JP4991666B2 - Conductive particles, anisotropic conductive materials, and connection structures - Google Patents

Description

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

  Anisotropic conductive materials such as anisotropic conductive pastes, anisotropic conductive inks, anisotropic conductive adhesives, anisotropic conductive films, and anisotropic conductive sheets are widely known. In these anisotropic conductive materials, conductive particles are dispersed in paste, ink, or resin.

  Anisotropic conductive materials are used for connection between an IC chip and a flexible printed circuit board, connection between an IC chip and a circuit board having an ITO electrode, and the like. For example, after an anisotropic conductive material is arranged between the electrode of the IC chip and the electrode of the circuit board, these electrodes can be connected by heating and pressurizing.

As an example of the conductive particles used for the anisotropic conductive material, the following Patent Document 1 discloses base material particles, a nickel layer formed on the surface of the base material particle, and formed on the surface of the nickel layer. Disclosed is a conductive particle comprising a modified palladium layer.
JP 2007-305583 A

  However, when the connection structure is formed using the conductive particles described in Patent Document 1 for connection between the electrodes, the connection resistance between the electrodes is reduced when the connection structure is exposed to high temperature and high humidity. Sometimes it was high.

  An object of the present invention is to form a connection structure by connecting electrodes, and even when the connection structure is exposed to high temperature and high humidity, the conductive particles that do not easily increase the connection resistance between the electrodes, and the An object of the present invention is to provide an anisotropic conductive material and a connection structure using conductive particles.

  According to the present invention, a substrate particle, a nickel layer formed on the surface of the substrate particle, and a palladium layer formed on the surface of the nickel layer, the phosphorus content of the nickel layer being 5 Conductive particles are provided that are in the range of ˜15 wt% and the palladium content of the palladium layer is 96 wt% or more.

  In one specific aspect of the present invention, the conductive particles have protrusions on the surface.

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

  In another specific aspect of the conductive particle according to the present invention, the insulating resin is an insulating resin particle.

  An anisotropic conductive material according to the present invention is characterized by including conductive particles configured according to the present invention and a binder resin.

  A connection structure according to the present invention includes a first connection target member, a second connection target member, and a connection portion that electrically connects the first and second connection target members, The connecting portion is formed of the conductive particles of the present invention or an anisotropic conductive material containing the conductive particles and a binder resin.

  In the conductive particles according to the present invention, the nickel layer and the palladium layer are formed in this order on the surface of the base particle, the phosphorus content of the nickel layer is in the range of 5 to 15% by weight, and Since the palladium content in the palladium layer is 96% by weight or more, the connection structure using conductive particles for connection between electrodes is prevented from increasing in connection resistance when exposed to high temperature and high humidity. it can. Therefore, the connection reliability of the connection structure can be improved.

  Hereinafter, the present invention will be described in detail.

  FIG. 1 is a cross-sectional view showing conductive particles according to an embodiment of the present invention.

  As shown in FIG. 1, the conductive particles 1 include a base particle 2, a nickel layer 3 formed on the surface 2 a of the base particle 2, and a palladium layer 4 formed on the surface 3 a of the nickel layer 3. With.

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

  Examples of the resin for forming the resin particles include divinylbenzene resin, styrene resin, acrylic resin, urea resin, imide resin, phenol resin, polyester resin, and vinyl chloride resin. Examples of the inorganic substance for forming the inorganic particles include silica or carbon black. Examples of the organic / inorganic hybrid particles include organic / inorganic hybrid particles formed of a crosslinked alkoxysilyl polymer and an acrylic resin. Examples of the metal for forming the metal particles include silver, copper, nickel, silicon, gold, and titanium.

  The average particle diameter of the substrate particles 2 is preferably in the range of 1 to 100 μm. When the average particle diameter of the substrate particles is smaller than 1 μm, the connection reliability between the electrodes may be lowered. When the average particle diameter of the substrate particles is larger than 100 μm, the distance between the electrodes may be too large.

  The phosphorus content of the nickel layer 3 formed on the surface 2a of the base particle 2 is in the range of 5 to 15% by weight. When the phosphorus content is less than 5% by weight, the connection resistance increases when the connection structure using the conductive particles for connection between the electrodes is exposed to high temperature and high humidity. When the phosphorus content exceeds 15% by weight, the initial connection resistance of the connection structure using the conductive particles for connection between the electrodes becomes high. Moreover, when the phosphorus content of the nickel layer 3 is 5 to 15% by weight, it becomes easy to obtain fine nickel crystals, and it becomes easy to obtain fine paraum crystals by epitaxial growth of palladium plating. For this reason, the connection reliability of the connection structure under high temperature and high humidity can be improved. The phosphorus content of the nickel layer 3 is preferably in the range of 10 to 15% by weight. When the phosphorus content of the nickel layer 3 is in the range of 10 to 15% by weight, the connection reliability of the connection structure under high temperature and high humidity can be further improved.

  As a method of bringing the phosphorus content of the nickel layer 3 within the above range, for example, when forming a nickel layer by electroless nickel plating, a method for controlling the pH of the nickel plating solution, or by electroless nickel plating For example, a method of controlling the concentration of the phosphorus-containing reducing agent when forming the oxidant is mentioned.

  The method for measuring the phosphorus content of the nickel layer is not particularly limited. For example, a thin film section of the obtained conductive particles is prepared using a focused ion beam, and a transmission electron microscope FE-TEM (Japan) A method of measuring the phosphorus content of the nickel layer with an energy dispersive X-ray analyzer (EDS) using “JEM-2010FEF” manufactured by Denshi Co., Ltd. is mentioned.

  The palladium content of the palladium layer 4 formed on the surface 3a of the nickel layer 3 is 96% by weight or more. When the palladium content is less than 96% by weight, the connection resistance increases when the connection structure using the conductive particles for connection between the electrodes is exposed to high temperature and high humidity. The palladium content is preferably 98% by weight or more.

  As a method of making the palladium content of the palladium layer 4 96% by weight or more, for example, when forming a palladium layer by electroless palladium plating, a method of controlling the pH of the palladium plating solution, or palladium by electroless palladium plating. A method of controlling the concentration of the reducing agent when forming the layer can be mentioned.

  The method for measuring the palladium content in the palladium layer is not particularly limited. For example, a thin film section of the obtained conductive particles is prepared using a focused ion beam, and a transmission electron microscope FE-TEM (Japan) A method of measuring the palladium content of the palladium layer with an energy dispersive X-ray analyzer (EDS) using “JEM-2010FEF” manufactured by Denshi Co., Ltd. may be mentioned.

  The total thickness of the metal layers of the nickel layer 3 and the palladium layer 4 is preferably in the range of 5 to 500 nm, and more preferably in the range of 10 to 400 nm. When the thickness of the metal layer is less than 5 nm, the conductivity of the conductive particles may be insufficient. If the thickness of the metal layer exceeds 500 nm, the difference in coefficient of thermal expansion between the substrate particles and the metal layer becomes large, and the metal layer may be easily peeled off from the substrate particles.

  Examples of the method for forming the nickel layer 3 on the surface 2a of the substrate particle 2 include a method of forming a nickel layer by electroless plating or a method of forming a nickel layer by electroplating.

  Examples of the method of forming the palladium layer 4 on the surface 3a of the nickel layer 3 include a method of forming a palladium layer by electroless plating or a method of forming a palladium layer by electroplating.

  The conductive particles preferably have protrusions on the surface. The conductive particles preferably have a plurality of protrusions on the surface. In this case, since the resin between the conductive particles and the electrodes can be effectively eliminated, the connection reliability of the connection structure using the conductive particles for the connection between the electrodes can be improved.

  As a method of forming protrusions on the surface of the conductive particles, a method of forming a metal layer by electroless plating after attaching a core substance to the surface of the base particles, or metal by electroless plating on the surface of the base particles Examples include a method of forming a metal layer by electroless plating after depositing a core material after forming the layer.

  As a method of attaching the core substance to the surface of the base particle, for example, a conductive substance that becomes the core substance is added to the dispersion liquid of the base particle, and the core substance is applied to the surface of the base particle, for example, van der A method of collecting and adhering by Waals force, or adding a conductive substance as a core substance to a container containing base particles, and the core substance on the surface of the base particles by mechanical action such as rotation of the container The method of making it adhere, etc. are mentioned. Among them, a method of accumulating and adhering the core substance on the surface of the base particle in the dispersion is preferable because the amount of the core substance to be attached is easy to control.

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

  Examples of the metal include gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, cadmium, and tin-lead alloys. , An alloy composed of two or more metals such as a tin-copper alloy, a tin-silver alloy, or a tin-lead-silver alloy. Of these, nickel, copper, silver or gold is preferable. The metal constituting the core material may be the same as or different from the metal constituting the metal layer.

  The shape of the core material is not particularly limited. The shape of the core substance is preferably a lump. Examples of the core substance include a particulate lump, an agglomerate in which a plurality of fine particles are aggregated, and an irregular lump.

  The conductive particles according to the present invention preferably further include an insulating resin attached to the surface of the palladium layer. In this case, when the conductive particles are used for connection between the electrodes, a short circuit between adjacent electrodes can be prevented.

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

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

  Examples of a method for attaching the insulating resin to the surface of the palladium layer include a chemical method, a physical or mechanical method, and the like. Examples of the chemical method include an interfacial polymerization method, a suspension polymerization method in the presence of particles, or an emulsion polymerization method. Examples of the physical or mechanical method include spray drying, hybridization, electrostatic adhesion, spraying, dipping, or vacuum deposition.

  The insulating resin is preferably insulating resin particles. In this case, when the conductive particles are used for connection between the electrodes, not only can a short circuit between adjacent electrodes be prevented, but also the connection resistance between the opposing electrodes can be reduced.

  Examples of a method for attaching insulating resin particles to the surface of the palladium layer include a chemical method, a physical or mechanical method, and the like. Examples of the chemical method include a method of attaching insulating resin particles to the surface of a palladium layer through a chemical bond. Examples of the physical or mechanical method include a method using hybridization or an electrostatic adhesion method. In particular, since the insulating resin particles are difficult to peel off, a method of attaching the insulating resin particles to the surface of the palladium layer through a chemical bond is preferable.

(Anisotropic conductive material)
The anisotropic conductive material according to the present invention contains the conductive particles of the present invention and a binder resin.

  The binder resin is not particularly limited. As the binder resin, generally an insulating resin is used. Examples of the binder resin include a vinyl resin, a thermoplastic resin, a curable resin, a thermoplastic block copolymer, or an elastomer. Binder resin may be used independently and 2 or more types may be used together.

  Examples of the vinyl resin include vinyl acetate resin, acrylic resin, and styrene resin. Examples of the thermoplastic resin include polyolefin resin, ethylene-vinyl acetate copolymer, polyamide resin, and the like. Examples of the curable resin include an epoxy resin, a urethane resin, a polyimide resin, and an unsaturated polyester resin. The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin, or a moisture curable resin. The curable resin may be used in combination with a curing agent. Examples of the thermoplastic block copolymer include a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a hydrogenated product of a styrene-butadiene-styrene block copolymer, or a styrene-isoprene- Examples thereof include a hydrogenated product of a styrene block copolymer. Examples of the elastomer include styrene-butadiene copolymer rubber or acrylonitrile-styrene block copolymer rubber.

  Anisotropic conductive materials include, for example, fillers, extenders, softeners, plasticizers, polymerization catalysts, curing catalysts, colorants, antioxidants, thermal stabilizers, light stabilizers, in addition to conductive particles and binder resins. Various additives such as an agent, an ultraviolet absorber, a lubricant, an antistatic agent or a flame retardant may be contained.

  The method for dispersing the conductive particles in the binder resin is not particularly limited, and a conventionally known dispersion method can be used. As a method for dispersing the conductive particles in the binder resin, for example, after adding the conductive particles in the binder resin, kneading and dispersing with a planetary mixer or the like, the conductive particles in water or an organic solvent. After uniformly dispersing using a homogenizer, etc., add into the binder resin, knead and disperse with a planetary mixer, etc., or after diluting the binder resin with water or organic solvent, add conductive particles And a method of kneading and dispersing with a planetary mixer or the like.

  The anisotropic conductive material of 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.

(Connection structure)
FIG. 2 is a front sectional view showing a connection structure in which conductive particles according to an embodiment of the present invention are used.

  As shown in FIG. 2, the connection structure 11 includes a circuit board 12 as a first connection target member, a semiconductor chip 14 as a second connection target member, and electrodes of the circuit board 12 and the semiconductor chip 14. 12a and 14a. The connection part 13 which has electrically connected between 14a and 14a is provided. The connection part 13 is formed of an anisotropic conductive film.

  A plurality of electrodes 12 a are provided on the upper surface of the circuit board 12. A plurality of electrodes 14 a are provided on the lower surface of the semiconductor chip 14. A semiconductor chip 14 is laminated on the upper surface of the circuit board 12 via an anisotropic conductive film containing the conductive particles 1. A connecting portion 13 formed of an anisotropic conductive film including the conductive particles 1 is disposed between the electrode 12a and the electrode 14a. In FIG. 2, the conductive particles 1 are shown schematically.

  As the connection structure, specifically, an electronic component chip such as a semiconductor chip, a capacitor chip or a diode chip is mounted on a circuit board, and the electrode of the electronic component chip is electrically connected to the electrode on the circuit board. Connection structure etc. which are connected in general. Examples of circuit boards include various printed boards such as flexible printed boards, glass boards, and various circuit boards such as boards on which metal foils are laminated.

  The manufacturing method of the connection structure is not particularly limited. As an example of a manufacturing method of a connection structure, the anisotropic conductive material is disposed between a first connection target member such as an electronic component or a circuit board and a second connection target member such as an electronic component or a circuit board. And after obtaining a laminated body, the method of heating and pressurizing this laminated body is mentioned.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited only to the following examples.

Example 1
(1) Electroless nickel plating step Divinylbenzene resin particles having an average particle diameter of 4 μm were treated with a 10 wt% solution of an ion adsorbent for 5 minutes, and then treated with a 0.01 wt% palladium sulfate aqueous solution for 5 minutes. Thereafter, dimethylamine borane was added for reduction treatment, filtration, and washing to obtain resin particles to which palladium was attached.

  Next, a 1% by weight sodium succinate solution in which sodium succinate was dissolved in 500 mL of ion exchange water was prepared. To this solution, 10 g of resin particles with palladium attached were added and mixed to prepare a slurry. The pH of the slurry was adjusted to 6.5. As a nickel plating solution, an initial nickel solution containing 10% by weight of nickel sulfate, 10% by weight of sodium hypophosphite, 4% by weight of sodium hydroxide and 20% by weight of sodium succinate was prepared. The slurry adjusted to pH 6.5 was heated to 80 ° C., and then the nickel solution was continuously added dropwise to the slurry and stirred for 20 minutes to advance the plating reaction. After confirming that hydrogen was no longer generated, the plating reaction was completed.

  Next, a late nickel solution containing 20 wt% nickel sulfate, 20 wt% sodium hypophosphite and 5 wt% sodium hydroxide was prepared. The late nickel solution was continuously added dropwise to the solution that had finished the plating reaction with the previous nickel solution, and the plating reaction was allowed to proceed by stirring for 1 hour. In this way, a nickel layer was formed on the surface of the resin particles to obtain nickel plated particles. The nickel layer had a thickness of 0.1 μm.

(2) Electroless palladium plating step 10 g of the obtained nickel-plated particles were dispersed in 500 mL of ion-exchanged water using an ultrasonic treatment machine to obtain a particle suspension. While stirring the suspension at 50 ° C., 0.02 mol / L of palladium sulfate, 0.04 mol / L of ethylenediamine as a complexing agent, 0.06 mol / L of sodium formate as a reducing agent, and pH 10.0 containing a crystal modifier. The electroless plating solution was gradually added to perform electroless palladium plating. When the thickness of the palladium layer reached 0.03 μm, the electroless palladium plating was finished. Next, by washing and vacuum drying, conductive particles having a palladium layer formed on the surface of the nickel layer were obtained.

(Example 2)
(1) Electroless nickel plating step Divinylbenzene resin particles having an average particle diameter of 4 μm were treated with a 10 wt% solution of an ion adsorbent for 5 minutes, and then treated with a 0.01 wt% palladium sulfate aqueous solution for 5 minutes. Thereafter, dimethylamine borane was added for reduction treatment, filtration, and washing to obtain resin particles to which palladium was attached.

  Next, a 1% by weight sodium succinate solution in which sodium succinate was dissolved in 500 mL of ion exchange water was prepared. To this solution, 10 g of resin particles with palladium attached were added and mixed to prepare a slurry. The pH of the slurry was adjusted to 9.0. As a nickel plating solution, an initial nickel solution containing 10% by weight of nickel sulfate, 10% by weight of sodium hypophosphite, 4% by weight of sodium hydroxide and 20% by weight of sodium succinate was prepared. The slurry adjusted to pH 9.0 was heated to 80 ° C., and then the nickel solution was continuously added dropwise to the slurry and stirred for 20 minutes to advance the plating reaction. After confirming that hydrogen was no longer generated, the plating reaction was completed.

  Next, a late nickel solution containing 20% by weight nickel sulfate, 20% by weight sodium hypophosphite and 15% by weight sodium hydroxide was prepared. The late nickel solution was continuously added dropwise to the solution that had finished the plating reaction with the previous nickel solution, and the plating reaction was allowed to proceed by stirring for 1 hour. In this way, a nickel layer was formed on the surface of the resin particles to obtain nickel plated particles. The nickel layer had a thickness of 0.1 μm.

(2) Electroless Palladium Plating Step By conducting palladium plating in the same manner as in Example 1, conductive particles having a palladium layer formed on the surface of the nickel layer were obtained.

(Example 3)
(1) Electroless nickel plating step Divinylbenzene resin particles having an average particle diameter of 4 μm were treated with a 10 wt% solution of an ion adsorbent for 5 minutes, and then treated with a 0.01 wt% palladium sulfate aqueous solution for 5 minutes. Thereafter, dimethylamine borane was added for reduction treatment, filtration, and washing to obtain resin particles to which palladium was attached.

  Next, a 1% by weight sodium succinate solution in which sodium succinate was dissolved in 500 mL of ion exchange water was prepared. To this solution, 10 g of resin particles with palladium attached were added and mixed to prepare a slurry. The pH of the slurry was adjusted to 4.5. As a nickel plating solution, an initial nickel solution containing 10% by weight of nickel sulfate, 10% by weight of sodium hypophosphite, 4% by weight of sodium hydroxide and 20% by weight of sodium succinate was prepared. The slurry adjusted to pH 4.5 was heated to 80 ° C., and then the nickel solution was continuously added dropwise to the slurry and stirred for 20 minutes to advance the plating reaction. After confirming that hydrogen was no longer generated, the plating reaction was completed.

  Next, a late nickel solution containing 20% by weight nickel sulfate, 30% by weight sodium hypophosphite and 5% by weight sodium hydroxide was prepared. The late nickel solution was continuously added dropwise to the solution that had finished the plating reaction with the previous nickel solution, and the plating reaction was allowed to proceed by stirring for 1 hour. In this way, a nickel layer was formed on the surface of the resin particles to obtain nickel plated particles. The nickel layer had a thickness of 0.1 μm.

(2) Electroless Palladium Plating Step By conducting palladium plating in the same manner as in Example 1, conductive particles having a palladium layer formed on the surface of the nickel layer were obtained.

Example 4
(1) Electroless nickel plating step (step of forming protrusions on the surface of the nickel layer)
1-1) Palladium adhesion process 10 g of divinylbenzene resin particles having an average particle diameter of 4 μm were prepared. The resin particles were etched and washed with water. Next, resin particles were added to 100 mL of a palladium-catalyzed solution containing 8% by weight of a palladium catalyst and stirred. Then, it filtered and wash | cleaned. Resin particles were added to 0.5 wt% dimethylamine borane solution at pH 6 to obtain resin particles to which palladium was attached.

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

1-3) Electroless nickel plating step 500 mL of ion-exchanged water was added to the resin particles to which the core substance was adhered, and the resin particles were sufficiently dispersed to obtain a suspension. While stirring this suspension, an electroless nickel plating solution having a pH of 5.0 containing nickel sulfate hexahydrate 50 g / L, sodium hypophosphite monohydrate 40 g / L and citric acid 50 g / L was gradually added. And electroless nickel plating. In this way, a nickel layer was formed on the surface of the resin particles, and nickel plated particles having protrusions on the surface were obtained. The nickel layer had a thickness of 0.1 μm.

(2) Electroless palladium plating step Conductive particles having a palladium layer formed on the surface of the nickel layer are obtained by performing the same electroless palladium plating step as in Example 1 using 10 g of the obtained nickel plating particles. Obtained. The obtained conductive particles had protrusions on the surface.

(Example 5)
Divinylbenzene resin particles are copolymerized resin particles of 1,4-butanediol diacrylate and tetramethylolmethane tetraacrylate (1,4-butanediol diacrylate: tetramethylolmethane tetraacrylate = 95 wt%: 5 wt% The conductive particles were obtained in the same manner as in Example 4 except that the change was changed to The obtained conductive particles had protrusions on the surface.

(Example 6)
(1) Production of insulating resin particles In a 1000 mL separable flask equipped with a four-neck separable cover, a stirring blade, a three-way cock, a cooling tube and a temperature probe, 100 mmol of methyl methacrylate and N, N, N-trimethyl Ion-exchanged water containing a monomer composition containing 1 mmol of -N-2-methacryloyloxyethylammonium chloride and 1 mmol of 2,2'-azobis (2-amidinopropane) dihydrochloride so that the solid content is 5% by weight. Then, the mixture was stirred at 200 rpm and polymerized at 70 ° C. for 24 hours under a nitrogen atmosphere. After completion of the reaction, freeze drying was performed to obtain insulating resin particles having an ammonium group on the surface, an average particle diameter of 220 nm, and a CV value of 10%.

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

  10 g of the conductive particles obtained in Example 5 were dispersed in 500 mL of ion exchange water, 4 g of an aqueous dispersion of insulating resin particles was added, and the mixture was stirred at room temperature for 6 hours. After filtration through a 3 μm mesh filter, the particles were further washed with methanol and dried to obtain conductive particles having insulating resin particles attached thereto.

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

(Example 7)
Divinylbenzene resin particles are copolymerized resin particles of 1,4-butanediol diacrylate and tetramethylolmethane tetraacrylate (1,4-butanediol diacrylate: tetramethylolmethane tetraacrylate = 95 wt%: 5 wt% The conductive particles were obtained in the same manner as in Example 1 except that the above was changed.

(Example 8)
Except having changed the electroconductive particle obtained in Example 5 into the electroconductive particle obtained in Example 1, it carried out similarly to Example 6, and obtained the electroconductive particle to which the insulating resin particle adhered.

Example 9
Except having changed the electroconductive particle obtained in Example 5 into the electroconductive particle obtained in Example 4, it carried out similarly to Example 6, and obtained the electroconductive particle to which the insulating resin particle adhered.

(Example 10)
Except having changed the electroconductive particle obtained in Example 5 into the electroconductive particle obtained in Example 7, it carried out similarly to Example 6, and obtained the electroconductive particle to which the insulating resin particle adhered.

(Comparative Example 1)
In the electroless palladium plating step, electroless plating solution having a pH of 10.0 containing 0.02 mol / L of palladium sulfate, 0.04 mol / L of ethylenediamine as a complexing agent, 0.06 mol / L of sodium formate as a reducing agent, and a crystal modifier. Was changed to an electroless plating solution of pH 6.5 containing 0.02 mol / L of palladium sulfate, 0.04 mol / L of ethylenediamine as a complexing agent, 0.09 mol / L of sodium hypophosphite as a reducing agent and a crystal modifier. Except that, conductive particles having a nickel layer formed on the surface of the resin particles and a palladium layer formed on the surface of the nickel layer were obtained in the same manner as in Example 1.

(Comparative Example 2)
In the electroless nickel plating step, the pH was adjusted to 7.5 when adjusting the pH, and nickel sulfate 10 wt%, sodium hypophosphite 10 wt%, sodium hydroxide 4 wt%, and sodium succinate 20 Example 1 except that the nickel solution containing 10% by weight was changed to a nickel solution containing 10% by weight nickel sulfate, 6% by weight sodium hypophosphite, 4% by weight sodium hydroxide and 20% by weight sodium succinate. In the same manner as in Example 1, conductive particles having a nickel layer formed on the surface of the resin particles and a palladium layer formed on the surface of the nickel layer were obtained.

(Comparative Example 3)
In the electroless nickel plating step, the pH of the slurry was adjusted to 4.5, and 10% by weight of nickel sulfate, 10% by weight of sodium hypophosphite, 4% by weight of sodium hydroxide and 20% by weight of sodium succinate were included. Example 1 was the same as Example 1 except that the nickel solution was changed to a nickel solution containing 10% by weight nickel sulfate, 30% by weight sodium hypophosphite, 4% by weight sodium hydroxide and 20% by weight sodium succinate. Thus, conductive particles having a nickel layer formed on the surface of the resin particles and a palladium layer formed on the surface of the nickel layer were obtained.

(Evaluation)
(1) Phosphorus content of nickel layer Thin film slices of the obtained conductive particles were prepared using a focused ion beam. Using a transmission electron microscope FE-TEM (“JEM-2010FEF” manufactured by JEOL Ltd.), the phosphorus content of the nickel layer was measured with an energy dispersive X-ray analyzer (EDS). Similarly, the phosphorus content of the nickel layer of 10 arbitrary conductive particles was measured, and the average value was calculated.

(2) Palladium Content of Palladium Layer Using a focused ion beam, a thin film slice of the obtained conductive particles was prepared. Using a transmission electron microscope FE-TEM (“JEM-2010FEF” manufactured by JEOL Ltd.), the content of palladium in the palladium layer was measured with an energy dispersive X-ray analyzer (EDS). Similarly, the palladium content of the palladium layer of 10 arbitrary conductive particles was measured, and the average value was calculated.

(3) Connection resistance Two substrates on which copper electrodes with L / S of 100 μm / 100 μm were formed were prepared. In addition, 10 parts by weight of the conductive particles obtained in Examples and Comparative Examples, 85 parts by weight of an epoxy resin (“Stractbond XN-5A” manufactured by Mitsui Chemicals) as a binder resin, and 5 parts by weight of an imidazole type curing agent An anisotropic conductive paste containing was prepared.

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

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

  Next, the obtained connection structure was allowed to stand for 100 hours at 85 ° C. and a humidity of 85%. The connection resistance between the electrodes of the connection structure after being allowed to stand was measured by the four-terminal method, and the obtained measured value was used as the connection resistance after the high temperature and high humidity test.

(4) Insulation resistance As shown in FIG. 3, comb-shaped electrode copper patterns 21 and 22 having L / S of 20 μm / 20 μm, in which a nickel plating layer and a gold plating layer are sequentially formed, are formed on the surface of the copper electrode. A prepared substrate was prepared. In addition, 10 parts by weight of the conductive particles obtained in Examples and Comparative Examples, 85 parts by weight of an epoxy resin (“Stractbond XN-5A” manufactured by Mitsui Chemicals) as a binder resin, and 5 parts by weight of an imidazole type curing agent An anisotropic conductive paste containing was prepared.

  After the anisotropic conductive paste was applied to the upper surfaces of the copper patterns 21 and 22 of the substrate, an alkali-free glass plate was laminated and pressure-bonded to bring the conductive particles into contact with the copper patterns 21 and 22. In the state which laminated | stacked the alkali free glass plate, the anisotropic conductive paste was hardened by heating at 180 degreeC for 1 minute, and the connection structure was obtained.

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

  Next, the obtained connection structure was left to stand for 1000 hours under the conditions of 85 ° C. and 85% humidity while applying a bias voltage of 50 V between the electrodes. The insulation resistance between the adjacent electrodes of the connection structure after being allowed to stand was measured by the four-terminal method, and the obtained measurement value was taken as the insulation resistance after the high temperature and high humidity test.

  The results are shown in Table 1 below.

FIG. 1 is a cross-sectional view showing conductive particles according to an embodiment of the present invention. FIG. 2 is a front sectional view schematically showing a connection structure in which conductive particles according to an embodiment of the present invention are used. FIG. 3 is a plan view for explaining the shape of the interdigital electrode copper pattern on the substrate used in the evaluation of the insulation resistance of the example and the comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Conductive particle 2 ... Base particle 2a ... Surface 3 ... Nickel layer 3a ... Surface 4 ... Palladium layer 11 ... Connection structure 12 ... Circuit board 12a ... Electrode 13 ... Connection part 14 ... Semiconductor chip 14a ... Electrode 21,22 ... Combine electrode copper pattern

Claims (6)

A substrate particle, a nickel layer formed on the surface of the substrate particle, and a palladium layer formed on the surface of the nickel layer,
Conductive particles, wherein the nickel layer has a phosphorus content of 5 to 15% by weight and the palladium layer has a palladium content of 96% by weight or more.   The electroconductive particle of Claim 1 which has a processus | protrusion on the surface.   The conductive particle according to claim 1, further comprising an insulating resin attached to a surface of the palladium layer.   The electroconductive particle of Claim 3 whose said insulating resin is an insulating resin particle.   An anisotropic conductive material comprising the conductive particles according to claim 1 and a binder resin. 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 connection structure, wherein the connection portion is formed of the conductive particles according to any one of claims 1 to 4 or an anisotropic conductive material containing the conductive particles and a binder resin. .

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