JP2010103080A - Electroconductive fine particles, anisotropic electroconductive material and connecting structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide electroconductive fine particles that achieves electrical connection with high reliability. <P>SOLUTION: The electroconductive fine particles have nickel layers formed on surfaces of their base fine particles. The nickel layer has a nickel content rate of ≥96 wt.%, and its surface contact angle to water is ≥90° and its volume resistance is ≤0.0030 Ω cm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to conductive fine particles that can be electrically connected with high reliability. The present invention also relates to an anisotropic conductive material containing the conductive fine particles, and a connection structure connected by the conductive fine particles or the anisotropic conductive material.

An anisotropic conductive material in which conductive fine particles are dispersed in an insulating binder resin is used as an electrode connecting material. Examples of the anisotropic conductive material include an anisotropic conductive film, an anisotropic conductive sheet, and an anisotropic conductive adhesive. For example, an anisotropic conductive material is used by being sandwiched between electrodes of a substrate or an electronic component in order to electrically connect electrodes formed on the substrate. In particular, anisotropic conductive materials are widely used in electronic devices such as liquid crystal displays, personal computers, and mobile phones.

Conventionally, conductive fine particles having a gold plating layer formed on the surface have been used as the conductive fine particles. In Patent Document 1, an electroless plating layer is formed on the surface of a non-metallic material core material powder, and the electroless plating layer includes a gold plating layer positioned at the uppermost layer and a nickel layer adjacent to the gold plating layer. A conductive electroless plating powder having a multilayer structure is disclosed. It is disclosed that the use of such a conductive electroless plating powder allows electrical conduction between opposing electrodes.

However, when an anisotropic conductive material in which conductive fine particles having a gold plating layer formed on the surface are dispersed is used to connect between electrodes of a substrate or an electronic component, an insulating binder resin is formed between the conductive fine particles and the electrodes. There was a problem that remained. Further, the conductive fine particles having the gold plating layer formed on the surface cannot break through the oxide film formed on the surface of the electrode, and there is a problem that the connection resistance value between the electrodes may be increased. These problems are considered because gold is a relatively soft metal.

Therefore, conductive fine particles having a conductive layer formed of a metal harder than gold have been studied. Patent Document 2 discloses a conductive electroless plating powder in which a nickel coating is formed on the surface of a core powder by an electroless plating method. However, since nickel is more easily oxidized than gold, such a conductive electroless plating powder has a problem that electrical connection with high reliability cannot be achieved.

JP 2004-238730 A JP 2004-131800 A

An object of this invention is to provide the electroconductive fine particles which can perform electrical connection with high reliability. Another object of the present invention is to provide an anisotropic conductive material containing the conductive fine particles, and a connection structure connected by the conductive fine particles or the anisotropic conductive material.

The present invention is a conductive fine particle having a nickel layer formed on the surface of the base particle, wherein the nickel layer has a nickel content of 96% by weight or more, a surface contact angle with water of 90 ° or more, and The conductive fine particles have a volume resistivity of 0.0030 Ω · cm or less.
The present invention is described in detail below.

The present inventor conducted the surface treatment so that the surface contact angle with respect to water is 90 ° or more even when the conductive fine particles have a nickel layer formed on the surface of the substrate fine particles. It was found that can be prevented. This is considered to be because the contact of moisture that causes oxidation can be minimized by setting the surface contact angle to water to a certain level or more. However, when surface treatment is performed to adjust the surface contact angle, the conductive connectivity may be impaired. The inventor achieves both suppression of oxidation and conductive connectivity by performing a surface treatment such that the surface contact angle with respect to water is 90 ° or more and the volume resistivity is 0.0030 Ω · cm or less. Thus, the inventors have found that electrical connection with high reliability can be performed, and completed the present invention.

The conductive fine particles of the present invention have a nickel layer formed on the surface of the substrate fine particles, and the lower limit of the surface contact angle with water is 90 °. When the surface contact angle with respect to water is less than 90 °, the nickel layer is likely to be oxidized, and highly reliable electrical connection cannot be performed. A preferable lower limit of the surface contact angle with respect to water is 100 °, and a more preferable lower limit is 110 °. Although there is no particular upper limit for the surface contact angle with water, the upper limit is substantially about 160 °.

The surface contact angle of the conductive fine particles with respect to water can be measured using, for example, a fully automatic contact angle measuring device (“OCA35” manufactured by Data Physics Co., Ltd.). 1 g of conductive fine particles are placed on a slide glass, the needle is brought close to the surface of the conductive fine particles, and 3 μL of pure water is attached to the surface of the conductive fine particles using the needle. The surface contact angle can be measured by analyzing an image obtained by photographing conductive fine particles to which pure water is adhered.

The conductive fine particles of the present invention have a volume resistivity of 0.0030 Ω · cm or less. When the volume resistivity exceeds 0.0030Ω, highly reliable electrical connection cannot be performed. A preferable upper limit of the volume resistivity is 0.0025 Ω · cm. There is no particular lower limit for the volume resistivity, but the lower limit is substantially about 0.0010 Ω · cm.

In the present specification, the volume resistivity can be measured using a “powder resistivity measurement system” manufactured by Mitsubishi Chemical Corporation. The volume resistivity means the volume resistivity when a load of 20 kN is applied to 2.5 g of conductive fine particles.

The substrate fine particles are not particularly limited, and examples thereof include resin fine particles, inorganic fine particles, organic-inorganic hybrid fine particles, and metal fine particles.
The resin fine particles are not particularly limited, and include, for example, polyolefin resin, acrylic resin, polyalkylene terephthalate resin, polysulfone resin, polycarbonate resin, polyamide resin, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, and the like. Resin fine particles.
The polyolefin resin is not particularly limited, and examples thereof include polyethylene resin, polypropylene resin, polystyrene resin, polyisobutylene resin, and polybutadiene resin. The acrylic resin is not particularly limited, and examples thereof include polymethyl methacrylate resin and polymethyl acrylate resin. These resins may be used alone or in combination of two or more.

The inorganic fine particles are not particularly limited, and examples thereof include fine particles composed of metal oxides such as silica and alumina. The organic-inorganic hybrid fine particles are not particularly limited, and examples thereof include hybrid fine particles containing an acrylic polymer in an organosiloxane skeleton. The metal fine particles are not particularly limited, and examples thereof include metal fine particles containing copper.

A preferred lower limit of the 10% K value of the resin fine particles 1000 N / mm ^2, the upper limit is preferably 15000 N / mm ^2. If the 10% K value is less than 1000 N / mm ² , the resin fine particles may be destroyed when the resin fine particles are compressed and deformed. When the 10% K value exceeds 15000 N / mm ² , the conductive fine particles may damage the electrode. A more preferred lower limit of the 10% K value 2000N / mm ^2, and more preferable upper limit is 10000 N / mm ^2.

The 10% K value is obtained by using a micro compression tester (for example, “PCT-200” manufactured by Shimadzu Corporation), and using a smooth indenter end face of a diamond cylinder having a diameter of 50 μm and a compression speed of 2.6 mN / The compression displacement (mm) when compressed under conditions of seconds and a maximum test load of 10 g can be measured and determined by the following equation.
K value ^{(N / mm 2) = (} 3 / √2) · F · S -3/2 · R -1/2
F: Load value at 10% compression deformation of resin fine particles (N)
S: Compression displacement (mm) in 10% compression deformation of resin fine particles
R: radius of resin fine particles (mm)

The average particle diameter of the substrate fine particles is not particularly limited, but a preferable lower limit is 0.5 μm and a preferable upper limit is 100 μm. When the average particle size of the base material particles is less than 0.5 μm, the base material particles are likely to aggregate. Therefore, the conductive fine particles in which the nickel layer is formed on the surface of the aggregated base material particles are short-circuited between adjacent electrodes. There are things to do. If the average particle diameter of the substrate fine particles exceeds 100 μm, the nickel layer tends to be peeled off from the surface of the substrate fine particles, so that the connection reliability may be lowered. The more preferable lower limit of the average particle diameter of the substrate fine particles is 1 μm, and the more preferable upper limit is 20 μm.
The average particle size of the above-mentioned substrate fine particles is obtained by measuring the particle size of 50 randomly selected substrate fine particles using an optical microscope or an electron microscope and arithmetically averaging the measured particle sizes. Can do.

The coefficient of variation of the average particle diameter of the substrate fine particles is not particularly limited, but is preferably 10% or less. If the coefficient of variation exceeds 10%, the connection reliability of the conductive fine particles may be lowered. The coefficient of variation is a numerical value obtained by dividing the standard deviation obtained from the particle size distribution by the average particle size and expressed as a percentage (%).

The shape of the substrate fine particles is not particularly limited as long as the distance between the opposing electrodes can be maintained, but a true spherical shape is preferable. Further, the surface of the substrate fine particles may be smooth or may have a protrusion.

The nickel content of the nickel layer is 96% by weight or more. When the nickel content is less than 96% by weight, the connection resistance value of the conductive fine particles is increased, so that highly reliable electrical connection cannot be achieved. Further, the nickel layer is easily oxidized. The nickel content is preferably 97% by weight or more, and more preferably 99% by weight or more. In addition, the nickel content rate of the said nickel layer is the numerical value which showed the ratio of the weight of nickel to the total weight of the element contained in a nickel layer in percentage (%).

The nickel layer may contain an element other than nickel. The elements other than nickel are not particularly limited, and examples thereof include phosphorus, boron, cobalt, tungsten, and the like. The content of elements other than nickel in the nickel layer is not particularly limited as long as it is 4% by weight or less, but the content of elements other than nickel is preferably 3% by weight or less, and is preferably 1% by weight or less. It is more preferable.
The nickel content of the nickel layer is determined using a high frequency inductively coupled plasma emission spectrometer (“ICP-AES” manufactured by Horiba, Ltd.), a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu), or the like. Can be measured.

The nickel layer may be directly formed on the surface of the substrate fine particles. In the nickel layer, a base metal layer may be formed between the nickel layer and the substrate fine particles.
The metal constituting the base metal layer is not particularly limited. For example, gold, silver, copper, platinum, zinc, iron, tin, lead, aluminum, cobalt, indium, chromium, titanium, antimony, bismuth, germanium, cadmium, etc. Is mentioned.

Although the thickness of the said nickel layer is not specifically limited, A preferable minimum is 0.005 micrometer and a preferable upper limit is 3 micrometers. When the thickness of the nickel layer is less than 0.005 μm, the connection resistance value of the conductive fine particles may increase. When the thickness of the nickel layer exceeds 3 μm, the flexibility of the conductive fine particles may be impaired. The minimum with more preferable thickness of the said nickel layer is 0.08 micrometer, and a more preferable upper limit is 0.3 micrometer.
The thickness of the nickel layer is a thickness obtained by observing a section of 10 randomly selected conductive fine particles with a scanning electron microscope (SEM) and measuring the thickness and arithmetically averaging the measured values. is there.

In the conductive fine particles of the present invention, it is preferable that a metal oxide layer containing cerium or titanium is formed on the surface of the nickel layer. When a metal oxide layer containing cerium or titanium is formed on the surface of the nickel layer, the nickel layer does not directly contact oxygen. As a result, oxidation of the nickel layer can be more effectively prevented. Among these, it is more preferable that a metal oxide layer containing cerium is formed on the surface of the nickel layer. Since the metal oxide layer containing cerium has a self-healing function, even if cracks occur in the nickel layer, it is excellent in the effect of preventing oxidation inside the nickel layer.
In addition, although the said metal oxide layer should just contain a cerium oxide or a titanium oxide at least, it is preferable that it is substantially comprised with the cerium oxide or the titanium oxide.

The thickness of the metal oxide layer containing cerium or titanium is not particularly limited, but a preferable lower limit is 0.005 μm and a preferable upper limit is 0.05 μm. When the thickness of the metal oxide layer is less than 0.005 μm, oxidation of the nickel layer may not be prevented. When the thickness of the metal oxide layer exceeds 0.05 μm, the connection resistance value of the conductive fine particles may increase. The more preferable lower limit of the thickness of the metal oxide layer is 0.01 μm, and the more preferable upper limit is 0.03 μm.
The thickness of the metal oxide layer is a thickness obtained by observing a section of 10 randomly selected conductive fine particles with a scanning electron microscope (SEM) and measuring the thickness and arithmetically averaging the measured values. That's it.

The method of forming the metal oxide layer containing cerium on the surface of the nickel layer is not particularly limited, but there is a method of adding the substrate fine particles on which the nickel layer is formed to an aqueous solution in which the cerium compound is dissolved. Can be mentioned. The method of forming the titanium-containing metal oxide layer on the surface of the nickel layer is not particularly limited, but the method of adding the substrate fine particles on which the nickel layer is formed to the aqueous solution in which the titanium compound is dissolved. Etc.

The cerium compound is not particularly limited, and examples thereof include cerium sulfate, cerium chloride, cerium nitrate, and cerium stearate. The titanium compound is not particularly limited, and examples thereof include potassium potassium oxalate, titanium sulfate, and titanium chloride.

In order for the surface contact angle of the conductive fine particles of the present invention to water to be 100 ° or more and the volume resistivity to be 0.0030 Ω · cm or less, the nickel layer (a metal oxide layer is formed on the nickel layer) In the case where it is applied, the surface of the metal oxide layer) needs to be subjected to surface treatment.
Although the said surface treatment is not specifically limited, For example, the method of making the surface of the said nickel layer or the said metal oxide layer react and couple | bond with the compound which has a C6-C22 alkyl group is mentioned. The nickel layer or metal oxide layer to which the compound having an alkyl group having 6 to 22 carbon atoms is bonded is hydrophobic and has a surface contact angle with water of 100 ° or more, while the conductivity is not lowered so much. The volume resistivity can be 0.0030 Ω · cm or less.

The lower limit of the carbon number of the alkyl group of the compound having an alkyl group having 6 to 22 carbon atoms is 6, and the upper limit is 22. When the carbon number of the alkyl group is less than 6, the surface contact angle of the obtained conductive fine particles cannot be 100 ° or more, the nickel layer is easily oxidized, and highly reliable electrical connection is performed. May not be possible. When the alkyl group has more than 22 carbon atoms, the conductivity of the obtained conductive fine particles may be reduced, and reliable electrical connection may not be performed. The upper limit with preferable carbon number of the said alkyl group is 16.
The alkyl group may be a linear alkyl group or a branched alkyl group, but is preferably a linear alkyl group.

Although the said compound which has a C6-C22 alkyl group is not specifically limited, The phosphate ester which has a C6-C22 alkyl group, or its salt, The alkoxysilane which has a C6-C22 alkyl group At least one selected from the group consisting of an alkylthiol having an alkyl group having 6 to 22 carbon atoms and a dialkyl disulfide having an alkyl group having 6 to 22 carbon atoms is preferable.

Examples of the phosphoric acid ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof include hexyl phosphate, heptyl phosphate, monooctyl phosphate, monononyl phosphate, monodecyl phosphate, Monoundecyl phosphate, monododecyl phosphate, monotridecyl phosphate, monotetradecyl phosphate, monopentadecyl phosphate, monohexyl phosphate monosodium salt, monoheptyl phosphate monosodium Salt, monooctyl phosphate monosodium salt, monononyl phosphate monosodium salt, monodecyl phosphate monosodium salt, monoundecyl phosphate monosodium salt, monododecyl phosphate monosodium salt, phosphorus Mono tridecyl ester monosodium salt, phosphate acid mono tetradecyl ester monosodium salt, monocalcium phosphate pentadecyl ester monosodium salt.

The method of reacting the phosphate ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof on the surface of the nickel layer or the metal oxide layer is not particularly limited. For example, the nickel layer or the metal oxide Examples include a method in which an aqueous solution of a phosphate ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof is attached to the substrate fine particles on which the physical layer is formed. By attaching an aqueous solution of a phosphoric ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof to the substrate fine particles on which the nickel layer or the metal oxide layer is formed, the nickel layer or the metal The nickel or metal oxide on the surface of the oxide layer reacts with the phosphate ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof, and the carbon number on the surface of the nickel layer or metal oxide layer. Is bound to a phosphate ester having an alkyl group of 6 to 22 or a salt thereof.
The concentration of the phosphate ester in the aqueous solution of the phosphate ester or a salt thereof is not particularly limited, but the preferred lower limit of the phosphate ester concentration is 0.5% by weight, and the preferred upper limit is 3% by weight.
In addition, the said phosphate ester aqueous solution may contain organic solvents, such as alcohol, such as tetrahydrofuran and methanol, ethanol, and propanol.

Examples of the alkoxysilane having an alkyl group having 6 to 22 carbon atoms include hexyltrimethoxysilane, hexyltriethoxysilane, heptyltrimethoxysilane, heptyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, nonyltri. Methoxysilane, nonyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, undecyltrimethoxysilane, undecyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, tridecyltrimethoxysilane, tridecyltriethoxy Examples include silane, tetradecyltrimethoxysilane, tetradecyltriethoxysilane, pentadecyltrimethoxysilane, and pentadecyltriethoxysilane.

The method of coating the surface of the nickel layer or the metal oxide layer with the alkoxysilane having an alkyl group having 6 to 22 carbon atoms is not particularly limited, but the nickel layer or the metal oxide layer was formed. The method etc. which adhere the aqueous solution of the alkoxysilane which has the said C6-C22 alkyl group to base-material microparticles | fine-particles are mentioned. By adhering an aqueous solution of an alkoxysilane having an alkyl group having 6 to 22 carbon atoms to the substrate fine particles on which the nickel layer or the metal oxide layer is formed, the nickel layer or the metal oxide layer The surface is coated with an alkoxysilane having an alkyl group having 6 to 22 carbon atoms.
The concentration of the alkoxysilane in the alkoxysilane aqueous solution is not particularly limited, but the preferred lower limit of the alkoxysilane concentration is 0.5% by weight, and the preferred upper limit is 3% by weight.
In addition, the alkoxysilane aqueous solution which has the said C6-C22 alkyl group may contain organic solvents, such as alcohol, such as methanol, ethanol, and propanol.

Examples of the alkyl thiol having an alkyl group having 6 to 22 carbon atoms include hexyl thiol, heptyl thiol, octyl thiol, nonyl thiol, decyl thiol, undecyl thiol, dodecyl thiol, tridecyl thiol, tetradecyl thiol, pentadecyl Examples include thiol and hexadecyl thiol. The alkyl thiol preferably has a thiol group at the end of the alkyl chain.

The method of reacting the alkylthiol having an alkyl group having 6 to 22 carbon atoms on the surface of the nickel layer or the metal oxide layer is not particularly limited, but the group on which the nickel layer or the metal oxide layer is formed. Examples thereof include a method in which the fine particles are adhered to a solution in which the alkylthiol having an alkyl group having 6 to 22 carbon atoms is dissolved. The nickel layer or the metal is formed by adhering to the solution in which the alkyl thiol having an alkyl group having 6 to 22 carbon atoms is dissolved in the substrate fine particles on which the nickel layer or the metal oxide layer is formed. The nickel or metal oxide on the surface of the oxide layer reacts with the alkylthiol having an alkyl group having 6 to 22 carbon atoms, and the surface of the nickel layer or the metal oxide layer has 6 to 6 carbon atoms. An alkyl thiol having 22 alkyl groups is attached.
The concentration of the alkylthiol in the solution in which the alkylthiol is dissolved is not particularly limited, but the preferred lower limit of the alkylthiol concentration is 0.5% by weight, and the preferred upper limit is 3% by weight.
The solution in which the alkylthiol having an alkyl group having 6 to 22 carbon atoms is dissolved is not particularly limited as long as the alkylthiol dissolves, and contains an organic solvent such as alcohol such as methanol, ethanol, and propanol. May be.

Examples of the dialkyl disulfide having an alkyl group having 6 to 22 carbon atoms include dihexyl disulfide, diheptyl disulfide, dioctyl disulfide, dinonyl disulfide, didecyl disulfide, diundecyl disulfide, didodecyl disulfide, ditridecyl disulfide, ditetradecyl disulfide. Examples include decyl disulfide, dipentadecyl disulfide, and dihexadecyl disulfide.

The method of reacting the dialkyl disulfide having an alkyl group having 6 to 22 carbon atoms on the surface of the nickel layer or the metal oxide layer is not particularly limited, but the group in which the nickel layer or the metal oxide layer is formed. Examples thereof include a method in which the fine particles are adhered to a solution in which the dialkyl disulfide having an alkyl group having 6 to 22 carbon atoms is dissolved. The nickel layer or the metal is formed by attaching a solution in which the dialkyl disulfide having an alkyl group having 6 to 22 carbon atoms is dissolved to the substrate fine particles on which the nickel layer or the metal oxide layer is formed. Nickel or metal oxide on the surface of the oxide layer reacts with the dialkyl disulfide having an alkyl group having 6 to 22 carbon atoms, and the carbon number is 6 to 6 on the surface of the nickel layer or the metal oxide layer. A dialkyl disulfide having 22 alkyl groups is attached.
The concentration of the dialkyl disulfide in the solution in which the dialkyl disulfide is dissolved is not particularly limited, but the preferred lower limit of the dialkyl disulfide concentration is 0.5% by weight, and the preferred upper limit is 3% by weight.
The solution in which the dialkyl disulfide is dissolved is not particularly limited as long as the dialkyl disulfide is dissolved, and may contain an organic solvent such as alcohol such as methanol, ethanol, and propanol.

Among the surface treatment methods, the nickel layer or the metal oxide layer is reacted with the phosphoric acid ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof, the nickel layer or the metal. A method of reacting an alkylthiol having an alkyl group having 6 to 22 carbon atoms on the surface of the oxide layer, and an alkyl group having 6 to 22 carbon atoms on the surface of the nickel layer or the metal oxide layer. A method of reacting a dialkyl disulfide having a reaction is preferable, a method of reacting a phosphate ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof on the surface of the nickel layer or the metal oxide layer, and the nickel layer Or the method of making the surface of the said metal oxide layer react the said alkylthiol which has the said C6-C22 alkyl group is more preferable. How the number of carbon atoms on the surface of the nickel layer or the metal oxide layer reacting phosphoric acid ester or a salt thereof having an alkyl group of 6 to 22 is more preferred. In addition, the said surface contact angle and volume resistivity are the time which changes the carbon number of the compound which has the said C6-C22 alkyl group, or the compound which has the said C6-C22 alkyl group reacts. It can be adjusted by controlling the temperature or the like.

The manufacturing method of the electroconductive fine particles of this invention is not specifically limited, For example, it can manufacture with the following method.

A nickel layer is formed on the surface of the substrate fine particles so that the nickel content is 96% by weight or more. The method for forming the nickel layer on the surface of the substrate fine particles is not particularly limited, and examples thereof include methods such as an electrolytic plating method and an electroless plating method.
When a nickel layer is formed on the surface of the substrate fine particles using the electrolytic plating method, a nickel layer having a high nickel content can be formed. However, when the nickel layer is formed on the surface of the substrate fine particles having an average particle diameter of less than 100 μm using the electrolytic plating method, the substrate fine particles sometimes aggregate.

In addition, when a nickel layer is formed on the surface of the substrate fine particles using a conventional electroless plating method, phosphorus or boron derived from a reducing agent contained in the electroless plating bath may be included in the nickel layer. was there. If phosphorus or boron is contained in the nickel layer, the connection resistance value of the conductive fine particles is increased.
In the conventional electroless plating method, since the electroless nickel plating solution containing the reducing agent is dropped into the suspension in which the base particles are dispersed, the reducing agent concentration in the suspension is increased. Since the nickel layer contains phosphorus, boron, and the like derived from the reducing agent, the nickel content of the nickel layer may be low. In addition, in such an electroless plating method, it is difficult to increase the nickel content of the nickel layer even if the pH of the suspension or the liquid temperature is adjusted.
Therefore, in the present invention, in order to form a nickel layer having a high nickel content, it is preferable to perform the first plating step and the second plating step while keeping the concentration of the reducing agent in the electroless plating bath low. By performing electroless plating in such a process, a nickel layer having a high nickel content can be obtained.

In the present invention, in the electroless plating method, it is generally preferable to perform an electroless plating step after performing an etching step and a catalytic step.
The etching process is based on an oxidizing agent such as chromic acid, sulfuric acid-chromic acid mixture, permanganic acid solution, strong acid such as hydrochloric acid or sulfuric acid, or strong alkaline aqueous solution such as sodium hydroxide or potassium hydroxide. This is a process for forming minute irregularities on the surface of the material fine particles and improving the adhesion of the nickel layer.

The catalyzing step is a step of imparting a catalyst serving as a starting point of electroless plating to the surface of the substrate fine particles. In the catalyzing step, for example, a sensitizing step and an activating step are performed. As the sensitizing step, Sn ²⁺ ions are adsorbed on the surface of the substrate fine particles by immersing the etched substrate fine particles in a tin dichloride solution. As the above-mentioned activating step, the base material fine particles adsorbed with Sn ²⁺ ions are immersed in a palladium dichloride solution, whereby a palladium catalyst is imparted to the surface of the base material fine particles. In the activating process, a reaction represented by Sn ²⁺ + Pd ²⁺ → Sn ⁴⁺ + Pd ⁰ is performed on the surface of the base particle.

The electroless plating step involves immersing the substrate fine particles provided with a palladium catalyst in an electroless plating bath in the presence of a reducing agent, and depositing a plating metal on the surface of the substrate fine particles using the provided palladium catalyst as a starting point. It is the process of making it precipitate. In the electroless plating process, it is preferable to have an early plating process and a late plating process.
For example, in the electroless plating step, after the reaction in the previous plating step is stopped, the substrate fine particles on which the nickel layer is formed are washed. It is preferable to disperse the cleaned substrate fine particles in ion-exchanged water or the like that does not contain a reducing agent, and perform the late plating step. By having such a plating step, the content of phosphorus, boron, etc. contained in the nickel layer can be reduced.

An anisotropic conductive material can be produced by dispersing the conductive fine particles of the present invention in a binder resin. An anisotropic conductive material containing the conductive fine particles of the present invention and a binder resin is also one aspect of the present invention.

Examples of the anisotropic conductive material of the present invention include anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive adhesive, anisotropic conductive film, and anisotropic conductive sheet.

The binder resin is not particularly limited, but an insulating resin is used, and examples thereof include a vinyl resin, a thermoplastic resin, a curable resin, a thermoplastic block copolymer, and an elastomer.
Although the said vinyl resin is not specifically limited, For example, a vinyl acetate resin, an acrylic resin, a styrene resin etc. are mentioned.
Although the said thermoplastic resin is not specifically limited, For example, polyolefin resin, ethylene-vinyl acetate copolymer, a polyamide resin etc. are mentioned.
Although the said curable resin is not specifically limited, For example, an epoxy resin, a urethane resin, a polyimide resin, an unsaturated polyester resin etc. are mentioned. The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin, or a moisture curable resin. The curable resin may be used in combination with a curing agent.
The thermoplastic block copolymer is not particularly limited. For example, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated product of styrene-butadiene-styrene block copolymer, styrene -Hydrogenated product of isoprene-styrene block copolymer.
The elastomer is not particularly limited, and examples thereof include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.
These resins may be used alone or in combination of two or more.

In addition to the conductive fine particles of the present invention and the above-mentioned binder resin, the anisotropic conductive material of the present invention is, for example, an extender, a plasticizer, and improved adhesiveness within a range that does not hinder the achievement of the present invention. Agents, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants, flame retardants, organic solvents, and the like.

The method for producing the anisotropic conductive material of the present invention is not particularly limited. For example, the conductive fine particles of the present invention are added to the binder resin, and the mixture is uniformly mixed and dispersed. Examples thereof include a method for producing an anisotropic conductive ink, an anisotropic conductive adhesive, and the like. Further, the conductive fine particles of the present invention are added to the binder resin and uniformly dispersed or dissolved by heating, and a predetermined film thickness is applied to a release treatment surface of a release material such as release paper or release film. For example, a method for producing an anisotropic conductive film, an anisotropic conductive sheet or the like by coating may be used.
Moreover, it is good also as an anisotropic conductive material by using separately the said binder resin and the electroconductive fine particles of this invention, without mixing.

A connection structure connected by the conductive fine particles of the present invention or the anisotropic conductive material of the present invention is also one aspect of the present invention.
The connection structure of the present invention is a connection structure in which a pair of circuit boards are electrically connected by filling the conductive fine particles of the present invention or the anisotropic conductive material of the present invention between a pair of circuit boards. is there.

ADVANTAGE OF THE INVENTION According to this invention, the electroconductive fine particles which can make highly reliable electrical connection can be provided. In addition, an anisotropic conductive material containing the conductive fine particles and a connection structure connected by the conductive fine particles or the anisotropic conductive material can be provided.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
(1) Preparation of resin fine particles 70 parts by weight of divinylbenzene, 30 parts by weight of trimethylolpropane trimethacrylate and 2 parts by weight of benzoyl peroxide were added to 800 parts by weight of an aqueous solution containing 3% by weight of polyvinyl alcohol, and the mixture was stirred. Under a nitrogen stream, the mixture was polymerized at 80 ° C. with stirring for 15 hours to obtain resin fine particles.
The obtained resin fine particles were washed with distilled water and methanol, and then classified. The average particle size of the resin fine particles was 4.1 μm, and the coefficient of variation was 5.0%.

10 g of the obtained resin fine particles were etched and washed with water. Resin fine particles adsorbed with palladium ions were added to a 0.5% by weight dimethylamine borane aqueous solution to obtain resin fine particles to which palladium was imparted.

(2) Formation of nickel layer 10 g of resin fine particles provided with palladium were dispersed in 1200 mL of ion-exchanged water, and 4 mL of a plating stabilizer was added to prepare a suspension A. Next, 120 mL of a mixed solution of 450 g / L of nickel sulfate, 150 g / L of sodium hypophosphite, 116 g / L of sodium citrate, and 6 mL of a plating stabilizer was adjusted to pH 8.5 with ammonia. Produced. The plating solution was added to the suspension A through a metering pump at an addition rate of 81 mL / min. Thereafter, stirring was performed until the pH of the aqueous solution was stabilized, and the previous plating step was performed until hydrogen foaming stopped. After the previous plating process was completed, the plating solution was filtered, and the particles were washed with distilled water and methanol. The washed particles were dispersed in 1200 mL of ion exchange water to prepare a suspension B.

Next, 650 mL of a mixed solution of 450 g / L of nickel sulfate, 150 g / L of sodium hypophosphite, 116 g / L of sodium citrate, and 35 mL of a plating stabilizer is adjusted to pH 9.5 with ammonia. Produced. Late plating solution was added to suspension B through a metering pump at an addition rate of 27 mL / min. Then, it stirred until pH was stabilized and the latter plating process was performed until hydrogen foaming stopped.
Next, the plating solution was filtered, and the particles were washed with distilled water and methanol and then dried with a vacuum dryer at 80 ° C. to obtain resin fine particles on which a nickel layer was formed.
In addition, the nickel content of the nickel layer was 97% by weight as measured by a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation). The thickness of the nickel layer was 0.1 μm.

(3) Addition of alkyl group 1 g of phosphoric acid monohexyl ester was dissolved in 99 g of a 50 wt% aqueous ethanol solution (water: ethanol = 50 wt%: 50 wt%). 10 g of resin fine particles formed with the nickel layer produced in Example 1 were added to an ethanol aqueous solution and stirred for 1 hour while keeping the temperature of the aqueous solution at 50 ° C. The aqueous ethanol solution was filtered, and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the nickel layer.
When analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that hexyl groups were formed on the surface of the conductive fine particles.

(Example 2)
Conductive fine particles were produced in the same manner as in Example 1 except that the monohexyl phosphate was changed to a monooctyl phosphate.

(Example 3)
Conductive fine particles were produced in the same manner as in Example 1 except that monohexyl phosphate was changed to monododecyl phosphate.

Example 4
Conductive fine particles were produced in the same manner as in Example 1 except that monohexyl phosphate was changed to monohexadecyl phosphate.

(Example 5)
In the formation of the nickel layer, the surface of the nickel layer has an alkyl group as in Example 1 except that the pH of the previous plating solution was changed to 8.0 and the pH of the latter plating solution was changed to 9.0. Conductive fine particles were produced.
In addition, the nickel content of the nickel layer was 96% by weight as measured by a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation). The thickness of the nickel layer was 0.1 μm.

(Example 6)
1 g of hexyl thiol was dissolved in 99 g of ethanol. 10 g of resin fine particles with a nickel layer formed in Example 1 were added to ethanol and stirred for 1 hour while maintaining the liquid temperature of ethanol at 50 ° C. Ethanol was filtered and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the nickel layer.
When analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that hexyl groups were formed on the surface of the conductive fine particles.

(Example 7)
Conductive fine particles were produced in the same manner as in Example 6 except that hexyl thiol was changed to octyl thiol.

(Example 8)
Conductive fine particles were produced in the same manner as in Example 6 except that hexylthiol was changed to dodecylthiol.

Example 9
Conductive fine particles were produced in the same manner as in Example 6 except that hexylthiol was changed to hexadecylthiol.

(Example 10)
1 g of di-n-hexyl disulfide was dissolved in 99 g of ethanol. 10 g of resin fine particles with a nickel layer formed in Example 1 were added to ethanol and stirred for 1 hour while maintaining the liquid temperature of ethanol at 50 ° C. Ethanol was filtered and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the nickel layer.
When analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that hexyl groups were formed on the surface of the conductive fine particles.

(Example 11)
Conductive fine particles were produced in the same manner as in Example 10 except that di-n-hexyl disulfide was changed to di-n-octyl disulfide.

Example 12
Conductive fine particles were produced in the same manner as in Example 10, except that di-n-hexyl disulfide was changed to di-n-dodecyl disulfide.

(Example 13)
1 g of hexyltriethoxysilane was dissolved in 99 g of a 95% by weight aqueous propanol solution (water: propanol = 5% by weight: 95% by weight). 10 g of resin fine particles with a nickel layer formed in Example 1 were added to a propanol aqueous solution and stirred for 1 hour while maintaining the temperature of the aqueous solution at 50 ° C. The aqueous propanol solution was filtered, and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the nickel layer.
When analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that hexyl groups were formed on the surface of the conductive fine particles.

(Example 14)
Conductive fine particles were produced in the same manner as in Example 13 except that hexyltriethoxysilane was changed to octyltriethoxysilane.

(Example 15)
Conductive fine particles were produced in the same manner as in Example 13 except that hexyltriethoxysilane was changed to dodecyltriethoxysilane.

(Comparative Example 1)
(1) Preparation of resin fine particles 70 parts by weight of divinylbenzene, 30 parts by weight of trimethylolpropane trimethacrylate and 2 parts by weight of benzoyl peroxide were added to 800 parts by weight of an aqueous solution containing 3% by weight of polyvinyl alcohol, and the mixture was stirred. Under a nitrogen stream, the mixture was polymerized at 80 ° C. with stirring for 15 hours to obtain resin fine particles.
The obtained resin fine particles were washed with distilled water and methanol, and then classified. The average particle size of the resin fine particles was 4.1 μm, and the coefficient of variation was 5.0%.

10 g of the obtained resin fine particles were etched and washed with water. Resin fine particles adsorbed with palladium ions were added to a 0.5% by weight dimethylamine borane aqueous solution to obtain resin fine particles to which palladium was imparted.

(2) Formation of nickel layer 10 g of resin fine particles provided with palladium were dispersed in 1200 mL of ion-exchanged water, and 4 mL of a plating stabilizer was added to prepare an aqueous solution. To this aqueous solution, 120 mL of a mixed solution of nickel sulfate 450 g / L, sodium hypophosphite 150 g / L, sodium citrate 116 g / L, and plating stabilizer 6 mL was added at a rate of 81 mL / min through a metering pump. . Thereafter, stirring was performed until the pH of the aqueous solution was stabilized, and the previous plating step was performed until hydrogen foaming stopped.

Next, 650 mL of a mixed solution of 450 g / L of nickel sulfate, 150 g / L of sodium hypophosphite, 116 g / L of sodium citrate, and 35 mL of a plating stabilizer was added to the aqueous solution after the previous plating step was 27 mL / min. It was added through a metering pump at an addition rate. Then, it stirred until pH was stabilized and the latter plating process was performed until hydrogen foaming stopped. Next, the plating solution was filtered, and the particles were washed with distilled water and methanol and then dried with a vacuum dryer at 80 ° C. to obtain resin fine particles on which a nickel layer was formed.
In addition, the nickel content of the nickel layer was 94% by weight as measured by a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation). The thickness of the nickel layer was 0.1 μm.

(Comparative Example 2)
Conductive fine particles were produced in the same manner as in Example 3 except that the resin fine particles formed with the nickel layer obtained in Comparative Example 1 were used.

(Comparative Example 3)
Conductive fine particles were produced in the same manner as in Example 1, except that the resin fine particles formed with the nickel layer obtained in Comparative Example 1 were used.

(Comparative Example 4)
1 g of phosphoric acid monobutyl ester was dissolved in 99 g of a 50 wt% ethanol aqueous solution (water: ethanol = 50 wt%: 50 wt%). 10 g of resin fine particles formed with the nickel layer produced in Example 1 were added to an ethanol aqueous solution and stirred for 1 hour while keeping the temperature of the aqueous solution at 50 ° C. The aqueous ethanol solution was filtered, and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the nickel layer.
When analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that a butyl group was formed on the surface of the conductive fine particles.

(Comparative Example 5)
The resin fine particles formed with the nickel layer obtained in Example 1 were used as conductive fine particles.

<Evaluation>
The following evaluation was performed about the electroconductive fine particles obtained in Examples 1-15 and Comparative Examples 1-5. The results are shown in Table 1.

(1) Measurement of surface contact angle to water The surface contact angle of conductive fine particles to water was measured using a fully automatic contact angle measuring device (“OCA35” manufactured by Data Physics Co., Ltd.). That is, 1 g of the obtained conductive fine particles were placed on a slide glass, the needle was brought close to the surface of the conductive fine particle, and 3 μL of pure water was attached to the surface of the conductive fine particle using the needle. An image obtained by photographing the conductive fine particles to which pure water adhered was analyzed, and the surface contact angle was measured.

(2) Measurement of volume resistivity The volume resistivity of the conductive fine particles was measured using a “powder resistivity measurement system” manufactured by Mitsubishi Chemical Corporation under a condition in which a load of 20 kN was applied to 2.5 g of the conductive fine particles. .

(3) Production of anisotropic conductive film 100 parts by weight of an epoxy resin (“Epicoat 828” manufactured by Yuka Shell Epoxy Co., Ltd.), 2 parts by weight of trisdimethylaminoethylphenol, and 100 parts by weight of toluene as a binder resin The mixture was sufficiently mixed using a stirrer to obtain a mixture. The obtained mixture was applied onto a release film so that the thickness after drying was 10 μm, and toluene was volatilized to obtain an adhesive film 1.
Next, conductive fine particles were added to 100 parts by weight of an epoxy resin (“Epicoat 828” manufactured by Yuka Shell Epoxy Co., Ltd.), 2 parts by weight of trisdimethylaminoethylphenol, and 100 parts by weight of toluene as a binder resin, and a planetary stirrer Was mixed well to obtain a mixture. The obtained mixture was applied onto a release film so that the thickness after drying was 7 μm, and toluene was volatilized to obtain an adhesive film 2 containing conductive fine particles. In addition, the content of the conductive fine particles in the adhesive film 2 was adjusted to be 50,000 / cm ² .
The obtained adhesive film 1 and adhesive film 2 were laminated at room temperature to obtain a 17 μm thick anisotropic conductive film having a two-layer structure.

(4) Preparation of connection structure The obtained anisotropic conductive film was cut into a size of 5 mm × 5 mm. At the center of the glass substrate on which the aluminum electrode (height 0.2 μm, L / S = 20 μm / 20 μm) having a resistance measurement lead wire formed on one side is formed on the cut anisotropic conductive film. Pasted. Next, the glass substrates on which the same aluminum electrodes were formed were bonded together after being aligned so that the electrodes overlap each other. The laminated body of the glass substrates was thermocompression bonded under pressure bonding conditions of 10N and 180 ° C. to obtain a connection structure.

(5) Measurement of connection resistance value The connection resistance value between the opposing electrodes of the obtained connection structure was measured by a four-terminal method. Moreover, the connection resistance value of the connection structure after a PCT test was measured similarly. The PCT test means an accelerated test in which the obtained connection structure is stored in a constant temperature and humidity chamber at 85 ° C. and a relative humidity of 85% for 100 hours.

(Example 16)
(1) Preparation of resin fine particles 70 parts by weight of divinylbenzene, 30 parts by weight of trimethylolpropane trimethacrylate and 2 parts by weight of benzoyl peroxide were added to 800 parts by weight of an aqueous solution containing 3% by weight of polyvinyl alcohol, and the mixture was stirred. Under a nitrogen stream, the mixture was polymerized at 80 ° C. with stirring for 15 hours to obtain resin fine particles.
The obtained resin fine particles were washed with distilled water and methanol, and then classified. The average particle size of the resin fine particles was 4.1 μm, and the coefficient of variation was 5.0%.

10 g of the obtained resin fine particles were etched and washed with water. Resin fine particles adsorbed with palladium ions were added to a 0.5% by weight dimethylamine borane aqueous solution to obtain resin fine particles to which palladium was imparted.

(2) Formation of nickel layer 10 g of resin fine particles provided with palladium were dispersed in 1200 mL of ion-exchanged water, and 4 mL of a plating stabilizer was added to prepare a suspension A. Next, 120 mL of a mixed solution of 450 g / L of nickel sulfate, 150 g / L of sodium hypophosphite, 116 g / L of sodium citrate, and 6 mL of a plating stabilizer was adjusted to pH 8.5 with ammonia. Produced. The plating solution was added to the suspension A through a metering pump at an addition rate of 81 mL / min. Thereafter, stirring was performed until the pH of the aqueous solution was stabilized, and the previous plating step was performed until hydrogen foaming stopped. After the previous plating process was completed, the plating solution was filtered, and the particles were washed with distilled water and methanol. The washed particles were dispersed in 1200 mL of ion exchange water to prepare a suspension B.

Next, 650 mL of a mixed solution of 450 g / L of nickel sulfate, 150 g / L of sodium hypophosphite, 116 g / L of sodium citrate, and 35 mL of a plating stabilizer is adjusted to pH 9.5 with ammonia. Produced. Late plating solution was added to suspension B through a metering pump at an addition rate of 27 mL / min. Then, it stirred until pH was stabilized and the latter plating process was performed until hydrogen foaming stopped.
Next, the plating solution was filtered, and the particles were washed with distilled water and methanol and then dried with a vacuum dryer at 80 ° C. to obtain resin fine particles on which a nickel layer was formed.
In addition, the nickel content of the nickel layer was 97% by weight as measured by a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation).

(3) Formation of cerium oxide layer 10 g of resin fine particles on which a nickel layer was formed were added to 1 L of a 1% by weight cerium sulfate aqueous solution and stirred for 1 hour while maintaining the liquid temperature of the aqueous solution at 50 ° C. The aqueous cerium sulfate solution was filtered, and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles on which a cerium oxide layer was formed.
In addition, when measured with an energy dispersive X-ray spectrometer, it was confirmed that a cerium oxide layer was formed on the surface of the nickel layer. Moreover, the thickness of the nickel layer of the obtained conductive fine particles was 0.1 μm, and the thickness of the cerium oxide layer was 0.005 μm.

(4) Giving alkyl group 1 g of phosphoric acid monododecyl ester was dissolved in 1 L of an aqueous tetrahydrofuran solution (water: tetrahydrofuran = 50 wt%: 50 wt%). 10 g of the obtained conductive fine particles were added to an aqueous tetrahydrofuran solution and stirred for 1 hour while keeping the temperature of the aqueous solution at 50 ° C. The aqueous tetrahydrofuran solution was filtered, and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the cerium oxide layer.
In addition, when analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that dodecyl groups were formed on the surface of the conductive fine particles.

(Example 17)
10 g of resin fine particles formed with a nickel layer obtained in the same manner as in Example 16 were added to 1 L of 1 wt% aqueous potassium potassium oxalate solution, and the mixture was stirred for 1 hour while maintaining the liquid temperature at 50 ° C. . After filtering the aqueous potassium potassium oxalate solution and washing the particles with distilled water, the particles were dried with a vacuum dryer at 80 ° C. to produce conductive fine particles on which a titanium oxide layer was formed.
In addition, when measured with the energy dispersive X-ray spectrometer, it was confirmed that a titanium oxide layer was formed on the surface of the nickel layer. Moreover, the thickness of the nickel layer of the obtained conductive fine particles was 0.1 μm, and the thickness of the titanium oxide layer was 0.005 μm.

1 g of phosphoric acid monododecyl ester was dissolved in 1 L of an aqueous tetrahydrofuran solution (water: tetrahydrofuran = 50% by weight: 50% by weight). 10 g of the obtained conductive fine particles were added to an aqueous tetrahydrofuran solution and stirred for 1 hour while keeping the temperature of the aqueous solution at 50 ° C. The aqueous tetrahydrofuran solution was filtered, and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the titanium oxide layer.
In addition, when analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that dodecyl groups were formed on the surface of the conductive fine particles.

(Example 18)
1 g of monohexyl phosphate was dissolved in 1 L of an aqueous tetrahydrofuran solution (water: tetrahydrofuran = 50% by weight: 50% by weight). 10 g of conductive fine particles obtained in the same manner as in Example 16 was added to an aqueous tetrahydrofuran solution and stirred for 1 hour while maintaining the liquid temperature of the aqueous solution at 50 ° C. The aqueous tetrahydrofuran solution was filtered, and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the cerium oxide layer.
When analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that hexyl groups were formed on the surface of the conductive fine particles.

(Example 19)
1 g of phosphoric acid monohexyl ester was dissolved in 1 L of an aqueous tetrahydrofuran solution (water: tetrahydrofuran = 50% by weight: 50% by weight). 10 g of conductive fine particles obtained in the same manner as in Example 17 was added to an aqueous tetrahydrofuran solution and stirred for 1 hour while maintaining the liquid temperature of the aqueous solution at 50 ° C. The aqueous tetrahydrofuran solution was filtered, and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the titanium oxide layer.
When analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that hexyl groups were formed on the surface of the conductive fine particles.

(Example 20)
1 g of phosphoric acid monohexadecyl ester was dissolved in 1 L of an aqueous tetrahydrofuran solution (water: tetrahydrofuran = 50 wt%: 50 wt%). 10 g of conductive fine particles obtained in the same manner as in Example 16 was added to an aqueous tetrahydrofuran solution and stirred for 1 hour while maintaining the liquid temperature of the aqueous solution at 50 ° C. The aqueous tetrahydrofuran solution was filtered, and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the cerium oxide layer.
When analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that hexadecyl groups were formed on the surface of the conductive fine particles.

(Example 21)
1 g of phosphoric acid monohexadecyl ester was dissolved in 1 L of an aqueous tetrahydrofuran solution (water: tetrahydrofuran = 50 wt%: 50 wt%). 10 g of conductive fine particles obtained in the same manner as in Example 17 was added to an aqueous tetrahydrofuran solution and stirred for 1 hour while maintaining the liquid temperature of the aqueous solution at 50 ° C. The aqueous tetrahydrofuran solution was filtered, and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the titanium oxide layer.
When analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that hexadecyl groups were formed on the surface of the conductive fine particles.

(Example 22)
In the formation of the nickel layer, conductive fine particles were prepared in the same manner as in Example 16 except that the pH of the first plating solution was changed to 8.0 and the pH of the latter plating solution was changed to 9.0.
In addition, the nickel content of the nickel layer was 96% by weight as measured by a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation). Moreover, the thickness of the nickel layer was 0.1 μm, and the thickness of the cerium oxide layer was 0.005 μm.

1 g of phosphoric acid monododecyl ester was dissolved in 1 L of an aqueous tetrahydrofuran solution (water: tetrahydrofuran = 50% by weight: 50% by weight). 10 g of the obtained conductive fine particles were added to an aqueous tetrahydrofuran solution and stirred for 1 hour while keeping the temperature of the aqueous solution at 50 ° C. The aqueous tetrahydrofuran solution was filtered, and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the cerium oxide layer.
In addition, when analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that dodecyl groups were formed on the surface of the conductive fine particles.

(Example 23)
In the formation of the nickel layer, conductive fine particles were prepared in the same manner as in Example 17 except that the pH of the first plating solution was changed to 8.0 and the pH of the latter plating solution was changed to 9.0.
In addition, the nickel content of the nickel layer was 96% by weight as measured by a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation). Moreover, the thickness of the nickel layer was 0.1 μm, and the thickness of the titanium oxide layer was 0.005 μm.

1 g of phosphoric acid monododecyl ester was dissolved in 1 L of an aqueous tetrahydrofuran solution (water: tetrahydrofuran = 50% by weight: 50% by weight). 10 g of the obtained conductive fine particles were added to an aqueous tetrahydrofuran solution and stirred for 1 hour while keeping the temperature of the aqueous solution at 50 ° C. The aqueous tetrahydrofuran solution was filtered, and the particles were washed with distilled water and then dried with a vacuum dryer at 80 ° C. to produce conductive fine particles having an alkyl group on the surface of the titanium oxide layer.
In addition, when analyzed by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), it was confirmed that dodecyl groups were formed on the surface of the conductive fine particles.

<Evaluation>
The conductive fine particles obtained in Examples 16 to 23 were evaluated in the same manner as in Example 1 and the like. The results are shown in Table 2.

ADVANTAGE OF THE INVENTION According to this invention, the electroconductive fine particles which can make highly reliable electrical connection can be provided. In addition, an anisotropic conductive material containing the conductive fine particles and a connection structure connected by the conductive fine particles or the anisotropic conductive material can be provided.

Claims (9)

Conductive fine particles in which a nickel layer is formed on the surface of the substrate fine particles,
The nickel content of the nickel layer is 96 wt% or more,
Conductive fine particles characterized by having a surface contact angle with water of 90 ° or more and a volume resistivity of 0.0030 Ω · cm or less. 2. The conductive fine particles according to claim 1, wherein a metal oxide layer containing cerium or titanium is formed on the surface of the nickel layer. The conductive fine particles according to claim 1, wherein a compound having an alkyl group having 6 to 22 carbon atoms is bonded to the surface of the nickel layer. The conductive fine particles according to claim 2, wherein a compound having an alkyl group having 6 to 22 carbon atoms is bonded to the surface of the metal oxide layer. The compound having an alkyl group having 6 to 22 carbon atoms is a phosphate ester or a salt thereof having an alkyl group having 6 to 22 carbon atoms, an alkoxysilane having an alkyl group having 6 to 22 carbon atoms, or 6 carbon atoms. 5. The conductive fine particle according to claim 3, wherein the conductive fine particle is at least one selected from the group consisting of an alkylthiol having an alkyl group of ˜22 and a dialkyl disulfide having an alkyl group having 6 to 22 carbon atoms. . The conductive fine particles according to claim 3 or 4, wherein the compound having an alkyl group having 6 to 22 carbon atoms is a phosphate ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof. An anisotropic conductive material comprising the conductive fine particles according to claim 1, 2, 3, or 4 and a binder resin. A connection structure, wherein the connection structure is connected using the conductive fine particles according to claim 1. A connection structure which is connected using the anisotropic conductive material according to claim 7.