JP2015195217A - Anisotropic conductive material and connecting structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive particle which, when a connection structure is obtained by connecting between electrodes, hardly increases connection resistance between the electrodes even if the connection structure is exposed to high temperature and high humidity, and to provide a connection structure using the conductive particle.SOLUTION: There is provided a conductive particle which comprises a substrate particle 2, a copper layer 3 provided on the surface 2a of the substrate particle 2 and a palladium layer 4 provided on the surface of the copper layer 3. The palladium layer 4 has an average thickness of 5 to 500 nm. A copper ion concentration eluted when 100 pts.wt. of a plurality of conductive particles 1 are immersed in 1000 pts.wt. of 0.001 N nitric acid for one minute at 25°C is 5 ppm/cmor less per unit surface area of the conductive particle 1.

Description

  The present invention relates to conductive particles that can be used, for example, for connection between electrodes, and more specifically, conductive particles that can improve conduction reliability between electrodes when used for connection between electrodes, and The present invention relates to an anisotropic conductive material and a connection structure using the conductive particles.

  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 used for the anisotropic conductive material, the following Patent Document 1 includes resin particles, a copper layer provided on the surface of the resin particles, and provided on the surface of the copper layer. Conductive particles comprising a palladium layer are disclosed. Patent Document 1 describes that such a conductive particle is not disclosed in a specific embodiment, but a good electrical connection can be obtained in connection of opposing circuits.

JP 2003-323813 A

  Conventionally, the conductive particles described in Patent Document 1 are manufactured as follows.

  First, a copper layer is formed on the surface of the resin particles. Next, a catalyzing step of attaching a palladium catalyst to the surface of the copper layer is performed. Thereafter, a palladium layer is formed using a plating solution containing sodium hypophosphite as a reducing agent.

  That is, when manufacturing the said electroconductive particle, since copper does not have catalytic property, before forming a palladium layer, the catalyzing process which makes a palladium catalyst adhere to the surface of a copper layer is performed. When such a catalyzing step is performed, the copper layer may be oxidized or eroded by the catalyst solution.

  Furthermore, when the palladium layer is formed after the catalyzing step, since palladium plating proceeds along the catalyst nucleus, the crystal grains in the palladium layer become large. Furthermore, when forming a thin palladium layer having a thickness of 500 nm or less, it is difficult to uniformly cover the surface of the copper layer with the palladium layer, and for example, minute holes may be formed in the palladium layer. . For this reason, the obtained electroconductive particle has the weak tolerance with respect to an external environment, a copper layer oxidizes, or copper corrosion by the galvanic reaction between copper-palladium occurs. As a result, the conductivity of the entire conductive layer in the conductive particles may be impaired.

  In particular, when the connection structure is formed using the conductive particles described in Patent Document 1 for connection between the electrodes, the connection resistance between the electrodes is reduced when the connection structure is exposed to high temperature and high humidity. The current capacity that the conductive particles in contact with the electrode can withstand may be low.

  An object of the present invention is to obtain a connection structure by connecting electrodes, and even when the connection structure is exposed to high temperature and high humidity, the conductive particles are less likely to have a high connection resistance between the electrodes, and An anisotropic conductive material and a connection structure using the conductive particles are provided.

According to a wide aspect of the present invention, the method includes a substrate particle, a copper layer provided on the surface of the substrate particle, and a palladium layer provided on the surface of the copper layer, wherein the average thickness of the palladium layer is It is 5 to 500 nm. When 100 parts by weight of the plurality of conductive particles are immersed in 1,000 parts by weight of 0.001N nitric acid at 25 ° C. for 1 minute, the copper ion concentration to be eluted is 5 ppm / per unit surface area of the conductive particles. Conductive particles are provided that are cm ² or less.

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

  In another specific aspect of the conductive particle according to the present invention, an insulating resin layer or an insulating resin particle attached to the surface of the palladium layer is provided.

  In still another specific aspect of the conductive particles according to the present invention, insulating resin particles attached to the surface of the palladium layer are provided.

  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 copper layer and a palladium layer are provided in this order on the surface of the base particle, the average thickness of the palladium layer is 5 to 500 nm, and a plurality of the conductive materials are provided. When 100 parts by weight of particles are immersed in 1000 parts by weight of 0.001N nitric acid at 25 ° C. for 1 minute, the eluted copper ion concentration is 5 ppm / cm ² or less per unit surface area of the conductive particles. When the connection structure used for the connection between the electrodes is exposed to high temperature and high humidity, it is possible to suppress an increase in connection resistance. Therefore, the conduction reliability of the connection structure can be improved.

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. 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 the example and the comparative example.

  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 particles 1 include a base particle 2, a copper layer 3 provided on the surface 2 a of the base particle 2, and a palladium layer 4 provided on the surface 3 a of the copper layer 3. With. The copper layer 3 and the palladium layer 4 are conductive layers. The conductive particles 1 may further include an insulating resin layer or insulating resin particles attached to the surface 4 a of the palladium layer 4.

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

  As shown in FIG. 2, the conductive particles 11 are composed of base particles 2, a copper layer 12 provided on the surface 2 a of the base particles 2, and a palladium layer 13 provided on the surface 12 a of the copper layer 12. With. The copper layer 12 and the palladium layer 13 are conductive layers. The conductive particle 11 includes a plurality of core substances 14 on the surface 2 a of the base particle 2. The copper layer 12 and the palladium layer 13, which are conductive layers, cover the core substance 14. By covering the core substance 14 with the conductive layer, the conductive particles 11 have a plurality of protrusions 15 on the surface 11a. The conductive particle 11 has a plurality of protrusions 15 on the outer surface 13 a of the palladium layer 13. The protrusion 15 is formed on the surface 13 a of the palladium layer 13. The surface 13 a of the palladium layer 13 is raised by the core material 14, and a protrusion 15 is formed.

  The conductive particles 11 include insulating resin particles 16 attached to the surface 13 a of the palladium layer 13. In the present embodiment, a part of the surface of the palladium layer 13 is covered with the insulating resin particles 16. Thus, the conductive particles may include the insulating resin particles 16 attached to the surface 13a of the palladium layer 13. However, the insulating resin particles 16 are not necessarily provided. Further, an insulating resin layer may be provided instead of the insulating resin particles 16. The conductive particles may include an insulating resin layer attached to the surface 13 a of the palladium layer 13. The surface 13a of the palladium layer 13 may be covered with an insulating resin layer.

  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 the electrodes are connected, the conductive particles 1 and 11 are generally compressed after the conductive particles 1 and 11 are disposed 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 is 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 average particle diameter of the substrate particles 2 is preferably in the range of 1 to 100 μm. When the average particle diameter of the substrate particles is 1 μm or more, the conduction reliability between the electrodes can be further improved. The space | interval between electrodes can be narrowed as the average particle diameter of a base particle is 100 micrometers or less. The more preferable lower limit of the average particle diameter of the base particle 2 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.

  The average particle diameter indicates a number average particle diameter. The average particle size can be measured using, for example, a Coulter counter (manufactured by Beckman Coulter).

  The average thickness of the palladium layers 4 and 13 is 5 nm or more. When the average thickness of the palladium layers 4 and 13 is 5 nm or more, the surfaces 3 a and 12 a of the copper layers 3 and 12 can be uniformly covered with the palladium layers 4 and 13. For this reason, the conductive particles 1 and 11 have high resistance to the external environment, the copper layer is difficult to oxidize, and copper corrosion due to the galvanic reaction between copper and palladium hardly occurs. For this reason, the electroconductivity of the whole electroconductive layer in electroconductive particle 1 and 11 can be improved further.

  The average thickness of the palladium layers 4 and 13 is 500 nm or less. When the average thickness of the palladium layers 4 and 13 is 500 nm or less, the cost of the conductive particles is reduced. Furthermore, since the usage-amount of palladium can be reduced, an environmental load can be reduced.

  The preferable lower limit of the average thickness of the palladium layers 4 and 13 is 10 nm, and the preferable upper limit is 400 nm. When the average thickness of the palladium layers 4 and 13 is 10 nm or more, the conductivity of the conductive particles 1 and 11 can be further increased.

  The total average thickness of the copper layers 3 and 12 and the palladium layers 4 and 13, that is, the average thickness of the conductive layer is preferably within a range of 10 to 1000 nm. A more preferable lower limit of the average thickness of the conductive layer is 20 nm, and a more preferable upper limit is 800 nm. The electroconductivity of the electroconductive particles 1 and 11 can be improved further as the average thickness of an electroconductive layer is more than the said minimum. When the average thickness of the conductive layer is not more than the above upper limit, the difference in thermal expansion coefficient between the base particle 2 and the conductive layer becomes small, and the conductive layer becomes difficult to peel from the base particle 2.

  Examples of the method of forming the copper layers 3 and 12 on the surface 2a of the substrate particle 2 include a method of forming a copper layer by electroless plating and a method of forming a copper layer by electroplating.

  As a method of forming the palladium layers 4 and 13 on the surfaces 3a and 12a of the copper layers 3 and 12, a method of forming a palladium layer using a plating solution containing a hydrazine compound as a reducing agent is used. The palladium layers 4 and 13 are preferably palladium layers formed using a plating solution containing a hydrazine compound as a reducing agent.

The feature of this embodiment is that the average thickness of the palladium layer is 5 to 500 nm, the thickness of the palladium layer is thin, and 100 parts by weight of the plurality of conductive particles is added to 1000 parts by weight of 0.001N nitric acid at 25 ° C. The copper ion concentration which elutes when immersed for a minute is 5 ppm / cm ² or less per unit surface area of the conductive particles.

This embodiment is particularly characterized in that the copper ion concentration is 5 ppm / cm ² or less in conductive particles having a palladium layer thickness of 5 to 500 nm.

Even in the case of conventional conductive particles, when the average thickness of the palladium layer exceeds 500 nm, the surface of the copper layer is sufficiently covered even if the crystal grains of the palladium are large, so that the copper ion concentration is 5 ppm / cm ² or less. There may be. On the other hand, in the conventional conductive particles, when the thickness of the palladium layer is 500 nm or less, the copper ion concentration cannot be reduced to 5 ppm / cm ² or less due to large crystal grains of palladium. It was. Therefore, the conventional conductive particles have poor resistance to the external environment, and the copper layer may be oxidized or copper may be corroded by a galvanic reaction between copper and palladium. For this reason, the electroconductivity of the whole electroconductive layer in electroconductive particle may be impaired. In particular, when a connection structure is formed using conventional conductive particles for connection between electrodes, the connection resistance between the electrodes may increase when the connection structure is exposed to high temperature and high humidity. In some cases, the current capacity that the conductive particles in contact with the electrode can withstand is low.

In contrast, in the conductive particles 1 and 11 in which the palladium layers 4 and 13 have an average thickness of 5 to 500 nm and the copper ion concentration is 5 ppm / cm ² or less, the resistance to the external environment is increased, and the copper Oxidation of the layers 3 and 12 hardly occurs, and copper corrosion due to a galvanic reaction between copper and palladium hardly occurs. For this reason, the electroconductivity of the whole electroconductive layer in electroconductive particle 1 and 11 can be improved. Furthermore, when the connection structure is obtained by connecting the electrodes, the conduction reliability of the connection structure under high temperature and high humidity can be increased, and the current capacity that the conductive particles in contact with the electrode can withstand is increased. be able to.

For example, when the palladium layers 4 and 13 are formed on the surfaces 3a and 12a of the copper layers 3 and 12, by using a plating solution containing a hydrazine compound as a reducing agent, palladium plating proceeds while imparting catalytic properties to copper. Therefore, the crystal grains in the palladium layers 4 and 13 can be made extremely small. Specifically, fine palladium crystals are formed by the epitaxial growth of palladium plating. As a result, even if the average thickness of the palladium layers 4 and 13 is 5 to 500 nm, the surfaces 3a and 12a of the copper layers 3 and 12 can be uniformly coated with the palladium layers 4 and 13, and the copper ion concentration is 5 ppm / cm. It becomes possible to make it ² or less.

  If a plating solution containing a hydrazine compound as a reducing agent is used to form the palladium layers 4 and 13, the palladium plating is spontaneously performed without imparting a palladium catalyst to the surfaces 3 a and 12 a of the copper layers 3 and 12. proceed. Therefore, the catalyzing step of applying a palladium catalyst to the surfaces 3a and 12a of the copper layers 3 and 12 can be omitted. As a result, the copper layers 3 and 12 are not eroded by the catalyst solution, and the production efficiency of the conductive particles 1 and 11 can be increased.

  Therefore, it is preferable to form the palladium layers 4 and 13 using a plating solution containing a hydrazine compound as a reducing agent. In this case, apart from the step of forming the palladium layers 4 and 13 using a plating solution containing a hydrazine compound as a reducing agent, a catalyzing step of imparting a palladium catalyst to the surfaces 3a and 12a of the copper layers 3 and 12 is performed. It is preferable not to do so. The palladium layers 4 and 13 are palladium layers formed by using a plating solution containing a hydrazine compound as a reducing agent without performing a catalyzing step of imparting a palladium catalyst to the surfaces 3a and 12a of the copper layers 3 and 12. It is preferable.

  Examples of the hydrazine compound include hydrazine and hydrazine salts.

  The plating solution for forming the palladium layers 4 and 13 preferably contains a hydrazine compound and a phosphorus-containing reducing agent as a reducing agent. By using a plating solution containing a hydrazine compound and a phosphorus-containing reducing agent as the reducing agent, the crystal grains in the palladium layers 4 and 13 can be further reduced, and the denser palladium layers 4 and 13 can be formed. As a result, the conduction reliability of the connection structure under high temperature and high humidity can be improved.

  Examples of the phosphorus-containing reducing agent include sodium hypophosphite.

  From the viewpoint of further reducing the crystal grains in the palladium layers 4 and 13 and further improving the conduction reliability under high temperature and high humidity of the connection structure, the phosphorus-containing reducing agent is preferably a phosphate compound. Hypophosphite is more preferable, and sodium hypophosphite is still more preferable.

  Like the electroconductive particle 11, 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 conductive layer, and more preferably have protrusions on the surface of the palladium layer. It is preferable that there are a plurality of protrusions. 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 can be contacted still more reliably, and the connection resistance between electrodes can be made low. Furthermore, when the conductive particles are provided with an insulating resin layer or insulating resin particles on the surface, or when the conductive particles are dispersed in the resin and used as an anisotropic conductive material, the conductive particles may cause protrusions. The resin between the conductive particles and the electrode 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 conductive layer by electroless plating after attaching a core substance to the surface of the base particles, and by electroless plating on the surface of the base particles Examples of the method include forming a conductive layer, then attaching a core substance, and further forming a conductive layer by electroless plating.

  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. 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 conductive material constituting the core material include conductive non-metals 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 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 conductive particles 11, the conductive particles according to the present invention preferably include an insulating resin layer or insulating resin particles attached to the surface of the palladium layer. In this case, when the conductive particles are used for connection between the electrodes, a short circuit between adjacent electrodes can be prevented. Specifically, when a plurality of conductive particles are in contact with each other, an insulating 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. Note that the insulating resin between the conductive layer of the conductive particles and the electrode can be easily removed by pressurizing the conductive particles with the two electrodes when connecting the electrodes. When the conductive particles have protrusions on the surface of the palladium layer, the insulating resin layer or the insulating resin particles between the conductive layer and the electrode of the conductive particles can be more easily eliminated.

  Specific examples of the insulating resin that is the material of the insulating resin layer include polyolefins, (meth) acrylate polymers, (meth) acrylate copolymers, block polymers, thermoplastic resins, crosslinked thermoplastic resins, A thermosetting resin, a water-soluble resin, etc. are 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. Of these, water-soluble resins are preferable, and polyvinyl alcohol is more preferable.

  Examples of the method for attaching the insulating resin layer or the insulating resin particles to the surface of the palladium 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. Among these, since the insulating resin layer or the insulating resin particles are difficult to be detached, a method of attaching the insulating resin layer or the insulating resin particles to the surface of the palladium layer through a chemical bond is preferable.

  The conductive particles according to the present invention more preferably include insulating resin particles attached to the surface of the palladium layer. In this case, when the conductive particles are used for the connection between the electrodes, not only can the short circuit between the laterally adjacent electrodes be further prevented, but also the connection resistance between the connected upper and lower electrodes can be further reduced. Can do.

(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 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 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 content of the said binder resin satisfy | fills the said minimum and upper limit, electroconductive particle can be arrange | positioned efficiently between electrodes and the conduction | electrical_connection reliability between electrodes can be improved further.

  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 a connection object member using the conductive particle which concerns on this invention, or anisotropic conductive material containing this electroconductive particle and 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. A connection structure formed of an anisotropic conductive material containing conductive particles or the conductive particles and a binder resin is preferable. 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. Instead of the conductive particles 1, conductive particles 11 may be used.

  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)
(1) Resin particle forming step To 800 parts by weight of an aqueous solution containing 3% by weight of polyvinyl alcohol (“GH-20” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), 70 parts by weight of divinylbenzene, 30 parts by weight of trimethylolpropane trimethacrylate, 2 parts by weight of benzoyl peroxide was added, stirred and mixed. While stirring in a nitrogen atmosphere, the mixture was heated to 80 ° C. and reacted for 15 hours to obtain resin particles.

  The obtained resin particles were washed with distilled water and methanol, and then classified to obtain resin particles having an average particle size of 4.1 μm and a coefficient of variation of 5.0%.

(2) Electroless copper plating step After 10 g of the obtained resin particles were etched, they were washed with water. Next, palladium sulfate was added to the resin particles to adsorb palladium ions to the resin particles.

  Next, resin particles adsorbed with palladium ions were added to an aqueous solution containing 0.5% by weight of dimethylamine borane to activate palladium. Distilled water (500 mL) was added to the resin particles to obtain a particle suspension.

  It also contains 40 g / L copper sulfate (pentahydrate), 100 g / L ethylenediaminetetraacetic acid (EDTA), 50 g / L sodium gluconate, and 25 g / L formaldehyde, and has a pH of 10.5. An electroless plating solution adjusted to 1 was prepared. The electroless plating solution was gradually added to the particle suspension, and electroless copper plating was performed while stirring at 50 ° C. Thus, copper plating particles having a copper layer provided on the surface were obtained.

(3) Electroless palladium plating step 10 g of the obtained copper plating particles were dispersed in 500 mL of ion-exchanged water using an ultrasonic treatment machine to obtain a particle suspension.

  Further, it contains 4 g / L of palladium sulfate (anhydride), 2.4 g / L of ethylenediamine, 4.0 g / L of hydradium sulfate, and 3.5 g / L of sodium hypophosphite, and has a pH of 10 An electroless plating solution adjusted to 1 was prepared. While stirring the particle suspension at 50 ° C., the electroless plating solution was gradually added to perform electroless palladium plating. The amount of electroless plating solution added was adjusted so that the thickness of the palladium layer was 10 nm. The obtained palladium-plated resin particles were washed with distilled water and methanol and then vacuum-dried. Thus, the electroconductive particle by which the copper layer was provided in the surface of the resin particle and the palladium layer was provided in the surface of the copper layer was obtained.

(4) Chlorine washing removal step 1 g of the obtained conductive particles were dispersed in 1000 mL of distilled water (specific resistance 18 MΩ), placed in an autoclave with a stirrer, and stirred and washed at 121 ° C. for 10 hours under a pressure of 0.1 MPa.
Then, it filtered and dried and obtained the electroconductive particle washed.

(Examples 2 to 7)
In the same manner as in Example 1 except that the amount of electroless plating solution added in the electroless palladium plating step was adjusted so that the thickness of the palladium layer was as shown in Table 1 below, copper was applied to the surface of the resin particles. Washed conductive particles provided with a layer and a palladium layer on the surface of the copper layer were obtained.

(Example 8)
(1) Core substance adhesion process The resin particles 10g obtained in Example 1 were etched and then washed with water. Next, palladium sulfate was added to the resin particles to adsorb palladium ions to the resin particles.

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

(2) Production of conductive particles Resin particles were subjected to an electroless copper plating step, an electroless palladium plating step and a chlorine washing removal step in the same manner as in Example 1 except that resin particles to which a core substance was attached were used. Washed conductive particles having a copper layer provided on the surface of the particles and a palladium layer provided on the surface of the copper layer were obtained. The obtained conductive particles had protrusions on the surface of the palladium layer.

Example 9
Resin particles are copolymerized resin particles of 1,4-butanediol diacrylate and tetramethylolmethane tetraacrylate (1,4-butanediol diacrylate: tetramethylolmethane tetraacrylate = 95 wt%: 5 wt%). Except having changed, it carried out similarly to Example 8, and obtained electroconductive particle. The obtained conductive particles had protrusions on the surface of the palladium layer.

(Example 10)
(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- Ion exchange of a monomer composition containing 1 mmol of trimethyl-N-2-methacryloyloxyethylammonium chloride and 1 mmol of 2,2′-azobis (2-amidinopropane) dihydrochloride so that the solid content is 5% by weight After weighing in water, the mixture was stirred at 200 rpm and polymerized at 70 ° C. for 24 hours in 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 9 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%.

(Example 11)
Resin particles are copolymerized resin particles of 1,4-butanediol diacrylate and tetramethylolmethane tetraacrylate (1,4-butanediol diacrylate: tetramethylolmethane tetraacrylate = 95 wt%: 5 wt%). Except having changed, it carried out similarly to Example 1, and obtained electroconductive particle.

(Example 12)
Except having changed the electroconductive particle obtained in Example 9 into the electroconductive particle obtained in Example 1, it carried out similarly to Example 10, and obtained the electroconductive particle to which the insulating resin particle was adhered.

(Example 13)
Except having changed the electroconductive particle obtained in Example 9 into the electroconductive particle obtained in Example 8, it carried out similarly to Example 10, and obtained the electroconductive particle to which the insulating resin particle was adhered.

(Example 14)
Except having changed the electroconductive particle obtained in Example 9 into the electroconductive particle obtained in Example 11, it carried out similarly to Example 10, and obtained the electroconductive particle to which the insulating resin particle was adhered.

(Comparative Example 1)
10 g of the copper plating particles obtained in Example 1 were dispersed in 500 mL of ion-exchanged water using an ultrasonic processor to obtain a particle suspension. While stirring this particle suspension at 50 ° C., an electroless plating solution containing 2.4 g / L ethylenediamine and 3.5 g / L sodium hypophosphite and adjusted to pH 10 was gradually added. It was added and electroless palladium plating was performed. The addition amount of the electroless plating solution was adjusted to an amount capable of forming a 10 nm thick palladium layer. As a result, no palladium layer was formed on the surface of the copper layer.

(Comparative Example 2)
In Comparative Example 2, a catalyzing step for attaching a palladium catalyst to the surface of the copper layer was performed.

  10 g of the copper plating particles obtained in Example 1 were dispersed in a catalyst solution containing palladium ions at 25 ° C., and stirred for 30 minutes to attach palladium ions to the surface of the copper layer. Thereafter, 10 g of copper plating particles having palladium ions attached to the surface thereof were dispersed in 500 mL of ion-exchanged water using an ultrasonic treatment machine to obtain a particle suspension.

  In addition, an electroless plating solution containing 2.4 g / L of ethylenediamine and 3.5 g / L of sodium hypophosphite and adjusted to pH 10 was prepared. While stirring the particle suspension at 50 ° C., the electroless plating solution was gradually added to perform electroless palladium plating. The amount of electroless plating solution added was adjusted so that the thickness of the palladium layer was 10 nm. The obtained palladium-plated resin particles were washed with distilled water and methanol and then vacuum-dried. Thus, the electroconductive particle by which the copper layer was provided in the surface of the resin particle and the palladium layer was provided in the surface of the copper layer was obtained.

  About the obtained electroconductive particle, it carried out similarly to Example 1, the chlorine washing | cleaning removal process was performed, and the wash | cleaned electroconductive particle was obtained.

(Comparative Example 3)
In the electroless palladium plating step, washed conductive particles were obtained in the same manner as in Example 1 except that the amount of the electroless plating solution was adjusted so that the thickness of the palladium layer was 1 nm.

(Evaluation)
(1) Plating state of palladium layer The plating state of the palladium layer in 50 conductive particles was observed with a scanning electron microscope. The results are shown in Table 1 below, where “○” indicates that the entire area of the copper layer is covered with the palladium layer, and “x” indicates that the entire area of the copper layer is not covered with the palladium layer. Indicated.

(2) Concentration of eluted copper ions 100 parts by weight of a plurality of conductive particles were immersed in 1000 parts by weight of 0.001N nitric acid at 25 ° C. for 1 minute. Using an ICP emission spectrometer (“ULTIMA2” manufactured by HORIBA), the concentration of copper ions eluted in the liquid after immersion was measured. The eluted copper ion concentration (ppm / cm ² ) per unit surface area of the conductive particles was determined.

(3) Connection resistance Two substrates on which copper electrodes with L / S of 100 μm / 100 μm were formed were prepared. Further, an anisotropic conductive paste containing 10 parts by weight of conductive particles, 85 parts by weight of an epoxy resin (“Stractbond XN-5A” manufactured by Mitsui Chemicals, Inc.) as a binder resin, and 5 parts by weight of an imidazole type curing agent. 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 allowed to stand for 100 hours at 85 ° C. and a humidity of 85%. The connection resistance between the electrodes of the connection structure after being allowed to stand was measured by the four-terminal method, and the obtained measured value was used as the connection resistance after the high temperature and high humidity test.

(4) Insulation resistance As shown in FIG. 4, comb-shaped electrode copper patterns 31 and 32 having a L / S of 20 μm / 20 μm, in which a nickel plating layer and a gold plating layer are sequentially formed, are formed on the surface of the copper electrode. A prepared substrate was prepared. Further, an anisotropic conductive paste containing 10 parts by weight of conductive particles, 85 parts by weight of an epoxy resin (“Stractbond XN-5A” manufactured by Mitsui Chemicals, Inc.) as a binder resin, and 5 parts by weight of an imidazole type curing agent. Prepared.

  After an anisotropic conductive paste was applied to the upper surfaces of the copper patterns 31 and 32 of the substrate, an alkali-free glass plate was laminated and pressure-bonded to bring the conductive particles into contact with the copper patterns 31 and 32. In the state which laminated | stacked the alkali free glass plate, the anisotropic conductive paste was hardened by heating at 180 degreeC for 1 minute, and the connection structure was obtained.

  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 to stand for 1000 hours under the conditions of 85 ° C. and 85% humidity while applying a bias voltage of 50 V between the electrodes. 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 measurement value was taken as the insulation resistance after the high temperature and high humidity test.

  The results are shown in Table 1 below.

DESCRIPTION OF SYMBOLS 1 ... Conductive particle 2 ... Base particle 2a ... Surface 3 ... Copper layer 3a ... Surface 4 ... Palladium layer 4a ... Surface 11 ... Conductive particle 11a ... Surface 12 ... Copper layer 12a ... Surface 13 ... Palladium layer 13a ... Surface 14 ... Core material 15 ... Protrusion 16 ... Insulating resin particle 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 31 , 32 ... comb electrode copper pattern

Claims (6)

A base material particle, a copper layer provided on the surface of the base material particle, and a palladium layer provided on the surface of the copper layer,
The palladium layer has an average thickness of 5 to 500 nm;
When 100 parts by weight of the plurality of conductive particles are immersed in 1,000 parts by weight of 0.001N nitric acid at 25 ° C. for 1 minute, the copper ion concentration to be eluted is 5 ppm / cm ² or less per unit surface area of the conductive particles. Conductive particles.   The electroconductive particle of Claim 1 which has a processus | protrusion on the outer surface of the said palladium layer.   The electroconductive particle of Claim 1 or 2 provided with the insulating resin layer or insulating resin particle adhering to the surface of the said palladium layer.   The electroconductive particle of Claim 3 provided with the insulating resin particle attached to the surface of the said palladium layer.   The anisotropic conductive material containing the electroconductive particle of any one of Claims 1-4, 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 1-4, or this electroconductive particle and binder resin.

Images