WO2021095803A1 - 導電性粒子、その製造方法及びそれを含む導電性材料 - Google Patents
導電性粒子、その製造方法及びそれを含む導電性材料 Download PDFInfo
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- WO2021095803A1 WO2021095803A1 PCT/JP2020/042255 JP2020042255W WO2021095803A1 WO 2021095803 A1 WO2021095803 A1 WO 2021095803A1 JP 2020042255 W JP2020042255 W JP 2020042255W WO 2021095803 A1 WO2021095803 A1 WO 2021095803A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B5/00—Non-insulated conductors or conductive bodies characterised by their form
- H01B5/16—Non-insulated conductors or conductive bodies characterised by their form comprising conductive material in insulating or poorly conductive material, e.g. conductive rubber
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
- C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
- H01B13/0026—Apparatus for manufacturing conducting or semi-conducting layers, e.g. deposition of metal
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B5/00—Non-insulated conductors or conductive bodies characterised by their form
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
- H01R11/00—Individual connecting elements providing two or more spaced connecting locations for conductive members which are, or may be, thereby interconnected, e.g. end pieces for wires or cables supported by the wire or cable and having means for facilitating electrical connection to some other wire, terminal, or conductive member, blocks of binding posts
- H01R11/01—Individual connecting elements providing two or more spaced connecting locations for conductive members which are, or may be, thereby interconnected, e.g. end pieces for wires or cables supported by the wire or cable and having means for facilitating electrical connection to some other wire, terminal, or conductive member, blocks of binding posts characterised by the form or arrangement of the conductive interconnection between the connecting locations
Definitions
- the present invention relates to conductive particles and a conductive material containing the same.
- the conductive particles used as the conductive material of the anisotropic conductive material such as the anisotropic conductive film and the anisotropic conductive paste, those in which a conductive layer made of metal is formed on the surface of the core material particles are generally known. This conductive layer provides electrical connection between electrodes and wiring.
- Patent Document 2 the compression hardness when compressed by 5% by the conductive particles composed of the conductive layer including the crystal layer having a crystal structure of nickel and phosphorus is at least a specific value.
- the conductive portion has a plurality of protrusions on the outer surface, the ratio of the (111) plane in the X-ray diffraction of these protrusions is 50% or more, and the average maximum diameter of the base is 1 nm or more and 500 nm. The following conductive particles are described.
- the oxide film formed on the electrode and the conductive layer can be eliminated, and the contact area between the electrode and the conductive particle after connection can be increased.
- the purpose is to reduce the connection resistance and increase the connection reliability when the electrodes are electrically connected by obtaining the enhanced conductive particles, but there is room for further improvement.
- an object of the present invention is to provide conductive particles having a lower connection resistance and higher connection reliability than before.
- the present invention is connected to a conductive layer having a hardness sufficient to eliminate the oxide film formed on the electrodes at the initial stage of pressure-connecting the electrodes.
- the present invention has been completed by finding that the conductive particles having a hardness ratio of the conductive particles satisfying a specific range can reduce the connection resistance and have excellent connection reliability.
- the maximum value of the compressive hardness of the conductive particles is 24000 N / mm 2 or more, and the compressibility is less than 5%.
- the maximum value of the compressive hardness is shown in, the average value of the compressive hardness at the compressibility of 20% or more and 50% or less is 5000 to 18000 N / mm 2 , and the average value of the compressive hardness at the compressibility of 20% or more and 50% or less. It provides conductive particles in which the ratio of the maximum value of compressive hardness to the value is 1.5 or more and 10 or less.
- the present invention is a method for producing conductive particles in which a conductive layer is formed on the surface of core material particles by an electroless plating method, and is a step of adding a sulfur compound to an electroless plating reaction solution during the formation of the conductive layer.
- FIG. 1 is an SEM image of the conductive particles obtained in Example 1.
- the conductive particles of the present invention have a maximum compressive hardness (hereinafter, sometimes referred to as “K value”) of 24000 N / mm 2 or more, preferably 29000 N / mm 2 or more, and a compressibility of 5%. Less than, preferably a compressibility of 1%, 2%, 3% or 4%, the compressibility shows the highest value.
- the maximum value of compression hardness is preferably 50,000 N / mm 2 or less.
- the compression hardness in the present invention refers to the case where a load is applied to conductive particles having a radius of R (mm) at a load speed of 2.23 mN / sec using a microcompression tester (for example, MCTM-500 manufactured by Shimadzu Corporation).
- the load value F (N) was measured, and it is a value obtained by the following formula.
- Compressive hardness (N / mm 2 ) (3 / ⁇ 2) x F x S -3/2 x R- 1 / 2
- the radius R (mm) of the conductive particles is a value calculated from the average particle diameter described later
- the compression ratio is the rate of change of the length in the particle diameter direction with respect to the average particle diameter (mm).
- the conductive particles of the present invention have an average compressive hardness of 5000 to 18000 N / mm 2 , preferably 6000 to 15000 N / mm 2 , and a compressibility of 20% or more at a compressibility of 20% or more and 50% or less.
- the ratio of the maximum value of the compressive hardness to the average value of the compressive hardness at 50% or less is 1.5 or more and 10 or less, preferably 2 or more and 8 or less, and particularly preferably 3 or more and 5 or less.
- the average value of the compression hardness at a compression rate of 20% or more and 50% or less is an average value of K values when the compression rates are 20%, 30%, 40%, and 50%.
- the connection resistance is low.
- the conductive particles have high connection reliability.
- the conductive particles of the present invention have the property of being hard at the initial stage of compression and exhibiting flexibility when further compressed. Therefore, they are formed on the electrodes at the initial stage when the electrodes are pressure-connected. It is possible to sufficiently eliminate the oxide film, and the connection resistance can be lowered. In addition, since it exhibits flexibility after pressure connection, the contact area with the electrodes can be maintained, and the connection reliability is also excellent.
- the conductive particles of the present invention are formed by forming a conductive layer on the surface of the core material particles.
- the core material particles may be inorganic or organic as long as they are in the form of particles, without particular limitation.
- the inorganic core material particles include metal particles such as gold, silver, copper, nickel, palladium, and solder, alloys, glass, ceramics, silica, metal or non-metal oxides (including hydrous substances), and aluminosilicates. Examples thereof include metal silicates, metal carbides, metal nitrides, metal carbonates, metal sulfates, metal phosphates, metal sulfides, metal acid salts, metal halides and carbons.
- examples of the organic core particles include thermoplastics such as natural fibers, natural resins, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylic acid ester, polyacrylic nitrile, polyacetal, ionomer, and polyester.
- thermoplastics such as natural fibers, natural resins, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylic acid ester, polyacrylic nitrile, polyacetal, ionomer, and polyester.
- examples thereof include resins, alkyd resins, phenol resins, urea resins, benzoguanamine resins, melamine resins, xylene resins, silicone resins, epoxy resins, diallyl phthalate resins and the like. These may be used alone or in combination of two or more.
- the core material particles may be made of a material made of both an inorganic substance and an organic substance instead of the material made of either the inorganic substance or the organic substance described above.
- the presence mode of the inorganic substance and the organic substance in the core material particles includes, for example, a core made of the inorganic substance and an inorganic substance covering the surface of the core material. Examples thereof include a core-shell type configuration in which a shell is provided, or a core made of an organic substance and a shell made of an inorganic substance covering the surface of the core are provided.
- a blend type structure in which an inorganic substance and an organic substance are mixed or randomly fused in one core material particle can be mentioned.
- the core material particles made of a material composed of both an inorganic substance and an organic substance the above-mentioned inorganic core material particles or the material constituting the organic core material particles can be used.
- the core material particles may be used so as to constitute each material of the inorganic substance and the organic substance independently, or may be used so as to form each of the inorganic substance and the organic substance in combination with two or more kinds of materials. ..
- the core material particles are preferably composed of a resin, and more preferably the resin is a thermoplastic resin.
- a core material made of such a material it is possible to improve the dispersion stability between particles, and it is possible to develop appropriate elasticity and enhance continuity at the time of electrical connection of an electronic circuit. ..
- the glass transition temperature is 200 ° C. or less, which means that the conductive particles tend to soften in the anisotropic conductive connection and the contact area becomes large, so that conduction can be easily obtained. Is preferable. From this viewpoint, when the core material particles have a glass transition temperature, the glass transition temperature is more preferably more than 100 ° C.
- the glass transition temperature can be determined, for example, as the intersection of the tangents of the original baseline and the inflection point at the baseline shift portion of the DSC curve obtained by differential scanning calorimetry (DSC).
- DSC differential scanning calorimetry
- the core material particles When an organic substance is used as the core material particles, when the organic substance is a highly crosslinked resin, the glass transition temperature is hardly observed even if the measurement is attempted to 200 ° C. by the above method.
- such particles are also referred to as particles having no glass transition point, and in the present invention, such core material particles may be used.
- the core material having no glass transition temperature as described above it is possible to obtain by copolymerizing the monomer constituting the organic substance exemplified above in combination with a crosslinkable monomer. it can.
- crosslinkable monomer examples include tetramethylene di (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, ethylene oxide di (meth) acrylate, and tetraethylene oxide.
- Examples thereof include silane-containing monomers, triallyl isocyanurate, diallyl phthalate, diallyl acrylamide, diallyl ether and the like.
- silane-containing monomers triallyl isocyanurate, diallyl phthalate, diallyl acrylamide, diallyl ether and the like.
- core material particles made of such a hard organic material are often used.
- the core material particles are spherical.
- the core material particles may have a shape other than a spherical shape, for example, a fibrous shape, a hollow shape, a plate shape, or a needle shape, and may have a large number of protrusions on the surface thereof or an irregular shape.
- spherical core material particles are preferable in terms of excellent filling property and easy coating of metal.
- the conductive layer formed on the surface of the core material particles is made of a conductive metal.
- the metals constituting the conductive layer include gold, platinum, silver, copper, iron, zinc, nickel, tin, lead, antimony, bismuth, cobalt, indium, titanium, antimony, bismuth, germanium, aluminum, chromium and palladium.
- metal compounds such as ITO and solder can be mentioned.
- gold, silver, copper, nickel, palladium or solder is preferable because of its low electrical resistance, and in particular, nickel, gold, nickel alloy or gold alloy is preferably used.
- the metal may be one kind, or two or more kinds may be used in combination.
- the conductive layer may have a single-layer structure or a laminated structure composed of a plurality of layers.
- the outermost layer is at least one selected from nickel, gold, silver, copper, palladium, nickel alloys, gold alloys, silver alloys, copper alloys and palladium alloys. ..
- the conductive layer may not cover the entire surface of the core material particles, or may cover only a part thereof. When only a part of the surface of the core material particles is coated, the coating portions may be continuous, for example, they may be discontinuously coated in an island shape.
- the thickness of the conductive layer is preferably 0.1 nm or more and 2000 nm or less, and more preferably 1 nm or more and 1500 nm or less.
- the thickness of the conductive layer can be measured by cutting the particles to be measured in two and observing the cross section of the cut end by SEM.
- the average particle size of the conductive particles is preferably 0.1 ⁇ m or more and 50 ⁇ m or less, and more preferably 1 ⁇ m or more and 30 ⁇ m or less.
- the average particle size of the metal-coated particles is within the above range, it is easy to secure continuity between the counter electrodes without causing a short circuit in a direction different from that between the counter electrodes.
- the average particle size of the conductive particles is a value measured using a scanning electron microscope (SEM). Specifically, the average particle size of the conductive particles is measured by the method described in Examples.
- the particle diameter is the diameter of a circular conductive particle image. When the conductive particles are not spherical, the particle diameter refers to the largest length (maximum length) of the line segments traversing the conductive particle image.
- the height of the protrusions is preferably 20 nm or more and 1000 nm or less, and more preferably 50 nm 800 nm or less.
- the number of protrusions depends on the particle size of the conductive particles, but the number of protrusions is preferably 1 or more and 20000 or less, and more preferably 5 or more and 5000 or less per conductive particle. It is advantageous in that the conductivity is further improved.
- the length of the base of the protrusion is preferably 5 nm or more and 1000 nm or less, and more preferably 10 nm or more and 800 nm or less.
- the length of the base of the protrusion refers to the length along the surface of the conductive particle at the site where the protrusion is formed when measured using an electron microscope image in a cross-sectional view of the particle, and the height of the protrusion is The shortest distance from the base of the protrusion to the apex of the protrusion. When one protrusion has a plurality of vertices, the highest vertex is defined as the height of the protrusion.
- the length of the base of the protrusion and the height of the protrusion shall be the arithmetic mean values measured for 20 different particles observed by an electron microscope.
- the shape of the conductive particles depends on the shape of the core material particles, but is not particularly limited.
- it may be fibrous, hollow, plate-shaped or needle-shaped, and may have a large number of protrusions on its surface or may be amorphous.
- the shape is spherical or has a large number of protrusions on the outer surface in terms of excellent filling property and connectivity.
- the shape since the shape has large protrusions on the outer surface, it tends to become conductive particles having a large compression hardness at the initial stage of compression.
- a dry method using a vapor deposition method, a sputtering method, a mechanochemical method, a hybridization method, etc., an electrolytic plating method, a wet method using an electroless plating method, etc. are used.
- a conductive layer may be formed on the surface of the core material particles by combining these methods.
- a conductive layer on the surface of the core material particles by an electroless plating method because it is easy to obtain conductive particles having a desired compressive hardness.
- the core material particles are surface-modified so that the surface has the ability to capture noble metal ions or has the ability to capture noble metal ions.
- the noble metal ion is preferably a palladium or silver ion. Having the ability to capture noble metal ions means that the noble metal ions can be captured as a chelate or a salt.
- the surface of the core material particles has an ability to capture noble metal ions.
- the surface is modified so as to have the ability to capture noble metal ions, for example, the method described in JP-A-61-64882 can be used.
- Such core material particles are used to support a noble metal on the surface thereof.
- the core material particles are dispersed in a dilute acidic aqueous solution of a precious metal salt such as palladium chloride or silver nitrate. This causes the noble metal ions to be captured on the surface of the particles.
- the concentration of the noble metal salt is sufficient in the range of 1 ⁇ 10 -7 to 1 ⁇ 10 ⁇ 2 mol per 1 m 2 of the surface area of the particles.
- the core material particles in which the noble metal ions are trapped are separated from the system and washed with water. Subsequently, the core material particles are suspended in water, and a reducing agent is added thereto to reduce the noble metal ions.
- the noble metal is carried on the surface of the core material particles.
- the reducing agent for example, sodium hypophosphite, sodium borohydride, potassium borohydride, dimethylamine borane, hydrazine, formalin and the like are used, and the reducing agent is selected based on the constituent material of the target conductive layer. It is preferable to be done.
- a sensitization treatment for adsorbing tin ions on the surface of the particles may be performed.
- the surface-modified core material particles may be put into an aqueous solution of stannous chloride and stirred for a predetermined time.
- the conductive layer is formed on the core material particles that have been pretreated in this way.
- the first step is an electroless nickel plating step of mixing an aqueous slurry of core material particles with an electroless nickel plating bath containing a dispersant, a nickel salt, a reducing agent, a complexing agent, and the like.
- autolysis of the plating bath occurs at the same time as the formation of the conductive layer on the core material particles. Since this autolysis occurs in the vicinity of the core material particles, the autolyzed material is trapped on the surface of the core material particles when the conductive layer is formed, so that the nuclei of microprojections are generated, and at the same time, the conductive layer is formed. Be done.
- the protrusion grows from the nucleus of the generated microprojection as a base point.
- the above-mentioned core material particles are sufficiently dispersed in water in the range of preferably 0.1 to 500 g / L, more preferably 1 to 300 g / L to prepare an aqueous slurry.
- the dispersion operation can be carried out by normal stirring, high speed stirring or by using a shear dispersion device such as a colloid mill or a homogenizer. Further, ultrasonic waves may be used in combination with the dispersion operation. If necessary, a dispersant such as a surfactant may be added in the dispersion operation.
- the aqueous slurry of the core material particles subjected to the dispersion operation is added to the electroless nickel plating bath containing the nickel salt, the reducing agent, the complexing agent, various additives, and the like, and the first step of the electroless plating is performed.
- Examples of the above-mentioned dispersant include nonionic surfactants, zwitterionic surfactants and / or water-soluble polymers.
- a nonionic surfactant a polyoxyalkylene ether-based surfactant such as polyethylene glycol, polyoxyethylene alkyl ether, or polyoxyethylene alkyl phenyl ether can be used.
- amphoteric ion surfactant betaine-based surfactants such as alkyldimethylacetate betaine, alkyldimethylcarboxymethyl acetate betaine, and alkyldimethylaminoacetate betaine can be used.
- the water-soluble polymer polyvinyl alcohol, polyvinylpyrrolidinone, hydroxyethyl cellulose and the like can be used. These dispersants can be used alone or in combination of two or more.
- the amount of the dispersant used depends on the type, but is generally 0.5 to 30 g / L with respect to the volume of the liquid (electroless nickel plating bath). In particular, when the amount of the dispersant used is in the range of 1 to 10 g / L with respect to the volume of the liquid (electroless nickel plating bath), it is preferable from the viewpoint of further improving the adhesion of the conductive layer.
- nickel salt for example, nickel chloride, nickel sulfate, nickel acetate or the like is used, and the concentration thereof is preferably in the range of 0.1 to 50 g / L.
- the reducing agent for example, the same one as that used for the reduction of the noble metal ion described above can be used, and the reducing agent is selected based on the constituent material of the target base film.
- a phosphorus compound for example, sodium hypophosphate
- its concentration is preferably in the range of 0.1 to 50 g / L.
- the complexing agent examples include carboxylic acids (salts) such as citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid or alkali metal salts and ammonium salts thereof, amino acids such as glycine, and amines such as ethylenediamine and alkylamine.
- carboxylic acids such as citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid or alkali metal salts and ammonium salts thereof, amino acids such as glycine, and amines such as ethylenediamine and alkylamine.
- Compounds that have a complexing effect on nickel ions such as acids, other ammonium, EDTA or pyrophosphate (salt), are used. These can be used alone or in combination of two or more.
- the concentration is preferably in the range of 1 to 100 g / L, more preferably 5 to 50 g / L.
- a first aqueous solution containing one of a nickel salt, a reducing agent and an alkali, and a second aqueous solution containing the remaining two are added.
- a first aqueous solution containing (ii) a nickel salt, a second aqueous solution containing a reducing agent, and a third aqueous solution containing an alkali are used, and these aqueous solutions are used simultaneously and over time.
- Electroless nickel plating is performed by adding to the liquid in one step. When these liquids are added, the plating reaction starts again, and the conductive layer formed can be controlled to a desired film thickness by adjusting the addition amount. After the addition of the electroless nickel plating solution is completed, the reaction is completed by continuing stirring while maintaining the liquid temperature for a while after the generation of hydrogen gas is completely not observed.
- first aqueous solution containing a nickel salt and a second aqueous solution containing a reducing agent and an alkali it is preferable to use a first aqueous solution containing a nickel salt and a second aqueous solution containing a reducing agent and an alkali, but the combination is not limited to this.
- the first aqueous solution does not contain a reducing agent and an alkali
- the second aqueous solution does not contain a nickel salt.
- nickel salt and the reducing agent those described above can be used.
- alkali for example, a hydroxide of an alkali metal such as sodium hydroxide or potassium hydroxide can be used. The same applies to the case of (ii) above.
- the first to third aqueous solutions contain nickel salts, reducing agents and alkalis, respectively, and each aqueous solution does not contain any other two components other than the component.
- the concentration of the nickel salt in the aqueous solution is preferably 10 to 1000 g / L, particularly preferably 50 to 500 g / L.
- the concentration of the reducing agent is preferably 100 to 1000 g / L, particularly preferably 100 to 800 g / L.
- a boron compound is used as the reducing agent, it is preferably 5 to 200 g / L, particularly preferably 10 to 100 g / L.
- hydrazine or a derivative thereof is used as the reducing agent, it is preferably 5 to 200 g / L, particularly preferably 10 to 100 g / L.
- the alkali concentration is preferably 5 to 500 g / L, particularly preferably 10 to 200 g / L.
- the second step is continuously performed after the completion of the first step, but instead of this, the first step and the second step may be performed intermittently.
- the core material particles and the plating solution are separated by a method such as filtration, and the core material particles are newly dispersed in water to prepare an aqueous slurry, and a complexing agent is prepared therein.
- the dispersant is preferably 0.5 to 30 g / L, more preferably 1 to 10 g / L.
- the conductive layer having a smooth surface can be formed by reducing the concentration of the nickel salt in the electroless nickel plating bath in the first step of the process of forming the conductive layer having the protrusions. That is, as the nickel salt, for example, nickel chloride, nickel sulfate, nickel acetate or the like is used, and the concentration thereof is preferably in the range of 0.01 to 0.5 g / L.
- a conductive layer having a smooth surface can be formed by the method of performing the first step and the second step other than reducing the concentration of the nickel salt in the electroless nickel plating bath.
- Sulfur compounds include 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzoimidazole, 2-mercapto-1-methylimidazole, thioglycolic acid, thiodiglycolic acid, cysteine, saccharin, thiamine nitrate, N, Sodium N-diethyl-dithiocarbamate, 1,3-diethyl-2-thiourea, dipyridine, N-thiazole-2-sulfamil amide, 1,2,3-benzotriazole-2-thiazolin-2-thiol, thiazole , Thiourea, ethylenethiourea, thiosol, sodium thioindoxylate, o-sulfonamide benzoic acid, sulfanic acid, acid orange,
- the amount of the sulfur compound used is preferably such that the total concentration of the sulfur compound in the electroless plating reaction solution is 0.01 mass ppm or more and 100 mass ppm or less, and is 0.1 mass ppm or more and 50 mass ppm or less. More preferably, it is an amount. If the amount of the sulfur compound used is too small, the effect of hardening the compressive hardness at the initial stage of compression is difficult to be exhibited, and if it is too large, the compressive hardness in the middle to late stages of compression becomes hard, which is not preferable.
- the time for adding the sulfur compound may be during the formation of the conductive layer, but it is preferably in the middle of the second step. In particular, it is preferable to start the addition 5 to 20 minutes after the start of the second step because it becomes easy to harden the compression hardness at the initial stage of compression.
- the entire amount of the sulfur compound may be added at one time, may be added in a plurality of times, or may be added continuously. However, if the entire amount is added at one time, the compression hardness at the initial stage of compression tends to be hardened. preferable.
- the addition time is preferably 30 seconds or less, more preferably 15 seconds or less, for example, when a 1 L reactor is used, although it depends on the scale of the reaction system.
- There is no lower limit to the addition time but it is usually 0.1 seconds or longer, or 0.5 seconds or longer.
- the sulfur compound in this range, it becomes easy to harden the compression hardness at the initial stage of compression.
- the protrusions tend to become large, so that the compression hardness at the initial stage of compression is further increased. The effect of hardening can be obtained. In this way, the conductive particles of the present invention can be obtained.
- the surface thereof may be further coated with an insulating resin in order to prevent short circuits between the conductive particles.
- the coating of the insulating resin is destroyed by the heat and pressure applied when the two electrodes are bonded together with a conductive adhesive so that the surface of the conductive particles is not exposed as much as possible when no pressure is applied. It is formed so that at least the protrusions on the surface of the conductive particles are exposed.
- the thickness of the insulating resin can be about 0.1 to 0.5 ⁇ m.
- the insulating resin may cover the entire surface of the conductive particles, or may only cover a part of the surface of the conductive particles.
- insulating resin those known in the technical field can be widely used.
- a chemical method such as a core precipitation method, an interfacial polymerization method, an insitu polymerization method and a liquid curing coating method, a spray drying method, and an air suspension coating method are used.
- a physico-mechanical method such as a method, a vacuum vapor deposition coating method, a dry blend method, a hybridization method, an electrostatic coalescence method, a melt dispersion cooling method and an inorganic encapsulation method, and a physicochemical method such as an interfacial precipitation method.
- the conductive particles of the present invention are used for connecting, for example, an anisotropic conductive film (ACF), a heat seal connector (HSC), or an electrode of a liquid crystal display panel to a circuit board of a driving LSI chip. It is suitably used as a conductive material or the like. In particular, the conductive particles of the present invention are suitably used as a conductive filler for a conductive adhesive.
- the conductive adhesive is disposed between two substrates on which a conductive substrate is formed, and is preferably used as an anisotropic conductive adhesive that adheres and conducts the conductive substrate by heating and pressurizing. ..
- This anisotropic conductive adhesive contains the conductive particles of the present invention and an adhesive resin.
- the adhesive resin can be used without particular limitation as long as it is insulating and is used as an adhesive resin. It may be either a thermoplastic resin or a thermosetting resin, and it is preferable that the adhesive performance is exhibited by heating.
- Such adhesive resins include, for example, a thermoplastic type, a thermosetting type, an ultraviolet curable type and the like.
- thermosetting type a composite type of a thermosetting type and an ultraviolet curable type, which show intermediate properties between a thermoplastic type and a thermosetting type.
- adhesive resins can be appropriately selected according to the surface characteristics of the circuit board or the like to be adhered and the usage pattern.
- an adhesive resin composed of a thermosetting resin is preferable because it has excellent material strength after bonding.
- the adhesive resin examples include ethylene-vinyl acetate copolymer, carboxyl-modified ethylene-vinyl acetate copolymer, ethylene-isobutyl acrylate copolymer, polyamide, polyimide, polyester, polyvinyl ether, polyvinyl butyral, and polyurethane.
- SBS block copolymer carboxyl-modified SBS copolymer, SIS copolymer, SEBS copolymer, maleic acid-modified SEBS copolymer, polybutadiene rubber, chloroprene rubber, carboxyl-modified chloroprene rubber, styrene-butadiene rubber, isobutylene- One or two selected from isoprene copolymer, acrylonitrile-butadiene rubber (hereinafter referred to as NBR), carboxyl-modified NBR, amine-modified NBR, epoxy resin, epoxy ester resin, acrylic resin, phenol resin, silicone resin, etc. Examples thereof include those prepared by using the one obtained by the above combination as a main agent.
- thermoplastic resin styrene-butadiene rubber, SEBS, etc. are preferable because they have excellent reworkability.
- thermosetting resin an epoxy resin is preferable. Of these, epoxy resin is most preferable because it has high adhesive strength, excellent heat resistance and electrical insulation, low melt viscosity, and can be connected at low pressure.
- epoxy resin a generally used epoxy resin can be used as long as it is a multivalent epoxy resin having two or more epoxy groups in one molecule.
- specific examples include novolac resins such as phenol novolac and cresol novolac, polyhydric phenols such as bisphenol A, bisphenol F, bisphenol AD, resorcin, and bishydroxydiphenyl ether, ethylene glycol, neopentyl glycol, glycerin, and trimethylolpropane.
- Polyhydric alcohols such as polypropylene glycol, polyamino compounds such as ethylenediamine, triethylenetetramine, aniline, polyhydric carboxy compounds such as adipic acid, phthalic acid, isophthalic acid, etc., and epichlorohydrin or 2-methylepicrolhydrin.
- a glycidyl type epoxy resin is exemplified. Examples thereof include aliphatic and alicyclic epoxy resins such as dicyclopentadiene epoxiside and butadiene dimer epoxiside. These can be used alone or in admixture of two or more.
- the amount of the conductive particles of the present invention used in the anisotropic conductive adhesive is usually 0.1 to 30 parts by mass, preferably 0.5 to 25 parts by mass, and more preferably 1 with respect to 100 parts by mass of the adhesive resin component. ⁇ 20 parts by mass.
- the amount of the conductive particles used is within this range, it is possible to suppress an increase in connection resistance and melt viscosity, improve connection reliability, and sufficiently secure anisotropy of connection.
- additives known in the art can be added to the anisotropic conductive adhesive.
- the blending amount can also be within the range known in the art.
- Other additives include, for example, tackifiers, reactive aids, epoxy resin hardeners, metal oxides, photoinitiators, sensitizers, hardeners, vulcanizers, deterioration inhibitors, heat resistant additives, heat. Examples thereof include conduction improvers, softeners, colorants, various coupling agents, and metal deactivators.
- tackifier examples include rosin, rosin derivative, terpene resin, terpenephenol resin, petroleum resin, kumaron-inden resin, styrene resin, isoprene resin, alkylphenol resin, xylene resin and the like.
- reactive auxiliary agent examples include polyols, isocyanates, melamine resins, urea resins, utropines, amines, acid anhydrides, and peroxides.
- the epoxy resin curing agent can be used without particular limitation as long as it has two or more active hydrogens in one minute.
- polyamino compounds such as diethylenetriamine, triethylenetetramine, metaphenylenediamine, dicyandiamide, and polyamideamine
- organic acid anhydrides such as phthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and pyromellitic anhydride.
- Novolac resins such as phenol novolac and cresol novolak can be mentioned. These can be used alone or in admixture of two or more. In addition, a latent curing agent may be used if necessary.
- latent curing agent examples include imidazole-based, hydrazide-based, boron trifluoride-amine complex, sulfonium salt, amineimide, polyamine salt, dicyandiamide and the like, and modified products thereof. These can be used alone or as a mixture of two or more.
- the anisotropic conductive adhesive is manufactured using a manufacturing apparatus usually used in the technical field.
- the conductive particles and adhesive resin of the present invention, and if necessary, a curing agent and various additives are blended, and when the adhesive resin is a thermosetting resin, it is mixed in an organic solvent to obtain a thermoplastic resin.
- the adhesive resin is a thermosetting resin, it is mixed in an organic solvent to obtain a thermoplastic resin.
- it is produced by melt-kneading at a temperature equal to or higher than the softening point of the adhesive resin, specifically preferably at about 50 to 130 ° C., and more preferably at about 60 to 110 ° C.
- the anisotropic conductive adhesive thus obtained may be applied or may be applied in the form of a film.
- K value Compressive hardness
- MCTM-500 microcompression tester
- X% K value Average particle size 200 particles are arbitrarily extracted from the scanning electron microscope (SEM) photograph to be measured, the particle size is measured at a magnification of 10000 times, and the arithmetic mean value is taken as the average particle size. did.
- Example 1 Pretreatment Spherical benzoguanamine-based hard resin particles having an average particle diameter of 3.0 ⁇ m were used as core particles. 9 g of the solution was added to a 200 mL aqueous conditioner solution (“Cleaner Conditioner 231” manufactured by Roam & Haas Electronic Materials) with stirring. The concentration of the conditioner aqueous solution was 40 mL / L. Subsequently, the surface of the core material particles was modified and dispersed by stirring for 30 minutes while applying ultrasonic waves at a liquid temperature of 60 ° C. This aqueous solution was filtered, and the core material particles washed once with ripulp water were made into a 200 mL slurry.
- aqueous conditioner solution (“Cleaner Conditioner 231” manufactured by Roam & Haas Electronic Materials) with stirring. The concentration of the conditioner aqueous solution was 40 mL / L.
- the surface of the core material particles was modified and dispersed by stirring for 30 minutes while applying ultrasonic waves
- stannous chloride 0.1 g was added to this slurry.
- the mixture was stirred at room temperature for 5 minutes to perform a sensitization treatment in which tin ions were adsorbed on the surface of the core material particles.
- this aqueous solution was filtered, and the core material particles washed once with water were made into a 200 mL slurry and maintained at 60 ° C. 1.5 mL of a 0.11 mol / L palladium chloride aqueous solution was added to this slurry.
- the mixture was stirred at 60 ° C. for 5 minutes to perform an activation treatment in which palladium ions were trapped on the surface of the core material particles.
- this aqueous solution was filtered, and the core material particles washed once with hot water were made into a 100 mL slurry, 10 mL of 0.5 g / L dimethylamine borane aqueous solution was added, and the mixture was stirred for 2 minutes while giving ultrasonic waves to the pretreated core material. A slurry of particles was obtained.
- a non-electrolytic nickel-phosphorus plating bath 3L consisting of an aqueous solution in which polyethylene glycol was dissolved was prepared and heated to 70 ° C.
- Electroless plating treatment It was confirmed that the slurry of the pretreated core material particles was put into this electroless plating bath and stirred for 5 minutes to stop the foaming of hydrogen.
- 420 mL of a 224 g / L nickel sulfate aqueous solution and 420 mL of a mixed aqueous solution containing 210 g / L of sodium hypophosphite and 80 g / L of sodium hydroxide were quantified at a rate of addition of 2.5 mL / min. Electroless plating was started by continuously separating and adding by a pump.
- the average particle size of the obtained conductive particles was 3.22 ⁇ m, the thickness of the conductive layer was 110 nm, and the conductive particles had large protrusions.
- the SEM image is shown in FIG.
- the obtained conductive particles showed the highest compressive hardness at a compressibility of 3%.
- Table 1 shows the compression hardness at each compression rate.
- Example 2 In Example 1, conductive particles were produced by the same method as in Example 1 except that (3) 2-mercaptobenzoxazole was added instead of 2-mercaptobenzothiazole in the electroless plating treatment.
- the average particle size of the obtained conductive particles was 3.22 ⁇ m, the thickness of the conductive layer was 110 nm, and the conductive particles had large protrusions.
- the obtained conductive particles showed the highest compressive hardness at a compressibility of 3%. Table 1 shows the compression hardness at each compression rate.
- Example 3 In Example 1, the production of conductive particles was carried out in the same manner as in Example 1 except that (2) the concentration of nickel sulfate hexahydrate prepared in the plating bath was changed from 2 g / L to 0.1 g / L. went. The average particle size of the obtained conductive particles was 3.22 ⁇ m, the thickness of the conductive layer was 110 nm, and the shape was smooth without protrusions. The obtained conductive particles showed the highest compressive hardness at a compressibility of 3%. Table 1 shows the compression hardness at each compression rate.
- stannous chloride 0.1 g was added to this slurry.
- the mixture was stirred at room temperature for 5 minutes to perform a sensitization treatment in which tin ions were adsorbed on the surface of the core material particles.
- this aqueous solution was filtered, and the core material particles washed once with water were made into a 200 mL slurry and maintained at 60 ° C. 1.5 mL of a 0.11 mol / L palladium chloride aqueous solution was added to this slurry.
- the mixture was stirred at 60 ° C. for 5 minutes to perform an activation treatment in which palladium ions were trapped on the surface of the core material particles.
- this aqueous solution was filtered, and the core material particles washed once with hot water were made into a 100 mL slurry, 10 mL of 0.5 g / L dimethylamine borane aqueous solution was added, and the mixture was stirred for 2 minutes while giving ultrasonic waves to the pretreated core material. A slurry of particles was obtained.
- a non-electrolytic nickel-phosphorus plating bath 3L consisting of an aqueous solution in which polyethylene glycol was dissolved was prepared and heated to 70 ° C.
- stannous chloride 0.1 g was added to this slurry.
- the mixture was stirred at room temperature for 5 minutes to perform a sensitization treatment in which tin ions were adsorbed on the surface of the core material particles.
- this aqueous solution was filtered, and the core material particles washed once with water were made into a 200 mL slurry and maintained at 60 ° C. 1.5 mL of a 0.11 mol / L palladium chloride aqueous solution was added to this slurry.
- the mixture was stirred at 60 ° C. for 5 minutes to perform an activation treatment in which palladium ions were trapped on the surface of the core material particles.
- this aqueous solution was filtered, and the core material particles washed once with hot water were made into a 100 mL slurry, 10 mL of 0.5 g / L dimethylamine borane aqueous solution was added, and the mixture was stirred for 2 minutes while giving ultrasonic waves to the pretreated core material. A slurry of particles was obtained.
- Electroless plating treatment It was confirmed that the slurry of the pretreated core material particles was put into this electroless plating bath and stirred for 5 minutes to stop the foaming of hydrogen.
- 420 mL of a 224 g / L nickel sulfate aqueous solution and 420 mL of a mixed aqueous solution containing 210 g / L of sodium hypophosphite and 80 g / L of sodium hydroxide were quantified at a rate of addition of 2.5 mL / min. Electroless plating was started by continuously separating and adding by a pump.
- connection resistance and connection reliability were evaluated by the following methods.
- An insulating adhesive obtained by mixing 100 parts by mass of an epoxy resin, 150 parts by mass of a curing agent and 70 parts by mass of toluene is mixed with 15 parts by mass of coated particles obtained in Examples and Comparative Examples to obtain an insulating paste. It was. This paste was applied onto a silicone-treated polyester film using a bar coater, and then the paste was dried to form a thin film on the film.
- the obtained thin film-forming film is placed between a glass substrate on which aluminum is vapor-deposited on the entire surface and a polyimide film substrate on which a copper pattern is formed at a pitch of 50 ⁇ m to prepare a sample for measuring conduction resistance and perform electricity.
- the connection was made, and the connection resistance value of this sample was measured at room temperature (25 ° C., 50% RH). It can be evaluated that the lower the connection resistance value, the better the connection resistance of the conductive particles.
- the results are shown in Table 2.
- the samples for measuring conduction resistance were arranged in a closed container, and a pressure cooker test was conducted in which the samples were treated in an environment of a temperature of 121 ° C., a relative humidity of 100%, and 2 atm for 10 hours.
- connection resistance value of the sample was measured at room temperature (25 ° C., 50% RH). It can be evaluated that the smaller the difference in the connection resistance value before and after the pressure cooker test, the higher the connection reliability of the conductive particles. The results are shown in Table 2.
- the conductive particles obtained in Examples 1 to 3 have a lower resistance value than the conductive particles obtained in Comparative Examples 1 and 2. Further, it can be seen that the conductive particles obtained in Examples 1 to 3 maintain good conductivity without an increase in the connection resistance value even after the pressure cooker test.
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Abstract
Description
本発明における圧縮硬さとは、微小圧縮試験機(例えば、島津製作所製MCTM-500)を用いて、負荷速度2.23mN/秒で半径R(mm)の導電性粒子に荷重を与えたときの及び荷重値F(N)を測定し、下記式により求めた値である。
圧縮硬さ(N/mm2)=(3/√2)×F×S-3/2×R-1/2
ここで、導電性粒子の半径R(mm)は、後述する平均粒子径から算出した値であり、圧縮率とは、粒子径方向の長さの変化率であり、平均粒子径(mm)に対する圧縮変位S(mm)の割合である。
ここで、圧縮率20%以上50%以下における圧縮硬さの平均値とは、圧縮率20%、30%、40%及び50%の場合のK値の平均値である。
前記芯材粒子としては、粒子状であれば、無機物であっても有機物であっても特に制限なく用いることができる。無機物の芯材粒子としては、金、銀、銅、ニッケル、パラジウム、ハンダ等の金属粒子、合金、ガラス、セラミック、シリカ、金属又は非金属の酸化物(含水物も含む)、アルミノ珪酸塩を含む金属珪酸塩、金属炭化物、金属窒化物、金属炭酸塩、金属硫酸塩、金属リン酸塩、金属硫化物、金属酸塩、金属ハロゲン化物及び炭素等が挙げられる。一方、有機物の芯材粒子としては、例えば、天然繊維、天然樹脂、ポリエチレン、ポリプロピレン、ポリ塩化ビニル、ポリスチレン、ポリブテン、ポリアミド、ポリアクリル酸エステル、ポリアクリルニトリル、ポリアセタール、アイオノマー、ポリエステル等の熱可塑性樹脂、アルキッド樹脂、フェノール樹脂、尿素樹脂、ベンゾグアナミン樹脂、メラミン樹脂、キシレン樹脂、シリコーン樹脂、エポキシ樹脂、ジアリルフタレート樹脂等が挙げられる。これらは単独で使用してもよいし、2種以上を組み合わせて使用してもよい。
また導電層は、芯材粒子の表面全体を被覆していなくてもよく、その一部のみを被覆していてもよい。芯材粒子の表面の一部のみを被覆している場合は、被覆部位が連続していてもよく、例えばアイランド状に不連続に被覆していてもよい。
導電層の厚みは、0.1nm以上2000nm以下であることが好ましく、1nm以上1500nm以下であることがより好ましい。導電性粒子が後述する突起を有する場合、突起の高さは、ここでいう導電層の厚みに含まないものとする。なお、本発明において、導電層の厚みは、測定対象の粒子を2つに切断し、その切り口の断面をSEM観察して測定することができる。
無電解めっき法により芯材粒子の表面に導電層を形成する場合、芯材粒子は、その表面が貴金属イオンの捕捉能を有するか、又は貴金属イオンの捕捉能を有するように表面改質されることが好ましい。貴金属イオンは、パラジウムや銀のイオンであることが好ましい。貴金属イオンの捕捉能を有するとは、貴金属イオンをキレート又は塩として捕捉し得ることをいう。例えば芯材粒子の表面に、アミノ基、イミノ基、アミド基、イミド基、シアノ基、水酸基、ニトリル基、カルボキシル基などが存在する場合には、該芯材粒子の表面は貴金属イオンの捕捉能を有する。貴金属イオンの捕捉能を有するように表面改質する場合には、例えば特開昭61-64882号公報記載の方法を用いることができる。
第1工程は、芯材粒子の水性スラリーと、分散剤、ニッケル塩、還元剤及び錯化剤などを含んだ無電解ニッケルめっき浴とを混合する無電解ニッケルめっき工程である。かかる第1工程では、芯材粒子上への導電層の形成と同時にめっき浴の自己分解が起こる。この自己分解は、芯材粒子の近傍で生じるため、導電層の形成時に自己分解物が芯材粒子表面上に捕捉されることによって、微小突起の核が生成し、それと同時に導電層の形成がなされる。生成した微小突起の核を基点として、突起部が成長する。
表面が平滑な導電層の形成は、上記突起部を有する導電層を形成する処理の第1工程における無電解ニッケルめっき浴中のニッケル塩の濃度を薄くすることで行うことができる。すなわち、ニッケル塩としては、例えば塩化ニッケル、硫酸ニッケル又は酢酸ニッケルなどが用いられ、その濃度を好ましくは0.01~0.5g/Lの範囲とする。無電解ニッケルめっき浴中のニッケル塩の濃度を薄くすること以外の上記第1工程、及び第2工程を行う方法により、表面が平滑な導電層を形成できる。
硫黄化合物としては、2-メルカプトベンゾチアゾール、2-メルカプトベンゾオキサゾール、2-メルカプトベンゾイミダゾール、2-メルカプト-1-メチルイミダゾール、チオグリコール酸、チオジグリコール酸、システイン、サッカリン、チアミン硝酸塩、N,N-ジエチル-ジチオカルバミン酸ナトリウム、1,3-ジエチル-2-チオ尿素、ジピリジン、N-チアゾール-2-スルファミルアマイド、1,2,3-ベンゾトリアゾール-2-チアゾリン-2-チオール、チアゾール、チオ尿素、エチレンチオ尿素、チオゾール、チオインドキシル酸ナトリウム、o-スルホンアミド安息香酸、スルファニル酸、アシッドオレンジ、メチルオレンジ、ナフチオン酸、ナフタレン-α-スルホン酸、1-ナフトール-4-スルホン酸、シェファー酸、サルファダイアジン、チオシアン酸アンモニウム、チオシアン酸カリウム、チオシアン酸ナトリウム、ロダニン、硫化アンモニウム、硫化ナトリウム、硫酸アンモニウム等が挙げられる。これらの硫黄化合物は、1種又は2種以上を組み合わせて用いることができる。硫黄化合物の使用量は、無電解めっき反応液中の全硫黄化合物濃度が0.01質量ppm以上100質量ppm以下となる量であることが好ましく、0.1質量ppm以上50質量ppm以下となる量であることがより好ましい。硫黄化合物の使用量が少なすぎると、圧縮初期の圧縮硬さを硬くする効果が発現しにくく、多すぎると圧縮中期から後期の圧縮硬さが硬くなってしまい好ましくない。
硫黄化合物を一度に全量添加する方法の場合、反応系の規模にもよるが、例えば1Lの反応器を使用した場合、その添加時間は30秒以下、更には15秒以下であることが好ましい。添加時間に下限はないが、通常は0.1秒以上、又は0.5秒以上である。この範囲で硫黄化合物を添加することにより、圧縮初期の圧縮硬さを硬くしやすくなる。
本発明においては、前記した突起部を有する導電層を形成する処理で、このような方法で硫黄化合物の添加を行うことにより、突起部が大きくなりやすくなるため、さらに圧縮初期の圧縮硬さを硬くする効果を得ることができる。
このようにして、本発明の導電性粒子が得られる。
(1)導電性粒子の圧縮硬さ(K値)
微小圧縮試験機(株式会社島津製作所製、MCTM-500)を用いて上述の方法によりK値を求めた。
また、圧縮率がX%のときのK値を「X%K値」と表記する場合がある。
(2)平均粒子径
測定対象の走査型電子顕微鏡(SEM)写真から、任意に200個の粒子を抽出して、倍率10000倍にて粒子径を測定し、その算術平均値を平均粒子径とした。
(1)前処理
平均粒子径3.0μmの球状ベンゾグアナミン系硬質樹脂粒子を芯材粒子として用いた。その9gを、200mLのコンディショナー水溶液(ローム・アンド・ハース電子材料製の「クリーナーコンディショナー231」)に攪拌しながら投入した。コンディショナー水溶液の濃度は40mL/Lであった。引き続き、液温60℃で超音波を与えながら30分間攪拌して芯材粒子の表面改質及び分散処理を行った。この水溶液を濾過し、一回リパルプ水洗した芯材粒子を200mLのスラリーにした。このスラリーへ塩化第一錫0.1gを投入した。常温で5分間攪拌し、錫イオンを芯材粒子の表面に吸着させる感受性化処理を行った。引き続きこの水溶液を濾過し、一回リパルプ水洗した芯材粒子を200mLのスラリーにして60℃に維持した。このスラリーへ0.11mol/Lの塩化パラジウム水溶液1.5mLを投入した。60℃で5分間撹拌し、パラジウムイオンを芯材粒子の表面に捕捉させる活性化処理を行った。引き続きこの水溶液を濾過し、一回リパルプ湯洗した芯材粒子を100mLのスラリーにし、0.5g/Lジメチルアミンボラン水溶液10mLを加え、超音波を与えながら2分間撹拌して前処理済み芯材粒子のスラリーを得た。
5g/Lの酒石酸ナトリウム、2g/Lの硫酸ニッケル六水和物、10g/Lのクエン酸3ナトリウム、0.1g/Lの次亜リン酸ナトリウム、及び2g/Lのポリエチレングリコールを溶解した水溶液からなる無電解ニッケル-リンめっき浴3Lを調製し、70℃に昇温した。
この無電解めっき浴に、前記前処理済み芯材粒子のスラリーを投入し、5分間攪拌して水素の発泡が停止するのを確認した。
このスラリーに、224g/Lの硫酸ニッケル水溶液420mLと、210g/Lの次亜リン酸ナトリウム及び80g/Lの水酸化ナトリウムを含む混合水溶液420mLを、添加速度はいずれも2.5mL/分として定量ポンプによって連続的に分別添加し、無電解めっきを開始した。開始してから10分後に、最終的に得られる液中の濃度が7.5質量ppmとなるように2-メルカプトベンゾチアゾールを1秒で加え、開始してから40分後に前記の2種類の水溶液の添加速度をいずれも4.7mL/分とした。硫酸ニッケル水溶液と、次亜リン酸ナトリウム及び水酸化ナトリウムの混合水溶液のそれぞれ全量を添加した後、70℃の温度を保持しながら5分間攪拌を継続した。次いで液を濾過し、濾過物を3回洗浄した後、110℃の真空乾燥機で乾燥して、ニッケル-リン合金からなる導電層を有する導電性粒子を得た。得られた導電性粒子の平均粒子径は3.22μm、導電層の厚みは110nmであり大きな突起部を有していた。SEM画像を図1に示す。得られた導電性粒子は、圧縮率3%で圧縮硬さが最高値を示した。各圧縮率での圧縮硬さを表1に示す。
実施例1において、(3)無電解めっき処理の2-メルカプトベンゾチアゾールに代えて2-メルカプトベンゾオキサゾールを加えること以外は実施例1と同じ方法で導電性粒子の製造を行った。得られた導電性粒子の平均粒子径は3.22μm、導電層の厚みは110nmであり大きな突起部を有していた。得られた導電性粒子は、圧縮率3%で圧縮硬さが最高値を示した。各圧縮率での圧縮硬さを表1に示す。
実施例1において、(2)めっき浴の調製の硫酸ニッケル六水和物の濃度を2g/Lから0.1g/Lに変更したこと以外は実施例1と同じ方法で導電性粒子の製造を行った。得られた導電性粒子の平均粒子径は3.22μm、導電層の厚みは110nmであり、突起部を有しない平滑な形状であった。得られた導電性粒子は、圧縮率3%で圧縮硬さが最高値を示した。各圧縮率での圧縮硬さを表1に示す。
(1)前処理
平均粒子径3.0μmの球状ベンゾグアナミン系硬質樹脂粒子を芯材粒子として用いた。その9gを、200mLのコンディショナー水溶液(ローム・アンド・ハース電子材料製の「クリーナーコンディショナー231」)に攪拌しながら投入した。コンディショナー水溶液の濃度は40mL/Lであった。引き続き、液温60℃で超音波を与えながら30分間攪拌して芯材粒子の表面改質及び分散処理を行った。この水溶液を濾過し、一回リパルプ水洗した芯材粒子を200mLのスラリーにした。このスラリーへ塩化第一錫0.1gを投入した。常温で5分間攪拌し、錫イオンを芯材粒子の表面に吸着させる感受性化処理を行った。引き続きこの水溶液を濾過し、一回リパルプ水洗した芯材粒子を200mLのスラリーにして60℃に維持した。このスラリーへ0.11mol/Lの塩化パラジウム水溶液1.5mLを投入した。60℃で5分間撹拌し、パラジウムイオンを芯材粒子の表面に捕捉させる活性化処理を行った。引き続きこの水溶液を濾過し、一回リパルプ湯洗した芯材粒子を100mLのスラリーにし、0.5g/Lジメチルアミンボラン水溶液10mLを加え、超音波を与えながら2分間撹拌して前処理済み芯材粒子のスラリーを得た。
5g/Lの酒石酸ナトリウム、2g/Lの硫酸ニッケル六水和物、10g/Lのクエン酸3ナトリウム、0.1g/Lの次亜リン酸ナトリウム、及び2g/Lのポリエチレングリコールを溶解した水溶液からなる無電解ニッケル-リンめっき浴3Lを調製し、70℃に昇温した。
(3)無電解めっき処理
このスラリーに、224g/Lの硫酸ニッケル水溶液420mLと、210g/Lの次亜リン酸ナトリウム及び80g/Lの水酸化ナトリウムを含む混合水溶液420mLを、添加速度はいずれも2.5mL/分として定量ポンプによって連続的に分別添加し、無電解めっきを開始した。硫酸ニッケル水溶液と、次亜リン酸ナトリウム及び水酸化ナトリウムの混合水溶液のそれぞれ全量を添加した後、70℃の温度を保持しながら5分間攪拌を継続した。次いで液を濾過し、濾過物を3回洗浄した後、110℃の真空乾燥機で乾燥して、ニッケル-リン合金からなる導電層を有する導電性粒子を得た。得られた導電性粒子の平均粒子径は3.22μm、導電層の厚みは110nmであり突起部を有していた。また、得られた導電性粒子は、圧縮率4%で圧縮硬さが最高値を示した。各圧縮率での圧縮硬さを表1に示す。
(1)前処理
平均粒径3.0μmの球状ベンゾグアナミン系硬質樹脂粒子を芯材粒子として用いた。その9gを、200mLのコンディショナー水溶液(ローム・アンド・ハース電子材料製の「クリーナーコンディショナー231」)に攪拌しながら投入した。コンディショナー水溶液の濃度は40mL/Lであった。引き続き、液温60℃で超音波を与えながら30分間攪拌して芯材粒子の表面改質及び分散処理を行った。この水溶液を濾過し、一回リパルプ水洗した芯材粒子を200mLのスラリーにした。このスラリーへ塩化第一錫0.1gを投入した。常温で5分間攪拌し、錫イオンを芯材粒子の表面に吸着させる感受性化処理を行った。引き続きこの水溶液を濾過し、一回リパルプ水洗した芯材粒子を200mLのスラリーにして60℃に維持した。このスラリーへ0.11mol/Lの塩化パラジウム水溶液1.5mLを投入した。60℃で5分間撹拌し、パラジウムイオンを芯材粒子の表面に捕捉させる活性化処理を行った。引き続きこの水溶液を濾過し、一回リパルプ湯洗した芯材粒子を100mLのスラリーにし、0.5g/Lジメチルアミンボラン水溶液10mLを加え、超音波を与えながら2分間撹拌して前処理済み芯材粒子のスラリーを得た。
5g/Lの酒石酸ナトリウム、2g/Lの硫酸ニッケル六水和物、10g/Lのクエン酸3ナトリウム、0.1g/Lの次亜リン酸ナトリウム、及び2g/Lのポリエチレングリコールを溶解した水溶液からなる無電解ニッケル-リンめっき浴3Lを調製し、最終的に得られる液中の濃度が7.5質量ppmとなるように2-メルカプトベンゾチアゾールを添加して70℃に昇温した。
この無電解めっき浴に、前記前処理済み芯材粒子のスラリーを投入し、5分間攪拌して水素の発泡が停止するのを確認した。
このスラリーに、224g/Lの硫酸ニッケル水溶液420mLと、210g/Lの次亜リン酸ナトリウム及び80g/Lの水酸化ナトリウムを含む混合水溶液420mLを、添加速度はいずれも2.5mL/分として定量ポンプによって連続的に分別添加し、無電解めっきを開始した。硫酸ニッケル水溶液と、次亜リン酸ナトリウム及び水酸化ナトリウムの混合水溶液のそれぞれ全量を添加した後、70℃の温度を保持しながら5分間攪拌を継続した。次いで液を濾過し、濾過物を3回洗浄した後、110℃の真空乾燥機で乾燥して、ニッケル-リン合金皮膜を有する導電性粒子を得た。得られた導電性粒子の平均粒子径は3.05μm、導電層の厚みは25nmであり突起部を有していた。また、得られた導電性粒子は、圧縮率5%で圧縮硬さが最高値を示した。各圧縮率での圧縮硬さを表1に示す。
実施例及び比較例の導電性粒子を用いて、接続抵抗性及び接続信頼性の評価を以下の方法で行った。
エポキシ樹脂100質量部、硬化剤150質量部及びトルエン70質量部を混合した絶縁性接着剤と、実施例及び比較例で得られた被覆粒子15質量部とを混合して、絶縁性ペーストを得た。このペーストをシリコーン処理ポリエステルフィルム上にバーコーターを用いて塗布し、その後、ペーストを乾燥させて、フィルム上に薄膜を形成した。得られた薄膜形成フィルムを、全面がアルミニウムを蒸着させたガラス基板と、銅パターンが50μmピッチに形成されたポリイミドフィルム基板との間に配して、導通抵抗測定用のサンプルを作製して電気接続を行い、このサンプルの接続抵抗値を室温下(25℃・50%RH)で測定した。接続抵抗値が低いほど導電性粒子の接続抵抗性が優れているものと評価できる。結果を表2に示す。
また、前記導通抵抗測定用のサンプルを密閉容器に並べ、温度121℃、相対湿度100%、2気圧の環境下で10時間処理するプレッシャークッカーテストを行った。プレッシャークッカーテスト後、サンプルの接続抵抗値を室温下(25℃・50%RH)で測定した。プレッシャークッカーテスト前後の接続抵抗値の差が小さいほど導電性粒子の接続信頼性が高いものであると評価できる。結果を表2に示す。
Claims (10)
- 芯材粒子の表面に導電層が形成されてなる導電性粒子において、
前記導電性粒子の圧縮硬さの最高値が24000N/mm2以上であり、かつ、圧縮率5%未満で圧縮硬さが最高値を示し、
圧縮率20%以上50%以下における圧縮硬さの平均値が5000~18000N/mm2であって、
圧縮率20%以上50%以下における圧縮硬さの平均値に対する、圧縮硬さの最高値の比が1.5以上10以下である導電性粒子。 - 圧縮率30%のときの圧縮硬さに対する、圧縮率2%のときの圧縮硬さの比が1.5以上10以下である請求項1に記載の導電性粒子。
- 前記導電層の厚みが0.1nm以上2000nm以下である請求項1又は2に記載の導電性粒子。
- 外表面に突起を有する請求項1~3のいずれか1項に記載の導電性粒子。
- 外表面が平滑である請求項1~3のいずれか1項に記載の導電性粒子。
- 請求項1~5のいずれか1項に記載の導電性粒子と絶縁性樹脂とを含む導電性材料。
- 無電解めっきにより芯材粒子の表面に導電層を形成する導電性粒子の製造方法であって、前記導電層の形成中に無電解めっき反応液に硫黄化合物を添加する工程を有する導電性粒子の製造方法。
- 前記硫黄化合物が、2-メルカプトベンゾチアゾール、2-メルカプトベンゾオキサゾール及び2-メルカプトベンゾイミダゾールからなる群より選択される少なくとも1種である請求項7に記載の導電性粒子の製造方法。
- 硫黄化合物の添加を30秒以内で行う請求項7又は8に記載の導電性粒子の製造方法。
- 前記硫黄化合物の添加量が、無電解めっき反応液中の全硫黄化物濃度が0.01ppm以上500ppm以下となる量である請求項7~9のいずれか1項に記載の導電性粒子の製造方法。
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