JP6469817B2 - Coated conductive powder, method for producing coated conductive powder, conductive adhesive containing coated conductive powder, and bonded structure - Google Patents

Description

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

  When electrically connecting circuit boards to each other or electronic components such as IC chips and the circuit board, an anisotropic conductive adhesive in which conductive particles are dispersed is used. These adhesives are arranged between the electrodes facing each other, the electrodes are connected to each other by heating and pressing, and then electrically connected and fixed by giving 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 coated with an insulator such as titanium oxide. For example, as a method for coating the surface of conductive particles with titanium oxide, a method of firmly fixing fine titanium oxide particles in a buried state on the surface of the conductive particles by a mechanofusion system or a hybridization system is known. (See Patent Documents 1 and 2).

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

Japanese Patent Laid-Open No. 07-118617 JP 2000-215730 A International Publication No. 2009/054386 Pamphlet International Publication No. 2009/054387 Pamphlet

  However, as disclosed in Patent Documents 1 and 2, in the method in which conductive particles are surface-modified / composited dry by the powerful impact force of the mechanofusion system or the hybridization system, fine titanium oxide particles are electrically conductive. Since the surface of the conductive particles is mechanically driven, the conductive particles are broken and deformed. In particular, when metal-coated resin particles plated on the surface of the resin particles as the core material are used as the conductive particles, there is a problem that peeling and deformation of the metal-coated film and deformation, cracking and destruction of the core material are caused. . Furthermore, since the coated conductive powder obtained in this way has a strong titanium oxide coating film, when used as an adhesive, the resin particles as the core material lose their flexibility when connected, and are electrically conductive. There is a concern that the electrode may be disturbed or bite into the opposing electrode and destroyed.

  In addition, the coated conductive powder obtained by the methods of Patent Documents 3 and 4 does not peel off the titanium oxide particles attached to the surface of the conductive particles due to external factors such as slight impact. When used as an agent, it can be peeled off from the conductive particles and uniformly diffused into 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. With recent miniaturization of electrodes of electronic parts and narrowing of wiring pitch, coated conductive powders with better dispersibility are required. In the coated conductive powders obtained by the methods of Patent Documents 3 and 4, There is a problem that such a request cannot be satisfied.

  Accordingly, 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 destruction and deformation of the conductive particles, and the coating film of the titanium oxide is soft and excellent in dispersibility. It is an object to provide a conductive powder, a method for producing the same, and an adhesive structure using the coated conductive powder.

  As a result of intensive research to solve the above-mentioned problems, the present inventors have used a peroxotitanic acid solution to form fine particles on the surface of conductive particles in which a metal film is formed on the surface of core material particles made of a resin material. And found that it is effective to make a coated conductive powder having a specific volume resistivity value, by depositing an appropriate titanium oxide and coating the surface of the conductive particles with titanium oxide. The present invention has been completed.

That is, the present invention provides a coated conductive powder in which the surface of conductive particles in which a metal film is formed on the surface of core material particles made of a resin material is coated with titanium oxide precipitated from an alkaline solution containing peroxotitanic acid. It is a coated conductive powder characterized by having a volume resistivity of 1 Ω · cm or less.
Further, the present invention adds an alkaline solution containing peroxotitanic acid to a suspension containing conductive particles in which a metal film is formed on the surface of core material particles made of a resin material, to the surface of the conductive particles. A method for producing a coated conductive powder comprising a step of depositing titanium oxide to form a coating film of titanium oxide, wherein the volume specific resistance value of the coated conductive powder is 1 Ω · cm or less. It is a method for producing a coated conductive powder, characterized in that the thickness of the titanium oxide coating film is adjusted.

  According to the present invention, the surface of the conductive particles is coated with fine titanium oxide without causing destruction and deformation of the conductive particles, and the coating film of the titanium oxide is soft and has good dispersibility. A certain coated conductive powder and a method for producing the same can be provided.

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

Hereinafter, the present invention will be described in detail.
Since the coated conductive powder of the present invention coats the surface of the conductive particles in which a metal film is formed on the surface of the core particles with fine titanium oxide precipitated from an alkaline solution containing peroxotitanic acid, The impact force as in the mechanofusion system or the hybridization system is not applied to the conductive particles, and the conductive particles are not broken or deformed. Moreover, since the coated conductive powder of the present invention is not coated with a continuous film of titanium oxide, but coated with fine titanium oxide that has been deposited, for example, as can be seen from the electron micrograph shown in FIG. The thickness of the titanium oxide coating film is not uniform over the entire surface, but varies depending on the location. Furthermore, since the coating film of titanium oxide is not strong and is reasonably soft, the flexibility of the coated conductive powder as a whole is ensured.

  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 titanium oxide coating film has thick and thin parts, but when used for conductive adhesive, the thin part is easily destroyed by external force during 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 at the thick location. If the thickness of the titanium oxide coating film is within the above range, it is easy to ensure conductivity. Note that the color tone of the coated conductive powder can be controlled by changing the thickness of the titanium oxide coating film. When the thickness of the titanium oxide coating film is reduced, titanium oxide is almost transparent, so that the obtained coated conductive powder exhibits the color of conductive particles. On the other hand, when the thickness of the titanium oxide coating film is increased, the resulting coated conductive powder has a gray to white color. Therefore, when the coated conductive powder of the present invention is used for optical applications, the thickness of the titanium oxide coating film may be further increased in consideration of light reflection and refraction.

Moreover, although the thickness of the titanium oxide coating film is as described above, 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 an external force at the time of connection. Is obtained.
The thickness and amount of the titanium oxide coating film can be arbitrarily 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 alkali hydroxide to the titanium solution. After washing the resulting white precipitate (titanium hydroxide), hydrogen peroxide is added and dissolved. Can be prepared.

  In the present invention, the titanium solution used for preparing the solution containing peroxotitanic acid is not particularly limited, and examples thereof include titanium alkoxide, titanium chloride solution, titanium sulfate solution, and titanium hydroxide solution. These may be used alone or in combination of two or more. The valence of titanium may be not only tetravalent but also trivalent. Among these, a titanium tetrachloride solution is preferable because of cost and ease of handling. The alkali hydroxide added to the titanium solution is not particularly limited, and examples thereof include aqueous solutions of alkali metal hydroxides such as ammonia water and sodium hydroxide. As the hydrogen peroxide used for dissolving the white precipitate (titanium hydroxide), a commercially available 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 preferable.

  The amount of hydrogen peroxide to be added is preferably 0.3 times to 60 times mol and more preferably 1 times to 54 times mol 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 with a practical addition amount.

  In order to promote dissolution of the white precipitate, an alkaline solution may be added together with hydrogen peroxide. Examples of the alkaline solution include sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, ammonium hydrogen carbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, and aqueous ammonia. These may be used alone or in combination of two or more. Among these, sodium hydroxide and aqueous ammonia are preferable because of easy 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 is present in a more stable state in the solution. If the pH is less than 8, and when the crystallinity of the TiO ₂ precipitated is deteriorated, it may precipitate at room temperature results observed. When the pH exceeds 14, it is not practical and there is a possibility that an alkali component remains in the obtained coated conductive powder. The pH may be adjusted by adding the above alkaline solution.

  To deposit titanium oxide on the surface of the conductive particles, an alkaline solution containing peroxotitanic acid may be dropped into a suspension in which the conductive particles are dispersed. When an alkaline solution containing peroxotitanic acid is dropped, titanium oxide gradually precipitates on the surface of the conductive particles. It contains peroxotitanic acid so 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. When the concentration of peroxotitanic acid is within the above range, titanium oxide can be efficiently deposited in a short time on the surface of the conductive particles. The concentration of the conductive particles in the suspension is preferably 0.1 g / L to 200 g / L, 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 more uniformly and efficiently in a short time on the surface of the conductive particles, and the agglomeration of the coated conductive powder. Can be suppressed.

  In addition, when the alkaline solution containing peroxotitanic acid is added dropwise, it is desirable to heat the suspension to 35 ° C. to 95 ° C., more preferably 45 ° C. to 95 ° C. while stirring the suspension. If the temperature at the time of precipitation is within the above range, titanium oxide can be efficiently precipitated 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, the suspension is preferably heated to 50 ° C. to 95 ° C., more preferably 60 ° C. to 95 ° C., preferably 10 minutes while stirring the suspension as necessary. It is desirable to age by holding for -5 hours, more preferably 30 minutes to 3 hours. When the aging temperature and time are within the above ranges, precipitation of titanium oxide on the surface of the conductive particles can be promoted.

Moreover, in order to age | cure | ripen more effectively, a suspension liquid can be processed under high temperature / high pressure after completion | finish of addition of the alkaline solution containing peroxotitanic acid. In general, an autoclave or the like is effective, but is not particularly limited as long as it can maintain a high temperature and a 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 within the above ranges, the 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 increased to the melting temperature of the core particles. In this case, the pressure is practically 300 kg / cm ² or less and the temperature is 300 ° C. or less.
Then, after aging, the suspension is filtered, and the filtrate is washed with repulp as necessary to remove the alkali component, and then dried to obtain a coated conductive powder.

  In addition, inorganic acid, organic acid, inorganic alkali, organic alkali, polymer, 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, a salt thereof, an aqueous ammonia solution, an ammonium salt, and the like may be added.

  The core material particles used in the present invention can be used without particular limitation, whether they are inorganic or organic. Inorganic core particles include metal particles such as gold, silver, copper, nickel, palladium, solder, alloys, glass, ceramics, silica, metal or non-metal oxides (including hydrates), and aluminosilicates. Examples thereof include metal silicate, metal carbide, metal nitride, metal carbonate, metal sulfate, metal phosphate, metal sulfide, metal acid salt, metal halide and carbon. On the other hand, examples of organic core particles include natural fibers, natural resins, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylic ester, polyacryl nitrile, polyacetal, ionomer, polyester, and the like. Examples thereof include a plastic resin, an alkyd resin, a phenol resin, a urea resin, a benzoguanamine resin, a melamine resin, a xylene resin, a silicone resin, an epoxy resin, and a diallyl phthalate resin. These may be used alone or in combination of two or more. Among these, the core particles made of a resin material are preferable in that the specific gravity is small compared to the core particles made of metal and hardly settles, the dispersion stability is excellent, and the electrical connection is easily maintained due to the elasticity of the resin. .

  The shape of the core particle is not particularly limited. In general, the core particles are spherical. However, the core 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 number of protrusions on its surface or an indefinite shape. In the present invention, spherical core particles are preferable from the viewpoint 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 material particles is within the above range, the obtained coated conductive powder can ensure conduction between the counter 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 electric resistance method.

Furthermore, there is a range in the particle size distribution of the core particles measured by the method described above. In general, the width of the particle size distribution of the powder is represented by a coefficient of variation represented by the following calculation formula (1).
Coefficient of variation (%) = (standard deviation / average particle size) × 100 (1)
A large coefficient of variation indicates that the distribution is broad, while a small coefficient of variation 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. This is because, when the conductive particles to which titanium oxide is fixed according to the present invention are used as the conductive particles in the anisotropic conductive film, there is an advantage that the effective contribution ratio for connection is increased.

Further, the other physical properties of the core material particles are not particularly limited, but in the case of the core material particles made of a resin material, the following formula (2):
K (kgf / mm ² ) = (3 / √2) × F × S−3 / 2 × R−1 / 2 (2)
[In the formula (2), F and S are respectively the load value (kgf) and the compression displacement (mm R is the radius (mm) of the core material particles measured with a micro compression tester (MCTM-500 manufactured by Shimadzu Corporation)] and the value of K defined by 10 kgf / mm ^{2 at} 20 ° C. What is in the range of 10,000 kgf / mm ² and the recovery rate after 10% compression deformation is in the range of 1% to 100% at 20 ° C. does not damage the electrodes when crimping the electrodes, It is preferable at the point which can fully contact.

  The conductive particles used in the present invention are obtained by forming a metal film on the surface of the above-described core material particles by an electroless plating method or the like. As a method of forming a metal film on the surface of the core particle, there are a dry method using a vapor deposition method, a sputtering method, a mechanochemical method, a hybridization method, a wet method using an electroplating method, an electroless plating method, etc. Can be mentioned. Moreover, you may form a metal membrane | film | coat on the surface of core material particle | grains combining these methods.

  As the size of the conductive particles, an appropriate size 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 size 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 counter 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 electric 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 powder, for example, a fiber shape, a hollow shape, a plate shape, or a needle shape, and may have a large number of protrusions on the surface or an irregular shape. Good. In the present invention, spherical conductive particles are preferable in terms of excellent filling properties.

  The conductive particles preferred for use in the present invention are those in which the surface of the core material particles is coated with a metal film composed 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 the core material particles by an electroless plating method are more preferable in that the surface of the core material particles can be uniformly and densely covered with the metal film. The metal film is preferably gold or palladium from the viewpoint of increasing the conductivity. The metal film also includes alloys such as nickel-phosphorus alloys and nickel-boron alloys.

  When the metal film is formed on the surface of the core material particles by the electroless plating method, 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 by, for example, the amount of metal ions to be coated or chemical analysis.

  When a nickel film is formed by an electroless plating method, (1) a catalytic treatment process, (2) an initial thin film forming process, and (3) an electroless nickel plating process are performed. In the catalyzing treatment step (1), the noble metal ions are captured by the core material particles that have the ability to capture noble metal ions or that have been given the ability to capture noble metal ions by surface treatment. It is carried on the surface of the core material particles. In the initial thin film forming step (2), the core material particles carrying the noble metal are dispersed and mixed in an initial thin film forming liquid containing nickel ions, a reducing agent and a complexing agent, and the nickel ions are reduced to reduce the core material particles. An initial thin film of nickel is formed on the surface. In the electroless nickel plating step (3), a plating powder having a nickel film on the surface of the core material particles is produced by electroless plating. These processes and other metal plating methods are all known (for example, JP-A-60-59070, JP-A-61-64882, JP-A-62-30885, JP-A-01-242787). JP, JP 02-15176, JP 08-176836, JP 08-31655, JP 10-101962, JP 2000-243132, JP 2004-131800, JP, 2004-131801, JP, 2004-197160, etc.).

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

  In addition, the conductive particles used in the present invention may be obtained by further forming an insulating layer made of a resin on the surface of the conductive particles. Examples of such conductive particles include conductive particles described in JP-A-5-217617, JP-A-5-70750, and the like.

  In addition, in the range which does not impair the effect of the present invention, the surface of the coated conductive powder of the present invention is coupled with a silane coupling agent, an aluminum coupling, a titanate coupling agent, a zirconate coupling agent or the like. It may be surface-treated with an agent, or may be 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 value of the coated conductive powder can be adjusted by the thickness of the titanium oxide coating film. One characteristic of the coated conductive powder of the present invention is that the volume resistivity value is in the above range and has excellent conductivity. For this reason, 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 value of the coated conductive powder is determined by placing 1.0 g of a powder sample in a vertically standing resin cylinder having an inner diameter of 10 mm and applying a load of 10 kg to the upper and lower electrodes. It is the value which measured the electrical resistance between. Further, the coated conductive powder having a thick titanium oxide coating film can also be suitably used for an adhesive that is desired to exhibit a white color.

  The conductive adhesive of the present invention is preferably used as an anisotropic conductive adhesive that is disposed between two substrates having conductive portions formed thereon as a member to be bonded, and is heated and pressurized to bond and conduct the conductive portions. Can be used. The anisotropic conductive adhesive of the present invention can make a highly reliable connection even for electronic components such as IC chips to be miniaturized and electrode connections of circuit boards. Hereinafter, preferred embodiments of the anisotropic conductive adhesive will be described in detail.

  The anisotropic conductive adhesive of the present invention includes 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 include novolak resins such as phenol novolak and cresol novolak, polyhydric phenols such as bisphenol A, bisphenol F, bisphenol AD, resorcin, and bishydroxydiphenyl ether, ethylene glycol, neopentyl glycol, glycerin, trimethylolpropane, Polyglycols such as polypropylene glycol, polyamino compounds such as ethylenediamine, triethylenetetramine, and aniline, polycarboxyl compounds such as adipic acid, phthalic acid, and isophthalic acid, and the like, and glycidyl obtained by reacting epichlorohydrin or 2-methylepichlorohydrin Examples of the type epoxy resin. Moreover, aliphatic and alicyclic epoxy resins such as dicyclopentadiene epoxide and butadiene dimer epoxide are listed. These may be used alone or in combination of two or more.

  Moreover, the anisotropic conductive adhesive of this invention may contain adhesive resins 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, and polyester resin. These may be used alone or in combination of two or more.

  As these adhesive resins, it is preferable to use a high-purity product in which impurity ions (such as Na and Cl) and hydrolyzable chlorine are reduced in order to prevent ion migration.

The blending amount of the coated conductive powder in the anisotropic 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. If the blending amount of the coated conductive powder is within the above range, it is possible to suppress an increase in connection resistance and melt viscosity, improve connection reliability, and sufficiently secure connection anisotropy.
Additives known in the art can be used for the anisotropic conductive adhesive of the present invention, and the addition amount may be within the range of additions known in the art. Examples of such additives include tackifiers, reactive auxiliaries, metal oxides, photoinitiators, sensitizers, curing agents, vulcanizing agents, deterioration inhibitors, heat resistant additives, and heat conduction improvers. , Softeners, colorants, various coupling agents, metal deactivators and the like.

  Examples of the tackifier include rosin, rosin derivatives, terpene resins, terpene phenol resins, petroleum resins, coumarone-indene resins, styrene resins, isoprene resins, alkylphenol resins, xylene resins and the like. Examples of the reactive assistant, that is, the crosslinking agent, include polyols, isocyanates, melamine resins, urea resins, utropines, amines, acid anhydrides, peroxides, and the like.

  As an epoxy resin hardening | curing agent, if it has two or more active hydrogen in 1 molecule, it can be used without a restriction | limiting in particular. Specific examples include polyamino compounds such as diethylenetriamine, triethylenetetramine, metaphenylenediamine, dicyandiamide, and polyamideamine, and organic compounds such as phthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and pyromellitic anhydride. Examples thereof include acid anhydrides and also novolak resins such as phenol novolak and cresol novolak. These may be used alone or in combination of two or more. Moreover, you may use a latent hardening | curing agent as needed and a use. Examples of the latent curing agent that can be used include imidazole series, hydrazide series, boron trifluoride-amine complexes, sulfonium salts, amine imides, polyamine salts, dicyandiamide, and the like, and modified products thereof. These may be used alone or in combination of two or more.

  The anisotropic conductive adhesive of the present invention is usually blended with a coated conductive powder, an epoxy resin, a curing agent, and further various additives as necessary, using a manufacturing apparatus widely used in the technical field. If necessary, it can be obtained by mixing in an organic solvent.

<Preparation of aqueous peroxotitanic acid solution>
20 mL of 25% sodium hydroxide was added to 15 mL of 15% titanium tetrachloride solution, and the resulting precipitate was filtered and washed. 100% of 32% hydrogen peroxide was added to the precipitate, and the pH was adjusted to 10.5 using 28% aqueous ammonia to obtain a peroxotitanic acid aqueous solution.

<Example 1>
20 g of gold-coated nickel particles having an average particle diameter of 6.5 μm as conductive particles (manufactured by Nippon Chemical Industry Co., Ltd .: trade name Bright 6GNM5-Ni) are dispersed in 300 mL of demineralized water to form a slurry, and this slurry is stirred. While maintaining at 80 ° C., the whole amount of the peroxotitanic acid aqueous solution prepared above was continuously added dropwise over 20 minutes. After completion of dropping, stirring was continued, and the mixture was kept at 80 ° C. for 2 hours for aging. After aging, the liquid was filtered, and the filtrate was washed with repulp three times, and then dried at 100 ° C. with a vacuum dryer to obtain coated conductive particles whose conductive particle surfaces were coated with titanium oxide. In addition, the coating amount of titanium oxide determined from the amount of conductive particles and peroxotitanic acid used is 10% by mass. Observation with a scanning electron microscope confirmed that a coating film of titanium oxide was uniformly formed on the surface of the conductive particles.

<Example 2>
Instead of using 20 g of gold-coated nickel particles having an average particle diameter of 6.5 μm, 30 g of gold-coated nickel particles having an average particle diameter of 2.5 μm (manufactured by Nippon Chemical Industry Co., Ltd .: trade name Bright 19GNM2.5-Ni) was used. Was the same as in Example 1 to obtain a coated conductive powder.

<Example 3>
Instead of using 20 g of gold-coated nickel particles having an average particle diameter of 6.5 μm, 30 g of nickel-coated resin particles having an average particle diameter of 4.6 μm (product name: Bright 52NR4.6-EHD, manufactured by Nippon Chemical Industry Co., Ltd.) Was the same as in Example 1 to obtain a coated conductive powder.

<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 (product name: Bright 20GNR4.6-EH, manufactured by Nippon Chemical Industry Co., Ltd.) was used. A coated conductive powder was obtained in the same manner as in Example 1 except that.

<Comparative Example 1>
Nickel-coated resin particles having an average particle size of 4.6 μm (manufactured by Nippon Chemical Industry Co., Ltd .: trade name BRIGHT 52NR4.6-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 Industry Co., Ltd .: trade name BRIGHT 20GNR4.6-EH) were used as they were.

<Comparative Example 3>
The coated conductive powder of Example 7 described in International Publication No. 2009/054386 pamphlet (Patent Document 3) was prepared.

<Comparative example 4>
A coated conductive powder of Example 28 described in International Publication No. 2009/054387 pamphlet (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 were kept at a temperature of 60 ° C. and a humidity of 95%. It was put in a high temperature and high humidity tank and left for 1000 hours.

<Measurement of volume resistivity>
A powder cylinder (1.0 g) was placed in a vertically standing resin cylinder with an inner diameter of 10 mm, and the electric resistance between the upper and lower electrodes was measured in a state where a load of 10 kgf was applied to obtain a volume resistivity value. As the powder, those before the high temperature and high humidity treatment and those after the high temperature and high humidity treatment were used.

  From the results of Table 1, the coated conductive powders of Examples 1 to 4 have good electrical conductivity, and also have a volume resistivity even when subjected to high temperature and high humidity treatment at 60 ° C. and 95% RH for 1000 hours. 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 4 to 15 parts by mass of the coated conductive powder of 4 to 4 as a conductive filler, 100 parts by mass of epoxy main agent jER828 (manufactured by Japan Epoxy Resin 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 with a planetary stirrer for 1 minute to obtain a paste. As the powder, those before and after the high-temperature and high-humidity treatment were used.

<Dispersibility evaluation>
The previously prepared anisotropic conductive adhesive was applied onto a PET film having a thickness of 100 μm and a thickness of 100 μm by an applicator. The area of 10 cm ² was observed 200 times with an optical microscope, and the number of aggregated particles having a major axis of 10 μm or more and the aggregated particles having a major axis of 8 μm or more and less than 10 μm were counted. The results of evaluation according to the following criteria are shown in Table 2.
A: There is no aggregated particle. O: There are 1 to 2 aggregated particles. X: There are 3 or more aggregated particles.

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

<Mounting evaluation>
5 parts by mass of coated conductive powder obtained in Examples 1 to 4, conductive particles of Comparative Examples 1 to 2 or coated conductive powder obtained in Comparative Examples 3 to 4, jER828 (Japan Epoxy Resin Co., Ltd.) 100 parts by mass), 30 parts by mass of curing agent Amicure PN23J (manufactured by Ajinomoto Fine Techno Co., Ltd.) and 2 parts by mass of a viscosity modifier were obtained by a planetary stirrer to obtain a paste, which was used as an adhesive sample. Next, the previously prepared adhesive sample was applied in a length of 2.5 mm × width 2.5 mm × thickness 0.05 mm on a substrate on which an aluminum wiring was formed on a PET film. A dummy IC having a gold pump was placed thereon and thermocompression bonded 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 sealed container and subjected to a pressure cracker test (temperature 121 ° C., relative humidity 100%, 2 atm) for 10 hours, and then the resistance value was measured.

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

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

Claims (10)

The surface of the conductive particles in which a metal film is formed on the surface of the core particles made of a resin material is a coated conductive powder coated with titanium oxide deposited from an alkaline solution containing peroxotitanic acid,
A coated conductive powder, wherein the coated conductive powder has a volume resistivity of 1 Ω · cm or less. The coated conductive powder according to claim 1 , wherein the conductive particles have an average particle size of 1 μm to 100 μm. 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. 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 material particles made of a resin material, and titanium oxide is precipitated on the surface of the conductive particles. A method for producing a coated conductive powder having a step of forming a coating film of titanium oxide,
A method for producing a coated conductive powder, comprising adjusting the thickness of the coating film of titanium oxide so that a volume specific resistance value of the coated conductive powder is 1 Ω · cm or less. The method for producing a coated conductive powder according to claim 4 , wherein the addition of the alkaline solution containing peroxotitanic acid is carried out while maintaining the suspension at 35 ° C to 95 ° C while stirring. After addition of the alkaline solution containing the peroxotitanate, the coated conductive powder according to claim 4 or 5, further comprising a step of maintaining the stirring 50 to 95 ° C. the suspension 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. The conductive adhesive according to claim 8 , wherein the conductive adhesive is used as an anisotropic conductive adhesive. Bonding structure be bonded members to each other via a conductive adhesive according to claim 8 or 9, characterized in that it is bonded.

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