JP2011243455A - Conductive particle, anisotropic conductive material and connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide conductive particles which can reduce connection resistance between electrodes when used for connection between electrodes, and to provide a connection structure using the conductive particles.SOLUTION: Conductive particles 1 have base material particles 2, and a nickel-boron conductive layer 3 provided on the surface 2a of the base material particles 2 and containing nickel and boron. The content of nickel occupies 97 wt% or more of the total 100 wt% content of the nickel-boron conductive layer 3. The connection structure according to the present invention comprises a first member to be connected, a second member to be connected, and a connection part for connecting the first and second members to be connected. The connection part is formed of the conductive particles 1, or an anisotropic conductive material containing the conductive particles 1.

Description

  The present invention relates to conductive particles in which a conductive layer is provided on the surface of substrate particles, and more specifically, for example, conductive particles that can be used for electrical connection between electrodes, and the conductive particles The present invention relates to an anisotropic conductive material and a connection structure.

  Anisotropic conductive materials such as anisotropic conductive pastes, anisotropic conductive inks, anisotropic conductive adhesives, anisotropic conductive films and anisotropic conductive sheets are widely known. In these anisotropic conductive materials, conductive particles are dispersed in paste, ink, or 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, the following Patent Document 1 discloses a conductive material in which a nickel conductive layer or a nickel alloy conductive layer is formed on the surface of spherical base particles having an average particle diameter of 1 to 20 μm by an electroless plating method. Sex particles are disclosed. The conductive particles have minute protrusions of 0.05 to 4 μm on the outermost layer of the conductive layer. The conductive layer and the protrusion are substantially continuously connected.

JP 2000-243132 A

  When the electrodes are connected using the conductive particles described in Patent Document 1, the connection resistance between the electrodes may increase.

  Furthermore, in the electroconductive particle of the Example of patent document 1, the electroconductive layer containing nickel and phosphorus is formed. In many cases, an oxide film is formed on the surfaces of the electrodes connected by the conductive particles and the conductive layer of the conductive particles. When conductive particles having a conductive layer containing nickel and phosphorus are connected between the electrodes, the conductive layer containing nickel and phosphorus is relatively soft. It may not be sufficiently eliminated, and the connection resistance may increase.

  Moreover, when the thickness of the conductive layer containing nickel and phosphorus as described in Patent Document 1 is increased in order to reduce the connection resistance, the connection target member or the substrate may be damaged by the conductive particles.

  An object of the present invention is to provide conductive particles capable of reducing connection resistance between electrodes when used for connection between electrodes, and an anisotropic conductive material and a connection structure using the conductive particles. It is to be.

  According to a wide aspect of the present invention, the nickel-boron conductive layer is provided on the surface of the substrate particle and has a nickel-boron conductive layer containing nickel and boron. Conductive particles having a nickel content of 97% by weight or more in 100% by weight in total are provided.

  In a specific aspect of the conductive particles according to the present invention, in the region having a thickness of ½ from the outer surface of the nickel-boron conductive layer toward the inside in the thickness direction, the boron in the nickel-boron conductive layer The difference between the maximum value and the minimum value of the content is 2% by weight or less.

  In another specific aspect of the conductive particles according to the present invention, boron in the nickel-boron conductive layer is formed in a region having a thickness of 1/5 from the outer surface of the nickel-boron conductive layer toward the inside in the thickness direction. The maximum value of the content of is 3% by weight or less.

  In still another specific aspect of the conductive particle according to the present invention, the particle diameter of the base particle is 2 to 5 μm, and the thickness of the nickel-boron conductive layer is 50 to 300 nm.

  In another specific aspect of the conductive particle according to the present invention, the conductive particle has a protrusion on the outer surface of the nickel-boron conductive layer.

  The anisotropic conductive material which concerns on this invention contains the electroconductive particle comprised according to this invention, and binder resin.

  A 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 described above. The portion is formed of conductive particles configured according to the present invention or an anisotropic conductive material including the conductive particles and a binder resin.

  In the conductive particles according to the present invention, a nickel-boron conductive layer containing nickel and boron is provided on the surface of the base particle, and the nickel content in 100% by weight of the entire nickel-boron conductive layer Therefore, when the conductive particles are used for connection between the electrodes, the connection resistance can be lowered.

FIG. 1 is a cross-sectional view showing conductive particles according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing conductive particles according to another embodiment of the present invention. FIG. 3 is a front sectional view schematically showing a connection structure using conductive particles according to an embodiment of the present invention.

  Details of the present invention will be described below.

  The conductive particles according to the present invention include base particles and a nickel-boron conductive layer provided on the surface of the base particles and containing nickel and boron. The content of nickel is 97% by weight or more in the whole 100% by weight of the nickel-boron conductive layer.

  When the electrodes are connected by conductive particles having a conductive layer containing nickel, the connection resistance between the electrodes can be lowered. Since the conductive particles according to the present invention have a nickel content of 97% by weight or more, the connection resistance between the electrodes can be lowered.

  In addition, in the conductive particles having a nickel conductive layer that does not contain boron, the nickel conductive layer that does not contain boron is too soft, and the oxide film on the surface of the electrode and conductive particles can be sufficiently eliminated when connecting the electrodes. However, the connection resistance may increase. For example, in conductive particles having a conductive layer containing nickel and phosphorus, the oxide film on the surfaces of the electrodes and the conductive particles cannot be sufficiently removed, and the connection resistance tends to be high.

  On the other hand, if the thickness of the conductive layer containing nickel and phosphorus is increased in order to reduce the connection resistance, the connection target member or the substrate may be damaged by the conductive particles.

  On the other hand, in the present invention, the conductive particles have a nickel-boron conductive layer, and the nickel-boron conductive layer has an appropriate hardness, so that the connection resistance between the electrodes can be lowered. For example, in the case of a member to be connected between electrodes, an oxide film on the surfaces of the electrodes and the conductive particles can be sufficiently eliminated, and the connection resistance can be lowered.

  Furthermore, since the said nickel- boron conductive layer has moderate hardness, it can suppress that a connection object member or an electrode is damaged by electroconductive particle.

  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 an embodiment of the present invention.

  As shown in FIG. 1, the conductive particle 1 has a base particle 2 and a nickel-boron conductive layer 3 provided on the surface 2 a of the base particle 2. The nickel-boron conductive layer 3 is a nickel-boron alloy layer. The nickel-boron conductive layer 3 contains nickel and boron. The conductive particles 1 are coated particles in which the surface 2 a of the base particle 2 is coated with a nickel-boron conductive layer 3.

  The conductive particle 1 has a plurality of core substances 4 on the surface 2 a of the base particle 2. The nickel-boron conductive layer 3 covers the core material 4. By covering the core substance 4 with the nickel-boron conductive layer 3, the conductive particles 1 have a plurality of protrusions 5 on the surface 1a. The conductive particle 1 has a plurality of protrusions 5 on the outer surface 3 a of the nickel-boron conductive layer 3. An outer surface 3 a of the nickel-boron conductive layer 3 is raised by the core material 4, and a protrusion 5 is formed.

  The conductive particles 1 have an insulating resin 6 attached to the outer surface 3 a of the nickel-boron conductive layer 3. At least a part of the outer surface 3 a of the nickel-boron conductive layer 3 is covered with the insulating resin 6. In the present embodiment, the insulating resin 6 is insulating resin particles. Thus, the conductive particles may have the insulating resin 6 attached to the outer surface 3 a of the nickel-boron conductive layer 3. However, the conductive particles according to the present invention do not necessarily have the insulating resin 6.

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

  The conductive particles 11 shown in FIG. 2 have base material particles 2 and a nickel-boron conductive layer 12 provided on the surface 2 a of the base material particles 2. The conductive particles 11 do not have the core material 4. The conductive particles 11 do not have protrusions on the surface 11a. The conductive particles 11 do not have protrusions on the outer surface 12 a of the nickel-boron conductive layer 12. Thus, the electroconductive particle which concerns on this invention does not need to have a processus | protrusion, and may be spherical. Further, the conductive particles 11 do not have an insulating resin.

  Examples of the base particle 2 include resin particles, inorganic particles, organic-inorganic hybrid particles, and metal particles.

  The substrate particles 2 are preferably resin particles formed of a resin. When connecting the electrodes using the conductive particles 1 and 11, the conductive particles 1 and 11 are generally compressed after the conductive particles 1 and 11 are arranged between the electrodes. When the base particle 2 is a resin particle, the conductive particles 1 and 11 are easily deformed by compression, and the contact area between the conductive particles 1 and 11 and the electrode can be increased. For this reason, the conduction | electrical_connection reliability between electrodes can be improved.

  Examples of the resin for forming the resin particles include polyolefin resin, acrylic resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polyethylene terephthalate, polysulfone, and polyphenylene. Examples thereof include oxides, polyacetals, polyimides, polyamideimides, polyetheretherketones, and polyethersulfones. Since the conductive particles can be appropriately deformed by compression, the resin particles are formed of a polymer obtained by polymerizing one or more polymerizable monomers having an ethylenically unsaturated group. Is preferred.

  Examples of the inorganic substance for forming the inorganic particles include silica and carbon black. Examples of the organic / inorganic hybrid particles include organic / inorganic hybrid particles formed of a crosslinked alkoxysilyl polymer and an acrylic resin.

  When the base particle 2 is a metal particle, examples of the metal for forming the metal particle include silver, copper, nickel, silicon, gold, and titanium.

  The particle diameter of the base particle 2 is preferably in the range of 1 to 100 μm. The more preferable lower limit of the particle diameter of the substrate particles is 2 μm, the more preferable upper limit is 50 μm, the still more preferable upper limit is 30 μm, and the particularly preferable upper limit is 5 μm. When the particle diameter of the base particle 2 satisfies the above lower limit, the conduction reliability between the electrodes can be further enhanced. When the particle diameter of the base particle 2 satisfies the above upper limit, the distance between the electrodes can be reduced. The particle diameter of the base particle indicates the diameter when the base particle is a true sphere, and indicates the maximum diameter when the base particle is not a true sphere.

  The particle diameter of the substrate particles 2 is preferably in the range of 2 to 5 μm. When the particle diameter of the base particle 2 is in the range of 2 to 5 μm, the distance between the electrodes can be reduced, and even if the thickness of the nickel-boron conductive layer is increased, small conductive particles can be obtained. Can do.

  The main feature of this embodiment is that the nickel content is 97% by weight or more in 100% by weight of the entire nickel-boron conductive layers 3 and 12. When the nickel content is 97% by weight or more, the connection resistance between the electrodes can be lowered when the conductive particles 1 and 11 are used for the connection between the electrodes. From the viewpoint of further reducing the connection resistance between the electrodes, the nickel content is preferably 97.5% by weight or more in the total of 100% by weight of the nickel-boron conductive layers 3 and 12, and 98% by weight or more. It is more preferable that The content of nickel indicates the total content of nickel in 100% by weight of the entire nickel-boron conductive layers 3 and 12.

  The content of boron is 3% by weight or less in the total 100% by weight of the nickel-boron conductive layers 3 and 12. When the boron content is 3% by weight or less, the nickel content is relatively increased, so that when the conductive particles 1 and 11 are used for connection between the electrodes, the connection resistance between the electrodes is lowered. be able to. From the viewpoint of further reducing the connection resistance between the electrodes, the content of boron is preferably 2.5% by weight or less in the total of 100% by weight of the nickel-boron conductive layers 3 and 12, and 2% by weight or less. It is more preferable that The boron content represents the total content of boron in 100% by weight of the entire nickel-boron conductive layers 3 and 12.

  The nickel-boron conductive layers 3 and 12 may contain atoms other than nickel and boron. The nickel-boron conductive layers 3 and 12 may contain a metal other than nickel.

  Examples of the other metal include gold, silver, palladium, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, chromium, titanium, antimony, germanium, cadmium, palladium, bismuth, thallium, tin- Examples include lead alloys, tin-copper alloys, tin-silver alloys, and tin-lead-silver alloys.

  Maximum and minimum contents of boron in the nickel-boron conductive layers 3 and 12 in a region having a thickness of ½ inward in the thickness direction from the outer surfaces 3a and 12a of the nickel-boron conductive layers 3 and 12 The difference from the value (hereinafter sometimes referred to as difference D) is preferably 2% by weight or less. That is, when the thickness of the nickel-boron conductive layers 3 and 12 is T, in the region of 0 to 0.5T inward in the thickness direction from the outer surfaces 3a and 12a of the nickel-boron conductive layers 3 and 12, The difference D between the maximum value and the minimum value of the boron content in the nickel-boron conductive layers 3 and 12 is preferably 2% by weight or less. The difference D is more preferably 1.5% by weight or less, still more preferably 1% by weight or less.

  The maximum value of the boron content in the nickel-boron conductive layers 3 and 12 (hereinafter referred to as “thickness”) in the region whose thickness is 1/5 from the outer surfaces 3a and 12a of the nickel-boron conductive layers 3 and 12 inward in the thickness direction The maximum value M may be 3% by weight or less. That is, when the thickness of the nickel-boron conductive layers 3 and 12 is T, in the region of 0 to 0.2T inward in the thickness direction from the outer surfaces 3a and 12a of the nickel-boron conductive layers 3 and 12, The maximum value M of the boron content in the nickel-boron conductive layers 3 and 12 is preferably 3% by weight or less. The maximum value M is more preferably 2.5% by weight or less, and further preferably 2% by weight or less.

  The method for measuring the nickel content and the boron content in the nickel-boron conductive layers 3 and 12 is not particularly limited, and various known analytical methods can be used. Examples of the measuring method include atomic absorption analysis or atomic spectrum analysis. In the atomic absorption analysis method, a flame atomic absorption photometer, an electric heating furnace atomic absorption photometer, or the like can be used. Examples of the atomic spectrum analysis method include a plasma emission analysis method and a plasma ion source mass spectrometry method.

  When measuring the nickel content and boron content in 100% by weight of the entire nickel-boron conductive layers 3 and 12, it is preferable to use an ICP emission spectrometer. Examples of commercially available ICP emission analyzers include ICP emission analyzers manufactured by HORIBA.

  When measuring the boron content distribution in the thickness direction of the nickel-boron conductive layers 3 and 12, it is preferable to use an FE-TEM apparatus. Examples of commercially available FE-TEM devices include JEM-2010 manufactured by JEOL Ltd.

  The method for forming the nickel-boron conductive layers 3 and 12 on the surface 2a of the base particle 2 is not particularly limited. Examples of the method for forming the nickel-boron conductive layers 3 and 12 include, for example, a method using electroless plating, a method using electroplating, a method using physical vapor deposition, and a paste containing metal powder or a metal powder and a binder. And the like. Especially, since formation of the nickel-boron conductive layer 3 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.

  As a method of bringing the nickel content in the nickel-boron conductive layers 3 and 12 within the above range, for example, when the nickel-boron conductive layers 3 and 12 are formed by electroless nickel plating, the pH of the nickel plating solution is adjusted. Examples thereof include a method of controlling, a method of adjusting the concentration of the boron-containing reducing agent, and a method of adjusting the nickel salt concentration when the nickel-boron conductive layer is formed by electroless nickel plating.

  In the method of forming by electroless plating, generally, a catalyzing step and an electroless plating step are performed. Hereinafter, an example of a method for forming an alloy plating layer containing nickel and boron on the surface of resin particles by electroless plating will be described.

  In the catalyzing step, a catalyst serving as a starting point for forming a plating layer by electroless plating is formed on the surface of the resin particles.

  As a method of forming the catalyst on the surface of the resin particles, for example, after adding the resin particles to a solution containing palladium chloride and tin chloride, the surface of the resin particles is activated with an acid solution or an alkali solution, A method of depositing palladium on the surface of the resin particles, and after adding the resin particles to a solution containing palladium sulfate and aminopyridine, the surface of the resin particles is activated by a solution containing a reducing agent. Examples thereof include a method of depositing palladium on the surface. As the reducing agent, a boron-containing reducing agent is preferably used. However, a phosphorus-containing reducing agent such as sodium hypophosphite may be used as the reducing agent.

  In the electroless plating step, a nickel plating bath containing a nickel salt and the boron-containing reducing agent is used. By immersing the resin particles in the nickel plating bath, nickel can be deposited on the surface of the resin particles on which the catalyst is formed, and a conductive layer containing nickel and boron can be formed.

  Examples of the boron-containing reducing agent include dimethylamine borane, sodium borohydride, and potassium borohydride.

  Like the electroconductive particle 1, it is preferable that the electroconductive particle which concerns on this invention has a processus | protrusion on the surface. The conductive particles preferably have protrusions on the surface of the nickel-boron conductive layer. The conductive particles preferably have a plurality of protrusions on the surface. The conductive particles preferably have a plurality of protrusions on the surface of the nickel-boron conductive layer. 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 the conductive particles having protrusions, the oxide film is 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 resin on the surface, or when the conductive particles are dispersed in the resin and used as an anisotropic conductive material, the conductive particles and the electrodes are The resin between can be effectively eliminated. For this reason, the conduction | electrical_connection reliability between electrodes can be improved.

  As a method of forming protrusions on the surface of the conductive particles, a method of forming a nickel-boron conductive layer by electroless plating after attaching a core substance to the surface of the substrate particles, Examples of the method include forming a nickel-boron conductive layer by electrolytic plating, attaching a core substance, and further forming a nickel-boron conductive layer by electroless plating.

  The thicknesses of the nickel-boron conductive layers 3 and 12 are preferably in the range of 5 to 1000 nm. The more preferable lower limit of the thickness of the nickel-boron conductive layers 3 and 12 is 10 nm, the still more preferable lower limit is 50 nm, the more preferable upper limit is 500 nm, and the still more preferable upper limit is 300 nm. When the thickness of the nickel-boron conductive layers 3 and 12 satisfies the above lower limit, the conductivity of the conductive particles 1 and 11 can be sufficiently increased. When the thicknesses of the nickel-boron conductive layers 3 and 12 satisfy the above upper limit, the difference in thermal expansion coefficient between the base particle 2 and the nickel-boron conductive layers 3 and 12 becomes small, and the nickel-boron conductivity is reduced from the base particle 2. Layers 3 and 12 are difficult to peel off.

  The thickness of the nickel-boron conductive layers 3 and 12 is particularly preferably 50 to 300 nm. Furthermore, it is particularly preferable that the particle diameter of the base particles is 2 to 5 μm, and the thickness of the nickel-boron conductive layer is 50 to 300 nm. In this case, the conductive particles can be suitably used for applications in which a large current flows. Furthermore, when the conductive particles are compressed to connect the electrodes, it is possible to further suppress the electrodes from being damaged.

  As a method of attaching the core substance to the surface of the base particle, for example, a conductive substance that becomes 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, a fan. A method of accumulating and adhering by Delwars force, and adding a conductive substance as a core substance to a container containing base particles, and a core substance on the surface of the base particles by mechanical action such as rotation of the container And the like. Among them, a method of accumulating and adhering the core substance on the surface of the base particle in the dispersion is preferable because the amount of the core substance to be attached is easy to control.

  Examples of the conductive substance constituting the core substance 4 include conductive nonmetals such as metals, metal oxides, and graphite, and conductive polymers. Examples of the conductive polymer include polyacetylene. Among them, metal is preferable because conductivity can be increased.

  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, and tin-lead-silver alloys. 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 nickel-boron conductive layer. Especially, it is more preferable that the metal which comprises the said core substance is the optimal nickel for promoting the epitaxial growth of a nickel- boron conductive layer.

  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.

  Like the electroconductive particle 1, it is preferable that the electroconductive particle which concerns on this invention has the insulating resin adhering to the surface of the said nickel- boron conductive 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 resin 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. . In addition, the insulating resin between the said nickel- boron conductive layer and an electrode can be easily excluded by pressurizing electroconductive particle with two electrodes in the case of the connection between electrodes. In the case where the conductive particles have protrusions on the surface of the nickel-boron conductive layer, the insulating resin between the nickel-boron conductive layer and the electrode can be more easily removed.

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

  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 compounds 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 attaching an insulating resin to the surface of the nickel-boron 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 resin particles are difficult to peel off, a method of attaching the insulating resin particles to the surface of the nickel-boron conductive layer through a chemical bond is preferable.

  The insulating resin is preferably insulating resin particles. In this case, when the conductive particles are used for the connection between the electrodes, not only can a short circuit between the electrodes adjacent in the lateral direction be prevented, but also the connection resistance between the connected upper and lower electrodes can be lowered.

(Anisotropic conductive material)
The anisotropic conductive material according to the present invention includes the above-described conductive particles and a binder resin.

  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 anisotropic conductive material includes, for example, a filler, an extender, a softener, a plasticizer, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, and a heat stabilizer. Further, various additives such as a light stabilizer, 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, kneaded and dispersed 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 anisotropic conductive material according to the present invention can be used as an anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive adhesive, anisotropic conductive film, or anisotropic conductive sheet. When the anisotropic conductive material according to the present invention is used as a film-like adhesive such as an anisotropic conductive film or an anisotropic conductive sheet, the film-like adhesive containing the conductive particles, A film-like adhesive that does not contain conductive particles may be laminated.

  In 100% by weight of the anisotropic conductive material, the content of the binder resin is preferably in the range of 10 to 99.99% by weight. The more preferable lower limit of the content of the binder resin is 30% by weight, the still more preferable lower limit is 50% by weight, the particularly preferable lower limit is 70% by weight, and the more preferable upper limit is 99.9% by weight. When the content of the binder resin satisfies the above lower limit and upper limit, the conductive particles can be efficiently arranged between the electrodes, and the connection reliability of the connection target member connected by the anisotropic conductive material can be further improved. it can.

  In 100% by weight of the anisotropic conductive material, the content of the conductive particles is preferably in the range of 0.01 to 20% by weight. A more preferable lower limit of the content of the conductive particles is 0.1% by weight, and a more preferable upper limit is 10% by weight. When content of the said electroconductive particle satisfy | fills the said minimum and upper limit, the conduction | electrical_connection reliability between electrodes can be improved further.

(Connection structure)
A connection structure can be obtained by connecting the connection target member using the conductive particles of the present invention or an anisotropic 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 that electrically connects the first and second connection target members. The connection structure is preferably formed of the conductive particles of the invention or 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 one Embodiment of this invention is typically shown with front sectional drawing.

  The connection structure 21 shown in FIG. 3 includes a first connection target member 22, a second connection target member 23, and a connection portion 24 connecting the first and second connection target members 22 and 23. Prepare. The connecting portion 24 is formed by curing an anisotropic conductive material including the conductive particles 1. In FIG. 3, the conductive particles 1 are schematically shown for convenience of illustration.

  A plurality of electrodes 22 b are provided on the upper surface 22 a of the first connection target member 22. A plurality of electrodes 23 b are provided on the lower surface 23 a of the second connection target member 23. The electrode 22b and the electrode 23b are electrically connected by one or a plurality of conductive particles 1. Accordingly, the first and second connection target members 22 and 23 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 anisotropic 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 The method of pressurizing is mentioned.

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 circuit boards such as printed boards, flexible printed boards, and glass boards.

  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 metal oxide 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
Divinylbenzene copolymer resin particles having a particle size of 5.0 μm (“Micropearl SP-205” manufactured by Sekisui Chemical Co., Ltd.) were prepared.

  After dispersing 10 parts by weight of the resin particles in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution using an ultrasonic disperser, the resin particles were taken out by filtering the solution. Next, the resin particles were added to 100 parts by weight of a 1% by weight dimethylamine borane solution to activate the surface of the resin particles. The resin particles whose surface was activated were sufficiently washed with water, and then added to 500 parts by weight of distilled water and dispersed to obtain a suspension.

  Further, a nickel plating solution (pH 8.5) containing 0.23 mol / L of nickel sulfate, 0.92 mol / L of dimethylamine borane, and 0.5 mol / L of sodium citrate was prepared.

  While stirring the obtained suspension at 60 ° C., the nickel plating solution was gradually added dropwise to the suspension to perform electroless nickel plating. When a conductive layer (nickel-boron conductive layer containing nickel and boron) having a thickness of about 0.08 μm was formed on the surface of the resin particles, dropping of the electroless plating solution was terminated. Thereafter, the suspension was filtered to take out the particles, washed with water, and dried to obtain conductive particles having a nickel-boron conductive layer (thickness: 0.1 μm) on the surface of the resin particles.

(Example 2)
Conductive particles having a nickel-boron conductive layer (thickness: 0.1 μm) provided on the surface of the resin particles were obtained in the same manner as in Example 1 except that the nickel sulfate concentration was changed to 0.19 mol / L. .

(Example 3)
Except having changed the temperature of suspension to 55 degreeC, it carried out similarly to Example 1, and obtained the electroconductive particle by which the nickel- boron conductive layer (thickness 0.1 micrometer) was provided in the surface of the resin particle.

Example 4
(1) Palladium adhesion process The divinylbenzene resin particle ("Micropearl SP-205" by Sekisui Chemical Co., Ltd.) whose particle diameter is 5.0 micrometers was 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 0.5 wt% dimethylamine borane solution at pH 6 to obtain resin particles to which palladium was attached.

(2) Core substance adhesion step The 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 metal nickel particle slurry (average particle diameter 200 nm) was added to the dispersion over 3 minutes to obtain resin particles to which the core substance was adhered.

(3) Electroless nickel plating step 500 mL of ion-exchanged water was added to the resin particles to which the core substance was adhered, and the resin particles were sufficiently dispersed to obtain a suspension. While stirring this suspension, an electroless nickel plating solution having a pH of 5.0 containing nickel sulfate hexahydrate 50 g / L, dimethylamine borane 0.32 g / L and citric acid 50 g / L was gradually added. Electroless nickel plating was performed. In this way, a nickel-boron conductive layer (thickness 0.1 μm) was provided on the surface of the resin particles, and conductive particles having protrusions on the surface of the nickel-boron conductive layer were obtained.

(Example 5)
(1) Production of insulating resin particles In 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, 100 mmol of methyl methacrylate and N, N, N-trimethyl Ion-exchanged water containing 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. Then, the mixture was stirred at 200 rpm and polymerized at 70 ° C. for 24 hours under a nitrogen atmosphere. After completion of the reaction, freeze drying was performed to obtain insulating resin particles having an ammonium group on the surface, an average particle diameter of 220 nm, and a CV value of 10%.

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

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

(Comparative Example 1)
Conductivity containing nickel and phosphorus on the surface of the resin particles in the same manner as in Example 1 except that 0.92 mol / L of dimethylamine borane in the nickel plating solution was changed to 0.5 mol / L of sodium hypophosphite. Conductive particles provided with a layer (thickness 0.1 μm) were obtained.

(Comparative Example 2)
Conductive particles in which a nickel-boron conductive layer (thickness: 0.1 μm) was provided on the surface of the resin particles were the same as in Example 1 except that the nickel sulfate concentration was changed to 0.11 mol / L. Obtained.

(Example 6)
Conductive particles having a nickel-boron conductive layer (thickness 0.1 μm) provided on the surface of the resin particles were obtained in the same manner as in Example 2 except that the dropping speed was changed to half.

(Example 7)
Except having changed the stirring rotation speed to 1/3, it carried out similarly to Example 3, and obtained the electroconductive particle by which the nickel- boron conductive layer (thickness 0.1 micrometer) was provided in the surface of the resin particle.

(Evaluation)
(1) Content of nickel and boron in 100% by weight of the entire conductive layer 5 g of conductive particles are added to a mixed solution of 5 mL of 60% nitric acid and 10 mL of 37% hydrochloric acid to completely dissolve the conductive layer. Obtained. Using the obtained solution, the contents of nickel and boron were analyzed with an ICP-MS analyzer (manufactured by Hitachi, Ltd.).

(2) Content of boron in the thickness direction of the nickel-boron conductive layer The distribution of the content of boron in the thickness direction from the outer surface of the nickel-boron conductive layer was measured. The difference between the maximum value and the minimum value of the boron content in the nickel-boron conductive layer in the region having a thickness of ½ from the outer surface of the nickel-boron conductive layer toward the inside in the thickness direction is “difference D”. The results are shown in Table 1 below. In the region of 1/5 thickness inward in the thickness direction from the outer surface of the nickel-boron conductive layer, the maximum value of the boron content in the nickel-boron conductive layer is defined as “maximum value M”, and the results are shown below. It showed in Table 1.

(3) Plating state The plating state of 50 conductive particles obtained was observed with a scanning electron microscope. The presence or absence of plating unevenness such as plating cracking or plating peeling was observed. The results are shown in Table 1 below, assuming that the number of conductive particles in which plating unevenness is confirmed is 4 or less is “good” and the case in which there are 5 or more conductive particles in which uneven plating is confirmed is “bad”. .

(4) Preparation of connection structure 10 parts by weight of bisphenol A type epoxy resin (“Epicoat 1009” manufactured by Japan Epoxy Resin Co., Ltd.), 40 parts by weight of acrylic rubber (weight average molecular weight of about 800,000), 200 parts by weight of methyl ethyl ketone, Mixing 50 parts by weight of a microcapsule type 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), the content of conductive particles is 3 It added so that it might become volume%, it was made to 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. A glass substrate (width 3 cm, length 3 cm) provided with an aluminum electrode (height 0.2 μm, L / S = 20 μm / 20 μm) having a lead wire for resistance measurement on one side of the cut anisotropic conductive film. ) On the aluminum electrode side. Subsequently, the two-layer flexible printed circuit board (width 2cm, length 1cm) provided with the same aluminum electrode was bonded after aligning so that electrodes might overlap. 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.

(5) Connection resistance The connection resistance between the electrodes facing each other of the connection structure obtained in the preparation of the connection structure (4) was measured by a four-terminal method. The connection resistance was evaluated according to the following evaluation criteria.

[Evaluation criteria for connection resistance]
○○: 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

  The results are shown in Table 1 below.

  In Table 1, the difference D is the maximum value of the boron content in the nickel-boron conductive layer in a region having a thickness of 1/2 from the outer surface of the nickel-boron conductive layer toward the inside in the thickness direction. Indicates the difference from the minimum value. The maximum value M indicates the maximum value of the boron content in the nickel-boron conductive layer in a region having a thickness of 1/5 from the outer surface of the nickel-boron conductive layer toward the inside in the thickness direction.

DESCRIPTION OF SYMBOLS 1 ... Conductive particle 1a ... Surface 2 ... Base material particle 2a ... Surface 3 ... Nickel-boron conductive layer 3a ... Outer surface 4 ... Core substance 5 ... Protrusion 6 ... Insulating resin 11 ... Conductive particle 12 ... Nickel-boron conductive Layer 12a ... outer surface 21 ... connection structure 22 ... first connection target member 22a ... upper surface 22b ... electrode 23 ... second connection target member 23a ... lower surface 23b ... electrode 24 ... connection portion

Claims (7)

Substrate particles,
A nickel-boron conductive layer provided on the surface of the substrate particles and containing nickel and boron;
The electroconductive particle whose content of nickel is 97 weight% or more in 100 weight% of the whole nickel- boron conductive layer.   The difference between the maximum value and the minimum value of the boron content in the nickel-boron conductive layer is 2 in the region having a thickness of ½ inward in the thickness direction from the outer surface of the nickel-boron conductive layer. The electroconductive particle of Claim 1 which is weight% or less.   The maximum boron content in the nickel-boron conductive layer is 3% by weight or less in a region having a thickness of 1/5 from the outer surface of the nickel-boron conductive layer toward the inside in the thickness direction. Item 3. The conductive particle according to Item 1 or 2. The particle size of the substrate particles is 2 to 5 μm, and
The electroconductive particle of any one of Claims 1-3 whose thickness of the said nickel- boron conductive layer is 50-300 nm.   The electroconductive particle of any one of Claims 1-4 which has a processus | protrusion on the outer surface of a nickel- boron conductive layer.   An anisotropic conductive 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 part connecting the first and second connection target members;
The connection structure in which the said connection part is formed with the anisotropic conductive material containing the electroconductive particle of any one of Claims 1-5, or this electroconductive particle and binder resin.

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