JP2002052333A - Coating method for fine particle, coated fine particle, anisotropic conductive adhesive, anisotropic conductive bonding film, and conductive connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method for fine particles, which has a high production efficiency and can coat fine particles of bad wettability and fine particles of a large specific gravity and make the thickness of coating layer uniform between the particles, a coated fine particle which has a low connection resistance and a large electric capacity in the case of connection and is stable in connection, thereby preventing the generation of a leak phenomenon, an anisotropic conductive adhesive, an anisotropic conductive bonding film, and a conductive connection structure. SOLUTION: In this coating method for fine particles, a mixture consisting of fine particles, a coating material, and a dispersion medium is prepared, and then the dispersion medium is slowly volatilized to be removed, thereby a coating layer is formed on each of the fine particles. The fine particles has a mean particle diameter of 0.2-3,000 μm, an aspect ratio of <5, and a CV value of <=40%. The coating material mainly comprises a water soluble resin and has a thickness of <=1/4 of the mean particle diameter of the fine particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating fine particles, coated fine particles coated by using the method for coating fine particles, coated fine particles used for connection between fine electrodes, and anisotropic conductive adhesive. The present invention relates to an agent, an anisotropic conductive bonding film, and a conductive connection structure.

[0002]

2. Description of the Related Art Conventionally, methods for coating fine particles include chemical methods such as interfacial polymerization, suspension polymerization in the presence of fine particles, and emulsion polymerization; spray drying, hybridization, electrostatic adhesion, spraying, and dipping. And physical and mechanical methods such as vacuum deposition. However, these coating methods require large-scale equipment, are inefficient because a large amount of uncoated particles are generated, that multiple particles are generated, that the coating thickness differs between the particles, There were problems such as difficulty in controlling the film thickness, being unsuitable for mass production, and inability to coat particles having poor wettability or heavy particles.

In electronic products such as a liquid crystal display, a personal computer, and a portable communication device, small electrical components such as semiconductor elements are electrically connected to the substrates and the substrates are electrically connected to each other. What is called anisotropic conductive material is used. Among the anisotropic conductive materials, anisotropic conductive adhesive or anisotropic conductive bonding film in which conductive fine particles and a binder resin are mixed is widely used. I have.

As the conductive fine particles used in the anisotropic conductive adhesive or the anisotropic conductive bonding film, organic base particles or inorganic base particles whose surfaces are plated with metal or metal particles are used. Have been. Such conductive fine particles are disclosed in, for example, Japanese Patent Publication No. 6-96871, Japanese Patent Laid-Open No. 4-369.
02, JP-A-4-269720, JP-A-3
-257710.

Anisotropic conductive bonding films formed into a film by mixing conductive fine particles and a binder resin or anisotropic conductive adhesive formed into a paste are disclosed in, for example, JP-A-63-231889. No., JP-A-4-25
No. 9766, JP-A-3-291807, JP-A-5-75250 and the like.

In recent years, with the miniaturization of electronic devices and electronic components, wirings on substrates and the like have become finer, and fine particles and improved particle diameter accuracy have been attempted so that conductive fine particles can cope with this. However, it is technically difficult to reduce the particle diameter to a certain value or less while maintaining high particle diameter accuracy. In addition, even if it is possible to reduce the particle diameter to a certain value or less while maintaining high particle diameter accuracy, if an attempt is made to sufficiently increase the electric capacity, adjacent particles are generated with a certain probability, so that the conductive fine particles There is a problem that a bridge is generated and a leak easily occurs between adjacent electrodes.

[0007]

SUMMARY OF THE INVENTION In view of the above, the present invention does not require a large-scale apparatus, does not generate uncoated fine particles, has a high production efficiency, is less likely to generate multiple particles, and has a thin coating layer. Controllability, it is possible to coat a large amount of fine particles, it is possible to coat fine particles having poor wettability and fine particles having a high specific gravity, and it is possible to make the thickness of the coating layer uniform between the particles. Method for coating fine particles, coated fine particles coated by using the method for coating fine particles, and coated fine particles having low connection resistance, large electric capacity at the time of connection, stable connection, and causing no leak phenomenon It is an object to provide an anisotropic conductive adhesive, an anisotropic conductive bonding film, and a conductive connection structure.

[0008]

According to the present invention, a coating layer is formed on the fine particles by mixing a fine particle, a coating substance, and a dispersion medium to prepare a mixture, and then gradually volatilizing and removing the dispersion medium. A method for coating fine particles, wherein the fine particles have an average particle diameter of 0.2 to 3000 μm, an aspect ratio of less than 5, and a CV value of 40% or less, and the coating substance is mainly a water-soluble resin. And the thickness of the coating layer is 1% of the average particle diameter of the fine particles.
/ 4 or less. Hereinafter, the present invention will be described in detail.

In the method for coating fine particles of the present invention, first, a mixture is prepared by mixing fine particles, a coating substance, and a dispersion medium. At this time, when the dissolution rate of the coating substance is low, for example, the coating substance may be first dissolved in the dispersion medium, and then the fine particles may be introduced into the solution of the coating substance.

The fine particles have an average particle size of 0.2 to 30.
00 μm. When the average particle diameter is less than 0.2 μm, the contact area between the particles becomes large, so that it may be difficult to form a single particle. When the average particle diameter is more than 3000 μm, the coating layer may become uneven due to the influence of gravity. Therefore, it is limited to the above range. It is preferably 0.5 to 100 μm, more preferably 1 to 20 μm, and still more preferably 2 to 10 μm.
μm. The average particle diameter is a value obtained by observing 300 arbitrary fine particles with an electron microscope.

The fine particles have an aspect ratio of less than 5. When the aspect ratio is 5 or more, the particle diameters become uneven, so that the contact area between the particles increases, and it becomes difficult to form a single particle. Therefore, the aspect ratio is limited to the above range. It is preferably less than 2, more preferably less than 1.4, even more preferably less than 1.1, particularly preferably less than 1.05. The aspect ratio is a value obtained by dividing the average major axis of fine particles obtained by observing 300 arbitrary particles with an electron microscope by the average minor axis.

The fine particles have a CV value of 40% or less. When the CV value exceeds 40%, the particle diameters become irregular, so that the contact area between the particles becomes large, and it becomes difficult to form a single particle. Therefore, the CV value is limited to the above range. Preferably 30%
Or less, more preferably 20% or less, still more preferably 10% or less, and particularly preferably 5% or less.

The CV value is defined by the following equation (1); CV value (%) = (σ / Dn) × 100 (1) (where σ represents the standard deviation of the particle diameter) , Dn represent the number average particle diameter). The standard deviation and the number average particle diameter are values obtained by observing 300 arbitrary fine particles with an electron microscope. Among them, those having an average particle diameter of 2 to 10 μm, an aspect ratio of less than 1.1 and a CV value of 10% or less are preferred.

The material of the fine particles is not particularly limited, and examples thereof include organic substances, polymers such as resins, inorganic substances, compounds and mixtures thereof, and metals. Further, the fine particles may be conductive fine particles having a conductive layer formed on at least the surface.

The coating material is not particularly limited, but is preferably a material containing a resin as a main component, and a material containing a resin soluble in a dispersion medium as a main component, since the coating layer is hardly cracked or peeled off. Is more preferred. Examples of the resin include polyolefins such as polyethylene, ethylene / vinyl acetate copolymer, and ethylene / acrylate copolymer; polymethyl (meth) acrylate;
Polyethyl (meth) acrylate, polybutyl (meth)
(Meth) acrylate polymers or copolymers such as acrylates; polystyrene, styrene / acrylate copolymers, SB-type styrene / butadiene block copolymers, SBS-type styrene / butadiene block copolymers,
SI-type styrene / isoprene block copolymer, SIS
Type styrene / isoprene block copolymers, block polymers of these water additives and the like; polyvinyl alcohol,
Examples thereof include thermoplastic resins such as vinyl polymers and copolymers, thermosetting resins such as epoxy resins, phenol resins, and melamine resins, and mixtures thereof. When the coating layer requires resin strength, the coating layer may be formed using a resin soluble in a dispersion medium and then made insoluble by a method such as crosslinking. The components of the coating substance other than the resin include, for example, organic substances, inorganic substances, compounds and mixtures thereof, and metals.

In particular, in the case of using a resin whose main component is a water-soluble resin as the coating substance, water can be used as the solvent, so there is no need to recover the solvent and the like, and the coating apparatus is simplified. be able to. As a resin soluble in water,
Polyvinyl alcohol (PVA) is preferably used.
Since PVA has a relatively high melting point as compared with ordinary thermoplastic resins such as polyethylene, high heat resistance can be expected without post-treatment such as crosslinking.

The above PVA preferably has a degree of polymerization of 30 to 10,000. If it exceeds 10,000, the viscosity of the solution when dissolved in the dispersion medium is high, and the wettability to the uneven particle surface is reduced, which may cause a decrease in the adhesion of the coating layer.
If it is less than the above range, the coating strength may be reduced and may not be suitable for practical use. More preferably 70
5,000, more preferably 70-2500, particularly preferably 200-2500.

The PVA has a saponification degree of 50 to 100%.
It is preferred that If it is less than 50%, the solubility in water as a dispersion medium is reduced and the workability of coating is reduced,
Alternatively, the above range is preferable because the film thickness that can be coated is too small, and the melting point is low and the heat resistance may be low. Within the above range, in the region where the degree of saponification is close to 100%, the water resistance, moisture resistance and heat resistance are improved, and in the range where the degree of saponification is slightly lower, the solubility in water is improved and the coating workability is improved. Single particles can be easily formed during the coating operation, and the coating quality can be improved. For this reason, the saponification degree can be appropriately selected according to the purpose within the above range. More preferably, it is 70 to 100%, and when it aims at uniform coating, it is still more preferably 75 to 95%, particularly preferably 80 to 92%, especially for improving moisture resistance and heat resistance. Is more preferably 9
It is 0 to 100%, particularly preferably 95 to 100%.

Among the above-mentioned PVAs, those having a degree of polymerization of 30 to 10,000 and a degree of saponification of 50 to 100% are preferable, and a degree of polymerization of 70 to 5000 and a degree of saponification of 70 to 1 are preferred.
More preferably, it is 00%.

The dispersion medium is not particularly limited as long as it is liquid and can dissolve PVA when preparing a mixture. For example, a solvent handbook (Kodansha)
And the like, ordinary organic solvents, water, inorganic solvents, mixtures and compounds thereof. The dispersion medium is
From the point of removing while gradually volatilizing using the method described later, the boiling point at the pressure at which the dispersion medium is volatilized is 60 to
Those at 200 ° C. are preferred. If the boiling point is less than 60 ° C., volatilization occurs rapidly, so that the coating substance is densely accumulated, and the fine particles are also densely aggregated, may not be formed into single particles, or the coating layer may be foamed. If the amount exceeds the above range, it takes too much time to volatilize, and the productivity may be remarkably reduced or the coating layer may be deteriorated. The temperature is more preferably 90 to 150 ° C.

In the method for coating fine particles of the present invention, a coating layer is formed on fine particles by preparing a mixture having the above-described structure and then removing the dispersion medium while gradually volatilizing. The method of removing the dispersion medium while gradually volatilizing is not particularly limited. For example, a method of volatilizing at a temperature lower than the boiling point of the dispersion medium by 60 ° C. or more, without reducing the pressure by 40 kPa or more, that is, by increasing the pressure by 40 kPa or more than the atmospheric pressure. For example, a method of volatilizing under a condition that the temperature is not lowered may be used.

In the method for coating fine particles of the present invention, the reason for removing the dispersion medium while gradually evaporating it is that it is preferable to form the coating layer while generating voids between the fine particles. , A uniform coating layer can be formed. In order to form a more uniform coating layer, it is preferable that at least a large part of the dispersion medium is removed by volatilization, and part of the coating material, or the interface between the fine particles and the coating material be destroyed by an external force. .

As a method for generating voids between the fine particles, for example, when the dispersion medium of the mixture is removed while being volatilized gradually, at least half or more of the fine particles having an interval between the fine particles less than the average particle diameter of the fine particles are used. And the like.

Since irregularities are usually present on the surface of the fine particles, when the dispersion medium is removed while being volatilized gradually, when the viscosity of the dispersion medium is high, when the surface tension of the dispersion medium is high, the coating material and If the wettability with fine particles is poor,
Air, moisture and the like may accumulate in concaves and convexes on the surface of the fine particles, and the adhesiveness between the coating substance and the fine particles may decrease.

In order to prevent a decrease in the adhesiveness between the coating substance and the fine particles, before coating the fine particles, the fine particles are preliminarily depressurized to remove air, moisture and the like existing on the surface irregularities. Further, it is preferable to return the pressure to atmospheric pressure after coating the fine particles in a reduced pressure state. The coated fine particles that have been returned to the atmospheric pressure after the pressure reduction have the coating layer and the fine particles more firmly adhere to each other due to the atmospheric pressure.

The degree of the pressure reduction is 66.7 k from the atmospheric pressure.
The pressure is preferably reduced to not less than Pa, more preferably 80
A reduced pressure of kPa or more, more preferably 93.3 kP
a.

When the fine particles are brought into a reduced pressure state before coating, it is preferable to heat the fine particles. This is because the heating removes moisture and air from the surface of the fine particles more quickly and completely. The temperature during heating is preferably from 50 to 150 ° C, more preferably from 80 to 100 ° C.

The thickness of the coating layer formed by the method for coating fine particles of the present invention is not more than 1/4 of the average particle diameter of the fine particles. When the thickness of the coating layer exceeds 1/4, the space between the fine particles is completely clogged with the coating material, so that the particles cannot be formed into single particles. May be increased, or a lump of only the coating substance may be formed. For this reason, when forming a coating layer thicker than the above range, it is preferable to repeat the above-described step of forming the coating layer a plurality of times. Also, if the strength of the coating layer is too strong, when the particles are formed into single particles, the coating layer may be peeled off to form bare fine particles,
In addition, it is difficult to remove the coating layer when the coating layer needs to be partially removed as in the case where the coated fine particles are manufactured using conductive fine particles as the fine particles and the conductive connection structure is further manufactured by the method described below. It may be. Preferably 1/10
And more preferably 5 / (molecular weight of the resin forming the coating layer) ^1/2 . In the present specification, the molecular weight of the resin, when the resin is a cross-linked resin,
It is assumed that the molecular weight is 1,000,000.

The method for coating fine particles of the present invention uses fine particles having a specific gravity of 1.5 or more, which could not form a coating layer due to sedimentation in a dispersion medium or the like by a conventional coating method such as a chemical method. Even if it is, a coating layer can be suitably formed. Furthermore, even if the specific gravity of the fine particles is 2.3 or more, the specific gravity of the fine particles is 3 or more, or 6 or more, the coating layer can be suitably formed.

The method for coating fine particles according to the present invention does not require a large-scale apparatus and does not generate uncoated fine particles, so that production efficiency is high, multiple particles are hardly generated, and the thickness of the coating layer can be easily controlled. A large amount of fine particles can be easily coated, and fine particles having poor wettability and high specific gravity can be coated. Therefore, coated fine particles having a uniform coating layer thickness among particles can be produced by the above method. Coated fine particles coated by the method for coating fine particles of the present invention are also one of the present invention.

The above coated fine particles have an average particle size of 0.1.
It is preferably larger than 2 μm and 4000 μm or less. It is more preferably 0.5 to 100 μm, and still more preferably 1 to 100 μm.
To 20 μm, particularly preferably 3 to 10 μm.

[0032] The coated fine particles have the shape of the fine particles maintained. Therefore, when the particles having an aspect ratio of less than 5 are coated, the obtained particles have an aspect ratio of less than 5, and when the particles have an aspect ratio of less than 2, the obtained particles have an aspect ratio of less than 2. Yes, if you cover fine particles with an aspect ratio of less than 1.4,
The resulting coated fine particles have an aspect ratio of less than 1.4, and if the fine particles having an aspect ratio of less than 1.1 are coated,
The aspect ratio of the obtained coated fine particles is less than 1.1. If the fine particles having an aspect ratio of less than 1.05 are coated, the obtained coated fine particles have an aspect ratio of less than 1.05.

When the fine particles having a CV value of 40% or less are coated, the resulting coated fine particles have a CV value of 40% or less, and when the fine particles having a CV value of 30% or less are coated, the obtained coated fine particles have a CV value of 30% or less. The CV value is 30% or less, and the CV value is 2
If the fine particles of 0% or less are coated, the CV value of the obtained coated fine particles is 20% or less, and if the CV value of 10% or less is coated, the CV value of the obtained coated fine particles is 10%.
Or less, if the particles have a CV value of 5% or less,
The CV value of the obtained conductive fine particles is 5% or less.

When preparing the above-mentioned coated fine particles, if the conductive fine particles having at least a conductive layer formed on the surface are used as the fine particles, the obtained coated fine particles can be used as the coated conductive fine particles.

The conductive fine particles having a conductive layer formed on at least the surface thereof are not particularly limited, and may be those usually used as conductive fine particles. , Carbon particles, metal particles and the like. Among these, polymer materials with a small CV value and a small aspect ratio are used for the core of the particles, and the metal is coated on the particles, from the viewpoint of increasing the contact area with the electrode and increasing the stability. Are preferable, and those plated with gold are more preferable. Further, metal particles are also preferable in that fine particles having high conductivity can be obtained.

As the coating material when the coated fine particles are used as the coated conductive fine particles, an insulating material is preferable, and therefore, an insulating resin is preferable. When the coating layer is formed of an insulating material, a leak occurs between adjacent electrodes when a conductive connection structure is manufactured using the coated conductive fine particles by a process described later when the coating layer is formed of an insulating material. Without doing so, the concentration of the coated conductive fine particles can be increased. Further, in the connection direction of the electrodes, the coating layer flows or breaks due to heating and / or pressurization, so that the coating layer is removed from the contact surface with the electrode, and conduction between the electrodes can be achieved.

Furthermore, since the coated conductive fine particles have a coating layer formed by using the method for coating fine particles of the present invention, there are no particles or multiple particles having no coating layer formed thereon.
Since the thickness of the coating layer is also uniform, leakage is less likely to occur between adjacent electrodes, and there is little residue of only the coating, so that conduction between the electrodes is not hindered.

The above-mentioned coated conductive fine particles are mainly used for electrically connecting two electrodes facing each other.
Examples of a method for electrically connecting two electrodes facing each other using the coated conductive fine particles include, for example, dispersing the coated conductive fine particles in a binder resin to form an anisotropic conductive adhesive or an anisotropic conductive bonding. A method of preparing a film, bonding and connecting two electrodes using the anisotropic conductive adhesive or anisotropic conductive bonding film, and connecting separately using a binder resin and the coated conductive fine particles. Method and the like. In this specification, the anisotropic conductive adhesive includes an anisotropic conductive paste, an anisotropic conductive ink, and the like.

The anisotropic conductive adhesive or the binder resin constituting the anisotropic conductive bonding film is not particularly limited.
For example, thermoplastic resins such as acrylate resins, ethylene / vinyl acetate resins, and styrene / butadiene block copolymers; curable resin compositions obtained by the reaction of monomers and oligomers having a glycidyl group with a curing agent such as isocyanate; Examples of the composition include a composition that is cured by heat or light. Preferably, among the curable resin compositions, a low-temperature curable resin that cures at a low temperature and a photocurable resin.

In the anisotropic conductive bonding film, the coated conductive fine particles may be dispersed at random or may be arranged at a specific position. The anisotropic conductive bonding film in which the coated conductive fine particles are randomly dispersed is generally used for a general purpose use. In addition, the anisotropic conductive bonding film in which the coated conductive fine particles are arranged at predetermined positions can perform efficient electrical bonding. The coating thickness of the anisotropic conductive adhesive is not particularly limited, but is preferably from 10 to several hundreds of μm. Such an anisotropic conductive adhesive and an anisotropic conductive bonding film are also one aspect of the present invention.

The objects to be connected by the coated conductive fine particles, the anisotropic conductive adhesive, and the anisotropic conductive bonding film include, for example, a substrate having an electrode portion formed on a surface thereof, and an electric component such as a semiconductor. And the like. The above substrate is roughly classified into a flexible substrate and a rigid substrate. Examples of the flexible substrate include a resin sheet having a thickness of 50 to 500 μm. As the material of the resin sheet, for example, polyimide, polyamide, polyester,
And polysulfone.

The rigid substrate is roughly classified into a resin substrate and a ceramic substrate. Examples of the above-mentioned resin include glass fiber reinforced epoxy resin, phenol resin, cellulose fiber reinforced phenol resin and the like. Examples of the ceramic material include silicon dioxide, alumina, and glass.

The structure of the substrate is not particularly limited.
It may be a single layer, and in order to increase the number of electrodes per unit area, for example, a plurality of layers are formed, and these layers are electrically connected to each other by means such as through hole formation. May be used.

The electric parts are not particularly limited, and include, for example, active parts such as semiconductors such as transistors, diodes, ICs, and LSIs; and passive parts such as resistors, capacitors, and crystal oscillators. The shape of the electrodes formed on the surface of the substrate or the electric component is not particularly limited, and examples thereof include stripes, dots, and arbitrary shapes.

As the material of the electrode, for example, gold,
Silver, copper, nickel, palladium, carbon, aluminum, ITO and the like can be mentioned. In order to reduce the contact resistance, it is preferable to use an electrode further coated with gold on copper, nickel or the like. The thickness of the electrode is 0.1 to 1
Preferably, the width of the electrode is 1 to
Preferably it is 500 μm.

The bonding between the coated conductive fine particles and a substrate or a component is performed, for example, by forming an anisotropic conductive bonding film containing the coated conductive fine particles on a substrate or an electric component having electrodes formed on the surface thereof. There is a method of arranging, placing an electrode of another substrate or an electric component on the substrate, heating and pressing. Instead of the anisotropic conductive bonding film, a predetermined amount of an anisotropic conductive paste containing coated conductive fine particles can be used by a printing means such as screen printing or a dispenser. For the above-mentioned heating and pressurizing, a crimping machine equipped with a heater, a bonding machine or the like is used.

A method not using the anisotropic conductive bonding film and the anisotropic conductive paste is also possible. For example, a liquid binder is injected into a gap between two electrode portions bonded together via coated conductive fine particles. Thereafter, a method of curing or the like can be used.

The electrodes constituting the substrate or the electric component are bonded to each other via coated conductive fine particles, an anisotropic conductive adhesive or an anisotropic conductive bonding film, and the coating layer of the coated fine particles is heated and heated. Another aspect of the present invention is a conductive connection structure in which the conductive material of the coated fine particles comes into contact with the electrode portion by flowing or breaking by pressurization, and conduction between the electrode portions is achieved.

As described above, the anisotropic conductive adhesive, the anisotropic conductive bonding film, and the conductive connection structure of the present invention have a structure in which at least the surface of the conductive fine particles is formed of a conductive material. It is characterized by using coated fine particles having a coating layer formed thereon. Therefore, in the anisotropic conductive adhesive, anisotropic conductive bonding film, and the conductive connection structure,
Leakage between adjacent electrodes does not occur due to the presence of the coating layer containing the coated fine particles, and the concentration of the coated fine particles can be increased. In addition, at the contact site between the electrode and the coated fine particles,
The coating layer flows or breaks due to heating and / or pressurization, whereby the coating layer is removed at the contact surface with the electrode, thereby achieving conduction between the electrodes and containing the coating conductive fine particles at a high concentration. As a result, a large electric capacity can be secured.

[0050]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(Example 1) Fine particles having an average particle diameter of 5 µm
m, an aspect ratio of 1.04, and a CV value of 4%.
50 g of pure water in which 3 g of polyvinyl alcohol having a saponification degree of about 000 and about 88 were dissolved was mixed to obtain a uniform dispersion. Next, the obtained mixture was spread into a thin film in a vat, and while gradually evaporating water, the thin film mixture was cut into a network using a spatula to form a fine lump. Further, while the dispersion medium was volatilized to such an extent that the micro lump did not coalesce with each other, the remaining dispersion medium was volatilized while being crushed in a mortar to form single particles. When the fine particles in the mixture were observed using a scanning electron microscope, at least half of the fine particles were present at intervals equal to or less than the average particle diameter of the fine particles until the fine particles were converted into single particles. The coated fine particles thus obtained had a coating layer thickness of about 50 nm and an average particle diameter of 5.0 μm.
m, the aspect ratio was 1.05, and the CV value was 4%. The coating was uniform and contained little multi-particles or residues of coating substances.

(Example 2) As fine particles, the average particle diameter was 5 μm.
m, an aspect ratio of 1.04, and a CV value of 8%.
000, polyvinyl alcohol 0.3 with a saponification degree of about 88
50 g of pure water in which g was dissolved was mixed to obtain a uniform dispersion.
Next, the obtained mixture is spread into a thin film in a vat,
While gradually evaporating water, the thin film-like mixture was cut into a network using a spatula to form a fine lump. Further, while the dispersion medium was volatilized to such an extent that the micro lump did not coalesce with each other, the remaining dispersion medium was volatilized while being crushed in a mortar to form single particles. When the fine particles in the mixture were observed using a scanning electron microscope, at least half of the fine particles were present at intervals equal to or less than the average particle diameter of the fine particles until the fine particles were converted into single particles. The coated fine particles thus obtained had a coating layer thickness of about 5 nm, an average particle diameter of 5.0 μm,
The coating was uniformly coated at an aspect ratio of 1.04 and a CV value of 4%, and contained little multi-particles or residues of coating substances.

(Example 3) As fine particles, the average particle diameter was 5 μm.
m, an aspect ratio of 1.04, and a CV value of 8%.
000, polyvinyl alcohol 0.3 with a saponification degree of about 98
50 g of pure water in which g was dissolved was mixed to obtain a uniform dispersion.
Next, the obtained mixture is spread into a thin film in a vat,
While gradually evaporating water, the thin film-like mixture was cut into a network using a spatula to form a fine lump. Further, while the dispersion medium was volatilized to such an extent that the micro lump did not coalesce with each other, the remaining dispersion medium was volatilized while being crushed in a mortar to form single particles. When the fine particles in the mixture were observed using a scanning electron microscope, at least half of the fine particles were present at intervals equal to or less than the average particle diameter of the fine particles until the fine particles were converted into single particles. The coated fine particles thus obtained had a coating layer thickness of about 5 nm, an average particle diameter of 5.0 μm,
The coating was uniformly coated at an aspect ratio of 1.04 and a CV value of 4%, and contained little multi-particles or residues of coating substances.

Example 4 Fine particles having an average particle diameter of 5 μm
m, an aspect ratio of 1.04, and a CV value of 8%.
400, polyvinyl alcohol 0.3 with a saponification degree of about 98
50 g of pure water in which g was dissolved was mixed to obtain a uniform dispersion.
Next, the obtained mixture is spread into a thin film in a vat,
While gradually evaporating water, the thin film-like mixture was cut into a network using a spatula to form a fine lump. Further, while the dispersion medium was volatilized to such an extent that the micro lump did not coalesce with each other, the remaining dispersion medium was volatilized while being crushed in a mortar to form single particles. When the fine particles in the mixture were observed using a scanning electron microscope, at least half of the fine particles were present at intervals equal to or less than the average particle diameter of the fine particles until the fine particles were converted into single particles. The coated fine particles thus obtained had a coating layer thickness of about 5 nm, an average particle diameter of 5.0 μm,
The coating was uniformly coated at an aspect ratio of 1.04 and a CV value of 4%, and contained little multi-particles or residues of coating substances.

Example 5 The coated conductive fine particles of Example 2 were mixed and dispersed in a binder solution obtained by dissolving a thermosetting epoxy resin in toluene. Next, the dispersion solution of the coated conductive fine particles was applied on a release film to a constant thickness, and toluene was evaporated to obtain an anisotropic conductive bonding film. The thickness was 25 μm. Thereafter, 50 μm square gold bumps were formed on the glass-epoxy substrate at an electrode pitch of 70 μm.
× 10 lines, paste the obtained anisotropic conductive bonding film,
Further, after positioning the same substrate thereon,
Heating and pressing were performed at 50 ° C. for 2 minutes to obtain a conductive connection structure.
The connection resistance value of the obtained conductive connection structure was sufficiently low, and the interline insulation between adjacent electrodes was sufficiently maintained. Also,
A thermal cycle test showed no change.

(Example 6) An anisotropic conductive bonding film and a conductive connection structure were obtained in the same manner as in Example 5, except that the coated conductive fine particles of Example 3 were used. The connection resistance value of the obtained conductive connection structure was sufficiently low, and the interline insulation between adjacent electrodes was sufficiently maintained. A cooling cycle test was performed, but no change was observed.

(Example 7) An anisotropic conductive bonding film and a conductive connection structure were obtained in the same manner as in Example 5, except that the coated conductive fine particles of Example 4 were used. The connection resistance value of the obtained conductive connection structure was sufficiently low, and the interline insulation between adjacent electrodes was sufficiently maintained. A cooling cycle test was performed, but no change was observed.

(Comparative Example 1) Fine particles having an average particle diameter of 0.1
Titanium oxide having a particle size of less than 2 μm and a styrene-acrylic copolymer having a number average molecular weight of 30,000 and a Tg of 80 ° C. soluble in xylene as a coating substance are added so that the coating thickness becomes about 20 nm. The mixture was uniformly dispersed in 20 g to obtain a mixture. Next, the obtained mixture is spread into a thin film in a vat, and while gradually volatilizing xylene,
The mixture in the form of a thin film was cut into a mesh using a spatula to form a fine lump. Furthermore, while the dispersion medium is volatilized to such an extent that the fine lumps do not coalesce with each other, while crushing in a mortar,
An attempt was made to volatilize the remaining dispersion medium into single particles, but the aggregates were hard and could not be formed into single particles.

(Comparative Example 2) Average particle diameter of 40 as fine particles
Coated microparticles were obtained in the same manner as in Example 1 except that 20 g of divinylbenzene microspheres having a size of 00 µm, an aspect ratio of 1.04, and a CV value of 4% were used. The obtained coated fine particles contained a large amount of resin residue at the bottom of the particles, the coating thickness was non-uniform, and a large amount of residues of the coating material.

(Comparative Example 3) As fine particles, an average particle diameter of 5 μm
m, an aspect ratio of 5, and a CV value of 4%, except that 20 g of divinylbenzene-based short fibers were used, but an attempt was made to form single particles in the same manner as in Example 1. However, the agglomerates were hard and single particles could be formed. Did not. Then, further rubbing resulted in peeling of the coating layer, generation of a large amount of residue, and partial destruction of divinylbenzene-based short fibers.

Comparative Example 4 Fine particles having an average particle diameter of 5 μm
m, an aspect ratio of 1.04, and a CV value of 50%, except that 20 g of divinylbenzene-based microspheres were used. Could not. Then, when further crushed, the coating layer was peeled off, a large amount of residue was generated, and some divinylbenzene microspheres were broken.

Comparative Example 5 As a coating substance, 1 g of a styrene-acrylic copolymer having a number average molecular weight of 30,000 and a Tg of 80 ° C. soluble in diethyl ether was used, and the dispersion medium was changed to diethyl ether. In the same manner as in Example 1, a mixture in which fine particles and a coating substance were dispersed was obtained. Next, the obtained mixture was spread in a thin film in a vat, and diethyl ether was evaporated. Since the evaporation rate was high, the mixture in the form of a thin film could not be cut into a mesh using a spatula. Further, the fine chunks were crushed in a mortar and tried to be formed into single particles, but the fine chunks were hard and could not be formed into single particles. Then, when further crushed, the coating layer was peeled off, a large amount of residue was generated, and some divinylbenzene microspheres were broken. Also, the coating thickness was non-uniform for the single particles.

(Comparative Example 6) An average particle diameter of 5 μm as fine particles
m, an aspect ratio of 1.04, divinylbenzene-based microspheres having a CV value of 4%, styrene and acrylate as a coating substance, and benzoyl peroxide as a polymerization initiator, and suspension polymerization in a polyvinyl alcohol dispersion medium. went. The polymer obtained by this polymerization reaction was a styrene-acrylic copolymer having a number average molecular weight of 30,000 and a Tg of 80 ° C., and covered divinylbenzene-based microspheres. In addition, multiple particles and many particles not containing microspheres were also generated.

Comparative Example 7 Fine particles having an average particle diameter of 5 μm
m, 20 g of divinylbenzene microspheres having an aspect ratio of 1.04 and a CV value of 4%, and 1 g of a styrene-acrylic copolymer having a number average molecular weight of 30,000 and a Tg of 80 ° C. soluble in xylene as a coating substance, as a dispersion medium. The mixture was uniformly dispersed in 100 g of certain xylene to obtain a mixture. When the solvent was removed under heating and reduced pressure while spraying the obtained mixture by a spray drying method, divinylbenzene microspheres were coated, but the coating film thickness varied depending on the particles, and multiple particles and microspheres were obtained. Many particles containing no were also generated.

(Comparative Example 8) Instead of the coated conductive fine particles,
Example 5 except that uncoated conductive fine particles were used.
In the same manner as in the above, an anisotropic conductive bonding film and a conductive connection structure were obtained. Although the connection resistance value of the obtained conductive connection structure was sufficiently low, a short circuit occurred between adjacent electrodes.

Comparative Example 9 An anisotropic conductive bonding film and a conductive connection structure were prepared in the same manner as in Example 5, except that the coated conductive fine particles obtained by suspension polymerization were used as the coated conductive fine particles. Obtained. In the obtained conductive connection structure, although the line-to-line insulation between adjacent electrodes was maintained, there were bumps that were not connected to the counter electrode. In addition, when a cooling / heating cycle test was performed, bumps that were short-circuited between adjacent electrodes were found.

[0067]

As described above, the method for coating fine particles of the present invention does not require a large-scale device, and does not generate uncoated fine particles. Therefore, the method is efficient. The thickness of the layer can be controlled, a large amount of fine particles can be coated, and fine particles having poor wettability and high specific gravity can be coated. Therefore, coated fine particles having a uniform coating layer thickness among particles can be produced by the above method. Further, since the coated fine particles of the present invention are coated using the fine particle coating method of the present invention, the shape of the fine particles is maintained. Furthermore, when the conductive fine particles are used as the fine particles, the connection fine particles have low connection resistance,
The electric capacity at the time of connection is large, the connection is stable, and no leak phenomenon occurs. Further, the anisotropic conductive adhesive and the anisotropic conductive bonding film of the present invention have low connection resistance, large electric capacity at the time of connection, stable connection, and do not cause a leak phenomenon. Further, the conductive connection structure of the present invention has low connection resistance, large electric capacity at the time of connection, stable connection, and does not cause a leak phenomenon.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C09C 3/10 C09C 3/10 4K018 C09J 9/02 C09J 9/02 5G301 201/00 201/00 5G307 H01B 1/22 H01B 1/22 D 5/00 5/00 C 5/16 5/16 13/00 501 13/00 501Z // C08L 101: 00 C08L 101: 00 F term (reference) 4F070 AA71 AB21 AB22 AC80 AD04 AE06 AE27 CB12 DB03 DB04 DC02 DC06 DC07 DC08 FA01 FA05 FA09 FA10 FA14 FA15 4G004 BA00 4G075 AA27 BB02 BB05 BD16 CA57 FC11 4J037 AA00 CA03 CC15 DD04 DD05 DD13 EE04 EE28 EE43 FF11 4J040 DA051 DF021 DM011 EC001 BF001 DA01 BC03 DA01 BC01 DA041 DA42 DA57 DD03 DE03 5G307 AA02 HA02 HB01 HB03 HC01

Claims (13)

[Claims] 1. A method of coating fine particles, wherein a mixture is prepared by mixing fine particles, a coating substance, and a dispersion medium, and then the dispersion medium is removed while gradually volatilizing to form a coating layer on the fine particles. The fine particles have an average particle size of 0.2.
2 to 3000 μm, aspect ratio less than 5, CV value of 4
0% or less, the coating substance is mainly composed of a resin soluble in water, and the thickness of the coating layer is 1/4 or less of the average particle diameter of the fine particles. A method for coating fine particles, characterized in that: 2. The method for coating fine particles according to claim 1, wherein the coating substance is mainly composed of polyvinyl alcohol. 3. The polyvinyl alcohol has a degree of polymerization of 30.
3. The method for coating fine particles according to claim 2, wherein the saponification degree is 50 to 100%. 4. Polyvinyl alcohol having a degree of polymerization of 70
The method for coating fine particles according to claim 2, wherein the saponification degree is 70 to 100%. 5. The fine particles have an average particle size of 2 to 10 μm,
5. The method according to claim 1, wherein the aspect ratio is less than 1.1 and the CV value is 10% or less. 6. The method for coating fine particles according to claim 1, wherein the specific gravity of the fine particles is 1.5 or more. 7. Coated fine particles coated using the method for coating fine particles according to claim 1, 2, 3, 4, 5, or 6. 8. The coated fine particles according to claim 7, wherein the fine particles are conductive fine particles having a conductive layer formed on at least the surface thereof, and the material constituting the nucleus is a polymer. 9. The coated fine particles according to claim 7, wherein the fine particles are conductive fine particles having a conductive layer formed on at least a surface thereof, and a material constituting a nucleus thereof is a metal. 10. An anisotropic conductive adhesive characterized in that the coated fine particles according to claim 8 or 9 are dispersed in a binder resin. 11. An anisotropic conductive bonding film, wherein the coated fine particles according to claim 8 or 9 are dispersed in a binder resin. 12. An electrode part constituting a substrate or an electric component is attached to each other via the coated fine particles according to claim 8 or 9, and the coating layer of the coated fine particles flows or flows by heating and / or pressing. A conductive connection structure wherein the conductive material of the coated fine particles comes into contact with the electrode portion by breaking, thereby establishing conduction between the electrode portions. 13. The anisotropic conductive adhesive according to claim 10, wherein the electrodes constituting the substrate or the electric component are connected to each other.
1. The coating layer of the coated fine particles bonded together via the anisotropic conductive bonding film according to 1 and in the anisotropic conductive adhesive or in the anisotropic conductive bonding film flows or breaks by heating and / or pressing. By doing so, the conductive material of the coated fine particles comes into contact with the electrode portion, and conduction between the electrode portions is achieved.