JP6512734B2 - Coated conductive powder, method of producing coated conductive powder, conductive adhesive containing coated conductive powder, and adhesive structure - Google Patents

Description

  The present invention relates to a coated conductive powder, a method of producing a coated conductive powder, a conductive adhesive containing a coated conductive powder, and an adhesive structure.

  In electrically connecting circuit boards or an electronic component such as an IC chip and the circuit board, an anisotropic conductive adhesive in which conductive particles are dispersed is used. These adhesives are disposed between opposing electrodes, and after the electrodes are connected by heating and pressing, electrical connection and fixation are performed by providing conductivity in the pressing direction.

  As such conductive particles, it has been proposed to use a coated conductive powder in which the surface of the conductive particles is covered with an insulator such as titanium oxide. For example, as a method of coating the surface of conductive particles with titanium oxide, a method of firmly fixing fine titanium oxide particles in a buried state to the surface of conductive particles by a mechanofusion system or a hybridization system is known. (See Patent Documents 1 and 2).

  The present inventors also proposed a coated conductive powder in which fine titanium oxide particles are attached to the surface of conductive particles using a dry bead mill or the like (see Patent Documents 3 and 4).

Japanese Patent Application Publication No. 07-118617 JP 2000-215730 A WO 2009/054386 pamphlet WO 2009/054387 pamphlet

  However, as in Patent Documents 1 and 2, in the method of surface modification / composition of conductive particles in a dry manner by the strong impact force of a mechanofusion system or a hybridization system, fine titanium oxide particles are conducted The mechanical impact on the surface of the sexual particles causes the fracture and deformation of the conductive particles. In particular, when metal-coated resin particles obtained by plating the surface of resin particles as a core material are used as conductive particles, there are problems such as peeling and deformation of the metal coating film and deformation, cracking and breakage of the core material. . Furthermore, the coated conductive powder thus obtained has a strong coating film of titanium oxide, and therefore, when used as an adhesive, the flexibility of the resin particles as the core material is lost at the time of connection, and the electric conduction is achieved. Or there is a concern that it will bite into the counter electrode and destroy it.

  Moreover, in the coated conductive powder obtained by the methods of Patent Documents 3 and 4, the titanium oxide particles attached to the surface of the conductive particles do not come off due to external factors such as a slight impact, etc. When used as an agent, it can be peeled off from the conductive particles and uniformly diffused in the adhesive. However, when the coated conductive powder obtained by this method is stored at 60 ° C. and 95% RH for 1000 hours, aggregated particles of about 8 μm to 10 μm are formed. In recent years, due to the miniaturization of electrodes of electronic parts and the narrowing of wiring, there is a demand for a coated conductive powder having better dispersibility, and coated conductive powders obtained by the methods of Patent Documents 3 and 4 are required. There is a problem that it can not meet such a demand.

  Therefore, an object of the present invention is to provide a coating in which the surface of the conductive particles is coated with titanium oxide without causing breakage and deformation of the conductive particles, and the coating film of the titanium oxide is soft and has excellent dispersibility. An electrically conductive powder, a method for producing the same, and an adhesive structure using the coated conductive powder.

  As a result of intensive studies to solve the above problems, the present inventors have made fine titanium oxide on the surface of conductive particles having a metal film formed on the surface of core particles using a peroxotitanic acid solution. It was found that it was effective to deposit and coat the surface of the conductive particles with titanium oxide, and the present invention has been completed.

That is, the present invention is characterized in that the surface of the conductive particle in which the metal film is formed on the surface of the core particle is coated with titanium oxide deposited from an alkaline solution containing peroxotitanic acid. It is powder.
In the present invention, an alkaline solution containing peroxotitanic acid is added to a suspension containing conductive particles in which a metal film is formed on the surface of core particles, and titanium oxide is deposited on the surface of the conductive particles. It is a manufacturing method of the covering conductive powder characterized by having a process of making it.

  According to the present invention, the surface of the conductive particles is coated with fine titanium oxide without causing breakage and deformation of the conductive particles, the coating film of the titanium oxide is soft, and the dispersibility is good. It is possible to provide a coated conductive powder and a method for producing the same.

5 is an electron micrograph of the coated conductive powder obtained in Example 1.

Hereinafter, the present invention will be described in detail.
In the coated conductive powder of the present invention, the surface of the conductive particle having the metal film formed on the surface of the core particle is coated with fine titanium oxide deposited from an alkaline solution containing peroxotitanic acid, There is no impact force applied to the conductive particles, such as a mechanofusion system or a hybridization system, and destruction and deformation of the conductive particles do not occur. Further, since the coated conductive powder of the present invention is not coated with a continuous film of titanium oxide, but is coated with fine titanium oxide deposited, as shown in, for example, an electron micrograph shown in FIG. The thickness of the titanium oxide coating is not uniform across the surface and varies from place to place. Furthermore, since the coating film of titanium oxide is not strong but moderately soft, flexibility as a whole of the coated conductive powder is secured.

  As described above, the coating film of titanium oxide in the coated conductive powder of the present invention is formed as an aggregate of fine titanium oxide deposited on the surface of the metal film of the conductive particles. The coating film of titanium oxide has thick and thin areas, but when it is used for conductive adhesive, external force can easily break the thin area at connection. Therefore, high connection reliability can be obtained.

  Although the thickness of the titanium oxide coating film is not uniform and varies depending on the location, the thickness of the titanium oxide coating film is preferably 1 nm to 1000 nm, more preferably 2 nm to 200 nm in a thick location. If the thickness of the titanium oxide coating film is within the above range, it is easy to ensure conductivity. The color tone of the coated conductive powder can also be controlled by changing the thickness of the titanium oxide coating film. When the thickness of the titanium oxide coating film is reduced, the resulting coated conductive powder exhibits the color of the conductive particles because titanium oxide is almost transparent. On the other hand, when the thickness of the titanium oxide coating film is increased, the obtained coated conductive powder exhibits gray to white. Therefore, when the coated conductive powder of the present invention is used for optical applications, the thickness of the titanium oxide coated film may be further increased in consideration of light reflection and refraction.

The thickness of the titanium oxide coating film is as described above, but the amount of the titanium oxide coating film is preferably 0.1% by mass to 200% by mass, with respect to the obtained coated conductive powder. More preferably, it is 0.5 mass-150 mass%. If the amount of the titanium oxide coating film is within the above range, the dispersibility can be further improved, and the coating film is more easily broken by external force at the time of connection, so high connection reliability Is obtained.
The thickness and amount of the titanium oxide film can be optionally changed by adjusting the amount of peroxotitanic acid added to the conductive particles.

  The solution containing peroxotitanic acid used in the present invention is hydrolyzed by adding an alkali hydroxide to a titanium solution to wash the obtained white precipitate (titanium hydroxide) and then dissolved by adding hydrogen peroxide Can be prepared by

  In the present invention, the titanium solution used to prepare the solution containing peroxotitanic acid is not particularly limited, and examples thereof include titanium alkoxide, titanium chloride solution, titanium sulfate solution, titanium hydroxide solution and the like. These may be used alone or in combination of two or more. The valence of titanium may be trivalent as well as tetravalent. Among these, titanium tetrachloride solution is preferable in terms of cost and ease of handling. The alkali hydroxide to be added to the titanium solution is not particularly limited, and examples thereof include aqueous ammonia, an aqueous solution of an alkali metal hydroxide such as sodium hydroxide, and the like. As hydrogen peroxide used to dissolve the white precipitate (titanium hydroxide), a commercial product having a concentration of several% to 60% can be used without limitation. In the present invention, hydrogen peroxide having a concentration of 30% to 35% is preferred.

  The amount of hydrogen peroxide to be added is preferably 0.3 times by mole to 60 times by mole, and more preferably 1 times by mole to 54 times by mole with respect to titanium hydroxide. If the addition amount of hydrogen peroxide is within the above range, a solution containing peroxotitanic acid can be obtained at a practical addition amount.

  An alkaline solution may be added along with hydrogen peroxide to facilitate dissolution of the white precipitate. As an alkaline solution, sodium hydrogencarbonate, potassium hydrogencarbonate, lithium hydrogencarbonate, ammonium hydrogencarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia water etc. are mentioned, for example. These may be used alone or in combination of two or more. Among these, sodium hydroxide and aqueous ammonia are preferable in terms of ease of handling.

The pH of the alkaline solution containing peroxotitanic acid is preferably 8 to 14, and more preferably 8 to 13. If the pH of the alkaline solution containing peroxotitanic acid is within the above range, peroxotitanic acid will be present in a more stable state in the solution. If the pH is less than 8, the crystallinity of the precipitated TiO ₂ may be degraded or precipitation may occur at room temperature. When the pH is more than 14, it is not practical, and there is a risk that an alkaline component may remain in the obtained coated conductive powder. The adjustment of pH may be performed by adding the above-mentioned alkaline solution.

  The titanium oxide may be deposited on the surface of the conductive particles by dropping an alkaline solution containing peroxotitanic acid into a suspension in which the conductive particles are dispersed. When an alkaline solution containing peroxotitanic acid is dropped, titanium oxide is gradually deposited on the surface of the conductive particles. Peroxotitanic acid is included such that the concentration of peroxotitanic acid in the suspension is preferably 0.001 g / L to 0.1 g / L, more preferably 0.005 g / L to 0.08 g / L It is desirable to adjust the dropping rate of the alkaline solution. If the concentration of peroxotitanic acid is within the above range, titanium oxide can be efficiently deposited on the surface of the conductive particles in a short time. In addition, the concentration of the conductive particles in the suspension is preferably 0.1 g / L to 200 g / L, and more preferably 1 g / L to 150 g / L. If the concentration of the conductive particles in the suspension is within the above range, titanium oxide can be deposited on the surface of the conductive particles more uniformly and efficiently in a short time, and aggregation of the coated conductive powder is also possible. Can be suppressed.

  In addition, when dropping an alkaline solution containing peroxotitanic acid, it is desirable to heat the suspension to preferably 35 ° C to 95 ° C, more preferably 45 ° C to 95 ° C while stirring the suspension. If the temperature at the time of deposition is within the above range, titanium oxide can be efficiently deposited in a short time without adversely affecting the properties of the coating film.

  After completion of the addition of the alkaline solution containing peroxotitanic acid, if necessary, the suspension is preferably heated to 50 ° C. to 95 ° C., more preferably 60 ° C. to 95 ° C. while stirring, preferably 10 minutes It is desirable to be aged by holding for 5 hours, more preferably for 30 minutes to 3 hours. If the aging temperature and time are within the above range, deposition of titanium oxide on the surface of conductive particles can be promoted.

Also, in order to age more effectively, the suspension can be processed under high temperature and pressure after the addition of the alkaline solution containing peroxotitanic acid. Generally, an autoclave or the like is effective, but it is not particularly limited as long as it can maintain high temperature and high pressure during aging. At this time, when the core particles are made of a resin material, the pressure is preferably 1.2 kg / cm ^{2 to} 5 kg / cm ² , and the temperature is preferably 100 ° C. to 300 ° C. If the pressure and temperature are in the above-mentioned range, precipitation of titanium oxide on the surface of the conductive particles can be further promoted without destroying the core particles made of the resin material. On the other hand, when the core particles are made of metal or ceramic, the pressure and temperature are not limited to this, and may be raised to the melting temperature of the core particles. In this case, a pressure of 300 kg / cm ² or less and a temperature of 300 ° C. or less are practical.
After aging, the suspension is filtered, and the filtrate is, if necessary, washed by repulping to remove the alkali component, and then dried to obtain a coated conductive powder.

  In addition, an inorganic acid, an organic acid, an inorganic alkali, an organic alkali, a polymer, an alcohol, etc. may be added to the alkaline solution containing peroxotitanic acid, as long as the precipitation of titanium oxide is not inhibited. Hydroxycarboxylic acid, its salt, aqueous ammonia solution, ammonium salt and the like may be added.

  As the core particles used in the present invention, whether it is an inorganic substance or an organic substance can be used without particular limitation. As core particles of inorganic substances, metal particles such as gold, silver, copper, nickel, palladium and solder, alloys, glass, ceramic, silica, oxides of metals or nonmetals (including water hydrates), aluminosilicates And metal silicates, metal carbides, metal nitrides, metal carbonates, metal sulfates, metal phosphates, metal sulfides, metal salts, metal halides, carbon halides and the like. On the other hand, as core particles of an organic substance, for example, heat of natural fiber, natural resin, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylic ester, polyacrylic nitrile, polyacetal, ionomer, polyester, etc. Plastic resin, alkyd resin, phenol resin, urea resin, benzoguanamine resin, melamine resin, xylene resin, silicone resin, epoxy resin, diallyl phthalate resin, etc. may be mentioned. These may be used alone or in combination of two or more. Among these, core particles made of a resin material are preferable in that they have a smaller specific gravity and are less likely to settle than core particles made of metal, are excellent in dispersion stability, and can easily maintain electrical connection due to the elasticity of resin. .

  The shape of the core particles is not particularly limited. In general, the core particles are spherical. However, the core material particles may have a shape other than a spherical shape, for example, a fiber shape, a hollow shape, a plate shape, or a needle shape, and may have a large number of projections on the surface or an irregular shape. In the present invention, spherical core particles are preferred in terms of excellent filling properties.

  The average particle diameter of the core particles is preferably 1 μm to 100 μm, more preferably 1.5 μm to 30 μm. If the average particle diameter of the core particles is within the above range, the conductive conductive powder obtained can ensure conduction between the opposing electrodes without causing a short circuit between adjacent electrodes. In the present invention, the average particle diameter of the core particles is a value measured using an electrical resistance method.

Furthermore, the particle size distribution of the core particles measured by the above-mentioned method is wide. In general, the width of the particle size distribution of the powder is represented by the coefficient of variation shown by the following formula (1).
Coefficient of variation (%) = (standard deviation / average particle size) × 100 (1)
The fact that the coefficient of variation is large indicates that the distribution is broad, while the fact that the coefficient of variation is small indicates that the particle size distribution is sharp. In the present invention, it is desirable to use core particles having a coefficient of variation of preferably 50% or less, more preferably 30% or less, and most preferably 20% or less. The reason for this is that when conductive particles having titanium oxide fixed thereto according to the present invention are used as conductive particles in the anisotropic conductive film, there is an advantage that the contribution ratio for connection becomes high.

The other physical properties of the core particle are not particularly limited, but in the case of the core particle made of a resin material, the following formula (2):
K (kgf / mm ² ) = (3 / √2) × F × S−3 / 2 × R−1 / 2 (2)
[In Formula (2), F and S respectively indicate load value (kgf) and compression displacement (mm in 10% compression deformation of core particles when measured by a micro compression tester (manufactured by MCTM-500 Shimadzu Corporation) Where R is the radius (mm) of the core particle measured with a micro compression tester (MCTM-500 manufactured by Shimadzu Corporation), and the value of K is 10 kgf / mm ^{2 at} 20 ° C. If the recovery rate after 10% compression deformation is in the range of 1% to 100% at 20 ° C., the electrode will not be damaged when the electrodes are crimped, and the recovery rate after 10% compression deformation is in the range of 10000 kgf / mm ² It is preferable in that it can be brought into sufficient contact.

  The conductive particles used in the present invention are obtained by forming a metal film on the surface of the core particles described above by an electroless plating method or the like. As a method of forming a metal film on the surface of core particles, a wet method using an evaporation method, a sputtering method, a mechanochemical method, a dry method using an hybridization method etc., an electrolytic plating method, an electroless plating method etc It can be mentioned. In addition, these methods may be combined to form a metal film on the surface of the core particle.

  The size of the conductive particles is selected according to the application of the coated conductive powder. When the coated conductive powder produced according to the present invention is used as a conductive material for connecting an electronic circuit, the average particle diameter of the conductive particles is preferably 1 μm to 100 μm, more preferably 1.5 μm to 30 μm. If the average particle diameter of the conductive particles is within the above range, the resulting coated conductive powder can ensure conduction between the opposing electrodes without causing a short circuit between adjacent electrodes. In the present invention, the average particle diameter of the conductive particles is a value measured using an electrical resistance method.

  The shape of the conductive particles used in the present invention is not particularly limited. In general, the conductive particles are spherical. However, the conductive particles may have a shape other than particulates, for example, fibrous, hollow, plate-like or needle-like, and even if they have a large number of protrusions on their surface or are irregularly shaped. Good. In the present invention, spherical conductive particles are preferred in terms of excellent filling properties.

  The preferred conductive particles for use in the present invention are those in which the surface of the core particles is coated with a metal film consisting of one or more of gold, silver, copper, nickel, palladium, solder and the like. Among these, conductive particles in which a metal film is formed on the surface of a core particle by electroless plating are more preferable in that the surface of the core particle can be uniformly and densely covered with the metal film. Gold or palladium is preferred in that the metal film is more conductive. The metal film also includes alloys such as nickel-phosphorus alloy and nickel-boron alloy.

  When a metal film is formed on the surface of the core particles by electroless plating, the thickness of the metal film is preferably 0.001 μm to 2 μm, more preferably 0.005 μm to 1 μm. The thickness of the metal film can be calculated, for example, by the amount of metal ions to be coated and the chemical analysis.

  When the nickel film is formed by the electroless plating method, (1) catalyzing treatment step, (2) initial thin film formation step, and (3) electroless nickel plating step are performed. In the catalyzing treatment step of (1), after the core material particles having the ability to trap noble metal ions or to which the ability to trap noble metal ions is imparted by surface treatment are made to trap noble metal ions, they are reduced to reduce noble metals. It is supported on the surface of the core particle. In the initial thin film forming step (2), core particles on which a noble metal is supported are dispersed and mixed in an initial thin film forming solution containing nickel ions, a reducing agent and a complexing agent to reduce nickel ions to obtain core particles. An initial thin film of nickel is formed on the surface. In the electroless nickel plating step (3), a plated powder having a nickel film on the surface of the core particles is produced by electroless plating. These steps and other metal plating methods are all known (for example, JP-A 60-59070, JP-A 61-64882, JP-A 62-30885, JP-A 01-242782). Patent Publication Nos. 02-15176, 08-176836, 08-311655, 10-101962, 2000-243132, 2004-131800, See, for example, JP-A-2004-131801 and JP-A-2004-197160).

  When the core particles are subjected to the above-mentioned catalyzing treatment step (1), it is preferable that the surface be surface-modified so that the surface has the ability to capture precious metal ions or the ability to capture precious metal ions. . The noble metal ion is preferably an ion of palladium or silver. Having the ability to capture a precious metal ion means that the precious metal ion can be captured as a chelate or a salt. For example, when an amino group, an imino group, an amido group, an imide group, a cyano group, a hydroxyl group, a nitrile group or a carboxyl group is present on the surface of the core particle, the surface of the core particle has Have. When the surface is modified to have the ability to capture noble metal ions, the methods described in, for example, JP-A-61-64882, JP-A-2007-262495, etc. can be used.

  In addition, the conductive particles used in the present invention may be those in which an insulating layer made of resin is further formed on the surface of the conductive particles. Examples of such conductive particles include, for example, conductive particles described in JP-A-5-217617 and JP-A-5-70750.

  The surface of the coated conductive powder of the present invention may be a coupling such as a silane coupling agent, an aluminum coupling, a titanate coupling agent, or a zirconate coupling agent within the range not impairing the effects of the present invention. The surface may be treated with an agent or coated with an insulating resin.

  The coated conductive powder of the present invention preferably has a volume resistivity of 1 Ω · cm or less, more preferably 0.5 Ω · cm or less. The volume resistivity of the coated conductive powder can be adjusted by the thickness of the titanium oxide coated film. The coated conductive powder of the present invention is characterized in that it has excellent conductivity within the above range of volume resistivity. Therefore, the coated conductive powder of the present invention can be suitably used as a conductive filler such as a conductive adhesive. When the coated conductive powder of the present invention is used for a conductive adhesive, the conductive adhesive usually contains a coated conductive powder as a conductive filler and an adhesive resin. In the present invention, the volume resistivity of the coated conductive powder is determined by placing 1.0 g of a powder sample in a resin cylinder with an inner diameter of 10 mm and standing vertically, and applying a load of 10 kg to the upper and lower electrodes. Of the electric resistance between them. Moreover, the coated conductive powder which made the thickness of the titanium oxide coating film thick can also be used conveniently for the adhesive agent which it is desired to exhibit white.

  The conductive adhesive of the present invention is preferably disposed as an adherend member between two substrates on which a conductive portion is formed, and is preferably heated and pressed to bond the conductive portion and conduct electricity. It can be used. The anisotropic conductive adhesive of the present invention can provide highly reliable connection also to the electrode connection of an electronic component such as an IC chip to be miniaturized or a circuit board. Hereinafter, preferred embodiments of the anisotropic conductive adhesive will be described in detail.

  The anisotropic conductive adhesive of the present invention comprises the above-described coated conductive powder and an epoxy resin as an adhesive resin. As the epoxy resin, a polyvalent epoxy resin having two or more epoxy groups in one molecule used as an adhesive resin can be used. Specific examples thereof include novolac resins such as phenol novolac and cresol novolac, bisphenol A, bisphenol F, bisphenol AD, resorcinol, polyhydric phenols such as bishydroxydiphenyl ether, ethylene glycol, neopentyl glycol, glycerin, trimethylolpropane, Glycidyl obtained by reacting epichlorohydrin or 2-methylepichlorohydrin with polyhydric alcohols such as polypropylene glycol, polyamino compounds such as ethylenediamine, triethylenetetramine, aniline, etc., polybasic carboxy compounds such as adipic acid, phthalic acid, isophthalic acid etc. An epoxy resin of a mold is exemplified. In addition, aliphatic and alicyclic epoxy resins such as dicyclopentadiene epoxide, butadiene dimer epoxide, etc. may be mentioned. These may be used alone or in combination of two or more.

  Moreover, the anisotropic conductive adhesive of this invention may contain adhesion resin other than an epoxy resin as needed. Examples of the adhesive resin other than the epoxy resin include urea resin, melamine resin, phenol resin, silicone resin, acrylic resin, polyurethane resin, polyester resin and the like. These may be used alone or in combination of two or more.

  In addition, it is preferable from the prevention of ion migration to use high purity goods which reduced impurity ion (Na, Cl, etc.), hydrolysable chlorine, etc. as these adhesion resin.

The compounding amount of the coated conductive powder in the anisotropically conductive adhesive of the present invention is usually 0.1 to 30 parts by mass, preferably 0.5 to 25 parts by mass with respect to 100 parts by mass of the adhesive resin. Part, more preferably 1 part by mass to 20 parts by mass. When the amount of the coated conductive powder is in the above range, the connection resistance and the melt viscosity can be suppressed from being increased, the connection reliability can be improved, and the anisotropy of the connection can be sufficiently secured.
Additives known in the art can be used in the anisotropic conductive adhesive of the present invention, and the addition amount thereof may be within the addition amount known in the art. As such an additive, for example, a tackifier, a reactive auxiliary, a metal oxide, a photoinitiator, a sensitizer, a curing agent, a vulcanizing agent, a deterioration inhibitor, a heat resistance additive, a heat conduction improver And softeners, colorants, various coupling agents, metal deactivators and the like.

  Examples of the tackifier include rosin, rosin derivative, terpene resin, terpene phenol resin, petroleum resin, coumarone-indene resin, styrene resin, isoprene resin, alkylphenol resin, xylene resin and the like. Examples of reactive auxiliary agents, ie, crosslinking agents, include polyols, isocyanates, melamine resins, urea resins, utropins, amines, acid anhydrides, peroxides and the like.

  Any epoxy resin curing agent can be used without particular limitation as long as it has two or more active hydrogens in one molecule. Specific examples thereof include polyamino compounds such as diethylenetriamine, triethylenetetramine, metaphenylenediamine, dicyandiamide and polyamidoamine, and organics such as phthalic anhydride, methyl nadic anhydride, hexahydrophthalic anhydride and pyromellitic anhydride. Acid anhydrides, and also novolac resins such as phenol novolac, cresol novolac, etc. may be mentioned. These may be used alone or in combination of two or more. In addition, a latent curing agent may be used according to the application and the necessity. Examples of latent curing agents that can be used include imidazoles, hydrazides, boron trifluoride-amine complexes, sulfonium salts, amine imides, salts of polyamines, dicyandiamides and the like, and modified products thereof. These may be used alone or in combination of two or more.

  In the anisotropically conductive adhesive of the present invention, a coated conductive powder, an epoxy resin, a curing agent, and, if necessary, various additives are usually blended using a production apparatus widely used in the relevant technical field, It can be obtained by mixing in an organic solvent if necessary.

<Preparation of Peroxotitanic Acid Aqueous Solution>
The resulting precipitate was filtered and washed by adding 20 mL of 25% sodium hydroxide to 15 mL of a 15% titanium tetrachloride solution. 100 mL of 32% hydrogen peroxide was added to the precipitate, and the pH was adjusted to 10.5 with 28% aqueous ammonia to obtain an aqueous peroxotitanic acid solution.

Example 1
20 g of gold-coated nickel particles (Nippon Chemical Industry Co., Ltd .: trade name Bright 6 GNM 5-Ni) having an average particle diameter of 6.5 μm as conductive particles are dispersed in 300 mL of deionized water to form a slurry, and this slurry is stirred While maintaining the temperature at 80 ° C., the whole amount of the peroxotitanic acid aqueous solution prepared above was continuously dropped over 20 minutes. After completion of the dropwise addition, stirring was continued, and aging was performed by maintaining the temperature at 80 ° C. for 2 hours. After aging, the liquid was filtered, and the filtrate was washed three times with pulp, and then dried at 100 ° C. with a vacuum dryer to obtain coated conductive particles in which the conductive particle surfaces were coated with titanium oxide. The coating amount of titanium oxide determined from the used amount of the conductive particles and peroxotitanic acid is 10% by mass. It was confirmed by observation with a scanning electron microscope that a coating film of titanium oxide was uniformly formed on the surface of the conductive particles.

Example 2
Except that 30 g of gold-coated nickel particles having an average particle diameter of 2.5 μm (manufactured by Nippon Chemical Industrial Co., Ltd .: trade name Bright 19GNM2.5-Ni) was used instead of 20 g of gold-coated nickel particles having an average particle diameter of 6.5 μm In the same manner as in Example 1, a coated conductive powder was obtained.

Example 3
Except that 30 g of nickel-coated resin particles having an average particle diameter of 4.6 μm (manufactured by Nippon Chemical Industrial Co., Ltd .: trade name Bright 52 NR4.6-EHD) was used instead of 20 g of gold-coated nickel particles having an average particle diameter of 6.5 μm In the same manner as in Example 1, a coated conductive powder was obtained.

Example 4
Instead of 20 g of gold-coated nickel particles having an average particle diameter of 6.5 μm, 30 g of gold-nickel coated resin particles having an average particle diameter of 4.6 μm (manufactured by Nippon Chemical Industrial Co., Ltd .: trade name Bright 20 GNR 4.6-EH) was used A coated conductive powder was obtained in the same manner as Example 1 except for the above.

Comparative Example 1
Nickel-coated resin particles having an average particle diameter of 4.6 μm (Nippon Chemical Industry Co., Ltd .: trade name Bright 52 NR4.6-EHD) were used as they were.

Comparative Example 2
Gold-nickel coated resin particles having an average particle diameter of 4.6 μm (manufactured by Nippon Chemical Industrial Co., Ltd .: trade name Bright 20 GNR 4.6-EH) were used as they were.

Comparative Example 3
The coated conductive powder of Example 7 described in WO2009 / 054386 (patent document 3) was prepared.

Comparative Example 4
The coated conductive powder of Example 28 described in WO2009 / 054387 (patent document 4) was prepared.

<High temperature and high humidity treatment>
The coated conductive powder obtained in Examples 1 to 4, the conductive particles of Comparative Examples 1 to 2 or the coated conductive powder obtained in Comparative Examples 3 to 4 are maintained at a temperature of 60 ° C. and a humidity of 95%. It was placed in a high temperature and high humidity tank and left for 1000 hours.

<Measurement of volume specific resistance>
In a resin cylinder with an inner diameter of 10 mm vertically stood, 1.0 g of powder was placed, a load of 10 kgf was applied, and the electrical resistance between the upper and lower electrodes was measured to determine the volume specific resistance value. As powder, those before high temperature high humidity processing and those after high temperature high humidity processing were used.

  From the results of Table 1, the coated conductive powders of Examples 1 to 4 have good electrical conductivity, and even when subjected to high temperature and high humidity treatment at 60 ° C. and 95% RH for 1000 hours, the volume resistivity is Good electrical conductivity was maintained without an increase in value.

Preparation of Anisotropic Conductive Adhesive
As the number of the conductive filler in the obtained resin paste after kneading is 300 million / cm ^3, coated conductive powders in Examples 1 to 4, conductive particles or Comparative Example 3 Comparative Example 1-2 About 3 parts by mass to about 15 parts by mass of the coated conductive powder of ~ 4 as conductive filler, 100 parts by mass of epoxy main agent jER 828 (manufactured by Japan Epoxy Resins Co., Ltd.), curing agent AMICURE PN23J (manufactured by Ajinomoto Fine Techno Co., Ltd.) 30 parts by mass and 2 parts by mass of a viscosity modifier were kneaded for 1 minute with a planetary stirrer to obtain a paste. As the powder, one before the high temperature and high humidity treatment and one after the high temperature and high humidity treatment were used.

<Dispersibility evaluation>
The anisotropically conductive adhesive prepared above was applied onto a 100 micron thick PET film with a film thickness of 100 microns by an applicator. This was observed with an optical microscope at an area of 10 cm ² at 200 times, and the number of agglomerated particles having a major axis of 10 μm or more and agglomerated particles having a major axis of 8 μm or more and less than 10 μm was measured. The results evaluated according to the following criteria are shown in Table 2.
:: no aggregate particles are present ○: one or two aggregate particles are present ×: three or more aggregate particles are present

  From the results of Table 2, the coated conductive powders of Examples 1 to 4 were in a good dispersed state even at high temperature and high humidity treatment at 60 ° C. and 95% RH for 1000 hours.

<Implementation evaluation>
5 parts by mass of the coated conductive powder obtained in Examples 1 to 4, the conductive particles of Comparative Examples 1 to 2 or the coated conductive powder obtained in Comparative Examples 3 to 4, jER 828 (Japan Epoxy Resins Co., Ltd. 100 parts by mass, 30 parts by mass of a curing agent AMICURE PN23J (manufactured by Ajinomoto Fine Techno Co., Ltd.), and 2 parts by mass of a viscosity modifier with a planetary stirrer to obtain a paste, which is used as an adhesive sample. Next, the adhesive sample prepared above was applied in a size of 2.5 mm long × 2.5 mm wide × 0.05 mm thick on a substrate having an aluminum wiring formed on a PET film. A dummy IC having a gold pump was placed thereon, and thermocompression bonding was performed at 170 ° C. and a pressure of 2.0 N for 30 seconds to prepare a sample for resistance measurement.

<Pressure cooker test>
The resistance measurement samples obtained in the mounting test were arranged in a closed vessel, and pressure cracker tests (temperature 121 ° C., relative humidity 100%, 2 atm) were performed for 10 hours, and then resistance values were measured.

  From the results of Table 3, the coated conductive powders of Examples 1 to 4 have good conductivity immediately after connection, and maintain good conductivity without any increase in connection resistance even after the pressure cracker test. The

  The coated conductive powder according to the present invention can be connected with high reliability even to a connection structure such as a connection of an electronic component of an IC chip to be miniaturized or a circuit board while maintaining the conductive performance by the titanium oxide coating. A conductive adhesive can be provided. Furthermore, white can be exhibited by thickening the thickness of the titanium oxide coating film in the coated conductive powder.

Claims (10)

The surface of a conductive particle having a metal film formed on the surface of a core particle made of a resin material is covered with an aggregate of fine titanium oxide deposited from an alkaline solution containing peroxotitanic acid. Coated conductive powder. The average particle size of the conductive particles, coated conductive powder according to claim 1, characterized in that a 1 m to 100 m. The metal film formed on the surface of the conductive particles, gold, silver, copper, nickel, claim 1, characterized in that it consists of one or more members selected from the group consisting of palladium and solder, or 2. The coated conductive powder according to 2. The method for producing a coated conductive powder according to any one of claims 1 to 3,
An alkaline solution containing peroxotitanic acid is added to a suspension containing conductive particles in which a metal film is formed on the surface of core particles made of resin material, and titanium oxide is deposited on the surface of the conductive particles. A method of producing a coated conductive powder, comprising: The method for producing a coated conductive powder according to claim 4 , wherein the addition of the alkaline solution containing peroxotitanic acid is performed while maintaining the suspension at 35 ° C to 95 ° C while stirring. The coated conductive powder according to claim 4 or 5 , further comprising the step of maintaining the suspension at 50 to 95 ° C with stirring after addition of the alkaline solution containing peroxotitanic acid. Production method. The method for producing a coated conductive powder according to any one of claims 4 to 6 , wherein a solution containing peroxotitanic acid and ammonia is used as the alkaline solution containing peroxotitanic acid. A conductive adhesive comprising the coated conductive powder according to any one of claims 1 to 3 and an adhesive resin. 9. The conductive adhesive according to claim 8 , which is used as an anisotropic conductive adhesive. An adhesive structure, wherein members to be adhered are adhered to each other via the conductive adhesive according to claim 8 or 9 .

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