JP4662748B2 - Conductive fine particles and anisotropic conductive materials - Google Patents

Description

  The present invention relates to conductive fine particles and anisotropic conductive materials, and in particular, conductive fine particles having a low connection resistance value and excellent conductive reliability, and a low connection resistance value using the conductive fine particles. The present invention relates to an anisotropic conductive material having excellent properties.

  The conductive fine particles are mixed and kneaded with a binder resin or an adhesive, for example, anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive adhesive, anisotropic conductive film, anisotropic Widely used as anisotropic conductive materials such as conductive sheets.

  These anisotropic conductive materials are, for example, for electrically connecting substrates in electronic devices such as liquid crystal displays, personal computers, and mobile phones, and electrically connecting small components such as semiconductor elements to the substrate. In order to achieve this, it is used by being sandwiched between electrodes of opposing substrates or between electrodes of various components.

  In the case of the connection between the electrodes, for example, the conductive fine particles dispersed in the binder resin or the like are in the binder resin and are contacted with the electrode by removing the binder resin at the time of thermocompression bonding. Is needed.

  As the conductive fine particles used in the anisotropic conductive material, conventionally, conductive fine particles obtained by performing metal plating on the surface of non-conductive fine particles such as resin fine particles having a uniform particle diameter have been used. However, with rapid progress and development of electronic devices in recent years, further reduction in connection resistance of conductive fine particles used as anisotropic conductive materials and improvement in conductive reliability have been demanded.

In order to reduce the connection resistance of the conductive fine particles and improve the conductive reliability, conductive fine particles having protrusions on the surface have been reported as conductive fine particles (see, for example, Patent Document 1).
By providing protrusions on the surface of the conductive fine particles, the exclusion property of the binder resin is increased, and the connection resistance is reduced and the conductive reliability is improved.

  Patent Document 1 discloses conductive fine particles obtained by performing metal plating on the surface of non-conductive fine particles having protrusions on the surface. The substrate fine particles of the conductive fine particles are protruding fine particles formed by composite fine particles obtained by combining mother particles and child particles, and the protruding portions are made of glass such as plastic or silicate glass.

JP-A-4-36902

  However, for example, when an anisotropic conductive adhesive or an anisotropic conductive film is disposed on the connection surface and used by pressure bonding, the conductive fine particles are often used after being compressed by about 30%. If the protrusions are hard, the connection area is reduced, which is not sufficient for further reducing connection resistance and improving conductive reliability.

  In view of the above situation, the present invention provides conductive fine particles having a low connection resistance value and excellent conductive reliability, and an anisotropic conductive material having a low connection resistance value using the conductive fine particles and excellent conductive reliability. The purpose is to provide.

In order to achieve the above object, the invention according to claim 1 is a composite fine particle which is used for an anisotropic conductive material and in which non-conductive fine particles B smaller than non-conductive fine particles A are bonded to the surface of non-conductive fine particles A. Conductive fine particles formed by metal plating on the surface, wherein non-conductive fine particles A are made of cross-linked resin fine particles using a cross-linkable monomer, and non-conductive fine particles B are made of non-cross-linkable monomers of a non-crosslinked resin particles had, as the crosslinking monomer, divinylbenzene, and Conjugate dienes or polyfunctional (meth) acrylates are used, as the non-crosslinkable monomer, styrene, alpha- methyl styrene, p- methyl styrene, p- chlorostyrene, chloromethylstyrene, vinyl chloride, unsaturated nitriles or monofunctional (meth) acrylates are used, the conductive fine particles 10% compression strange Conductivity compressive modulus in (10% K value) 5000~8500N / mm ^2, and compressive modulus obtained while a 30% compressive deformation (30% K value) is 1500~3000N / mm ² obtained while Providing fine particles.

Further, an invention according to claim 2 wherein, relative to the average particle size of the non-conductive fine particles A, provide a conductive fine particle according to claim 1, wherein the average particle size of the non-conductive fine particles B is less than 1/10 To do.

The invention according to claim 3 provides the conductive fine particles according to claim 1 or 2 , wherein the non-conductive fine particles A have an average particle diameter of 10 μm or less.

The invention according to claim 4 provides the conductive fine particles according to any one of claims 1 to 3 , wherein 10 or more non-conductive fine particles B are bonded to the surface of the non-conductive fine particles A. .

The invention according to claim 5 provides an anisotropic conductive material in which the conductive fine particles according to any one of claims 1 to 4 are dispersed in a resin binder.

Details of the present invention will be described below.
The conductive fine particles of the present invention are obtained by applying metal plating to the surface of composite fine particles in which non-conductive fine particles B smaller than non-conductive fine particles A are bonded to the surface of non-conductive fine particles A.
Furthermore, the conductive fine particles of the present invention have a compressive elastic modulus (10% K value) of 5000 to 8500 N / mm ² when the conductive fine particles are subjected to 10% compression deformation, and compression when 30% compression deformation is performed. The elastic modulus (30% K value) needs to be 1500 to 3000 N / mm ² .

The compressive elastic modulus when the conductive fine particles are 10% compressively deformed (hereinafter also referred to as 10% K value) is 5000 to 8500 N / mm ² and the compressive elastic modulus when 30% compressively deformed (hereinafter 30). % K value) is set to 1500 to 3000 N / mm ^2, and when the compression is as low as 10% compression, the protrusion formed by the non-conductive fine particles B of the composite fine particles has a high exclusion property of the binder resin, and When the compression rate is increased to about 30% after the electrode terminal and the conductive fine particles are in contact, the protrusion is deformed, the connection area between the electrode terminal and the conductive fine particle is increased, the connection resistance value is low, and the conductive Conductive fine particles having excellent reliability can be obtained.

When the 10% K value is less than 5000 N / mm ² , it may be too soft at the time of low compression of about 10% compression, and the exclusion property of the binder resin due to the protrusion may not be sufficient, and when it exceeds 8500 N / mm ² , It may be too hard to damage the electrode.

When the 30% K value is less than 1500 N / mm ^{2, when} it is further compressed to about 30% compression, it is still too soft and the exclusion of the binder resin by the protrusions may not be sufficient, and exceeds 3000 N / mm ² . In some cases, the protrusions are too hard to deform and the connection area is difficult to increase.

  In the present invention, the compression elastic modulus when the conductive fine particles are 10% compressed and deformed, that is, 10% K value, and the compression elastic modulus when the conductive fine particles are compressed and deformed by 30%, that is, 30% K value. It is important to measure The above measurement was performed on conductive fine particles obtained by metal plating on the surface of composite fine particles in which non-conductive fine particles B were bonded to the surface of non-conductive fine particles A, and non-conductive fine particles A, non-conductive fine particles B, and Conductive fine particles as a whole. That is, the measurement adopts a measured value when not only the non-conductive fine particles A but also the non-conductive fine particles B are sandwiched and compressed.

  In the present invention, the 10% K value and the 30% K value are obtained by compressing the conductive fine particles on the smooth end surface of a square column having a side of 50 μm using a micro compression tester (Fischer H-100, manufactured by Fischer). It can be determined by compressing at 0.33 mN / sec and a maximum test load of 40 mN. The 10% K value is the compression elastic modulus when the conductive fine particle diameter is 10% compression deformed, and the 30% K value is the compression elastic modulus when the conductive fine particle diameter is 30% compressive deformed.

The 10% K value can be obtained from the following equation.
K = (3 / √2) ・ F1 ・ S1 ^-3/2・ R ^-1/2
F1: Load value at 10% compression deformation of conductive fine particles (N)
S1: Compression displacement (mm) in 10% compression deformation of conductive fine particles
R: radius of conductive fine particles (mm)

The 30% K value can be obtained from the following equation.
K = (3 / √2) ・ F2 ・ S2 ^-3/2・ R ^-1/2
F2: Load value at 30% compression deformation of conductive fine particles (N)
S2: Compression displacement (mm) in 30% compression deformation of conductive fine particles
R: radius of conductive fine particles (mm)

  The composite fine particles in the conductive fine particles of the present invention are those in which non-conductive fine particles B smaller than the non-conductive fine particles A are bonded to the surface of the non-conductive fine particles A.

  The method for bonding the nonconductive fine particles B to the surface of the nonconductive fine particles A is not particularly limited. For example, the method using an adhesive, the method of fusing the nonconductive fine particles B, the nonconductive fine particles A A method of accumulating and adhering non-conductive fine particles B on the surface by van der Waals force, a method of adhering non-conductive fine particles B on the surface of non-conductive fine particles A by a mechanical action such as rotation of a container, etc. Can be mentioned.

The non-conductive fine particles A is state, and are not having an appropriate compression characteristics, hard particles is favored over the non-conductive fine particles B, comprising a crosslinked resin fine particles.

  A method for obtaining the non-conductive fine particles A is not particularly limited, and examples thereof include a method using a polymerization method such as suspension polymerization, seed polymerization, dispersion polymerization, dispersion seed polymerization, emulsion polymerization, or the like.

  In order to form the cross-linked resin fine particles, there is no particular limitation as long as a cross-linkable monomer is contained. A non-crosslinkable monomer may be used in combination.

  Examples of the crosslinkable monomer include divinylbenzene and its derivatives, conjugated dienes such as butadiene and isoprene, polytetramethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and the like. Examples include functional (meth) acrylates. Here, (meth) acrylate means methacrylate or acrylate. The said crosslinkable monomer may be used independently and may use 2 or more types together.

  Examples of the non-crosslinkable monomer include styrene derivatives such as styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene, and chloromethylstyrene; unsaturated nitriles such as vinyl chloride and acrylonitrile, isobutyl ( And monofunctional (meth) acrylates such as (meth) acrylate and isooctyl (meth) acrylate. The said non-crosslinkable monomer may be used independently and may use 2 or more types together.

The non-conductive fine particles B is state, and are not having an appropriate compression characteristics, soft particles is favored over the non-conductive fine particles A, consisting of non-crosslinked resin particles.

  The method for obtaining the non-conductive fine particles B is not particularly limited, and examples thereof include a method using a polymerization method such as suspension polymerization, seed polymerization, dispersion polymerization, dispersion seed polymerization, emulsion polymerization, or the like.

In order to form the said non-crosslinked resin fine particle, if it is formed only from the non-crosslinkable monomer, it will not specifically limit.
Examples of the non-crosslinkable monomer include those described above for the non-crosslinkable monomer of the non-conductive fine particles A.

  Accordingly, in the conductive fine particles of the present invention, it is preferable that the nonconductive fine particles A are made of crosslinked resin fine particles and the nonconductive fine particles B are made of non-crosslinked resin fine particles.

In the present invention, the non-conductive fine particles B need to be smaller than the non-conductive fine particles A, and have an average particle size of 1/10 or less with respect to the average particle size of the non-conductive fine particles A. Preferably there is.
The average particle size of the non-conductive fine particles B is smaller than the average particle size of the non-conductive fine particles A, in particular, 1/10 or less, so that the particle size of the conductive fine particles as a whole is uniform and sandwiched between the electrodes. When done, a good connection can be obtained.

  Therefore, in the conductive fine particles of the present invention, the average particle diameter of the nonconductive fine particles B is preferably 1/10 or less of the average particle diameter of the nonconductive fine particles A.

The shape of the nonconductive fine particles A is not particularly limited, and examples thereof include a spherical shape and an elliptical spherical shape. Of these, spherical is preferable.
The average particle diameter of the nonconductive fine particles A is not particularly limited, but is preferably 10 μm or less, and more preferably 1 to 5 μm. When the average particle diameter of the non-conductive fine particles A exceeds 10 μm, the range used as the anisotropic conductive material between the substrate electrodes may be exceeded.

  Therefore, the conductive fine particles of the present invention preferably have an average particle size of the nonconductive fine particles A of 10 μm or less.

The shape of the nonconductive fine particles B is not particularly limited, and examples thereof include a spherical shape, an elliptical spherical shape, a disc shape, a cylindrical shape, a cube, a rectangular parallelepiped, and a tetrahedron.
The average particle diameter of the non-conductive fine particles B is not particularly limited, but is preferably 0.1 to 1 μm. If the average particle size of the non-conductive fine particles B is less than 0.1 μm, it is difficult to obtain the effect of bonding the non-conductive fine particles B to form protrusions. If the average particle size exceeds 1 μm, the particle size of the entire conductive fine particles is uniform. When it is used while being sandwiched between electrodes, it may be difficult to obtain a good connection.

In the present invention, the number of nonconductive fine particles B bonded to the surface of the nonconductive fine particles A (hereinafter also referred to as the number of nonconductive fine particles B) is preferably 10 or more. When the number of the non-conductive fine particles B is 10 or more, the conductive fine particles of the present invention are non-conductive regardless of the direction in which the conductive fine particles are oriented at the time of connection using the conductive fine particles as an anisotropic conductive material. Protrusions due to the fine particles B come into contact with the electrodes, and a good connection state can be obtained.
Control of the number of non-conductive fine particles B can be easily performed by changing the amount of non-conductive fine particles B to be added to the non-conductive fine particles A, for example.

  Therefore, in the conductive fine particles of the present invention, it is preferable that 10 or more non-conductive fine particles B are bonded to the surface of the non-conductive fine particles A.

The conductive fine particles of the present invention are obtained by performing metal plating on the surface of the composite fine particles in which the nonconductive fine particles B are bonded to the surface of the nonconductive fine particles A.
Therefore, the conductive fine particles are obtained by performing metal plating on the surface while leaving the protrusions formed by bonding the nonconductive fine particles B on the surface of the nonconductive fine particles A as they are.

  The metal used for the said metal plating is not specifically limited, For example, nickel, gold | metal | money, silver, copper, cobalt or the alloy etc. which have these as a main component are mentioned.

  The method of applying the metal plating is preferably an electroless plating method because the substrate fine particles that are the composite fine particles are non-conductive fine particles. Especially, the method by electroless nickel plating is used more suitably. The metal plating may be a single metal layer or a multilayer composed of a plurality of metals.

Examples of the electroless nickel plating method include a base material provided with a catalyst when an electroless nickel plating solution composed of sodium hypophosphite as a reducing agent is bathed and heated according to a predetermined method. Examples include a method in which fine particles are immersed and a nickel layer is deposited by a reduction reaction of Ni ²⁺ + H ₂ PO ₂ ⁻ + H ₂ O → Ni + H ₂ PO ₃ ⁻ + 2H ⁺ .

Examples of the method for imparting the catalyst include alkali degreasing, acid neutralization, sensitizing in a tin dichloride (SnCl ₂ ) solution, and activation in a palladium dichloride (PdCl ₂ ) solution. Examples include a method of performing an electroless plating pretreatment step. Sensitizing is a process of adsorbing Sn ²⁺ ions on the surface of a non-conductive substance, and activating is a reaction of Sn ²⁺ + Pd ²⁺ → Sn ⁴⁺ + Pd ^0, which is non-conductive. This is a process in which palladium is generated on the surface of the material and used as a catalyst core for electroless plating.

  The thickness of the metal plating plating film is preferably 0.02 to 5 μm. When the thickness of the plating film is less than 0.02 μm, the metal layer is thin and it is difficult to obtain conductivity. In addition, when the thickness of the plating film exceeds 5 μm, the non-conductive material constituting the substrate fine particles and the metal formed by plating have different coefficients of thermal expansion, so that the plating film is easily peeled off. There is.

  The conductive fine particles of the present invention are preferably formed with a plating film having the outermost surface as a gold layer. By making the outermost surface a gold layer, the connection resistance value can be reduced and the surface can be stabilized. When the outermost surface of the plating film is already a gold layer, the connection resistance value can be reduced and the surface can be stabilized without forming a gold layer again.

  The gold layer can be formed by a known method such as electroless plating, displacement plating, or electroplating.

  Although the film thickness of the said gold layer is not specifically limited, 1-100 nm is preferable, More preferably, it is 1-50 nm. If it is less than 1 nm, for example, it may be difficult to prevent oxidation of the underlying nickel layer, and the connection resistance value may increase. When the thickness exceeds 100 nm, for example, in the case of displacement plating, the underlying nickel layer may be eroded and adhesion between the substrate fine particles and the underlying nickel layer may be deteriorated.

  Various characteristics of the conductive fine particles in the present invention, for example, the thickness of the plating film, the thickness of the gold layer, the average particle size of the non-conductive fine particles A, the average particle size of the non-conductive fine particles B, the non-conductive fine particle B The existence number can be obtained by observing particles or cross sections of conductive fine particles with an electron microscope.

  As a method for preparing a sample for performing the cross-sectional observation, for example, conductive fine particles are embedded in a thermosetting resin and cured by heating, and the sample is brought into a mirror surface state that can be observed using a predetermined abrasive paper or abrasive. The method etc. which grind | polish are mentioned.

  The observation of the conductive fine particles is performed with a scanning electron microscope (SEM). As the magnification, an easily observable magnification may be selected. For example, the observation is performed at 5000 times. Further, the cross-sectional observation of the conductive fine particles is performed with a transmission electron microscope (TEM), and as the magnification, an easily observable magnification may be selected. For example, the observation is performed at 50,000 times.

  The average film thickness of the conductive fine particle plating film and the gold layer is a film thickness obtained by arithmetically averaging 10 randomly selected conductive fine particles. In addition, when the film thickness of each electroconductive fine particle has nonuniformity, the maximum film thickness and the minimum film thickness are measured, and let the film thickness be the arithmetic average value.

  The average particle diameters of the non-conductive fine particles A and the non-conductive fine particles B are measured for 10 randomly selected non-conductive fine particles A or non-conductive fine particles B, and the arithmetic average is obtained. Shall be.

  The number of the non-conductive fine particles B is calculated by counting the number of protrusions formed by the non-conductive fine particles B for 50 randomly selected conductive fine particles and converting them to the number per one conductive fine particle. , The existing number.

  The anisotropic conductive material of the present invention is obtained by dispersing the above-described conductive fine particles of the present invention in a resin binder.

  The anisotropic conductive material is not particularly limited as long as the conductive fine particles of the present invention are dispersed in a resin binder. For example, anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive An adhesive, an anisotropic conductive film, an anisotropic conductive sheet, etc. are mentioned.

  The method for producing the anisotropic conductive material of the present invention is not particularly limited. For example, the conductive fine particles of the present invention are added to an insulating resin binder, and mixed and dispersed uniformly. For example, a method of using an anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive adhesive, etc., or adding the conductive fine particles of the present invention to an insulating resin binder and mixing them uniformly. After preparing the conductive composition, the conductive composition is uniformly dissolved (dispersed) in an organic solvent as necessary, or heated and melted to release a release material such as release paper or release film. Applying to the mold processing surface so as to have a predetermined film thickness, and performing drying or cooling as necessary, for example, an anisotropic conductive film, an anisotropic conductive sheet, etc. Depending on the type of anisotropic conductive material to be produced, Manufacturing methods may Taking. Further, the insulating resin binder and the conductive fine particles of the present invention may be used separately without being mixed to form an anisotropic conductive material.

  The resin of the insulating resin binder is not particularly limited. For example, vinyl resins such as vinyl acetate resins, vinyl chloride resins, acrylic resins, styrene resins; polyolefin resins, ethylene -Thermoplastic resins such as vinyl acetate copolymers and polyamide resins; Epoxy resins, urethane resins, polyimide resins, unsaturated polyester resins, and curable resins composed of these curing agents; styrene-butadiene-styrene blocks Thermoplastic block copolymers such as copolymers, styrene-isoprene-styrene block copolymers, and hydrogenated products thereof; elastomers such as styrene-butadiene copolymer rubber, chloroprene rubber, acrylonitrile-styrene block copolymer rubber ( Rubbers). These resins may be used alone or in combination of two or more. The curable resin may be in any curing form such as a room temperature curing type, a thermosetting type, a photocuring type, and a moisture curing type.

  In addition to the insulating resin binder and the conductive fine particles of the present invention, the anisotropic conductive material of the present invention includes, for example, a bulking agent, a softening agent, etc. 1 type of various additives such as additives (plasticizers), tackifiers, antioxidants (anti-aging agents), heat stabilizers, light stabilizers, UV absorbers, colorants, flame retardants, organic solvents, etc. Or 2 or more types may be used together.

  Since the conductive fine particles of the present invention have the above-described configuration, it is possible to obtain one having a low connection resistance value and excellent conductivity reliability. In addition, the anisotropic conductive material using the conductive fine particles has a low connection resistance value and can be obtained with excellent conductivity reliability.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example.

(Preparation of non-conductive fine particles A)
5 g of 0.75 μm styrene particles as seed particles, 500 g of ion-exchanged water, and 100 g of a 5 wt% aqueous polyvinyl alcohol solution were mixed and dispersed by applying ultrasonic waves, and then placed in a separable flask and uniformly stirred.
Next, 128 g of polytetramethylene glycol diacrylate and 32 g of divinylbenzene were added to the separable flask with an emulsion prepared from 1035 g of ion-exchanged water to which 12 g of an oil-soluble polymerization initiator, 9 g of triethanolamine lauryl sulfate, and 118 g of ethanol were added. The mixture was stirred for 12 hours to allow the seed particles to absorb the monomer.
Thereafter, 500 g of a 5 wt% aqueous polyvinyl alcohol solution was added, nitrogen gas was introduced, and the mixture was reacted in an autoclave at 130 ° C. for 9 hours to obtain nonconductive fine particles A composed of crosslinked resin fine particles having an average particle size of 3.75 μm. .

(Preparation of non-conductive fine particles B1)
After mixing and dissolving 95% by weight of styrene and 5% by weight of methacrylic acid, 100 parts by weight of the resulting monomer mixture was heated to 70 ° C., 2 parts by weight of potassium persulfate was added as a radical polymerization initiator, and further 70 ° C. For 12 hours to obtain non-crosslinked resin fine particles. Thereafter, the particles are dried and non-conductive fine particles comprising non-crosslinked resin fine particles having an average particle size of 0.3 μm and a CV value (a value obtained by dividing the standard deviation of the particle size distribution by the average particle size as a percentage) is 3%. B1 was obtained.

(Preparation of non-conductive fine particles B2)
After mixing and dissolving 75% by weight of styrene, 20% by weight of divinylbenzene and 5% by weight of methacrylic acid, 100 parts by weight of the resulting monomer mixture was heated to 70 ° C., and then 2 parts by weight of potassium persulfate as a radical polymerization initiator. Was further added and reacted at 70 ° C. for 12 hours to obtain crosslinked resin fine particles. Thereafter, drying was performed to obtain non-conductive fine particles B2 made of crosslinked resin fine particles having an average particle size of 0.3 μm and a CV value of 3%.

Example 1
(Preparation of composite fine particles)
A non-conductive fine particle B1 was attached to the surface of the non-conductive fine particle A by a hybridizer to obtain composite fine particles having protrusions on the surface.

(Electroless nickel plating process)
10 g of the obtained composite fine particles were subjected to alkali degreasing with an aqueous sodium hydroxide solution, acid neutralization, and sensitizing in a tin dichloride solution. Thereafter, an electroless plating pretreatment consisting of activation in a palladium dichloride solution was performed, and after filtering and washing, composite fine particles having palladium adhered to the particle surface were obtained.
The obtained composite fine particles adhered with palladium were further diluted with 1200 ml of water, and after adding 4 ml of plating stabilizer, nickel sulfate 450 g / l, sodium hypophosphite 150 g / l, sodium citrate 116 g / l 120 ml of a mixed solution of 6 ml of plating stabilizer was added through an 8 metering pump. Then, it stirred until pH became stable, it confirmed that hydrogen foaming stopped, and the electroless-plating pre-process was performed.
Subsequently, a further 650 ml of a mixed solution of 450 g / l of nickel sulfate, 150 g / l of sodium hypophosphite, 116 g / l of sodium citrate, and 35 ml of plating stabilizer was added through a metering pump. Then, it stirred until pH became stable, it confirmed that hydrogen foaming stopped, and the electroless-plating late process was performed.
Next, the plating solution was filtered, and the filtrate was washed with water, and then dried with a vacuum dryer at 80 ° C. to obtain nickel-plated conductive fine particles.

(Gold plating process)
Thereafter, the surface was further plated with gold by a displacement plating method to obtain conductive fine particles.

With respect to the obtained conductive fine particles, the average film thickness of nickel and the average film thickness of gold are determined by cross-sectional observation with a transmission electron microscope (TEM), and the number of non-conductive fine particles B1 is determined with a scanning electron microscope (SEM). It was determined by observation.
Moreover, about the obtained electroconductive fine particles, 10% K value and 30% K value were measured using the micro compression tester (Fischer H-100, product made by Fischer).
These results are shown in Table 1.

(Comparative Example 1)
(Preparation of composite fine particles)
A non-conductive fine particle B2 was adhered to the surface of the non-conductive fine particle A by a hybridizer to obtain composite fine particles having protrusions on the surface.

  The electroless nickel plating step and the gold plating step were performed in the same manner as in Example 1 to obtain conductive fine particles.

  About the obtained electroconductive fine particles, it carried out similarly to Example 1, and calculated | required the average film thickness of nickel, the average film thickness of gold | metal | money, the number of nonelectroconductive microparticles B2, the 10% K value, and the 30% K value. . These results are shown in Table 1.

(Comparative Example 2)
Preparation of composite fine particles was not performed.
In the electroless nickel plating process, composite fine particles were not used, but non-conductive fine particles A were used instead, and 1 ml of plating stabilizer was used instead of 4 ml of the plating stabilizer added first, and then the plating stabilizer was used. Nickel-plated conductive fine particles were obtained in the same manner as in Example 1 except that no addition was made. In the electroless nickel plating process, the plating solution self-decomposes, and a nickel lump by self-decomposition is formed at the same time as the nickel coating, and the nickel lump (bulk shape with a particle size of about 0.3 μm) becomes a protrusion. It was.
Thereafter, the gold plating step was performed in the same manner as in Example 1 to obtain conductive fine particles.

  About the obtained electroconductive fine particles, it carried out similarly to Example 1, and calculated | required the average film thickness of nickel, the average film thickness of gold | metal | money, the number of nickel lump presence, 10% K value, and 30% K value. These results are shown in Table 1.

(Evaluation of connection resistance)
An anisotropic conductive adhesive is mixed with an epoxy adhesive (Mitsui Chemicals Co., Ltd., “Struct Bond XN-5A”) at a ratio of 2% by weight of the obtained conductive fine particles and 1% by weight of silica fine particles. did.
This anisotropic conductive adhesive was applied by screen printing almost at the center on a glass plate (20 mm × 40 mm) on which ITO electrodes were formed with a pitch width of 300 μm. The other glass plate (20 mm x 40 mm) on which ITO electrodes were formed with a 300 μm pitch width was overlaid so that the electrode parts overlap vertically, and then a pressure of 325 kPa was applied, and heat compression was performed at 160 ° C. for 5 minutes. Pasted together. At this time, the compression rate (%) and the connection resistance value (Ω) were measured. The connection resistance value was a particle resistance value (Ω / piece) converted per single particle, and the value was obtained by changing the particle diameter of the silica fine particles so that the compression rate was 10% and the compression rate was 30%. These results are shown in Table 1.

  From Table 1, the particles using the conductive fine particles obtained in the Examples had sufficiently low particle resistance values even when the compression rate was 10% or 30%. Therefore, it can be seen that the conductive fine particles of the present invention have a low connection resistance value and excellent conductivity reliability.

  According to the present invention, it is possible to provide conductive fine particles having a low connection resistance value and excellent conductive reliability, and an anisotropic conductive material having a low connection resistance value using the conductive fine particles and excellent conductive reliability. .

Claims (5)

Conductive fine particles which are used for anisotropic conductive materials and are obtained by performing metal plating on the surface of composite fine particles in which non-conductive fine particles B smaller than non-conductive fine particles A are bonded to the surface of non-conductive fine particles A. ,
The non-conductive fine particles A consist of cross-linked resin fine particles using a cross-linkable monomer, the non-conductive fine particles B consist of non-cross-linked resin fine particles using a non-cross-linkable monomer,
As the crosslinking monomer, divinylbenzene, Conjugate dienes or polyfunctional (meth) acrylates have been used, as the non-crosslinkable monomer, styrene, alpha-methyl styrene, p- methyl styrene, p-chlorostyrene, chloromethylstyrene , vinyl chloride, unsaturated nitriles or monofunctional (meth) acrylates are used,
The compressive elastic modulus (10% K value) when the conductive fine particles are 10% compressively deformed is 5000 to 8500 N / mm ² , and the compressive elastic modulus (30% K value) when 30% compressively deformed is 1500. Conductive fine particles characterized by being -3000 N / mm ² .   2. The conductive fine particles according to claim 1, wherein the average particle diameter of the nonconductive fine particles B is 1/10 or less of the average particle diameter of the nonconductive fine particles A. 3.   The conductive fine particles according to claim 1 or 2, wherein the non-conductive fine particles A have an average particle size of 10 µm or less.   The conductive fine particles according to any one of claims 1 to 3, wherein 10 or more nonconductive fine particles B are bonded to the surface of the nonconductive fine particles A.   An anisotropic conductive material comprising the conductive fine particles according to any one of claims 1 to 4 dispersed in a resin binder.