Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
  • C09J11/08—Macromolecular additives
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J201/00—Adhesives based on unspecified macromolecular compounds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J9/00—Adhesives characterised by their physical nature or the effects produced, e.g. glue sticks
  • C09J9/02—Electrically-conducting adhesives
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/20—Conductive material dispersed in non-conductive organic material
  • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B5/00—Non-insulated conductors or conductive bodies characterised by their form
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B5/00—Non-insulated conductors or conductive bodies characterised by their form
  • H01B5/16—Non-insulated conductors or conductive bodies characterised by their form comprising conductive material in insulating or poorly conductive material, e.g. conductive rubber
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
  • H01R11/00—Individual connecting elements providing two or more spaced connecting locations for conductive members which are, or may be, thereby interconnected, e.g. end pieces for wires or cables supported by the wire or cable and having means for facilitating electrical connection to some other wire, terminal, or conductive member, blocks of binding posts
  • H01R11/01—Individual connecting elements providing two or more spaced connecting locations for conductive members which are, or may be, thereby interconnected, e.g. end pieces for wires or cables supported by the wire or cable and having means for facilitating electrical connection to some other wire, terminal, or conductive member, blocks of binding posts characterised by the form or arrangement of the conductive interconnection between the connecting locations

Definitions

• the present invention relates to a conductive particle having a base particle and a conductive portion disposed on the surface of the base particle.
• the present invention also relates to a conductive material and a connection structure using the conductive particle.
• Anisotropic conductive materials such as anisotropic conductive paste and anisotropic conductive film are widely known.
• anisotropic conductive materials conductive particles are dispersed in a binder resin.
• the above-mentioned anisotropic conductive materials are used to obtain a variety of connection structures.
• Examples of connections that use the above-mentioned anisotropic conductive materials include connections between flexible printed circuit boards and glass substrates (FOG (Film on Glass)), connections between semiconductor chips and flexible printed circuit boards (COF (Chip on Film)), connections between semiconductor chips and glass substrates (COG (Chip on Glass)), and connections between flexible printed circuit boards and glass epoxy substrates (FOB (Film on Board)).
• conductive particles may be used that have a base particle and a conductive layer disposed on the surface of the base particle.
• Patent Document 1 discloses conductive particles having a conductive layer formed on the surface of core particles.
• the conductive particles have a maximum compression hardness of 22,000 N/mm2 or more, a maximum compression hardness at a compression ratio of less than 5%, and an average compression hardness of the conductive particles at a compression ratio of 20% to 50% of 5,000 N/ mm2 to 18,000 N/ mm2 . Furthermore, the ratio of the maximum compression hardness to the average compression hardness at a compression ratio of 20% to 50% is 2.0 to 10.0.
• the load at which the conductive layer breaks is 3.0 mN or more.
• a conductive particle comprising a base particle and a conductive portion disposed on the surface of the base particle, the conductive portion having two or more conductive layers, at least one of the two or more conductive layers having a melting point greater than 100°C and equal to or less than 400°C, and the ratio of the compressive modulus when the conductive particle is compressed 5% at 25°C to the compressive modulus when the conductive particle is compressed 0.5% at 25°C is 0.40 or greater.
• Item 5 The conductive particles according to any one of Items 1 to 4, wherein the conductive particles have a compressive modulus of 500 N/ mm2 or more and 4000 N/ mm2 or less when compressed by 0.5% at 100°C.
• Item 7 The conductive particle described in any one of Items 1 to 6, wherein the outermost layer of the conductive portion contains indium.
• Item 10 The conductive particles described in any one of Items 1 to 9, wherein the base particles are resin particles.
• Item 11 The conductive particle according to any one of Items 1 to 10 , wherein the base particle has a compressive modulus of 5600 N/mm2 or less when compressed by 5% at 25°C.
• Item 12 A conductive material comprising the conductive particles described in any one of items 1 to 11 and a binder resin.
• a connection structure comprising a first connection target member having a first electrode on its surface, a second connection target member having a second electrode on its surface, and a connection portion connecting the first connection target member and the second connection target member, wherein the material of the connection portion contains the conductive particles described in any one of Items 1 to 11, and the first electrode and the second electrode are electrically connected by the conductive particles.
• the conductive particle according to the present invention comprises a base particle and a conductive portion disposed on the surface of the base particle.
• the conductive portion has two or more conductive layers, and at least one of the two or more conductive layers has a melting point of greater than 100°C and less than 400°C.
• the ratio of the compressive modulus when the conductive particle is compressed 5% at 25°C to the compressive modulus when the conductive particle is compressed 0.5% at 25°C is 0.40 or greater. Because the conductive particle according to the present invention has the above configuration, when used for electrical connection between electrodes, sufficient contact between the electrodes and the conductive particle is possible, improving conductivity reliability.
• FIG. 1 is a cross-sectional view schematically showing a conductive particle according to a first embodiment of the present invention.
• FIG. 2 is a cross-sectional view schematically showing a conductive particle according to a second embodiment of the present invention.
• FIG. 3 is a cross-sectional view schematically showing a conductive particle according to a third embodiment of the present invention.
• FIG. 4 is a cross-sectional view that schematically shows a connection structure using the conductive particles shown in FIG.
• the conductive particle according to the present invention includes a base particle and a conductive portion disposed on the surface of the base particle.
• the conductive portion has two or more conductive layers, and at least one of the two or more conductive layers has a melting point of more than 100°C and not more than 400°C.
• the ratio of the compressive modulus when the conductive particle is compressed 5% at 25°C to the compressive modulus when the conductive particle is compressed 0.5% at 25°C is 0.40 or greater.
• the electrodes and conductive particles may not be in sufficient contact.
• the conductive particles may be too hard to deform sufficiently, resulting in an insufficient contact area between the electrodes and conductive particles.
• the resulting connection structure may have high connection resistance (low conductivity reliability) after a conductivity reliability test under a high-temperature, high-humidity environment.
• the resulting connection structure may have high initial connection resistance between the electrodes.
• the above ratio (5% K value of conductive particles at 25°C/0.5% K value of conductive particles at 25°C) is preferably 1.00 or less, more preferably 0.90 or less, and even more preferably 0.80 or less.
• the ratio (5% K value of conductive particles at 25°C/0.5% K value of conductive particles at 25°C) is equal to or greater than the lower limit, the conductive particles deform appropriately, ensuring a sufficient contact area between the electrode and the conductive particles, thereby further improving conductivity reliability.
• the compressive modulus of the conductive particles when compressed by 5% at 25 ° C. is preferably 1000 N/mm 2 or more, more preferably 1500 N/mm 2 or more, even more preferably 2000 N/mm 2 or more, and particularly preferably 2250 N/mm 2 or more.
• the compressive modulus of the conductive particles when compressed by 5% at 25 ° C. is preferably 15000 N/mm 2 or less, more preferably 12500 N/mm 2 or less, even more preferably 8500 N/mm 2 or less, and particularly preferably 6500 N/mm 2 or less.
• the conductive particles can contact the electrode without being excessively crushed, thereby further improving the conductivity reliability.
• the 5% K value of the conductive particles at 25°C is equal to or less than the upper limit, the conductive particles can be appropriately deformed to ensure a sufficient contact area between the electrode and the conductive particles, thereby further improving the conduction reliability.
• the compressive modulus when the conductive particles are compressed by 5% at 25°C is preferably equal to or greater than the lower limit and equal to or less than the upper limit, and the range can be set by appropriately selecting the lower limit and the upper limit.
• the above ratio (5% K value of conductive particles at 100°C / 0.5% K value of conductive particles at 100°C) is preferably 0.50 or more, more preferably 0.60 or more, even more preferably 0.70 or more, particularly preferably 0.75 or more, and most preferably 0.80 or more.
• the above ratio (5% K value of conductive particles at 100°C / 0.5% K value of conductive particles at 100°C) is preferably 1.20 or less, more preferably 1.10 or less, and even more preferably 1.00 or less.
• the ratio (5% K value of conductive particles at 100°C/0.5% K value of conductive particles at 100°C) be equal to or greater than the lower limit and equal to or less than the upper limit, and the range can be set by appropriately selecting the lower limit and upper limit.
• the compressive modulus of the conductive particles when compressed 0.5% at 100 ° C. (0.5% K value of the conductive particles at 100 ° C.) is preferably 500 N/mm 2 or more, more preferably 1000 N/mm 2 or more, even more preferably 1500 N/mm 2 or more, particularly preferably 2000 N/mm 2 or more, and most preferably 2750 N/mm 2 or more.
• the conductive particles can contact the electrode without being excessively crushed when pressure is applied to the electrode and the conductive particles during mounting, thereby further improving the conductivity reliability.
• the conductive particles can be appropriately deformed to ensure a sufficient contact area between the electrode and the conductive particles, thereby further improving the conduction reliability.
• the compressive modulus of the conductive particles when compressed by 5% at 100°C is preferably equal to or greater than the lower limit and equal to or less than the upper limit, and the range can be set by appropriately selecting the lower limit and the upper limit.
• the 0.5% K value and 5% K value of the above-mentioned conductive particles at 25°C, and the 0.5% K value and 5% K value of the above-mentioned conductive particles at 100°C can be measured as follows.
• the conductive particles are compressed with the smooth end face of a cylindrical indenter (diameter 50 ⁇ m, made of diamond) at 25°C or 100°C under conditions where a maximum test load of 90 mN is applied for 30 seconds.
• the load value (N) and compression displacement (mm) at this time are measured. From the obtained measured values, the compressive elastic modulus can be calculated using the following formula.
• micro-compression testing machines that can be used include the Fischerscope H-100 manufactured by Fischer and the ENT-5 manufactured by Elionix.
• K value (N/mm 2 ) (3/2 1/2 ) ⁇ F ⁇ S -3/2 ⁇ R -1/2
• F Load value (N) when the conductive particles are compressed and deformed by 0.5% or 5%
• S Compression displacement (mm) when the conductive particles are compressed and deformed by 0.5% or 5%
• R Radius of conductive particle (mm)
• the melting point of the first conductive layer 13A and the melting point of the second conductive layer 13B may each be greater than 100°C and less than 400°C
• the melting point of the first conductive layer 13A and the melting point of the third conductive layer 13C may each be greater than 100°C and less than 400°C
• the melting point of the second conductive layer 13B and the melting point of the third conductive layer 13C may each be greater than 100°C and less than 400°C.
• the melting point of the first conductive layer 13A, the melting point of the second conductive layer 13B, and the melting point of the third conductive layer 13C may each be greater than 100°C and less than 400°C.
• base particles examples include resin particles, inorganic particles excluding metal particles, organic-inorganic hybrid particles, and metal particles.
• the base particles may be core-shell particles having a core and a shell disposed on the surface of the core.
• the core may be an organic core.
• the shell may be an inorganic shell.
• the base particles are preferably resin particles, inorganic particles excluding metal particles, or organic-inorganic hybrid particles, more preferably resin particles or organic-inorganic hybrid particles, and even more preferably resin particles.
• non-crosslinkable monomers include styrene-based monomers such as styrene and ⁇ -methylstyrene; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate.
• styrene-based monomers such as styrene and ⁇ -methylstyrene
• carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride
• Examples include polyfunctional (meth)acrylate compounds such as propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate; and silane-containing monomers such as triallyl (iso)cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, ⁇ -(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane.
• silane-containing monomers such as triallyl (iso)cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, ⁇ -(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimeth
• the material of the resin particles contains divinylbenzene or a compound having a (meth)acryloyl group.
• the material of the resin particles may contain divinylbenzene or a compound having a (meth)acryloyl group.
• crosslinking agent When using the above-mentioned crosslinkable monomers to obtain resin particles, a crosslinking agent can be used.
• the crosslinking agent include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate.
• the above-mentioned crosslinking agents may be used alone or in combination of two or more.
• the crosslinking agent is preferably (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, or 1,4-butanediol di(meth)acrylate.
• the resin particles can be obtained by polymerizing the polymerizable monomer having the ethylenically unsaturated group using a known method. Examples of such methods include suspension polymerization in the presence of a radical polymerization initiator, and polymerization using non-crosslinked seed particles to swell the monomer together with a radical polymerization initiator.
• the base particles are inorganic particles other than metal particles or organic-inorganic hybrid particles
• examples of inorganic materials that are the material for the base particles include silica and carbon black. It is preferable that the inorganic material is not a metal.
• the particles formed from silica are not particularly limited, but examples include particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, followed by baking as necessary.
• the organic-inorganic hybrid particles include organic-inorganic hybrid particles formed from a crosslinked alkoxysilyl polymer and an acrylic resin.
• the base particles are metal particles
• examples of the metal particles include silver, copper, nickel, silicon, gold, and titanium.
• the base particles are not metal particles, and it is preferable that they are not copper particles.
• the compressive modulus of the base particle when compressed 0.5% at 25 ° C. (0.5% K value of the base particle at 25 ° C.) is preferably 500 N / mm 2 or more, more preferably 800 N / mm 2 or more, even more preferably 1000 N / mm 2 or more, and particularly preferably 2000 N / mm 2 or more.
• the compressive modulus of the base particle when compressed 0.5% at 25 ° C. (0.5% K value of the base particle at 25 ° C.) is preferably 15,000 N / mm 2 or less, more preferably 10,000 N / mm 2 or less, even more preferably 7,500 N / mm 2 or less, and particularly preferably 6,000 N / mm 2 or less.
• the 0.5% K value of the base particle at 25 ° C. is the above lower limit or more, when electrodes are connected using the resulting conductive particles, the electrodes and conductive particles can be in more effective contact, the initial connection resistance between the electrodes can be further reduced, and the conduction reliability can be further improved.
• the 0.5% K value of the base particle at 25°C is equal to or less than the upper limit, when electrodes are connected using the resulting conductive particles, the electrodes and the conductive particles can maintain contact without being destroyed.
• the 0.5% K value of the base particle at 25°C is preferably equal to or greater than the lower limit and equal to or less than the upper limit, and the range can be set by appropriately selecting the lower limit and the upper limit.
• the compressive modulus of the base particle when compressed 5% at 25 ° C. is preferably 550 N / mm 2 or more, more preferably 850 N / mm 2 or more, even more preferably 1100 N / mm 2 or more, and particularly preferably 2200 N / mm 2 or more.
• the particle diameter of the base particles is preferably 0.1 ⁇ m or more, more preferably 1 ⁇ m or more, even more preferably 1.5 ⁇ m or more, even more preferably 2 ⁇ m or more, particularly preferably 2.5 ⁇ m or more, and most preferably 3.5 ⁇ m or more, and is preferably 500 ⁇ m or less, more preferably 300 ⁇ m or less, even more preferably 50 ⁇ m or less, particularly preferably 30 ⁇ m or less, and most preferably 20 ⁇ m or less.
• the particle diameter of the base particles is above the above lower limit, when the resulting conductive particles are used to connect electrodes, the electrodes and conductive particles can contact more effectively, the initial connection resistance between the electrodes can be further reduced, and the conductivity reliability can be further improved.
• the conductive portion is formed on the surface of the base particles by electroless plating, agglomeration is less likely to occur, and agglomerated conductive particles are less likely to form.
• the particle diameter of the base particles is below the above upper limit, the conductive particles are easily compressed sufficiently, the connection resistance between the electrodes is further reduced, and the gap between the electrodes is further reduced.
• the particle diameter of the base particles refers to the number average particle diameter.
• the particle diameter of the base particles is determined using a particle size distribution analyzer or the like.
• the particle diameter of the base particles is preferably determined by observing 50 random base particles under an electron microscope or optical microscope and calculating the average value. When observed under an electron microscope or optical microscope, the particle diameter of each base particle is determined as the particle diameter in equivalent circle diameter. When observed under an electron microscope or optical microscope, the average particle diameter in equivalent circle diameter of 50 random base particles is approximately equal to the average particle diameter in equivalent sphere diameter. When observed under a particle size distribution analyzer, the particle diameter of each base particle is determined as the particle diameter in equivalent sphere diameter.
• the particle diameter of the base particles is preferably calculated using a particle size distribution analyzer. When measuring the particle diameter of the base particles of conductive particles, it can be measured, for example, as follows.
• the conductive particles are added to Kulzer's Technovit 4000 so that the content is 30% by weight, and dispersed to create an embedding resin for conductive particle inspection.
• An ion milling device (Hitachi High-Technologies Corporation's IM4000) is used to cut out a cross section of the conductive particles dispersed in the embedding resin, passing through the vicinity of the center of the base particle. Then, using a field emission scanning electron microscope (FE-SEM) with an image magnification set to 25,000x, 50 conductive particles are randomly selected and the base particle of each conductive particle is observed. The particle diameter of the base particle for each conductive particle is measured, and the arithmetic average is used to determine the particle diameter of the base particle.
• FE-SEM field emission scanning electron microscope
• At least one of the two or more conductive layers (conductive portions) has a melting point greater than 100°C and equal to or less than 400°C. That is, in the conductive particles, at least one of the two or more conductive layers (conductive portions) has a melting point greater than 100°C and equal to or less than 400°C. In the conductive particles, it is preferable that the melting point of the metal component constituting at least one of the two or more conductive layers (conductive portions) is greater than 100°C and equal to or less than 400°C.
• the conductive layer (X) is preferably a layer other than the innermost layer of the conductive part, and is preferably not in contact with the base particle. It is particularly preferable that the conductive layer (X) is the outermost layer of the conductive part, and it is particularly preferable that the outermost layer of the conductive part is the conductive layer (X). In these cases, immediately after the conductive particles come into contact with the electrode, the conductive particles deform and conform well to the electrode surface, ensuring a sufficient contact area between the electrode and the conductive particles. As a result, conductivity reliability can be further improved.
• Examples of metals contained in the conductive layer (Y) include gold, silver, palladium, copper, platinum, zinc, iron, lead, ruthenium, aluminum, cobalt, nickel, chromium, titanium, antimony, thallium, germanium, cadmium, silicon, and alloys thereof. It is preferable that the conductive layer (Y) contain these metals.
• the metal constituting the conductive layer (Y) may be tin-doped indium oxide (ITO) or solder.
• the metal contained in the conductive layer (Y) may be one type only, or two or more types. When the conductive layer (Y) contains two or more types of metals, the two or more types of metals may be alloyed, or may be contained in the conductive layer (Y) as an alloy.
• the conductive part have a conductive layer (X) and a conductive layer (Y).
• the melting point of the conductive layer (Y) may be 100°C or lower, or may exceed 400°C, but in order to achieve even superior effects of the present invention, it is preferable that the melting point of the conductive layer (Y) exceed 400°C.
• the conductive part may have only the conductive layer (X), or may not have the conductive layer (Y).
• the metal contained in the conductive layer (Y) is preferably nickel, palladium, copper, silver, or gold, and more preferably nickel.
• the conductive layer (Y) preferably contains nickel, palladium, copper, silver, or gold, and more preferably contains nickel.
• the method for forming the conductive portion on the surface of the base particle is not particularly limited.
• methods for forming the conductive portion include electroless plating, electroplating, physical vapor deposition, and coating the surface of the base particle with a metal powder or a paste containing a metal powder and a binder. Electroless plating is preferred as the method for forming the conductive portion, as this is easy to do.
• physical vapor deposition methods include vacuum deposition, ion plating, and ion sputtering.
• the thickness of the conductive portion is preferably 250 nm or more, more preferably 300 nm or more, even more preferably 350 nm or more, even more preferably 400 nm or more, particularly preferably 500 nm or more, and most preferably 600 nm or more, and is preferably 5000 nm or less, more preferably 2000 nm or less, even more preferably 1500 nm or less, and particularly preferably 1000 nm or less.
• the thickness of the conductive portion is the thickness of the entire conductive portion (total thickness of the conductive layer).
• the thickness of the outermost layer of the conductive portion is below the above upper limit, the hardness of the conductive particles (particularly the conductive portion) at the initial stage of mounting becomes appropriate, allowing for contact to be maintained without destruction when pressure is applied to the electrode and conductive particles during mounting.
• the melting point of the outermost layer of the conductive portion exceeds 100°C and that the thickness of the outermost layer of the conductive portion is 300 nm or more and 1000 nm or less.
• the melting point of the outermost layer of the conductive portion may be 400°C or less, or may exceed 400°C.
• the melting point of the outermost layer of the conductive portion is greater than 100°C and 400°C or less, and that the thickness of the outermost layer of the conductive portion is 300 nm or more and 1000 nm or less.
• the ratio of the thickness of the conductive layer (X) having a melting point exceeding 100°C and not exceeding 400°C to the thickness of the conductive portion (total thickness of the conductive portion) is defined as the ratio (thickness of conductive layer (X) / thickness of conductive portion).
• the ratio (thickness of conductive layer (X) / thickness of conductive portion) is preferably 0.20 or more, more preferably 0.35 or more, even more preferably 0.40 or more, particularly preferably 0.50 or more, and most preferably 0.60 or more, and is preferably 1.00 or less, more preferably 0.95 or less, even more preferably 0.90 or less, particularly preferably 0.85 or less, and most preferably 0.80 or less.
• the conductive layer (X) is sufficiently deformed by heating, ensuring a sufficient contact area between the electrode and the conductive particles, thereby further improving conductivity reliability.
• the above ratio (thickness of conductive layer (X)/thickness of conductive portion) is equal to or less than the above upper limit, softening (deformation) of the conductive particles during mounting can be suppressed to a certain level, and a sufficient contact area between the conductive particles and the electrode can be ensured.
• the thickness of the conductive portion and each conductive layer can be measured, for example, by observing the cross section of the conductive particle using a transmission electron microscope (TEM).
• TEM transmission electron microscope
• the content of the metal components having a melting point greater than 100°C and equal to or less than 400°C is equal to or greater than the above lower limit, sufficient conductivity is obtained, and when the resulting conductive particles are used to connect electrodes, the electrodes and conductive particles can make more effective contact, further reducing the initial connection resistance between the electrodes and further increasing the conductivity reliability.
• the content of metal components having a melting point of greater than 100°C and less than 400°C is preferably 0.4% by weight or more, more preferably 0.65% by weight or more, and preferably 100% by weight or less, more preferably 95.0% by weight or less, and even more preferably 90.0% by weight or less.
• the content of metal components having a melting point of greater than 100°C and less than 400°C is equal to or greater than the above lower limit and equal to or less than the above upper limit, sufficient conductivity is obtained, and when the resulting conductive particles are used to connect electrodes, the electrodes and conductive particles can contact more effectively, further reducing the initial connection resistance between the electrodes and further increasing the conductivity reliability.
• a variety of known analytical methods can be used to measure the metal content of the conductive portion.
• methods for measuring the metal content of the conductive portion include absorption spectrometry and spectral analysis.
• absorption spectrometry a flame absorption spectrometer or an electric heating furnace absorption spectrometer can be used.
• spectral analysis include plasma emission spectrometry and plasma ion source mass spectrometry.
• the metal content of the conductive portion can be measured, for example, using an ICP optical emission analyzer.
• ICP optical emission analyzers include the "ICP optical emission analyzer" manufactured by HORIBA.
• the conductive particles preferably have a plurality of protrusions on the outer surface of the conductive portion. Furthermore, the conductive particles preferably include a plurality of core materials in the conductive portion that raise the outer surface of the conductive portion so as to form the plurality of protrusions.
• Methods for forming the protrusions include a method in which a core material is attached to the surface of a base particle and then a conductive portion is formed by electroless plating; a method in which a conductive portion is formed on the surface of a base particle by electroless plating, then a core material is attached, and then a conductive portion is formed by electroless plating; and a method in which a core material is added during the process of forming a conductive portion on the surface of a base particle by electroless plating.
• the core material may be made of conductive or non-conductive materials.
• conductive materials include metals, metal oxides, conductive non-metals such as graphite, and conductive polymers.
• conductive polymers include polyacetylene.
• non-conductive materials include silica, alumina, tungsten carbide, titanium oxide, barium titanate, and zirconia. The metals listed as metals contained in the conductive layer (X) and the conductive layer (Y) can be used as appropriate for the core material.
• the core material examples include barium titanate (Mohs hardness 4.5), nickel (Mohs hardness 5), silica (silicon dioxide, Mohs hardness 6-7), titanium oxide (Mohs hardness 7), zirconia (Mohs hardness 8-9), alumina (Mohs hardness 9), tungsten carbide (Mohs hardness 9), and diamond (Mohs hardness 10).
• the core material is preferably nickel, silica, titanium oxide, zirconia, alumina, tungsten carbide, or diamond, and more preferably silica, titanium oxide, zirconia, alumina, tungsten carbide, or diamond.
• the core material is even more preferably titanium oxide, zirconia, alumina, tungsten carbide, or diamond, and particularly preferably zirconia, alumina, tungsten carbide, or diamond.
• the Mohs hardness of the core material is preferably 4 or higher, more preferably 6 or higher, even more preferably 7 or higher, and particularly preferably 7.5 or higher. When the Mohs hardness of the core material is above the lower limit, the compressive modulus of the conductive particles can be easily controlled within a suitable range.
• the shape of the core substance is not particularly limited.
• the core substance is preferably in the form of a mass.
• Examples of core substances include particulate masses, aggregates formed by aggregating multiple microparticles, and amorphous masses.
• the average particle size of the core material is preferably the number average particle size.
• the average particle size of the core material is determined by observing 50 random core materials under an electron microscope or optical microscope and calculating the average value.
• the number of protrusions per conductive particle is preferably 3 or more, and more preferably 5 or more. There is no particular upper limit to the number of protrusions. The upper limit can be selected appropriately taking into account factors such as the particle diameter of the conductive particles.
• the surface area of the portion where the protrusions are located is preferably 10% or more, more preferably 30% or more, and preferably 95% or less, more preferably 90% or less, of the total surface area (100%) of the conductive particles.
• the average height of the multiple protrusions is preferably 0.001 ⁇ m or more, more preferably 0.05 ⁇ m or more, and preferably 0.9 ⁇ m or less, more preferably 0.5 ⁇ m or less. If the average height of the protrusions is above the above lower limit and below the above upper limit, when used for electrical connection between electrodes, the initial connection resistance can be further reduced, and conductivity reliability can be further improved.
• the conductive particles may or may not include an insulating material disposed on the surface of the conductive portion. From the viewpoint of further reducing the initial connection resistance and further increasing the conduction reliability when electrodes are connected using the conductive particles, it is preferable that the conductive particles do not include an insulating material.
• the insulating material examples include polyolefins, (meth)acrylate polymers, (meth)acrylate copolymers, block polymers, thermoplastic resins, cross-linked thermoplastic resins, thermosetting resins, and water-soluble resins.
• the conductive material according to the present invention includes the conductive particles described above and a binder resin.
• the conductive particles are preferably dispersed in the binder resin when used.
• the conductive particles are preferably dispersed in the binder resin when used as a conductive material.
• the conductive particles are preferably used to obtain an anisotropic conductive material (use of the conductive particles to obtain an anisotropic conductive material).
• the conductive material is preferably an anisotropic conductive material (use of the conductive material to obtain an anisotropic conductive material).
• the conductive particles are preferably used for electrical connection between electrodes (use of the conductive particles for electrical connection between electrodes).
• the conductive material is preferably used for electrical connection between electrodes (use of the conductive material for electrical connection between electrodes).
• the conductive material is preferably used for electrical connection between electrodes (use of the conductive material for electrical connection between electrodes).
• the conductive material is preferably a conductive material for circuit connection (use of the
• binder resin examples include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, and elastomers. Only one type of the binder resins may be used, or two or more types may be used in combination.
• Examples of the vinyl resin include vinyl acetate resin, acrylic resin, and styrene resin.
• examples of the thermoplastic resin include polyolefin resin, ethylene-vinyl acetate copolymer, and polyamide resin.
• examples of the curable resin include epoxy resin, urethane resin, polyimide resin, and 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.
• thermoplastic block copolymer examples include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, and hydrogenated styrene-isoprene-styrene block copolymer.
• the elastomer include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.
• the conductive material may also contain various additives such as fillers, extenders, softeners, plasticizers, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, UV absorbers, lubricants, antistatic agents, and flame retardants.
• additives such as fillers, extenders, softeners, plasticizers, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, UV absorbers, lubricants, antistatic agents, and flame retardants.
• the method for dispersing the conductive particles in the binder resin can be any conventionally known dispersion method and is not particularly limited.
• methods for dispersing the conductive particles in the binder resin include the following: A method in which the conductive particles are added to the binder resin and then kneaded and dispersed using a planetary mixer or the like; A method in which the conductive particles are uniformly dispersed in water or an organic solvent using a homogenizer or the like, then added to the binder resin, and then kneaded and dispersed using a planetary mixer or the like; A method in which the binder resin is diluted with water or an organic solvent, and then the conductive particles are added, and then kneaded and dispersed using a planetary mixer or the like.
• the viscosity ( ⁇ 25) of the conductive material at 25°C is preferably 30 Pa ⁇ s or more, more preferably 50 Pa ⁇ s or more, and preferably 400 Pa ⁇ s or less, more preferably 300 Pa ⁇ s or less.
• the viscosity ( ⁇ 25) can be adjusted appropriately by changing the types and amounts of the ingredients used.
• connection structure can be obtained by connecting electrodes using the conductive particles or a conductive material containing the conductive particles and a binder resin.
• connection structure according to the present invention comprises a first connection target member having a first electrode on its surface, a second connection target member having a second electrode on its surface, and a connection portion connecting the first connection target member and the second connection target member.
• the material of the connection portion contains the conductive particles described above.
• the first electrode and the second electrode are electrically connected by the conductive particles. Because the connection structure according to the present invention has the above configuration, sufficient contact between the electrodes and the conductive particles can be achieved, improving conductivity reliability.
• the electrodes provided on the connection target members include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, SUS electrodes, and tungsten electrodes.
• the electrodes are preferably gold electrodes, nickel electrodes, tin electrodes, silver electrodes, or copper electrodes.
• the connection target members are glass substrates, the electrodes are preferably aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, or tungsten electrodes.
• the electrodes are aluminum electrodes, they may be formed solely from aluminum, or may be electrodes in which an aluminum layer is laminated on the surface of a metal oxide layer. Examples of materials for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal elements include Sn, Al, and Ga.
• nickel plating solution (1) (pH 8.5) containing 0.14 mol/L of nickel sulfate, 0.46 mol/L of dimethylamine borane, and 0.2 mol/L of sodium citrate was prepared.
• Formation of the second conductive layer Ten parts by weight of the resulting particles A were dispersed in 500 parts by weight of ion-exchanged water using an ultrasonicator to obtain suspension B.
• a tin-indium plating solution (1) (adjusted to pH 8.5 with sodium hydroxide) containing 15 g/L of tin sulfate, 34 g/L of indium sulfate, 70 g/L of ethylenediaminetetraacetic acid, 30 g/L of sodium gluconate, and 1.5 g/L of phosphinic acid was prepared.
• reducing solution A (adjusted to pH 10.0 with sodium hydroxide) containing 5 g/L of sodium borohydride was prepared.
• the tin-indium plating solution (1) was gradually added to the resulting suspension B while stirring at 55°C, and then electroless tin-indium plating was performed by reducing the solution with reducing solution A to form a second conductive layer.
• a second conductive layer (tin-indium alloy layer) was disposed on the surface of the first conductive layer, yielding conductive particles with protrusions on their surfaces.
• the resulting conductive material was applied to a PET (polyethylene terephthalate) film (separator, 50 ⁇ m thick) with one side treated for release, and then dried with hot air at 70°C for 5 minutes to produce an anisotropic conductive film.
• the resulting anisotropic conductive film had a thickness of 50 ⁇ m.
• connection structure A polyimide substrate (flexible printed circuit board) having an Au electrode pattern (electrode (Au circuit): Ni/Au thin film on Cu) with an L/S of 200 ⁇ m/200 ⁇ m on its upper surface was prepared.
• the resulting anisotropic conductive film was attached to the upper surface of the polyimide substrate at 80°C and 0.98 MPa (10 kgf/cm 2 ), and then the separator was peeled off.
• the Au bumps on the printed circuit board were then aligned with the Au circuits on the polyimide substrate.
• a pressure and heating head was then placed on the upper surface of the printed circuit board, and the anisotropic conductive film was cured at 140°C while applying a low pressure of 2 MPa calculated from the bonding area, thereby obtaining a connection structure.
• Example 2 Conductive particles, conductive materials, and connection structures were obtained in the same manner as in Example 1, except that the thickness of the second conductive layer was changed as shown in Table 1 below.
• Example 6 Conductive particles, conductive materials, and connection structures were obtained in the same manner as in Example 1, except that the type of base particle, the thickness of the first conductive layer, and the thickness of the second conductive layer were set as shown in Table 3 below.
• Example 9 Conductive particles, conductive materials, and connection structures were obtained in the same manner as in Example 1, except that the type of base particle, the thickness of the first conductive layer, and the thickness of the second conductive layer were set as shown in Table 3 below, and the thickness of the anisotropic conductive film was changed from 50 ⁇ m to 70 ⁇ m.
• Example 10 A tin-bismuth plating solution (1) (adjusted to pH 8.5 with sodium hydroxide) containing 15 g/L of tin sulfate, 41 g/L of bismuth sulfate, 70 g/L of ethylenediaminetetraacetic acid, 30 g/L of sodium gluconate, and 1.5 g/L of phosphinic acid was prepared.
• Conductive particles having protrusions on the surface thereof and a second conductive layer (tin-bismuth alloy layer) disposed on the surface of a first conductive layer (nickel layer) were obtained in the same manner as in Example 1, except that the tin-indium plating solution (1) was replaced with the tin-bismuth plating solution (1) and the thickness of the second conductive layer was changed.
• Conductive materials and connection structures were obtained in the same manner as in Example 1, except that the obtained conductive particles were used.
• Example 1 The particles A obtained in Example 1 were thoroughly washed with water and then dispersed in 500 parts by weight of distilled water to obtain a suspension C. 2 L of a gold plating solution (pH 9.0) containing 0.011 mol/L of potassium gold cyanide, 0.20 mol/L of sodium citrate, 0.08 mol/L of ethylenediaminetetraacetic acid, and 0.5 mol/L of sodium hydroxide was also prepared.
• a gold plating solution pH 9.0
• ⁇ The ratio of the length of the contact surface between the conductive particle and the electrode exceeds 70%.
• ⁇ The ratio of the length of the contact surface between the conductive particle and the electrode is more than 65% and not more than 70%.
• ⁇ The ratio of the length of the contact surface between the conductive particle and the electrode is more than 60% and not more than 65%.
• ⁇ The ratio of the length of the contact surface between the conductive particle and the electrode is more than 50% and not more than 60%.
• ⁇ The ratio of the length of the contact surface between the conductive particle and the electrode is 50% or less.
• Connection resistance A is 6.8 ⁇ or less ⁇ : Connection resistance A is greater than 6.8 ⁇ and less than 7.1 ⁇ ⁇ : Connection resistance A is greater than 7.1 ⁇ and less than 7.4 ⁇ ⁇ : Connection resistance A exceeds 7.4 ⁇
• connection reliability The connection structure after evaluation of "(4) Initial connection resistance” was left at 85°C and 85% humidity for 500 hours to conduct a conduction reliability test under a high temperature and high humidity environment. After the conduction reliability test, the connection resistance B between the upper and lower electrodes of the connection structure was measured by the four-terminal method. The conduction reliability was evaluated according to the following criteria.
• Connection resistance B is 7.5 ⁇ or less ⁇ : Connection resistance B is more than 7.5 ⁇ and less than 8.0 ⁇ ⁇ : Connection resistance B is more than 8.0 ⁇ and less than 8.7 ⁇ ⁇ : Connection resistance B exceeds 8.7 ⁇
• Example 9 The composition of the conductive particles and the results are shown in Tables 1 to 6 below. Note that the evaluation results for Example 9 are for a connection structure using an anisotropic conductive film with a thickness of 70 ⁇ m, but the evaluation results for a connection structure using an anisotropic conductive film with a thickness of 50 ⁇ m were similar.

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