WO2021235435A1

WO2021235435A1 - Electrically conductive particle, and electrically conductive material and connection structure obtained using same

Info

Publication number: WO2021235435A1
Application number: PCT/JP2021/018786
Authority: WO
Inventors: 哲高橋; 直也田杉; 智真成橋
Original assignee: 日本化学工業株式会社
Priority date: 2020-05-20
Filing date: 2021-05-18
Publication date: 2021-11-25
Also published as: KR20230011946A; CN115667580A; TW202219318A

Abstract

The present invention provides an electrically conductive particle which exhibits excellent storage stability, excellent corrosion resistance and low connection resistance, and in which a nickel plating layer is formed as an electrically conductive layer on the surface of a core particle. The molar ratio of the amount of carbon relative to the total amount of nickel and phosphorus (C/(Ni+P)) or the molar ratio of the amount of carbon relative to nickel and boron (C/(Ni+B)) is 0.0002-1.65, the molar ratio of the amount of oxygen relative to the total amount of nickel and phosphorus (O/(Ni+P)) or the molar ratio of the amount of oxygen relative to the total amount of nickel and boron (O/(Ni+B)) is 0.0001-1.8, and the molar ratio of phosphorus relative to nickel (P/Ni) or the molar ratio of boron relative to nickel (B/Ni) is 0.003-0.7 in a region within 5 nm in the depth direction from a surface of the electrically conductive layer, as measured using a scanning Auger electron spectroscope.

Description

Conductive particles, conductive materials and connecting structures using them

The present invention relates to conductive particles, a conductive material containing the conductive particles, and a connection structure using the same.

As 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 an electrical connection between the electrodes and wiring.

Nickel plating film by electroless plating method is often used as the conductive layer of these conductive particles, but various measures have been taken to develop the desired characteristics. As an example, Patent Document 1 describes treating the surface of conductive particles with a treatment liquid containing a radically polymerizable compound, an acidic compound and water in order to obtain conductive particles having excellent storage stability. It is described that a uniform resin film is formed on the surface of the conductive particles to suppress the activity of the conductive layer. Further, Patent Document 2 describes that a coated conductive particle having excellent storage stability and the like is provided by a conductive particle provided with an organometallic complex that covers at least a part of the surface of the conductive particle.

Further, in order to obtain conductive particles having excellent storage stability, it is also necessary for the conductive layer to have high corrosion resistance. As such a technique, for example, Patent Document 3 describes conductive particles in which a phosphorus-containing hydrophobic group is introduced on the surface of a conductive layer. It is said that this can suppress the oxidation of the conductive layer and improve the corrosion resistance. Further, Patent Document 4 describes, in a conductive layer containing nickel, phosphorus and tungsten, conductive particles containing phosphorus in a region inside the thickness of the conductive layer and tungsten in a region outside the thickness in a specific range. .. It has been reported that this makes it difficult for corrosion to proceed even when exposed to the presence of acid. In these patent documents, an attempt is made to impart corrosion resistance by modifying the conductive layer.

Japanese Patent Application Laid-Open No. 2003-77335 Japanese Unexamined Patent Publication No. 2017-134902 Japanese Unexamined Patent Publication No. 2010-278026 JP-A-2015-10834

In general, the storage stability of the conductive particles can be achieved by suppressing the deterioration of the surface of the conductive layer such as the oxidation of the metal. Although protection is performed, when an anisotropic conductive material such as an anisotropic conductive film or an anisotropic conductive paste is used, the connection resistance increases due to the protection of the surface of the conductive layer. It was a problem to get rid of it.
Therefore, an object of the present invention is to provide conductive particles having excellent storage stability, excellent corrosion resistance and low connection resistance.

The present inventors are excellent in storage stability and corrosion resistance when the specific element present on the surface layer of the conductive layer composed of the nickel plating layer is present in a constant ratio with respect to the total amount of nickel and phosphorus or boron. And completed the present invention.

That is, in the present invention, in a conductive particle in which a nickel plating layer as a conductive layer is formed on the surface of the core material particles, within 5 nm in the depth direction from the surface of the conductive layer measured by a scanning Auger electron spectroscopic analyzer. The molar ratio of carbon to the total of nickel and phosphorus (C / (Ni + P)) or the molar ratio of carbon to the total of nickel and boron (C / (Ni + B)) is 0.0002 or more and 1.65 or less, and nickel. The molar ratio of oxygen to the total of nickel and phosphorus (O / (Ni + P)) or the molar ratio of oxygen to the total of nickel and boron (O / (Ni + B)) is 0.0001 or more and 2.0 or less, and nickel. It provides conductive particles in which the molar ratio of phosphorus to nickel (P / Ni) or the molar ratio of boron to nickel (B / Ni) is 0.003 or more and 0.7 or less.

Further, according to the present invention, in a conductive particle in which a nickel-plated layer as a conductive layer is formed on the surface of the core material particle, the conductive layer is measured by a flight time type secondary ion mass spectrometer (TOF-SIMS). The count intensity of CH ₄ N ⁺ positive ions (CH ₄ N ⁺ / Ni ⁺ ^{) with respect to the count intensity of Ni +} positive ions within 1 nm in the depth direction from the surface is 0.1 or less, or Ni ⁻ negative ions. count intensity for _C 2 _H 3 _{O 2} ^- negative ion count strength _{_{_{^{(C 2 H 3 O 2 -}}}} / Ni -) or is 10.0, Ni ^- PO of relative counts the intensity of the _negative-ion ^- negative ion count strength _^(PO 2 ^- / Ni -) or is 10.0 or less, or Ni ^- negative _B against ion count strength 2 _O 4 _{H 3} of ^- and _B 3 _O 6 _{H 4} ^- negative It provides conductive particles having an ion count intensity ((B ₂ O ₄ H ₃ ⁻ + B ₃ O ₆ H ₄ ⁻ ) / Ni ⁻ ) of 10.0 or less.

The present invention also provides a method for producing conductive particles, which comprises a step of heating the conductive particles obtained by forming a conductive layer on the surface of the core material particles at a temperature of 200 to 600 ° C. under a vacuum of 1000 Pa or less. It is something to do.

According to the present invention, it is possible to provide conductive particles having excellent storage stability, excellent corrosion resistance and low connection resistance.

FIG. 1 is an SEM image of the conductive particles obtained in Example 1. FIG. 2 is an SEM image of the conductive particles obtained in Example 4.

The conductive particles of the present invention have a nickel plating layer as a conductive layer formed on the surface of the core material particles, and the molar ratio of carbon to the total of nickel and phosphorus within 5 nm from the surface of the conductive layer (C /). (Ni + P)) or the molar ratio of carbon to the total of nickel and boron (C / (Ni + B)) is 0.0002 or more and 1.65 or less, preferably 0.0005 or more and 1.55 or less, and nickel and phosphorus. The molar ratio of oxygen to the total (O / (Ni + P)) or the molar ratio of oxygen to the total of nickel and boron (O / (Ni + B)) is 0.0001 or more and 2.0 or less, preferably 0.0003 or more. 8 or less, and the molar ratio of phosphorus to nickel (P / Ni) or the molar ratio of boron to nickel (P / Ni) is 0.003 or more and 0.7 or less, preferably 0.005 or more and 0.5. Is.

In the present invention, the molar ratio of each of the above elements is carbon, oxygen, nickel and carbon, oxygen, nickel within 5 nm from the surface of the conductive layer using a scanning Auger electron spectroscopic analyzer (hereinafter, also referred to as an AES analyzer). The atomic% of phosphorus or boron was measured, and the measured values of each element of carbon and oxygen with respect to the total measured values of nickel and phosphorus or nickel and boron were calculated, and the measured values of phosphorus or boron with respect to the measured values of nickel were calculated. be. As the AES analyzer, for example, PHI-710 manufactured by ULVAC-PHI Co., Ltd. can be used.

If the molar ratio of each element of carbon and oxygen to the total of nickel and phosphorus or nickel and boron and the molar ratio of phosphorus or boron to nickel are less than the lower limit of the above range, the crystal structure portion becomes too large and corrosion occurs. Since it becomes a starting point, storage stability deteriorates, and if the upper limit of the above range is exceeded, the number of amorphous structural portions becomes too large and the connection resistance becomes high.

Further, the conductive particles of the present invention have a nickel-plated layer as a conductive layer formed on the surface of the core material particles, and are a flight time type secondary ion mass spectrometer (hereinafter, also referred to as TOF-SIMS). The count intensity of CH ₄ N ⁺ positive ions (CH ₄ N ⁺ / Ni ⁺ ^{) with respect to the count intensity of Ni +} positive ions within 1 nm from the surface of the conductive layer measured by is 0.1 or less, preferably 0. 05 or less ^{_{_{_{either, Ni - C 2 H 3 O}}}} 2 for counting the strength of the negative ion ^- negative ion count strength of _{_{_{^{(C 2 H 3 O 2 -}}}} / Ni -) 10.0 or less, preferably 9. 0 or less than, Ni ^- the PO ₂ for counting the strength of the negative ion ^- negative ion count strength _^(PO 2 - / Ni ^-) 10.0 or less, or preferably 9.0 or less, or Ni ^- the _B 2 _O 4 for the count intensity of the negative ion _{H 3} ^- and _B 3 _O 6 _{H 4} ^- negative ion count strength _{_{_{^{_{((B 2 O 4 H 3}}}}} - + B 3 O 6 H 4 -) / Ni -) Is 10.0 or less, preferably 9.0 or less. As the TOF-SIMS, for example, TOF-SIMS5 type manufactured by ION-TOF can be used.

Ni ^⁺ _CH 4 ^N ⁺ of positive ions count intensity for counting the strength of the positive ions _{^{^{(CH 4 N + / Ni +}}} ), Ni - C 2 H 3 O 2 for counting the strength of the negative ion ^- counts of negative ions Intensity (C ₂ H ₃ O ₂ ⁻ / Ni ⁻ ), _{PO 2} ⁻ negative ion count intensity relative to ^{Ni −} negative ion count intensity (PO ₂ ⁻ / Ni ⁻ ), or Ni ⁻ negative ion count intensity and _B 3 _O 6 _{H 4} ^{^- -} negative ion count strength _{_{_{^{_{((B 2 O 4 H 3}}}}} - + B 3 O 6 H 4 -) / Ni -) B 2 O 4 H 3 for the is less than the above range This is preferable because corrosion is suppressed and the connection resistance after pressure connection is low. On the contrary, if it exceeds the above range, the conductive layer is likely to be corroded, which affects the connection reliability after the pressure connection.

The _CH 4 ^{N +} is a positive ion from amine compounds, the _C ₂ _H 3 _O 2 ^- is a negative ion derived from the organic acid, the PO ₂ ^- the negative ions from phosphoric acid compound, wherein the _B 2 O ₄ H ₃ ^- and _B 3 _O 6 _{H 4} ^- is a negative ion derived from boric acid compound.
The amine compound, the organic acid, the phosphoric acid compound, and the boric acid compound are complexing agents and dispersants contained in the electroless plating solution when the method for producing conductive particles of the present invention described later is carried out. , A reducing agent, a pH buffering agent, a surfactant and the like.

The complexing agent is an effective component for preventing the precipitation of nickel compounds such as nickel hydroxide by forming a stable complex with nickel ions, and further for accelerating the precipitation reaction of nickel at an appropriate rate. Yes, various complexing agents used in known electroless nickel plating solutions can be used. Specific examples of such complexing agents include monocarboxylic acids such as acetic acid, propionic acid and butyric acid and their soluble salts, dicarboxylic acids such as oxalic acid and adipic acid and their soluble salts, and oxycarboxylic acids such as malic acid and tartrate acid. Acids and soluble salts thereof, aminocarboxylic acids such as glycine and alanine and soluble salts thereof, ethylenediamine tetraacetic acid, versenol (N-hydroxyethylethylenediamine-N, N', N'-triacetic acid), quadrol (N, N, N', N'-Tetrahydroxyethylethylenediamine) and other ethylenediamine derivatives and their soluble salts, 1-hydroxyethane-1,1-diphosphonic acid, ethylenediaminetetramethylenephosphonic acid and other phosphonic acids and their soluble salts, pyrophosphates and their salts. Soluble salts and the like can be mentioned. These complexing agents can be used alone or in admixture of two or more.

Examples of the amine compound include aliphatic amines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, triethanolamine, N, N-diisopropylethylamine, tetramethylethylenediamine and hexamethylenediamine, and phenylamine. , Aromatic amines such as benzylamine, N-phenylhydroxylamine, hydroxylamines such as O-methylhydroxylamine, O-carboxyhydroxylamine, and pyrrole, pyrazole, imidazole, pyridine, oxazole, thiazole, benzothiazole. , Triazole, benzotriazole and other heterocyclic amines and their alkali metal salts, alanine, arginine, glutamine, glutamic acid, glycine, leucine, phenylalanine, cystine, histidine, glutathione, methionine, asparagine, aspartic acid, etc. Will be.

Examples of the organic acid include saturated fatty carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, lauric acid, tridecyl acid, partiminic acid and stearic acid, and alkali metal salts thereof, acrylic acid, methacrylic acid and oleic acid. , Linol acid, α-linolenic acid, and other unsaturated fatty carboxylic acids and alkali metal salts thereof, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and other saturated dicarboxylic acids and alkali metal salts thereof, maleic acid. , Fumaric acid, unsaturated dicarboxylic acids and alkali metal salts thereof, aconitic acid and alkali metal salts thereof, aromatic carboxylic acids such as benzoic acid, salicylic acid, phthalic acid, and alkali metal salts thereof, lactic acid, glyceric acid, apples. Hydroxycarboxylic acids such as acid, tartaric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, citric acid, leucic acid, pantoic acid, pantothenic acid, celebronic acid and their alkali metal salts, ethylenediamine tetraacetic acid, ethylenediamine tetra Examples include disodium acetate.

Examples of the phosphoric acid compound include oxyphosphoric acid such as phosphoric acid, hypophosphoric acid, and phosphoric acid and its soluble salt, pyrophosphoric acid and its soluble salt, and phosphoric acid ester such as phosphoric acid monododecyl ester and its soluble salt. Examples include phosphoric acid esters and soluble salts thereof, phosphonic acid and derivatives thereof. This phosphoric acid compound is derived from a phosphorus-based compound such as sodium hypophosphite and potassium hypophosphite, which are reducing agents contained in the electroless plating solution.

Examples of the boric acid compound include boric acid anhydride, pyroboric acid, orthoboric acid and derivatives thereof. This borate compound contains the reducing agents methylhexaborane, dimethylamineborane, diethylamineborane, morpholinborane, pyridineamineborane, piperidineborane, ethylenediamineborane, ethylenediaminebisborane, t-butylamineborane, which are contained in the electroless plating solution. It is derived from boron-based compounds such as imidazole borane, methoxyethylamine borane, sodium boron hydride, and potassium boron hydride.

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, and can be used without particular limitation. Examples of the inorganic core particles include metal particles such as gold, silver, copper, nickel, palladium, and solder, alloys, glass, ceramics, silica, metal or non-metal oxides (including hydrous), 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. On the other hand, 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. Examples thereof include thermosetting resins such as resins, alkyd resins, phenol resins, urea resins, benzoguanamine resins, melamine resins, xylene resins, silicone resins, epoxy resins and diallyl phthalate resins. These may be used alone or in combination of two or more.

The core material particles may be composed of a material composed of both an inorganic substance and an organic substance, instead of the material composed of either the above-mentioned inorganic substance or the organic substance. When the core material particles are made of a material composed of both an inorganic substance and an organic substance, the existence mode of the inorganic substance and the organic substance in the core material particles is, for example, a core made of the inorganic substance and an inorganic substance covering the surface of the core. Examples thereof include a core-shell type configuration including a mode including a shell, or a mode including a core made of an organic substance and a shell made of an inorganic substance covering the surface of the core. In addition to these, 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 are preferably made of an organic substance or a material made of both an inorganic substance and an organic substance, and more preferably made of a material made of both an inorganic substance and an organic substance. The inorganic substances include glass, ceramics, silica, metal or non-metal oxides (including hydrous), metal silicates including aluminosilicates, metal carbides, metal nitrides, metal carbonates, metal sulfates, and metal phosphorus. Preferably acid salts, metal sulfides, metal acid salts, metal halides and carbons. Further, the organic substance is preferably a thermoplastic resin such as natural fiber, natural resin, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylic acid ester, polyacrylic nitrile, polyacetal, ionomer, polyester and the like. By using 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. ..

When an organic substance is used as the core material particles, the fact that the core material particles do not have a glass transition temperature or the glass transition temperature exceeds 100 ° C. makes it easy to maintain the shape of the core material particles and the core in the process of forming a metal film. It is preferable because it is easy to maintain the shape of the material particles. The glass transition temperature can be determined, for example, as the intersection of the tangents of the original baseline and the inflection in the baseline shift portion of the DSC curve obtained by differential scanning calorimetry (DSC).

When an organic substance is used as the core material particles and the organic substance is a highly crosslinked resin, almost no baseline shift is observed even if the glass transition temperature is measured up to 200 ° C. by the above method. In the present specification, such particles are also referred to as particles having no glass transition temperature, and in the present invention, such core material particles may be used. As a specific example of the core material having no glass transition temperature, it can be obtained by copolymerizing the monomer constituting the organic substance exemplified above in combination with the crosslinkable monomer. Examples of the crosslinkable monomer 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. (Meta) acrylate, 1,6-hexanedi (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,9-nonandiol di (meth) acrylate, trimeterol propanthry (meth) acrylate, tetramethylol methandi (meth) Meta) acrylate, tetramethylol methanetri (meth) acrylate, tetramethylol methanetetra (meth) acrylate, tetramethylol propanetetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, glycerol di (meth) acrylate, glycerol tridi (meth) acrylate Polyfunctional (meth) acrylates such as meth) acrylates, polyfunctional vinyl monomers such as divinylbenzene and divinyltoluene, vinyltrimethoxysilane, trimethoxysilylstyrene, γ- (meth) acryloxypropyltrimethoxysilane, etc. Examples thereof include silane-containing monomers, triallyl isocyanurates, diallyl phthalates, diallyl acrylamides, diallyl ethers and the like. In particular, in the field of COG (Chip on Glass), core material particles made of such a hard organic material are often used.

There are no particular restrictions on the shape of the core material particles. Generally, the core material particles are spherical. However, 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 amorphous shape. In the present invention, spherical core material particles are preferable in terms of excellent filling property and easy coating with metal.

The conductive layer formed on the surface of the core material particles is made of a conductive metal. Examples of the metal constituting the conductive layer include gold, platinum, silver, copper, iron, zinc, nickel, tin, lead, antimony, bismuth, cobalt, indium, titanium, germanium, aluminum, chromium, palladium, tungsten, molybdenum, and the like. Metals such as calcium, magnesium, rhodium, sodium, iridium, beryllium, ruthenium, potassium, cadmium, osmium, lithium, rubidium, gallium, tarium, tantalum, cesium, thorium, strontium, poronium, zirconium, barium, manganese or alloys thereof. In addition, metal compounds such as ITO and solder can be mentioned. Of these, gold, silver, copper, nickel, palladium, rhodium or solder is preferable because of its low electrical resistance, and nickel, gold, nickel alloy or gold alloy is particularly 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. In the case of a laminated structure consisting of a plurality of layers, the outermost layer may be at least one selected from nickel, gold, silver, copper, palladium, nickel alloy, gold alloy, silver alloy, copper alloy and palladium alloy. preferable.
In the conductive particles of the present invention, the outermost surface layer of the conductive layer is a nickel-phosphorus plating layer or a nickel-boron plating layer.

Further, 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 covered, the coated portions may be continuous, for example, may be discontinuously covered in an island shape.

The thickness of the conductive layer is preferably 5 nm or more and 2,000 nm or less, and more preferably 10 nm or more and 1,500 nm or less. When the thickness of the conductive layer is within the above range, the electrical characteristics are excellent and the storage stability is also excellent. When the conductive particles have protrusions described later, the height of the protrusions is not included in the thickness of the conductive layer referred to here. In the present invention, the thickness of the conductive layer can be measured by cutting the particles to be measured into two pieces and observing the cross section of the cut end with a scanning electron microscope (SEM).

The average particle size of the conductive particles is preferably 0.1 μm or more and 50 μm or less, and more preferably 1 μm or more and 30 μm or less. When the average particle size of the conductive particles is within the above range, it is easy to secure conduction between the counter electrodes without causing a short circuit in a direction different from that between the counter electrodes. In the present invention, the average particle size of the conductive particles is a value measured by SEM observation. 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.

When the conductive particles have protrusions on their surface, that is, when the outer surface of the conductive layer has a protrusion, the height of the protrusions is preferably 20 nm or more and 1,000 nm or less, more preferably 50 nm and 800 nm or less. .. The number of protrusions depends on the particle size of the conductive particles, but is preferably 1 or more and 20,000 or less, and more preferably 5 or more and 5,000 or less per conductive particle. It is advantageous in that the conductivity of the conductive particles is further improved. The length of the base of the protrusion is preferably 5 nm or more and 1,000 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 the cross section of the particle is observed by SEM, and the height of the protrusion is from the base of the protrusion to the protrusion apex. The shortest distance to. When one protrusion has a plurality of vertices, the highest vertex is the height of the protrusion. The length of the base of the protrusion and the height of the protrusion shall be the arithmetic mean of the 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. For example, 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. In the present invention, it is preferable that the shape is spherical or has a large number of protrusions on the outer surface in terms of excellent filling property and connectivity.

As a method for forming a conductive layer on the surface of the core material particles, 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. Can be mentioned. Further, a conductive layer may be formed on the surface of the core material particles by combining these methods.

In the present invention, by forming a nickel-phosphorus plating layer or a nickel-boron plating layer as a conductive layer on the surface of core material particles by an electroless plating method, conductive particles having desired particle characteristics can be obtained. Is preferable because it is easy to use.

Hereinafter, a method of forming a nickel plating layer as a conductive layer will be described.
When the conductive layer is formed on the surface of the core material particles by the electroless plating method, 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. Is preferable. 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. For example, when an amino group, an imino group, an amide group, an imide group, a cyano group, a hydroxyl group, a nitrile group, a carboxyl group, etc. are present on the surface of the core material particles, the surface of the core material particles has an ability to capture noble metal ions. Have. When 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 precious metal on the surface thereof. Specifically, 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 captured 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. As a result, the precious metal is carried on the surface of the core material particles. As 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 from these based on the constituent material of the target conductive layer. It is preferable to be done.

Before capturing the noble metal ions on the surface of the core material particles, a sensitization treatment for adsorbing tin ions on the surface of the particles may be performed. In order to adsorb tin ions on the surface of the particles, for example, 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. There are two types of treatments for forming the conductive layer: a treatment for forming a conductive layer having protrusions and a treatment for forming a conductive layer having a smooth surface. First, a treatment for forming a conductive layer having protrusions will be described.

In the process of forming the conductive layer having protrusions, the following first step and second step are performed.
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. In the first step, self-decomposition 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. Will be done. The protrusion grows from the nucleus of the generated microprotrusion as a base point.

In the first step, 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. Next, 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. As the nonionic surfactant, a polyoxyalkylene ether-based surfactant such as polyethylene glycol, polyoxyethylene alkyl ether, or polyoxyethylene alkyl phenyl ether can be used. As the amphoteric ion surfactant, a betaine-based surfactant such as alkyldimethylacetate betaine, alkyldimethylcarboxymethyl acetate betaine, and alkyldimethylaminoacetate betaine can be used. As 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.

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 0.1 to 50 g / L. As 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. When a phosphorus compound such as sodium hypophosphite is used as the reducing agent, the concentration thereof is preferably in the range of 0.1 to 50 g / L. When a boron compound, for example, dimethylamine borane is used as the reducing agent, the concentration thereof is preferably in the range of 0.01 to 100 g / L.

Examples of the complexing agent include citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid or carboxylic acids (salts) such as alkali metal salts and ammonium salts thereof, amino acids such as glycine, and amines such as ethylenediamine and alkylamine. Acids and other compounds that have a complexing effect on nickel ions, such as 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. The pH of the preferred electroless nickel plating bath at this stage is in the range of 3-14. The electroless nickel plating reaction starts promptly when an aqueous slurry of core particles is added, and is accompanied by the generation of hydrogen gas. The first step is terminated when the generation of hydrogen gas is completely no longer recognized.

Next, in the second step, following the first step, (i) 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. Either used, or (ii) a first aqueous solution containing 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, respectively. Electroless nickel plating is performed by adding to the liquid of 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, after the generation of hydrogen gas is completely no longer observed, stirring is continued while maintaining the liquid temperature for a while to complete the reaction.

In the case of (i) above, 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. In this case, the first aqueous solution does not contain the reducing agent and the alkali, and the second aqueous solution does not contain the nickel salt. As the nickel salt and the reducing agent, those described above can be used. As the 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.

In 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 components.

In any of the cases (i) and (ii), the concentration of the nickel salt in the aqueous solution is preferably 10 to 1,000 g / L, particularly preferably 50 to 500 g / L. When a phosphorus compound is used as the reducing agent, the concentration of the reducing agent is preferably 100 to 1,000 g / L, particularly preferably 100 to 800 g / L. When a boron compound is used as the reducing agent, it is preferably 5 to 200 g / L, particularly preferably 10 to 100 g / L. When 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. In this case, after the completion of the first step, 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. Is preferably added in a concentration range of 1 to 100 g / L, more preferably 5 to 50 g / L, and the dispersant is preferably 0.5 to 30 g / L, more preferably 1 to 10 g / L. It is also possible to carry out the second step of dissolving in a range to prepare an aqueous slurry and adding each of the above aqueous solutions to the aqueous slurry. In this way, the conductive layer having protrusions can be formed.

Subsequently, the process of forming a conductive layer having a smooth surface will be described below.
The formation of the conductive layer having a smooth surface can be performed by reducing the concentration of the nickel salt in the electroless nickel plating bath in the first step of the treatment for 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.

The conductive particles of the present invention are obtained by using the conductive particles obtained by the above method at 200 to 600 ° C. under a vacuum of 1,000 Pa or less, preferably 0.01 to 900 Pa, particularly preferably 0.01 to 500 Pa. It is preferably obtained by heat treatment at a temperature of 250 to 500 ° C, particularly preferably 300 to 450 ° C. By heating the conductive particles while maintaining such a vacuum state, the ratio of carbon and oxygen present on the surface of the conductive layer can be reduced, and the molar ratio of phosphorus to carbon, oxygen and nickel is appropriate. It becomes. The degree of vacuum in the present invention is an absolute pressure, that is, a value when the absolute vacuum is 0.

The heat treatment time is preferably 0.1 to 10 hours, more preferably 0.5 to 5 hours. By adopting this processing time, it is possible to suppress an increase in manufacturing cost, and it is possible to suppress denaturation of core material particles and conductive layer due to thermal history, and to reduce the influence on quality. This heat treatment time is the time from reaching the target treatment temperature to the end of the heat treatment.

The heat treatment may be performed in a state where the conductive particles are allowed to stand still, or may be performed while stirring. When the heat treatment is performed in a state where the conductive particles are allowed to stand still, it is preferable to allow the conductive particles to stand still to a thickness of 0.1 mm to 100 mm. By allowing the conductive layer to stand still at this thickness, the conductive layer can be successfully heat-treated and the manufacturing cost can be suppressed.

The heat treatment is performed by vacuuming the container containing the conductive particles and then allowing the container to stand still or stirring. At this time, the gas phase portion of the container containing the conductive particles may be replaced with an inert gas such as nitrogen and then evacuated, or may be evacuated as it is. Further, the heat treatment may be performed a plurality of times if necessary.
In this way, the conductive particles of the present invention can be obtained.

When the conductive particles of the present invention are used as a conductive filler of a conductive adhesive as described later, the surface thereof can be further coated with an insulating resin in order to prevent the occurrence of 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. , 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 μm. The insulating resin may cover the entire surface of the conductive particles, or may cover only a part of the surface of the conductive particles.

As the insulating resin, those known in the technical field can be widely used. To give an example, phenol resin, urea resin, melamine resin, allyl resin, furan resin, polyester resin, epoxy resin, silicone resin, polyamide-imide resin, polyimide resin, polyurethane resin, fluororesin, polyolefin resin (eg polyethylene). , Polypropylene, Polybutylene), Polyalkyl (meth) acrylate resin, Poly (meth) acrylic acid resin, Polystyrene resin, Acrylonitrile-styrene-butadiene resin, Vinyl resin, Polyamide resin, Polycarbonate resin, Polyacetal resin, Ionomer resin, Polyether sulfone Examples thereof include resins made of organic polymers such as resins, polyphenyl oxide resins, polysulfone resins, polyvinylidene fluoride resins, ethyl cellulose resins and cellulose acetate resins.

As a method for forming an insulating coating layer on the surface of conductive particles, a chemical method such as a core selvation method, an interfacial polymerization method, an insitu polymerization method and a liquid curing coating method, a spray drying method, and an aerial suspension coating method are used. Examples thereof include a physico-mechanical method such as a vacuum vapor deposition coating method, a dry blend method, a hybridization method, an electrostatic coalescence method, a melting dispersion cooling method and an inorganic encapsulation method, and a physicochemical method such as an interfacial precipitation method.

The organic polymer constituting the insulating resin may contain a compound containing an ionic group as a monomer component in the structure of the polymer, provided that it is non-conductive. The compound containing an ionic group may be a crosslinkable monomer or a non-crosslinkable monomer. That is, it is preferable that the organic polymer is formed by using a compound in which at least one of the crosslinkable monomer and the non-crosslinkable monomer has an ionic group. The "monomer component" refers to a structure derived from a monomer in an organic polymer, and is a component derived from the monomer. By subjecting the monomer to polymerization, an organic polymer containing the monomer component as a constituent unit is formed.

The ionic group is preferably present at the interface of the organic polymer constituting the insulating resin. Further, it is preferable that the ionic group is chemically bonded to the monomer component constituting the organic polymer. Whether or not the ionic group is present at the interface of the organic polymer is determined by the scanning electron microscope observation when the insulating resin containing the organic polymer having the ionic group is formed on the surface of the conductive particles. It can be determined by whether or not it adheres to the surface of the particles.

Examples of the ionic group include onium-based functional groups such as a phosphonium group, an ammonium group and a sulfonium group. Of these, ammonium groups or phosphonium groups are preferable from the viewpoint of enhancing the adhesiveness of the conductive particles and the insulating resin to form conductive particles having both insulating properties and conduction reliability at a high level. It is more preferably a phosphonium group.

As the onium-based functional group, those represented by the following general formula (1) are preferably mentioned.

(In the formula, X is a phosphorus atom, a nitrogen atom, or a sulfur atom, and R may be the same or different, and is a hydrogen atom, a linear, branched or cyclic alkyl group, or an aryl group. N is 1 when X is a nitrogen atom and a phosphorus atom, and 0 when X is a sulfur atom. * Is a bond.)

Examples of the counterion for the ionic group include halide ions. Examples of halide ions include Cl ⁻ , F ⁻ , Br ⁻ , and I ⁻ .

In the formula (1), examples of the linear alkyl group represented by R include a linear alkyl group having 1 or more and 20 or less carbon atoms, and specifically, a methyl group, an ethyl group, or n−. Propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n- Examples thereof include a tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group and an n-icosyl group.

In the formula (1), examples of the branched alkyl group represented by R include a branched alkyl group having 3 or more carbon atoms and 8 or less carbon atoms, and specifically, an isopropyl group, an isobutyl group, or s-. Examples thereof include a butyl group, a t-butyl group, an isopentyl group, an s-pentyl group, a t-pentyl group, an isohexyl group, an s-hexyl group, a t-hexyl group and an ethylhexyl group.

In the formula (1), examples of the cyclic alkyl group represented by R include cycloalkyl groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group and cyclooctadecyl group. ..

In the formula (1), examples of the aryl group represented by R include a phenyl group, a benzyl group, a tolyl group, an o-kisilyl group and the like.

In the general formula (1), R is preferably an alkyl group having 1 or more and 12 or less carbon atoms, more preferably an alkyl group having 1 or more and 10 or less carbon atoms, and an alkyl group having 1 or more and 8 or less carbon atoms. Is more preferable. Further, in the general formula (1), it is further preferable that R is a linear alkyl group. By having such a structure of the onium-based functional group, it is possible to enhance the adhesion between the insulating resin and the conductive particles to secure the insulating property, and to further enhance the conduction reliability at the time of thermocompression bonding.

From the viewpoint of facilitating the acquisition of the monomer and the synthesis of the polymer and increasing the production efficiency of the insulating resin, the organic polymer having an ionic group constituting the insulating resin is represented by the following general formula (2) or general formula (3). It is preferable to have a structural unit represented.

(In the formula, X, R and n are synonymous with the general formula (1). M is an integer of 0 or more and 5 or less ^{. An −} indicates a monovalent anion.)

(In the formula, X, R and n are synonymous with the general formula (1). An ⁻ represents a monovalent anion. M ¹ is an integer of 1 or more and 5 or less. R ₅ is a hydrogen atom or It is a methyl group.)

As an example of R in the formula (2) and the formula (3), the description of the functional group of R in the general formula (1) described above is appropriately applied. The ionic group may be bonded to any of the para-position, the ortho-position, and the meta-position with respect to the CH group of the benzene ring of the formula (2), and is preferably bonded to the para-position. In the formula (2) and the formula (3), a halide ion is preferably mentioned as ^{the monovalent An −.} Examples of halide ions include Cl ⁻ , F ⁻ , Br ⁻ , and I ⁻ .

Further, in the general formula (2), m is preferably an integer of 0 or more and 2 or less, more preferably 0 or 1, and particularly preferably 1. In the general formula (3), m ¹ is preferably 1 or more and 3 or less, more preferably 1 or 2, and most preferably 2.

The organic polymer having an ionic group is preferably composed, for example, containing a monomer component having an onium-based functional group and an ethylenically unsaturated bond. From the viewpoint of facilitating the acquisition of the monomer and the synthesis of the polymer and increasing the production efficiency of the insulating resin, the organic polymer having an ionic group preferably contains a non-crosslinkable monomer component.

Examples of the non-crosslinkable monomer having an onium-based functional group and an ethylenically unsaturated bond include N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropylacrylamide, N, N, N-trimethyl. -N-2-Armium group-containing monomer such as methacryloyloxyethylammonium chloride; Monomer having a sulfonium group such as phenyldimethylsulfonate sulfonatemethylsulfate; 4- (vinylbenzyl) triethylphosphonium chloride, 4- (vinylbenzyl) trimethyl Phosphonium chloride, 4- (vinylbenzyl) tributylphosphonium chloride, 4- (vinylbenzyl) trioctylphosphonium chloride, 4- (vinylbenzyl) triphenylphosphonium chloride, 2- (methacloyloxyethyl) trimethylphosphonium chloride, 2-( Phosphonium groups such as metachlorooxyethyl) triethylphosphonium chloride, 2- (methacloyloxyethyl) tributylphosphonium chloride, 2- (methacloyloxyethyl) trioctylphosphonium chloride, 2- (methacloyloxyethyl) triphenylphosphonium chloride. Examples thereof include monomers having the above. The organic polymer having an ionic group may contain two or more kinds of non-crosslinkable monomer components.

In the organic polymer constituting the insulating resin, an ionic group may be bonded to all of the monomer components, or an ionic group may be bonded to a part of all the constituent units of the organic polymer. good. When an ionic group is bonded to a part of all the constituent units of the organic polymer, the ratio of the monomer component to which the ionic group is bonded is preferably 0.01 mol% or more and 99 mol% or less, and is 0. More preferably, it is 0.02 mol% or more and 95 mol% or less. Here, the number of monomer components in the organic polymer counts the structure derived from one ethylenically unsaturated bond as a constituent unit of one monomer. When the ionic group is contained in both the crosslinkable monomer and the non-crosslinkable monomer, the ratio of the monomer components is the total amount.

Examples of the form of coating with the insulating resin include a form in which a plurality of insulating fine particles are arranged in a layer, or an insulating continuous film.

When the insulating resin is made of insulating fine particles, the insulating fine particles are melted, deformed, peeled off, or moved on the surface of the conductive particles by heat-bonding the conductive particles coated with the insulating fine particles between the electrodes to generate heat. The metal surface of the conductive particles in the crimped portion is exposed, which enables conduction between the electrodes and provides connectivity. On the other hand, since the surface portion of the conductive particles facing a direction other than the thermocompression bonding direction is generally maintained in a state of being covered with the insulating fine particles on the surface of the conductive particles, conduction in a direction other than the thermocompression bonding direction is prevented. ..

By including the ionic group on the surface of the insulating fine particles, the insulating fine particles can easily adhere to the conductive particles, whereby the ratio of the insulating fine particles covered with the insulating fine particles on the surface of the conductive particles can be made sufficient, and the insulating fine particles are conductive. The peeling of insulating fine particles from the particles is effectively prevented. Therefore, the effect of preventing a short circuit in a direction different from that between the counter electrodes by the insulating fine particles is likely to be exhibited, and improvement in the insulating property in that direction can be expected.

The shape of the insulating fine particles is not particularly limited and may be spherical or may be a shape other than spherical. Examples of the shape other than the spherical shape include a fibrous shape, a hollow shape, a plate shape, and a needle shape. Further, the insulating fine particles may have a large number of protrusions on the surface thereof or may have an amorphous shape. Spherical insulating fine particles are preferable in terms of adhesion to conductive particles and ease of synthesis.

The average particle size (D) of the insulating fine particles is preferably 10 nm or more and 3,000 nm or less, and more preferably 15 nm or more and 2,000 nm or less. When the average particle size of the insulating fine particles is within the above range, it is easy to secure conduction between the counter electrodes without causing a short circuit in the obtained coated particles in a direction different from that between the counter electrodes. In the present invention, the average particle size of the insulating fine particles is a value measured by observation using a scanning electron microscope, and specifically, it is measured by the method described in Examples described later.

The particle size distribution of the insulating fine particles measured by the above method varies. Generally, the width of the particle size distribution of the powder is represented by the coefficient of variation (hereinafter also referred to as “CV”) represented by the following formula (1).
C. V. (%) = (Standard deviation / average particle size) x 100 ... (1)
This C.I. V. Larger indicates that the particle size distribution is wider, while C.I. V. A small value indicates that the particle size distribution is sharp. The coated particles of this embodiment are C.I. V. It is preferable to use insulating fine particles of 0.1% or more and 20% or less, more preferably 0.5% or more and 15% or less, and most preferably 1% or more and 10% or less. C. V. However, there is an advantage that the thickness of the coating layer made of the insulating fine particles can be made uniform.

Further, the insulating resin may be a continuous film made of a polymer and having an ionic group instead of the above-mentioned insulating fine particles. When the insulating resin is a continuous film having an ionic group, the conductive particles are thermally pressure-bonded between the electrodes to melt, deform or peel off the continuous film, and the metal surface of the conductive particles is exposed. This enables continuity between the electrodes and provides connectivity. In particular, the metal surface is often exposed by tearing the continuous film by thermocompression bonding the conductive particles between the electrodes. On the other hand, in the surface portion of the conductive particles facing a direction different from the thermocompression bonding direction, the coating state of the conductive particles by the continuous film is generally maintained, so that conduction in a direction other than the thermocompression bonding direction is prevented. It is preferable that the continuous film also has an ionic group on the surface.

The thickness of the continuous film is preferably 10 nm or more from the viewpoint of improving the insulating property in a direction different from that between the counter electrodes, and 3,000 nm or less is preferable from the viewpoint of ease of conduction between the counter electrodes. Is preferable. From this point of view, the thickness of the continuous film is preferably 10 nm or more and 3,000 nm or less, and more preferably 15 nm or more and 2,000 nm or less.

Similar to the insulating fine particles, in the continuous film, the ionic group preferably forms a part of the chemical structure of the substance as a part of the substance constituting the continuous film. In the continuous film, the ionic group is preferably contained in at least one structure of the constituent unit of the polymer constituting the continuous film. The ionic group is preferably chemically bonded to the polymer constituting the continuous film, and more preferably bonded to the side chain of the polymer.

When the insulating resin is a continuous film, it is preferable that the insulating particles are a continuous film obtained by coating the conductive particles with insulating fine particles having an ionic group on the surface and then heating the insulating fine particles. Alternatively, it is preferably a continuous film obtained by dissolving the insulating fine particles with an organic solvent. As described above, the insulating fine particles having an ionic group easily adhere to the conductive particles, whereby the ratio of being covered with the insulating fine particles on the surface of the conductive particles becomes sufficient, and the conductive particles are covered with the insulating fine particles. It becomes easy to prevent the peeling of the insulating fine particles from. Therefore, the continuous film obtained by heating or dissolving the insulating fine particles that coat the conductive particles can have a uniform thickness and a high coating ratio on the surface of the conductive particles.

Further, the conductive particles according to the production method of the present invention may be treated with a surface treatment agent for the purpose of increasing the affinity with the insulating resin and improving the adhesion.
Examples of the surface treatment agent include benzotriazole-based compounds, titanium-based compounds, higher fatty acids or derivatives thereof, phosphoric acid esters, phosphite esters and the like. These may be used alone or in combination of two or more as needed.

The surface treatment agent may or may not be chemically bonded to the metal on the surface of the conductive particles. The surface treatment agent may be present on the surface of the conductive particles, and in that case, it may be present on the entire surface of the conductive particles, or may be present only on a part of the surface.

Examples of the triazole-based compound include compounds having a nitrogen-containing heterocyclic structure having three nitrogen atoms in a 5-membered ring.

Examples of the triazole-based compound include a compound having a triazole monocyclic structure that is not condensed with another ring, and a compound having a ring structure in which a triazole ring and another ring are condensed. Examples of other rings include a benzene ring and a naphthalene ring.

Among them, a compound having a ring structure in which a triazole ring and another ring are condensed is preferable because of its excellent adhesion to an insulating resin, and a benzotriazole compound which is a compound having a structure in which a triazole ring and a benzene ring are condensed is particularly preferable. Is preferable.
Examples of the benzotriazole-based compound include those represented by the following general formula (I).

(In the formula, R ¹¹ is a negative charge, a hydrogen atom, an alkali metal, an optionally substituted alkyl group, an amino group, a formyl group, a hydroxyl group, an alkoxy group, a sulfonic acid group or a silyl group, and R ¹² ,. R ¹³ , R ¹⁴ and R ¹⁵ are independently hydrogen atoms, halogen atoms, optionally substituted alkyl groups, carboxyl groups, hydroxyl groups or nitro groups.)

^{Examples of the alkali metal represented by R 11} in the formula (I) include lithium, sodium, potassium and the like. The ^{alkali metal represented by R 11} is an alkali metal cation, and when R ¹¹ in the formula (I) is an alkali metal, ^{the bond between R 11} and the nitrogen atom may be an ionic bond.
^{Examples of the alkyl group represented by R 11} , R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ in the formula (I) include those having 1 to 20 carbon atoms, and 1 to 12 carbon atoms are particularly preferable. The alkyl group may be substituted, and the substituents include an amino group, an alkoxy group, a carboxyl group, a hydroxyl group, an aldehyde group, a nitro group, a sulfonic acid group, a quaternary ammonium group, a sulfonium group and a sulfonyl group. Examples include a phosphonium group, a cyano group, a fluoroalkyl group, a mercapto group, and a halogen atom.
As the ^{alkoxy group represented by R 11} , those having 1 to 12 carbon atoms are preferably mentioned.
Further, the number of carbon atoms of the alkoxy group as a substituent of the alkyl group represented by ^{R 12} , R ¹³ , R ¹⁴ and R ^{15 is preferably 1 to 12.} ^{Examples of the halogen atom represented by R 12} , R ¹³ , R ¹⁴ and R ¹⁵ in the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like.

Specific triazole-based compounds include 1,2,3-triazole, 1,2,4-triazole, 3-amino-1H-1,2,4-triazole, and 5 as compounds having a triazole monocyclic structure. -Mercapto-1H-1,2,3-triazole sodium, 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, 3-amino-5-mercapto-1,2,4-triazole, In addition, benzotriazole having a ring structure in which a triazole ring and another ring are condensed, 1-methyl-1H-benzotriazole, 4-methyl-1H-benzotriazole, 5-methyl-1H-benzotriazole, 4 -Carboxy-1H-benzotriazole, 5-carboxy-1H-benzotriazole, 5-ethyl-1H-benzotriazole, 5-propyl-1H-benzotriazole, 5,6-dimethyl-1H-benzotriazole, 1-aminobenzo Triazole, 5-nitrobenzotriazole, 5-chlorobenzotriazole, 4,5,6,7-tetrabromobenzotriazole, 1-hydroxybenzotriazole, 1- (methoxymethyl) -1H-benzotriazole, 1H-benzotriazole- 1-Methanol, 1H-benzotriazole-1-carboxyaldehyde, 1- (chloromethyl) -1H-benzotriazole, 1-hydroxy-6- (trifluoromethyl) benzotriazole, benzotriazole butyl ester, 4-carboxy-1H -Benzotriazole butyl ester, 4-carboxy-1H-benzotriazole octyl ester, 1- [N, N-bis (2-ethylhexyl) aminomethyl] methylbenzotriazole, 2,2'-[[(methyl-1H-benzo) Triazole-1-yl) methyl] imino] bisethanol, tetrabutylphosphonium benzotriazolate, 1H-benzotriazole-1-yloxytris (dimethylamino) phosphonium hexafluorophosphart, 1H-benzotriazole-1-yloxy Tripyrolidinophosphonium hexafluorophosphate, 1- (formamide methyl) -1H-benzotriazole, 1- [bis (dimethylamino) methylene] -1H-benzotriazolium 3-oxide hexafluorophosphate, 1- [bis (Dimethylamino) Methylene] -1H-benzotriazolium 3-oxidetet Lafluoroborate, (6-chloro-1H-benzotriazole-1-yloxy) tripyrolidinophosphonium hexafluorophosphate, O- (benzotriazole-1-yl) -N, N, N', N'-bis (Tetramethylene) Uronium hexafluorophosphate, O- (6-chlorobenzotriazole-1-yl) -N, N, N', N'-tetramethyluronium tetrafluoroborate, O- (6-chloro Benzotriazole-1-yl) -N, N, N', N'-tetramethyluronium hexafluorophosphate, O- (benzotriazole-1-yl) -N, N, N', N'-bis ( Pentamethylene) uronium hexafluorophosphate, 1- (trimethylsilyl) -1H-benzotriazole, 1- [2- (trimethylsilyl) ethoxycarbonyloxy] benzotriazole, 1- (trifluoromethanesulfonyl) -1H-benzotriazole, ( Trifluoroacetyl) Benzotriazole, Tris (1H-benzotriazole-1-yl) methane, 9- (1H-benzotriazole-1-ylmethyl) -9H-carbazole, [(1H-benzotriazole-1-yl) methyl] Triphenylphosphonium chloride, 1- (isocyanomethyl) -1H-benzotriazole, 1-[(9H-fluoren-9-ylmethoxy) carbonyloxy] benzotriazole, 1,2,3-benzotriazole sodium salt, naphthotriazole, etc. Can be mentioned.

As the titanium-based compound, for example, when a compound having a structure represented by the general formula (II) is present on the surface of conductive particles, an affinity between the insulating resin and the conductive particles can be easily obtained and a solvent. It is particularly preferable because it is easy to disperse in the particle and the surface of the conductive particles can be uniformly treated.

(R ²¹ is a divalent or trivalent group, R ²² is an aliphatic hydrocarbon group having 2 or more and 30 or less carbon atoms, an aryl group having 6 or more and 22 or less carbon atoms, or 7 or more and 23 or less carbon atoms. If it is an arylalkyl group, p and r are integers of 1 or more and 3 or less, satisfy p + r = 4, q is an integer of 1 or 2, and R ²¹ is a divalent group, q is. When it is 1 and R ²¹ is a trivalent group, q is 2. When q is 2, a plurality of R ^22s may be the same or different. * Represents a bond. )

Examples of the aliphatic hydrocarbon group having 4 or more and 28 or less carbon atoms represented by R ²² include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group and a nonyl group. , Decyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, henicosyl group, docosyl group and the like. Examples of unsaturated aliphatic hydrocarbon groups include dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, nonadesenyl group, icosenyl group, eicosenyl group, henicosenyl group and docosenyl group as alkenyl groups. Be done. Examples of the aryl group having 6 or more and 22 or less carbon atoms include a phenyl group, a tolyl group, a naphthyl group, an anthryl group and the like.
Examples of the arylalkyl group having 7 or more and 23 or less carbon atoms include a benzyl group, a phenethyl group, a naphthylmethyl group and the like.
As the hydrophobic group, a linear or branched aliphatic hydrocarbon group is particularly preferable, and a linear aliphatic hydrocarbon group is particularly preferable.
As the aliphatic hydrocarbon group as the hydrophobic group, those having 4 or more and 28 or less carbon atoms are more preferable, and those having 6 or more and 24 or less are the most preferable, from the viewpoint of enhancing the affinity between the insulating resin and the conductive particles. preferable.

Examples of the divalent group represented by R ²¹ include -O-, -COO-, -OCO-, -OSO _2- and the like. Examples of the trivalent group represented by R ²¹ include -P (OH) (O-) ₂ , -OPO (OH) -OPO (O-) _{2, and the} like.

In the general formula (II), * is a bond, and the bond may be bonded to the metal film of the conductive particles, or may be bonded to another group or the like. Examples of other groups in that case include hydrocarbon groups, and specific examples thereof include alkyl groups having 1 or more and 12 or less carbon atoms.

As the titanium-based compound having the structure represented by the general formula (II), the compound having the structure in which R ²¹ is a divalent group in the general formula (II) has the availability and the conductive property of the conductive particles. It is preferable in that it can be processed without damage. The structure in which R ²¹ is a divalent group in the general formula (II) is represented by the following general formula (III).

(R ²¹ is a group selected from -O-, -COO-, -OCO-, and -OSO _2- , and p, r and R ²² are synonymous with the general formula (II).)

In the general formulas (II) and (III), r is preferably 2 or 3, from the viewpoint of improving the adhesion between the insulating resin and the conductive layer, and r is most preferably 3.

Specific examples of the titanate-based coupling agent used in the present invention include isopropyltriisostearoyl titanate, isopropyltridodecylbenzenesulfonyl titanate, isopropyltris (dioctylpyrophosphate) titanate, tetraisopropyl (dioctylphosphite) titanate, and tetraisopropylbis. (Dioctylphosphite) titanate, tetraoctylbis (ditridecylphosphite) titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (ditridecyl) phosphite titanate, bis (dioctylpyrophosphate) oxyacetate titanate, Examples thereof include bis (dioctylpyrophosphate) ethylene titanate, and these can be used in one kind or two or more kinds.
These titanate-based coupling agents are commercially available, for example, from Ajinomoto Fine-Techno Co., Ltd.

The higher fatty acid is preferably a saturated or unsaturated linear or branched mono or polycarboxylic acid, more preferably a saturated or unsaturated linear or branched monocarboxylic acid. More preferably, it is a saturated or unsaturated linear monocarboxylic acid. The fatty acid preferably has 7 or more carbon atoms. The derivative refers to a salt or amide of the fatty acid.

The higher fatty acid or its derivative used in the present invention preferably has 7 to 23 carbon atoms, more preferably 10 to 20 carbon atoms. Examples of such higher fatty acids or derivatives thereof include saturated fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid and stearic acid, unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid and arachidonic acid, or these. Metal salts or amides of the above can be mentioned. Examples of the metal salt of the higher fatty acid include alkali metals, alkaline earth metals, transition metals such as Zr, Cr, Mn, Fe, Co, Ni, Cu and Ag, and metals other than transition metals such as Al and Zn. Examples thereof include polyvalent metal salts such as Al, Zn, W and V. The higher fatty acid metal salt may be a mono-form, a di-form, a tri-form, a tetra-form or the like, depending on the valence of the metal. The higher fatty acid metal salt may be any combination thereof.

As the phosphoric acid ester and the phosphite ester, those having an alkyl group having 6 to 22 carbon atoms are preferably used.
Examples of the phosphoric acid ester include phosphoric acid hexyl ester, phosphoric acid heptyl ester, phosphoric acid monooctyl ester, phosphoric acid monononyl ester, phosphoric acid monodecyl ester, phosphoric acid monoundecyl ester, phosphoric acid monododecyl ester, and phosphorus. Examples thereof include acid monotridecyl ester, phosphoric acid monotetradecyl ester, and phosphoric acid monopentadecyl ester.
Examples of the phosphite ester include succinic acid hexyl ester, succinic acid heptyl ester, sulphate monooctyl ester, sulphate monononyl ester, sulphate monodecyl ester, and sulphate monoundecyl ester. Examples thereof include phosphite monododecyl ester, sulphate monotridecyl ester, sulphate monotetradecyl ester, and sulphate monopentadecyl ester.

In the present invention, the surface treatment agent is preferably a triazole-based compound or a titanium-based compound, and is particularly benzotriazole or 4-carboxyl, because it has an excellent affinity with the insulating resin and has a high effect of increasing the coverage of the insulating resin. Benzotriazole, isopropyltriisostearoyl titanate, and tetraisopropyl (dioctylphosphite) titanate are particularly preferred.

The method of treating the conductive particles with a surface treatment agent is obtained by dispersing the conductive particles in a solution of the surface treatment agent and then filtering the particles. Before the treatment with the surface treatment agent, the conductive particles may be treated with another treatment agent or may not be treated.
The concentration of the surface treatment agent in the solution of the surface treatment agent for dispersing the conductive particles (solution containing the conductive particles) is 0.01% by mass or more and 10.0% by mass or less. The solvent in the solution of the surface treatment agent is water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, isopentyl alcohol, cyclohexanol, and other alcohols, acetone, and methyl. Ketones such as isobutyl ketone, methyl ethyl ketone, methyl-n-butyl ketone, esters such as methyl acetate and ethyl acetate, ethers such as diethyl ether and ethylene glycol monoethyl ether, normal hexane, cyclohexanone, toluene, 1,4 -Dioxane, N, N-dimethylformamide, tetrahydrofuran and the like can be mentioned. It is preferable that the dispersed and filtered conductive particles after the surface treatment are dispersed in the solvent again to remove the excess surface treatment agent.

The surface treatment of the conductive particles with the surface treatment agent can be performed by mixing the conductive particles, the surface treatment agent and the solvent at room temperature. Alternatively, the conductive particles and the surface treatment agent may be mixed in a solvent and then heated to accelerate the reaction. The heating temperature is, for example, 30 ° C. or higher and 50 ° C. or lower.

Since the conductive particles of the present invention have low connection resistance, they are conductive for connecting, for example, an anisotropic conductive film (ACF), a heat-sealed 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 sex material. Examples of the conductive material include the use of the conductive particles of the present invention as they are, or the use of the conductive particles of the present invention dispersed in a binder resin. Other forms of the conductive material are not particularly limited, and examples thereof include an anisotropic conductive paste, a conductive adhesive, and an anisotropic conductive ink.

Examples of the binder resin include thermoplastic resins and thermosetting resins. Examples of the thermoplastic resin include acrylic resin, styrene resin, ethylene-vinyl acetate resin, styrene-butadiene block copolymer and the like, and examples of the thermosetting resin include epoxy resin, phenol resin and urea resin. Examples thereof include polyester resin, urethane resin, and polyimide resin.

In addition to the conductive particles and the binder resin of the present invention, the conductive material includes a tackifier, a reactive aid, an epoxy resin curing agent, a metal oxide, a photoinitiator, a sensitizer, and curing, if necessary. Agents, vulcanizers, deterioration inhibitors, heat resistant additives, heat conduction improvers, softeners, colorants, various coupling agents, metal deactivators and the like can be blended.

In the conductive material, the amount of the conductive particles used may be appropriately determined according to the intended use, but from the viewpoint of facilitating electrical conduction without contacting the conductive particles, for example, 100 mass of the conductive material. It is preferably 0.01 parts by mass or more and 50 parts by mass or less, particularly preferably 0.03 parts by mass or more and 40 parts by mass or less.

Among the above-mentioned forms of the conductive material, the conductive particles of the present invention are particularly preferably 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 has an insulating property 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. Further, there are a so-called semi-thermosetting type, a composite type of a thermosetting type and an ultraviolet curable type, and the like, which show intermediate properties between a thermoplastic type and a thermosetting type. These 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. In particular, an adhesive resin composed of a thermosetting resin is preferable because it has excellent material strength after bonding.

Specific examples of the adhesive resin 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 and the like. Examples thereof include those prepared by using the one obtained by the above combination as the main agent. Of these, styrene-butadiene rubber, SEBS, and the like are preferable as the thermoplastic resin because they have excellent reworkability. As the 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.

As the epoxy resin, a commonly used epoxy resin can be used as long as it is a polyvalent epoxy resin having two or more epoxy groups in one molecule. Specific examples include novolak resins such as phenol novolac and cresol novolak, 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, and aniline, polyhydric carboxy compounds such as adipic acid, phthalic acid, and isophthalic acid, etc., and epichlorhydrin 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.

As the above-mentioned various adhesive resins, it is preferable to use high-purity products in which impurity ions (Na, Cl, etc.) and hydrolyzable chlorine are reduced, from the viewpoint of preventing ion migration.

The amount of the conductive particles 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 to 20 parts by mass with respect to 100 parts by mass of the adhesive resin component. It is a department. When the amount of the conductive particles used is within this range, it is possible to suppress the increase in connection resistance and melt viscosity, improve the connection reliability, and sufficiently secure the anisotropy of the connection.

In addition to the above-mentioned conductive particles and the adhesive resin, the above-mentioned anisotropic conductive adhesive may contain additives known in the art. The blending amount may 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.

Examples of the tackifier include rosin, rosin derivative, terpene resin, terpene phenol resin, petroleum resin, kumaron-inden resin, styrene resin, isoprene resin, alkylphenol resin, xylene resin and the like. Examples of the reactive auxiliary agent, that is, the cross-linking agent, include polyols, isocyanates, melamine resins, urea resins, utropines, amines, acid anhydrides, peroxides and the like. The epoxy resin curing agent can be used without particular limitation as long as it has two or more active hydrogens in one minute. Specific examples thereof include polyamino compounds such as diethylenetriamine, triethylenetetramine, metaphenylenediamine, dicyandiamide and polyamideamine; organic acid anhydrides such as phthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride and pyromellitic anhydride. Substances; Novolac resins such as phenol novolac and cresol novolak can be mentioned. These can be used alone or in admixture of two or more. Further, a latent curing agent may be used if necessary. Examples of the latent curing agent that can be used 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 by using a manufacturing apparatus usually used in the technical field. For example, conductive particles, an adhesive resin, and if necessary, a curing agent and various additives are blended, and if the adhesive resin is a thermosetting resin, it is mixed in an organic solvent, and if it is a thermoplastic resin, it is bonded. It is produced by melt-kneading at a temperature equal to or higher than the softening point of the agent resin, specifically preferably at about 50 to 130 ° C, more preferably about 60 to 110 ° C. The anisotropic conductive adhesive thus obtained may be applied or may be applied in the form of a film.

The connection structure according to the present invention is obtained by connecting two circuit boards to each other using the conductive particles according to the present invention or the conductive material according to the present invention. Examples of the form of the connection structure include a connection structure between a flexible printed substrate and a glass substrate, a connection structure between a semiconductor chip and a flexible printed substrate, a connection structure between a semiconductor chip and a glass substrate, and the like.

Hereinafter, the present invention will be further described with reference to Examples. However, the scope of the present invention is not limited to these examples.

The characteristics in the example were measured by the following method.
(1) Elemental analysis of the surface of the conductive layer Using a scanning Auger electron spectroscopic analyzer (PHI710, manufactured by ULVAC Phi Co., Ltd.), carbon, oxygen, phosphorus, boron and carbon, oxygen, phosphorus, boron and within 5 nm in the depth direction from the surface of the conductive particles The atomic% of nickel was calculated.
(2) Ion analysis of the surface of the conductive layer Using a flight-time type secondary ion mass analyzer (TOF-SIMS5 type manufactured by ION-TOF), conductive particles are spread uniformly and evenly on the substrate, and the vicinity of the center thereof is 200 μm. ^{With respect to the count intensity of positive Ni ions (Ni +} : mass number 57.94) within 1 nm in the depth direction from the surface of the conductive particles under the conditions that the primary ion source is Bi ^{3+ and the acceleration voltage is 30 kV in all directions.} Positive ions derived from amine compounds (CH ₄ N ⁺ _{: mass number 30.03), negative ions derived from organic acids (C 2} H ₃ O ₂ ⁻ : mass relative to the count intensity of negative ions of Ni (mass number 57.94) the number 59.01), negative ions (Ni of Ni ^-: negative ions derived from phosphoric acid compound to the count intensity of mass number 57.94) (PO ₂ ^-: mass number 62.96), and Ni ^- of negative ions Negative ions derived from borate compounds (B ₂ O ₄ H ₃ ⁻ : mass number 89.02 and B ₃ O ₆ H ₄ ⁻ : mass number 133.03) with respect to the count intensity were measured.
(3) 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 10,000 times, and the arithmetic average value is the average particle. The diameter was set.
(4) Thickness of Conductive Layer The conductive particles were cut into two pieces, and the cross section of the cut end was observed and measured with a scanning electron microscope (SEM).

[Example 1]
(1) Pretreatment Spherical styrene-acrylate-silica composite resin particles having an average particle diameter of 3.0 μm 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 aqueous conditioner 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. 0.1 g of stannous chloride was added to this slurry. After stirring at room temperature for 5 minutes, a sensitization treatment was performed in which tin ions were adsorbed on the surface of the core material particles. Subsequently, this aqueous solution was filtered, and the core material particles washed once with ripulp 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 captured on the surface of the core material particles. Subsequently, 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 applying ultrasonic waves to pretreated the core material. A slurry of particles was obtained.
(2) Preparation of plating bath 5 g / L sodium tartrate, 2 g / L nickel sulfate hexahydrate, 10 g / L trisodium citrate, 0.1 g / L sodium hypophosphite, and 2 g / L 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.
(3) 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.
To this slurry, 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 an addition rate of 2.5 mL / min. Separation and addition were continuously performed by a pump, and electroless plating was started.
After adding the entire amount of each of the aqueous solution of nickel sulfate and the mixed aqueous solution of sodium hypophosphite and sodium hydroxide, stirring was continued for 5 minutes while maintaining the temperature of 70 ° C. Then, the liquid was filtered, the filtrate was washed three times, and then dried in a vacuum dryer at 110 ° C. to obtain conductive particles having a nickel-phosphorus alloy film. The average particle size of the obtained conductive particles was 3.22 μm, the thickness of the conductive layer was 110 nm, and the conductive particles had protrusions.
(4) Vacuum heat treatment The obtained conductive particles were placed in a square container so as to have a thickness of 5 mm. This was placed in a vacuum heating furnace (KDF-75, manufactured by Denken Hydental Co., Ltd.) and heat-treated at 390 ° C. for 2 hours under a vacuum of 10 Pa. After the heat treatment, the particles were allowed to cool to room temperature to obtain heat-treated conductive particles. The average particle size of the obtained conductive particles was 3.22 μm, the thickness of the conductive layer was 110 nm, and the conductive particles had protrusions. The elemental analysis results on the surface of the conductive layer are shown in Table 1, and the ion analysis results are shown in Table 2.

[Example 2]
The vacuum heat treatment (4) in Example 1 was carried out by the following operation. The conductive particles obtained by the (3) electroless plating treatment of Example 1 were placed in a square container so as to have a thickness of 5 mm. This was placed in a heating furnace (KDF-75, manufactured by Denken Hydental Co., Ltd.) and heat-treated at 390 ° C. for 2 hours under a vacuum of 100 Pa. After the heat treatment, the particles were allowed to cool to room temperature to obtain heat-treated conductive particles. The average particle size of the obtained conductive particles was 3.22 μm, the thickness of the conductive layer was 110 nm, and the conductive particles had protrusions. The elemental analysis results on the surface of the conductive layer are shown in Table 1, and the ion analysis results are shown in Table 2.

[Example 3]
The vacuum heat treatment (4) in Example 1 was carried out by the following operation. The conductive particles obtained by the (3) electroless plating treatment of Example 1 were placed in a square container so as to have a thickness of 5 mm. This was placed in a heating furnace (KDF-75, manufactured by Denken Hydental Co., Ltd.) and heat-treated at 320 ° C. for 2 hours under a vacuum of 10 Pa. After the heat treatment, the particles were allowed to cool to room temperature to obtain heat-treated conductive particles. The average particle size of the obtained conductive particles was 3.22 μm, the thickness of the conductive layer was 110 nm, and the conductive particles had protrusions. The elemental analysis results on the surface of the conductive layer are shown in Table 1, and the ion analysis results are shown in Table 2.

[Comparative Example 1]
The conductive particles obtained by the (3) electroless plating treatment of Example 1 were used as the conductive particles of Comparative Example 1. The elemental analysis results on the surface of the conductive layer are shown in Table 1, and the ion analysis results are shown in Table 2.

[Comparative Example 2]
The following operation was performed instead of (4) vacuum heat treatment in Example 1. The conductive particles obtained by the (3) electroless plating treatment of Example 1 were placed in a square container so as to have a thickness of 5 mm. This was placed in a heating furnace (KDF-75, manufactured by Denken Hydental Co., Ltd.) and heat-treated at 260 ° C. for 2 hours under normal pressure in a nitrogen atmosphere. After the heat treatment, the particles were allowed to cool to room temperature to obtain heat-treated conductive particles. The average particle size of the obtained conductive particles was 3.22 μm, the thickness of the conductive layer was 110 nm, and the conductive particles had protrusions. The elemental analysis results on the surface of the conductive layer are shown in Table 1, and the ion analysis results are shown in Table 2.

[Comparative Example 3]
The following operation was performed instead of (4) vacuum heat treatment in Example 1. The conductive particles obtained by the (3) electroless plating treatment of Example 1 were placed in a square container so as to have a thickness of 5 mm. This was placed in a heating furnace (KDF-75, manufactured by Denken Hydental Co., Ltd.) and heat-treated at 390 ° C. for 2 hours under normal pressure in a nitrogen atmosphere. After the heat treatment, the particles were allowed to cool to room temperature to obtain heat-treated conductive particles. The average particle size of the obtained conductive particles was 3.22 μm, the thickness of the conductive layer was 110 nm, and the conductive particles had protrusions. The elemental analysis results on the surface of the conductive layer are shown in Table 1, and the ion analysis results are shown in Table 2.

[Example 4]
(1) Pretreatment Spherical styrene-acrylate-silica composite resin particles having an average particle diameter of 3.0 μm 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 aqueous conditioner 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. 0.1 g of stannous chloride was added to this slurry. After stirring at room temperature for 5 minutes, a sensitization treatment was performed in which tin ions were adsorbed on the surface of the core material particles. Subsequently, this aqueous solution was filtered, and the core material particles washed once with ripulp 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 captured on the surface of the core material particles. Subsequently, 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 applying ultrasonic waves to pretreated the core material. A slurry of particles was obtained.
(2) Preparation of plating bath 5 g / L sodium tartrate, 2 g / L nickel sulfate hexahydrate, 10 g / L 3 sodium citrate, 0.1 g / L dimethylamine borane, and 2 g / L polyethylene A 3L electroless nickel-boron plating bath consisting of an aqueous solution in which glycol was dissolved was prepared and heated to 70 ° C.
(3) 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.
To this slurry, 420 mL of a 224 g / L nickel sulfate aqueous solution and 420 mL of a mixed aqueous solution containing 120 g / L of dimethylamine borane and 80 g / L of sodium hydroxide were added at a rate of 2.5 mL / min by a metering pump. Electroless plating was started by continuously separating and adding.
After adding the entire amount of each of the aqueous solution of nickel sulfate and the mixed aqueous solution of dimethylamine borane and sodium hydroxide, stirring was continued for 5 minutes while maintaining the temperature of 70 ° C. Then, the liquid was filtered, the filtrate was washed three times, and then dried in a vacuum dryer at 110 ° C. to obtain conductive particles having a nickel-boron alloy film. The average particle size of the obtained conductive particles was 3.22 μm, the thickness of the conductive layer was 110 nm, and the conductive particles had protrusions.
(4) Vacuum heat treatment The obtained conductive particles were placed in a square container so as to have a thickness of 5 mm. This was placed in a vacuum heating furnace (KDF-75, manufactured by Denken Hydental Co., Ltd.) and heat-treated at 390 ° C. for 2 hours under a vacuum of 10 Pa. After the heat treatment, the particles were allowed to cool to room temperature to obtain heat-treated conductive particles. The average particle size of the obtained conductive particles was 3.22 μm, the thickness of the conductive layer was 110 nm, and the conductive particles had protrusions. The elemental analysis results on the surface of the conductive layer are shown in Table 1, and the ion analysis results are shown in Table 2.

[Example 5]
The vacuum heat treatment (4) in Example 4 was carried out by the following operation. The conductive particles obtained by the (3) electroless plating treatment of Example 4 were placed in a square container so as to have a thickness of 5 mm. This was placed in a heating furnace (KDF-75, manufactured by Denken Hydental Co., Ltd.) and heat-treated at 390 ° C. for 2 hours under a vacuum of 100 Pa. After the heat treatment, the particles were allowed to cool to room temperature to obtain heat-treated conductive particles. The average particle size of the obtained conductive particles was 3.22 μm, the thickness of the conductive layer was 110 nm, and the conductive particles had protrusions. The elemental analysis results on the surface of the conductive layer are shown in Table 3, and the ion analysis results are shown in Table 4.

[Example 6]
The vacuum heat treatment (4) in Example 4 was carried out by the following operation. The conductive particles obtained by the (3) electroless plating treatment of Example 4 were placed in a square container so as to have a thickness of 5 mm. This was placed in a heating furnace (KDF-75, manufactured by Denken Hydental Co., Ltd.) and heat-treated at 320 ° C. for 2 hours under a vacuum of 10 Pa. After the heat treatment, the particles were allowed to cool to room temperature to obtain heat-treated conductive particles. The average particle size of the obtained conductive particles was 3.22 μm, the thickness of the conductive layer was 110 nm, and the conductive particles had protrusions. The elemental analysis results on the surface of the conductive layer are shown in Table 3, and the ion analysis results are shown in Table 4.

[Comparative Example 4]
The conductive particles obtained by the (3) electroless plating treatment of Example 4 were used as the conductive particles of Comparative Example 4. The elemental analysis results on the surface of the conductive layer are shown in Table 3, and the ion analysis results are shown in Table 4.

[Comparative Example 5]
The following operation was performed instead of (4) vacuum heat treatment in Example 4. The conductive particles obtained by the (3) electroless plating treatment of Example 4 were placed in a square container so as to have a thickness of 5 mm. This was placed in a heating furnace (KDF-75, manufactured by Denken Hydental Co., Ltd.) and heat-treated at 260 ° C. for 2 hours under normal pressure in a nitrogen atmosphere. After the heat treatment, the particles were allowed to cool to room temperature to obtain heat-treated conductive particles. The average particle size of the obtained conductive particles was 3.22 μm, the thickness of the conductive layer was 110 nm, and the conductive particles had protrusions. The elemental analysis results on the surface of the conductive layer are shown in Table 3, and the ion analysis results are shown in Table 4.

[Comparative Example 6]
The following operation was performed instead of (4) vacuum heat treatment in Example 4. The conductive particles obtained by the (3) electroless plating treatment of Example 4 were placed in a square container so as to have a thickness of 5 mm. This was placed in a heating furnace (KDF-75, manufactured by Denken Hydental Co., Ltd.) and heat-treated at 390 ° C. for 2 hours under normal pressure in a nitrogen atmosphere. After the heat treatment, the particles were allowed to cool to room temperature to obtain heat-treated conductive particles. The average particle size of the obtained conductive particles was 3.22 μm, the thickness of the conductive layer was 110 nm, and the conductive particles had protrusions. The elemental analysis results on the surface of the conductive layer are shown in Table 3, and the ion analysis results are shown in Table 4.

[Evaluation of storage stability and corrosion resistance]
(1) Storage stability and corrosion resistance of conductive particles Using the conductive particles of Examples and Comparative Examples, the storage stability and corrosion resistance of the conductive particles were evaluated by the following methods.
The conductive particles obtained in Examples and Comparative Examples were stored at room temperature (25 ° C., 50% RH) for the time shown in Table 2, and then the conductive particles were placed in a vertically standing resin cylinder having an inner diameter of 10 mm. The volume resistance value between the upper and lower electrodes was determined by adding 1.0 g of particles and applying a load of 2 kN at room temperature (25 ° C., 50% RH). The results are shown in Table 5.

From this result, it can be seen that the conductive particles obtained in the examples have a smaller increase in volume resistance value than the conductive particles obtained in the comparative example, and are excellent in storage stability and corrosion resistance.

(2) Storage stability of the conductive material Using the conductive particles of Examples and Comparative Examples, a conductive material was prepared by the following method, and the storage stability of the conductive material was evaluated by a pressure cooker test.
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 was mixed with 15 parts by mass of the conductive particles obtained in Examples and Comparative Examples to obtain a paste. This paste was applied onto a silicone treated polyester film using a bar coater and then 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 copper patterns are formed at a pitch of 50 μm to prepare a connection structure and perform electrical connection. , The connection resistance value of this connection structure was measured at room temperature (25 ° C., 50% RH). Then, the connection structure was arranged in a closed container, and a pressure cooker test was conducted in which the connection structure was treated in an environment of a temperature of 121 ° C., a relative humidity of 100%, and 2 atm for 10 hours. After the pressure cooker test, the connection resistance value of the connection structure was measured at room temperature (25 ° C., 50% RH). It can be evaluated that the smaller the difference between the connection resistance values before and after the pressure cooker test, the higher the storage stability of the conductive material. The results are shown in Table 6.

From this result, it can be seen that the conductive material obtained in the example has a smaller difference in connection resistance value before and after the pressure cooker test than the conductive material obtained in the comparative example, and is excellent in storage stability. ..

[Evaluation of connection resistance and connection reliability]
Using the conductive particles of Examples and Comparative Examples, the connection resistance and connection reliability were evaluated by the following methods.
1.0 g of the conductive particles obtained in Examples and Comparative Examples were placed in a vertically standing resin cylinder having an inner diameter of 10 mm, and a load of 2 kN was applied at room temperature (25 ° C., 50% RH). The electrical resistance between the upper and lower electrodes was measured, and the initial volume resistance value was obtained. The lower the initial volume resistance value, the more effectively the oxide film formed on the electrode can be eliminated, and it can be evaluated that the connection resistance of the conductive particles is low.
Furthermore, the resistance value after holding for 24 hours under the conditions of 85 ° C. and 85% RH was also measured. It can be evaluated that the smaller the difference from the connection resistance value at room temperature, the better the connection reliability of the conductive particles. The results are shown in Table 7.

From this result, it can be seen that the conductive particles obtained in the examples have a lower initial volume resistance value and lower connection resistance than the conductive particles obtained in the comparative example. Further, the conductive particles obtained in the examples had a smaller difference between the initial volume resistance value and the resistance value after 24 hours at 85 ° C. and 85% RH as compared with the conductive particles obtained in the comparative example. It can be seen that the connection reliability is high. In particular, when the conductive particles obtained in Examples 1 and 2 on which the nickel-phosphorus plating layer is formed and the conductive particles obtained in Comparative Example 3 are compared, they are connected by heating under vacuum. It can be seen that conductive particles having low resistance and excellent connection reliability can be obtained. Further, when the conductive particles obtained in Examples 4 and 5 on which the nickel-boron plated layer is formed and the conductive particles obtained in Comparative Example 6 are compared, they are connected by heating under vacuum. It can be seen that conductive particles having low resistance and excellent connection reliability can be obtained.

Claims

In conductive particles in which a nickel-plated layer as a conductive layer is formed on the surface of core material particles.
The molar ratio of carbon to total nickel and phosphorus (C / (Ni + P)) within 5 nm of the surface of the conductive layer, or carbon to total nickel and boron, as measured by a scanning Auger electron spectroscopic analyzer. The molar ratio (C / (Ni + B)) is 0.0002 or more and 1.65 or less, and the molar ratio of oxygen to the total of nickel and phosphorus (O / (Ni + P)) or the molar ratio of oxygen to the total of nickel and boron. (O / (Ni + B)) is 0.0001 or more and 2.0 or less, and the molar ratio of phosphorus to nickel (P / Ni) or the molar ratio of boron to nickel (B / Ni) is 0.003 or more. Conductive particles that are 0.7 or less.
In conductive particles in which a nickel-plated layer as a conductive layer is formed on the surface of core material particles.
CH 4 N + positive ion count intensity (CH 4 N + positive ion count intensity with respect to Ni + positive ion count intensity within 1 nm in the depth direction from the surface of the conductive layer, as measured by a time-of-flight secondary ion mass spectrometer (TOF-SIMS). CH 4 N + / Ni + ) is 0.1 or less, or the count intensity of negative ions of C 2 H 3 O 2 − with respect to the count intensity of negative ions of Ni − (C 2 H 3 O 2 − / Ni −) ) or it is 10.0 or less, Ni - the PO 2 for counting the strength of the negative ion - negative ion count strength (PO 2 - / Ni -) is either 10.0 or less, or Ni - negative B 2 O for counting the strength of the ion 4 H 3 - and B 3 O 6 H 4 - negative ion count strength ((B 2 O 4 H 3 - + B 3 O 6 H 4 -) / Ni -) 10. Conductive particles that are 0 or less.
The conductive particles according to claim 1 or 2, wherein the thickness of the conductive layer is 5 nm or more and 2000 nm or less.
The conductive particle according to any one of claims 1 to 3, wherein the average particle size is 0.1 μm or more and 50 μm or less.
The conductive particle according to any one of claims 1 to 4, which has protrusions on the outer surface of the conductive layer.
The conductive particle according to any one of claims 1 to 4, wherein the outer surface of the conductive layer is smooth.
A conductive material containing the conductive particles according to any one of claims 1 to 6 and a binder resin.
A connection structure in which connected members are connected to each other via the conductive material according to claim 7.
The conductive particle according to any one of claims 1 to 6, further comprising a step of heating the conductive particle having a conductive layer on the surface of the core material particle at a temperature of 200 to 600 ° C. under a vacuum of 1000 Pa or less. Production method.
The method for producing conductive particles according to claim 9, wherein the conductive particles obtained by forming the conductive layer on the surface of the core material particles by an electroless plating method are heated.