JP6165625B2 - Conductive particles, conductive materials, and connection structures - Google Patents

Description

  The present invention relates to conductive particles that can be used, for example, for connection between electrodes, and more particularly to conductive particles having base particles and a conductive layer disposed on the surface of the base 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.

  The anisotropic conductive material is used for connection between an IC chip and a flexible printed circuit board, connection between an IC chip and a circuit board having an ITO electrode, and the like. For example, after disposing an anisotropic conductive material between the electrode of the IC chip and the electrode of the circuit board, these electrodes can be electrically connected by heating and pressing.

  As an example of the conductive particles used for the anisotropic conductive material, the following Patent Document 1 discloses base material particles, a nickel layer formed on the surface of the base material particle, and formed on the surface of the nickel layer. Disclosed is a conductive particle comprising a modified palladium layer. In this conductive particle, the phosphorus content in the nickel layer is in the range of 5 to 15% by weight, and the palladium content in the palladium layer is 96% by weight or more.

JP 2010-73578 A

  In the conductive particles described in Patent Document 1, a specific conductive layer is formed. Therefore, in the connection structure in which the electrodes are electrically connected using the conductive particles described in Patent Document 1, the connection resistance Can be lowered to some extent.

  However, in recent years, development of conductive particles that can further reduce the connection resistance has been desired.

  An object of the present invention is to provide conductive particles capable of effectively reducing connection resistance when electrodes are electrically connected, and a conductive material and a connection structure using the conductive particles. It is.

  According to a broad aspect of the present invention, base particles, a first conductive layer disposed on the surface of the base particles and containing nickel and phosphorus, and an outer surface of the first conductive layer There is provided a conductive particle, comprising: a second conductive layer disposed on top of the second conductive layer, wherein the phosphorous content in the first conductive layer is less than 3% by weight.

  On the specific situation with the electroconductive particle which concerns on this invention, content of phosphorus in the said 1st conductive layer is 0.1 to 3 weight%.

  On the specific situation with the electroconductive particle which concerns on this invention, content of phosphorus in the said 1st conductive layer is the said 2nd electroconductivity on the said base particle side in the thickness direction of the said 1st conductive layer. More than the layer side.

  On the specific situation with the electroconductive particle which concerns on this invention, this electroconductive particle has a processus | protrusion on the electroconductive surface.

  In another specific aspect of the conductive particle according to the present invention, an insulating material disposed on the outer surface of the second conductive layer is provided.

  The conductive material according to the present invention includes the conductive particles described above and a binder resin.

  The connection structure according to the present invention 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 The part is formed of the above-described conductive particles, or is formed of a conductive material containing the conductive particles and a binder resin.

  The conductive particles according to the present invention include base particles, a first conductive layer that is disposed on the surface of the base particles, and includes nickel and phosphorus, and an outer surface of the first conductive layer. And a second conductive layer containing palladium, and the phosphorous content in the first conductive layer is less than 3% by weight, so that the electrodes are electrically connected. In this case, the connection resistance can be effectively reduced.

FIG. 1 is a cross-sectional view schematically showing conductive particles according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing conductive particles according to the second embodiment of the present invention. FIG. 3 is a front cross-sectional view schematically showing a connection structure using conductive particles according to the first embodiment of the present invention. FIG. 4 is a plan view for explaining the shape of the comb-shaped electrode copper pattern on the substrate used for the evaluation of the insulation resistance of Examples, Comparative Examples, and Reference Examples.

  Hereinafter, the present invention will be described in detail.

  The conductive particles according to the present invention include base particles, a first conductive layer, and a second conductive layer. The first conductive layer is disposed on the surface of the base particle and includes nickel and phosphorus. The second conductive layer is disposed on the outer surface of the first conductive layer and contains palladium. In the conductive particles according to the present invention, the phosphorus content in the first conductive layer is less than 3% by weight.

  When the phosphorus content in the first conductive layer is less than 3% by weight, the connection resistance can be effectively reduced when the electrodes are electrically connected using conductive particles. Compared with the case where the phosphorus content in the first conductive layer is 5% by weight or more and the case where the phosphorus content in the first conductive layer is 3% by weight or more, the first conductive layer When the phosphorus content in is less than 3% by weight, the connection resistance is effectively reduced.

  In order to further reduce the connection resistance, the lower the phosphorus content in the first conductive layer, the better. The phosphorus content in the first conductive layer is less than 3% by weight, more preferably 2.9% by weight or less. The content of phosphorus in the first conductive layer may be 0.1% by weight or more, or 0.5% by weight or more.

  From the viewpoint of making it more difficult to cause cracking of the conductive layer and peeling of the conductive layer from the surface of the base material particles when a load is applied to the conductive particles, the phosphorus content in the first conductive layer is In the thickness direction of the first conductive layer, the base particle side is preferably larger than the second conductive layer side. The phosphorus in the first conductive layer is unevenly distributed in the thickness direction of the first conductive layer so that the base particle side is larger on the base particle side and the second conductive layer side. It is preferable.

  The phosphorus content in the base particle side region in the thickness direction of the first conductive layer is preferably more than 0.1% by weight, more preferably 0.5% by weight or more, and further preferably 3% by weight or more. Particularly preferably, it is 6% by weight or more, preferably 13% by weight or less, more preferably 10% by weight or less. When the content of phosphorus in the region on the base particle side is equal to or more than the above lower limit, cracking and peeling of the conductive layer are more unlikely to occur when a load is applied to the conductive particles. When the phosphorus content in the region on the base particle side is not more than the above upper limit, the connection resistance between the electrodes is further reduced. The phosphorus content in the region on the second conductive layer side in the thickness direction of the first conductive layer is preferably 3% by weight or less, more preferably less than 3% by weight, and still more preferably 1% by weight or less. is there. When the phosphorus content in the region on the second conductive layer side is not more than the above upper limit, the connection resistance between the electrodes is further reduced. In addition, it is preferable that the area | region by the side of the base particle in the said 1st conductive layer which described content of phosphorus is a 10% of area | region from the base particle side in a 1st conductive layer. The region on the second conductive layer side is preferably a region of 10% of the thickness from the second conductive layer side in the first conductive layer.

  The phosphorus content in the first conductive layer is preferably 0.5% by weight or more higher on the substrate particle side than on the second conductive layer side in the thickness direction of the first conductive layer. More preferably, it is more than 0% by weight, more preferably more than 4.0% by weight, particularly preferably more than 8.0% by weight. The absolute value of the difference between the maximum value and the minimum value of phosphorus content in the first conductive layer is preferably 0.5% by weight or more, more preferably 2.0% by weight or more, and still more preferably 4.0% by weight. % Or more, particularly preferably 8.0% by weight or more. The region on the base particle side in which the phosphorus content of the first conductive layer is relatively large is larger than the region on the second conductive layer side in which the phosphorus content of the first conductive layer is relatively small. Located inside. For this reason, the crack of a conductive layer and peeling of a conductive layer can be suppressed effectively. The region on the base particle side where the phosphorus content of the first conductive layer is relatively large is a region (region A) having a thickness of 10% from the inner surface to the outer side of the first conductive layer. preferable. The region on the second conductive layer side in which the phosphorus content of the first conductive layer is relatively small is a region (region B) having a thickness of 10% from the outer surface to the inside of the first conductive layer. It is preferable. The absolute value of the difference between the phosphorus content in region A and the phosphorus content in region B is preferably 0.5% by weight or more, more preferably 2.0% by weight or more, and still more preferably 4.0% by weight. % Or more, particularly preferably 8.0% by weight or more.

  From the viewpoint of making it more difficult to cause cracking of the conductive layer and peeling of the conductive layer from the surface of the base material particles when a load is applied to the conductive particles, the phosphorus content in the first conductive layer is In the thickness direction of the first conductive layer, it is preferable to increase continuously or stepwise from the second conductive layer side to the base particle side.

  In the connection structure using the conductive particles according to the present invention, from the viewpoint of further reducing the connection resistance between the electrodes, the higher the nickel content in the first conductive layer, the better. The content of nickel in the first conductive layer is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight or more, still more preferably 80% by weight or more, and particularly preferably 90% by weight. That's it. The nickel content in the first conductive layer may be 97% by weight or more, 97.5% by weight or more, or 98% by weight or more. The content of nickel in 100% by weight of the first conductive layer is preferably 99.85% by weight or less, more preferably 99.7% by weight or less, and still more preferably 99.5% by weight or less.

  In the present invention, the upper limit of the palladium content in the second conductive layer is not particularly limited. The palladium content in the second conductive layer may be 100% by weight, less than 99% by weight, less than 98% by weight, or less than 96% by weight. .

  In the connection structure using the conductive particles according to the present invention, the higher the content of palladium in the second conductive layer, the better from the viewpoint of further reducing the connection resistance. The palladium content in the second conductive layer is preferably 80% by weight or more, more preferably 90% by weight or more, still more preferably 96% by weight or more, particularly preferably 97% by weight or more, and most preferably 98% by weight. That's it.

  Each content of phosphorus and nickel in the first conductive layer indicates an average content in the entire first conductive layer. The content of palladium in the second conductive layer indicates the average content of palladium in the entire second conductive layer. The phosphorus content in the region A and the region B indicates the average phosphorus content in the entire region A and the entire region B.

  As a method for controlling the contents of phosphorus and nickel in the first conductive layer, for example, a method for controlling the pH of the nickel plating solution when forming the first conductive layer by electroless nickel plating, A method of controlling the concentration of the phosphorus-containing reducing agent when forming the first conductive layer by electrolytic nickel plating can be used. Further, in order to partially vary the phosphorus content in the first conductive layer, two stages of high phosphorus composition Ni plating and low phosphorus composition Ni plating via solid-liquid separation in the Ni plating step or A multi-stage plating method may be used.

  As a method of controlling the content of palladium in the second conductive layer, for example, a method of controlling the pH of a palladium plating solution when forming the second conductive layer by electroless palladium plating, and electroless palladium plating For example, a method of controlling the concentration of the reducing agent when forming the second conductive layer.

  The method for measuring the contents of nickel, phosphorus and palladium in the first and second conductive layers is not particularly limited, and various known analytical methods can be used.

  The method for measuring the contents of nickel, phosphorus and palladium in the first and second conductive layers is not particularly limited. For example, using a focused ion beam, a thin film slice of the obtained conductive particles is prepared, Examples include a method of measuring each content of nickel, phosphorus and palladium by an energy dispersive X-ray analyzer (EDS) using a transmission electron microscope FE-TEM (“JEM-2010FEF” manufactured by JEOL Ltd.). .

  Other measurement methods for the contents of nickel, phosphorus and palladium in the first and second conductive layers include absorption spectrometry or spectrum analysis. In the absorptiometry, a flame absorptiometer and an electric heating furnace absorptiometer can be used. Examples of the spectrum analysis method include a plasma emission analysis method and a plasma ion source mass spectrometry method.

  When measuring the contents of nickel, phosphorus and palladium in the first and second conductive layers, an ICP emission analyzer may be used. Examples of commercially available ICP emission analyzers include ICP emission analyzers manufactured by HORIBA.

  When measuring the contents of nickel and phosphorus in the thickness direction of the first conductive layer, it is preferable to use an FE-TEM apparatus. Examples of commercially available FE-TEM devices include “JEM-2010FEF” manufactured by JEOL Ltd.

  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 a base particle 2, a first conductive layer 3, a second conductive layer 4, a plurality of core substances 5, and a plurality of insulating substances 6. .

  The first conductive layer 3 is disposed on the surface of the base particle 2. The first conductive layer 3 covers the surface of the base particle 2. The second conductive layer 4 is disposed on the outer surface of the first conductive layer 3. The second conductive layer 4 covers the outer surface of the first conductive layer 3. The conductive particle 1 is a coated particle in which the surface of the base particle 2 is coated with the first and second conductive layers 3 and 4.

  The conductive particle 1 has a plurality of protrusions 1a on a conductive surface. The first and second conductive layers 3 and 4 have a plurality of protrusions 3a and 4a on the outer surface. A plurality of core substances 5 are arranged on the surface of the base particle 2. The plurality of core materials 5 are embedded in the first and second conductive layers 3 and 4. The plurality of core materials 5 are disposed between the base particle 2 and the first conductive layer 3 and between the base particle 2 and the second conductive layer 4. The core substance 5 is disposed inside the protrusions 1a, 3a, 4a. The first conductive layer 3 covers a plurality of core materials 5. The outer surfaces of the first and second conductive layers 3 and 4 are raised by the plurality of core materials 5 to form protrusions 1a, 3a and 4a.

  The conductive particles 1 have an insulating material 6 disposed on the outer surface of the second conductive layer 4. At least a part of the outer surface of the second conductive layer 4 is covered with an insulating material 6. The insulating substance 6 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 a 2nd conductive layer. However, the conductive particles according to the present invention do not necessarily have an insulating material.

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

  A conductive particle 11 shown in FIG. 2 includes a base particle 2, a first conductive layer 12, and a second conductive layer 13.

  The conductive particles 11 do not have a core substance. The conductive particles 11 do not have protrusions on the conductive surface. The conductive particles 11 are spherical. The first and second conductive layers 12 and 13 do not have protrusions on the surface. Thus, the electroconductive particle which concerns on this invention does not need to have an electroconductive protrusion, and may be spherical. Further, the conductive particles 11 do not have an insulating material. However, the conductive particles 11 may have an insulating material disposed on the surface of the second conductive layer 13.

  Examples of the substrate particles include resin particles, inorganic particles excluding metal particles, 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 particles, or organic-inorganic hybrid particles.

  The substrate particles are preferably resin particles formed of a resin. When connecting the electrodes, the conductive particles are generally compressed after the conductive particles are arranged between the electrodes. When the substrate particles are resin particles, the conductive particles are easily deformed by compression, and the contact area between the conductive particles and the electrode is increased. For this reason, the conduction | electrical_connection reliability between electrodes becomes high.

  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, polysulfone, 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, poly Chromatography ether ether ketone, polyether sulfone, and polymers such as obtained by a variety of polymerizable monomer having an ethylenically unsaturated group is polymerized with one or more thereof. In addition, by polymerizing one or more of various polymerizable monomers having an ethylenically unsaturated group, it is possible to design and synthesize resin particles having any compression property suitable for conductive materials. . In addition, resin particles having any compression properties suitable for conductive materials can be designed and synthesized, and the hardness of the base particles can be easily controlled within a suitable range, so that the resin particles are formed. The resin 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 the ethylenically unsaturated group may be a non-crosslinkable monomer or a crosslinkable monomer. And a polymer.

  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 di (meth) acrylate, 1,4-butanediol di (meth) acrylate; triallyl (iso) cyanurate, tria Rutorimeriteto, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, .gamma. (meth) acryloxy propyl trimethoxy silane, trimethoxy silyl styrene, include silane-containing monomers such as vinyltrimethoxysilane.

  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 polymerization 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 inorganic substances for forming the substrate particles include silica and carbon black. Although it does not specifically limit as the particle | grains formed with the said silica, For example, after hydrolyzing the silicon compound which has two or more hydrolysable alkoxysil groups, and forming a crosslinked polymer particle, it calcinates as needed. 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.

  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 average particle diameter of the substrate particles is preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 1 μm or more, still more preferably 1.5 μm or more, particularly preferably 2 μm or more, preferably 1000 μm or less. More preferably, it is 500 μm or less, more preferably 300 μm or less, still more preferably 100 μm or less, still more preferably 50 μm or less, still more preferably 30 μm or less, particularly preferably 5 μm or less, and most preferably 3 μm or less. When the average particle diameter of the base particles is equal to or more than the above lower limit, the contact area between the conductive particles and the electrodes is increased, so that the conduction reliability between the electrodes is further increased and the conductive particles are connected via the conductive particles. The connection resistance between the electrodes is further reduced. Further, when forming the conductive layer on the surface of the base particle by electroless plating, it becomes difficult to aggregate and the aggregated conductive particles are hardly formed. When the average particle diameter of the substrate particles is not more than the above upper limit, the conductive particles are easily compressed, the connection resistance between the electrodes is further reduced, and the interval between the electrodes is further narrowed.

  The average particle diameter of the substrate particles is particularly preferably 0.1 μm or more and 5 μm or less. When the average 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 average particle diameter is a number average particle diameter. The average particle diameter can be measured using, for example, a Coulter counter (manufactured by Beckman Coulter).

  The total thickness of the first conductive layer and the second conductive layer (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 it is 1000 nm or less, More preferably, it is 800 nm or less, More preferably, it is 500 nm or less, Especially preferably, it is 400 nm or less, Most preferably, it is 300 nm or less. When the thickness of the entire conductive layer is not less than the above lower limit, the conductivity of the conductive particles is further improved. When the thickness of the entire conductive layer is not more than the above upper limit, the difference in thermal expansion coefficient between the base particle and the metal layer becomes small, and the metal layer becomes difficult to peel from the base particle.

  As a method of forming the first and second conductive layers on the surface of the substrate particles, a method of forming the first and second conductive layers by electroless plating, and a first and second method by electroplating. Examples include a method of forming a conductive layer.

  The first conductive layer may contain a metal other than nickel and phosphorus as long as the object of the present invention is not impaired. The second conductive layer may contain a metal other than palladium as long as the object of the present invention is not impaired. Examples of the other metal include gold, silver, platinum, palladium, zinc, iron, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, thallium, germanium, cadmium, tungsten, molybdenum, and silicon. And tin-doped indium oxide (ITO). The first conductive layer may contain palladium. The second conductive layer may contain phosphorus.

  When the first and second conductive layers include the other metal, the content of the other metal in the first conductive layer and the content of the other metal in the second conductive layer are preferably respectively Is 20% by weight or less, more preferably 10% by weight or less, still more preferably 5% by weight or less, and particularly preferably 1% by weight or less.

  Like the electroconductive particle 1, it is preferable that the electroconductive particle which concerns on this invention has a processus | protrusion on the electroconductive surface. It is preferable that there are a plurality of protrusions. Since the core substance is embedded in the conductive layer, the conductive layer has protrusions on the outer surface. An oxide film is often formed on the surface of the electrode connected by the conductive particles. When conductive particles having protrusions are used, the oxide film is effectively eliminated by the protrusions by placing the conductive particles between the electrodes and pressing them. For this reason, an electrode and the conductive layer of electroconductive particle contact more reliably, and the connection resistance between electrodes becomes still lower. 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 (anisotropic conductive material, etc.), the conductive particles can be The resin component between the conductive particles and the electrode is effectively eliminated. For this reason, the conduction | electrical_connection reliability between electrodes becomes high.

  As a method of forming protrusions on the surface of the conductive particles, a method of forming a conductive layer by electroless plating after attaching a core substance to the surface of the base particles, and electroless plating on the surface of the base particles Examples include a method of forming a conductive layer by, attaching a core substance, and further forming a conductive layer by electroless plating. As another method for forming the protrusion, a first conductive layer is formed on the surface of the base particle, and then a core substance is disposed on the first conductive layer, and then the second conductive layer. And a method of adding a core substance in the middle of forming the conductive layer on the surface of the base particle.

  As a method of attaching the core substance to the surface of the base particle, for example, a core substance is added to the dispersion of the base particle, and the core substance is applied to the surface of the base particle by, for example, van der Waals force. Examples thereof include a method of accumulating and adhering, and a method of adding a core substance to a container containing base particles and attaching the core substance to the surface of the base particles by a mechanical action such as rotation of the container. Especially, since the quantity of the core substance to adhere is easy to control, the method of making a core substance accumulate and adhere on the surface of the base particle in a dispersion liquid 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 nonconductive material include silica, alumina, and zirconia. 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 constituting the core material may be the same as or different from the metal constituting the conductive layer. It is preferable that the metal which comprises the said core substance contains nickel. Examples of the metal oxide include alumina, silica and zirconia.

  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.

  Inorganic particles may be disposed on the surface of the core substance. It is preferable that there are a plurality of inorganic particles arranged on the surface of the core substance. Inorganic particles may be attached to the surface of the core substance. You may use the composite particle provided with such an inorganic particle and a core substance. The size (average diameter) of the inorganic particles is preferably smaller than the size (average diameter) of the core substance, and the inorganic particles are preferably inorganic fine particles.

  As the material of the inorganic particles arranged on the surface of the core substance, barium titanate (Mohs hardness 4.5), silica (silicon dioxide, Mohs hardness 6-7), zirconia (Mohs hardness 8-9), Examples include alumina (Mohs hardness 9), tungsten carbide (Mohs hardness 9), diamond (Mohs hardness 10), and the like. The inorganic particles are preferably silica, zirconia, alumina, tungsten carbide or diamond, and are also preferably silica, zirconia, alumina or diamond. The Mohs hardness of the inorganic particles is preferably 5 or more, more preferably 6 or more. The Mohs hardness of the inorganic particles is preferably larger than the Mohs hardness of the conductive layer. The Mohs hardness of the inorganic particles is preferably larger than the Mohs hardness of the second conductive layer. The absolute value of the difference between the Mohs hardness of the inorganic particles and the Mohs hardness of the conductive layer, and the absolute value of the difference between the Mohs hardness of the inorganic particles and the Mohs hardness of the second conductive layer are preferably 0.1. Above, more preferably 0.2 or more, still more preferably 0.5 or more, particularly preferably 1 or more. Further, the effect of reducing the connection resistance is more effectively exhibited when the inorganic particles are harder than all the metals constituting the first and second layers.

  The average particle size of the inorganic particles is preferably 0.0001 μm or more, more preferably 0.005 μm or more, preferably 0.5 μm or less, more preferably 0.1 μm or less. When the average particle size of the inorganic particles 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 particle diameter” of the inorganic particles indicates a number average particle diameter. The average particle diameter of the inorganic particles is obtained by observing 50 arbitrary inorganic particles with an electron microscope or an optical microscope and calculating an average value.

  When using composite particles in which inorganic particles are arranged on the surface of the core substance, the average diameter of the composite particles (average particle diameter) is preferably 0.0012 μm or more, more preferably 0.0502 μm or more, preferably Is 1.9 μm or less, more preferably 1.2 μm or less. When the average diameter of the composite particles 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 composite particles indicates a number average diameter (number average particle diameter). The average diameter of the composite particles is determined by observing 50 arbitrary composite particles with an electron microscope or an optical microscope and calculating an average value.

  Like the electroconductive particle 1, it is preferable that the electroconductive particle which concerns on this invention is equipped with the insulating substance arrange | positioned on the outer surface of the said 2nd electroconductive layer. In this case, when the conductive particles are used for connection between the electrodes, it is difficult to cause a short circuit between adjacent electrodes. 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 difficult to cause a short circuit between electrodes adjacent in the lateral direction instead of between the upper and lower electrodes. Note that the insulating material between the conductive layer of the conductive particles and the electrode can be easily eliminated by pressurizing the conductive particles with the two electrodes when connecting the electrodes. In the case where the conductive particles have protrusions on the surface of the second conductive layer, the insulating material between the conductive layer of the conductive particles and the electrode is more easily removed. The insulating material is preferably an insulating resin layer or insulating particles, and more preferably insulating particles. The insulating particles are preferably insulating resin particles.

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

  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. More preferably, the conductive particles include insulating particles attached to the surface of the conductive layer. In this case, when the conductive particles are used for the connection between the electrodes, not only the short circuit between the electrodes adjacent in the lateral direction becomes even more difficult to occur, but also the connection resistance between the connected upper and lower electrodes is further reduced. Become.

  Examples of a method for attaching insulating particles to the surface of the conductive layer include a chemical method and a physical or mechanical method. Examples of the chemical method include a method in which insulating particles are attached on the conductive layer of metal surface particles by a heteroaggregation method using van der Waals force or electrostatic force, and further chemically bonded as necessary. Examples of the physical or mechanical method include spray drying, hybridization, electrostatic adhesion, spraying, dipping, and vacuum deposition. In particular, a method of attaching an insulating material to the surface of the conductive layer through a chemical bond is preferable because the insulating material is difficult to be detached.

  The particle diameter of the insulating particles is preferably 1/5 or less of the particle diameter of the conductive particles. In this case, the particle diameter of the insulating particles is not too large, and the electrical connection by the conductive layer is more reliably achieved. When the particle size of the insulating particles is 1/5 or less of the particle size of the conductive particles, the insulating particles are efficiently deposited on the surface of the conductive particles when attaching the insulating particles by the hetero-aggregation method. Adsorption is possible. Moreover, the average diameter (average particle diameter) of the insulating substance (the insulating particles) is preferably 5 nm or more, more preferably 10 nm or more, preferably 1000 nm or less, and more preferably 500 nm or less. When the average diameter (average particle diameter) of the insulating substance (insulating particles) is equal to or greater than the lower limit, the distance between adjacent conductive particles becomes larger than the electron hopping distance, and leakage is less likely to occur. When the average diameter (average particle diameter) of the insulating substance (the insulating particles) is not more than the above upper limit, the pressure and the amount of heat required for thermocompression bonding are reduced.

  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.

  The CV value of the particle diameter of the insulating particles is preferably 20% or less. When the CV value is 20% or less, the thickness of the coating layer made of insulating particles becomes uniform, and it becomes easy to apply a uniform pressure when thermocompression bonding between electrodes, and poor conduction is less likely to occur. The CV value of the particle diameter is calculated by the following formula.

  CV value of particle diameter (%) = standard deviation of particle diameter / average particle diameter × 100

  The particle size distribution can be measured with a particle size distribution meter or the like before coating the metal surface particles, and can be measured by image analysis of an SEM photograph after coating.

  In order to expose the conductive layer of the conductive particles, the coverage with the insulating material is preferably 5% or more, and preferably 70% or less. The coverage with the insulating material is the area of the portion covered with the insulating material in the entire surface area of the conductive layer (or the metal surface particles). When the coverage is 5% or more, adjacent conductive particles are more reliably insulated by the insulating material. When the coverage is 70% or less, it is not necessary to apply heat and pressure more than necessary when the electrodes are connected, and a decrease in the performance of the binder resin due to the excluded insulating material can be suppressed.

  Although it does not specifically limit as said insulating particle, Well-known inorganic particle | grains and organic polymer particle | grains are applicable. Examples of the inorganic particles include insulating inorganic particles such as alumina, silica, and zirconia.

  The organic polymer particles are preferably resin particles obtained by (co) polymerizing one or more monomers having an unsaturated double bond. Examples of the monomer having an unsaturated double bond include (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth). Acrylate, glycidyl (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, trimethylolpropane tri (meth) acrylate, glycerol tri (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (Meth) acrylates such as (meth) acrylate and 1,4-butanediol di (meth) acrylate; vinyl ethers; vinyl chloride; styrene compounds such as styrene and divinyl benzene, acrylonitrile, and the like. That. Of these, (meth) acrylic acid esters are preferably used.

  The insulating particles preferably have a polar functional group in order to adhere to the conductive layer of the conductive particles by heteroaggregation. Examples of the polar functional group include an ammonium group, a sulfonium group, a phosphate group, and a hydroxysilyl group. The polar functional group can be introduced by copolymerizing a monomer having the polar functional group and an unsaturated double bond.

  Examples of the monomer having an ammonium group include N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropylacrylamide, and N, N, N-trimethyl-N-2-methacryloyloxyethylammonium chloride. It is done. Examples of the monomer having sulfonium include phenyldimethylsulfonium methylsulfate methacrylate. Examples of the monomer having a phosphoric acid group include acid phosphooxyethyl methacrylate, acid phosphooxypropyl methacrylate, acid phosphooxypolyoxyethylene glycol monomethacrylate, and acid phosphooxypolyoxypropylene glycol monomethacrylate. Examples of the monomer having a hydroxysilyl group include vinyltrihydroxysilane and 3-methacryloxypropyltrihydroxysilane.

  As another method for introducing a polar functional group onto the surface of the insulating particle, there is a method using a radical initiator having a polar group as an initiator when the monomer having an unsaturated double bond is polymerized. Can be mentioned. Examples of the radical initiator include 2,2′-azobis {2-methyl-N- [2- (1-hydroxy-butyl)]-propionamide}, 2,2′-azobis [2- (2- Imidazolin-2-yl) propane], 2,2′-azobis (2-amidinopropane) and salts thereof.

(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 anisotropic conductive material includes a conductive material for conducting between the upper and lower electrodes.

  The binder resin is not particularly limited. In general, an insulating resin is used as the binder resin. 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 method for dispersing the conductive particles in the binder resin is not particularly limited, and a conventionally known dispersion method can be used. Examples of a method for dispersing the conductive particles in the binder resin include a method in which the conductive particles are added to the binder resin and then kneaded and dispersed with a planetary mixer or the like. The conductive particles are dispersed in water. Alternatively, after uniformly dispersing in an organic solvent using a homogenizer or the like, it is added to the binder resin and kneaded with a planetary mixer or the like, and the binder resin is diluted with water or an organic solvent. Then, the method of adding the said electroconductive particle, kneading with a planetary mixer etc. and disperse | distributing is mentioned.

  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 not containing conductive particles may be laminated on the conductive film containing conductive particles. The conductive paste is preferably an anisotropic conductive paste. The conductive film is preferably an anisotropic conductive film.

  The conductive material is preferably a conductive paste from the viewpoint of suppressing generation of voids in the connection portion of the connection structure and further improving the conduction reliability. The conductive material is preferably a conductive paste and is a conductive material that is applied to the upper surface of the connection target member in a paste state.

  The content of the binder resin in 100% by weight of the conductive material is preferably 10% by weight or more, more preferably 30% by weight or more, still more preferably 50% by weight or more, and preferably 90.99% by weight or less. When the content of the binder resin is not less than the above lower limit and not more than the upper limit, the conductive particles are efficiently arranged between the electrodes, and the conduction reliability between the electrodes is further enhanced.

  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 80% by weight or less, more preferably 40% by weight or less. More preferably, it is 20 weight% or less, Most 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 upper limit, the conduction reliability between the electrodes is further enhanced.

(Connection structure)
A connection structure can be obtained by connecting the connection target members using the conductive particles according to the present invention, 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 part connecting the first and second connection target members, the connection part of the present invention. The connection structure is preferably formed of conductive particles or a conductive material (such as an anisotropic conductive material) containing the 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. 3, the connection structure using the electroconductive particle which concerns on the 1st Embodiment of this invention is typically shown with front sectional drawing.

  A connection structure 51 shown in FIG. 3 includes a first connection target member 52, a second connection target member 53, and a connection portion 54 connecting 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. 3, the conductive particles 1 are schematically shown for convenience of illustration. Instead of the conductive particles 1, conductive particles 11 or the like may be used.

  The first connection target member 52 has a plurality of electrodes 52b on the upper surface 52a (front surface). The second connection target member 53 has a plurality of electrodes 53b on the lower surface 53a (front surface). The electrode 52 b and the electrode 53 b 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 the manufacturing method of the connection structure, the conductive material is disposed between the first connection target member and the second connection target member to obtain a laminate, and then the laminate is heated and pressurized. Methods and the like. The pressure of the said pressurization is about 9.8 * 10 < ⁴ > -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 that are circuit boards such as printed boards, flexible printed 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 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.

  If another usage form of the electroconductive particle which concerns on this invention is given, electroconductive particle can be used as a conduction | electrical_connection material for the electrical connection between the upper-and-lower board | substrate which comprises a liquid crystal display element. Conductive particles are mixed with thermosetting resin or thermosetting resin combined with heat UV, dispersed, applied in a dot pattern on one side of the substrate, and bonded to the counter substrate, and the conductive particles are mixed with the peripheral sealant For example, there is a method in which the sealing seal and the upper and lower substrates are electrically connected to each other by applying them in a linear form. The conductive particles according to the present invention can be applied to any of such usage forms. Moreover, since the 1st, 2nd conductive layer is arrange | positioned on the surface of a base particle, the electroconductive particle which concerns on this invention does not damage a transparent substrate etc. by the outstanding elasticity of a base particle. Conductive connection is possible.

  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
(1) Electroless Nickel Plating Step Divinylbenzene resin particles (average particle size 4 μm, CV value 5%, “Micropearl SP-204” manufactured by Sekisui Chemical Co., Ltd.) were prepared. The resin particles are treated with a 10 wt% solution of an ion adsorbent for 5 minutes, then treated with an aqueous 0.01 wt% palladium sulfate solution for 5 minutes, further reduced with dimethylamine borane, and then filtered and washed. As a result, resin particles having palladium attached thereto were obtained.

  Next, a solution containing 1% by weight of sodium succinate and 500 mL of ion exchange water was prepared. To this solution, 10 g of resin particles with palladium attached were added and mixed to prepare a slurry, and sulfuric acid was further added to adjust the pH of the slurry to 5.

  An initial nickel solution 52 mL containing 10% by weight of nickel sulfate, 10% by weight of sodium hypophosphite, 4% by weight of sodium hydroxide and 20% by weight of sodium succinate was prepared. The pH 5 slurry was brought to 80 ° C., and the obtained pre-nickel solution was continuously added dropwise to the 80 ° C. slurry at 5 mL / min and stirred for 20 minutes to allow the plating reaction to proceed. During the plating reaction, it was confirmed that there was no significant aggregation and generation of hydrogen disappeared, and the plating reaction was terminated.

  Next, 100 mL of a late nickel solution containing 30% by weight of nickel sulfate, 10% by weight of sodium hypophosphite and 5% by weight of sodium hydroxide was prepared. Thereafter, the pH of the solution after completion of the plating reaction with the nickel solution was adjusted to 9.0, and the temperature of the solution was lowered from 80 ° C. to 30 ° C. for the purpose of preventing aggregation. The late nickel solution was continuously dropped into the 30 ° C. solution at 5 mL / min, and stirred for 55 minutes to cause a plating reaction. Thereafter, solid-liquid separation was performed to obtain intermediate nickel particles.

  Next, a solution containing 1% by weight of sodium succinate and 500 mL of ion exchange water was prepared. To this solution, all the intermediate nickel particles obtained by solid-liquid separation were added and mixed to prepare a slurry. Further, the pH of the slurry was adjusted to 9.0 with a sodium hydroxide solution, and the liquid temperature was maintained at 30 ° C.

  Next, 20 mL of a finished nickel solution containing 50% by weight of nickel sulfate, 5% by weight of sodium hypophosphite and 5% by weight of sodium hydroxide was prepared. Then, the finishing nickel solution was continuously dropped into the slurry solution at 30 ° C. at 5 mL / min, and the plating reaction was carried out by stirring for 5 minutes.

  In this way, particles were obtained in which a first conductive layer containing nickel and phosphorus was formed on the surface of the resin particles. The thickness of the 1st conductive layer in the obtained particle | grains was 0.1 micrometer.

(2) Electroless palladium plating step 10 g of the obtained particles were dispersed in 500 mL of ion-exchanged water using an ultrasonic processor to obtain a suspension. A plating solution having a pH of 10.0 containing 0.02 mol / L of palladium sulfate, 0.04 mol / L of ethylenediamine as a complexing agent, 0.06 mol / L of sodium formate as a reducing agent, and a crystal modifier was prepared. While stirring the obtained suspension at 50 ° C., the obtained plating solution was gradually added, and electroless palladium plating was performed to form a second conductive layer. When the thickness of the second conductive layer reached 0.04 μm, the electroless palladium plating was finished. Next, by washing and vacuum drying, conductive particles were obtained in which a second conductive layer containing palladium was formed on the outer surface of the first conductive layer containing nickel and phosphorus.

(Example 2)
(1) Electroless nickel plating step (step of forming protrusions on the surface of the first conductive layer)
1-1) Palladium adhesion step Divinylbenzene resin particles (average particle size 4 μm, CV value 5%, “Micropearl SP-204” manufactured by Sekisui Chemical Co., Ltd.) were prepared. The resin particles were etched and washed with water. Next, resin particles were added to 100 mL of a palladium-catalyzed solution containing 8% by weight of a palladium catalyst and stirred. Then, it filtered and wash | cleaned. Resin particles were added to a 0.5 wt% dimethylamine borane solution at pH 6 to obtain resin particles with palladium attached.

1-2) Core substance adhering step 10 g of resin particles to which palladium was adhered were stirred and dispersed in 300 mL of ion exchange water for 3 minutes to obtain a dispersion. Next, 1 g of metallic nickel particle slurry (“2020SUS” manufactured by Mitsui Kinzoku Co., Ltd., average particle size 200 nm) was added to the dispersion over 3 minutes to obtain resin particles to which the core substance was adhered.

1-3) Electroless nickel plating step Through the same electroless nickel plating step as in Example 1, the first conductive layer containing nickel and phosphorus is formed on the surface of the resin particles, and on the surface Particles having protrusions were obtained. The thickness of the 1st conductive layer in the obtained particle | grains was 0.1 micrometer.

(2) Electroless palladium plating step Through the electroless palladium plating step similar to that in Example 1, a second conductive layer containing palladium is formed on the outer surface of the first conductive layer containing nickel and phosphorus. Conductive particles were obtained.

(Example 3)
(1) Production of insulating particles A 1000 mL separable flask equipped with a four-neck separable cover, a stirring blade, a three-way cock, a condenser tube and a temperature probe was charged with 100 mmol methyl methacrylate and N, N, N-trimethyl. Ion exchange of a monomer composition containing 1 mmol of -N-2-methacryloyloxyethylammonium chloride and 1 mmol of 2,2'-azobis (2-amidinopropane) dihydrochloride so that the solid content is 5% by weight Added to water. Then, it stirred at 200 rpm and superposed | polymerized for 24 hours at 70 degreeC by nitrogen atmosphere. After completion of the reaction, the mixture was freeze-dried to obtain insulating particles (insulating resin particles) having an ammonium group on the surface, an average particle size of 220 nm, and a CV value of 10%.

(2) Production of conductive particles Insulating particles were dispersed in ion-exchanged water under ultrasonic irradiation to obtain a 10 wt% aqueous dispersion of insulating particles.

  10 g of the conductive particles obtained in Example 1 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%.

Example 4
Conductive particles having insulating particles attached thereto were obtained in the same manner as in Example 3, except that the conductive particles obtained in Example 1 were changed to the conductive particles obtained in Example 2. The coverage was 30%.

(Example 5)
(Electroless nickel plating process)
Divinylbenzene resin particles (average particle size 4 μm, CV value 5%, “Micropearl SP-204” manufactured by Sekisui Chemical Co., Ltd.) were prepared. The resin particles are treated with a 10 wt% solution of an ion adsorbent for 5 minutes, then treated with an aqueous 0.01 wt% palladium sulfate solution for 5 minutes, further reduced with dimethylamine borane, and then filtered and washed. As a result, resin particles having palladium attached thereto were obtained.

  Next, a solution containing 1% by weight of sodium succinate and 500 mL of ion exchange water was prepared. To this solution, 10 g of resin particles with palladium attached were added and mixed to prepare a slurry, and sulfuric acid was further added to adjust the pH of the slurry to 6.5.

  An initial nickel solution 52 mL containing 10% by weight of nickel sulfate, 10% by weight of sodium hypophosphite, 4% by weight of sodium hydroxide and 20% by weight of sodium succinate was prepared. The pH 6.5 slurry was brought to 80 ° C., and the obtained pre-nickel solution was continuously added dropwise to the 80 ° C. slurry at 5 mL / min and stirred for 20 minutes to advance the plating reaction. During the plating reaction, it was confirmed that there was no significant aggregation and generation of hydrogen disappeared, and the plating reaction was terminated.

  Next, 100 mL of a late nickel solution containing 30% by weight of nickel sulfate, 10% by weight of sodium hypophosphite and 5% by weight of sodium hydroxide was prepared. Thereafter, the pH of the solution after completion of the plating reaction with the nickel solution was adjusted to 9.0, and the temperature of the solution was lowered from 80 ° C. to 30 ° C. for the purpose of preventing aggregation. The late nickel solution was continuously dropped into the 30 ° C. solution at 5 mL / min, and stirred for 55 minutes to cause a plating reaction. Thereafter, solid-liquid separation was performed to obtain intermediate nickel particles.

  Next, a solution containing 1% by weight of sodium succinate and 500 mL of ion exchange water was prepared. To this solution, all the intermediate nickel particles obtained by solid-liquid separation were added and mixed to prepare a slurry. Further, the pH of the slurry was adjusted to 9.5 with a sodium hydroxide solution, and the liquid temperature was maintained at 30 ° C.

  Next, 20 mL of a finished nickel solution containing 60% by weight of nickel sulfate, 5% by weight of sodium hypophosphite and 5% by weight of sodium hydroxide was prepared. Thereafter, the finishing nickel solution was continuously dropped into the slurry solution at 30 ° C., and the plating reaction was carried out by stirring for 5 minutes.

  In this way, particles were obtained in which a first conductive layer containing nickel and phosphorus was formed on the surface of the resin particles. The thickness of the 1st conductive layer in the obtained particle | grains was 0.1 micrometer.

  A second conductive layer containing palladium is formed on the outer surface of the first conductive layer containing nickel and phosphorus in the same manner as in Example 2 except that the electroless nickel plating step is changed. And the electroconductive particle which has a processus | protrusion on the surface was obtained.

( Reference Example 1 )
(Electroless nickel plating process)
Nickel sulfate hexahydrate 80g / L, sodium hypophosphite monohydrate 40g / L and citric acid 60g / L, pH 8.0 nickel plating solution 600mL was prepared. 500 mL of distilled water is added to the resin particles to which the core substance is adhered, 600 mL of nickel plating solution is added at 10 mL / min, and the electroless nickel plating is performed by stirring while maintaining the pH of the suspension at 8.0. A first conductive layer was formed. During the nickel plating, the temperature of the suspension was lowered to 30 ° C. for the purpose of preventing aggregation. When the thickness of the first conductive plating layer reached 0.1 μm, the plating was finished to obtain plated particles.

  A second conductive layer containing palladium is formed on the outer surface of the first conductive layer containing nickel and phosphorus in the same manner as in Example 2 except that the electroless nickel plating step is changed. And the electroconductive particle which has a processus | protrusion on the surface was obtained.

( Reference Example 2 )
A second conductive layer containing palladium on the outer surface of the first conductive layer containing nickel and phosphorus in the same manner as in Reference Example 1 except that the pH of the electroless nickel plating step was changed to 8.8. Thus, conductive particles having protrusions on the surface were obtained.

(Example 6 )
In the electroless palladium plating step, the electroconductivity was the same as in Example 1 except that the pH of the plating solution was changed to 5.5 and the temperature of the suspension to which the plating solution was added was changed to 80 ° C. Particles were obtained.

( Reference Example 3 )
In the electroless nickel plating step, the pH of the slurry to which the initial nickel solution is added is changed to 10.5, the pH of the solution to which the latter nickel solution is added is changed to 10.5, the content of nickel sulfate in the latter nickel solution Was changed to 45% by weight, the dropping rate of the late nickel solution was changed to 10 mL / min (stirring time 27 minutes), the pH of the slurry to which the finished nickel solution was added was changed to 10.5, and the finish Conductive particles were obtained in the same manner as in Example 1 except that the dropping rate of the nickel solution was changed to 10 mL / min (stirring time: 2.5 minutes).

(Reference Example 4 )
(1) Electroless Nickel Plating Step Divinylbenzene resin particles (average particle size 4 μm, CV value 5%, “Micropearl SP-204” manufactured by Sekisui Chemical Co., Ltd.) were prepared. The resin particles were treated with a 10% by weight solution of an ion adsorbent for 5 minutes and then treated with a 0.01% by weight aqueous solution of palladium sulfate for 5 minutes. Thereafter, dimethylamine borane was added for reduction treatment, filtration, and washing to obtain resin particles having palladium attached thereto.

  Next, a 1% by weight sodium succinate solution in which sodium succinate was dissolved in 500 mL of ion exchange water was prepared. To this solution, 10 g of resin particles with palladium attached were added and mixed to prepare a slurry. The pH of the slurry was adjusted to 6.5.

  An initial nickel solution containing 10% by weight of nickel sulfate, 10% by weight of sodium hypophosphite, 4% by weight of sodium hydroxide and 20% by weight of sodium succinate was prepared. After heating the slurry adjusted to pH 6.5 to 80 ° C., the nickel solution is continuously added dropwise to the slurry at a flow rate of 5 mL / min for 10 minutes, and the plating reaction proceeds by stirring for 20 minutes. I let you. After confirming that hydrogen was no longer generated, the plating reaction was completed.

  Next, a late nickel solution containing 20% by weight of nickel sulfate, 20% by weight of sodium hypophosphite and 5% by weight of sodium hydroxide was prepared. The late nickel solution was continuously dropped at a flow rate of 10 mL / min over a period of 20 minutes to the solution after the plating reaction with the previous nickel solution, and the plating reaction was advanced by stirring. In this way, when the thickness of the first conductive layer containing nickel and phosphorus reached 0.1 μm on the surface of the resin particles, the plating reaction was terminated to obtain plated particles. The thickness of the 1st conductive layer in the obtained particle | grains was 0.1 micrometer.

(2) Electroless palladium plating step 10 g of the obtained particles were dispersed in 500 mL of ion-exchanged water using an ultrasonic processor to obtain a suspension. While stirring the suspension at 50 ° C., 0.02 mol / L of palladium sulfate, 0.04 mol / L of ethylenediamine as a complexing agent, 0.06 mol / L of sodium formate as a reducing agent, and pH 10.0 containing a crystal modifier. The plating solution was gradually added and electroless palladium plating was performed to form a second conductive layer. When the thickness of the second conductive layer reached 0.04 μm, the electroless palladium plating was finished. Next, by washing and vacuum drying, conductive particles were obtained in which a second conductive layer containing palladium was formed on the outer surface of the first conductive layer containing nickel and phosphorus.

(Reference Example 5 )
(1) Electroless Nickel Plating Step Divinylbenzene resin particles (average particle size 4 μm, CV value 5%, “Micropearl SP-204” manufactured by Sekisui Chemical Co., Ltd.) were prepared. The resin particles were treated with a 10% by weight solution of an ion adsorbent for 5 minutes and then treated with a 0.01% by weight aqueous solution of palladium sulfate for 5 minutes. Thereafter, dimethylamine borane was added for reduction treatment, filtration, and washing to obtain resin particles having palladium attached thereto.

  Next, a 1% by weight sodium succinate solution in which sodium succinate was dissolved in 500 mL of ion exchange water was prepared. To this solution, 10 g of resin particles with palladium attached were added and mixed to prepare a slurry. The pH of the slurry was adjusted to 7.5.

  An initial nickel solution containing 10% by weight of nickel sulfate, 6% by weight of sodium hypophosphite, 4% by weight of sodium hydroxide and 20% by weight of sodium succinate was prepared. After the slurry adjusted to pH 7.5 is heated to 80 ° C., the nickel solution is continuously dropped into the slurry at a flow rate of 5 mL / min over 10 minutes, and the plating reaction proceeds by stirring for 20 minutes. I let you. After confirming that hydrogen was no longer generated, the plating reaction was completed.

  Next, a late nickel solution containing 20% by weight of nickel sulfate, 20% by weight of sodium hypophosphite and 5% by weight of sodium hydroxide was prepared. The late nickel solution was continuously dropped at a flow rate of 10 mL / min for 20 minutes into the solution that had finished the plating reaction with the previous nickel solution, and the plating reaction was advanced by stirring to form a first conductive layer. When the thickness of the first conductive layer containing nickel and phosphorus reached 0.1 μm on the surface of the resin particles, the plating reaction was terminated to obtain plated particles. The thickness of the 1st conductive layer in the obtained particle | grains was 0.1 micrometer.

(2) Electroless Palladium Plating Step Similar to Reference Example 4 except that the electroless nickel plating step is changed to the above electroless nickel plating step, a second containing palladium is formed on the outer surface of the first conductive layer containing nickel and phosphorus. The electroconductive particle in which the conductive layer of this was formed was obtained.

(Reference Example 6 )
In the electroless nickel plating step, the same procedure as in Example 1 was performed except that the pH of the slurry to which the initial nickel solution was added was changed to 4.5 and the pH of the solution to which the later nickel solution was added was changed to 4.5. Conductive particles were obtained.

(Comparative Example 1)

10 g of the particles obtained in the electroless nickel plating step of Example 1 were dispersed in 500 mL of ion-exchanged water using an ultrasonic treatment machine to obtain a suspension. A plating solution having a pH of 10.0 containing 0.04 mol / L of palladium sulfate, 0.08 mol / L of ethylenediamine as a complexing agent, 0.10 mol / L of hydrazine sulfate as a reducing agent, and a crystal modifier was prepared. While stirring the obtained suspension at 50 ° C., the obtained plating solution is gradually added, electroless palladium plating is performed, and when the thickness of the conductive layer reaches 0.04 μm, electroless palladium plating is performed. By finishing, conductive particles were obtained. In Comparative Example 1, the second conductive layer was formed on the surface of the base particle without forming the first conductive layer.

(Comparative Example 2)
Conductive particles were obtained in the same manner as in Example 1 except that the electroless palladium process was not performed. In Comparative Example 2, only the first conductive layer was formed on the surface of the base particle without forming the second conductive layer.

(Comparative Example 3)
(1) Electroless nickel plating step In the same manner as in Example 1, resin particles having palladium attached thereto were obtained.

  Next, a solution containing 1% by weight of sodium succinate and 500 mL of ion exchange water was prepared. To this solution, 10 g of resin particles with palladium attached were added and mixed to prepare a slurry, and sulfuric acid was further added to adjust the pH of the slurry to 8.

  An initial nickel solution 52 mL containing 10% by weight of nickel sulfate, 15% of hydradium sulfate, 4% by weight of sodium hydroxide and 20% by weight of sodium succinate was prepared. The pH 8 slurry was brought to 80 ° C., and the obtained pre-nickel solution was continuously added dropwise to the 80 ° C. slurry at 5 mL / min and stirred for 20 minutes to advance the plating reaction. During the plating reaction, it was confirmed that there was no significant aggregation and generation of hydrogen disappeared, and the plating reaction was terminated.

  Next, 120 mL of a late nickel solution containing 45% by weight of nickel sulfate, 15% of hydradium sulfate and 5% by weight of sodium hydroxide was prepared. Thereafter, the pH of the solution after completion of the plating reaction with the nickel solution was adjusted to 9.0, and the temperature of the solution was lowered from 80 ° C. to 60 ° C. for the purpose of preventing aggregation. The late nickel solution was continuously dropped into the 30 ° C. solution at 5 mL / min, and stirred for 55 minutes to cause a plating reaction. Thereafter, solid-liquid separation was performed.

  In this way, particles in which a first conductive layer containing nickel not containing phosphorus was formed on the surface of the resin particles were obtained. The thickness of the 1st conductive layer in the obtained particle | grains was 0.1 micrometer.

  Next, electroconductive particles were obtained by performing an electroless palladium plating step in the same manner as in Example 1. In Comparative Example 3, phosphorus was not included in the first conductive layer.

(Evaluation)
(1) Respective contents of phosphorus and nickel in the first conductive layer A thin film slice of the obtained conductive particles was prepared using a focused ion beam. The section position was set at a position advanced by a distance corresponding to the radius of the conductive particles from the surface of the conductive particles toward the center of the conductive particles. Using a transmission electron microscope FE-TEM (“JEM-2010FEF” manufactured by JEOL Ltd.), each content of phosphorus and nickel in the first conductive layer was measured by an energy dispersive X-ray analyzer (EDS). . Similarly, each average content of phosphorus and nickel in the entire first conductive layer of 10 arbitrary conductive particles was measured, and an average value of 10 measured values was calculated. Further, in the thickness direction of the first conductive layer, the average content of phosphorus in the first conductive layer on the resin particle side (region A having a thickness of 10% from the inner surface to the outer side of the first conductive layer) The average content of phosphorus in the whole) and the average content of phosphorus in the first conductive layer on the second conductive layer side (region B having a thickness of 10% from the outer surface to the inside of the first conductive layer) The average content of phosphorus in the whole) was evaluated. The thickness of the first conductive layer was also evaluated by the above method.

(2) Content of Palladium and Phosphorus in Second Conductive Layer Using a focused ion beam, a thin film slice of the obtained conductive particles was prepared. The section position was set at a position advanced by a distance corresponding to the radius of the conductive particles from the surface of the conductive particles toward the center of the conductive particles. Using a transmission electron microscope FE-TEM (“JEM-2010FEF” manufactured by JEOL Ltd.), the average content of palladium and phosphorus in the second conductive layer is measured by an energy dispersive X-ray analyzer (EDS). did. Similarly, each average content of each average of palladium and phosphorus in the second conductive layer of 10 arbitrary conductive particles was measured, and an average value of 10 measured values was calculated. The thickness of the second conductive layer was also evaluated by the above method.

(3) Conduction layer corrosion test 1 (connection resistance)
Two substrates on which copper electrodes with L / S of 100 μm / 100 μm were formed were prepared. Further, anisotropy containing 10 parts by weight of the obtained conductive particles, 85 parts by weight of an epoxy resin (“Mitsui Chemical Co., Ltd.“ Struct Bond XN-5A ”) as a binder resin, and 5 parts by weight of an imidazole type curing agent A conductive paste was prepared.

  After applying the anisotropic conductive paste on the upper surface of the substrate so that the conductive particles are in contact with the copper electrode, the other substrate is laminated so that the copper electrode is in contact with the conductive particles, and is bonded to obtain a laminate. It was. Then, the anisotropic conductive paste was hardened by heating a laminated body at 180 degreeC for 1 minute, and the connection structure was obtained.

  The connection resistance between the opposing electrodes of the obtained connection structure was measured by a four-terminal method, and the obtained measurement value was taken as the initial connection resistance.

  Next, the obtained connection structure was left under high temperature and high humidity conditions of 60 ° C. and 95%. The connection resistance between the electrodes of the connection structure after being left standing was measured by the four-terminal method, and the obtained measured value was used as the connection resistance after the corrosion test.

(4) Conduction layer corrosion test 2 (insulation resistance)
As shown in FIG. 4, a substrate was prepared in which a nickel-plated layer and a gold-plated layer were sequentially formed on the surface of a copper electrode, and a comb-tooth electrode copper pattern with L / S of 20 μm / 20 μm was formed. Further, anisotropy containing 10 parts by weight of the obtained conductive particles, 85 parts by weight of an epoxy resin (“Mitsui Chemical Co., Ltd.“ Struct Bond XN-5A ”) as a binder resin, and 5 parts by weight of an imidazole type curing agent A conductive paste was prepared.

  After applying an anisotropic conductive paste on the upper surface of the copper pattern of the substrate, an alkali-free glass plate was laminated and pressure-bonded to bring the conductive particles into contact with the copper pattern. The anisotropic conductive paste was cured by heating at 180 ° C. for 1 minute in a state where the alkali-free glass plates were laminated, to obtain a connection structure.

  The insulation resistance between the adjacent electrodes of the obtained connection structure was measured by a four-terminal method, and the obtained measurement value was taken as the initial insulation resistance.

  Next, the obtained connection structure was left under conditions of 60 ° C. and high temperature and high humidity of 95%. The insulation resistance between the adjacent electrodes of the connection structure after being allowed to stand was measured by the four-terminal method, and the obtained measured value was taken as the insulation resistance after the corrosion test.

(5) Load test Using the obtained conductive particles, each material was mixed in a 300 cc glass beaker at a ratio of conductive particles 1 g: zirconia balls (diameter 1.0 mm) 45 g: toluene 17 g. A load was applied to the conductive particles under the condition of stirring at 400 rpm / 2 minutes with a stainless steel blade. Then, the presence or absence of the peeling from the surface of the crack of a conductive layer and the base material particle | grains of a conductive layer was confirmed. The load test was judged according to the following criteria.

[Criteria for load test]
○: No cracking occurred in the conductive layer, and the conductive layer was not peeled off from the surface of the base particle. Δ: Although a slight crack occurred in the conductive layer, at least a part of the conductive layer was separated from the surface of the base particle. Peeled x: Cracking occurred in the conductive layer, and at least a part of the conductive layer was peeled off from the surface of the base particle

  The results are shown in Tables 1 and 2 below.

DESCRIPTION OF SYMBOLS 1 ... Conductive particle 1a ... Protrusion 2 ... Base particle 3 ... 1st conductive layer 3a ... Protrusion 4 ... 2nd conductive layer 4a ... Protrusion 5 ... Core substance 6 ... Insulating substance 11 ... Conductive particle 12 ... 1st Conductive layer 13 ... second conductive layer 51 ... connection structure 52 ... first connection target member 52a ... upper surface 52b ... electrode 53 ... second connection target member 53a ... lower surface 53b ... electrode 54 ... connection portion

Claims (7)

Substrate particles,
A first conductive layer disposed on the surface of the substrate particles and containing nickel and phosphorus;
A second conductive layer disposed on the outer surface of the first conductive layer and containing palladium;
The first conductive layer contains phosphorus in an amount of 0.1 wt% or more and less than 3 wt%,
Conductive particles in which the content of phosphorus in the first conductive layer is greater on the base particle side than on the second conductive layer side in the thickness direction of the first conductive layer. In the thickness direction of the first conductive layer, the content of phosphorus in the first conductive layer is 10% thick from the inner surface to the outer side of the first conductive layer. 2. The conductive particle according to claim 1, wherein the conductive particle is 0.5 wt% or more larger than a region having a thickness of 10% from the outer surface toward the inner side .   The electroconductive particle of Claim 1 or 2 which has a processus | protrusion on the electroconductive surface. The electroconductive particle of any one of Claims 1-3 whose sum total thickness of a said 1st conductive layer and a said 2nd conductive layer is 5 nm or more and 1000 nm or less. The electroconductive particle of any one of Claims 1-4 provided with the insulating substance arrange | positioned on the outer surface of a said 2nd conductive layer. The electroconductive material containing the electroconductive particle of any one of Claims 1-5 , and binder resin. A first connection target member, a second connection target member, and a connection portion connecting the first and second connection target members;
A connection structure in which the connection portion is formed of the conductive particles according to any one of claims 1 to 5 , or is formed of a conductive material including the conductive particles and a binder resin.

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