JP2007207665A - Manufacturing method of conductive particle, conductive particle and anisotropic conductive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a conductive particle capable of preventing a conduction failure, and of reducing a resistance value; to provide a conductive particle; and to provide an anisotropic conductive material. <P>SOLUTION: This manufacturing method of this conductive particle 1 having projections 2 on the surface thereof comprises: a process 1 for forming a nickel-plated layer with positive or negative charge charged thereon on the surface of a core particle; a process 2 for attaching a chelate agent having a functional group A and a reactive functional group B in every molecule to the surface of the nickel-plated layer through the functional group A; a process 3 for binding a resin fine particle or inorganic fine particle with charge opposite to the charge charged on the nickel-plated layer charged thereon to the surface of the nickel-plated layer through the reactive functional group B of the chelate agent; and a process 4 for coating the resin fine particle or inorganic fine particle and the nickel-plated layer with metal plating by an electrodeless plating method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for producing conductive particles capable of preventing conduction failure and reducing the resistance value, conductive particles, and an anisotropic conductive material.

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

These anisotropic conductive materials are used to electrically connect circuit boards to each other, for example, in electronic devices such as liquid crystal displays, personal computers, and mobile phones, and to electrically connect small components such as semiconductor elements to the circuit board. For this reason, it is used by being sandwiched between circuit boards and electrode terminals facing each other.

As conductive particles used in such anisotropic conductive materials, conventionally, a metal plating layer is formed as a conductive layer on the surface of non-conductive particles such as resin particles having a uniform particle size and appropriate strength. Conductive particles are used. However, when the circuit boards are electrically connected using such an anisotropic conductive material, a binder resin or the like is sandwiched between the conductive layer on the surface of the conductive particles and the circuit board, and the conductive particles and the circuit board. In some cases, the connection resistance between them and the like increases. In particular, with rapid progress and development of electronic devices in recent years, there has been a demand for further reduction in connection resistance between conductive particles and circuit boards.

For the purpose of reducing connection resistance, conductive particles having protrusions on the surface are disclosed (for example, see Patent Document 1). This conductive particle ensures that the protrusion and the circuit board are connected by the protrusion breaking through the binder resin or the like existing between the conductive layer on the surface of the conductive particle and the circuit board (resin eliminability). Thus, the connection resistance between the conductive particles and the circuit board is reduced.

However, since these protrusions are formed by abnormal deposition of the conductive layer on the surface of the conductive particles, it is difficult to control the position, height, etc. of the protrusions. When such conductive particles are sandwiched and pressure-bonded, depending on the position of the protrusion, the circuit board and the protrusion may not come into contact with each other, and it cannot be said that the connection resistance is sufficiently reduced.
JP 2000-243132 A

An object of this invention is to provide the manufacturing method of electroconductive particle, electroconductive particle, and anisotropic conductive material which can reduce a resistance value while preventing a conduction defect in view of the said present condition.

The present invention is a method for producing conductive particles having protrusions on the surface, the step 1 of forming a nickel plating layer charged with positive or negative charges on the surface of the core particles, the surface of the nickel plating layer A step 2 of attaching a chelating agent having a functional group A and a reactive functional group B in one molecule via the functional group A; and the reactive functional group B of the chelating agent on the surface of the nickel plating layer. A step 3 for bonding resin fine particles or inorganic fine particles charged with a charge opposite to the charge charged on the nickel plating layer, and the resin fine particles or inorganic fine particles and the nickel plating layer by an electroless plating method. It is a manufacturing method of the electroconductive particle which has the process 4 which coat | covers with metal plating.
The present invention is described in detail below.

As a result of intensive studies, the inventors of the present invention electrostatically agglomerate fine particles that become protrusions near the surface of the core particle, and attach the fine particles that become protrusions to the surface of the core particle by chemical bonding. The inventors have found that conductive particles having protrusions that are substantially uniform in height, position, etc. can be produced, and the present invention has been completed.

The manufacturing method of the electroconductive particle of this invention has the process 1 which forms the nickel plating layer which charged the positive or negative electric charge on the surface of a core particle.

The core particle is not particularly limited, and may be an inorganic material or an organic material as long as it has an appropriate elastic modulus, elastic deformability, and restoration property. Especially, since it is excellent in elastic deformability and a restoring property, it is preferable that it is the resin particle which uses resin. Moreover, nickel metal particles can also be used, and in this case, a step of forming a nickel layer described later can be omitted.

The resin constituting the resin particles is not particularly limited, for example, polyolefins such as polyethylene, polypropylene, polystyrene, polyisobutylene and polybutadiene, acrylic resins such as polymethyl methacrylate and polymethyl acrylate, polyalkylene terephthalate, polysulfone, polycarbonate, Polyamide, phenol resin such as phenol formaldehyde resin, melamine resin such as melamine formaldehyde resin, benzoguanamine resin such as benzoguanamine formaldehyde resin, urea formaldehyde resin, epoxy resin, (un) saturated polyester resin, polyethylene terephthalate, polysulfone, polyphenylene oxide, polyacetal, Polyimide, polyamideimide, polyetheretherketone, poly Those composed of Terusuruhon the like. Especially, what uses the resin formed by superposing | polymerizing 1 type, or 2 or more types of various polymerizable monomers which have an ethylenically unsaturated group is preferable from being easy to obtain suitable hardness.

The polymerizable monomer having an ethylenically unsaturated group may be a non-crosslinkable monomer or a crosslinkable monomer.
The non-crosslinkable monomer is not particularly limited, and examples thereof include styrene monomers such as styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene, chloromethylstyrene; (meth) acrylic acid Carboxyl group-containing monomers such as maleic acid and maleic anhydride; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl ( (Meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, ethylene glycol (meth) acrylate, trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate Alkyl (meth) acrylates such as relate; oxygen atom-containing (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, polyoxyethylene (meth) acrylate, glycidyl (meth) acrylate; Nitrile-containing monomers such as (meth) acrylonitrile; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether; vinyl acetate, vinyl butyrate, vinyl laurate, vinyl stearate, vinyl fluoride, vinyl chloride, vinyl propionate, etc. Acid vinyl esters; unsaturated hydrocarbons such as ethylene, propylene, butylene, methylpentene, isoprene and butadiene.

The crosslinkable monomer is not particularly limited. For example, tetramethylolmethane tetra (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane di (meth) acrylate, trimethylolpropane tri (meth) Acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, glycerol tri (meth) acrylate; glycerol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, etc. Polyfunctional (meth) acrylates; triallyl (iso) cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallylacrylamide, dia Silane-containing monomers such as γ- (meth) acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, vinyltrimethoxysilane; dicarboxylic acids such as phthalic acid; diamines; diallyl phthalate, benzoguanamine, triallyl isocyanate Etc.

Although it does not specifically limit as an average particle diameter of the said core particle, A preferable minimum is 1 micrometer and a preferable upper limit is 100 micrometers. If it is less than 1 μm, for example, it is likely to aggregate when electroless plating is performed, and it may be difficult to form single particles, and if it exceeds 100 μm, it may exceed the range used for circuit boards and the like as anisotropic conductive materials. is there.
In addition, the average particle diameter of the said core particle shall measure the particle diameter about 50 core particles chosen at random, and shall mean these arithmetically.

A method for forming a nickel plating layer charged with positive or negative charges on the surface of the core particles is not particularly limited. For example, a high concentration nickel plating solution is added to electrolessly plate the surface of the core particles. And the like.

The method for producing conductive particles of the present invention comprises the step 2 of attaching a chelating agent having a functional group A and a reactive functional group B in one molecule to the surface of the nickel plating layer via the functional group A. Have.

The functional group A is not particularly limited as long as it is a functional group capable of ionic bond, covalent bond, and coordinate bond with the nickel plating layer. For example, silane group, silanol group, carboxyl group, amino group, ammonium group Nitro group, hydroxyl group, carbonyl group, thiol group, sulfonic acid group, sulfonium group, boric acid group, oxazoline group, pyrrolidone group, phosphoric acid group, nitrile group and the like. Of these, a functional group capable of coordination bonding is preferable, and a functional group having S, N, and P atoms is preferably used.

The reactive functional group B is not particularly limited as long as it is a functional group capable of reacting with resin fine particles or inorganic fine particles described later. For example, a hydroxyl group, a carboxyl group, an amino group, an epoxy group, a silyl group, a silanol group, An isocyanate group etc. are mentioned.

The chelating agent having the functional group A and the reactive functional group B in one molecule is not particularly limited, and examples thereof include 2-aminoethanethiol, p-aminothiophenol, 4,4-diaminodiphenyl disulfide and the like. It is done. Moreover, the polysulfide etc. which have a functional group which can react with a resin fine particle or an inorganic fine particle are mentioned, Specifically, the trisulfide etc. which have an amino group are mentioned, for example.

Since the thiol group or sulfide group coordinates to nickel in the chelating agent, the chelating agent adheres to the surface of the nickel plating layer via the functional group A.
Thereby, the resin fine particles or inorganic fine particles described later can be electrostatically aggregated on the surface of the nickel-plated resin fine particles, and the resin fine particles or inorganic fine particles and the reactive functional groups B described later react efficiently, and are uniform. Protrusions can be formed.

In the method for producing conductive particles of the present invention, the surface of the nickel plating layer is charged with a charge opposite to the charge charged on the nickel plating layer via the reactive functional group B of the chelating agent. A step 3 of bonding resin fine particles or inorganic fine particles;

In the method for producing conductive particles of the present invention, the resin fine particles or the inorganic fine particles are charged to the nickel plated layer by using resin fine particles or inorganic fine particles charged with a charge opposite to the charge charged on the nickel plated layer. Since the resin fine particles or inorganic fine particles have the same electric charge, the resin fine particles or inorganic fine particles repel each other, so that the resin through the reactive functional group B Since fine particles or inorganic fine particles adhere to the nickel plating layer almost uniformly, the obtained conductive particles become conductive particles having substantially uniform protrusions.

The resin fine particles are not particularly limited, and examples thereof include negatively charged acrylic resin fine particles, styrene resin fine particles, divinylbenzene resin fine particles, positively charged amide resin fine particles, and polyacrylamide fine particles.

The size of the resin fine particles or the inorganic fine particles is not particularly limited, but a preferred lower limit is 30 nm and a preferred upper limit is 600 nm. If the thickness is less than 30 nm, the strength of the projection portion is remarkably inferior, and the projection may be damaged when the conductive particles of the present invention are kneaded with a binder resin or the like. The protrusion may not collapse when a substrate or the like is crimped.

The reactive functional group B of the chelating agent reacts with the functional group present on the surface of the resin fine particles or inorganic fine particles to form a bond, and therefore adheres to the surface of the nickel plating layer.
In addition, when it is desired to promote the reaction, it is preferable to heat the reaction solution.

The manufacturing method of the electroconductive particle of this invention has the process 4 which coat | covers the said resin fine particle or inorganic fine particle, and the said nickel plating layer with a metal plating by the electroless-plating method.

It does not specifically limit as a metal to coat | cover, For example, nickel, zinc, iron, lead, tin, aluminum, cobalt, indium, chromium, titanium, antimony, bismuth, germanium, cadmium etc. are mentioned.

The method for coating with the metal plating is not particularly limited, and examples thereof include an electroless plating method.

Although it does not specifically limit as thickness of the said metal plating, A preferable minimum is 0.02 micrometer and a preferable upper limit is 5 micrometers. If the thickness is less than 0.02 μm, the conductive particles may not be able to obtain conductivity. If the thickness exceeds 5 μm, the conductive particles become too hard and the conductive particles are deformed following the distance between the electrode terminals. It may be difficult.

The thickness of the conductive metal layer can be measured, for example, by observing the cross section of the conductive particles of the present invention with a transmission electron microscope (TEM). The magnification is not particularly limited, and a magnification that is easy to observe may be selected. For example, 50,000 times is used.

It is preferable that the manufacturing method of the electroconductive particle of this invention has the process 5 which forms a gold plating layer further on the surface of the said metal plating layer in addition to the process mentioned above.

By forming a gold layer on the outermost surface of the conductive particles of the present invention, it is possible to prevent oxidation of the metal plating layer, reduce connection resistance, stabilize the surface, and the like.

The method for forming the gold layer is not particularly limited, and examples thereof include conventionally known methods such as electroless plating, displacement plating, electroplating, reduction plating, and sputtering.

Although it does not specifically limit as thickness of the said gold layer, A preferable minimum is 1 nm and a preferable upper limit is 100 nm. If the thickness is less than 1 nm, it may be difficult to prevent oxidation of the metal plating layer, and the connection resistance value may increase. If the thickness exceeds 100 nm, the gold layer erodes the metal plating layer, and the core particles And the metal plating layer may deteriorate the adhesion.

The conductive particles manufactured by the above-described method for manufacturing conductive particles of the present invention are conductive particles having uniform protrusions on the surface.
Conductive particles produced by the method for producing conductive particles of the present invention, where τ is 10% or less, where τ is the coefficient of variation of the height of the protrusion represented by the following formula (1), and In addition, a conductive particle in which two or more of the protrusions exist in a concentric circle that is ½ of the diameter of the orthographic projection plane when an arbitrary orthographic projection plane is taken is also one aspect of the present invention. .

Although it does not specifically limit as an average particle diameter of the electroconductive particle of this invention, A preferable minimum is 2.5 micrometers and a preferable upper limit is 15 micrometers. If it is less than 2.5 μm, it tends to aggregate when forming the conductive metal layer, making it difficult to form single particles. If it exceeds 15 μm, an electrode such as a substrate having fine wiring as an anisotropic conductive material It may exceed the range used between terminals.

The height of the protrusion is not particularly limited, but a preferable lower limit is 0.5% of the average particle diameter of the core particles, and a preferable upper limit is 25% of the average particle diameter of the core particles. If the average particle diameter of the core particles is less than 0.5%, sufficient resin exclusion may not be obtained. If the average particle diameter of the core particles exceeds 25%, protrusions may be formed on the circuit board or the like. There is a risk of digging deep and damaging the circuit board.

In the conductive particles of the present invention, τ is 10% or less, where τ is a variation coefficient of the height of the protrusion represented by the above formula (1). If it exceeds 10%, it becomes difficult to control the distance between the opposing electrodes using conductive particles.

The conductive particles of the present invention have two or more projections in a concentric circle that is ½ of the diameter of the orthographic projection surface when an arbitrary orthographic projection surface is taken. When the number is less than 2, high connection stability between the conductive particles and the circuit board cannot be exhibited.
The orthographic projection surface can be observed with, for example, a scanning electron microscope (SEM).

Further, the abundance ratio of the protrusions of the conductive particles of the present invention is not particularly limited, but a preferable lower limit is 20% and a preferable upper limit is 80% with respect to the entire surface. If it is less than 20%, the projection and the circuit board may not come into contact depending on the direction of the conductive particles. If it exceeds 80%, the projections overlap each other, and the conductive particles and the circuit board etc. When crimped, the protrusions may be difficult to collapse.
The abundance ratio of the protrusions of the conductive particles is determined by image analysis using a scanning electron microscope (SEM), and the covering area of the protrusions with respect to an area of 2.5 μm from the center of the conductive particles (that is, the projected area of the particle diameter of the protrusions). ) Can be obtained.

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

Specific examples of the anisotropic conductive material of the present invention include, for example, anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive adhesive layer, anisotropic conductive film, anisotropic conductive sheet and the like. Is mentioned.

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

In addition to the conductive particles of the present invention and the resin binder described above, the anisotropic conductive material of the present invention includes, for example, a bulking agent and a softening agent (if necessary) within a range not impairing the achievement of the problems of the present invention. Additives such as plasticizers), adhesive improvers, antioxidants (anti-aging agents), heat stabilizers, light stabilizers, UV absorbers, colorants, flame retardants, organic solvents, etc. Good.

The method for producing the anisotropic conductive material of the present invention is not particularly limited. For example, the conductive particles of the present invention are added to an insulating resin binder, and are uniformly mixed and dispersed. A method of using a conductive paste, anisotropic conductive ink, anisotropic conductive adhesive, etc., adding the conductive particles of the present invention to an insulating resin binder, and uniformly dissolving (dispersing), or , Heat-dissolve, and apply to the release treatment surface of the release material such as release paper and release film to have a predetermined film thickness, and perform drying and cooling as necessary, for example, anisotropic For example, an appropriate manufacturing method may be employed in accordance with the type of anisotropic conductive material to be manufactured.
Moreover, it is good also as an anisotropic conductive material by using separately, without mixing an insulating resin binder and the electroconductive particle of this invention.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of electroconductive particle, electroconductive particle, and anisotropic conductive material which can reduce a resistance value while preventing conduction failure can be provided.

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
A dispersion was prepared by dispersing 5 g of 4 μm divinylbenzene resin fine particles as core particles in 100 g of water.
A nickel plating solution was added to the obtained dispersion and electroless plating was performed to obtain nickel-plated particles. The thickness of the nickel plating was 70 nm.
Furthermore, 0.05 g of 2-aminoethanethiol was added as a chelating agent, heated at 80 ° C. for 30 minutes, the chelating agent was bound to the surface nickel plating layer, 0.05 g of polyacrylamide was added as resin fine particles, and 50 ° C. For 30 minutes to obtain particles in which resin fine particles are bonded to the surface of the nickel plating layer via a chelating agent. Electroless gold plating was performed on the obtained particles to produce conductive particles having a 50 nm gold plating layer formed on the surface.

(Example 2)
Conductive particles were produced in the same manner as in Example 1 except that 0.05 g of 4,4-diaminodiphenyl sulfide was used as the chelating agent.

(Comparative Example 1)
Conductive particles were produced in the same manner as in Example 1 except that no chelating agent was added.

<Evaluation>
The following evaluation was performed about the electroconductive particle obtained by the Example and the comparative example. The results are shown in Table 1.

(1) Surface observation SEM photographs of the surfaces of the conductive particles obtained in Examples and Comparative Examples were observed with a scanning electron microscope, and the uniformity of protrusions was evaluated visually according to the following criteria.
○ The protrusions were almost uniformly in both height and position.
Δ Either the height or position of the protrusion was uniform.
X The protrusions were uneven in height and position.

(2) Measurement of coefficient of variation and number of protrusions For the conductive particles obtained in the examples and comparative examples, the height of the protrusions was measured based on the observation image of the SEM photograph, and the fluctuation was determined according to the above equation (1). The coefficient τ was measured.
Further, in the measurement of (1), the number of protrusions existing in concentric circles that are 1/2 the diameter of the orthographic projection surface of the conductive particles was measured.

(3) Measurement of connection resistance value 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 resin binder resin After sufficiently mixing using a formula stirrer, the mixture was applied onto a release film so that the thickness after drying was 10 μm, and toluene was evaporated to obtain an adhesive film.
Next, the obtained 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 resin binder resin. Then, after sufficiently mixing using a planetary stirrer, it was applied on the release film so that the thickness after drying was 7 μm, and toluene was evaporated to obtain an adhesive film containing conductive fine particles. . In addition, the compounding quantity of electroconductive fine particles was made for the content in a film to be 50,000 piece / cm < ² >.
By laminating the obtained adhesive film and an adhesive film containing conductive fine particles at room temperature, an anisotropic conductive film having a two-layer structure and a thickness of 17 μm was obtained.
The obtained anisotropic conductive film was cut into a size of 5 × 5 mm. Affixed to the center of an ITO electrode having a width of 200 μm, a length of 1 mm, a height of 0.2 μm, and an L / S of 20 μm having a lead wire for resistance measurement on one side, and then a glass substrate having the same ITO electrode. After the alignment, the electrodes were pasted together.
The bonded portion of this glass substrate was thermocompression bonded under pressure bonding conditions of 40 MPa and 200 ° C., and then the resistance value between the electrodes was measured.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of electroconductive particle, electroconductive particle, and anisotropic conductive material which can reduce a resistance value while preventing conduction failure can be provided.

It is a schematic diagram of the orthographic projection surface of the electroconductive particle of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive particle 2 Protrusion 3 Gold layer R Diameter of conductive particle r Diameter of concentric circle whose diameter is 1/2 of the diameter of conductive particle

Claims (5)

A method for producing conductive particles having protrusions on the surface,
Step 1 of forming a nickel plating layer charged with positive or negative charges on the surface of the core particles,
A step 2 of attaching a chelating agent having a functional group A and a reactive functional group B in one molecule to the surface of the nickel plating layer via the functional group A;
A step of bonding resin fine particles or inorganic fine particles charged with a charge opposite to the charge charged on the nickel plated layer to the surface of the nickel plated layer via the reactive functional group B of the chelating agent; as well as,
A method for producing conductive particles, comprising a step 4 of coating the resin fine particles or inorganic fine particles and the nickel plating layer with metal plating by an electroless plating method. The method for producing conductive particles according to claim 1, further comprising a step 5 of forming a gold plating layer on the surface of the metal plating layer. It is the electroconductive particle manufactured by the manufacturing method of the electroconductive particle of Claim 1 or 2, Comprising:
When the variation coefficient of the height of the protrusion represented by the following formula (1) is τ, τ is 10% or less, and
A conductive particle comprising two or more protrusions in a concentric circle that is ½ the diameter of the orthographic projection plane when an arbitrary orthographic projection plane is taken.

The conductive particles according to claim 2, wherein the abundance ratio of the protrusions is 20 to 80% with respect to the entire surface. An anisotropic conductive material, wherein the conductive particles according to claim 3 or 4 are dispersed in a resin binder.

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