JP5271019B2 - Conductive fine particles, anisotropic conductive material, and connection structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive particulate with highly reliable electrical connectivity, as well as an anisotropic conductive material containing the conductive particulate, and to provide a connection structure connected with either the conductive particulate or the anisotropic conductive material. <P>SOLUTION: Of the conductive particulate with a metal layer containing nickel and a conductive layer containing gold or palladium sequentially laminated, the conductive layer has a thickness of 10 nm or less, and has alkyl groups with the carbon number of 6 to 22 on the surface. <P>COPYRIGHT: (C)2010,JPO&amp;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.

Palladium is known as a metal having excellent conductivity. Although it has been studied to provide a palladium plating layer instead of the gold plating layer, since palladium is a relatively soft metal, there is a problem similar to that of the gold plating layer.

Thus, conductive fine particles having a conductive layer formed of a metal harder than gold or palladium 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 in which a metal layer containing nickel and a conductive layer containing gold or palladium are sequentially laminated on the surface of the substrate fine particle, and the thickness of the conductive layer is 10 nm or less And conductive fine particles having an alkyl group having 6 to 22 carbon atoms on the surface.
The present invention is described in detail below.

In order to solve the problem that the insulating binder resin remains between the conductive fine particles and the electrode, or the oxide film formed on the surface of the electrode cannot be broken, Conductive fine particles were produced by forming a nickel-containing metal layer on the surface of the material fine particles and further laminating a conductive layer made of gold or palladium on the surface of the metal layer with a thickness of 10 nm or less. When the thickness of the conductive layer made of gold or palladium is 10 nm or less, the surface hardness of the substantially conductive fine particles becomes the same as that of the metal layer made of hard nickel, and there is a problem caused by the softness of gold or palladium. Can be resolved.
However, such conductive fine particles have a problem in terms of reliability of electrical connection. If the thickness of the conductive layer is set to 10 nm or less, uniform coating becomes difficult, and a part of the metal layer containing nickel is exposed without being covered with the conductive layer. Further, even when the conductive layer is peeled off by impact or the like, a part of the metal layer containing nickel is exposed. It was thought that the reliability of the electrical connection was lowered because the exposed metal layer was oxidized.
The present inventor has found that the reliability of electrical connection is remarkably improved by introducing an alkyl group having 6 to 22 carbon atoms into the surface of such conductive fine particles, thus completing the present invention.

In the conductive fine particles of the present invention, a metal layer containing nickel and a conductive layer containing gold or palladium are sequentially laminated on the surface of the substrate 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.

The preferable lower limit of the 10% K value of the resin fine particles is 1000 MPa, and the preferable upper limit is 15000 MPa. If the 10% K value is less than 1000 MPa, the resin fine particles may be destroyed when the resin fine particles are compressed and deformed. When the 10% K value exceeds 15000 MPa, the conductive fine particles may damage the electrode. The more preferable lower limit of the 10% K value is 2000 MPa, and the more preferable upper limit is 10,000 MPa.

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 diameter of the base material particles is less than 0.5 μm, the base material particles are likely to aggregate. May cause short circuit. When the average particle diameter of the substrate fine particles exceeds 100 μm, the metal layer and the conductive layer are easily 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 conductive fine particles of the present invention have a metal layer containing nickel on the surface of the above-mentioned substrate fine particles.
The metal layer may be directly formed on the surface of the substrate fine particles. In the metal layer, a base metal layer may be formed between the metal layer and the base particle.
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.

The nickel content of the metal layer is preferably 96% by weight or more. When the nickel content is 96% by weight or more, even if a part of the metal layer is exposed, it is difficult to be oxidized, and the reliability of electrical connection is improved. 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 metal layer means the ratio of nickel which occupies for the sum total of the element contained in a metal layer.
The nickel content of the metal 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 metal 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.

Although the thickness of the said metal 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 metal layer is less than 0.005 μm, the connection resistance value of the conductive fine particles may increase. When the thickness of the metal layer exceeds 3 μm, the flexibility of the conductive fine particles may be impaired. A more preferable lower limit of the thickness of the metal layer is 0.08 μm, and a more preferable upper limit is 0.3 μm.
The thickness of the metal layer is a thickness obtained by observing and measuring a cross section of 10 randomly selected conductive fine particles with a scanning electron microscope (SEM) and arithmetically averaging the measured values.

In the conductive fine particles of the present invention, a conductive layer containing gold or palladium is laminated on the metal layer containing nickel.

The upper limit of the thickness of the conductive layer is 10 nm. If the thickness of the conductive layer exceeds 10 nm, the surface hardness of the conductive fine particles becomes insufficient, and an insulating binder resin remains between the conductive fine particles and the electrode, or on the surface of the electrode. The formed oxide film cannot be broken through. A preferable upper limit of the thickness of the conductive layer is 7 nm. A preferable lower limit of the thickness of the conductive layer is 3 nm. If the thickness of the conductive layer is less than 3 nm, the effect of providing the conductive layer may not be obtained. Further, it is technically difficult to make the thickness of the conductive layer less than 3 nm.
In addition, the thickness of the said metal layer means the average value of the maximum thickness when the cross section of ten electroconductive fine particles selected at random is observed and measured with a scanning electron microscope (SEM).

The conductive layer preferably covers the entire metal layer, but a part of the metal layer may be exposed without being covered with the conductive layer. Even if a part of the metal layer is exposed, the oxidation can be suppressed by introducing an alkyl group having 6 to 22 carbon atoms on the surface.

The conductive fine particles of the present invention have an alkyl group having 6 to 22 carbon atoms on the surface. By having an alkyl group having 6 to 22 carbon atoms, the surface of the conductive fine particles becomes hydrophobic. Therefore, even if the metal layer containing nickel is exposed, the metal layer is hardly corroded, and the connection resistance value of the conductive fine particles is prevented from increasing.
The surface includes both a conductive layer containing gold or palladium which is the outermost surface layer and a metal layer containing nickel exposed without being covered with the conductive layer.

The lower limit of the carbon number of the alkyl group is 6 and the upper limit is 22. If the alkyl group has less than 6 carbon atoms, the surface cannot be made hydrophobic. When the carbon number of the alkyl group exceeds 22, the connection resistance value of the conductive fine particles may be increased. 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.

The method for imparting the alkyl group is not particularly limited, but the method of reacting the surface of the conductive fine particles with a phosphate ester having an alkyl group, the method of coating the surface of the conductive fine particles with an alkoxysilane having an alkyl group, and conductivity Examples thereof include a method of reacting alkylthiol on the surface of the fine particles, a method of reacting dialkyl disulfide on the surface of the conductive fine particles, and the like.

The phosphate ester is not particularly limited as long as it is a phosphate ester or phosphate monosodium salt having an alkyl group. For example, phosphate monohexyl ester, phosphate monoheptyl ester, phosphate monooctyl ester, phosphate Monononyl ester, phosphate monodecyl ester, phosphate monoundecyl ester, phosphate monododecyl ester, phosphate monotridecyl ester, phosphate monotetradecyl ester, phosphate monopentadecyl ester, phosphate monohexyl ester mono Sodium salt, monoheptyl phosphate monosodium salt, monooctyl phosphate monosodium salt, monononyl phosphate monosodium salt, monodecyl phosphate monosodium salt, monoundecyl phosphate mononatriate Unsalted, phosphoric acid monododecyl ester monosodium salt, monocalcium phosphate tridecyl ester monosodium salt, phosphate acid mono tetradecyl ester monosodium salt, monocalcium phosphate pentadecyl ester monosodium salt.

The method for reacting the phosphoric acid ester having an alkyl group on the surface of the conductive fine particles is not particularly limited. For example, the method is a method in which the substrate fine particles on which the metal layer and the conductive layer are formed are attached to an aqueous phosphate ester solution. Etc. By attaching the substrate fine particles formed with the metal layer and the conductive layer to the phosphate ester aqueous solution, nickel, gold, palladium on the surface reacts with the phosphate ester, and an alkyl group is formed on the surface. Is granted.
The concentration of the phosphate ester in the aqueous phosphate ester solution 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.

The alkoxysilane is not particularly limited as long as it is an alkoxysilane having an alkyl group. For example, hexyltrimethoxysilane, hexyltriethoxysilane, heptyltrimethoxysilane, heptyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, Nonyltrimethoxysilane, nonyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, undecyltrimethoxysilane, undecyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, tridecyltrimethoxysilane, tridecyl Triethoxysilane, tetradecyltrimethoxysilane, tetradecyltriethoxysilane, pentadecyltrimethoxysilane, pentadecyltriethoxysilane And the like.

The method of coating the surface of the conductive fine particles with an alkoxysilane having an alkyl group is not particularly limited, and examples thereof include a method of attaching the substrate fine particles on which the metal layer and the conductive layer are formed to an alkoxysilane aqueous solution. It is done. By attaching the substrate fine particles on which the metal layer and the conductive layer are formed to the alkoxysilane aqueous solution, the surface is coated with the alkoxysilane and an alkyl group is imparted.
The concentration of alkoxysilane in the aqueous alkoxysilane 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 said alkoxysilane aqueous solution may contain organic solvents, such as alcohol, such as methanol, ethanol, and propanol.

Although the alkylthiol is not particularly limited, for example, hexylthiol, heptylthiol, octylthiol, nonylthiol, decylthiol, undecylthiol, dodecylthiol, tridecylthiol, tetradecylthiol, pentadecylthiol, hexadecylthiol, etc. Can be mentioned. The alkyl thiol preferably has a thiol group at the end of the alkyl chain.

The method for reacting the alkyl thiol on the surface of the conductive fine particles is not particularly limited, and examples thereof include a method of attaching the substrate fine particles on which the metal layer and the conductive layer are formed to a solution in which the alkyl thiol is dissolved. It is done. By attaching the substrate fine particles on which the metal layer and the conductive layer are formed to a solution in which the alkylthiol is dissolved, nickel, gold, palladium on the surface reacts with the alkylthiol, An alkyl group is provided.
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 alkyl thiol is dissolved is not particularly limited as long as the alkyl thiol is dissolved, and may contain an organic solvent such as alcohol such as methanol, ethanol, and propanol.

The dialkyl disulfide is not particularly limited. And dihexadecyl disulfide.

A method of reacting the dialkyl disulfide on the surface of the conductive fine particles is not particularly limited, and examples thereof include a method of attaching the substrate fine particles on which the metal layer and the conductive layer are formed to a solution in which the dialkyl disulfide is dissolved. It is done. By attaching the substrate fine particles on which the metal layer and the conductive layer are formed to a solution in which the dialkyl disulfide is dissolved, nickel, gold, palladium on the surface reacts with the dialkyl disulfide, and the surface is exposed to the surface. An alkyl group is provided.
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.

As a method for imparting the alkyl group, a method of reacting a phosphate ester having an alkyl group on the surface of the conductive fine particles, a method of reacting an alkyl thiol on the surface of the conductive fine particles, and a surface of the conductive fine particles A method of reacting a dialkyl disulfide is preferable, a method of reacting a phosphate ester having an alkyl group on the surface of the conductive fine particles, and a method of reacting an alkylthiol on the surface of the conductive fine particles are more preferable. A method of reacting a phosphate ester having an alkyl group on the surface thereof is more preferable.

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

First, a metal layer containing nickel is formed on the surface of the substrate fine particles. A method for forming a nickel-containing metal layer on the surface of the substrate fine particles is not particularly limited, and examples thereof include an electrolytic plating method and an electroless plating method.
When a metal layer containing nickel is formed on the surface of the substrate fine particles using the electrolytic plating method, a metal layer having a high nickel content can be formed. However, when the metal 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 metal layer containing nickel is formed on the surface of the substrate fine particles using the conventional electroless plating method, phosphorus, boron, etc. derived from the reducing agent contained in the electroless plating bath are included in the metal layer. There were times when it was. If phosphorus or boron is contained in the metal 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 phosphorus, boron, etc. derived from a reducing agent are contained in the metal layer, the nickel content of the metal layer may be lowered. Further, in such an electroless plating method, it is difficult to increase the nickel content of the metal layer even if the pH of the suspension or the liquid temperature is adjusted.
Therefore, in the present invention, in order to form a metal 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 metal 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 metal 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 metal 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 metal layer can be reduced.

Next, a conductive layer containing gold or palladium is formed on the surface of the substrate fine particles on which the metal layer is formed. The method for forming the conductive layer is not particularly limited, and examples thereof include an electrolytic plating method and an electroless plating method.

Examples of the method of setting the thickness of the conductive layer to 10 nm or less include a method of adjusting the content of gold salt or palladium salt contained in the electroless plating solution, a method of adjusting the time for performing electroless plating, and the like. It is done.

Finally, the conductive fine particles of the present invention are obtained by introducing an alkyl group having 6 to 22 carbon atoms into the surface of the base fine particles on which the metal layer and the conductive layer are sequentially laminated by the above-described method.

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 perform electrical connection with high reliability can be provided. Further, according to the present invention, it is possible 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.

Hereinafter, 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 To 800 parts by weight of an aqueous solution containing 3% by weight of polyvinyl alcohol, 70 parts by weight of divinylbenzene, 30 parts by weight of trimethylolpropane trimethacrylate and 2 parts by weight of benzoyl peroxide are added, and the mixture is stirred. did. 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 metal 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 metal layer containing nickel was formed.
In addition, the nickel content of the metal layer was 97% by weight as measured by a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation). The thickness of the metal layer was 0.1 μm.

(3) Formation of conductive layer Next, 10 g of resin fine particles having a metal layer formed thereon were added to 1000 mL of ion-exchanged water containing 3 g of sodium gold chloride to prepare an aqueous suspension.
To the obtained aqueous suspension, 20 g of mercaptosuccinic acid as a complexing agent, 0.5 g of 2-aminopyridine, 3 g of thiourea as a reducing agent, and 40 g of ammonium hydrogenphosphate as a buffering agent are added. An electrolytic gold plating solution was prepared.
After further adding 10 g of hydroxylamine to the gold plating solution, the pH was adjusted to 10 using ammonia. Next, the temperature of the plating solution was raised to 60 ° C. and stirred for 20 minutes to obtain resin fine particles having a conductive layer containing gold on the surface.
In addition, 50 resin fine particles on which the conductive layer was formed were observed with an electron microscope, the maximum thickness of the conductive layer was measured, and the average value of the maximum thickness of the conductive layer was calculated. The average value of the maximum thickness of the conductive layer was 10 nm. Moreover, some metal layers were not completely covered with the conductive layer.

(4) Introduction of 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 resin fine particles on which a conductive layer was formed 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 a dodecyl group (carbon number 12) on the surface.
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 2)
Conductive fine particles were produced in the same manner as in Example 1, except that monododecyl phosphate was changed to octyl phosphate (alkyl: carbon number 8) ester.

(Example 3)
Conductive fine particles were produced in the same manner as in Example 1, except that monododecyl phosphate was changed to hexyl phosphate (alkyl: carbon number 6) ester.

Example 4
Conductive fine particles were prepared in the same manner as in Example 1 except that the condition of the gold plating solution was 2.4 g of sodium gold chloride. The average value of the maximum thickness of the conductive layer was 7 nm.

(Example 5)
Conductive fine particles were produced in the same manner as in Example 2 except that the condition of the gold plating solution was 2.4 g of sodium gold chloride. The average value of the maximum thickness of the conductive layer was 7 nm.

(Example 6)
Conductive fine particles were prepared in the same manner as in Example 3 except that the condition of the gold plating solution was 2.4 g of sodium gold chloride. The average value of the maximum thickness of the conductive layer was 7 nm.

(Example 7)
10 g of resin fine particles formed with the metal layer produced in the example were added to 500 mL of ion-exchanged water and sufficiently dispersed by an ultrasonic treatment machine to obtain a particle suspension. While stirring this suspension at 50 ° C., 0.003 mol / L of palladium sulfate, 0.04 mol / L of ethylenediamine as a complexing agent, 0.06 mol / L of sodium formate as a reducing agent, and pH 10.0 containing a crystal modifier. The electroless plating solution was gradually added to perform electroless palladium plating. Next, by washing and vacuum drying, resin fine particles in which a conductive layer containing palladium was formed on the surface of the metal layer were obtained. The average value of the maximum thickness of the conductive layer was 10 nm.
Conductive fine particles were obtained in the same manner as in Example 1 except that the resin fine particles on which the obtained conductive layer containing palladium was formed were used.

(Example 8)
Conductive fine particles were produced in the same manner as in Example 7 except that the monododecyl phosphate was changed to octyl phosphate (alkyl: carbon number 8) ester.

Example 9
Conductive fine particles were produced in the same manner as in Example 1, except that monododecyl phosphate was changed to hexyl phosphate (alkyl: carbon number 6) ester.

(Example 10)
Conductive fine particles were produced in the same manner as in Example 7 except that the concentration of palladium sulfate was 0.002 mol / L under the conditions of the palladium plating solution. The average value of the maximum thickness of the conductive layer was 7 nm.

(Example 11)
Conductive fine particles were produced in the same manner as in Example 8 except that the concentration of palladium sulfate was 0.002 mol / L under the conditions of the palladium plating solution. The average value of the maximum thickness of the conductive layer was 7 nm.

(Example 12)
Conductive fine particles were produced in the same manner as in Example 9 except that the concentration of palladium sulfate was 0.002 mol / L under the conditions of the palladium plating solution. The average value of the maximum thickness of the conductive layer was 7 nm.

(Example 13)
Conductive fine particles were prepared in the same manner as in Example 1 except that monohexododecyl phosphate (alkyl: carbon number 16) ester was used instead of monododecyl phosphate.

(Example 14)
Conductive fine particles were produced in the same manner as in Example 7 except that monohexodecyl phosphate (alkyl: carbon number 16) ester was used instead of monododecyl phosphate.

(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 metal 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 conductive fine particles.
In addition, when measured with a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation), the nickel content of the metal layer was 94% by weight. The thickness of the metal layer was 0.1 μm.

(Comparative Example 2)
Conductive fine particles were prepared in the same manner as in Example 1 except that the condition of the gold plating solution was 6 g of sodium gold chloride and no alkyl group was formed. The average value of the maximum thickness of the conductive layer was 20 nm.

(Comparative Example 3)
Conductive fine particles were produced in the same manner as in Example 7, except that the concentration of palladium sulfate was 0.005 mol / L under the conditions of the palladium plating solution, and no alkyl group was formed. The average value of the maximum thickness of the conductive layer was 20 nm.

(Comparative Example 4)
Conductive fine particles were produced in the same manner as in Example 1 except that no alkyl group was introduced.

(Comparative Example 5)
Conductive fine particles were produced in the same manner as in Example 7 except that no alkyl group was introduced.

(Comparative Example 6)
Conductive fine particles were produced in the same manner as in Example 1 except that monododecyl phosphate was changed to butyl phosphate (alkyl: carbon number 4) ester.

(Comparative Example 7)
Conductive fine particles were produced in the same manner as in Example 7 except that monododecyl phosphate was changed to butyl phosphate (alkyl: carbon number 4) ester.

<Evaluation>
The following evaluation was performed about the electroconductive fine particles obtained in Examples 1-14 and Comparative Examples 1-7. The results are shown in Table 1.

(1) 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.

(2) 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.

(3) 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.

ADVANTAGE OF THE INVENTION According to this invention, the electroconductive fine particles which can perform electrical connection with high reliability can be provided. Further, according to the present invention, it is possible 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.

Claims (6)

Conductive fine particles in which a metal layer containing nickel and a conductive layer containing gold or palladium are sequentially laminated on the surface of the substrate fine particles,
Conductive fine particles, wherein the conductive layer has a thickness of 10 nm or less and has an alkyl group having 6 to 22 carbon atoms on the surface. The conductive fine particle according to claim 1, wherein the thickness of the conductive layer is 7 nm or less. 3. The conductive fine particle according to claim 1, wherein a part of the metal layer is exposed without being covered with the conductive layer. 4. The conductive fine particles according to claim 1, 2, or 3, wherein the substrate fine particles are resin fine particles. An anisotropic conductive material comprising the conductive fine particles according to claim 1, 2, 3, or 4 and a binder resin. A connection structure comprising the conductive fine particles according to claim 1, or the anisotropic conductive material according to claim 5.