JP5584615B2 - Conductive particles, anisotropic conductive materials, and connection structures - Google Patents

Description

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

  Conductive particles are used for connection between an IC chip and a flexible printed circuit board, connection between liquid crystal driving IC chips, connection between an IC chip and a circuit board having an ITO electrode, and the like. For example, after the conductive particles are arranged between the electrode of the IC chip and the electrode of the circuit board, the electrodes can be electrically connected by bringing the conductive particles into contact with the electrodes by heating and pressurization.

  The conductive particles are dispersed in a binder resin and are also used as an anisotropic conductive material.

  As an example of the conductive particles, Patent Document 1 listed below includes resin particles, a nickel plating layer covering the surface of the resin particles, and a solder layer covering the surface of the nickel plating layer. Conductive particles are disclosed.

  Patent Literature 2 below discloses conductive particles including resin particles and a copper layer provided on the surface of the resin particles. Patent Document 2 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-A-9-306231 JP 2003-323813 A

  The conductive particles described in Patent Document 1 are not used by being dispersed in a binder resin. This is because the conductive particles have a large particle size, and thus the conductive particles are not preferable for dispersing the conductive particles in a binder resin and using them as an anisotropic conductive material. In the example of Patent Document 1, the surface of resin particles having a particle size of 650 μm is coated with a conductive layer, and conductive particles having a particle size of several hundreds of μm are obtained. It is not used as a mixed anisotropic conductive material.

  In patent document 1, when connecting between the electrodes of the connection object member using conductive particles, after placing one conductive particle on one electrode and then placing the electrode on the conductive particle, Heating. By heating, the solder layer is melted and joined to the electrode. However, the operation of placing conductive particles on the electrode is complicated. Further, since there is no resin layer between the connection target members, the connection reliability is low.

  As described in Patent Document 2, in the conductive particles having a copper layer on the surface, when the conductive particles are stored for a long time or when the conductive particles are exposed to high temperature and high humidity, the copper layer is May oxidize. When the electrodes are electrically connected using conductive particles in which the copper layer is oxidized, the connection resistance is increased.

  Therefore, in the anisotropic conductive material including the conductive particles described in Patent Document 2, in the connection structure using the anisotropic conductive material for connection between the electrodes, conduction reliability may be low.

  An object of the present invention is to use conductive particles that can be easily connected to each other and further improve conduction reliability when used for connection between electrodes in a connection structure, and the conductive particles. An anisotropic conductive material and a connection structure are provided.

  According to a wide aspect of the present invention, conductive particles dispersed and used in a binder resin, disposed on the surface of the substrate particle and the substrate particle, and having a single layer structure or 2 A first conductive layer having a laminated structure of more than one layer, and a second conductive layer disposed on the outer surface of the first conductive layer, wherein the first conductive layer has a single layer structure And the second conductive layer has a higher ionization tendency than the first conductive layer, and the second conductive layer has a melting point higher than that of the first conductive layer. When the first conductive layer has a laminated structure of two or more layers, the ionization tendency of the second conductive layer is larger than the ionization tendency of the outermost layer of the first conductive layer, and Conductive particles in which the melting point of the second conductive layer is lower than the melting point of the outermost layer of the first conductive layer. It is subjected.

  In a specific aspect of the conductive particles according to the present invention, when the first conductive layer has a single-layer structure, the first conductive layer is a copper layer, and the first conductive layer is When it has a laminated structure of two or more layers, the outermost layer of the first conductive layer is a copper layer.

  In another specific aspect of the conductive particle according to the present invention, the melting point of the second conductive layer is 300 ° C. or lower.

  In still another specific aspect of the conductive particle according to the present invention, the second conductive layer is a layer containing tin.

  The average particle diameter of the conductive particles according to the present invention is preferably 0.1 μm or more and 100 μm or less. The average particle diameter of the conductive particles according to the present invention is more preferably 0.1 μm or more and 50 μm or less. The substrate particles are preferably resin particles.

  The anisotropic conductive material according to the present invention includes a binder resin and conductive particles dispersed in the binder resin and configured according to the present invention.

  In a specific aspect of the anisotropic conductive material according to the present invention, a flux is further included.

  The connection structure according to the present invention includes a first connection target member, a second connection target member, and a connection part that electrically connects the first and second connection target members. The connecting portion is formed of an anisotropic conductive material in which conductive particles configured according to the present invention are dispersed in a binder resin.

  In the conductive particles according to the present invention, a single-layer or multilayer first conductive layer is disposed on the surface of the base particle, and the second conductive layer is formed on the outer surface of the first conductive layer. When the first conductive layer has a single-layer structure, the ionization tendency of the second conductive layer is larger than the ionization tendency of the first conductive layer, and the first conductive layer has a single-layer structure. When the melting point of the second conductive layer is lower than the melting point of the first conductive layer and the first conductive layer has a laminated structure of two or more layers, the ionization tendency of the second conductive layer is Since the ionization tendency of the outermost layer of the first conductive layer is larger and the melting point of the second conductive layer is lower than the melting point of the outermost layer of the first conductive layer, oxidation of the conductive layer can be suppressed. . Therefore, when used for connection between electrodes in the connection structure, conduction reliability can be improved.

  Furthermore, since the electroconductive particle which concerns on this invention is disperse | distributed and used in binder resin, when it uses for the connection between the electrodes in a connection structure, the connection between electrodes is easy.

FIG. 1 is a cross-sectional view showing conductive particles according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view showing conductive particles according to the second embodiment of the present invention. FIG. 3 is a front sectional view schematically showing a connection structure using an anisotropic conductive material including conductive particles and a binder resin according to the first embodiment of the present invention. 4 is an enlarged front sectional view showing a connection portion between the conductive particles and the electrodes in the connection structure shown in FIG.

  Hereinafter, the present invention will be described in detail.

  The conductive particles according to the present invention are used by being dispersed in a binder resin. The conductive particles according to the present invention include base particles, a first conductive layer disposed on the surface of the base particles, and having a one-layer structure or a laminated structure of two or more layers; And a second conductive layer disposed on the outer surface of the first conductive layer. The conductive layer may have a single-layer structure or a stacked structure of two or more layers. The first conductive layer may be a single layer or a multilayer.

  When the first conductive layer has a single-layer structure, the ionization tendency of the second conductive layer is larger than the ionization tendency of the first conductive layer, and the melting point of the second conductive layer. Is lower than the melting point of the first conductive layer. When the first conductive layer has a laminated structure of two or more layers, the ionization tendency of the second conductive layer is larger than the ionization tendency of the outermost layer of the first conductive layer, and the second The melting point of the conductive layer is lower than the melting point of the outermost layer of the first conductive layer.

  Since the ionization tendency of the second conductive layer is larger than the ionization tendency of the first conductive layer (in the case of a single layer) or the outermost layer (in the case of a multilayer) of the first conductive layer, the second conductive layer The conductive layer itself has a property that oxidation is more likely to proceed than the first conductive layer. Furthermore, by disposing the second conductive layer on the outer surface of the first conductive layer that is the inner layer, oxidation of the first conductive layer that is the inner layer can be prevented. For this reason, when the anisotropic conductive material containing the electroconductive particle which concerns on this invention is used for the electrical connection of a connection structure, connection resistance can be made low.

  Furthermore, since the melting point of the second conductive layer is lower than the melting point of the first conductive layer (in the case of a single layer) or the outermost layer (in the case of a multilayer) of the first conductive layer, conductive particles are used. When the electrodes in the connection structure are connected by heating, the second conductive layer can be melted before the first conductive layer, or only the second conductive layer can be melted. it can. Therefore, the first conductive layer and the electrode can be more easily brought into contact with each other, the contact area between the second conductive layer and the electrode can be increased, and the connection between the electrodes by the conductive particles can be further improved. It can be done more reliably. Furthermore, the first conductive layer can be brought into contact with the electrode. For this reason, when the connection resistance by the first conductive layer is lower than the connection resistance by the second conductive layer, and when the oxidation of the second conductive layer has further proceeded, the first conductive layer The contact resistance between the electrodes can be further reduced by bringing the electrode into contact with the electrodes. When electrically connecting the electrodes using the conductive particles according to the present invention, the first conductive layer is preferably brought into contact with the electrodes.

  Therefore, the conduction reliability of the connection structure using the conductive particles according to the present invention can be improved.

  Further, the conductive particles according to the present invention are used by being dispersed in a binder resin. The conductive particles according to the present invention are preferably dispersed in a binder resin and used as an anisotropic conductive material. When the anisotropic conductive material is used for the connection between the electrodes in the connection structure, the connection between the electrodes is easy. For example, without disposing conductive particles one by one on the electrode provided on the connection target member, the conductive particles can be formed on the electrode by simply coating or laminating an anisotropic conductive material on the connection target member. Can be placed. Furthermore, after an anisotropic conductive material layer is formed on the connection target member, the other electrodes are stacked on the anisotropic conductive material layer so that the electrodes face each other, and the electrodes are electrically connected. it can. Therefore, the manufacturing efficiency of the connection structure in which the electrodes of the connection target members are connected can be increased. The first conductive layer is preferably brought into contact with the electrodes when the electrodes are electrically connected. Furthermore, since not only the conductive particles but also the binder resin exists between the connection target members, the connection target members can be firmly adhered, and the connection reliability can be improved.

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

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

  A conductive particle 1 shown in FIG. 1 includes a base particle 2, a first conductive layer 3, and a second conductive layer 4. The conductive particles 1 are used by being dispersed in a binder resin.

  The first conductive layer 3 is disposed on the surface 2 a of the base particle 2. The first conductive layer 3 covers the surface 2 a of the base particle 2. In the conductive particles 1, the first conductive layer 3 is directly laminated on the surface 2 a of the base particle 2. The first conductive layer 3 has a single layer structure. The first conductive layer 3 is an inner layer.

  The second conductive layer 4 is disposed on the outer surface 3 a of the first conductive layer 3. The second conductive layer 4 is directly laminated on the outer surface 3 a of the first conductive layer 3. The second conductive layer 4 covers the outer surface 3 a of the first conductive layer 3. The second conductive layer 4 has a single layer structure. The second conductive layer 4 is an outer layer.

  In FIG. 2, the electroconductive particle which concerns on the 2nd Embodiment of this invention is shown with sectional drawing.

  A conductive particle 11 shown in FIG. 2 includes a base particle 2, a first conductive layer 12, and a second conductive layer 13. The conductive particles 11 are used by being dispersed in a binder resin. The conductive particles 11 and the conductive particles 1 differ only in the conductive layer.

  The first conductive layer 12 is disposed on the surface 2 a of the base particle 2. The first conductive layer 12 covers the surface 2 a of the base particle 2. The first conductive layer 12 has a multilayer structure of two layers and is a multilayer. The first conductive layer 12 includes an inner conductive layer 21 and an outer conductive layer 22. The outer conductive layer 22 is the outermost layer of the first conductive layer 12. The first conductive layer 12 is an inner layer.

  The second conductive layer 13 is disposed on the outer surface 12 a of the first conductive layer 12. The second conductive layer 13 is directly laminated on the outer surface 12 a of the first conductive layer 12. The second conductive layer 13 is disposed on the surface of the outer conductive layer 22 that is the outermost layer of the first conductive layer 12. The second conductive layer 13 covers the outer surface 12 a of the first conductive layer 12 and the outer surface of the outer conductive layer 22. The second conductive layer 13 has a single layer structure. The second conductive layer 13 is an outer layer.

  Like the conductive particles 1 and 11, the first conductive layer may have a one-layer structure or a two-layer stacked structure. Furthermore, the first conductive layer may have a stacked structure of two or more layers.

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

  The substrate particles are preferably resin particles formed of a resin. When connecting the electrodes, the conductive particles are generally compressed after the conductive particles are arranged between the electrodes. When the substrate particles are resin particles, the conductive particles are easily deformed by compression, and the contact area between the conductive particles and the electrode is increased. For this reason, the conduction | electrical_connection reliability between electrodes can be improved. Furthermore, the flexibility of the conductive particles can be increased when the substrate particles are not particles formed of metal such as nickel or glass but resin particles formed of resin. When the flexibility of the conductive particles is high, damage to the electrode in contact with the conductive particles can be suppressed.

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

  The first and second conductive layers are preferably made of metal. The metal which comprises the 1st, 2nd conductive layer is not specifically limited. Examples of the metal include tin, gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium and cadmium, and alloys thereof. It is done. In addition, tin-doped indium oxide (ITO) can also be used as the metal. As for the said metal, only 1 type may be used and 2 or more types may be used together.

  In addition, the order of ionization tendency of typical metals is magnesium (Mg)> aluminum (Al)> zinc (Zn)> chromium (Cr)> iron (Fe)> cobalt (Co)> nickel (Ni)> tin ( Sn)> lead (Pb)> antimony (Sb)> bismuth (Bi)> copper (Cu)> silver (Ag)> palladium (Pd)> platinum (Pt)> gold (Au).

  The method for forming the first conductive layer on the surface of the substrate particles and the method for forming the second conductive layer on the surface of the first conductive layer are not particularly limited. As a method of forming the first and second conductive layers, for example, a method by electroless plating, a method by electroplating, a method by physical collision, a method by physical vapor deposition, and metal powder or metal powder and binder And a method of coating the surface of the resin particles with a paste containing Of these, electroless plating or electroplating is preferable. Examples of the method by physical vapor deposition include methods such as vacuum vapor deposition, ion plating, and ion sputtering. Further, in the method based on the physical collision, for example, a theta composer or the like is used.

  In the conductive particles according to the present invention, when the first conductive layer has a single layer structure, the first conductive layer is preferably a copper layer or a silver layer, and is preferably a copper layer. More preferred. When the first conductive layer has a laminated structure of two or more layers, the outermost layer of the first conductive layer is preferably a copper layer or a silver layer, and more preferably a copper layer. . In this case, the connection resistance between the electrodes can be further reduced.

  The copper layer and the silver layer also have properties that are relatively easy to oxidize. However, in the conductive particles according to the present invention, when the first conductive layer (in the case of a single layer) or the outermost layer (in the case of a multilayer) of the first conductive layer is a copper layer and a silver layer, the copper layer And since the 2nd conductive layer is arrange | positioned on the surface of a silver layer, the oxidation of a copper layer and a silver layer can be suppressed effectively. In addition, a tin-containing layer or a solder layer can be more easily formed on the surface of these preferable conductive layers.

  From the viewpoint of facilitating the connection between the electrodes and further enhancing the conduction reliability in the connection structure, the melting point of the second conductive layer is preferably 300 ° C. or lower. That is, the second conductive layer is preferably a low melting point conductive layer having a melting point of 300 ° C. or lower. From the viewpoint of further facilitating the connection between the electrodes and further enhancing the conduction reliability in the connection structure, the melting point of the second conductive layer is preferably 100 ° C. or higher, more preferably 280 ° C. or lower, Preferably it is 260 degrees C or less, Especially preferably, it is 240 degrees C or less, Most preferably, it is 220 degrees C or less. From the viewpoint of further facilitating the connection between the electrodes and further enhancing the conduction reliability in the connection structure, the melting point of the second conductive layer is the first conductive layer (in the case of a single layer) or the above It is preferably 5 ° C. or more lower than the melting point of the outermost layer (in the case of a multilayer) of the first conductive layer, preferably 10 ° C. or more, more preferably 20 ° C. or more, and particularly preferably 40 ° C. or more. Preferably, it is most preferably 60 ° C. or lower.

  The second conductive layer is preferably disposed on the entire surface of the first conductive layer. The second conductive layer is preferably laminated directly on the entire surface of the first conductive layer. The second conductive layer preferably covers the entire surface of the first conductive layer. In these cases, the second conductive layer is not partially disposed or laminated on the surface of the first conductive layer and does not partially cover the surface of the first conductive layer. . When the second conductive layer is disposed or laminated on the entire surface of the first conductive layer, the oxidation of the first conductive layer does not easily progress partially. For this reason, the conduction | electrical_connection reliability of a connection structure can fully be improved.

  From the viewpoint of further facilitating the connection between the electrodes and further enhancing the conduction reliability in the connection structure, the second conductive layer is preferably a layer containing tin, and preferably a solder layer. Particularly preferred. The tin-containing layer and the solder layer may be alloy layers. In such conductive particles having the second conductive layer, for example, the contact area between the second conductive layer and the electrode can be increased by melting the second conductive layer by heating. Therefore, when the second conductive layer is a low melting point metal layer, a layer containing tin, or a solder layer, the outer surface layer of the conductive layer is a gold layer or a nickel layer. Compared with conductive particles that are metals other than the solder layer, conduction reliability can be improved.

  The method for forming the second conductive layer on the surface of the first conductive layer is preferably an electroplating method or a physical collision method, more preferably a physical collision method. preferable. The second conductive layer is preferably disposed on the surface of the conductive layer by physical impact. The second conductive layer, the tin-containing layer, or the solder layer is preferably formed by a physical collision method.

  Conventionally, the particle diameter of the conductive particles having a tin-containing layer or a solder layer on the outer surface layer of the conductive layer has been about several hundred μm. This is because even if it is intended to obtain conductive particles having a particle diameter of several tens of μm and the second conductive layer having a tin-containing layer or solder layer, the tin-containing layer or solder layer cannot be formed uniformly. This is because. On the other hand, by using a theta composer, even when conductive particles having a particle size of several tens of μm, particularly a particle size of 0.1 μm or more and a particle size of 50 μm or less are obtained, A layer containing tin or a solder layer can be uniformly formed on the surface of one conductive layer.

  When the second conductive layer is a layer containing tin or a solder layer, the content of tin is preferably less than 85% by weight and more preferably 80% by weight or less in 100% by weight of the second conductive layer. is there. Further, the content of tin in 100% by weight of the second conductive layer is appropriately determined in consideration of the ionization tendency and the melting point. The content of tin in 100% by weight of the second conductive layer is preferably 5% by weight or more, more preferably 10% by weight or more, and still more preferably 20% by weight or more.

  The thicknesses of the first and second conductive layers are each preferably 5 nm or more, more preferably 10 nm or more, still more preferably 20 nm or more, preferably 70 μm or less, more preferably 40 μm or less, and even more preferably 20 μm or less. When the thickness of the first and second conductive layers is not less than the above lower limit, the conductivity is sufficiently high. When the thickness of the first and second conductive layers is not more than the above upper limit, the difference in thermal expansion coefficient between the base particles and the first and second conductive layers becomes small, and the first and second conductive layers Peeling is less likely to occur.

  When the first conductive layer has a laminated structure of two or more layers, the thickness of the outermost layer of the first conductive layer is preferably 3 nm or more, preferably 5 nm or more, more preferably 10 nm or more, and further preferably 20 nm. The thickness is preferably 70 μm or less, more preferably 40 μm or less, still more preferably 20 μm or less, and particularly preferably 5 μm or less. When the thickness of the outermost layer of the first conductive layer is not less than the above lower limit, the conductivity is sufficiently high. When the thickness of the outermost layer of the first conductive layer is not more than the above upper limit, the difference in coefficient of thermal expansion between the base particles and the outermost layer of the first conductive layer becomes small, and the outermost layer of the first conductive layer Peeling is less likely to occur.

  The average particle diameter of the conductive particles is preferably 0.1 μm or more, more preferably 1 μm or more, preferably 100 μm or less, more preferably 80 μm or less, still more preferably 50 μm or less, and particularly preferably 40 μm or less. When the average particle diameter of the conductive particles is not less than the above lower limit and not more than the above upper limit, the contact area between the conductive particles and the electrode is sufficiently large, and aggregated conductive particles are formed when the conductive layer is formed. It becomes difficult. Further, the distance between the electrodes connected via the conductive particles does not become too large, and the conductive layer is difficult to peel from the surface of the base material particles.

  Since the size is suitable for the conductive particles in the anisotropic conductive material and the distance between the electrodes can be further reduced, the average particle diameter of the conductive particles is preferably 0.1 μm or more, more preferably Is 100 μm or less, more preferably 50 μm or less.

  The “average particle size” of the conductive particles indicates a number average particle size. The average particle diameter of the conductive particles can be obtained by observing 50 arbitrary conductive particles with an electron microscope or an optical microscope and calculating an average value.

  The electroconductive particle which concerns on this invention may be equipped with the insulating particle arrange | positioned on the surface of the 2nd electroconductive layer. It is preferable that the number of insulating particles arranged on the surface of the second conductive layer is plural.

  When the conductive particles including the insulating 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, the insulating particles are present between the plurality of electrodes, so that it is possible to prevent a short circuit between electrodes adjacent in the lateral direction instead of between the upper and lower electrodes. Note that, when the conductive particles are pressurized with two electrodes at the time of connection between the electrodes, the insulating particles between the second conductive layer and the electrodes in the conductive particles can be easily excluded.

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

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

  Examples of the method for attaching insulating particles to the surface of the second 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, a method of attaching insulating particles to the surface of the second conductive layer via a chemical bond is preferable because the insulating particles are difficult to be detached.

(Anisotropic conductive material)
The anisotropic conductive material according to the present invention includes a binder resin and the above-described conductive particles dispersed in the binder resin. That is, the conductive particles contained in the anisotropic conductive material according to the present invention include base particles, a first conductive layer disposed on the surface of the base particles, and the first conductive layers. And a second conductive layer disposed on the surface. The ionization tendency of the second conductive layer is greater than the ionization tendency of the first conductive layer (in the case of a single layer) or the outermost layer (in the case of a multilayer) of the first conductive layer. The melting point of the second conductive layer is lower than the melting point of the first conductive layer (in the case of a single layer) or the outermost layer (in the case of a multilayer) of the first conductive layer.

  The anisotropic conductive material according to the present invention is preferably in a liquid state and is preferably an anisotropic conductive paste.

  The binder resin is not particularly limited. As the binder resin, for example, an insulating resin is used. Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, and elastomers. As for the said binder resin, only 1 type may be used and 2 or more types may be used together.

  Specific examples of the vinyl resin include vinyl acetate resin, acrylic resin, and styrene resin. Specific examples of the thermoplastic resin include polyolefin resin, ethylene-vinyl acetate copolymer and polyamide resin. Specific examples of the curable resin include epoxy resins, urethane resins, polyimide resins and unsaturated polyester resins. The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin, or a moisture curable resin. Specific examples of the thermoplastic block copolymer include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated product of styrene-butadiene-styrene block copolymer, and styrene- Examples include hydrogenated products of isoprene-styrene block copolymers. Specific examples of the elastomer include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.

  The binder resin is preferably a thermosetting resin. In this case, the second conductive layer of conductive particles can be melted and the binder resin can be cured by heating when electrically connecting the electrodes. For this reason, the connection between electrodes by a 2nd conductive layer or a 1st conductive layer and the connection of the connection object member by binder resin can be performed simultaneously.

  The anisotropic conductive material according to the present invention preferably contains a curing agent in order to cure the binder resin.

  The said hardening | curing agent is not specifically limited. Examples of the curing agent include imidazole curing agents, amine curing agents, phenol curing agents, polythiol curing agents, and acid anhydride curing agents. As for a hardening | curing agent, only 1 type may be used and 2 or more types may be used together.

  The anisotropic conductive material according to the present invention preferably further contains a flux. By using the flux, an oxide film is hardly formed on the surface of the second conductive layer, and the oxide film formed on the second conductive layer or the electrode surface can be effectively removed.

  The flux is not particularly limited. As the flux, a flux generally used for soldering or the like can be used. Examples of the flux include zinc chloride, a mixture of zinc chloride and an inorganic halide, a mixture of zinc chloride and an inorganic acid, a molten salt, phosphoric acid, a derivative of phosphoric acid, an organic halide, hydrazine, an organic acid, and pine resin. Is mentioned. Only 1 type of flux may be used and 2 or more types may be used together.

  Examples of the molten salt include ammonium chloride. Examples of the organic acid include lactic acid, citric acid, stearic acid, glutamic acid, and hydrazine. Examples of the pine resin include activated pine resin and non-activated pine resin. The flux is preferably rosin. By using rosin, the connection resistance between the electrodes is further reduced.

  The rosin is a rosin composed mainly of abietic acid. The flux is preferably rosins, and more preferably abietic acid. By using this preferable flux, the connection resistance between the electrodes can be further reduced.

  The said flux may be disperse | distributed in binder resin and may adhere on the surface of electroconductive particle.

  The anisotropic conductive material according to the present invention may contain a basic organic compound in order to adjust the activity of the flux. Examples of the basic organic compound include aniline hydrochloride and hydrazine hydrochloride.

  When a curing agent is used, the content of the curing agent is preferably 0.01 parts by weight or more, more preferably 0.1 parts by weight or more, preferably 100 parts by weight or less with respect to 100 parts by weight of the binder resin. More preferably, it is 50 parts by weight or less. When the content of the curing agent is not less than the above lower limit and not more than the above upper limit, the binder resin can be sufficiently cured, and a residue derived from the curing agent is less likely to occur after curing.

  In 100% by weight of the anisotropic conductive material, the content of the conductive particles is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and preferably 20% by weight or less. When the content of the conductive particles is not less than the above lower limit and not more than the above upper limit, short-circuiting between adjacent electrodes can be further prevented, and conduction reliability between the electrodes can be further enhanced.

  In 100% by weight of the anisotropic conductive material, the content of the flux is 0% by weight or more, preferably 0.5% by weight or more, preferably 30% by weight or less, more preferably 25% by weight or less. The anisotropic conductive material may not contain a flux. If the flux content is not less than the above lower limit and not more than the above upper limit, an oxide film is more difficult to be formed on the surface of the second conductive layer, and further, an oxide film formed on the surface of the second conductive layer or electrode. Can be more effectively removed.

  The anisotropic conductive material according to the present invention includes, for example, a filler, an extender, a softener, a plasticizer, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, Various additives such as a lubricant, an antistatic agent or a flame retardant may be further 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 the method for dispersing the conductive particles in the binder resin include, for example, 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 or an organic solvent. After uniformly dispersing using a homogenizer, etc., adding into a binder resin, kneading and dispersing with a planetary mixer, etc., and after diluting the binder resin with water or an organic solvent, the conductive particles are The method of adding, kneading | mixing with a planetary mixer etc., and dispersing 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 containing the conductive particles of the present invention is used as a film-like adhesive such as an anisotropic conductive film or an anisotropic conductive sheet, the film-like shape containing the conductive particles is used. A film-like adhesive that does not contain conductive particles may be laminated on the adhesive. However, as described above, the anisotropic conductive material according to the present invention is preferably in a liquid state, and is preferably an anisotropic conductive paste.

(Connection structure)
A connection structure can be obtained by connecting the connection target members using the anisotropic conductive material according to the present invention.

  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 part is preferably formed of the anisotropic conductive material according to the present invention. The connecting portion is preferably formed by curing the anisotropic conductive material according to the present invention.

  FIG. 3 is a front sectional view schematically showing a connection structure using an anisotropic conductive material including conductive particles according to the first embodiment of the present invention.

  A connection structure 51 shown in FIG. 3 includes a first connection target member 52, a second connection target member 53, and a connection portion that electrically connects the first and second connection target members 52 and 53. 54. The connection portion 54 is formed by curing an anisotropic conductive material including the conductive particles 1 and the binder resin. In FIG. 3, the conductive particles 1 are schematically shown for convenience of illustration.

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

  The manufacturing method of the connection structure is not particularly limited. As an example of the manufacturing method of the connection structure, the anisotropic conductive material is disposed between the first connection target member and the second connection target member to obtain a laminate, and then the laminate is heated. And a method of applying pressure. By heating and pressurizing, the second conductive layer 4 of the conductive particles 1 is melted, and the electrodes 52 b and 53 b are electrically connected by the conductive particles 1. At this time, the first conductive layer 3 is preferably brought into contact with the electrodes 52b and 53b. When the binder resin is a thermosetting resin, the binder resin is cured, and the first and second connection target members 52 and 53 are connected by the cured binder resin.

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.

  FIG. 4 is an enlarged front sectional view of a connection portion between the conductive particles 1 and the electrodes 52b and 53b in the connection structure 51 shown in FIG. As shown in FIG. 4, in the connection structure 51, after the second conductive layer 4 of the conductive particles 1 is melted by heating and pressurizing the laminated body, the melted second conductive layer portion 4a is The electrode 52b and 53b are in sufficient contact. That is, by using the conductive particles 1 whose surface layer is the second conductive layer 4, the second conductive layer 4 can be quickly melted, and the contact area between the conductive particles 1 and the electrodes 52b and 53b. Can be increased. For this reason, the conduction | electrical_connection reliability of the connection structure 51 can be improved. Moreover, the contact resistance between electrodes can be made still lower by making the 1st conductive layer 3 contact the electrodes 52b and 53b. In general, the flux is gradually deactivated by heating.

  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) Production of conductive particles Divinylbenzene resin particles having an average particle diameter of 10 μm (“Micropearl SP-210” manufactured by Sekisui Chemical Co., Ltd.) are electroless nickel-plated, and a base having a thickness of 0.3 μm is formed on the surface of the resin particles. A nickel plating layer was formed. Next, the resin particles on which the base nickel plating layer was formed were subjected to electrolytic copper plating to form a copper layer having a thickness of 1 μm to obtain particles. Thereafter, using a theta composer (manufactured by Tokuju Kogakusha Co., Ltd.), on the surface of the copper layer of the obtained particles, solder fine powder (average particle diameter of 3 μm including 42 wt% tin and 58 wt% bismuth) is applied. By melting, a 2 μm thick solder layer was formed on the surface of the copper layer.

  In this way, conductive particles having a 1 μm thick copper layer formed on the surface of the resin particles and a 2 μm thick solder layer (42% by weight of tin) formed on the surface of the copper layer. Produced.

  The melting point of the copper layer as the first conductive layer was 1084 ° C. The melting point of the solder layer as the second conductive layer was 138 ° C.

(2) Production of anisotropic conductive material A Conductive particles A immediately after production were prepared.

  100 parts by weight of TEPIC-PAS B22 (manufactured by Nissan Chemical Industries, specific gravity 1.4) as a binder resin, 15 parts by weight of TEP-2E4MZ (manufactured by Nippon Soda Co., Ltd.) as a curing agent, and 5 parts by weight of weakly active rosin After blending and adding 10 parts by weight of conductive particles A immediately after preparation, the mixture was stirred at 2000 rpm for 5 minutes using a planetary stirrer to obtain anisotropic conductive material A as an anisotropic conductive paste.

(3) Production of anisotropic conductive material B Conductive particles A immediately after production were stored at 85 ° C. and 85% humidity for 500 hours to obtain conductive particles B after storage.

  The anisotropic conductive material B, which is an anisotropic conductive paste, is prepared in the same manner as the anisotropic conductive material A except that the conductive particles A immediately after the preparation are changed to the conductive particles B after storage. Got.

(Example 2)
Conductive particles and anisotropic conductive material in the same manner as in Example 1 except that the resin particles were changed to divinylbenzene resin particles (“Micropearl SP-220” manufactured by Sekisui Chemical Co., Ltd.) having an average particle diameter of 20 μm. A and B were obtained.

(Example 3)
Conductive particles and anisotropic conductive material A were the same as in Example 1 except that the resin particles were changed to divinylbenzene resin particles having an average particle diameter of 30 μm (“Micropearl-SP230” manufactured by Sekisui Chemical Co., Ltd.). , B was obtained.

Example 4
Same as Example 3 except that the thickness of the copper layer formed by electrolytic copper plating was changed from 1 μm to 2.5 μm, and the amount of solder fine powder was increased to change the thickness of the solder layer from 2 μm to 5 μm. Thus, conductive particles and anisotropic conductive materials A and B were obtained.

(Example 5)
Solder fine powder (42% by weight of tin and 58% by weight of bismuth, average particle diameter of 3 μm) was changed to a fine powder of solder (78% by weight of tin and 22% by weight of bismuth, average particle diameter of 3 μm) Except that, conductive particles and anisotropic conductive materials A and B were obtained in the same manner as Example 1.

  The melting point of the copper layer as the first conductive layer was 1084 ° C. The melting point of the solder layer (containing 78 wt% tin) as the second conductive layer was 138 ° C.

(Comparative Example 1)
Solder particles (tin: bismuth = 43 wt%: 57 wt%, average particle diameter of 15 μm) were prepared. Anisotropic conductive materials A and B were obtained in the same manner as in Example 1 except that the solder particles were used.

(Comparative Example 2)
Electroless nickel plating was performed on divinylbenzene resin particles having an average particle diameter of 10 μm (manufactured by Sekisui Chemical Co., Ltd., Micropearl SP-210) to form a base nickel plating layer having a thickness of 0.3 μm on the surface of the resin particles. Next, the resin particles on which the base nickel plating layer was formed were subjected to electroless nickel plating to form a nickel layer having a thickness of 1 μm to obtain particles. Then, using a theta composer (manufactured by Tokuju Kogakusha Co., Ltd.), the solder powder (containing 42% by weight of tin and 58% by weight of bismuth and having an average particle diameter of 3 μm) is melted on the surface of the nickel layer of the obtained particles. Thus, a 2 μm thick solder layer was formed on the surface of the nickel layer.

  In this way, conductive particles were produced in which a nickel layer having a thickness of 1 μm was formed on the surface of the resin particles, and a solder layer having a thickness of 2 μm was formed on the surface of the nickel layer.

  The melting point of the nickel layer as the first conductive layer was 1455 ° C. The melting point of the solder layer as the second conductive layer was 138 ° C. Anisotropic conductive materials A and B were obtained in the same manner as in Example 1 except that the obtained conductive particles were used.

(Comparative Example 3)
Electroless nickel plating was performed on divinylbenzene resin particles having an average particle diameter of 10 μm (manufactured by Sekisui Chemical Co., Ltd., Micropearl SP-210) to form a base nickel plating layer having a thickness of 0.3 μm on the surface of the resin particles. Next, the resin particles on which the base nickel plating layer was formed were subjected to electrolytic copper plating to form a copper layer (single layer) having a thickness of 3 μm. A solder layer was not formed on the surface of the copper layer.

  Thus, the electroconductive particle in which the copper layer with a thickness of 3 micrometers was formed on the surface of the resin particle was produced. Anisotropic conductive materials A and B were obtained in the same manner as in Example 1 except that the obtained conductive particles were used.

(Evaluation)
(1) Production of connection structure A An FR-4 substrate having a gold electrode pattern with an L / S of 200 μm / 200 μm formed on the upper surface was prepared. In addition, a polyimide substrate (flexible substrate) having a gold electrode pattern with L / S of 200 μm / 200 μm formed on the lower surface was prepared.

  After stirring the obtained anisotropic conductive material A on the upper surface of the FR-4 substrate, the thickness becomes three times the average particle diameter of the conductive particles contained in the anisotropic conductive material A. Was applied to form an anisotropic conductive material layer.

  Next, a polyimide substrate (flexible substrate) was laminated on the upper surface of the anisotropic conductive material layer so that the electrodes face each other. Then, while adjusting the temperature of the head so that the temperature of the anisotropic conductive material layer is 185 ° C., a pressure heating head is placed on the upper surface of the semiconductor chip and a pressure of 2.0 MPa is applied to apply the anisotropic conductive material. The material layer was cured at 185 ° C. to obtain a connection structure A using the anisotropic conductive material A.

(2) Production of connection structure B Connection structure except that anisotropic conductive material A containing conductive particles A immediately after production was changed to anisotropic conductive material B containing conductive particles B after storage In the same manner as A, a connection structure B using an anisotropic conductive material B was obtained.

(3) Conduction reliability (conductivity test between upper and lower electrodes)
The connection resistance between the upper and lower electrodes of the obtained connection structure A was measured by a four-terminal method. The average value of the two connection resistances was calculated. Furthermore, the connection resistance between the upper and lower electrodes of the obtained connection structure B was measured by a four-terminal method. The average value of the two connection resistances was calculated.

  Note that the connection resistance can be obtained by measuring the voltage when a constant current is passed from the relationship of voltage = current × resistance.

  From the connection resistance A (Ω) of the connection structure A using the conductive particles A immediately after production and the connection resistance B (Ω) of the connection structure B using the conductive particles B after storage, The rate of increase ((BA) / A × 100 (%)) was determined. From the rate of increase in connection resistance, the conduction reliability was determined according to the following criteria.

[Judgment criteria for conduction reliability]
○○: Connection resistance increase rate is less than 10% ○: Connection resistance increase rate is 10% or more and less than 30% △: Connection resistance increase rate is 30% or more and less than 50% ×: Connection resistance increase rate 50% or more The results are shown in Table 1 below.

  In addition, in the connection structure using the anisotropic conductive material obtained in Examples 1 to 5, after the solder layer was melted, it was solidified, and the first conductive layer and the electrode were in contact.

DESCRIPTION OF SYMBOLS 1 ... Conductive particle 2 ... Base particle 2a ... Surface 3 ... 1st conductive layer 3a ... Surface 4 ... 2nd conductive layer 4a ... 2nd molten conductive layer part 11 ... Conductive particle 12 ... 1st Conductive layer 12a ... surface 13 ... second conductive layer 21 ... inner first conductive layer 22 ... outer first conductive layer 51 ... connection structure 52 ... first connection target member 52a ... upper surface 52b ... electrode 53 ... 2nd connection object member 53a ... Lower surface 53b ... Electrode 54 ... Connection part

Claims (9)

Conductive particles used dispersed in a binder resin,
Substrate particles,
A first conductive layer disposed on the surface of the substrate particles and having a one-layer structure or a laminated structure of two or more layers;
A second conductive layer disposed on an outer surface of the first conductive layer,
When the first conductive layer has a single-layer structure, the first conductive layer is a copper layer,
When the first conductive layer has a laminated structure of two or more layers, the outermost layer of the first conductive layer is a copper layer,
When the first conductive layer has a single-layer structure, the ionization tendency of the second conductive layer is greater than the ionization tendency of the first conductive layer, and the melting point of the second conductive layer. Is lower than the melting point of the first conductive layer,
When the first conductive layer has a laminated structure of two or more layers, the ionization tendency of the second conductive layer is larger than the ionization tendency of the outermost layer of the first conductive layer, and the second Conductive particles in which the melting point of the conductive layer is lower than the melting point of the outermost layer of the first conductive layer. The melting point of the second conductive layer is 300 ° C. or less, the conductive particles of claim 1. The second conductive layer is a layer containing tin, conductive particle according to claim 1 or 2. The electroconductive particle of any one of Claims 1-3 whose average particle diameter is 0.1 micrometer or more and 100 micrometers or less. The electroconductive particle of Claim 4 whose average particle diameter is 0.1 micrometer or more and 50 micrometers or less. The electroconductive particle of any one of Claims 1-5 whose said base material particle is a resin particle. A binder resin,
And a conductive particle according to any one of claims 1 to 6 which is dispersed in the binder resin, the anisotropic conductive material. The anisotropic conductive material according to claim 7 , further comprising a flux. A first connection target member;
A second connection target member;
A connecting portion electrically connecting the first and second connection target members;
A connection structure in which the connection part is formed of an anisotropic conductive material in which the conductive particles according to any one of claims 1 to 6 are dispersed in a binder resin.

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