). It was measured. When the number of times that the resistance value was 5Ω or less was 16 times or more in the 20 times of the test, “◯” when the number of times the resistance value was 10 times or less and “△” when the number was 10 times or less and less than 10 times Was evaluated as “×”.

According to the present invention, the insulating fine particles are difficult to peel off even if a pretreatment step under severe conditions in which a strong shearing force is applied, and when the fine circuit electrode members with fine pitch specifications are connected to each other, the connection portion is sufficiently formed. Insulating coated conductive particles that can achieve both a low resistance value and excellent insulation between adjacent circuit electrodes can be provided.

It is a schematic diagram which shows the comb-shaped pattern used in the insulation test between the adjacent electrodes of an Example.

Claims (4)

The surface of the conductive particles is partially covered by chemically bonding to the conductive particles having a conductive surface through the functional group (A) having a binding property to the conductive particles. Insulating coated conductive particles having insulating fine particles,
In the insulating fine particles, the surface of the core particle containing the polymer component derived from the crosslinkable monomer is coated with a coating layer containing the polymer component derived from the crosslinkable monomer,
The degree of cross-linking defined by the following formula (1) of the core particle is 7 or more, and the degree of cross-linking defined by the following formula (1) of the core particle is defined by the following formula (1) of the coating layer. Insulating coated conductive particles characterized in that the degree of cross-linking is higher.
Crosslinking degree = number of polymerizable functional groups of the crosslinkable monomer
X (number of moles of crosslinkable monomer / number of moles of all monomers) x 100 (1) The insulating coated conductive particles according to claim 1, wherein the conductive particles are coated with a single layer by insulating fine particles. An anisotropic conductive material comprising the insulating coated conductive particles according to claim 1 and a binder resin. A connection structure in which the first circuit board and the second circuit board are conductively connected using the anisotropic conductive material according to claim 3 .

Images