JP2014241278A - Conductive particles, conductive material, and connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide conductive particles capable of enhancing conduction reliability when electrically connecting electrodes.SOLUTION: Conductive particles 1 according to the present invention each include a base material particle 2 and a conductive layer 3 disposed on the surface of the base material particle 2. The base material particle 2 has a compressive elastic modulus of 1,000 N/mmor more when compressed by 10%. The conductive layer 3 has a palladium layer on the outer surface side. The content of palladium is 99.9 wt.% or more in 100 wt.% of the palladium layer.

Description

  The present invention relates to conductive particles having substrate particles and a conductive layer disposed on the surface of the substrate particles. The present invention also relates to a conductive material and a connection structure using the conductive particles.

  Anisotropic conductive materials such as anisotropic conductive pastes and anisotropic conductive films are widely known. In the anisotropic conductive material, conductive particles are dispersed in a binder resin.

  In order to obtain various connection structures, the anisotropic conductive material is, for example, a connection between a flexible printed circuit board and a glass substrate (FOG (Film on Glass)) or a connection between a semiconductor chip and a flexible printed circuit board (COF ( Chip on Film)), connection between a semiconductor chip and a glass substrate (COG (Chip on Glass)), connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)), and the like.

  As an example of the conductive particles, in Patent Document 1 below, a base plating layer having a thickness of 1 to 2 nm and an intermediate plating layer having a thickness of 20 to 100 nm are formed on the surface of a base particle having an average particle diameter of 1 to 10 μm. And conductive particles in which a finish plating layer having a thickness of 10 to 50 nm is sequentially formed is disclosed. In Patent Document 1, a gold layer and a palladium layer are listed as specific examples of the finish plating layer. In Patent Document 1, it is described that a sputtering method is optimal as a method for forming the base plating layer on the surface of the base particle, and in addition to the sputtering method, a vacuum deposition method, a CVD method, and the like are described. It is described that there are various plating methods.

  Patent Document 2 below discloses conductive particles in which a noble metal coating layer is formed by physical vapor deposition on the surface of silicone rubber particles having an average particle size of 0.1 to 100 μm. Patent Document 2 describes that, as the physical vapor deposition method, a vacuum vapor deposition method can also be adopted, but it is preferable to use a sputtering method. Gold, silver, copper, platinum, palladium, nickel, etc. are mentioned as a noble metal for forming the said noble metal coating layer.

JP 2007-103222 A JP 2004-238588 A

  In the conductive particles described in Patent Document 1, when the palladium layer is formed as the finish plating layer and the electrodes are electrically connected using the obtained conductive particles, the conduction reliability is reduced. There's a problem. Even with the conductive particles described in Patent Document 2, the conduction reliability may not be sufficiently high.

  The objective of this invention is providing the electroconductive particle which can improve conduction | electrical_connection reliability, when electrodes are electrically connected. Another object of the present invention is to provide a conductive material and a connection structure using the conductive particles.

According to a wide aspect of the present invention, the substrate includes a base particle and a conductive layer disposed on the surface of the base particle, and the compressive elastic modulus when the base particle is compressed by 10% is 1000 N / mm ^2. Thus, conductive particles are provided in which the conductive layer has a palladium layer on the outer surface side and the palladium content is 99.9% by weight or more in 100% by weight of the palladium layer.

  On the specific situation with the electroconductive particle which concerns on this invention, the thickness of the said palladium layer is less than 20 nm.

  On the specific situation with the electroconductive particle which concerns on this invention, the said palladium layer is directly arrange | positioned on the surface of the said base particle.

  On the specific situation with the electroconductive particle which concerns on this invention, the said base particle is a resin particle or a core-shell type organic-inorganic hybrid particle.

  On the specific situation with the electroconductive particle which concerns on this invention, the said base material particle is the said organic-inorganic hybrid particle.

  On the specific situation with the electroconductive particle which concerns on this invention, the said conductive layer has a some protrusion on the outer surface.

  On the specific situation with the electroconductive particle which concerns on this invention, the said electroconductive particle is equipped with the insulating substance arrange | positioned on the outer surface of the said conductive layer.

  According to a wide aspect of the present invention, there is provided a conductive material including the above-described conductive particles and a binder resin.

  According to a wide aspect of the present invention, a first connection target member having a first electrode on the surface, a second connection target member having a second electrode on the surface, the first connection target member, and the A connection portion connecting the second connection target member, and the connection portion is formed of the above-described conductive particles or formed of a conductive material including the conductive particles and a binder resin. There is provided a connection structure in which the first electrode and the second electrode are electrically connected by the conductive particles.

The conductive particle according to the present invention includes a base particle and a conductive layer disposed on the surface of the base particle, and a compression elastic modulus when the base particle is compressed by 10% is 1000 N / mm ² or more. When the conductive layer has a palladium layer on the outer surface side and the palladium content in the palladium layer 100% by weight is 99.9% by weight or more, the electrodes are electrically connected. , Conduction reliability can be improved.

FIG. 1 is a cross-sectional view showing conductive particles according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view showing conductive particles according to the second embodiment of the present invention. FIG. 3 is a cross-sectional view showing conductive particles according to the third embodiment of the present invention. FIG. 4 is a cross-sectional view schematically showing a connection structure using conductive particles according to the first embodiment of the present invention. FIG. 5 is a schematic view showing one side surface of the sputtering apparatus used in Comparative Example 1. 6 is a schematic view of a cross section taken along the line II-II in FIG.

  Details of the present invention will be described below.

(Conductive particles)
The electroconductive particle which concerns on this invention is equipped with a base material particle and the electroconductive layer arrange | positioned on the surface of the said base material particle. The compression elastic modulus (10% K value) when the substrate particles are compressed by 10% is 1000 N / mm ² or more. The conductive layer has a palladium layer on the outer surface side. In 100% by weight of the palladium layer, the content of palladium is 99.9% by weight or more.

  By employing the above-described configuration in the present invention, conduction reliability can be improved when the electrodes are electrically connected using the conductive particles according to the present invention. Furthermore, by adopting the above-described configuration in the present invention, it is possible to improve the thermal shock reliability in the connection structure using the conductive particles.

The compression elastic modulus (10% K value) when the substrate particles are compressed by 10% is 1000 N / mm ² or more. The high 10% K value greatly contributes to the improvement of the conduction reliability between the electrodes. From the viewpoint of enhancing the conduction reliability further, the 10% K value is preferably 1500 N / mm ² or more, more preferably 4000 N / mm ² or more. The upper limit of the 10% K value is not particularly limited. The 10% K value may be less than or equal 15000 N / mm ^2, may also be 10000 N / mm ² or less, or may be 6000 N / mm ² or less.

  The compression elastic modulus (10% K value) of the substrate particles can be measured as follows.

  Using a micro-compression tester, the substrate particles are compressed under the conditions of a smooth indenter end face of a cylinder (diameter 100 μm, made of diamond) at 25 ° C., a compression rate of 0.3 mN / sec, and a maximum test load of 20 mN. The load value (N) and compression displacement (mm) at this time are measured. From the measured value obtained, the compression elastic modulus can be obtained by the following formula. As the micro compression tester, for example, “Fischer Scope H-100” manufactured by Fischer is used.

10% K value (N / mm ² ) = (3/2 ^1/2 ) · F · S ⁻³ / ² · R ^−1/2
F: Load value (N) when the base material particle is 10% compressively deformed
S: Compression displacement (mm) when the substrate particles are 10% compressively deformed
R: radius of base particle (mm)

  The compression elastic modulus represents the hardness of the base particle universally and quantitatively. By using the compression elastic modulus, the hardness of the base particle can be expressed quantitatively and uniquely.

  When the conductive layer is a single conductive layer, the conductive layer is a palladium layer, and the palladium layer is directly disposed on the surface of the base particle. When the conductive layer is a multilayer conductive layer, the multilayer conductive layer has a palladium layer on the outer surface side.

  In 100% by weight of the palladium layer, the content of palladium is 99.9% by weight or more. The palladium content in the palladium layer is quite high. The fact that the palladium content in the palladium layer is quite high greatly contributes to the improvement of the reliability of conduction between the electrodes.

  Hereinafter, the present invention will be clarified by describing specific embodiments and examples of the present invention with reference to the drawings.

  FIG. 1 is a cross-sectional view showing conductive particles according to the first embodiment of the present invention.

  As shown in FIG. 1, the conductive particle 1 includes base material particles 2 and a conductive layer 3. The conductive layer 3 is a palladium layer. The palladium layer is the outermost layer.

  The conductive layer 3 is directly disposed on the surface of the base particle 2. The conductive particle 1 is a coated particle in which the surface of the base particle 2 is coated with the conductive layer 3.

  The conductive particles 1 do not have a core substance. The conductive particles 1 do not have protrusions on the surface. The conductive particles 1 are spherical. The conductive layer 3 has no protrusion on the outer surface. Thus, the electroconductive particle which concerns on this invention does not need to have a processus | protrusion, and may be spherical. Moreover, the electroconductive particle 1 does not have an insulating substance. However, the conductive particles 1 may not have an insulating material disposed on the outer surface of the conductive layer 3.

  FIG. 2 is a cross-sectional view showing conductive particles according to the second embodiment of the present invention.

  The conductive particles 11 shown in FIG. 2 have base material particles 2 and a conductive layer 12. The conductive layer 12 has a first conductive layer 12A on the inner surface side and a second conductive layer 12B on the outer surface side. The second conductive layer 12B is a palladium layer.

  Only the conductive layer is different between the conductive particles 1 and the conductive particles 11. That is, the conductive particle 1 has a single conductive layer 3, whereas the conductive particle 11 has a multilayer conductive layer 12, and the conductive layer 12 is the first conductive layer 12 A. And the second conductive layer 12B.

  The conductive layer 12 is disposed on the surface of the base particle 2. 12 A of 1st conductive layers are arrange | positioned between the base particle 2 and the 2nd conductive layer 12B. Accordingly, the first conductive layer 12A is disposed on the surface of the base particle 2, and the second conductive layer 12B is disposed on the surface of the first conductive layer 12A.

  FIG. 3 is a cross-sectional view showing conductive particles according to the third embodiment of the present invention.

  A conductive particle 21 shown in FIG. 3 includes a base particle 2, a conductive layer 22, a core material 23, and an insulating material 24. The conductive layer 22 is a palladium layer. The conductive layer 22 is disposed directly on the surface of the base particle 2.

  The conductive particles 21 have protrusions 21a on the conductive surface. There are a plurality of protrusions 21a. The conductive layer 22 has a plurality of protrusions 22a on the outer surface. A plurality of core substances 23 are arranged on the surface of the base particle 2. The plurality of core materials 23 are embedded in the conductive layer 22. The core substance 23 is disposed inside the protrusions 21a and 22a. The conductive layer 22 covers a plurality of core materials 23. The outer surface of the conductive layer 22 is raised by the plurality of core materials 23, and protrusions 21a and 22a are formed. Thus, the electroconductive particle which concerns on this invention may have a processus | protrusion on the electroconductive surface. The conductive particles according to the present invention may have protrusions on the outer surface of the conductive layer, and the conductive layer may have protrusions on the outer surface. The palladium layer preferably has protrusions on the outer surface.

  The conductive particles 21 have an insulating material 24 disposed on the outer surface of the conductive layer 22. At least a part of the outer surface of the conductive layer 22 is covered with an insulating material 24. The insulating substance 24 is made of an insulating material and is an insulating particle. Thus, the electroconductive particle which concerns on this invention may have the insulating substance arrange | positioned on the outer surface of an electroconductive layer.

  Hereinafter, other details of the conductive particles according to the present invention will be described.

[Base material particles]
Examples of the substrate particles include resin particles, inorganic particles excluding metals, organic-inorganic hybrid particles, and metal particles. The substrate particles are preferably substrate particles excluding metal particles, and more preferably resin particles, inorganic particles excluding metal, or organic-inorganic hybrid particles.

  The substrate particles are more preferably resin particles or organic-inorganic hybrid particles, and may be resin particles or organic-inorganic hybrid particles. By using these preferable base particles, conductive particles more suitable for electrical connection between the electrodes can be obtained.

  When connecting between electrodes using the said electroconductive particle, after arrange | positioning the said electroconductive particle between electrodes, the said electroconductive particle is compressed by crimping | bonding. When the substrate particles are resin particles or organic-inorganic hybrid particles, the conductive particles are easily deformed during the pressure bonding, and the contact area between the conductive particles and the electrode is increased. For this reason, the conduction | electrical_connection reliability between electrodes becomes still higher.

  Various organic materials are suitably used as the resin for forming the resin particles. Examples of the resin for forming the resin particles include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; Alkylene terephthalate, polycarbonate, polyamide, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polysulfone, polyphenylene Oxide, polyacetal, polyimide, polyamideimide, polyether ether Tons, polyethersulfone, and polymers such as obtained by a variety of polymerizable monomer having an ethylenically unsaturated group is polymerized with one or more thereof. Resin for forming the resin particles can be designed and synthesized, and the hardness of the base particles can be easily controlled within a suitable range, which is suitable for conductive materials and having physical properties at the time of compression. Is preferably a polymer obtained by polymerizing one or more polymerizable monomers having a plurality of ethylenically unsaturated groups.

  When the resin particles are obtained by polymerizing a monomer having an ethylenically unsaturated group, the monomer having an ethylenically unsaturated group includes a non-crosslinkable monomer and a crosslinkable monomer. And so on.

  Examples of the non-crosslinkable monomer include styrene monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth) acrylic acid, maleic acid, and maleic anhydride; (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 ( Alkyl (meth) acrylates such as meth) acrylate and isobornyl (meth) acrylate; oxygen such as 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, polyoxyethylene (meth) acrylate and glycidyl (meth) acrylate (Meth) acrylates; nitrile-containing monomers such as (meth) acrylonitrile; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether; vinyl acids such as vinyl acetate, vinyl butyrate, vinyl laurate, vinyl stearate Esters; Unsaturated hydrocarbons such as ethylene, propylene, isoprene and butadiene; Halogen-containing monomers such as trifluoromethyl (meth) acrylate, pentafluoroethyl (meth) acrylate, vinyl chloride, vinyl fluoride and chlorostyrene Is mentioned.

  Examples of the crosslinkable monomer include tetramethylolmethane tetra (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and dipenta Erythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, glycerol tri (meth) acrylate, glycerol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) Polyfunctional (meth) acrylates such as acrylate, (poly) tetramethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate; triallyl (iso) cyanure Silane-containing monomers such as triallyl trimellitate, divinylbenzene, diallyl phthalate, diallylacrylamide, diallyl ether, γ- (meth) acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, vinyltrimethoxysilane It is done.

  The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group by a known method. Examples of this method include a method of suspension polymerization in the presence of a radical polymerization initiator, and a method of polymerizing by swelling a monomer together with a radical polymerization initiator using non-crosslinked seed particles.

  In the case where the substrate particles are inorganic particles or organic-inorganic hybrid particles excluding metal particles, examples of the inorganic material for forming the substrate particles include silica, alumina, barium titanate, zirconia, and carbon black. . The particles formed by the silica are not particularly limited. For example, after forming a crosslinked polymer particle by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups, firing may be performed as necessary. The particle | grains obtained by performing are mentioned. Examples of the organic / inorganic hybrid particles include organic / inorganic hybrid particles formed of a crosslinked alkoxysilyl polymer and an acrylic resin.

  The organic-inorganic hybrid particles are preferably core-shell type organic-inorganic hybrid particles having a core and a shell disposed on the surface of the core. The core is preferably an organic core. The shell is preferably an inorganic shell.

  Examples of the material for forming the organic core include the resin for forming the resin particles described above.

  Examples of the material for forming the inorganic shell include inorganic substances for forming the above-described base material particles. This inorganic substance is preferably not a metal. The material for forming the inorganic shell is preferably silica. The inorganic shell is preferably formed on the surface of the core by forming a metal alkoxide into a shell-like material by a sol-gel method and then firing the shell-like material. The metal alkoxide is preferably a silane alkoxide.

  As a specific method of the sol-gel method, an interfacial sol reaction is performed by coexisting an inorganic monomer such as tetraethoxysilane in a dispersion containing a core, a solvent such as water or alcohol, a surfactant, and a catalyst such as an aqueous ammonia solution. And a method in which a sol-gel reaction is performed with an inorganic monomer such as tetraethoxysilane coexisting with a solvent such as water or alcohol and an aqueous ammonia solution, and then the sol-gel reaction product is heteroaggregated in the core. In the sol-gel method, the metal alkoxide is preferably hydrolyzed and polycondensed.

  The particle size of the core is preferably 0.5 μm or more, more preferably 1 μm or more, preferably 500 μm or less, more preferably 100 μm or less, still more preferably 50 μm or less, particularly preferably 20 μm or less, and most preferably 10 μm or less. . When the particle size of the core is not less than the above lower limit and not more than the above upper limit, more suitable conductive particles can be obtained by electrical connection between the electrodes, and the base particles can be suitably used for the use of conductive particles. Become. For example, when the core particle size is not less than the lower limit and not more than the upper limit, when the electrodes are connected using the conductive particles, the contact area between the conductive particles and the electrodes is sufficiently large, and Aggregated conductive particles are hardly formed when the conductive layer is formed. Further, the distance between the electrodes connected via the conductive particles does not become too large, and the conductive layer is difficult to peel from the surface of the base material particles.

  The particle diameter of the core means a diameter when the core is a true sphere, and when the core is a shape other than a true sphere, means a diameter when assuming a true sphere corresponding to the volume. To do. Moreover, the particle size of a core means the average particle size which measured the core with the arbitrary particle size measuring apparatus. For example, a particle size distribution measuring machine using principles such as laser light scattering, electrical resistance value change, and image analysis after imaging can be used.

  The thickness of the shell is preferably 100 nm or more, more preferably 200 nm or more, preferably 5 μm or less, more preferably 3 μm or less. When the thickness of the shell is not less than the above lower limit and not more than the above upper limit, conductive particles more suitable for electrical connection between the electrodes can be obtained, and the base particles can be suitably used for the use of conductive particles. . The thickness of the shell is an average thickness per base particle. The thickness of the shell can be controlled by controlling the sol-gel method.

  When the substrate particles are metal particles, examples of the metal for forming the metal particles include silver, copper, nickel, silicon, gold, and titanium. However, the substrate particles are preferably not metal particles.

  The particle diameter of the substrate particles is particularly preferably 0.1 μm or more and 5 μm or less. When the particle diameter of the substrate particles is in the range of 0.1 to 5 μm, even when the distance between the electrodes is small and the thickness of the conductive layer is increased, small conductive particles can be obtained. From the viewpoint of obtaining even smaller conductive particles even when the distance between the electrodes is further reduced or the conductive layer is thickened, the average particle diameter of the base particles is preferably 0.5 μm. Above, more preferably 2 μm or more, preferably 3 μm or less. The particle diameter of the base particle indicates a diameter when the base particle is a true sphere, and indicates a maximum diameter when the base particle is not a true sphere.

[Conductive layer]
The conductive layer has a palladium layer on the outer surface side. The conductive layer may include a conductive layer (first conductive layer) other than the palladium layer and a palladium layer (second conductive layer).

  The metal for forming the conductive layer other than the palladium layer is not particularly limited. Examples of the metal include gold, silver, copper, platinum, zinc, iron, tin, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, thallium, germanium, cadmium, silicon, tungsten, and molybdenum. , Tin-doped indium oxide (ITO) and solder. In the conductive layer, these metals may be alloys. Especially, since the connection resistance between electrodes can be made still lower, an alloy containing tin, nickel, copper or gold is preferable, nickel or copper is more preferable, and nickel is more preferable.

  The method for forming the conductive layer other than the palladium layer is not particularly limited. Examples of a method for forming a conductive layer other than the palladium layer include a method using electroless plating, a method using electroplating, a method using physical vapor deposition, and a paste containing metal powder or metal powder and a binder. For example, a method of coating the surface. Especially, since formation of electroconductive layers other than the said palladium layer is simple, the method by electroless plating is preferable. Examples of the method by physical vapor deposition include methods such as vacuum vapor deposition, ion plating, and ion sputtering.

  The method for forming the palladium layer is not particularly limited as long as the content of palladium in 100% by weight of the palladium layer can be 99.9% by weight or more. Examples of the method for forming the palladium layer include a barrel sputtering method and an ion plating method. The palladium layer is preferably formed by a barrel sputtering method, and is preferably formed by a barrel sputtering method so that the content of palladium is not less than the above lower limit.

As preferable conditions of the barrel sputtering method, the degree of vacuum is 1 × 10 ⁻³ Torr or less, the Ar flow rate is 5 ccm or less, the sputtering output is 10 W / cm ² or more, the barrel rotation speed is 1 to 10 rpm, and the temperature of the base particle is: Conditions of 100 ° C. or higher are preferable.

  In particular, when the palladium layer is formed by electroless plating, it may be necessary to add a large amount of catalyst to the surface of the particles before forming the palladium layer. Therefore, when the palladium layer is formed by the electroless plating method, the palladium content in the palladium layer is generally less than 99.9% by weight and not 99.9% by weight or more. Moreover, when a palladium layer is formed by an electroless plating method, a lot of catalyst residues are easily contained in the palladium layer.

  In the region having a thickness of 5 nm from the inner surface of the palladium layer (the surface on the substrate particle side) toward the outside in the thickness direction, the palladium layer does not contain any component other than palladium, or the palladium layer is other than palladium. The content of components other than palladium, including the components and contained in the palladium layer, is preferably 50 ppm or less. In this case, examples of the component other than palladium include a catalyst residue. Examples of components other than palladium include sulfur, chlorine, and tin.

  The thickness of the conductive layer (when the conductive layer is a multilayer, the total thickness of the conductive layer) is preferably 5 nm or more, more preferably 10 nm or more, still more preferably 20 nm or more, particularly preferably 50 nm or more, preferably 1000 nm. Below, more preferably 800 nm or less, still more preferably 500 nm or less, particularly preferably 400 nm or less, and most preferably 300 nm or less. The thickness of the palladium layer is preferably 5 nm or more, more preferably 10 nm or more, still more preferably 20 nm or more, particularly preferably 50 nm or more, preferably 1000 nm or less, more preferably 800 nm or less, still more preferably 500 nm or less, particularly preferably 400 nm or less, most preferably 300 nm or less. When the thickness of the conductive layer and the palladium layer is equal to or greater than the lower limit, the conductivity of the conductive particles is further improved. When the thickness of the conductive layer and the palladium layer is not more than the above upper limit, the difference in thermal expansion coefficient between the base particle and the conductive layer becomes small, and the conductive layer and the palladium layer are difficult to peel from the base particle.

  The thickness of the palladium layer may be less than 20 nm. By adopting the above-described configuration in the present invention, even when the thickness of the palladium layer is less than 20 nm, the conduction reliability between the electrodes can be sufficiently enhanced. When the thickness of the palladium layer is thin, the amount of palladium used is reduced and the environmental load can be reduced.

  The particle diameter of the conductive particles is preferably 0.5 μm or more, more preferably 1 μm or more, preferably 100 μm or less, more preferably 20 μm or less, and even more preferably 5 μm or less. When the particle diameter of the conductive particles is not less than the above lower limit and not more than the above upper limit, the contact area between the conductive particles and the electrodes is sufficiently large when the electrodes are connected using the conductive particles, and the conductive layer When forming the conductive particles, it becomes difficult to form aggregated conductive particles. Further, the distance between the electrodes connected via the conductive particles does not become too large, and the conductive layer is difficult to peel from the surface of the base material particles.

  The particle diameter of the conductive particles indicates the diameter when the conductive particles are true spherical, and indicates the maximum diameter when the conductive particles are not true spherical.

  The conductive particles according to the present invention preferably have protrusions on the conductive surface. The conductive layer preferably has a protrusion on the outer surface. The palladium layer preferably has a protrusion on the outer surface. An oxide film is often formed on the surface of the electrode connected by the conductive particles. Furthermore, an oxide film is often formed on the surface of the conductive layer of the conductive particles. By using conductive particles having conductive protrusions, the oxide particles are effectively eliminated by the protrusions by placing the conductive particles between the electrodes and then pressing them. For this reason, an electrode and electroconductive particle can be contacted still more reliably and the connection resistance between electrodes can be made low. Further, when the conductive particles have an insulating material on the surface, or when the conductive particles are dispersed in the resin and used as a conductive material, the conductive particles and the electrodes are insulated by the protrusions of the conductive particles. Substances or resins can be effectively excluded. For this reason, the conduction | electrical_connection reliability between electrodes can be improved.

  It is preferable that there are a plurality of protrusions. The number of protrusions on the outer surface of the conductive layer per one conductive particle is preferably 3 or more, more preferably 5 or more. The upper limit of the number of protrusions is not particularly limited. The upper limit of the number of protrusions can be appropriately selected in consideration of the particle diameter of the conductive particles.

  The average height of the plurality of protrusions is preferably 0.001 μm or more, more preferably 0.05 μm or more, preferably 0.9 μm or less, more preferably 0.2 μm or less. When the average height of the protrusions is not less than the above lower limit and not more than the above upper limit, the connection resistance between the electrodes is effectively reduced.

[Core material]
Since the core substance is embedded in the conductive layer, it is easy for the conductive layer to have a plurality of protrusions on the outer surface. However, in order to form protrusions on the surfaces of the conductive particles and the conductive layer, the core substance is not necessarily used.

  As the method for forming the protrusions, a core material is attached to the surface of the base particle, and then a conductive layer is formed by barrel sputtering, and a conductive layer is formed by barrel sputtering on the surface of the base particle. Thereafter, a method of attaching a core substance and further forming a conductive layer by barrel sputtering may be used.

  As a method of disposing the core substance on the surface of the base particle, for example, the core substance is added to the dispersion of the base particle, and the core substance is applied to the surface of the base particle, for example, van der Waals force. And a method of attaching the core material to the surface of the base material particles by adding a core material to the container containing the base material particles and mechanically acting by rotating the container, etc. Is mentioned. Especially, since the quantity of the core substance to adhere is easy to control, the method of accumulating a core substance on the surface of the base particle in a dispersion liquid, and making it adhere by drying is preferable.

  Examples of the material constituting the core material include conductive materials and non-conductive materials. Examples of the conductive material include conductive non-metals such as metals, metal oxides, and graphite, and conductive polymers. Examples of the conductive polymer include polyacetylene. Examples of the non-conductive substance include silica, alumina, barium titanate, zirconia, and the like. Among them, metal is preferable because conductivity can be increased and connection resistance can be effectively reduced. The core substance is preferably metal particles.

  Examples of the metal include gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium and cadmium, and tin-lead. Examples include alloys composed of two or more metals such as alloys, tin-copper alloys, tin-silver alloys, tin-lead-silver alloys, and tungsten carbide. Of these, nickel, copper, silver or gold is preferable. The metal for forming the core material may be the same as or different from the metal for forming the conductive layer. The metal for forming the core substance preferably includes a metal for forming the conductive layer. The metal for forming the core substance preferably contains nickel. The metal for forming the core substance preferably contains nickel.

  The shape of the core material is not particularly limited. The shape of the core substance is preferably a lump. Examples of the core substance include a particulate lump, an agglomerate in which a plurality of fine particles are aggregated, and an irregular lump.

  The average diameter (average particle diameter) of the core substance is preferably 0.001 μm or more, more preferably 0.05 μm or more, preferably 0.9 μm or less, more preferably 0.2 μm or less. When the average diameter of the core substance is not less than the above lower limit and not more than the above upper limit, the connection resistance between the electrodes can be effectively reduced.

  The “average diameter (average particle diameter)” of the core substance indicates a number average diameter (number average particle diameter). The average diameter of the core material is obtained by observing 50 arbitrary core materials with an electron microscope or an optical microscope and calculating an average value.

[Insulating material]
The conductive particles according to the present invention preferably include an insulating substance disposed on the outer surface of the conductive layer. The insulating material is preferably disposed on the outer surface of the palladium layer. In this case, when the conductive particles are used for connection between the electrodes, a short circuit between adjacent electrodes can be prevented. Specifically, when a plurality of conductive particles are in contact with each other, an insulating material is present between the plurality of electrodes, so that it is possible to prevent a short circuit between electrodes adjacent in the lateral direction instead of between the upper and lower electrodes. Note that when the conductive particles are pressurized with the two electrodes at the time of connection between the electrodes, the insulating substance between the conductive layer of the conductive particles and the electrodes can be easily excluded. When the conductive particles have a plurality of protrusions on the outer surface of the conductive layer, the insulating material between the conductive layer of the conductive particles and the electrode can be easily excluded.

  It is preferable that the insulating material is an insulating particle because the insulating material can be more easily removed when the electrodes are pressed.

  Specific examples of the insulating resin that is the material of the insulating material include polyolefins, (meth) acrylate polymers, (meth) acrylate copolymers, block polymers, thermoplastic resins, crosslinked thermoplastic resins, and thermosetting. Resin, water-soluble resin, and the like.

  Examples of the polyolefins include polyethylene, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid ester copolymer. Examples of the (meth) acrylate polymer include polymethyl (meth) acrylate, polyethyl (meth) acrylate, and polybutyl (meth) acrylate. Examples of the block polymer include polystyrene, styrene-acrylic acid ester copolymer, SB type styrene-butadiene block copolymer, SBS type styrene-butadiene block copolymer, and hydrogenated products thereof. Examples of the thermoplastic resin include vinyl polymers and vinyl copolymers. As said thermosetting resin, an epoxy resin, a phenol resin, a melamine resin, etc. are mentioned. Examples of the water-soluble resin include polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyvinyl pyrrolidone, polyethylene oxide, and methyl cellulose. Of these, water-soluble resins are preferable, and polyvinyl alcohol is more preferable.

  Examples of a method for disposing an insulating material on the surface of the conductive layer include a chemical method and a physical or mechanical method. Examples of the chemical method include an interfacial polymerization method, a suspension polymerization method in the presence of particles, and an emulsion polymerization method. Examples of the physical or mechanical method include spray drying, hybridization, electrostatic adhesion, spraying, dipping, and vacuum deposition. In particular, since the insulating substance is difficult to be detached, a method of disposing the insulating substance on the surface of the conductive layer through a chemical bond is preferable.

  The average diameter (average particle diameter) of the insulating material can be appropriately selected depending on the particle diameter of the conductive particles, the use of the conductive particles, and the like. The average diameter (average particle diameter) of the insulating material is preferably 0.005 μm or more, more preferably 0.01 μm or more, preferably 1 μm or less, more preferably 0.5 μm or less. When the average diameter of the insulating material is not less than the above lower limit, the conductive layers of the plurality of conductive particles are difficult to contact when the conductive particles are dispersed in the binder resin. When the average diameter of the insulating particles is not more than the above upper limit, it is not necessary to make the pressure too high in order to eliminate the insulating material between the electrodes and the conductive particles when the electrodes are connected. There is no need for heating.

  The “average diameter (average particle diameter)” of the insulating material indicates a number average diameter (number average particle diameter). The average diameter of the insulating material is obtained using a particle size distribution measuring device or the like.

[Rust prevention treatment]
From the viewpoint of suppressing the corrosion of the conductive particles and further reducing the connection resistance between the electrodes, the outer surface of the conductive layer is preferably treated with rust, and the outer surface of the palladium layer is treated with rust. It is preferable.

  From the viewpoint of further improving the conduction reliability, the outer surface of the palladium layer is preferably subjected to a rust prevention treatment with a compound having an alkyl group having 6 to 22 carbon atoms. From the viewpoint of further improving the conduction reliability, the outer surface of the palladium layer is preferably rust-proofed with an alkyl phosphate compound or an alkyl thiol. By the rust prevention treatment, a rust prevention film can be formed on the surface of the palladium layer.

  The rust preventive film is preferably formed of a compound having an alkyl group having 6 to 22 carbon atoms (hereinafter also referred to as compound A). The outer surface of the palladium layer is preferably surface-treated with the compound A. When the carbon number of the alkyl group is 6 or more, rust is more unlikely to occur on the outer surface of the copper layer. When the carbon number of the alkyl group is 22 or less, the conductivity of the conductive particles is increased. From the viewpoint of further improving the conductivity of the conductive particles, the alkyl group in the compound A preferably has 16 or less carbon atoms. The alkyl group may have a linear structure or a branched structure. The alkyl group preferably has a linear structure.

  The compound A is not particularly limited as long as it has an alkyl group having 6 to 22 carbon atoms. The compound A has a phosphate ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof, a phosphite ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof, and an alkyl group having 6 to 22 carbon atoms. It is preferably at least one selected from the group consisting of alkoxysilanes, alkylthiols having an alkyl group having 6 to 22 carbon atoms, and dialkyl disulfides having an alkyl group having 6 to 22 carbon atoms. That is, the compound A having an alkyl group having 6 to 22 carbon atoms is at least one selected from the group consisting of phosphate esters or salts thereof, phosphite esters or salts thereof, alkoxysilanes, alkylthiols, and dialkyl disulfides. It is preferable that By using these preferable compounds A, it is possible to further prevent rust from being generated in the palladium layer. From the viewpoint of making rust even more difficult to generate, the compound A is preferably the phosphate ester or salt thereof, phosphite ester or salt thereof, or alkylthiol, and the phosphate ester or salt thereof, Or it is more preferable that it is a phosphite ester or its salt. As for the said compound A, only 1 type may be used and 2 or more types may be used together.

  The compound A preferably has a reactive functional group capable of reacting with the outer surface of the copper layer. The compound A preferably has a reactive functional group capable of reacting with the insulating substance. The rust preventive film is preferably chemically bonded to the palladium layer. The rust preventive film is preferably chemically bonded to the insulating substance. More preferably, the rust preventive film is chemically bonded to both the palladium layer and the insulating material. Due to the presence of the reactive functional group and the chemical bond, the rust preventive film is less likely to be peeled off. As a result, the palladium layer is more unlikely to rust, and the insulating material is exposed from the surface of the conductive particles. It becomes more difficult to detach unintentionally.

  Examples of the phosphoric acid ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof include, for example, phosphoric acid hexyl ester, phosphoric acid heptyl ester, phosphoric acid monooctyl ester, phosphoric acid monononyl ester, phosphoric acid monodecyl ester, Monoundecyl phosphate, monododecyl phosphate, monotridecyl phosphate, monotetradecyl phosphate, monopentadecyl phosphate, monohexyl phosphate monosodium salt, monoheptyl phosphate monosodium Salts, monooctyl phosphate monosodium salt, monononyl phosphate monosodium salt, monodecyl phosphate monosodium salt, monoundecyl phosphate monosodium salt, monododecyl phosphate monosodium salt, Phosphate mono tridecyl ester monosodium salt, phosphate acid mono tetradecyl ester monosodium salt and phosphoric acid mono pentadecyl ester monosodium salt. You may use the potassium salt of the said phosphate ester.

  Examples of the phosphite ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof include, for example, hexyl phosphite ester, heptyl phosphite ester, monooctyl phosphite ester, monononyl phosphite ester, Phosphoric acid monodecyl ester, phosphorous acid monoundecyl ester, phosphorous acid monododecyl ester, phosphorous acid monotridecyl ester, phosphorous acid monotetradecyl ester, phosphorous acid monopentadecyl ester, phosphorous acid monohexyl Ester monosodium salt, phosphorous acid monoheptyl ester monosodium salt, phosphorous acid monooctyl ester monosodium salt, phosphorous acid monononyl ester monosodium salt, phosphorous acid monodecyl ester monosodium salt, phosphorous acid monoun Decyl ester monosodium salt, phosphorous acid Dodecyl ester monosodium salt, phosphorous acid mono-tridecyl ester monosodium salt, phosphorous acid mono-tetradecyl ester monosodium salt and phosphorous acid mono-pentadecyl ester monosodium salt. You may use the potassium salt of the said phosphite.

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

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

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

(Conductive material)
The conductive material according to the present invention includes the conductive particles described above and a binder resin. The conductive particles are preferably dispersed in a binder resin and used as a conductive material. The conductive material is preferably an anisotropic conductive material. The conductive material is preferably used for electrical connection of electrodes. The conductive material is preferably a circuit connection material.

  The binder resin is not particularly limited. As the binder resin, a known insulating resin is used.

  Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, and elastomers. As for the said binder resin, only 1 type may be used and 2 or more types may be used together.

  Examples of the vinyl resin include vinyl acetate resin, acrylic resin, and styrene resin. Examples of the thermoplastic resin include polyolefin resins, ethylene-vinyl acetate copolymers, and polyamide resins. Examples of the curable resin include an epoxy resin, a urethane resin, a polyimide resin, and an unsaturated polyester resin. 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. Examples of the thermoplastic block copolymer include a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a hydrogenated product of a styrene-butadiene-styrene block copolymer, and a styrene-isoprene. -Hydrogenated product of a styrene block copolymer. Examples of the elastomer include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.

  In addition to the conductive particles and the binder resin, the conductive material includes, for example, a filler, an extender, a softener, a plasticizer, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, a heat stabilizer, and a light stabilizer. Various additives such as an agent, an ultraviolet absorber, a lubricant, an antistatic agent and a flame retardant may be contained.

  The conductive material according to the present invention can be used as a conductive paste and a conductive film. When the conductive material according to the present invention is a conductive film, a film that does not include conductive particles may be laminated on a conductive film that includes conductive particles. The conductive paste is preferably an anisotropic conductive paste. The conductive film is preferably an anisotropic conductive film.

  In 100% by weight of the conductive material, the content of the binder resin is preferably 10% by weight or more, more preferably 30% by weight or more, still more preferably 50% by weight or more, particularly preferably 70% by weight or more, preferably 99.% or more. It is 99 weight% or less, More preferably, it is 99.9 weight% or less. When the content of the binder resin is not less than the above lower limit and not more than the above upper limit, the conductive particles are efficiently arranged between the electrodes, and the connection reliability of the connection target member connected by the conductive material is further increased.

  In 100% by weight of the conductive material, the content of the conductive particles is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, preferably 40% by weight or less, more preferably 20% by weight or less, More preferably, it is 10 weight% or less. When the content of the conductive particles is not less than the above lower limit and not more than the above upper limit, the conduction reliability between the electrodes is further enhanced.

(Connection structure)
A connection structure can be obtained by connecting the connection object members using the conductive particles or using a conductive material containing the conductive particles and a binder resin.

  The connection structure includes a first connection target member, a second connection target member, and a connection portion connecting the first and second connection target members, and the connection portion has the above-described conductivity. The connection structure is preferably formed of particles or formed of a conductive material containing the above-described conductive particles and a binder resin. In the case where conductive particles are used, the connection portion itself is conductive particles. That is, the first and second connection target members are connected by the conductive particles.

  In FIG. 4, the connection structure using the electroconductive particle which concerns on the 1st Embodiment of this invention is typically shown with sectional drawing.

  4 includes a first connection target member 52, a second connection target member 53, and a connection portion 54 that connects the first and second connection target members 52 and 53. Prepare. The connection portion 54 is formed by curing a conductive material including the conductive particles 1. In FIG. 4, the conductive particles 1 are schematically shown for convenience of illustration. Instead of the conductive particles 1, conductive particles 11, 21, etc. may be used.

  The first connection target member 52 has a plurality of first electrodes 52a on the surface (upper surface). The second connection target member 53 has a plurality of second electrodes 53a on the surface (lower surface). The first electrode 52 a and the second electrode 53 a are electrically connected by one or a plurality of conductive particles 1. Therefore, the first and second connection target members 52 and 53 are electrically connected by the conductive particles 1.

The manufacturing method of the connection structure is not particularly limited. As an example of a method for manufacturing a connection structure, the conductive material is disposed between a first connection target member and a second connection target member to obtain a laminate, and then the laminate is heated and pressurized. Methods and the like. The pressure of the pressurization is about 9.8 × 10 ^{4 to} 4.9 × 10 ⁶ Pa. The temperature of the said heating is about 120-220 degreeC.

  Specific examples of the connection target member include electronic components such as semiconductor chips, capacitors, and diodes, and electronic components such as printed boards, flexible printed boards, glass epoxy boards, and glass boards. The connection target member is preferably an electronic component. The conductive particles are preferably used for electrical connection of electrodes in an electronic component.

  Examples of the electrode provided on the connection target member include metal electrodes such as a gold electrode, a nickel electrode, a tin electrode, an aluminum electrode, a copper electrode, a silver electrode, a molybdenum electrode, and a tungsten electrode. When the connection object member is a flexible printed board, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, or a copper electrode. When the connection target member is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, or a tungsten electrode. In addition, when the said electrode is an aluminum electrode, the electrode formed only with aluminum may be sufficient and the electrode by which the aluminum layer was laminated | stacked on the surface of the metal oxide layer may be sufficient. Examples of the material for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal element include Sn, Al, and Ga.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited only to the following examples.

Example 1
The surface of divinylbenzene copolymer resin particles (“Micropearl SP-203” manufactured by Sekisui Chemical Co., Ltd.) having a particle diameter of 3.0 μm was coated with an inorganic shell (thickness 250 nm) using a condensation reaction by sol-gel reaction. Core-shell type organic-inorganic hybrid particles (base material particles) were prepared.

A palladium layer (thickness 20 nm) was formed on the surface of the substrate particles by barrel sputtering using the organic-inorganic hybrid particles as the substrate particles. The conditions of barrel sputtering were set to a degree of vacuum: 5 × 10 ⁻⁴ Torr or less, an Ar flow rate: 3 ccm or less, a sputtering output: 50 W / cm ² or more, a barrel rotation speed: 6 rpm, and a base particle temperature: 150 ° C. Then, electroconductive particle was obtained by carrying out an antirust process using the compound which has a C6-C22 alkyl group.

(Example 2)
Divinylbenzene copolymer resin particles having a particle size of 3.0 μm (“Micropearl SP-203” manufactured by Sekisui Chemical Co., Ltd.) were prepared.

  Conductive particles were obtained in the same manner as in Example 1 except that the base particles were changed to the resin particles.

Example 3
When forming the palladium layer, conductive particles were obtained in the same manner as in Example 1 except that the thickness of the palladium layer was changed to 5 nm.

Example 4
The organic-inorganic hybrid particles obtained in Example 1 were prepared. The organic / inorganic hybrid particles were etched and washed with water. Next, the obtained organic-inorganic hybrid particles and a dispersion containing the dispersant are mixed with a highly dispersible nickel nanopaste containing nickel nanoparticles having an average particle size of 50 to 200 nm, and the organic-inorganic hybrid is mixed. Nickel nanoparticles were attached to the surface of the particles by heteroaggregation. Next, after solid-liquid separation, vacuum drying was performed at 50 ° C. for 5 hours to obtain organic-inorganic hybrid particles to which a core substance was adhered.

  Conductive particles were obtained in the same manner as in Example 1 except that the base particles were changed to organic-inorganic hybrid particles to which the core substance was attached.

(Example 5)
To a 1000 mL separable flask equipped with a four-neck separable cover, stirring blade, three-way cock, condenser and temperature probe, 100 mmol of methyl methacrylate and N, N, N-trimethyl-N-2-methacryloyloxyethyl A monomer composition containing 1 mmol of ammonium chloride and 1 mmol of 2,2′-azobis (2-amidinopropane) dihydrochloride was weighed in ion-exchanged water so that the solid content was 5% by weight, and then at 200 rpm. The mixture was stirred and polymerized at 70 ° C. for 24 hours under a nitrogen atmosphere. After completion of the reaction, it was freeze-dried to obtain insulating particles having an ammonium group on the surface, an average particle size of 220 nm, and a CV value of 10%.

  The insulating particles were dispersed in ion exchange water under ultrasonic irradiation to obtain a 10 wt% aqueous dispersion of insulating particles.

  10 g of the conductive particles obtained in Example 4 were dispersed in 500 mL of ion exchange water, 4 g of an aqueous dispersion of insulating particles was added, and the mixture was stirred at room temperature for 6 hours. After filtration through a 3 μm mesh filter, the particles were further washed with methanol and dried to obtain conductive particles having insulating particles attached thereto.

  When observed with a scanning electron microscope (SEM), only one coating layer of insulating particles was formed on the surface of the conductive particles. The coverage of the insulating particles with respect to the area of 2.5 μm from the center of the conductive particles by image analysis (that is, the projected area of the particle diameter of the insulating particles) was calculated to be 30%.

(Comparative Example 1)
Alkaline degreasing was performed on 3 g of divinylbenzene copolymer resin particles (“Micropearl SP-203” manufactured by Sekisui Chemical Co., Ltd.) having a particle size of 3.0 μm, and then neutralized with an acid. The resin particles were added to 100 mL of the cationic polymer solution adjusted to pH 6.0, and stirred at 60 ° C. for 1 hour. Thereafter, the mixture was filtered through a membrane filter having a diameter of 3 μm (manufactured by Millipore) and washed with water. The resin particles after washing with water were added to 100 mL of a palladium-catalyzed solution containing 8% by weight of a palladium catalyst (“Atotech Neneogant 834” manufactured by Atotech Japan), and the mixture was stirred at 35 ° C. for 30 minutes. Thereafter, the solution was filtered through a membrane filter (manufactured by Millipore) having a diameter of 3 μm and washed with water. Resin particles were repeatedly added to the palladium catalyst solution to give a sufficient amount of palladium catalyst to the surface of the resin particles. Next, the resin particles after washing with water were added to 3 g / L of sodium hypophosphite solution adjusted to pH 6.0 to obtain resin particles (core particles) whose surfaces were activated. Thereafter, the resin particles whose surface was activated were immersed in distilled water and ultrasonically dispersed. The above solution is filtered through a membrane filter (made by Millipore) having a diameter of 3 μm, and the resin particles whose surface is activated are applied to an electroless palladium plating solution (“Palette” made by Kojima Chemical Co., Ltd.) at 70 ° C. Immersion and electroless palladium plating were performed to form a 20 nm thick palladium layer on the surface of the resin particles. Thereafter, the mixture was filtered with a membrane filter having a diameter of 3 μm (manufactured by Millipore), and washed with water three times. After vacuum drying at 40 ° C. for 7 hours, aggregation was broken by pulverization to produce conductive particles having a palladium layer with a thickness of 20 nm on the surface of the resin particles.

(Comparative Example 2)
Preparation of Silicone Rubber Particles 500 g of methyl vinyl siloxane (viscosity 600 cP) represented by the following formula (1) and 20 g of methyl vinyl siloxane (viscosity 30 cP) represented by the following formula (2) were prepared.

  500 g of methyl vinyl siloxane (viscosity 600 cP) represented by the above formula (1) and 20 g of methyl vinyl siloxane (viscosity 30 cP) represented by the above formula (2) are put in a 1 L glass beaker, and a homomixer is used. The mixture was stirred and mixed at 2000 rpm. Thereafter, 1 g of polyoxyethylene (added mole number = 9 mol) octylphenyl ether and 150 g of water were added, and stirring was continued at 6000 rpm. As a result, phase inversion occurred and thickening was observed, but 329 g of water was added while stirring at 2000 rpm to obtain an O / W emulsion.

  Next, the obtained emulsion was transferred to a glass flask equipped with a stirrer with a vertical stirring blade, and stirred at room temperature (25 ° C.) under a toluene solution of a chloroplatinic acid-olefin complex (platinum content 0.05 weight). %) 1 g and 5 g of polyoxyethylene (added mole number = 9 mol) octylphenyl ether were added and reacted for 12 hours to obtain dispersion A.

  It was 3 micrometers when the average particle diameter of the particle | grains in the obtained dispersion liquid A was measured using the Coulter counter (made by Coulter Electronics Co., Ltd.). Further, several g of this dispersion A was air-dried to obtain elastic white rubber powder (rubber particles (1)).

  Further, 2290 g of water, 580 g of the above dispersion A, and 60 g of ammonia water (concentration: 28% by weight) are placed in a 3 L glass flask, the water temperature is set to 10 ° C., and stirring is performed with a vertical stirring blade at a blade rotation speed of 200 rpm. went. The pH of the liquid at this time was 11.2. To this liquid, 65 g of methyltrimethoxysilane was dropped over 20 minutes, and the liquid temperature was kept at 5 to 15 ° C. during the dropping, and stirring was further performed for 4 hours. Thereafter, the mixture was heated to 55 to 60 ° C. and subsequently stirred for 1 hour, and the obtained liquid was made into a cake-like product having a water content of about 30% by weight using a pressure filter. Next, the cake was dried at a temperature of 105 ° C. in a hot air circulating dryer, and the dried product was crushed by a jet mill. When the obtained particles (rubber particles (2)) were observed with an optical microscope, the particles were spherical particles. Further, when dispersed in water using a surfactant and the average particle size of the particles was measured using a Coulter counter, the average particle size of the particles was 3 μm. In addition, 88 mol% in the siloxane unit which comprises this rubber particle (2) was a dimethylsiloxane unit.

  In Comparative Example 1, the surface of the rubber powder (2) was coated with palladium. The coating with palladium was performed using an apparatus described in Japanese Patent No. 2909744.

  A schematic of this device is shown in FIG. FIG. 6 is a sectional view taken along line II-II in FIG.

  The main part of the apparatus includes a reduced pressure heat treatment chamber 1, a rotary barrel type sputtering chamber 2, a fluid jet mill 3, and a collector 4 with a powder filter. The reduced-pressure heat treatment chamber 1 is a container that is heated by electric resistance, and communicates with the main exhaust system 6 and the advanced exhaust system 7 through the filter 5. The reduced pressure heat treatment chamber 1 includes a screw feeder 9 for dropping the fine powder 8 subjected to the reduced pressure heat treatment to a conduit 10 that is fed into the rotary barrel type sputtering chamber 2, and a motor 40 that rotates the screw feeder 9. As shown in FIG. 6, the rotary barrel type sputtering chamber 2 is a rotating cylindrical body having a structure like a ball mill, and is rotated and controlled by a support roll 13, a rotary motor 14, and a belt 15. The shaft 12 is inserted into one side wall via a bearing mechanism 30 that functions as a rotating shaft, and the target 50 is held opposite to the tip. A conduit 10 communicating with the reduced pressure heat treatment chamber 1 is inserted from the opposite side wall through a similar bearing mechanism 30 that functions as a rotating shaft. The conduit 10 communicates with the inert gas inlet pipe 19 and the exhaust systems 6 and 7. The reduced pressure heat treatment chamber 1 and the fluid jet mill 3 are connected via a rotary barrel type sputtering chamber 2. Conduits 10 and 11 include valves 121 and 122, respectively. The fluid jet mill 3 includes a propeller 21 that rotates at high speed by a motor 20. The discharge side of the fluid jet mill 3 communicates with a fine powder circulation pipe 23 provided with a valve 22 and further communicates with the vacuum heat treatment chamber 1. The fine powder circulation pipe 23 communicates with the powder filter-equipped collector 4 from the lower side of the valve 22 through a branch pipe having a valve 24. This collector 4 with a powder filter is connected to an exhaust system 26 via a cylindrical filter 25.

First, 500 g of rubber particles (2) are put into the rotary barrel type sputtering chamber 2, and then the vacuum heat treatment chamber 1 is depressurized to 2 × 10 ⁻² Torr, the valve 121 is closed, the valve 122 is released, and the vacuum heating is performed. The communication between the processing chamber 1 and the sputtering chamber 2 was cut off. Thereafter, the argon gas is gradually fed from the inert gas feed pipe 19 to be conveyed to the fluid jet mill 3, and the fluid jet mill 3 is used to disperse the rubber particles (2) into primary particles. Collected in a vacuum heat treatment chamber 1. The collected fine powder was heated to 200 ° C. with a heater while reducing the pressure to 2 × 10 ⁻² Torr, and dried and degassed for 30 minutes. Next, the fine powder was transferred to the rotary barrel type sputtering chamber 2 which was previously deaerated after being replaced with argon gas. After the transfer, while rotating the rotary barrel type sputtering chamber 2 at a rotation speed of 5 rpm, using a palladium target, sputtering by a bipolar magnetron system under a reduced pressure of 2 × 10 ⁻² Torr (power 3 kW × 2, frequency) 13.56 MHz) was started. About 10% palladium by weight of the total silicone rubber particles after 1 hour of sputtering was formed by the coating. Sputtering was stopped, dispersion and reduced-pressure heat treatment were performed by the fluid jet mill 3 described above, and then transferred again to the rotary barrel type sputtering chamber 2 to perform palladium sputtering for 1 hour. This process was repeated 5 times to coat the palladium. After completion of the coating operation by sputtering, an argon gas flow containing fine powder is sent to the collector 4 with a powder filter while introducing argon gas into the rotary barrel type sputtering chamber 2 through the inert gas inlet pipe 19. A palladium-coated silicone rubber powder (conductive particles) was obtained.

(Example 6)
Conductive particles were obtained in the same manner as in Example 2 except that the resin particles were changed to resin particles having a compression modulus of 1400 N / mm ² when compressed by 10%.

(Reference Example A)
1 g of the conductive particles of Comparative Example 1 was dispersed in 1000 mL of distilled water (specific resistance 18 MΩ), placed in an autoclave equipped with a stirrer, and stirred and washed at 121 ° C. for 10 hours under a pressure of 0.1 MPa. Then, it was made to filter and dry and the electroconductive particle was obtained.

(Example 7)
In a 500 mL reaction vessel equipped with a stirrer and a thermometer, 300 g of a 0.13% by weight aqueous ammonia solution was placed. Next, 4.1 g of methyltrimethoxysilane, 19.2 g of vinyltrimethoxysilane, silicone alkoxy oligomer (“X-41-1053” manufactured by Shin-Etsu Chemical Co., Ltd., methoxy group, A mixture of 0.7 g of weight average molecular weight (about 1600) having an ethoxy group, an epoxy group and an alkyl group directly bonded to a silicon atom was slowly added. After the hydrolysis and condensation reaction proceeded with stirring, 2.4 mL of a 25 wt% aqueous ammonia solution was added, then the particles were isolated from the aqueous ammonia solution, and the resulting particles were subjected to an oxygen partial pressure of 10 ⁻¹⁷ atm, Firing at 400 ° C. for 2 hours gave organic-inorganic hybrid particles. The obtained organic / inorganic hybrid particles had a particle size of 3.5 μm.

  Conductive particles were obtained in the same manner as in Example 1 except that the substrate particles were used.

(Example 8)
Core-shell type organic-inorganic hybrid particles in which the surface of divinylbenzene copolymer resin particles (manufactured by Sekisui Chemical Co., Ltd.) having a particle size of 2.0 μm is coated with an inorganic shell (thickness: 250 nm) using a condensation reaction by a sol-gel reaction. (Base material particles) were prepared. Conductive particles were obtained in the same manner as in Example 1 except that the base particles were used.

Example 9
In a four-necked flask equipped with a cooling tube, a thermometer, and a dropping port, 804 parts by weight of ion-exchanged water, 1.2 parts by weight of 25% ammonia water, and 336.6 parts by weight of methanol are added dropwise with stirring. Hydrolysis of 3-methacryloxypropyltrimethoxysilane by adding a mixed solution of 80 parts by weight of 3-methacryloxypropyltrimethoxysilane (“KBM503” manufactured by Shin-Etsu Chemical Co., Ltd.) and 59.4 parts by weight of methanol from the mouth, A condensation reaction was performed to prepare an emulsion of polysiloxane particles having a methacryloyl group (polymerizable polysiloxane particles). Two hours after the start of the reaction, the obtained emulsion of polysiloxane particles was sampled and the particle size was measured. The particle size was 2.25 μm.

  Next, 2 parts by weight of 20% aqueous solution of polyoxyethylene styrenated ammonium sulfate ester ammonium salt (“HITENOL (registered trademark) NF-08” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as an emulsifier is dissolved in 80 parts by weight of ion-exchanged water. In this solution, 80 parts by weight of triallyl cyanurate (TAC) and 1.6 parts by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) (“W-65” manufactured by Wako Pure Chemical Industries, Ltd.) are dissolved. The resulting solution was added and emulsified and dispersed to prepare an emulsion of monomer components.

  The obtained emulsion was added to an emulsion of polymerizable polysiloxane particles and further stirred. One hour after the addition of the emulsified liquid, the mixed liquid was sampled and observed with a microscope. As a result, it was confirmed that the polymerizable polysiloxane particles absorbed the monomer and were enlarged.

  Next, 8 parts by weight of 20% aqueous solution of polyoxyethylene styrenated phenyl ether sulfate ammonium salt and 20.6 parts by weight of ion-exchanged water were added, and the reaction solution was heated to 65 ° C. in a nitrogen atmosphere. Holding for 2 hours, radical polymerization of the monomer component was performed. The emulsion after radical polymerization was subjected to solid-liquid separation, and the obtained cake was washed with ion-exchanged water and methanol, and then vacuum-dried at 120 ° C. for 2 hours to obtain base particles as polymer particles. The particle diameter of the obtained polymer particles was 3.1 μm.

  Conductive particles were obtained in the same manner as in Example 1 except that the substrate particles were used.

(Evaluation)
(1) The above-mentioned compression elastic modulus (10% K value) of the base particle
The compression elastic modulus (10% K value) of the substrate particles was measured by the above-described method using a micro compression tester (“Fischerscope H-100” manufactured by Fischer).

(2) Content of palladium in 100% by weight of palladium layer 5 g of conductive particles were added to a mixed solution of 5 mL of 60% nitric acid and 10 mL of 37% hydrochloric acid to completely dissolve the palladium layer to obtain a solution. Using the obtained solution, the content of palladium was analyzed by an ICP-MS analyzer (manufactured by Hitachi, Ltd.).

(3) Content of components other than palladium in region R having a thickness of 5 nm from the inner surface of the palladium layer (the surface on the base particle side) toward the outer side in the thickness direction Distribution of the content of each component in the thickness direction of the palladium layer Was measured. In the region R having a thickness of 5 nm from the inner surface of the palladium layer (the surface on the base particle side) to the outer side in the thickness direction, the content of components other than palladium was evaluated.

  Using a focused ion beam, a thin film slice of the obtained conductive particles was prepared. The content of components other than the palladium layer in the palladium layer was measured by an energy dispersive X-ray analyzer (EDS) using a transmission electron microscope FE-TEM (“JEM-2010FEF” manufactured by JEOL Ltd.).

(4) Conductivity reliability 10 parts by weight of bisphenol A type epoxy resin (“Epicoat 1009” manufactured by Mitsubishi Chemical Corporation), 40 parts by weight of acrylic rubber (weight average molecular weight of about 800,000), 200 parts by weight of methyl ethyl ketone, and microcapsule type 50 parts by weight of a curing agent (“HX3941HP” manufactured by Asahi Kasei Chemicals) and 2 parts by weight of a silane coupling agent (“SH6040” manufactured by Toray Dow Corning Silicone) are mixed, and the content of conductive particles is 3% by weight. It added so that it might become and disperse | distribute and the resin composition was obtained.

  The obtained resin composition was applied to a 50 μm-thick PET (polyethylene terephthalate) film whose one surface was released from the mold, and dried with hot air at 70 ° C. for 5 minutes to produce an anisotropic conductive film. The thickness of the obtained anisotropic conductive film was 12 μm.

  The obtained anisotropic conductive film was cut into a size of 5 mm × 5 mm. The cut anisotropic conductive film is formed of a glass substrate (width 3 cm, length 3 cm) having an aluminum electrode (height 0.2 μm, L / S = 20 μm / 20 μm) having a lead wire for resistance measurement on one side. Affixed almost at the center on the aluminum electrode side. Next, a two-layer flexible printed board (width 2 cm, length 1 cm) having the same aluminum electrode was bonded after being aligned so that the electrodes overlap each other. The laminated body of the glass substrate and the two-layer flexible printed circuit board was thermocompression bonded under pressure bonding conditions of 10 N, 180 ° C., and 20 seconds to obtain a connection structure. A two-layer flexible printed board in which an aluminum electrode is directly formed on a polyimide film was used. The connection resistance was measured after the obtained connection structure was left in a high-temperature and high-humidity environment at 85 ° C. and 85% and a direct current of 10 mA was applied to the connection portion for 500 hours.

Connection resistance measurement:
The connection resistance between the opposing electrodes of the obtained connection structure was measured by the 4-terminal method. Moreover, the conduction | electrical_connection reliability was determined on the following reference | standard from connection resistance.

[Evaluation criteria for conduction reliability]
○○: Connection resistance is 2.0Ω or less ○: Connection resistance exceeds 2.0Ω, 3.0Ω or less △: Connection resistance exceeds 3.0Ω, 5.0Ω or less ×: Connection resistance exceeds 5.0Ω

(5) Environmental load (cost)
When conductive particles are obtained by the procedures of Examples 1 to 9, Comparative Example 1 and Reference Example A, the environmental load is considerably reduced as compared to the case of obtaining conductive particles by the procedure of Comparative Example 2. The manufacturing cost was low.

  The results are shown in Table 1 below.

(6) Thermal shock reliability: connection resistance The obtained connection structure is left in a thermal shock tester (“TSA-72ES” manufactured by Espec Co., Ltd.) and alternately at −40 ° C., 30 minutes / 100 ° C., 30 minutes. After 1000 cycles of the connection structure under repeated conditions, the connection resistance between the opposing electrodes was measured by the 4-terminal method. From the connection resistance, the thermal shock reliability was determined according to the following criteria.

[Criteria for thermal shock reliability]
○○○: Connection resistance is 5.5Ω or less ○○: Connection resistance exceeds 5.5Ω and 6.0Ω or less ○: Connection resistance exceeds 6.0Ω and 10.0Ω or less Δ: Connection resistance is 10.0Ω Over 15.0Ω ×: Connection resistance exceeds 15.0Ω

  The results are shown in Table 2 below.

  From the results shown in Tables 1 and 2 above, even when the palladium layer has a thickness of 20 nm or less and the palladium layer is thin, the conductive particles of Examples 1 to 9 are excellent in conduction reliability and thermal shock reliability. I understand. In Examples 1 to 9, the conductive reliability evaluation results are all “◯◯”, but the conductive particles of Example 6 are more conductive than the conductive particles of Examples 1 to 5 and 7 to 9. However, the connection resistance was high. This is probably because the 10% K value of the base particles is relatively low. In Examples 1, 4 and 5, the conductive reliability evaluation results are all “◯◯”, but the conductive particles of Examples 4 and 5 are more conductive than the conductive particles of Example 1. Connection resistance was low. This is because there are protrusions on the outer surface of the conductive layer. Moreover, in the electroconductive particle of Example 5, it was difficult to connect between the electrodes which should not be connected, and it was excellent in insulation reliability. This is because an insulating material is disposed on the outer surface of the conductive layer.

DESCRIPTION OF SYMBOLS 1 ... Conductive particle 2 ... Base material particle 3 ... Conductive layer (palladium layer)
DESCRIPTION OF SYMBOLS 11 ... Conductive particle 12 ... Conductive layer 12A ... 1st conductive layer 12B ... 2nd conductive layer (palladium layer)
21 ... Conductive particles 21a ... Protrusions 22 ... Conductive layer (palladium layer)
22a ... projection 23 ... core material 24 ... insulating material 51 ... connection structure 52 ... first connection target member 52a ... first electrode 53 ... second connection target member 53a ... second electrode 54 ... connection portion

Claims (9)

Comprising base material particles and a conductive layer disposed on the surface of the base material particles,
The compression elastic modulus when compressing the substrate particles by 10% is 1000 N / mm ² or more,
The conductive layer has a palladium layer on the outer surface side,
The electroconductive particle whose content of palladium is 99.9 weight% or more in 100 weight% of said palladium layers.   The electroconductive particle of Claim 1 whose thickness of the said palladium layer is less than 20 nm.   The electroconductive particle of Claim 1 or 2 with which the said palladium layer is directly arrange | positioned on the surface of the said base material particle.   The electroconductive particle of any one of Claims 1-3 whose said base material particle is a resin particle or a core-shell type organic-inorganic hybrid particle.   The electroconductive particle of Claim 4 whose said base material particle is the said organic-inorganic hybrid particle.   The conductive particles according to claim 1, wherein the conductive layer has a plurality of protrusions on an outer surface.   The electroconductive particle of any one of Claims 1-6 provided with the insulating substance arrange | positioned on the outer surface of the said electroconductive layer.   The electroconductive material containing the electroconductive particle of any one of Claims 1-7, and binder resin. A first connection object member having a first electrode on its surface;
A second connection target member having a second electrode on its surface;
A connection portion connecting the first connection target member and the second connection target member;
The connecting portion is formed of the conductive particles according to any one of claims 1 to 7, or is formed of a conductive material including the conductive particles and a binder resin.
A connection structure in which the first electrode and the second electrode are electrically connected by the conductive particles.

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