KR100736598B1 - Highly reliable conductive particles - Google Patents

Abstract

Provided are highly reliable conductive particles, which comprise polymer resin particles showing excellent adhesion to a metal layer, have excellent conductivity and electric connection reliability, and are useful for producing an anisotropic conductive adhesive film. The highly reliable conductive particles(1) comprise: polymer resin particles(11) having a plurality of fine pores and/or irregularities on the surface thereof and obtained through polymerization of 10-90 parts by weight of at least one crosslinkable monomer with 90-10 parts by weight of an unsaturated monomer copolymerizable with the crosslinkable monomer based on 100 parts of the total monomers; and a conductive metal layer(12) coated on the surface of the polymer resin particles.

Description

Highly Reliable Conductive Particles

1 is a schematic cross-sectional view of conductive fine particles according to the present invention.

2A and 2B are schematic cross-sectional views showing surfaces of polymer resin fine particles of conductive fine particles according to the present invention.

3A is a scanning electron microscope (SEM) photograph showing the surface of the polymer resin fine particles having fine pores on the surface according to Example 1 of the present invention, and FIG. 3B shows the surface of the conductive fine particles prepared using the polymer resin fine particles. .

Figure 4a is a scanning electron microscope (SEM) showing the surface of the polymer resin fine particles having fine pores and irregularities on the surface according to Example 2 of the present invention, Figure 4b shows the surface of the conductive fine particles produced using the polymer resin fine particles It is a photograph.

FIG. 5A is a scanning electron microscope (SEM) photograph showing the surface of the smooth polymer resin fine particles according to Comparative Example 1 of the present invention, and FIG. 5B is a surface of the conductive fine particles prepared using the polymer resin fine particles.

* Brief description of the major symbols in the drawings *

1: conductive fine particles 11: polymer resin fine particles

12: conductive metal layer

Field of invention

The present invention relates to conductive fine particles. More specifically, the present invention relates to conductive fine particles having excellent adhesion to plating and excellent electrical connection reliability by forming fine pores and / or irregularities on the surface of the polymer resin fine particles without an etching process.

Background of the Invention

Recently, the micro-electrode between electronic electrodes, such as the connection of the ITO electrode and the driver IC circuit of the liquid crystal display (LCD) substrate, the connection of the driver IC chip and the circuit board, and the connection of the fine pattern electrode terminal, etc. For the connection, conductive materials such as conductive metal fine particles or metal coated resin fine particles are used. In particular, in order to secure long-term reliability of the electrical connection and the connection state between the electrodes, conductive fine particles coated with a metal layer on polymer resin fine particles that are flexible in deformation and recovery are used. In recent years, as the pitch of the circuit to be connected becomes finer and the area of the bump electrode becomes smaller, the conductivity, adhesion, electrical reliability, and the like of the conductive fine particles used become more important for good electrical connection. .

Electroless plating is mainly applied as a method for producing conductive fine particles coated with a polymer layer on polymer resin fine particles. This method generally performs electroless plating after pretreatment processes such as cleaning and degreasing of the substrate fine particles, etching, and catalysis treatment. Japanese Patent No. 2507381, Japanese Patent Publication No. 06-096771, Japanese Patent Publication No. 02-24358, Japanese Patent Publication No. 2000-243132, Japanese Patent Publication No. 2003-64500, Japanese Patent Publication No. 2003-068143 Discloses a technique for the above electroless plating. In such an electroless plating method, in order for the plating layer to be firmly and uniformly adhered to the surface of the smooth polymer resin fine particles, it is necessary to have the surface of the substrate fine particles in advance by an etching process before the catalytic treatment. Such surface irregularities help to adsorb the catalyst, improve the plating property, bring about an anchor effect, and improve the adhesion of the plating layer.

By applying the etching process as described above, the surface is excessively etched according to the type of the substrate fine particle material to generate fine cracks, thereby lowering the properties required for the substrate fine particles, or sometimes dissolving the entire surface without partially etching the surface. Unevenness may not be obtained. In addition, if the etching liquid used in the etching step is not properly selected, not only a sufficient effect is obtained but also a problem such as aggregation occurs during etching occurs. Accordingly, efforts have been made to secure plating properties, adhesion, conductivity, and the like in the conductive fine particles while eliminating the etching process, which may complicate the process and increase the cost.

As an example, Japanese Patent Laid-Open No. 61-64882 discloses a method of electroless plating after introducing a noble metal ion into a surface of a synthetic resin substrate with a noble metal trapping surface treatment agent. Further, Japanese Patent Laid-Open No. 02-62960 discloses a method of catalyzing the surface by dispersing a large amount of active metal particles in a liquid organic binder and coating the surface of the substrate fine particles. However, the above methods improve the plating property by surface treatment but have a problem in that the plating layer is easily peeled off from the surface because metal plating is formed on the smooth surface.

Accordingly, the inventors of the present invention form excellent pores and / or irregularities on the surface of the polymer resin substrate microparticles without using an etching process so that the adhesion of the plating is excellent, the conductivity is excellent, and there is no peeling of the plating due to external force, so the electrical connection reliability is excellent. It is early to develop particulates.

An object of the present invention is to provide conductive fine particles having a plating layer having excellent adhesion to the surface of polymer resin fine particles by forming fine pores and / or irregularities on the surface of the polymer resin fine particles.

Another object of the present invention is to provide conductive fine particles having excellent conductivity and high electrical connection reliability.

Still another object of the present invention is to provide an anisotropic conductive adhesive film containing conductive fine particles having excellent adhesion and conductivity of a plating layer.

The above and other objects of the present invention can be achieved by the present invention described below.

Summary of the Invention

The conductive fine particles according to the present invention are prepared by polymerizing 10 to 90 parts by weight of at least one crosslinkable polymerizable monomer with respect to 100 parts by weight of the total monomers and 90 to 10 parts by weight of a polymerizable unsaturated monomer copolymerizable with the crosslinkable polymerizable monomer. It characterized in that it comprises a polymer resin fine particles having a plurality of fine pores and / or fine unevenness in the conductive metal layer coated on the surface of the polymer resin fine particles.

Fine pores and / or irregularities of the polymer resin fine particles can be visually observed when observed at 10,000 to 30,000 magnification using an electron microscope, and the average particle diameter of the fine pores is 1 to 50 nm, The volume is formed at 0.01 to 0.2 cm 3 / g. In addition, the average particle diameter of the polymer resin fine particles is preferably in the range of 1 to 20 µm.

It is most preferable to use divinylbenzene for the said crosslinkable polymerizable monomer, and the said conductive metal layer may be formed from the composite metal layer which consists of a nickel layer and a gold layer. The thickness of the said conductive metal layer can be made into the range of 0.01-1 micrometer.

The present invention includes an anisotropic conductive adhesive film containing the conductive fine particles.

Hereinafter, with reference to the accompanying drawings, the contents of the present invention will be described in detail.

Detailed Description of the Invention

1 is a schematic cross-sectional view of the conductive fine particles according to the present invention, Figures 2a and 2b is a schematic cross-sectional view showing the surface of the polymer resin fine particles of the conductive fine particles according to the present invention.

As shown in FIG. 1, the conductive fine particles 1 of the present invention are formed in a form in which the entire surface of the polymer resin fine particles 11 is coated with the conductive metal layer 12, and the polymer resin fine particles 11 are illustrated in FIG. As shown in 2a and 2b, the surface has a plurality of fine pores and / or fine irregularities. Fine pores or fine irregularities on the surface of the substrate fine particles may improve the adhesion by causing a physical anchor effect of the metal layer to be coated.

The material of the polymer resin fine particles 11 is not particularly limited, for example, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, polyamide, poly Mid, polysulfone, polyphenylene oxide, polyacetal, urethane resin, unsaturated polyester resin, (meth) acrylate resin, styrene resin, butadiene resin, epoxy resin, phenol resin, melamine resin and the like can be used.

However, in consideration of characteristics such as compression deformation and elastic recovery force required for anisotropic conductive connection, it is preferable to use styrene resin, (meth) acrylate resin or styrene-acrylate copolymer resin. In particular, it is most preferable to use a crosslinked polymer resin prepared using 10 to 90% by weight of the crosslinkable polymerizable monomer relative to the total amount of the monomers. When the content of the crosslinkable polymerizable monomer is less than 10%, the crosslinking density becomes low, so that it is difficult to have sufficient elastic recovery force, and when the content exceeds 90%, the crosslinking density becomes too high to obtain very hard fine particles. Therefore, there is a problem that does not deform well during electrical connection. In addition, the cross-polymerizable monomer is suitable for inducing fine phase separation between the monomer and the polymer during polymerization when copolymerized with the common polymerizable monomer, and thus has advantages in introducing fine pores or irregularities to the surface.

As in the present invention, a suspension polymerization method or a seed polymerization method may be suitably used as a method of preparing the polymer resin fine particles 11 while introducing micropores or irregularities on the surface.

For example, in the case of using the suspension polymerization method, porogen, which can form pores, is mixed with the polymerizable monomer to be polymerized, followed by suspension and polymerization, and washing and solvent treatment, if necessary. After the post treatment, fine pores may be formed on the surface. Here, porogen is a material that does not actually participate in polymerization, and means a material that can be easily removed by washing, dissolving, or drying after the polymerization process. Examples of porogens include organic solvents, linear organic polymers, waxes, and the like, which can be mixed with the polymerizable monomer but are insoluble in the suspension medium. These porogens are uniformly dissolved in the polymerizable monomer prior to the polymerization reaction and then undergo phase separation as heterogeneous materials with the polymer produced as the polymerization proceeds slowly. At this time, the porogen region formed by the microphase separation in the polymer polymerization process is later removed by washing or solvent treatment to form fine pores or irregularities. Furthermore, in consideration of such fine phase separation and solvent post-treatment, it is preferable to use a cross-linking polymerizable monomer or more in a predetermined amount so as to have a sufficient cross-linking structure insoluble in a solvent.

The porogen may be used in the seed polymerization method similar to the suspension polymerization method as the mechanism of the radical polymerization itself, and may serve to form fine pores or irregularities on the surface. The seed polymerization method is a method in which a polymerizable monomer is swelled to a polymer seed particle prepared beforehand and then polymerized. This is useful for obtaining fine particles having a very uniform particle size without a separate classification process. Therefore, if the porogen is mixed and used in the swollen polymerizable monomer, the same effect as in suspension polymerization can be obtained. However, in the case of using the seed polymerization method, porogen may be used as described above, but it is also possible to introduce surface pores or irregularities depending on conditions without using a separate porogen. Strictly speaking, however, it can be seen that the polymer seed particles not only act as substrates for swelling of the polymerizable monomer, but also function similar to porogens. Here, the selection of molecular weight and polymerizable monomer of the polymer seed particles plays an important role in inducing fine phase separation in the fine particles, which is advantageous for forming surface pores or surface irregularities. In order to cause fine phase separation necessary for introducing micropores or irregularities on the surface by the seed polymerization method, the molecular weight of the seed particles is preferably 10,000 or more. When the molecular weight of the seed particles is less than 10,000, since the free volume of the seed polymer chain is not so large, the phase separation is rarely prevented because it does not significantly prevent the polymerization behavior of the monomer to be secondaryly polymerized. However, when the molecular weight of the seed particles becomes too large, the physical properties of the finally formed polymer resin fine particles can be greatly reduced, so that the molecular weight is preferably limited to 30,000 or less. In addition, in order to maximize the fine phase separation during the polymerization process, it is advantageous that the polymer to be polymerized is not dissolved in the monomer, and for this purpose, it is preferable to use at least 10% by weight or more of the crosslinkable polymerizable monomer. Therefore, in order to introduce fine pores or unevenness to the surface by using the seed polymerization method, the molecular weight of the seed particles is about 10,000 to 30,000, and as the monomer to be swollen, it is necessary to use 10% by weight or more of the crosslinkable polymerizable monomer. Do.

Specific examples of the crosslinkable polymerizable monomer include divinylbenzene, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9-nonanediol di (meth) acryl Allyl compounds, such as a late, allyl (meth) acrylate, divinyl sulfone, diallyl phthalate, diallyl acrylamide, triallyl (iso) cyanurate, and triallyl trimellitate, and (poly) ethylene glycol di (meth) (Poly) alkylene glycol di (meth) acrylates such as) acrylate, (poly) propylene glycol di (meth) acrylate, (poly) dimethylsiloxane di (meth) acrylate, (poly) dimethylsiloxane divinyl, (Poly) urethane di (meth) acrylate, pentaaryl tritol tri (meth) acrylate, pentaaryl tritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (Meth) acrylate, te La and trimethylolpropane tetra (meth) acrylate, dipentaerythritol tree in Reel Tall hexa (meth) acrylate, penta the reel tree tolyl-penta (meth) acrylate, glycerol tri (meth) acrylate and the like. Among them, divinylbenzene can be used most preferably.

Moreover, it does not specifically limit as a monomer used together with the said crosslinkable polymerizable monomer, The polymerizable unsaturated monomer copolymerizable with the said crosslinkable polymerizable monomer is mentioned. Specific examples of the polymerizable unsaturated monomer include styrene monomers such as styrene, ethyl vinyl benzene, α-methyl styrene, m-chloromethyl styrene, methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth). Acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (Meth) acrylate, stearyl (meth) acrylate, ethylene glycol (meth) acrylate, glycidyl (meth) acrylate, vinyl chloride, acrylic ester, acrylonitrile, vinyl acetate, vinyl propionate, vinyl Butyrate, vinyl ether, allyl butyl ether, butadiene, isoprene and the like.

If micropores and / or irregularities formed on the surface of the base resin fine particles 11 of the present invention can be visually observed when observed at 10,000 to 30,000 magnification with a scanning electron microscope (SEM), plating adhesion by effective anchoring and The improvement of plating uniformity etc. can be shown. For example, when the metal layer by electroless plating is plated on the polymer resin fine particles 11 showing fine pores or irregularities on the surface at the electron microscope magnification in the above range, as shown in FIGS. 3 and 4, the structure is uniform and dense. It can be seen that the plating layer of. On the other hand, when using the substrate fine particles having a smooth surface as shown in Figure 5, the metal layer introduced by the electroless plating is non-uniform and the surface is not sufficiently coated. Furthermore, the smooth surface of the substrate fine particles is inferior in plating adhesion of the metal layer, causing the plating layer to peel off from the surface of the substrate fine particles, or exhibiting a tendency to become brittle due to lack of compactness of the plating layer.

The polymer resin fine particles 11 of the present invention have a plurality of fine pores or fine irregularities on the surface thereof in order to improve plating adhesion, compactness and uniformity, and more specifically, the average size of the fine pores is 1 to 50 nm. And the volume of the fine pores is 0.01 to 0.2 cm 3 / g. The average size of micropores below 1 nm may help adsorption of precious metal catalyst ions, but it is difficult to achieve the desired sufficient physical anchoring effect. On the other hand, when the average size of the fine pores is more than 50 nm it may be difficult to maintain the physical properties of the originally expected substrate fine particles. In other words, when pressure or a force from the outside is applied to the substrate fine particles, excessively large surface pores may be a functioning point for promoting cracks or breakage. In addition, the volume of the micropores is determined according to the size, distribution, and number of the micropores, which is preferably 0.01 to 0.2 cm 3 / g. If the volume of the pores is less than 0.01 cm 3 / g, the pores formed on the surface is too small to obtain the effect of the surface fine pores, on the contrary, if the volume of the pores exceeds 0.2 cm 3 / g is too porous, the surface of the conductive metal layer is large It may be rough or may damage the physical properties of the substrate particles or the metal layer to be plated.

The polymer resin fine particles 11 used as the base material for the highly reliable conductive fine particles 1 for anisotropic conductive connection of the present invention are spherical fine particles, preferably having an average particle diameter of 1 to 20 μm, more preferably 2 to 10 μm. to be. When the particle size of the fine particles is less than 1 μm, a problem occurs in that the fine particles are agglomerated, and the conductive fine particles using the base fine particles having a particle size of more than 20 μm are rarely used in recent fine mounting materials.

The manufacturing method of the polymer resin microparticles | fine-particles 11 used in this invention is not specifically limited, For example, suspension polymerization, dispersion polymerization, precipitation polymerization, seed polymerization, seed polymerization Seeded polymerization, soap-free emulsion polymerization, etc. may be used as appropriate. Among them, it is advantageous to use a seed polymerization method in order to obtain fine particles having a very uniform particle size without a separate classification process, and suspension polymerization is advantageous to control physical properties by copolymerizing various monomers by type, but uniform particle size You must go through a classification process to make it work.

In the present invention, an electroless plating method may be used as a method of coating the conductive metal layer 12 on the polymer resin substrate fine particles 11. Such an electroless plating method is conventionally performed in the order of electroless plating after a pretreatment process such as cleaning and degreasing of the substrate fine particles, etching, and catalyzing treatment. Here, as a pretreatment of electroless plating, the catalytic treatment process adsorbs and reduces precious metal ions such as palladium chloride (Pd) on the surface of the plating substrate, so that the metal palladium is supported on the surface, thereby catalyzing subsequent electroless plating. It is a process to function as a nucleus. If such a palladium catalyst nucleus is formed unevenly or sufficiently on the surface of the substrate fine particles, the growth of the electroless plating layer based on such nucleus becomes uneven or it is difficult to obtain a sufficient plating reaction as desired depending on the input.

By using the polymer resin fine particles 11 having fine pores and / or fine irregularities on the surface as in the present invention, by eliminating the etching process and inducing uniform and sufficient adsorption of the palladium catalyst on the surface, Uniform plating property and the compactness and adhesiveness of a conductive metal layer can be improved. That is, in the present invention, since the polymer resin fine particles 11 having fine pores or irregularities on the surface are used, the etching step in the prior art is not introduced. In the present invention, the conductive metal layer may be formed of a composite metal layer of a nickel layer and a gold layer by performing electroless gold plating after electroless nickel plating.

In the present invention, when the base resin fine particles 11 are immersed in a tin chloride and palladium chloride solution for electroless plating, and subjected to catalysis and activation on the surface, fine nuclei of a palladium catalyst are formed on the surface of the base fine particles. When the reduction reaction is continued with sodium hypophosphite, sodium borohydride, dimethyl amine borane, hydrazine and the like, uniform nuclei of palladium are formed on the resin fine particles. Thus, the substrate fine particles having palladium nuclei are dispersed in an electroless nickel plating solution, and then nickel salts are reduced with sodium hypophosphite to form an electroless nickel plating layer. Subsequently, when the nickel plated fine particles are added to an electroless gold plating solution at a predetermined concentration to perform a substitution plating reaction or an electroless gold plating of gold, a nickel / gold composite plating film layer having gold deposited on the outermost layer is formed. . However, in some cases, a gold plating solution may be added during electroless nickel plating to form a composite plating layer having a nickel / gold concentration gradient. In other words, the conductive metal layer has a concentration gradient in which the nickel concentration gradually decreases and the gold concentration gradually increases from the surface of the polymer fine particles toward the outermost portion, but the surface of the metal layer is a nickel / gold composite plating layer made of gold.

In the conductive fine particles 1 of the present invention, the thickness of the conductive metal layer 12 is preferably 0.01 to 1 m. When the thickness of the metal layer is less than 0.01 μm, it is difficult to obtain desired conductivity. On the contrary, when the thickness of the metal layer exceeds 1 μm, the deformation, flexibility, and recovery properties of the fine particles are not properly expressed by the thick metal layer. Aggregation between particles easily occurs during use, making it difficult to have excellent conductivity. The thickness of the more preferable metal layer 12 is 0.05-0.5 micrometer.

The conductive fine particles 1 according to the present invention have excellent porosity and plating uniformity, good plating uniformity, denseness, and the like by having fine pores or fine unevennesses on the surface of the polymer resin substrate fine particles 11, and thus can be mixed with an adhesive resin or a solvent. When the conductive metal layer 12 is not easily peeled off by external force such as shear force or pressure, the electrical connection reliability is excellent. Such conductive fine particles of the present invention may be used as a conductive filler having excellent anisotropic conductive connection performance, and may be applied to the conductive fine particles to prepare an anisotropic conductive adhesive composition or a film having excellent connection and connection reliability.

The present invention will be further illustrated by the following examples, which are merely illustrative of the present invention and are not intended to limit or limit the scope of the present invention.

Example

Example  One

Synthesis of Polymer Resin Fine Particles

30 parts by weight of styrene monomer, 1.2 parts by weight of 2,2'-azobis (isobutyronitrile) as an initiator, 4.0 parts by weight of polyvinylpyrrolidone (molecular weight 40,000) as a dispersion stabilizer, and 200 parts by weight of methanol as a reaction medium The solution was quantified and introduced into the reactor, followed by polymerization for 24 hours in a nitrogen atmosphere at 70 ° C. to prepare seed particles. The particle size of the prepared seed particles was measured using a Coulter counter (manufactured by Beckman Coulter, Multisizer III), and the average particle size was 1.08 µm and the CV value (Coefficient of Variation) was 3.5%. The CV value is a% value obtained by dividing the standard deviation of the particle size by the average particle size, and is an important criterion for measuring the size dispersion of the particles. In addition, the molecular weight of the seed particles analyzed using gel permeation chromatography (GPC) was 12,500 g / mol. A latex containing 2 parts by weight of the prepared seed particles was uniformly dispersed in pure water to prepare a seed aqueous dispersion in 350 parts by weight. Subsequently, 30 parts by weight of divinylbenzene (DVB) and 70 parts by weight of styrene mixed with 400 parts by weight of a 0.2% by weight aqueous solution of sodium lauryl sulfate (SLS) in 4.0 parts by weight of a benzoyl peroxide initiator were emulsified with a homogenizer for 10 minutes, and then seeded. It was added to the particle dispersion and swollen at room temperature. After confirming that the monomer swelling was completed, 500 parts by weight of a 1% by weight aqueous solution of polyvinyl alcohol having a degree of saponification of 90% was added and nitrogen was charged into the reactor, and the temperature of the reactor was increased to 80 ° C and polymerized for 15 hours. Divinylbenzene-styrene crosslinked polymer (PDVB) fine particles prepared above were washed several times with pure water and ethanol and dried. The average particle diameter of the prepared polymer resin fine particles was 4.0 μm and the CV value was 3.7%, indicating a very uniform particle size distribution. An electron micrograph of the prepared polymer resin microparticles is shown in FIG. 3. As shown in Figure 3a, it can be seen that a number of fine pores are uniformly distributed on the entire surface of the fine particles. As a result of analyzing the surface pores by BET measurement, the average pore size was 7 nm and the volume was 0.018 cm 3 / g.

Preparation of Conductive Fine Particles

10 g of the polymer resin fine particles were immersed in a 10% hydrochloric acid solution for 10 minutes without a separate etching process, and immersed in a mixed solution of tin chloride (1 g / L) and palladium chloride (0.1 g / L) for 10 minutes. After filtration it was washed. Subsequently, palladium ions adsorbed on the surface of the substrate fine particles were reduced using an aqueous sodium hypophosphite solution to form fine nuclei.

Thereafter, the electroless plating process was performed with slow stirring to prevent the catalyzed substrate fine particles from agglomerating, adhering, or sedimenting upon plating to form a non-uniform coating. First, 20 g of the pretreated base resin fine particles were placed in a stirring plating bath and sufficiently dispersed, and then an electroless nickel plating solution was added to form a nickel film. At this time, the nickel electroless plating solution was made of nickel sulfate (50 g) and sodium hypophosphite, the equivalent ratio was 1: 2, and electroless nickel plating was performed at 60 ° C for 30 minutes. The pH of the plating reaction was constantly adjusted to 7 using an aqueous ammonia solution. After the nickel plating film was formed, an electroless gold plating solution was injected to form a nickel / gold composite plating film. The plating solution used for electroless gold plating uses 15 g of gold potassium cyanide (KAu (CN) ₂ ) as a precursor of gold (Au), and potassium cyanide (KCN), potassium hydroxide (KOH), potassium carbonate (K ₂ CO ₃ ) as the main raw material, the plating solution composition is already well known to the company and can be easily carried out. After washing and filtering after electroless gold plating, conductive fine particles plated with a nickel / gold composite metal layer were obtained, washed well with alcohol again, and vacuum dried.

An electron micrograph of the conductive fine particles obtained above is shown in FIG. 3B. As shown in the figure, it can be seen that the metal layer of the conductive fine particles is uniformly and densely plated on the entire surface of the substrate fine particle. In addition, in order to evaluate the plating adhesion of the fine particles, the conductive fine particles were interposed between the two slide glasses in small amounts, rubbed 20 times with a constant force, and peeling of the plating layer was observed by an electron microscope. As a result, it was confirmed that peeling or detachment of the plating layer was not found and remained stable.

Example  2

The polymer resin fine particles used in Example 2 were prepared by mixing 80 parts by weight of divinylbenzene and 20 parts by weight of styrene instead of using 30 parts by weight of divinylbenzene and 70 parts by weight of styrene in the Seeded polymerization process. Except that used, it was prepared in the same manner as in Example 1. The prepared polymer resin fine particles had an average particle diameter of 4.0 μm and a CV value of 3.6%. An electron micrograph of the prepared polymer resin microparticles is shown in FIG. 4. As shown in Figure 4a, it can be seen that a number of fine pores and irregularities are uniformly distributed on the entire surface of the fine particles. As a result of analyzing the surface pores by BET measurement, the average pore size was 17 nm and the volume was 0.05 cm 3 / g.

Subsequently, electroless plating was performed in the same manner as in Example 1 using the prepared polymer resin fine particles to prepare conductive fine particles. An electron micrograph of the obtained conductive fine particles is shown in FIG. 4B. As shown in FIG. 4B, it can be seen that the metal layer is uniformly and densely plated on the entire surface of the substrate fine particles. In addition, as a result of evaluating the plating adhesion of the fine particles in the same manner as in Example 1, it was confirmed that the conductive fine particles without peeling or detachment of the plating layer.

Comparative Example  One

Polymeric resin-based fine particles of Comparative Example 1 was 5 parts by weight of divinylbenzene and 95 parts by weight of styrene instead of using 30 parts by weight of divinylbenzene and 70 parts by weight of mixed monomers in the Seeded polymerization process in Example 1 It was prepared in the same manner as in Example 1 except that a negative mixed monomer was used. The prepared polymer resin fine particles had an average particle diameter of 4.0 μm and a CV value of 3.8%. An electron micrograph of the prepared polymer resin microparticles is shown in FIG. 5. As shown in FIG. 5A, the surface of the base resin fine particles was very smooth, and no fine pores or fine irregularities were observed. As a result of analyzing the surface pores by the BET measurement method, the fine pores were not largely confirmed, and the volume was very low as 0.003 cm 3 / g.

Subsequently, electroless plating was performed in the same manner as in Example 1 using the prepared polymer resin fine particles to prepare conductive fine particles. An electron micrograph of the obtained conductive fine particles is shown in FIG. 5B. As shown in FIG. 5B, the metal layer is formed non-uniformly on the surface of the substrate fine particle, the density of the plating layer is also inferior, and some of the conductive particles are peeled off and separated. In addition, as a result of evaluating the plating adhesion of the fine particles in the same manner as in Example 1, it was found that the peeling or detachment of the plating layer was considerably large, so that the plating adhesion to the surface without fine pores or fine unevenness was significantly reduced. I could see.

Evaluation method of conductive fine particles

Inductively coupled plasma spectroscopy (ICP) was used to measure the plated layer thickness of the prepared conductive fine particles. First, nickel / gold plated conductive fine particles were added to nitric acid: hydrochloric acid 3: 1 volume fraction of aqua regia to completely dissolve the nickel and gold plated layers, and then the solution was subjected to ICP spectroscopic analysis to determine the contents of nickel, gold, and phosphorus. It could be obtained in weight percent. The thicknesses of the nickel layer and the gold layer plated on the surface of the polymer resin fine particles were calculated by using the calculated weight% and the specific specific gravity, the specific gravity and the average particle diameter of the polymer substrate fine particles, and the like.

In the electrical resistance measurement of the conductive fine particles, the compression resistance was measured by the electrical resistance value of the single particles, and 20 fine particles for each sample were measured and expressed as their average values. In this case, the compressive resistance was used as the same micro-compression tester as described above, and was expressed as the resistance (10% compression resistance) at the time when the fine particles were subjected to 10% compression deformation in the initial state before deformation by force. The volume resistance was measured by the electrical resistance value of the conductive particulate bulk powder, and the results are shown in Table 1. The volume resistance is a value obtained by the following equation (1) from an insulating cylinder having a diameter of 1 cm, filled with conductive fine particles, and provided with electrodes at both ends of the cylinder, and then subjected to voltage to measure the resistance and the volume of the filled conductive fine particles.

[Equation 1]

Volume resistivity ^{= πd 2/4 (h-} h ') × RV

Where h is the height after filling the sample, h 'is the height before filling the sample, Rv is the resistance stationary, and d is the diameter of the insulating cylinder.

In addition, by measuring the resistance at 50% compression deformation (50% compression resistance), it can be confirmed by the change in the resistance value whether the plating layer peels or breaks when the microparticles are excessively deformed. When the conductive fine particles deform, the contact area with the upper and lower compression electrodes becomes wider, so that the resistance gradually decreases or at least remains constant. In the case where the adhesion of the plating is poor, peeling or breaking of the plating layer occurs during compressive deformation. On the contrary, the resistance tends to rise. Therefore, the adhesion and reliability of the conductive metal layer to the polymer-based fine particles were indirectly determined by observing the 50% compression resistance.

As shown in Table 1, the conductive fine particles plated using the polymer resin fine particles having micropores and / or fine unevenness according to the present invention as a substrate, the uniformity of the metal layer after plating, compared to the conductive fine particles plated on a smooth surface, It is excellent in compactness and low in single particle compression resistance and volume resistance, and also has excellent electrical adhesion reliability due to excellent plating adhesion without peeling of the plating layer even when subjected to shear force or deformation by external force.

The present invention has a plating layer having excellent adhesion to the surface of the polymer resin fine particles by forming fine pores and / or irregularities on the surface of the polymer resin fine particles, providing conductive fine particles having excellent electrical conductivity and high electrical connection reliability. It has the effect of providing the anisotropically conductive adhesive film containing conductive fine particles excellent in adhesion and conductivity.

Simple modifications and variations of the present invention can be readily used by those skilled in the art, and all such variations or modifications can be considered to be included within the scope of the present invention.

Claims (8)

10 to 90 parts by weight of at least one crosslinkable polymerizable monomer with respect to 100 parts by weight of the total monomers and 90 to 10 parts by weight of the polymerizable unsaturated monomer copolymerizable with the crosslinkable polymerizable monomer to prepare a plurality of fine pores on the surface and / Or polymer resin fine particles in which fine unevenness is formed; And A conductive metal layer coated on the surface of the polymer resin fine particles; Conductive fine particles, characterized in that consisting of. The conductive fine particles of claim 1, wherein the fine pores and / or irregularities of the polymer resin fine particles are visually observed when observed at 10,000 to 30,000 magnification using an electron microscope. The conductive fine particles according to claim 1, wherein the average pore size of the fine pores is 1 to 50 nm, and the volume of the fine pores is 0.01 to 0.2 cm 3 / g. Electroconductive fine particle of Claim 1 whose average particle diameter of the said polymeric resin microparticle is 1-20 micrometers. The method of claim 1, wherein the crosslinkable polymerizable monomer is divinylbenzene, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth). ) Allyl compounds of acrylate, allyl (meth) acrylate, divinyl sulfone, diallyl phthalate, diallyl acrylamide, triallyl (iso) cyanurate, triallyl trimellitate, and (poly) ethylene glycol di ( Meta) acrylate, (poly) alkylene glycol di (meth) acrylate of (poly) propylene glycol di (meth) acrylate, (poly) dimethylsiloxane di (meth) acrylate, (poly) dimethylsiloxane divinyl, (Poly) urethane di (meth) acrylate, pentaaryl tritol tri (meth) acrylate, pentaaryl tritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (Meth) acrylate, tetramethyl Propane tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, inpentaryltritol penta (meth) acrylate, and glycerol tri (meth) acrylate Conductive fine particles made of. The conductive fine particle of claim 1, wherein the conductive metal layer is a composite metal layer including a nickel layer and a gold layer. The conductive fine particles according to claim 1, wherein the conductive metal layer has a thickness of 0.01 to 1 m. Anisotropically conductive adhesive film comprising the conductive fine particles according to any one of claims 1 to 7.

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