JP2013251099A - Conductive particle and process of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive particle and a process of manufacturing the same, capable of exerting excellent conductivity in a pressure direction and insulation properties in a surface direction when applied to an anisotropic conductive adhesive and capable of being downsized.SOLUTION: The conductive particle includes a mother particle having conductivity, a plurality of child particles disposed at an outside of the mother particle and having insulation properties, and a first polymer adhered to a surface of a child particle and having molecular mass of 500 or over.

Description

  The present invention relates to conductive particles and a method for producing the same.

  As a method for electrically connecting circuit boards or IC chips or electronic components to a circuit board, a method using an adhesive or an anisotropic conductive adhesive in which conductive particles are dispersed is known. Such a connection method is remarkably developed in the liquid crystal field. For example, a method of mounting a liquid crystal driving IC on a glass panel for liquid crystal display can be broadly classified into two types: COG (Chip-on-Glass) mounting and COF (Chip-on-Flex) mounting.

  Among these, in COG mounting, the liquid crystal driving IC is directly bonded to the glass panel using an anisotropic conductive adhesive containing conductive particles. On the other hand, in COF mounting, a liquid crystal driving IC is bonded to a flexible tape having metal wiring, and these are bonded to a glass panel using an anisotropic conductive adhesive containing conductive particles. Note that the anisotropy here refers to conduction in the direction of pressurization (hereinafter referred to as “pressurization direction”) when pressurization is performed for adhesion, while being substantially orthogonal to the pressurization direction. The direction (hereinafter referred to as “plane direction”) means the property of maintaining insulation. Since the anisotropic conductive adhesive can exhibit such properties, it can conduct between opposing circuits and terminals, and can insulate between circuits provided on the same substrate or the like.

  As conductive particles used for the anisotropic conductive adhesive, particles obtained by applying nickel plating, nickel / gold plating, nickel / palladium plating, or the like to the outside of plastic particles are known. In addition, a conductive particle having a protrusion on the surface of nickel plating for improving conductivity is also known. As a method for forming such protrusions, Patent Document 1 discloses a method in which nickel particles are used as a core material and nickel plating is performed thereon. In addition, Patent Document 2 discloses a method of forming a roughened shape on the surface using abnormal deposition of plating.

  By the way, with recent high definition of liquid crystal display, gold bumps, which are circuit electrodes of a liquid crystal driving IC, are narrowed in pitch and area. Therefore, when conducting adhesion using an anisotropic conductive adhesive, if conductive particles in the anisotropic conductive adhesive flow into adjacent circuit electrodes, a short circuit occurs between adjacent circuit electrodes. Problems are likely to arise. In particular, the tendency is remarkable in COG mounting.

In addition, when conductive particles flow between adjacent circuit electrodes, the number of conductive particles arranged between the gold bump and the glass panel decreases, and the connection resistance between the facing circuit electrodes increases. Therefore, there is a problem that connection failure is likely to occur. In particular, in recent years, in order to cope with the narrowing of the pitch and the area of the gold bump, 20,000 particles / mm ² or more are introduced per unit area, and this tendency tends to become remarkable.

  Therefore, as a method for solving these problems, Patent Document 3 discloses that an insulating adhesive is formed on at least one surface of an anisotropic conductive adhesive, thereby preventing deterioration in bonding quality in COG mounting or COG mounting. In addition, Patent Document 4 discloses a method in which the entire surface of conductive particles is covered with an insulating film.

JP 2007-324138 A JP 2000-243132 A JP-A-8-279371 Japanese Patent No. 2779409

However, in the method of forming an insulating adhesive on one side of the anisotropic conductive adhesive as described above, a stable connection resistance is obtained when the bump area is relatively small (for example, less than 3000 μm ² ). For this reason, when increasing the number of conductive particles, it tends to be difficult to ensure sufficient insulation between adjacent circuit electrodes. In addition, the method of covering the entire surface of the conductive particles with an insulating coating has a problem that the conductivity tends to be low although high insulating properties can be obtained.

  In addition, in the conventional anisotropic conductive adhesive, even if the number of conductive particles is increased from the viewpoint of obtaining good conductivity, the conductive particles are difficult to get on the bumps due to the resin flowing at the time of pressure bonding, and the conductivity as expected There was also a problem that it could not be obtained. Therefore, when increasing the number of conductive particles, it is important from the viewpoint of improving both good conductivity and insulation that the conductive particles do not move as much as possible at the time of pressure bonding.

  Furthermore, a method of covering the surface of the conductive particles with the child particles having an insulating property is also known, but this method tends to improve the balance between the initial insulating property and the electrical conductivity. However, this method tends to be difficult to apply as the diameter of the conductive particles decreases or as the particle diameter of the insulating child particles increases. In particular, in recent years, in order to cope with the narrow pitch of gold bumps, it is necessary to reduce the diameter of the conductive particles and the diameter of the insulating child particles, and this tendency is remarkable. Furthermore, as a method for producing conductive particles whose surfaces are coated with insulating child particles, a method based on heteroaggregation is known, but in that case, since the bonding force between the insulating child particles and the conductive particles is weak, Problems such as child particles falling off the conductive particles in a film or solvent are likely to occur.

  Therefore, the present invention has been made in view of the circumstances of the above-described prior art, and exhibits excellent conductivity in the pressing direction and insulation in the surface direction when applied to an anisotropic conductive adhesive. It is an object to provide a conductive particle that can be reduced in diameter and a method for producing the same.

  In order to achieve the above object, the conductive particles of the present invention include conductive mother particles, a plurality of insulating child particles arranged outside the mother particles, and a molecular weight attached to the surface of the child particles. And 500 or more first polymers.

  Since the conductive particles of the present invention have a configuration in which the insulating child particles are arranged outside the conductive mother particles, the anisotropic conductive adhesive using the conductive particles has a surface. It is possible to satisfactorily obtain the conductivity in the pressing direction while sufficiently maintaining the insulation in the direction. Further, in the conductive particles of the present invention, the dispersibility of the conductive particles in the anisotropic conductive adhesive is caused by the adhesion of the first polymer having a molecular weight of 500 or more to the surface of the insulating child particles. In addition, the adhesion between the mother particles and the child particles is improved, and the above-described effects can be obtained well even if the conductive particles are made smaller as a whole while the mother particles are made smaller and the child particles are made larger in diameter. be able to.

  The conductive particles of the present invention preferably further include a second polymer having a molecular weight of 500 or more attached to the surface of the mother particle. Thereby, the adhesiveness between the mother particles and the child particles is further improved, and the above-described effects can be obtained better.

  The first polymer is preferably a silicone oligomer. The first polymer preferably has a glycidyl group. When the first polymer has these characteristics, the dispersibility of the conductive particles of the present invention is improved, and the adhesion between the mother particles and the child particles tends to be further improved. is there.

  Moreover, it is preferable that a 2nd polymer has an amino group. The effect of the present invention is that when the mother particles have the amino group-containing second polymer attached to the surface, the adhesion with the first polymer attached to the surface of the child particles is further improved. Can be obtained more satisfactorily.

  In the conductive particles of the present invention, the particle diameter of the child particles is preferably 100 nm or more and 500 nm. Moreover, it is preferable that the particle diameter of a mother particle is 3.0 micrometers or less. Conductive particles satisfying these conditions have a small particle size as a whole, which is advantageous when connecting a liquid crystal driving IC having bumps with a narrow pitch and a small area. As described above, the conductive particles of the present invention have such a structure that the child particles adhere to the surface of the mother particles and the first polymer having a molecular weight of 500 or more adheres to the surface of the child particles. Even if relatively large child particles adhere to the mother particles as compared with the conventional particles, the adhesion between them is good.

  In addition, the child particles preferably have a silanol group. Since the child particles having a silanol group on the surface can have even better adhesion with the first polymer having a molecular weight of 500 or more attached to the surface, in the conductive particles including such child particles, There is a tendency that the adhesion between the mother particles and the child particles becomes even better.

  In the case where a second polymer having a molecular weight of 500 or more is attached to the surface of the mother particle, there is a chemical bond between the second polymer and the first polymer attached to the surface of the child particle. Preferably it has occurred. Thereby, since the adhesiveness between the mother particles and the child particles in the conductive particles becomes extremely good, the effect according to the present invention is further easily obtained.

  The method for producing conductive particles according to the present invention is a method by which the above-described conductive particles of the present invention can be satisfactorily obtained, and the first polymer having a molecular weight of 500 or more is on the outside of the conductive mother particles. And a step of arranging a plurality of insulating child particles attached to the substrate.

  In such a method for producing conductive particles of the present invention, the first polymer is preferably a silicone oligomer. Moreover, it is preferable that a 1st polymer has a glycidyl group. Furthermore, the second polymer preferably has an amino group. When the first or second polymer has these characteristics, the dispersibility of the conductive particles obtained by the production method of the present invention is improved, and the adhesion between the mother particles and the child particles is further improved. Tend to be.

  Moreover, in the manufacturing method of the electroconductive particle of this invention, it is preferable that the particle diameter of a child particle is 100 nm or more and 500 nm. Furthermore, the particle diameter of the mother particles is preferably 3.0 μm or less. As a result, the anisotropic conductive adhesive containing the conductive particles obtained by the production method of the present invention can be successfully applied to the connection of a liquid crystal driving IC having bumps with a narrow pitch and a small area. Become. According to the production method of the present invention, the first polymer is formed on the surface of the child particles even when relatively small child particles are attached to the small mother particles. Since it adheres, the adhesiveness between a mother particle and a child particle can be acquired favorably.

  In addition, the child particles preferably have a silanol group. Since the child particles having a silanol group on the surface can have even better adhesion to the first polymer having a molecular weight of 500 or more attached to the surface, production of conductive particles using such child particles is possible. By conducting the process, conductive particles having good adhesion between the mother particles and the child particles tend to be more easily obtained.

  ADVANTAGE OF THE INVENTION According to this invention, when applied to an anisotropic conductive adhesive, the conductive particle which can exhibit the electrical conductivity of the pressurization direction excellent in the insulation of the surface direction, and can be reduced in diameter, and its manufacturing method Can be provided.

It is a figure which shows typically the cross-sectional structure of the electroconductive particle of suitable embodiment. It is a figure which shows typically the manufacturing process of a connection structure.

  Hereinafter, preferred embodiments of the present invention will be described.

(Conductive particles)
First, the conductive particles according to a preferred embodiment will be described. FIG. 1 is a diagram schematically showing a cross-sectional configuration of conductive particles according to a preferred embodiment. As shown in FIG. 1, the conductive particle 1 of the present embodiment includes a mother particle 2 having conductivity and a plurality of child particles 4 having insulating properties. In the conductive particle 1, the first polymer 6 having a molecular weight of 500 or more is attached to the surface of the child particle 4, and the second polymer 8 having a molecular weight of 500 or more is attached to the surface of the mother particle 2. doing.

  The particle diameter of the mother particle 2 in the conductive particle 1 is preferably smaller than the minimum interval between adjacent electrodes in the electrode of the substrate to be connected by the anisotropic conductive adhesive containing the conductive particle 1. . In addition, when there is a variation in the height of the electrode, it is preferable that the height is larger than the variation in the height.

  From these viewpoints, the particle diameter of the mother particle 2 is preferably in the range of 1 to 10 μm, more preferably in the range of 2.0 to 5 μm, and still more preferably in the range of 2.0 to 3 μm. When the particle diameter of the mother particle 2 is less than 2.0 μm, when there is a variation in the height of the electrode, the number of electrodes that are difficult to connect with the conductive particles 1 increases, and the reliability of conduction may be deteriorated. On the other hand, when the particle diameter of the mother particle 2 exceeds 3.0 μm, the insulation reliability in the surface direction may be deteriorated.

  Here, the particle diameter of the mother particle 2 means the outer diameter of the part of the mother particle 2 forming a particle shape. For example, when the mother particle 2 is composed of a predetermined core particle as described later and a metal coating formed on the surface thereof, the particle size of the combined particle portion is used, and the mother particle 2 has a protruding portion. When it has, it is the particle size of the part which does not contain the projection part. As this particle size, about 100 conductive particles are photographed with a scanning electron microscope (SEM) at a magnification of several thousand to several tens of thousands times, and the particle size of the mother particle 2 obtained by image analysis is applied. be able to. The particle size can be measured by, for example, HITACHI S-4500 (manufactured by Hitachi High-Tech Corporation).

  The mother particle 2 is a particle having conductivity. As the conductive mother particles 2, any of particles consisting only of metal and particles obtained by coating organic or inorganic core particles with metal by a method such as plating can be used. Among these, those obtained by coating organic core particles with metal by plating are preferable. The metal to be coated by plating or the like is not particularly limited, but metals such as gold, silver, copper, platinum, zinc, iron, palladium, nickel, tin, chromium, titanium, aluminum, cobalt, germanium, cadmium, ITO, Examples thereof include metal compounds such as solder. From the viewpoint of corrosion resistance, nickel, palladium, and gold are preferable.

  The metal coating that coats the core particles may have a single layer structure or a laminated structure composed of a plurality of layers. In the case of a single layer structure, the metal film is preferably made of nickel from the viewpoints of cost, conductivity, and corrosion resistance. Furthermore, considering the recent flattening of the glass electrode, the metal coating is preferably nickel plating having protrusions. On the other hand, in the case of a multilayer structure, the metal film preferably has a film made of a noble metal such as gold or palladium on the outside of the film made of nickel.

  The mother particles 2 may have protrusions on the surface. If the mother particle 2 has protrusions, it tends to be fixed to the electrode of the conductive particle 1 and the like, and more excellent conductivity tends to be obtained. The protrusions in the mother particle 2 can be formed on, for example, a metal film formed on the surface of the core particle. In this case, as a method for forming the protrusion, a method using abnormal deposition of plating or a method using a core material may be used.

  Among these methods for forming protrusions, a method using a core material is preferable from the viewpoint of making the shape of the protrusions uniform. Examples of the core material include conductive materials such as nickel, carbon, palladium, and gold, and nonconductive materials such as plastic, silica, and titanium oxide. However, if a ferromagnetic material is used for the core material, magnetic aggregation of the mother particles 2 is likely to occur, and the child particles 4 may not be uniformly attached when the child particles 4 are attached to the surface of the mother particle 2. Therefore, it is preferable to use a nonmagnetic material for the core material. For example, when nickel is used for the core material, the nickel preferably contains phosphorus.

  As a method for forming the protrusion using the core material, for example, a functional group is formed on the surface of the organic core particle, and then a functional group capable of binding to the functional group on the surface of the core particle is formed on the core particle. Examples include a method in which the entire core formed on the surface is adsorbed and then the whole is nickel-plated.

  When forming a metal film by nickel-plating the entire core particles, the nickel plating desirably contains 1.0 wt% or more and 10.0 wt% or less of phosphorus. The phosphorus content here is expressed as (phosphorus content) = (total phosphorus weight) / (total phosphorus weight + total nickel weight). In the case where the protrusion is formed using the core material as described above, when the core material is nickel, it is preferable to satisfy the above conditions including the weight of nickel and phosphorus in the core material.

  When the phosphorus content exceeds 10.0% by weight, the conductivity of the entire metal coating is lowered, and the conduction resistance tends to increase when mounting with an anisotropic conductive adhesive. On the other hand, when the proportion of phosphorus is less than 1.0% by weight, the mother particles 2 are likely to aggregate, and the dispersion tends to increase when the child particles 4 are adhered. Such a phenomenon is remarkable when the particle diameter of the mother particle 2 is 3 μm or less.

Preferably the saturation magnetization of the mother particle 2 is 45 emu / cm ³ or less, more preferably 30 emu / cm ³ or less, still more preferably 10 emu / cm ³ or less, it is 5 emu / cm ³ or less Is more preferable. When the saturation magnetization of the conductive particles exceeds 45 emu / cm ³ and the particle diameter of the mother particles 2 is less than 3 μm, the mother particles 2 tend to be magnetically aggregated, and the child particles 4 tend to be difficult to adhere. .

  The lower the saturation magnetization of the mother particle 2 is, the more difficult it is to agglomerate. However, for example, if too much phosphorus is contained in a metal film formed by nickel plating in order to lower the saturation magnetization, good conductivity may not be obtained. Therefore, it is preferable to set the saturation magnetization of the mother particle 2 so that the conductivity or the like does not decrease excessively. The saturation magnetization can also be lowered by a method of putting a different metal in nickel. According to this method, a decrease in conductivity can be suppressed. For example, a method of adding a few percent of a metal having no ion migration such as palladium to nickel is preferable.

  When the mother particle 2 has protrusions, the size of the protrusions is preferably in the range of 30 nm to 300 nm, and more preferably in the range of 50 to 200 nm. Here, the size of the protrusion means the particle diameter when the protrusion is regarded as a sphere. If the size of the protrusion is too large, the probability of a short circuit between adjacent circuits may increase, and if it is too small, sufficient conductivity may not be obtained. From the viewpoint of achieving both favorable conductivity in the pressing direction and insulation in the planar direction, it is preferable that the protrusions cover 5 to 60% of the surface area of the mother particle 2.

  Examples of the method for forming the metal film on the core particles include electroless plating, displacement plating, electroplating, and sputtering. Of these, electroless copper plating is an excellent method in that it is low in cost, simple and easy to control the thickness.

  Although the thickness of a metal film is not specifically limited, The range of 0.001-1.0 micrometer is preferable and the range of 0.005-0.3 micrometer is more preferable. When the thickness of the metal coating is less than 0.001 μm, poor conduction is likely to occur when mounting with an anisotropic conductive adhesive. On the other hand, when it exceeds 1.0 μm, it is not preferable in terms of cost.

  The material for the organic core particles is not particularly limited, and examples thereof include acrylic resins such as polymethyl methacrylate and polymethyl acrylate, and polyolefin resins such as polyethylene, polypropylene, polyisobutylene, and polybutadiene.

  The child particles 4 in the conductive particles 1 are particles having insulating properties. As the child particles 4, organic fine particles, inorganic oxide fine particles, and organic-inorganic hybrid particles are preferable. Among them, the organic fine particles are easily soluble in a solvent and may not be highly stable against physical impact. On the other hand, the inorganic oxide fine particles have low flexibility and tend to reduce the conductivity of the conductive particles 1. Therefore, for example, the child particles 4 preferably have a structure in which organic fine particles are covered with inorganic fine particles. Such child particles 4 have a good characteristic that they are flexible but hardly dissolved in a solvent.

  Examples of the organic fine particles include fine particles made of polyolefin resins such as polyethylene, polypropylene, and polybutadiene, acrylic resins such as polymethyl methacrylate, epoxy resins, and polyimide resins. Examples of methods for producing these organic fine particles include soap-free and precipitation polymerization.

As the inorganic oxide fine particles, fine particles made of an oxide containing each element of silicon, aluminum, zirconium, titanium, niobium, zinc, tin, cerium, and magnesium are preferable. Moreover, these oxides may be included in combination of two or more. Of these, water-dispersed colloidal silica (SiO ₂ ) is preferable because of its excellent insulating properties and easy particle size control. Examples of such commercially available inorganic oxide fine particles include Snowtex, Snowtex UP (manufactured by Nissan Chemical Industries, Ltd.), Quatron PL series (manufactured by Fuso Chemical Industries, Ltd.) and the like.

  From the viewpoint of obtaining good insulation reliability in the plane direction when using an anisotropic conductive adhesive, the inorganic oxide fine particles are preferably produced by hydrolysis reaction of metal alkoxide, so-called sol-gel method. . When producing fine particles by the sol-gel method, in addition to tetraethoxysilane or tetramethoxysilane, a bifunctional or trifunctional silane having a methyl group or a phenyl group is added to produce silicone fine particles which are inorganic oxide fine particles. You can also According to this method, the degree of crosslinking and the functional group can be changed, and thereby flexibility and hydrophobicity can be controlled.

  Furthermore, examples of the organic / inorganic hybrid particles include those obtained by copolymerization of an acrylic resin and a polyfunctional alkoxysilane. Even with such organic-inorganic hybrid particles, there is a tendency that the child particles 4 having moderate characteristics of the organic fine particles and the inorganic oxide fine particles can be easily obtained. The organic-inorganic hybrid particles exhibit more inorganic particle characteristics when the proportion of the polyfunctional alkoxysilane in the raw material is increased, and the organic particles properties when the proportion of the acrylic resin is increased. Therefore, the organic-inorganic hybrid particles can easily obtain desired characteristics by appropriately adjusting the ratio of raw materials at the time of production. Examples of the method for synthesizing the organic / inorganic hybrid particles include dispersion polymerization and precipitation polymerization.

  As the child particle 4, one having a core-shell structure in which a core particle and a coating layer covering the core particle are formed can be applied. As the child particles 4 having such a core-shell structure, those having a flexible inner side and a hard outer side are preferable. Examples thereof include those having the above organic fine particles as core particles and provided with a coating layer made of silicone or silica crosslinked on the outside thereof. The child particles 4 having such a structure have characteristics of being flexible and excellent in solvent resistance.

  The child particles 4 preferably have a reactive functional group such as a hydroxyl group, a silanol group, a carboxyl group, or an amino group on the surface, and more preferably a silanol group. Since the child particles 4 have these functional groups on the surface, the reactivity with the first polymer 6 to be described later is improved, and the adhesion between the child particles 4 and the first polymer 6 is improved. The adhesion between the mother particle 2 and the child particle 4 tends to be improved.

  As the child particle 4 having these functional groups on the surface, the child particle 4 itself is formed by a compound having these functional groups, or the coating layer in the core-shell structure is formed by a compound having these functional groups. What is composed is mentioned. For example, the child particle 4 having a core-shell structure in which the coating layer made of silicone or silica as described above is provided on the surface of a predetermined core particle becomes the child particle 4 having a silanol group on the surface.

  The child particles 4 preferably have a particle size measured by a specific surface area conversion method by the BET method or a small-angle X-ray scattering method of 20 nm to 500 nm, more preferably 100 nm to 500 nm, and 200 nm to 400 nm. More preferably. When the particle size of the child particles 4 is smaller than the preferred range, the insulating property by the child particles 4 attached to the mother particles 2 is not exhibited as compared with the case where the particle size is within the range, and an anisotropic conductive adhesive is used. When joining, it is easy to cause a short circuit in part. On the other hand, when larger than it, when joining using anisotropic conductive adhesive, it exists in the tendency for the electroconductivity of a pressurization direction to fall. In addition, when the mother particle 2 has a protrusion on the surface, the size of the child particle 4 is desirably larger than the protrusion.

  In the conductive particle 1, the first polymer 6 having a molecular weight of 500 or more is attached to the surface of the child particle 4. Here, in the present specification, the polymer means a compound in which at least two certain structural units are bonded, and includes compounds usually classified into oligomers and polymers. Thus, the dispersibility in the anisotropic conductive adhesive of the conductive particles 1 becomes good because the first polymer 6 having a molecular weight of 500 or more adheres to the surface of the child particles 4. A strong bond is generated between the functional group of the first polymer 6 and the functional group of the second polymer 8 attached to the mother particle 2 or the surface thereof. Adhesiveness between the particles 2 and the child particles 4 is improved. As a result, in the conductive particle 1, it is possible to reduce the diameter of the mother particle 2 and increase the diameter of the child particle 4.

  The first polymer 6 preferably has a functional group capable of causing a reaction with the functional group of the mother particle 2 or the second polymer 8 attached to the surface thereof as a functional group. Specifically, the first polymer 6 is preferably one having a glycidyl group, a carboxyl group, an isocyanate group, or the like. The functional group in the first polymer 6 can be selected according to the type of the functional group that the polymer 8 attached to the mother particle 2 or the surface thereof has, but among those described above, the glycidyl group is More preferred.

  Examples of the first polymer 6 include silicone oligomers. As the first polymer 6, a silicone oligomer having a glycidyl group is particularly preferable.

  The molecular weight of the 1st polymer 6 is 500 or more, it is preferable in it being 500-10000, and it is more preferable in it being 1000-4000. The more the first polymer 6 has a suitable molecular weight, the better the dispersibility of the conductive particles 1 in the anisotropic conductive adhesive and the better the adhesion between the mother particles 2 and the child particles 4. .

  Since the first polymer 6 is attached to the surface of the child particle 4, the child particle 4 is in a state of being at least partially covered with the first polymer 6. If the coverage of the child particles 4 by the first polymer 6 is too high, the conductivity in the pressurizing direction may be lowered when the conductive particles 1 are used as an anisotropic conductive adhesive. On the other hand, when this coverage is too small, when the conductive particles 1 are used as an anisotropic conductive adhesive, the insulation in the surface direction may be lowered.

  Therefore, the coverage of the child particles 4 with the first polymer 6 is preferably in the range of 10% to 50%, and more preferably in the range of 20 to 50%. The coverage is determined by, for example, observing the child particles 4 to which the first polymer 6 is adhered by SEM image analysis, and the surface area (A) of the portion of the child particles 4 covered with the first polymer 6 and the child particles. 4 can be calculated by (A) / (B) × 100%. Further, the variation (C.V.) in the coverage of the child particles 4 by the first polymer 6 is preferably in the range of 0.4 or less, and more preferably 0.3 or less. By satisfying these conditions, the conductivity in the pressing direction by the anisotropic conductive adhesive using the conductive particles 1 and the insulating property in the surface direction tend to be favorably obtained.

  Only one layer of the first polymer 6 may be formed on the surface of the child particle 4, or a plurality of layers may be formed. That is, for example, a plurality of layers made of different types of first polymers 6 may be formed on the surfaces of the child particles 4. However, in the case where the first polymer 6 having a plurality of layers is formed on the surface of the child particle 4, the first polymer 6 is formed on the surface of the child particle 4 because the amount of lamination tends to be difficult to control. It is preferable that only one layer is formed.

  In the conductive particle 1, the second polymer 8 having a molecular weight of 500 or more is attached to the surface of the mother particle 2. However, the second polymer 8 is not necessarily attached to the surface of the base particle 2. For example, when the mother particle 2 itself has a functional group capable of reacting with the functional group of the first polymer 6, the second polymer 8 adheres to the surface of the mother particle 2. Even if it is not, sufficient adhesiveness can be exhibited with the child particle 4 which has the 1st polymer 6 on the surface. Since the mother particle 2 has the second polymer 8 on the surface, it is controlled so that good adhesion between the mother particle 2 and the child particle 4 having the first polymer 6 attached to the surface is obtained. It tends to be easier.

  As the second polymer 8, a functional group capable of reacting with the functional group of the first polymer 6 to form a bond, for example, a functional group that is ionized in an aqueous solution and has a charge, What has in a principal chain or a side chain is preferable. The functional group possessed by the second polymer is preferably a functional group that can be positively charged, such as an amino group.

  As the second polymer 8, a polymer electrolyte having a functional group as described above, for example, a polycation is preferable. As the second polymer 8, polyethyleneimine (PEI), polyallylamine hydrochloride (PAH), polydiallyldimethylammonium chloride (PDDA), polyvinylpyridine (PVP), polylysine, polyacrylamide, and at least one of them And the like. Among these, polyethyleneimine has a high charge density and tends to have a high binding force with the first polymer 6. Since these are both water-soluble or soluble in organic solvents such as alcohol, they can be easily attached to the surface of the mother particle 2 as a solution, for example.

  The polymer electrolyte applied as the second polymer 8 is made of alkali metal (Li, Na, K, Rb, Cs) ions, alkaline earth metals (Ca, Sr, Ba, Ra, Ra) in order to avoid electromigration and corrosion. ) Ions, halide ions (fluorine ions, chloride ions, bromine ions, iodine ions) and the like are preferable.

  The molecular weight of the second polymer 8 varies depending on the type of polymer electrolyte applied as the second polymer 8, but is preferably 500 or more, and more preferably 500 to 200,000. When the molecular weight of the second polymer 8 is less than 500, the mother particles 2 are dispersed in the solution of the second polymer 8 in a manufacturing method as described later, for example, as compared with the case where the molecular weight is 500 or more. At this time, the dispersibility of the mother particles 2 tends to be insufficient. In that case, when the particle diameter of the mother particle 2 is small (for example, 3.0 μm or less), the mother particle 2 may be excessively aggregated and it may be difficult to produce the conductive particle 1. In particular, when a compound having an amino group is used as the second polymer 8, if the molecular weight is too small, the second polymer 8 tends to be detached from the surface of the mother particle 2, and adhesion by an anisotropic conductive adhesive is performed. When performing, there is a possibility that the curing reaction is inhibited.

  Thus, when the 2nd polymer 8 has adhered to the surface of the mother particle 2, the coverage of the mother particle 2 with the second polymer 8 is the coverage of the child particle 4 with the first polymer 6. It can be obtained in the same way as the rate.

  Since the second polymer 8 is attached to the surface of the mother particle 2, good adhesion between the mother particle 2 and the child particle 2 having the first polymer 6 attached to the surface is obtained. Therefore, the child particles 4 having insulating properties can uniformly adhere to the surface of the mother particles 2 having conductivity. In particular, when the particle diameter of the mother particles 2 is small, the mother particles 2 are likely to be magnetically aggregated in the process of producing the conductive particles 1 and it is difficult to attach the child particles 4 to the surface. Since the dispersibility of the mother particles 2 is good because the second polymer 8 is attached to the surface, the child particles 4 are easily attached. As a result, when the conductive particles 1 are applied to the anisotropic conductive adhesive and bonded, the conductivity in the pressurizing direction can be suitably obtained, and even if the distance between the circuit electrodes is a narrow pitch, the surface Good direction insulation can be obtained.

  As described above, in the conductive particle 1 of the present embodiment, a plurality of child particles 4 having the first polymer 6 adhered to the surface are adhered to the outside of the mother particle 2 having the second polymer 8 adhered to the surface. It has a configuration. Therefore, in the conductive particles 1, at least a part of the surface of the mother particle 2 is covered with the plurality of child particles 4. The coverage of the mother particles 2 with the child particles 4 can also be determined in the same manner as the coverage of the child particles 4 with the first polymer 6.

(Method for producing conductive particles)
Next, the suitable example of the manufacturing method of the electrically-conductive particle 1 of suitable embodiment mentioned above is demonstrated.

  The conductive particles 1 are attached to the outer surfaces of the conductive mother particles 2 directly and / or through a predetermined layer, and the insulating child particles 4 having the first polymer 6 having a molecular weight of 500 or more attached to the surface. It can manufacture through the process of making it. In the present embodiment, an example in which the second polymer 8 is attached on the surface of the mother particle 2 will be described.

  First, as the mother particle 2, particles made of only the metal as described above, or particles obtained by coating an organic or inorganic core particle with a metal by a method such as plating are prepared. The mother particle 2 preferably has a predetermined functional group formed on the surface thereof. According to the mother particle 2 having a predetermined functional group formed on the surface, the second polymer 8 and the child particle 4 can be satisfactorily adhered to the surface of the mother particle 2. For example, a hydroxyl group can form a strong bond with a hydroxyl group, a carboxyl group, an alkoxy group, an alkoxycarbonyl group, an amino group, or a glycidyl group. As a bond between the hydroxyl group and these functional groups, for example, by dehydration condensation A covalent bond and a hydrogen bond are mentioned. Therefore, from the viewpoint of favorably attaching the child particles 4, it is preferable that a hydroxyl group, a carboxyl group, an alkoxy group, an alkoxycarbonyl group, or the like is formed on the surface of the mother particle 2.

  As the aspect of the mother particle 2 having the functional group formed on the surface, the mother particle 2 itself has the functional group on the surface, or the compound having the functional group adheres to the surface of the mother particle 2. And the like. In the latter case, the functional group can be formed on the surface of the mother particle 2 by treating the surface of the mother particle 2 with the compound having the functional group. In particular, from the viewpoint of making aggregation of the mother particles 2 difficult to occur, the following method is preferable.

  For example, when the mother particle 2 has a surface made of gold or palladium, the surface is formed on the surface of the mother particle 2 as described above with a functional group that forms a coordinate bond with gold or palladium. The method of processing with the compound which has both the functional group to form (a hydroxyl group, a carboxyl group, an alkoxy group, an alkoxycarbonyl group, etc.) is mentioned. Examples of the functional group that forms a coordinate bond with gold or palladium include a mercapto group, a sulfide group, and a disulfide group. Examples of the compound having these functional groups include mercaptoacetic acid, 2-mercaptoethanol, methyl mercaptoacetate, mercaptosuccinic acid, thioglycerin, cysteine and the like.

  Further, when the mother particle 2 has a surface made of nickel, both the silanol group and the hydroxyl group that form a strong bond with nickel and the functional group that is formed on the surface of the mother particle 2 are used. And a method of treating with a nitrogen compound having a functional group formed on the surface of the mother particle 2 or the like. Examples of such a compound include carboxybenzotriazole.

  The method of treating the surface of the mother particle 2 with the above compound is not particularly limited as long as the compound can be attached to the surface of the mother particle 2. For example, the above-described method may be performed in an organic solvent such as methanol or ethanol. Examples include a method in which the obtained compounds (mercaptoacetic acid, carboxybenzotriazole, etc.) are dispersed to a concentration of 10 to 100 mmol / L, the mother particles 2 are dispersed in the solution, and then the mother particles 2 are taken out.

  Thus, when a hydroxyl group, a carboxyl group, an alkoxy group, an alkoxycarbonyl group or the like is formed on the surface of the mother particle 2, the overall surface potential (zeta potential) is usually (when the pH is in a neutral region). ) Is negative. On the other hand, the child particle 4 may have a hydroxyl group, a silanol, or a glycidyl group on the surface due to the child particle 4 itself or the first polymer 6 attached to the surface thereof. Is usually negative.

  However, it is usually not easy to attach particles having a negative surface potential to particles having a negative surface potential because they repel. In that case, the above-described second polymer 8 (particularly, polymer electrolyte) is adhered to the surface of the mother particle 2 so that such repulsion does not occur, and the child particle 4 is formed on the surface of the mother particle 2. Can be adhered well.

  For example, the mother particles 2 having the second polymer 8 attached to the surface thereof are dispersed in a solution containing the second polymer 8 (hereinafter referred to as “second polymer solution”). Thereafter, the mother particles 2 to which the second polymer 8 is adhered to the surface can be taken out from the second polymer solution and dried or the like if necessary. The solution containing the second polymer 8 can be obtained by dissolving or dispersing the second polymer 8 in a solvent.

  As described above, the mother particle 2 having the second polymer 8 attached to the surface is obtained, but the child particle 4 having the first polymer 6 attached to the surface can be obtained in the same manner. That is, after the child particles 4 are dispersed in a solution containing the first polymer 6, the child particles 4 having the first polymer 6 attached to the surface are taken out of the solution and dried or the like as necessary. Can be obtained. The solution containing the first polymer 6 can be obtained by dissolving or dispersing the first polymer 6 in a solvent. The solvent is not particularly limited as long as it can dissolve or disperse the first polymer 6.

  The conductive particles 1 can be obtained by adsorbing the child particles 4 with the first polymer 6 attached to the surface to the mother particles 2 with the second polymer 8 attached to the surface as described above. For example, in a solution in which the child particles 4 having the first polymer 6 attached to the surface are dispersed in a predetermined solvent (hereinafter referred to as “child particle dispersion”), the second polymer 8 is formed on the surface. There is a method in which after the adhered mother particles 2 are dispersed, the mother particles 2 to which the child particles 4 adhere to the surface are removed.

  In particular, as a preferred method for producing the conductive particles 1, a method in which the child particles 4 having the second polymer 8 and the first polymer 6 attached to the surface of the mother particle 2 are sequentially attached to the surface of the mother particle 2 is preferable. Specifically, (1) the mother particle 2 having a hydroxyl group, a carboxyl group, an alkoxy group, an alkoxycarbonyl group or the like formed on the surface is dispersed in the second polymer solution, and the second particle is dispersed on the surface of the mother particle 2. A step of rinsing after the polymer 8 is adhered, and (2) the mother particles 2 having the second polymer 8 adhered to the surface are dispersed in the child particle dispersion liquid, and the second polymer 8 After the child particles 4 having the first polymer 6 attached to the surface are attached to the surface of the mother particles 2 to which the particles are attached, the child particles 4 are attached to the surface of the mother particles 2 by performing a rinsing step. Conductive particles 1 can be obtained.

  Such a method is based on a method called a layer-by-layer assembly (G. Decher et al., Thin Solid Films, 210/211, p831 (1992)). In the alternate lamination method, the substrate is alternately immersed in an aqueous solution of a polymer electrolyte (polycation) having a positive charge and an aqueous solution of a polymer electrolyte (polyanion) having a negative charge, and is adsorbed by electrostatic attraction on a substrate. A composite membrane (alternate laminated membrane) is obtained by laminating a combination of the polycation and the polyanion. In such an alternate lamination method, the film grows by attracting the charge of the material formed on the substrate and the material having the opposite charge in the solution by electrostatic attraction, so that the adsorption progresses and the charge grows. When the neutralization of the water occurs, no further adsorption occurs. Therefore, when this adsorption reaches the saturation point, the film thickness does not increase any more.

  It has been reported that such an alternate lamination method can be applied even when fine particles are used. For example, a method of laminating fine particles and a polymer electrolyte by an alternating lamination method using a dispersion of fine particles of silica, titania, and ceria and a solution of a polymer electrolyte having a charge opposite to the surface charge of these fine particles is known. (Lvov et al., Langmuir, Vol. 13, (1997), p6195-6203). According to this method, insulator particles having a negative surface charge and polydiallyldimethylammonium chloride (PDDA) and polyethyleneimine (PEI), which are polycations having the opposite charge, can be alternately stacked. It becomes possible to form a fine particle laminated thin film in which insulator particles and polymer electrolyte are alternately laminated.

  As described above, after the second polymer 8 is attached to the surface of the mother particle 2, and on the surface of the mother particle 2 to which the second polymer 8 is attached, the m first polymer 6 is attached to the surface. After the attached child particles 4 are attached, it is preferable to rinse away the excess second polymer solution and child particle dispersion by rinsing them only with a solvent. For such rinsing, water, alcohol, acetone or the like can be used.

  Moreover, as a 2nd polymer solution used by this method, what melt | dissolved the 2nd polymer 8 in the mixed solvent of water or an organic solvent is mentioned. Examples of the water-soluble organic solvent include methanol, ethanol, propanol, acetone, dimethylformamide, acetonitrile, and the like. The concentration of the second polymer 8 in the solution is preferably about 0.01 to 10% (weight basis). Further, the pH of the second polymer solution is not particularly limited.

  In the method described above, by adjusting the type and molecular weight of the second polymer 8 and the concentration of the second polymer solution, the ratio of the mother particles 2 covered by the child particles 4 (the coating of the child particles 4). Rate) can be controlled moderately.

  For example, when a polymer electrolyte having a high charge density such as polyethyleneimine is used as the second polymer 8, the coverage of the child particles 4 tends to increase. On the other hand, when a polymer electrolyte having a low charge density such as polydiallyldimethylammonium chloride is used as the second polymer 8, the coverage of the child particles 4 tends to be low. Further, when the molecular weight of the second polymer 8 is large, the coverage of the child particles 4 tends to be high, and when the molecular weight of the second polymer 8 is small, the coverage of the child particles 4 tends to be low. is there. Furthermore, when the second polymer solution has a high concentration, the coverage of the child particles 4 tends to increase, and when the second polymer solution has a low concentration, the coverage of the child particles 4 decreases. Tend.

  As described above, the bonding between the mother particles 2 and the child particles 4 can be strengthened by further heating and drying the conductive particles 1 having the child particles 4 attached to the surfaces of the mother particles 2. The reason why the bonding force is improved is that the functional groups of these particles are chemically bonded to each other. The drying temperature is preferably 60 to 200 ° C., and the heating time is preferably in the range of 10 to 180 minutes. When the temperature is lower than 60 ° C or when the heating time is shorter than 10 minutes, the child particles 4 may be easily peeled off from the mother particle 2, and when the temperature is higher than 200 ° C or when the heating time is longer than 180 minutes. If the length is long, the conductive particles 1 may be easily deformed.

  In addition, there exists a possibility that the reliability of the electroconductive particle 1 produced as mentioned above may become inadequate depending on the quantity and kind of surface functional group. Therefore, it is preferable that the conductive particles 1 having such a fear are those in which the surface is further treated with a silicone oligomer and the silicone oligomer is attached to the surface. Such a conductive particle 1 has high insulation reliability even if it has a functional group that may reduce the reliability of the conductive particle 1 at the time when the child particle 4 is attached to the mother particle 2. It will be a thing. Examples of the silicone oligomer used here include those having a hydrophobic functional group such as a methyl group and a phenyl group, and those having a molecular weight of about 500 to 5,000 are preferably used.

(Anisotropic conductive adhesive)
The conductive particles 1 as described above can be used as an anisotropic conductive adhesive by being dispersed in an adhesive.

  As the adhesive in the present embodiment, a mixture of a heat-reactive resin and a curing agent can be used. Especially, as an adhesive agent, the mixture of an epoxy resin and a latent hardener is preferable. Examples of the latent curing agent include imidazole series, hydrazide series, boron trifluoride-amine complex, sulfonium salt, amine imide, polyamine salt, dicyandiamide, and the like. In addition, as the adhesive, a mixture of a radical reactive resin and an organic peroxide or a curable resin that is cured by energy rays such as ultraviolet rays can be applied.

  Epoxy resins include bisphenol-type epoxy resins derived from epichlorohydrin and bisphenol A, F, AD, and the like, epoxy novolac resins derived from epichlorohydrin and phenol novolac and cresol novolac, and naphthalene having a skeleton containing a naphthalene ring Examples thereof include various epoxy compounds having two or more glycidyl groups in one molecule such as epoxy resin, glycidylamine, glycidyl ether, biphenyl, and alicyclic. These can be used alone or in admixture of two or more.

  As these epoxy resins, it is possible to use a high-purity product in which impurity ions (Na +, Cl-, etc.), hydrolyzable chlorine, etc. are reduced to 300 ppm or less, and adhesion is performed using an anisotropic conductive adhesive. This is preferable because it is easy to prevent electromigration.

  In order to reduce the stress after adhesion or to improve the adhesiveness, butadiene rubber, acrylic rubber, styrene-butadiene rubber, silicone rubber or the like can be further mixed into the adhesive.

  Examples of the shape of the anisotropic conductive adhesive include a paste shape and a film shape. In order to obtain a film-like anisotropic conductive adhesive, it is effective to add a thermoplastic resin such as a phenoxy resin, a polyester resin, or a polyamide resin to the adhesive. These thermoplastic resins function as a film-forming polymer and can also relieve stress when the thermoreactive resin is cured. In particular, when these film-forming polymers have a functional group such as a hydroxyl group, the adhesiveness due to the anisotropic conductive adhesive is further improved, which tends to be more preferable.

  For example, an anisotropic conductive adhesive in the form of a film is obtained by dissolving or dispersing an adhesive (adhesive composition) containing an epoxy resin, acrylic rubber, and a latent curing agent in an organic solvent to liquefy the adhesive. It can apply | coat on the base material which has, and can obtain by removing a solvent below the active temperature of a latent hardening | curing agent. At this time, the conductive particles 1 are preferably added when the adhesive is dissolved or dispersed in an organic solvent. As the organic solvent, an aromatic hydrocarbon-based and oxygen-containing mixed solvent is preferable because excellent solubility can be obtained.

  The thickness of the film-like anisotropic conductive adhesive can be determined in consideration of the particle diameter of the conductive particles 1 and the characteristics of the anisotropic conductive adhesive. The film-like anisotropic conductive adhesive preferably has a two-layer structure of a layer containing the conductive particles 1 and a layer not containing the conductive particles 1. When using such a film-like anisotropic conductive adhesive having a two-layer structure, a layer not containing the conductive particles 1 is arranged on the metal bump side, and a layer containing the conductive particles 1 is arranged on the glass side. The conductive particles 1 are captured by the metal bumps with high efficiency.

  From the viewpoint of obtaining such an effect better, the layer containing the conductive particles 1 is preferably as thin as possible. Further, the layer not containing the conductive particles 1 is preferably thicker and has higher fluidity than the layer containing the conductive particles 1. For example, the layer containing the conductive particles 1 has a thickness of 3 to 15 μm, the layer not containing the conductive particles 1 is in the range of 7 to 20 μm, and the layer containing the conductive particles 1 is anisotropically conductive. It is preferable that it is 50 weight% or less of the whole adhesive film.

  Furthermore, the film-like anisotropic conductive adhesive has a thickness of 4 μm or less on the side where the glass or ITO is disposed in addition to the above two-layer structure from the viewpoint of enhancing the adhesion with glass or ITO. It is preferable to have a three-layer structure including a layer not containing conductive particles. It is particularly preferable that such a layer not containing conductive particles has high fluidity.

(Connection structure)
A connection structure can be obtained by connecting a chip or the like to a substrate or the like using the anisotropic conductive adhesive as described above. Hereinafter, an example of a method for manufacturing a connection structure using an anisotropic conductive adhesive will be described with reference to FIG. FIG. 2 is a diagram schematically showing a manufacturing process of the connection structure.

  FIG. 2A is a schematic cross-sectional view showing each arrangement when the chip 10 is connected to the substrate 19 using the anisotropic conductive adhesive 20. The chip 10 has a configuration in which metal bumps 12 are formed on the IC chip 11. The substrate 19 has a configuration in which the electrode 17 is formed on the glass substrate 18. Here, the electrode 17 is an ITO (Indium Tin Oxide) electrode or an IZO (Indium Zinc Oxide) electrode.

  Further, in the anisotropic conductive adhesive 20, the layer containing the conductive particles 1 (conductive particle-containing layer 14) is sandwiched between the pair of layers not containing the conductive particles 1 (conductive particle-free layers 13, 15). It has a three-layer structure. The conductive particle-containing layer 14 is a layer in which the conductive particles 1 are dispersed in the adhesive 16. Here, the conductive particles 1 have the same configuration as the conductive particles 1 shown in FIG. 1, but the first polymer 6 and the second polymer 8 are omitted for convenience of explanation. The adhesive 16 and the conductive particle non-containing layers 13 and 15 are both made of the same adhesive. Examples of the adhesive include those exemplified above.

  As shown in FIG. 2A, in this step, the chip 10 and the substrate 19 are arranged to face each other so that the metal bumps 12 and the electrodes 17 face each other, and a film-like structure having a three-layer structure therebetween. A one-way conductive adhesive 20 is disposed. The anisotropic conductive adhesive 20 is disposed such that the conductive particle non-containing layer 13 faces the chip 10 side and the conductive particle non-containing layer 15 faces the substrate 19 side.

  And the connection structure 100 shown in FIG.2 (b) is obtained by crimping | bonding the chip | tip 10, the anisotropic conductive adhesive 20, and the board | substrate 19 which were arranged in this way to a lamination direction, heating and pressurizing.

  In manufacture of such a connection structure 100, since the conductive particles 1 are easily captured by the metal bumps 12 by the child particles 4 on the surface, the lateral flow is suppressed. As a result, good conductivity in the stacking direction (between the metal bump 12 and the electrode 17) can be obtained. In addition, since the flow of the conductive particles 1 in the lateral direction is suppressed, the conductive particles 1 are less likely to flow between the metal bumps 12 and between the electrodes 17, and the insulation in the lateral direction is favorably maintained. Moreover, since it becomes easy to maintain the insulation of a horizontal direction by this, the coverage of the mother particle 2 by the child particle 4 in the electrically-conductive particle 1 can be made small, and the electroconductivity of a lamination direction can also be improved.

  Moreover, since the conductive particle non-containing layers 13 and 15 in the anisotropic conductive adhesive 20 are first brought into contact with the metal bumps 12 and the electrodes 17 at the time of pressure bonding, the embedding property between the metal bumps 12 and the electrodes 17, and the chip 10. And good adhesion to the substrate 19 can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example.

[Preparation of mother particle M1]
First, 10 g of a plastic core having an average particle size of 2.6 μm made of a copolymer of divinylbenzene and acrylic acid having an adjusted degree of crosslinking was prepared. This plastic core has a carboxyl group on its surface. The hardness of the plastic core (compression elastic modulus (20% K value) when the particle diameter is displaced by 20% at 200 ° C.) was 280 kgf / mm ² .

  In addition, a 30% by mass polyethyleneimine aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) having a molecular weight of 70,000 was diluted with ultrapure water to 0.3% by mass.

  Next, 10 g of the above plastic core was added to 300 mL of a 0.3 mass% polyethyleneimine aqueous solution, and the mixture was stirred at room temperature for 15 minutes. The dispersion was filtered through a φ3 μm membrane filter (manufactured by Millipore) to take out the plastic core. The taken out plastic core was put into 300 g of ultrapure water and stirred at room temperature for 5 minutes. Next, this dispersion is filtered through a 3 μm membrane filter (manufactured by Millipore) to remove the plastic core, and then the plastic core on the membrane filter is washed twice with 200 g of ultrapure water. Polyethyleneimine not adsorbed on the body was removed. As a result, a plastic core having polyethyleneimine adsorbed on the surface was obtained.

  Further, a colloidal silica dispersion having an average particle diameter of 100 nm was diluted with ultrapure water to obtain a 0.33% by mass silica particle dispersion (total amount of silica: 1 g).

  The 0.33 mass% silica particle dispersion was charged with the plastic core adsorbed with the polyethyleneimine and stirred at room temperature for 15 minutes. The dispersion was filtered through a φ3 μm membrane filter (Millipore) to take out the plastic core. Since no silica was extracted from the filtrate, it was confirmed that substantially all silica particles were adsorbed on the plastic core.

  Next, the plastic core on which the silica particles were adsorbed was placed in 200 g of ultrapure water and stirred at room temperature for 5 minutes. This dispersion was filtered through a 3 μm membrane filter (manufactured by Millipore) to remove the plastic core, and then the plastic core on the membrane filter was washed twice with 200 g of ultrapure water. The plastic nuclei after washing were dried by sequentially heating at 80 ° C. for 30 minutes and 120 ° C. for 1 hour to obtain plastic nuclei (composite particles) having silica particles adsorbed on the surface.

  1 g of the above composite particles were collected, irradiated with ultrasonic waves having a resonance frequency of 28 kHz and an output of 100 W for 15 minutes, and then contained 8% by mass of Atotech Nene Gantt 834 (trade name, manufactured by Atotech Japan Co., Ltd.) which is a palladium catalyst. The resulting solution was added to 100 mL of the palladium catalyzed solution and stirred at 30 ° C. for 30 minutes while being irradiated with ultrasonic waves. Thereafter, the composite particles were taken out by filtration using a φ3 μm membrane filter (Millipore), and the taken out composite particles were washed with water. The composite particles after washing with water were added to a 0.5% by mass dimethylamine borane solution adjusted to pH 6.0 to obtain composite particles whose surface was activated.

  The surface-activated composite particles were immersed in distilled water and ultrasonically dispersed to obtain a suspension. While stirring this suspension at 50 ° C., nickel sulfate hexahydrate 50 g / L, sodium hypophosphite monohydrate 20 g / L, dimethylamine borane 2.5 g / L and citric acid 50 g / L were added. The electroless plating solution A having a pH adjusted to 7.5 by mixing was gradually added. As a result, an electroless nickel plating layer was formed on the composite particles. The phosphorus content in nickel was about 7%. The thickness of the nickel was adjusted by sampling and atomic absorption, and the addition of the electroless plating solution A was stopped when the thickness of the nickel plating layer reached 750 mm.

The composite particles on which the electroless nickel plating layer was formed were filtered and then washed with 100 mL of pure water for 60 seconds to obtain conductive particles (mother particles) having a nickel film on which protrusions were formed on the surface. When the height of the protrusion of the nickel film was observed with an SEM, it was 100 nm, which was almost the same as the particle size of the silica particles adsorbed on the plastic core. Further, the coverage of the mother particles by the protrusions was measured by image analysis of the SEM image, and was about 40%. Furthermore, when the saturation magnetization per unit volume was measured using BHV-525 manufactured by Riken Denshi and a specific gravity meter, it was 0.5 emu / cm ³ .

[Preparation of silicone oligomer]
(Silicone oligomer 1)
A glass flask equipped with a stirrer, a condenser and a thermometer is charged with a solution containing 118 g of 3-glycidoxypropyltrimethoxysilane and 5.9 g of methanol, and 5 g of activated clay and 4.8 g of distilled water are added thereto. The mixture was stirred at 75 ° C. for a certain time to synthesize a silicone oligomer having a molecular weight of 2000 (weight average molecular weight measurement by GPC, converted to polystyrene). The obtained silicone oligomer has a methoxy group or a silanol group as a terminal functional group that reacts with a hydroxyl group.

(Silicone oligomer 2)
Silicone oligomer 2 was synthesized in the same manner as silicone oligomer 1, except that the molecular weight was 600 by adjusting the stirring time and reaction temperature.

(Preparation of silicone oligomer 3)
Silicone oligomer 3 was synthesized in the same manner as silicone oligomer 1 except that the stirring time and reaction temperature were adjusted and the molecular weight was 1100.

(Preparation of silicone oligomer 4)
Silicone oligomer 4 was synthesized in the same manner as silicone oligomer 1 except that the stirring time and reaction temperature were adjusted and the molecular weight was 3200.

(Preparation of silicone oligomer 5)
Silicone oligomer 5 was synthesized in the same manner as silicone oligomer 1 except that the stirring time and reaction temperature were adjusted and the molecular weight was 3900.

(Preparation of silicone oligomer 6)
Silicone oligomer 6 was produced in the same manner as silicone oligomer 1 except that the stirring time and reaction temperature were adjusted and the molecular weight was 6000.

[Manufacture of child particles]
(Child particle C1)
3-acryloxypropyltrimethoxysilane (73.13% by mass), methyl acrylate (5.42% by mass), methacrylic acid (19.5% by mass), azobisisobutyronitrile (1.95% by mass) Fine particles were prepared with the composition of That is, each of the above compounds was collectively charged into a 500 ml flask while adjusting the above concentrations, and 350 g of acetonitrile was added as a solvent, followed by treatment with nitrogen (100 mL / min) for 1 hour. Dissolved oxygen was replaced. It was 0.07 mg / mL when the density | concentration of the dissolved oxygen was measured using the dissolved oxygen meter (Do meter B506 by Iijima Denshi Kogyo).

  Then, this solution was heated and stirred for about 6 hours at a water bath temperature of 80 ° C. using a stirrer to obtain a dispersion in which organic-inorganic composite particles were dispersed in a solvent. Next, about the obtained dispersion liquid, the organic-inorganic composite particles were settled by a centrifuge, and after discarding the supernatant, acetonitrile was added again to re-disperse the organic-inorganic composite particles. Thereafter, 1.76 g of an aqueous ammonia solution (28% by mass) was added as a particle curing catalyst (equal moles with respect to the charged carboxyl group amount of the organic-inorganic composite particles) to cause crosslinking of the organic-inorganic composite particles. Subsequently, with respect to the obtained dispersion, the organic-inorganic composite particles were again settled by centrifugation, and the supernatant was discarded. Then, the particles were redispersed in methanol. Thereby, the child particle dispersion liquid in which the organic-inorganic composite particles as the child particles C1 were dispersed in methanol was obtained. It was 300 nm when the average particle diameter of the obtained child particle C1 was measured by SEM.

(Child particle C2)
A child particle C2 was obtained in the same manner as the child particle C1, except that the concentration of each component at the time of preparing the organic-inorganic composite particle was adjusted so that the average particle diameter was 150 nm. At this time, the composition of the particles was set to be the same as that of the child particles C1.

(Child particle C3)
A child particle C3 was obtained in the same manner as the child particle C1, except that the concentration of each component in preparing the organic-inorganic composite particles was adjusted so that the average particle diameter was 400 nm. At this time, the composition of the particles was set to be the same as that of the child particles C1.

(Child particle C4)
A child particle C4 was obtained in the same manner as the child particle C1, except that the concentration of each component at the time of preparing the organic-inorganic composite particle was adjusted so that the average particle diameter was φ600 nm. At this time, the composition of the particles was set to be the same as that of the child particles C1.

[Manufacture of conductive particles]
(Conductive particle E1)
First, 8 mmol of mercaptoacetic acid was dissolved in 200 ml of methanol to prepare a reaction solution. Next, 10 g of the mother particle M1 described above was added to the reaction solution, and the mixture was stirred at room temperature for 2 hours with a three-one motor and a stirring blade having a diameter of 45 mm. The treated mother particles M1 were washed with methanol and then filtered through a φ3 μm membrane filter (Millipore) to obtain 10 g of mother particles M1 having a carboxyl group on the surface.

  Next, a 30% polyethyleneimine aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) having a molecular weight of 70,000 was diluted with ultrapure water to obtain a 0.3 wt% polyethyleneimine aqueous solution. 10 g of the mother particle M1 having a carboxyl group on the surface was added to the 0.3 wt% polyethyleneimine aqueous solution, and the mixture was stirred at room temperature for 15 minutes. Next, the mother particle M1 was filtered with a φ3 μm membrane filter (manufactured by Millipore), put in 200 g of ultrapure water, and stirred at room temperature for 5 minutes. Thereafter, the mother particle M1 is filtered with a membrane filter of φ3 μm (manufactured by Millipore), and the mother particle M1 is washed twice with 200 g of ultrapure water on this membrane filter, so that the polyethyleneimine that is not adsorbed on the mother particle M1 Was removed. Thus, mother particles M1 having polyethyleneimine (amino group-containing polymer; second polymer) attached to the surface were obtained.

  Next, the surface of the child particle C1 was treated with the silicone oligomer 1, and the child particle C1 with the silicone oligomer 1 (glycidyl group-containing oligomer; first polymer) attached to the surface was dispersed in methanol. A child particle dispersion 1 was prepared.

  Next, the mother particle M1 with polyethyleneimine attached to the surface is immersed in isopropyl alcohol, and the above-described child particle dispersion 1 is dropped therein, whereby the composite particle with the child particle C1 attached to the surface of the mother particle M1. Got. The coverage of the mother particles M1 by the child particles C1 in the composite particles was 35%, and this coverage was adjusted by the amount of the child particle dispersion 1 dropped. Thereafter, the obtained composite particles were dried at 80 ° C. for 30 minutes, and further heated and dried at 120 ° C. for 1 hour to obtain conductive particles E1.

(Conductive particle E2)
Conductive particles E2 were produced under the same conditions as the conductive particles E1, except that polyethyleneimine with a molecular weight of 10,000 (commercially available) was used instead of polyethyleneimine with a molecular weight of 70,000. At this time, the coverage of the mother particles M1 with the child particles C1 (child particle coverage) was set to 35%.

(Conductive particle E3)
Conductive particles E3 were produced under the same conditions as the conductive particles E1, except that polyethyleneimine with a molecular weight of 1800 (commercially available) was used instead of polyethyleneimine with a molecular weight of 70,000. At this time, the coverage of the mother particles M1 with the child particles C1 was set to 35%.

(Conductive particle E4)
Conductive particles E4 were produced under the same conditions as the conductive particles E1, except that polyethyleneimine with a molecular weight of 600 (commercially available) was used instead of polyethyleneimine with a molecular weight of 70,000. At this time, the coverage of the mother particles M1 with the child particles C1 was set to 35%.

(Conductive particle E5)
Conductive particles E5 were produced under the same conditions as the conductive particles E1, except that the silicone oligomer 2 was used instead of the silicone oligomer 1. At this time, the coverage of the mother particles M1 with the child particles C1 was set to 35%.

(Conductive particle E6)
Conductive particles E6 were produced under the same conditions as the conductive particles E1, except that the silicone oligomer 3 was used instead of the silicone oligomer 1. At this time, the coverage of the mother particles M1 with the child particles C1 was set to 35%.

(Conductive particle E7)
Conductive particles E7 were produced under the same conditions as the conductive particles E1, except that the silicone oligomer 4 was used instead of the silicone oligomer 1. At this time, the coverage of the mother particles M1 with the child particles C1 was set to 35%.

(Conductive particles E8)
Conductive particles E8 were produced under the same conditions as the conductive particles E1, except that the silicone oligomer 5 was used instead of the silicone oligomer 1. At this time, the coverage of the mother particles M1 with the child particles C1 was set to 35%.

(Conductive particles E9)
Conductive particles E9 were produced under the same conditions as the conductive particles E1, except that the silicone oligomer 6 was used instead of the silicone oligomer 1. At this time, the coverage of the mother particles M1 with the child particles C1 was set to 35%.

(Conductive particles E10)
A conductive particle E10 was produced under the same conditions as the conductive particle E1, except that the child particle C2 was used instead of the child particle C1. At this time, the coverage of the mother particles M1 with the child particles C2 was set to 35%.

(Conductive particles E11)
Conductive particles E11 were produced under the same conditions as the conductive particles E1, except that the child particles C3 were used instead of the child particles C1. At this time, the coverage of the mother particles M1 with the child particles C3 was set to 35%.

(Conductive particle E12)
Conductive particles E12 were produced under the same conditions as the conductive particles E1, except that the child particles C4 were used instead of the child particles C1. At this time, the coverage of the mother particles M1 with the child particles C4 was set to 35%.

(Conductive particles E13)
Conductive particles E13 were produced under the same conditions as the conductive particles E1, except that 3-glycidoxypropyltrimethoxysilane, which is a monomer, was used instead of the silicone oligomer 1. At this time, the coverage of the mother particles M1 with the child particles C1 was set to 35%.

(Conductive particle E14)
Conductive particles E14 were produced under the same conditions as the conductive particles E1, except that the surface of the child particles C1 was not treated with the silicone oligomer 1. At this time, the coverage of the mother particles M1 with the child particles C1 was set to 35%.

[Characteristic evaluation]
(Preparation of connection sample 1)
First, 100 g of phenoxy resin (trade name, PKHC, manufactured by Union Carbide) and 75 g of acrylic rubber (40 parts of butyl acrylate, 30 parts of ethyl acrylate, 30 parts of acrylonitrile, 3 parts of glycidyl methacrylate, molecular weight: 850,000) Was dissolved in 300 g of a solvent in which ethyl acetate and toluene were mixed at a weight ratio of 1: 1 to obtain a 30 wt% solution. Next, in this solution, 300 g of a liquid epoxy (Eboxy equivalent 185, manufactured by Asahi Kasei Epoxy Co., Ltd., Novacure HX-3941) containing a microcapsule type latent curing agent, and a liquid epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd., YL980) 400 g was added and stirred to obtain an adhesive solution 1.

  Moreover, the silica slurry which disperse | distributed (phi) 14nm silica (R202, Nippon Aerosil Co., Ltd.) to the solvent was added to the adhesive solution 1 so that the content of the silica solid content with respect to the solid content of an adhesive agent might be 5 wt%.

  Next, the conductive particles E1 were ultrasonically dispersed in 10 g of a solvent in which ethyl acetate and toluene were mixed at a weight ratio of 1: 1 to obtain a conductive particle dispersion. This ultrasonic dispersion was performed by immersing the beaker containing the conductive particles E1 and the solvent in an ultrasonic bath of 38 kHZ400W20L (test apparatus: US107, trade name of Fujimoto Kagakusha) and stirring for 1 minute.

  Films A and B for forming a film-like anisotropic conductive adhesive using the adhesive solution 1 obtained as described above, the adhesive solution 1 to which silica slurry is added, and the conductive particle dispersion. And C were obtained as follows.

Film A: Conductive particle dispersion is dispersed in adhesive solution 1 to which silica slurry is added, and this solution is applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) with a roll coater and dried at 90 ° C. for 10 minutes. Thus, a film A having a thickness of 10 μm was produced. This film A contained 100,000 particles / mm ² of conductive particles E1 per unit area.

  Film B: Adhesive solution 1 was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) with a roll coater and dried at 90 ° C. for 10 minutes to prepare film B containing no conductive particles having a thickness of 3 μm.

  Film C: Adhesive solution 1 was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) with a roll coater and dried at 90 ° C. for 10 minutes to produce film C containing 10 μm-thick conductive particles.

  Films A, B, and C thus obtained were sequentially laminated in the order of film B, film A, and film C to produce a film-like anisotropic conductive adhesive having a three-layer structure.

  Then, using the obtained film-like anisotropic conductive adhesive, a chip (1.7 × 1.7 mm) with gold bumps (area: 30 × 90 μm, space: 8 μm, height: 15 μm, bump number: 362), Thickness: 0.5 μm) and a glass substrate with a circuit (thickness: 0.7 mm) were connected as shown below.

That is, first, a film-like anisotropic conductive adhesive was attached to a circuit side surface of a glass substrate with a circuit under conditions of 80 ° C. and 0.98 MPa (10 kgf / cm ² ), and then the separator was peeled off.

  Next, on the anisotropic conductive adhesive, the chip is arranged so that the gold bump faces the anisotropic conductive adhesive side, and after aligning the gold bump of the chip and the glass substrate with a circuit, Heating and pressing are performed from above the chip under the conditions of 40 g / bump for 10 seconds, the main connection between the chip and the glass substrate with a circuit is performed, and the chip and the glass substrate with a circuit are connected with the above film-like anisotropic conductivity. The connection sample 1 connected by the adhesive was obtained.

(Preparation of connection sample 2)
A connection sample 2 was produced in the same manner as the connection sample 1 except that the conductive particles E2 were used instead of the conductive particles E1.

(Preparation of connection sample 3)
A connection sample 3 was produced in the same manner as the connection sample 1 except that the conductive particles E3 were used instead of the conductive particles E1.

(Preparation of connection sample 4)
A connection sample 4 was produced in the same manner as the connection sample 1 except that the conductive particles E4 were used instead of the conductive particles E1.

(Preparation of connection sample 5)
A connection sample 5 was produced in the same manner as the connection sample 1 except that the conductive particles E5 were used instead of the conductive particles E1.

(Preparation of connection sample 6)
A connection sample 6 was produced in the same manner as the connection sample 1 except that the conductive particles E6 were used instead of the conductive particles E1.

(Preparation of connection sample 7)
A connection sample 7 was produced in the same manner as the connection sample 1 except that the conductive particles E7 were used instead of the conductive particles E1.

(Preparation of connection sample 8)
A connection sample 8 was produced in the same manner as the connection sample 1 except that the conductive particles E8 were used instead of the conductive particles E1.

(Preparation of connection sample 9)
A connection sample 9 was produced in the same manner as the connection sample 1 except that the conductive particles E9 were used instead of the conductive particles E1.

(Preparation of connection sample 10)
A connection sample 10 was produced in the same manner as the connection sample 1 except that the conductive particles E10 were used instead of the conductive particles E1.

(Preparation of connection sample 11)
A connection sample 11 was produced in the same manner as the connection sample 1 except that the conductive particles E11 were used instead of the conductive particles E1.

(Preparation of connection sample 12)
A connection sample 12 was produced in the same manner as the connection sample 1 except that the conductive particles E12 were used instead of the conductive particles E1.

(Preparation of connection sample 13)
A connection sample 13 was produced in the same manner as the connection sample 1 except that the conductive particles E13 were used instead of the conductive particles E1.

(Preparation of connection sample 14)
A connection sample 14 was produced in the same manner as the connection sample 1 except that the conductive particles E14 were used instead of the conductive particles E1.

(Insulation resistance test and conduction resistance test)
The insulation resistance and conduction resistance of the connection samples 1 to 14 obtained above were measured. It is important that the anisotropic conductive adhesive has high insulation resistance between adjacent metal bumps in the chip, but low conduction resistance between the metal bumps facing each other and the circuit.

In this measurement, the insulation resistance between adjacent metal bumps in the chip was measured for 20 samples for each connection sample. And the insulation resistance measured the initial value, the thing whose insulation resistance exceeded 10 < ⁹ > ((ohm)) was made into the non-defective product, and the yield of the good product in 20 samples was computed. Further, the conduction resistance between the metal bump and the circuit was measured for 14 samples for each connection sample, and the average value thereof was calculated. For the conduction resistance, both an initial value and a value after a moisture absorption heat test (standing for 500 hours under conditions of an air temperature of 85 ° C. and a humidity of 85%) were measured.

(Child particle coverage)
Take a SEM image of each conductive particle E1 to E14 and analyze the image of 50% from the center to measure the ratio of the actual conductive particles covered with the child particles (child particle coverage) did.

(Coating variation by child particles (C.V.))
By taking SEM images of each of the conductive particles E1 to E14 and analyzing the image of 50% from the center, the variation in the ratio of the conductive particles covered by the child particles (child particle coverage) is measured. did.

(result)
Table 1 summarizes the results obtained by each of the above measurements. In Table 1, A to C are results obtained by determining the results obtained in each evaluation according to the following criteria. A: Good, B: Inferior to A, usable, C: Unusable

Connection samples 1 to 4 are results obtained when the weight average molecular weight (Mw) of polyethyleneimine (second polymer) attached to the surface of the mother particle is changed. The larger the molecular weight, the smaller the variation in the child particle coverage. When the molecular weight of polyethyleneimine was 600, the insulation was slightly lowered. Therefore, if the molecular weight of polyethyleneimine is smaller than this, the bond strength between the mother particles and the child particles may be weakened. Connection samples 5 to 9 are results when the weight average molecular weight (Mw) of the silicone oligomer (first polymer) adhering to the surface of the child particles is changed. The smaller the molecular weight of the silicone oligomer, the greater the variation in the coating of the child particles and the lower the insulating property. Also, when the molecular weight of the silicone oligomer was 6000, the variation in the coating of the child particles became large. Connection samples 10 to 12 are results when the diameter of the child particles is changed. When the child particle diameter was 600 nm, the child particle coverage was reduced, the coating variation was large, and the insulation was lower than when the child particle diameter was larger than that. Connection samples 13 to 14 are examples in which the child particles were not coated with the first polymer, but all of them were inferior to the other samples.

Claims (17)

Conductive mother particles,
A plurality of child particles having insulating properties arranged outside the mother particles;
A first polymer having a molecular weight of 500 or more attached to the surface of the child particles;
Conductive particles comprising:   The conductive particle according to claim 1, further comprising a second polymer having a molecular weight of 500 or more attached to a surface of the mother particle.   The conductive particles according to claim 1, wherein the first polymer is a silicone oligomer.   The conductive particles according to claim 1, wherein the first polymer has a glycidyl group.   The conductive particles according to any one of claims 2 to 4, wherein the second polymer has an amino group.   The particle diameter of the said child particle is 100 nm or more and 500 nm, The electroconductive particle as described in any one of Claims 1-5 characterized by the above-mentioned.   The particle diameter of the said mother particle is 3.0 micrometers or less, The electroconductive particle as described in any one of Claims 1-6 characterized by the above-mentioned.   The conductive particle according to claim 1, wherein the child particle has a silanol group.   The conductive particles according to any one of claims 2 to 8, wherein a chemical bond is generated between the first polymer and the second polymer.   A method for producing conductive particles, comprising a step of arranging a plurality of insulating child particles having a first polymer having a molecular weight of 500 or more attached to a surface outside a conductive mother particle.   The method for producing conductive particles according to claim 10, wherein the base particles having a second polymer having a molecular weight of 500 or more attached to the surface thereof are used.   The method for producing conductive particles according to claim 10 or 11, wherein the first polymer is a silicone oligomer.   The said 1st polymer has a glycidyl group, The manufacturing method of the electrically-conductive particle as described in any one of Claims 10-12 characterized by the above-mentioned.   The method for producing conductive particles according to any one of claims 11 to 13, wherein the second polymer has an amino group.   The method for producing conductive particles according to claim 10, wherein a particle diameter of the child particles is 100 nm or more and 500 nm.   The method for producing conductive particles according to claim 10, wherein a particle diameter of the base particles is 3.0 μm or less. The said child particle has a silanol group, The manufacturing method of the electrically-conductive particle as described in any one of Claims 10-16 characterized by the above-mentioned.

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