KR20160084331A - Conductive powder and conductive material comprising thereof and method for preparing conductive particle - Google Patents

Abstract

The present invention provides conductive powder having conductivity and electric reliability which is equal to or higher than existing conductive powder consisting of conductive particles in the prior art having a gold plating film as an outermost layer. According to the present invention, conductive powder consists of conductive particles further having a palladium film on a nickel film particle surface having a nickel film on the surface of core material particles; conductive powder has 5 or more protruding portions, protruding from the surface of the palladium film, formed to be a continuum with the palladium film, and having a height of 50 nm or more, per one particle; a content of the palladium film is 3 wt% or less; and a ratio in which primary particles are occupied, of conductive particles, is 85 wt% or more with respect to the weight of conductive powder.

Description

TECHNICAL FIELD [0001] The present invention relates to a conductive powder, a conductive material containing the conductive powder, and a method for manufacturing the conductive particle. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a conductive powder and a conductive material containing the conductive powder. The present invention also relates to a method for producing conductive particles.

Conventionally, as the conductive powder used in the conductive adhesive, the anisotropic conductive film, the anisotropic conductive adhesive, etc., metal powder such as nickel, copper, silver, gold, solder and the like; Carbon-based materials such as carbon powder, carbon fiber and carbon flake; There is known a conductive particle in which the surface of the resin particle is electroless nickel plated and coated with nickel.

Among these conductive powders, the conductive particles coated with nickel on the surface of the resin particles tend to be oxidized in the nickel coating, which may increase the electrical resistance over time. Further, for the purpose of further enhancing the conductivity, a gold-plated coating film of a noble metal is usually formed on the nickel plating film.

In view of the high price of gold, it is considered that other precious metals are used as substitutes for gold. For example, palladium is proposed as the outermost layer, and conductive powders have been proposed (see Patent Documents 1 to 3). However, it is difficult to say that the outermost layer has properties equivalent to those of the conductive particles which are gold-plated coatings.

Japanese Patent Laid-Open Publication No. 11-134936 Japanese Patent Application Laid-Open No. 2007-194210 Japanese Patent Application Laid-Open No. 2004-238738

Accordingly, it is an object of the present invention to provide a conductive powder having the outermost layer of the above-mentioned gold plating layer and a conductive powder having the same or higher properties.

Means for Solving the Problems In order to achieve the above object, the inventors of the present invention have conducted intensive studies and, as a result of intensive studies, have found that the present inventors have found that a film- A coating film prepared by using palladium-coated particles produced in a specific range, a coating film containing substantially no phosphorus or adjusting the content of phosphorus to a specific range or less as a palladium or palladium alloy coating film, It is found that the outermost layer is a conductive powder comprising conductive particles, which is a gold-plated coating, and has the same or superior electrical conductivity and electrical reliability.

The present invention is based on the above finding and is an electroconductive powder comprising conductive particles in which a nickel or nickel alloy coating is formed on the surface of core particles and further a coating of palladium or palladium alloy is formed on the surface of nickel-

Wherein the conductive particles have at least 5 protrusions each having a height of 50 nm or more and protruding from the surface of the palladium or palladium alloy coating film and continuing with the palladium or palladium alloy coating,

The content of phosphorus in the palladium or palladium alloy coating is 3 wt% or less,

In the conductive powder, the proportion of the primary particles in the conductive particles is 85% by weight or more based on the weight of the conductive powder.

According to the present invention, there is also provided a method for manufacturing a core particle, comprising the steps of: forming a core material particle having a nickel or nickel alloy film on its surface and projecting from the surface of the core film and having a height of 50 nm or more, The present invention also provides a method for producing conductive particles characterized in that the nickel-coated particles are subjected to electroless palladium plating in the presence of a dispersion in any one of the following methods (D1) to (D3).

(D1) A method of reducing electroless palladium plating treatment with a pure palladium plating bath.

(D2) A method for reducing electroless palladium plating treatment wherein the molar ratio of the reducing agent to palladium ions is 0.1 to 100 in a reducing electroless palladium plating treatment using hypophosphoric acid or a salt thereof as a reducing agent.

(D3) substituted electroless palladium plating.

The conductive powder of the present invention has a conductivity equal to or higher than that of the conductive powder comprising the conductive particles of the prior art having a gold plated film as the outermost layer and has electrical reliability. Further, according to the production method of the present invention, such conductive powder can be easily produced.

Hereinafter, the present invention will be described based on preferred embodiments. The conductive powder of the present invention can be produced by coating a nickel or nickel alloy film (hereinafter collectively referred to simply as a " nickel film ") on the surfaces of the core particles with a nickel film or a palladium or palladium alloy film Simply referred to as " palladium film ") is further formed. The conductive powder of the present invention has one of the features in that it has a plurality of protrusions protruding from the surface of the palladium coating. Hereinafter, the protrusion will be described.

In the present invention, the individual protrusions in the conductive particles are continuous with the palladium coating, and the outermost layer of the protrusions is composed of at least a palladium coating. The term " continuum " as used herein means that there is no portion between the palladium coating and the protruding portion such as a joint which damages the sense of unity. Therefore, for example, since the protruding portion formed by forming the palladium coating on the core particle, adhering the core particle for forming the protrusion on the core particle, and the starting point of the growth of the core particle is not continuous with the palladium coating, Is not included in the continuum. Since the protrusions are continuous with the palladium coating, the strength of the protrusions is ensured, so that even when pressure is applied during use of the conductive powder, the protrusions are less prone to breakage. As a result, good conductivity can be obtained.

The protrusions in the conductive powder of the present invention are characterized in that the protrusions having a specific height or more exist in a specific range. That is, the conductive powder of the present invention has five or more protrusions each having a height of 50 nm or more per one particle. The upper limit value of the number of protrusions having a height of 5 nm or more per one particle is preferably 1,000 or less. The reason is that if the protrusions are too large, the distance between the protrusions and the protrusions becomes narrow, and the effect of the protrusions may be deteriorated. Particularly, the number of protrusions having a height of 50 nm or more is preferably 5 to 300 per one particle, because the conductivity is particularly excellent.

The protrusions having a height of 50 nm or more are preferably elongated protrusions extending substantially radially from the surface of the particles. The protrusions preferably have an aspect ratio of 1.0 or more, more preferably 1.1 or more. The reason for this is that when the electrode is made conductive by using the conductive powder of the present invention, there is a case where a thin oxide film is naturally formed on the surface of the electrode, or an oxide film of the electrode is formed intentionally, , It is considered that this oxide film can break through easily. In addition, when the anisotropic conductive film is formed using the conductive powder, if the aspect ratio of the protruding portion is large, the resin excretability is high, and therefore, the conductivity is considered to be high. As described above, it has been found by the inventors of the present invention that the aspect ratio of the protruding portion is 1.0 or more, that is, the shape of the protruding portion is made elongated and the conductivity becomes very high. Particularly, as apparent from the comparison between Examples 1 to 7 and Examples 8 to 10 in Examples to be described later, when the aspect ratio of the protrusions is 1.0 or more, deterioration of conductivity after storage for a long time under high temperature and high humidity is effectively suppressed . As far as the present inventors know, it is not easy to set the aspect ratio of the protrusions to 1 or more. The protrusions in the conventional conductive powder have a stocky shape, so to speak. Since the upper limit value of the aspect ratio tends to be easily broken when pressure is applied to the protruding portion, it is preferable that the upper limit value is 3.0 or less. Conductive particles having protrusions having such a large aspect ratio can be produced by, for example, a method described later.

The aspect ratio in the present invention is a value defined by the ratio of the height H of the protrusion to the width D of the protrusion in the base of the protrusion, that is, H / D. As is clear from this definition, the aspect ratio means that the projecting portion is thin and the length is the measure of the steaming, and the larger the value, the thinner the projecting portion is. This aspect ratio represents an average value of protrusions having a protrusion height of 50 nm or more.

The above-described aspect ratio measurement method is as follows. And enlarged and observed individual particles in the conductive powder by an electron microscope. With respect to at least one protrusion with respect to one particle, the length D and the height H of the base are measured. In this case, it is important from the viewpoint of accurate measurement that the protrusions existing in the periphery of the particle are to be measured rather than the protrusions present in the center of the particle on the observation. This measurement is performed on at least 20 different particles. The data of the plurality of aspect ratios thus obtained are arithmetically averaged, and the values are set as aspect ratios. Further, since the cross section of the projection has a small anisotropy shape (for example, almost circular shape), there is little possibility that the value of the length D of the base portion of the projection varies depending on the observation angle of the particle.

It is preferable that the aspect ratio of the protruding portion is as described above. The length D itself of the base portion of the protruding portion and the height H itself of the protruding portion are preferably 0.05 to 0.5 占 퐉, particularly 0.1 to 0.4 占 퐉 with respect to the length D of the base portion. 0.05 to 0.5 [mu] m, particularly preferably 0.1 to 0.4 [mu] m. When the length D of the base portion of the protrusion and the height H of the protrusion are within the range, the conductivity is further improved.

The protrusions having a height of 50 nm or more may have the above-mentioned number per particle. In addition to such protrusions, the presence of protrusions having a height of 50 nm or less in the conductive particles does not interfere with the present invention. However, if there are a plurality of protrusions having a height of 50 nm or less, the distance between the protrusions and the protrusions is narrowed, and the effect of the protrusions may be deteriorated. Therefore, the ratio of the protrusions having the aspect ratio satisfying the above- , Preferably not less than 40%, more preferably not less than 45%, still more preferably not less than 50%.

The conductive powder of the present invention is characterized by the content of phosphorus (P) contained in the palladium coating. Specifically, as a result of a study conducted by the present inventors, it has been found that when the palladium film contains more than 3% by weight of phosphorus, it affects conductivity and electrical reliability. Therefore, in the present invention, the content of phosphorus in the palladium coating is 3 wt% or less, preferably 2 wt% or less. The lower limit value of the phosphorus content is not particularly limited, and a smaller value is more preferable. The phosphorus content in the palladium film is measured by the method described in the following Examples.

The content of phosphorus contained in the coating film is not particularly limited as far as the nickel coating film located below the palladium coating film is concerned.

Regarding the thickness of the palladium coating, if it is too thin, the conductive powder tends not to exhibit sufficient conductivity. On the other hand, if it is too thick, it tends to peel off from the surface of the core particles. From these viewpoints, it is preferable that the thickness of the palladium coating at the portion where the protrusions do not exist is preferably 5 to 500 nm, more preferably 10 to 300 nm.

As the nickel film is too thin, the conductive performance tends to be inadequate. On the other hand, when the nickel film is too thick, the particles tends to flocculate. Thus, the thickness of the nickel film is preferably 10 to 300 nm, more preferably 50 to 250 nm desirable.

The thickness of the palladium coating and the thickness of the nickel coating on the conductive particles were measured by the method described in the following Examples.

The nickel coating located on the lower side of the palladium coating covers the surface of the core material particles to form nickel coating particles. Preferably, the nickel-coated particles are subjected to electroless nickel plating treatment of the core material particles to form a nickel film on the surface of the core material particles and to form protrusions. This is because the protrusions thus formed are more difficult to break. From this point of view, in the conductive powder of the present invention, the protrusions in the individual particles are preferably composed of protruding portion cores made of nickel or a nickel alloy and protruded portion covering layers made of palladium or palladium alloy covering the surface of the core Do. When the projecting portion has such a structure, it is preferable that the projecting portion core body is a continuous body with the nickel coating located below the palladium coating. It is preferable that the protruding portion coating layer is continuous with the palladium coating.

As the core material particles covered with the nickel coating, various materials may be used as described later. Particularly, when resin particles are used as the core material particles, the particle size distribution of the conductive powder to be obtained becomes sharp and the compression recovery property is excellent.

In the conductive powder of the present invention, the shape of each particle is preferably spherical. The shape of the particles referred to herein is the shape of the particles excluding the projecting portion. The conductive powder of the present invention has high conductivity because of its spherical shape and its protruding portion.

In the conductive powder of the present invention, the conductive powder having an average particle diameter of 1 to 50 μm, particularly 1 to 40 μm, particularly 1.5 to 30 μm, determined by the Coulter counter method described below in relation to the number of the projections described above Particles. By making conductive particles having particle diameters in this range, the number of protrusions per one particle and the density of the protrusions are balanced, and it is easy to increase the conductivity.

Conductive particles tend to flocculate when their particle diameters become smaller. If aggregation occurs, there is a problem that the anisotropic conductive film using conductive particles tends to cause a short circuit. In addition, when the treatment such as grinding is performed to solve the aggregation, the palladium coating and / or the nickel coating are peeled off, which causes the conductivity to deteriorate. From this point of view, in the conductive powder of the present invention, it is important to improve the dispersibility of individual particles. Therefore, in the conductive powder of the present invention, the proportion of the primary particles in the conductive particles is 85% by weight or more, preferably 90% by weight or more, more preferably 92% by weight or more based on the weight of the conductive powder. In order to enhance the dispersibility of the conductive particles, the conductive particles may be produced by, for example, a method described later. The ratio of primary particles is measured by the following method. 0.1 g of the conductive powder is added to 100 mL of water and dispersed for 1 minute in an ultrasonic homogenizer. Next, the particle size distribution is measured by a Coulter counter method. From the result, the weight ratio of the primary particles is calculated.

The palladium film in the conductive particles is composed of a metal palladium or a palladium alloy. Palladium alloys include, for example, palladium-phosphorus alloys. Palladium-phosphorus alloy is an alloy which is generated when sodium hypophosphite is used as a reducing agent of palladium in the production of a conductive powder to be described later.

Further, the nickel coating on the conductive particles is composed of metallic nickel or a nickel alloy. Nickel alloys include, for example, nickel-phosphorus alloys. The nickel-phosphorus alloy is an alloy which is generated when sodium hypophosphite is used as a reducing agent of nickel in the production of a conductive powder to be described later.

Next, a suitable production method of the conductive powder of the present invention will be described. According to the present manufacturing method, a protruding portion having a height of 50 nm or more, which is formed on the surface of the core material particles and has a coating of nickel or nickel alloy and which protrudes from the surface of the coating and is continuous with the coating, Nickel-coated particles (hereinafter simply referred to as " nickel-coated particles ") are subjected to electroless palladium plating in any one of the following methods (D1) to (D3) in the presence of a dispersant.

(D1) A method of reducing electroless palladium plating treatment with a pure palladium plating bath.

(D2) A method for reducing electroless palladium plating treatment wherein the molar ratio of the reducing agent to palladium ions is 0.1 to 100 in a reducing electroless palladium plating treatment using hypophosphoric acid or a salt thereof as a reducing agent.

(D3) substituted electroless palladium plating.

If the nickel-coated particles are obtained by any one of the following two methods (b1) and (b2), the strength of the protrusions is so strong that the protrusions are unlikely to break even when pressure is applied during use of the conductive powder, It is preferable from the viewpoint of possibility.

(b1) an electroless nickel plating bath containing a dispersant and nickel ions, and a core material particle carrying noble metal on its surface, and forming a nickel initial thin film layer on the surface of the core material particle, An A1 step of using the core particles in an amount such that the sum of the surface areas is 1 to 15 m ² per 1 liter of the electroless nickel plating bath adjusted to 0.0001 to 0.008 mol /

The aqueous slurry containing the core particles having the nickel initial thin film layer obtained in the step A1 and the aqueous slurry containing the dispersing agent is kept in the pH range in which the dispersing effect of the dispersing agent is exhibited, (Hereinafter referred to as " b1 production method ") in which an amount of nickel ions and an reducing agent are added with time in an amount equivalent to 100 nm.

(b2)

A step B1 of adding an aqueous slurry of the core particles to an electroless nickel plating bath containing a dispersant, a nickel salt, a reducing agent, a complexing agent, and the like, followed by electroless nickel plating, and then, the electroless nickel plating bath was immersed in an electroless nickel plating solution (Hereinafter, referred to as " b2 production method ") in which at least two liquid components are separated, and each of them is simultaneously and agedly electroless nickel plated.

The shape of the core material particles used in the production methods of b1 and b2 has a great influence on the shape of the intended conductive particles. As described above, since the thickness of the nickel coating film covering the surface of the core material particles and the palladium coating are thin, the shape of the core material particles is mostly reflected in the shape of the conductive particles. Since the conductive particles are preferably spherical as described above, it is preferable that the shape of the core material particles is spherical.

When the core particles are spherical, the particle size of the core particles greatly affects the particle diameter of the intended conductive particles. As described above, since the thicknesses of the nickel coating and the palladium coating covering the surface of the core material particles are thin, the particle size of the core material particles is mostly reflected in the particle diameter of the conductive particles. From this viewpoint, the particle size of the core particles can be made to be the same as the particle size of the intended conductive particles. Specifically, the average particle size determined by the Coulter counter method is preferably 1 to 50 μm, particularly 1 to 40 μm, particularly preferably 1.5 to 30.0 μm.

The particle size distribution of the core material powder measured by the above method is wide. Generally, the width of the particle size distribution of the powder is represented by the coefficient of variation represented by the following expression (1).

<Formula 1>

Coefficient of variation (%) = (standard deviation / average particle diameter) x 100

A larger coefficient of variation indicates that the distribution has a width, while a smaller coefficient of variation indicates that the particle size distribution is sharp. In the present invention, it is preferable to use this core particle having a coefficient of variation of 30% or less, particularly 20% or less, and particularly 10% or less. This is because, when the conductive particles of the present invention are used as the conductive particles in the anisotropic conductive film, there is an advantage that the effective contribution ratio to the connection is increased.

Specific examples of the core particles include an oxide (including hydrous) of a metal (including an alloy), glass, ceramics, silica, carbon, a metal or a nonmetal, a metal silicate including an aluminosilicate, Nitrides, metal carbonates, metal sulfates, metal phosphates, metal sulfides, metal halides, metal halides and carbon. Examples of the organic material include natural fibers, natural resins, thermoplastic resins such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylic acid ester, polyacrylonitrile, polyacetal, ionomer and polyester, , Phenol resin, urea resin, melamine resin, benzoguanamine resin, melamine resin, xylene resin, silicone resin, epoxy resin or diallyl phthalate resin. These may be used alone or as a mixture of two or more.

Further, the other physical properties of the core particles are not particularly limited, but when the core particles are resin particles, the K value defined by the following formula 2 is preferably 10 kgf / mm ² to 10000 kgf / mm ² , And the recovery rate after 10% compression deformation is preferably in the range of 1% to 100% at 20 캜. By satisfying these physical property values, it is possible to sufficiently bring the electrodes into contact with each other without damaging the electrodes when the electrodes are pressed against each other.

<Formula 2>

F and S denoted by the formula 2 are the load value (kgf) at 10% compressive strain of the microspheres and the compressive displacement (kgf) when measured with a micro compression tester MCTM-500 (manufactured by Shimadzu Corporation) (mm), and R is the radius (mm) of the microspheres.

It is preferable that the surface of the core particle is surface-modified so as to have a trapping ability of a noble metal ion or a trapping ability of a noble metal ion. The noble metal ions are preferably palladium or silver ions. The ability to trap noble metal ions means that noble metal ions can be captured as chelates or salts. For example, when an amino group, an imino group, an amide 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 material particles, the surface of the core material particles has a capping ability I have. When the surface is modified to have a trapping ability of a noble metal ion, for example, the method described in Japanese Patent Application Laid-Open No. 61-64882 can be used.

By using such core particles, a noble metal is carried on the surface thereof. Specifically, the core material particles are dispersed in an acidic aqueous solution in which a noble metal salt such as palladium chloride or silver nitrate is lean. This allows noble metal ions to be trapped on the surface of the particles. The concentration of the noble metal salt in the range of 1 x 10 ^-7 to 1 x 10 ^-2 moles per m ² of the surface area of the particles is sufficient. The core particles in which noble metal ions are trapped are separated from the system and washed with water. Subsequently, the core material particles are suspended in water, and a reducing agent is added thereto to perform reduction treatment of noble metal ions. Whereby the noble metal is carried on the surface of the core material particles. As the reducing agent, for example, sodium hypophosphite, sodium borohydride, potassium borohydride, dimethylamine borane, hydrazine, and formalin are used.

Before the noble metal ions are trapped on the surface of the core particles, a sensitization treatment may be performed in which tin ions are adsorbed on the surface of the particles. In order to adsorb tin ions to the surfaces of the particles, for example, the surface-modified core particles may be put into an aqueous solution of tin chloride and stirred for a predetermined time.

Hereinafter, the production method of the above-mentioned b1 will be described in more detail. The present manufacturing method includes (1) an A1 step of forming a nickel initial thin film layer on the surface of the core material particles, and (2) a step A2 of forming an objective conductive particle by using the particles obtained in the A1 step as a raw material . Hereinafter, each step will be described.

In the step A1, an electroless nickel plating bath containing a dispersant and nickel ions and a core material particle bearing noble metal on its surface are mixed to form a nickel initial thin film layer on the surface of the core material particles.

The core particles described above are mixed with an electroless nickel plating bath containing a dispersant and nickel ions. The electroless nickel plating bath is a solution containing water as a medium. Examples of the dispersing agent include nonionic surfactants, amphoteric surfactants and / or water-soluble polymers. As the nonionic surfactant, polyoxyalkylene ether surfactants such as polyethylene glycol, polyoxyethylene alkyl ether, and polyoxyethylene alkyl phenyl ether can be used. Examples of the amphoteric surfactant include betaine surfactants such as alkyldimethyl acetate betaine, alkyldimethylcarboxymethylacetate betaine, and alkyldimethylaminoacetic acid betaine. As the water-soluble polymer, polyvinyl alcohol, polyvinyl pyrrolidinone, hydroxyethyl cellulose and the like can be used. The amount of the dispersing agent to be used depends on the kind thereof, but is generally 0.5 to 30 g / L based on the volume of the liquid (electroless nickel plating bath). Particularly, when the amount of the dispersing agent used is in the range of 1 to 10 g / L with respect to the volume of the liquid (electroless nickel plating bath), it is preferable from the viewpoint of improving the adhesion of the nickel coating.

The nickel ion contained in the electroless nickel plating bath uses a water-soluble nickel salt as its nickel source. As the water-soluble nickel salt, nickel sulfate or nickel chloride can be used, but it is not limited thereto. The concentration of nickel ions contained in the electroless nickel plating bath is preferably 0.0001 to 0.008 mol / liter, particularly 0.0001 to 0.005 mol / liter.

The electroless nickel plating bath may contain a reducing agent in addition to the above-mentioned components. As the reducing agent, the same one as used for the reduction of the noble metal ions described above can be used. The concentration of the reducing agent in the electroless nickel plating bath is preferably 4 × 10 ^-4 to 2.0 mol / liter, particularly preferably 2.0 × 10 ^-3 to 0.2 mol / liter.

The electroless nickel plating bath may further contain a complexing agent. The advantageous effect that the decomposition of the plating liquid is suppressed by containing the complexing agent appears. Examples of the complexing agent include an organic carboxylic acid or a salt thereof, such as citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid or gluconic acid or an alkali metal salt or ammonium salt thereof. These complexing agents may be used alone or in combination of two or more. The concentration of the complexing agent in the electroless nickel plating bath is preferably 0.005 to 6 mol / liter, particularly 0.01 to 3 mol / liter.

There is no particular limitation on the method of mixing the pretreated core particles and the electroless nickel plating bath. For example, the electroless nickel plating bath may be heated to a temperature at which the nickel ion can be reduced, and the pre-treated core particles may be introduced into the electroless nickel plating bath under the condition. By this operation, nickel ions are reduced, and nickel generated by the reduction forms an initial thin film layer on the surface of the core material particles. The initial thin film layer is preferably formed to have a thickness of 0.1 to 10 nm, particularly 0.1 to 5 nm. At this point, protrusions are not yet formed.

An important point in the A1 process is the relationship between the amount of nickel ions contained in the electroless nickel plating bath and the amount of core particles injected. Concretely, the total sum of the surface areas is 1 to 15 m ² , preferably 1 to 10 m ² per 1 liter of the electroless nickel plating bath whose nickel ion concentration is adjusted to 0.0001 to 0.008 mol / liter, preferably 0.0001 to 0.005 mol / 2 uses the amount of the core particles as it is a ² to 8 m. Thus, the initial thin film layer having the above-mentioned thickness can be easily formed. Furthermore, by making the relationship between the amount of nickel ions and the amount of core particles as described above, it is possible to effectively prevent aggregation of core particles in which the initial thin film layer is formed. This is particularly effective when the particle size of the core particles is small, for example, when the particle size is 3 μm or less.

When the reduction of nickel ions is completed, the A2 step is performed. The step A2 is continued to the step A1, and the operation such as separating the core material particles having the nickel initial thin film layer obtained in the step A1 from the liquid is not performed. Therefore, the dispersant added in the Al process remains in the aqueous slurry containing the core material particles having the nickel initial thin film layer. In the step A2, nickel ions and a reducing agent are added over time to the aqueous slurry containing the core material particles having the nickel initial thin film layer obtained in the step A1 and the dispersant used in the step A1. The term &quot; addition over time &quot; is intended to exclude adding nickel ions and a reducing agent at a time, and it is intended to add nickel ions and a reducing agent continuously or intermittently over a certain period of time. In this case, the addition timing of the nickel ion and the reducing agent may be completely matched, or the addition of the nickel ion may be preceded, and the addition of the reducing agent may be followed. It could be the opposite. Further, at the end of the addition, the addition of the nickel ion may precede the addition, and the addition of the reducing agent may be followed by the addition. It could be the opposite.

As the nickel source of the nickel ion used in the step A2, the same nickel sources as those used in the A1 process can be used. The same is true for the reducing agent.

In the step A2, nickel particles of minute nickel are first produced in the solution by the reduction of nickel ions, the nuclear particles are adhered to the surface of the core material particles having the nickel initial thin film layer obtained in the process, And this is grown to form a protruding core body made of nickel. By employing this method, aggregation of particles can be effectively prevented, and protrusions having an aspect ratio of 1 or more at a height of 50 nm or more can be easily formed.

In the reduction of the nickel ion in the step A2, it is important to maintain the aqueous slurry in a pH range in which the dispersing effect of the dispersing agent added in the step A1 (the dispersing agent remains in the step A2) is exhibited. Thus, aggregation of the particles can be effectively prevented. To adjust the pH, an acid such as various inorganic acids or an alkali such as sodium hydroxide may be added to the aqueous slurry while monitoring the pH of the aqueous slurry. The adjustment range of the pH may be appropriately selected depending on the dispersing agent to be used. When a nonionic surfactant is used as the dispersant, for example, the pH of the aqueous slurry is preferably maintained in the range of 5 to 10. When a positive ion surfactant is used as the dispersing agent, it is preferable to maintain the pH of the aqueous slurry in the range of 5 to 8. [ Even when a water-soluble polymer is used as the dispersing agent, it is preferable to maintain the pH of the aqueous slurry in the range of 5 to 8. [

In the reduction of the nickel ion in the step A2, the amount of nickel ion added to the aqueous slurry and the amount of the reducing agent are also important. As a result, it is possible to form the projecting portion cores with high aspect ratios well. As concrete conditions, an amount of nickel ion and a reducing agent are added to the aqueous slurry in an amount corresponding to the amount of nickel precipitation of 25 to 100 nm, preferably 40 to 60 nm per hour, over time. By adopting such a condition of addition, nickel precipitation occurs more preferentially in the core particle than in the initial thin film layer, and the projected core having a high aspect ratio is easily formed.

In the addition of the nickel ion and the reducing agent, the aqueous slurry may be heated to a predetermined temperature so that the reduction of the nickel ion by the reducing agent proceeds smoothly. In the addition of the nickel ion and the reducing agent, the aqueous slurry may be stirred so that the reduced nickel is uniformly adhered. Thus, the intended nickel-coated particles are obtained.

Next, the production method of the above-mentioned b2 will be described in detail. Step B1 in this manufacturing method is an electroless nickel plating process in which an aqueous slurry of core particles and an electroless nickel plating bath including a dispersant, a nickel salt, a reducing agent, and a complexing agent are mixed. In this B1 step, the nickel plating film is formed on the core particles, and the plating bath self-decomposes. Since the magnetorolysis occurs in the vicinity of the core particles, the magnetostriction is trapped on the surface of the core material particles at the time of formation of the nickel coating, so that nuclei of the fine protrusions are formed, and at the same time, the nickel coating is formed. And the protruding core body is grown starting from the nucleus of the generated fine protrusions.

In the step B1, an aqueous slurry is prepared by thoroughly dispersing the core particles mentioned above in water preferably in the range of 1 to 500 g / L, more preferably 5 to 300 g / L. The dispersion operation can be usually carried out using a shear dispersion apparatus such as stirring, high-speed stirring or a colloid mill or a homogenizer. Ultrasonic waves may also be used in combination for the dispersion operation. If necessary, a dispersing agent such as a surfactant may be added in the dispersing operation. Then, an electroless plating B1 step is carried out by adding an aqueous slurry of the core particles subjected to the dispersion operation to an electroless nickel plating bath containing a nickel salt, a reducing agent, a complexing agent and various additives.

Examples of the above-mentioned dispersant include nonionic surfactants, amphoteric surfactants and / or water-soluble polymers. As the nonionic surfactant, polyoxyalkylene ether surfactants such as polyethylene glycol, polyoxyethylene alkyl ether, and polyoxyethylene alkyl phenyl ether can be used. Examples of the amphoteric surfactant include betaine surfactants such as alkyldimethyl acetate betaine, alkyldimethylcarboxymethylacetate betaine, and alkyldimethylaminoacetic acid betaine. As the water-soluble polymer, polyvinyl alcohol, polyvinyl pyrrolidinone, hydroxyethyl cellulose and the like can be used. These dispersants may be used alone or in combination of two or more. The amount of the dispersing agent to be used depends on the kind thereof, but is generally 0.5 to 30 g / L based on the volume of the liquid (electroless nickel plating bath). Particularly, when the amount of the dispersing agent used is in the range of 1 to 10 g / L with respect to the volume of the liquid (electroless secondary plating bath), it is preferable from the viewpoint of further improving the adhesion of the nickel coating.

As the nickel salt, for example, nickel chloride, nickel sulfate or nickel acetate is used, and the concentration thereof is preferably set in the range of 0.1 to 50 g / L. As the reducing agent, for example, sodium hypophosphite, dimethylaminoborane, sodium borohydride, potassium borohydride or hydrazine is used, and the concentration is preferably in the range of 0.1 to 50 g / L. Examples of the complexing agent include carboxylic acids (salts) such as citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid or its alkali metal salts or ammonium salts, amino acids such as glycine, amine acids such as ethylenediamine, Other compounds having a complexing action with respect to nickel ions such as ammonium, EDTA or pyrophosphoric acid (salt) may be used, and these may be used singly or in combination of two or more. The concentration thereof is preferably in the range of 1 to 100 g / L, more preferably 5 to 50 g / L. The pH of the preferred electroless nickel plating bath at this stage is in the range of 4-14. The electroless nickel plating reaction starts quickly when an aqueous slurry of core particles is added and involves the generation of hydrogen gas. The electroless plating B1 process is terminated when the generation of the hydrogen gas becomes completely invisible.

Subsequently, in step B2, the first aqueous solution containing (i) one of the nickel salt, the reducing agent and the alkali and the second aqueous solution containing the remaining two species are used, or (ii) A first aqueous solution containing a nickel salt, a second aqueous solution containing a reducing agent, and a third aqueous solution containing an alkali, and these aqueous solutions are simultaneously added to the liquid of the step B1, Nickel plating is performed. When these liquids are added, the plating reaction is started again, but the nickel coating formed by adjusting the addition amount can be controlled to a desired film thickness. After the completion of the addition of the electroless nickel plating solution, the generation of the hydrogen gas becomes completely invisible, and stirring is continued while maintaining the liquid temperature for a while to complete the reaction.

In the case of (i), it is preferable to use a first aqueous solution containing a nickel salt, and a second aqueous solution containing a reducing agent and an alkali, but the combination is not limited thereto. In this case, the reducing agent and the alkali are not included in the first aqueous solution, and the nickel salt is not included in the second aqueous solution. As the nickel salt and the reducing agent, those described above can be used. As the alkali, for example, a hydroxide of an alkali metal such as sodium hydroxide or potassium hydroxide can be used. The same applies to the case (ii).

In the case of (ii) above, the first to third aqueous solutions each contain a nickel salt, a reducing agent and an alkali, and each of the aqueous solutions does not contain two components other than the component.

In both cases (i) and (ii), the concentration of the nickel salt in the aqueous solution is preferably 50 to 400 g / L, especially 100 to 300 g / L. The concentration of the reducing agent is preferably 50 to 1000 g / L, particularly preferably 50 to 900 g / L. The concentration of the alkali is preferably 10 to 300 g / L, particularly preferably 20 to 250 g / L.

The B2 step is performed continuously after the end of the B1 step, but the B1 step and the B2 step may be interrupted instead. In this case, after the completion of the step B1, the core particles and the plating liquid are separated by a method such as filtration to newly disperse the core particles in water to prepare an aqueous slurry, and the complexing agent is added thereto in an amount of preferably 1 to 100 g / L, more preferably 5 to 50 g / L, and the dispersing agent is added in the range of preferably 0.5 to 30 g / L, more preferably 1 to 10 g / L A method in which an aqueous slurry is prepared by dissolving the aqueous slurry in the aqueous slurry, and the above-mentioned aqueous solution is added to the aqueous slurry. Thus, the intended nickel-coated particles are obtained.

Further, in the production methods of b1 and b2, the nickel-coated particles can be subjected to a pulverizing step using a ball mill. This pulverization step can provide mono-pulverized nickel-coated particles, and the mono-pulverized nickel-coated particles can be subjected to electroless palladium plating treatment to be described later to form a uniform palladium-plated film on the particle surfaces of the individual particles And the ratio of the primary particles to the weight of the conductive powder can be more easily set within the above-mentioned range after the electroless palladium plating treatment.

In the present invention, the production method of b1 can be effectively used regardless of the size of the core material particles, but in particular, the core material particles having fine core particles having an average particle diameter of 1 to 10 mu m are electroless nickel plated , And is particularly effective when nickel-coated particles having protruding core bodies are obtained. On the other hand, the production method of b2 is particularly effective when nickel-coated particles having protruding core bodies are obtained by electroless nickel plating on relatively large core particles of 3 to 50 mu m.

The nickel-coated particles thus obtained can be subjected to electroless palladium plating treatment in any one of the following methods (D1) to (D3) in the presence of a dispersant to obtain a desired conductive powder.

(D1) A method of reducing electroless palladium plating treatment with a pure palladium plating bath.

(D2) A method for reducing electroless palladium plating treatment wherein the molar ratio of the reducing agent to palladium ions is 0.1 to 100 in a reducing electroless palladium plating treatment using hypophosphoric acid or a salt thereof as a reducing agent.

(D3) substituted electroless palladium plating.

The reduction type electroless palladium plating method of (D1) and (D2) is to deposit palladium ions in the plating liquid by the function of a reducing agent to deposit palladium on the nickel plating film. Further, in the plating method of (D1), for example, by using a formic acid compound as a reducing agent, an electroless palladium plating film having a purity of 99 wt% or more can be obtained. On the other hand, in the reducing electroless palladium plating method of (D2), a plating film made of a palladium-phosphorus alloy is obtained by using hypophosphoric acid or a salt thereof as a reducing agent.

Hereinafter, a method for performing reduction type electroless palladium plating treatment with a pure palladium plating bath of (D1) will be described. The pure palladium plating bath is composed of an aqueous solution containing a palladium compound, a reducing agent and a complexing agent as essential components. In the present invention, the palladium plating treatment is performed by reducing the palladium plating bath containing the dispersant and the nickel-coated particles.

The palladium compound is not particularly limited as long as it is soluble in a plating solution and can obtain an aqueous solution having a predetermined concentration. And water-soluble palladium compounds such as palladium sulfate, palladium chloride, palladium nitrate, palladium acetate, dichlorodiethylenediamine palladium, and tetraamine palladium dichloride. These may be used alone or in combination of two or more. A palladium solution obtained by dissolving palladium as a palladium compound may also be used. As the palladium solution, for example, a dichlorodiethylenediaminepalladium solution or a tetraammine dichloride solution can be used. The content of the palladium compound in the pure palladium plating bath is preferably 0.1 to 30 g / L, more preferably 0.3 to 10 g / L as palladium.

Formic acid or a salt thereof is used as the reducing agent. The content of the reducing agent in the pure palladium plating bath is preferably 0.1 to 100 g / L, more preferably 1 to 50 g / L.

Examples of the complexing agent include amines such as ethylenediamine and diethylenetriamine; Aminopolycarboxylic acids such as ethylenediamine diacetic acid, ethylenediaminetetraacetic acid, and diethylenetriamine pentaacetic acid, and sodium, potassium, and ammonium salts thereof; Amino acids such as glycine, alanine, iminodiacetic acid, nitrilotriacetic acid, L-glutamic acid, L-glutamic acid diacetic acid, L-aspartic acid and taurine; sodium salts, potassium salts and ammonium salts thereof; Aminoethyltrimethylenephosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, ammonium salts thereof, potassium salts and sodium salts thereof. The complexing agent may be used alone or in combination of two or more. The content of the complexing agent in the pure palladium plating bath is preferably about 0.5 to 100 g / L, and more preferably about 5 to 50 g / L.

Examples of the dispersing agent include nonionic surfactants, amphoteric surfactants and water-soluble polymers. As the nonionic surfactant, polyoxyalkylene ether surfactants such as polyethylene glycol, polyoxyethylene alkyl ether, and polyoxyethylene alkyl phenyl ether can be used. Examples of the amphoteric surfactant include betaine surfactants such as alkyldimethyl acetate betaine, alkyldimethylcarboxymethylacetate betaine, and alkyldimethylaminoacetic acid betaine. As the water-soluble polymer, polyvinyl alcohol, polyvinyl pyrrolidinone, hydroxyethyl cellulose and the like can be used. The amount of the dispersing agent to be used depends on the kind thereof, but it is generally 0.5 to 30 g / L based on the volume of the liquid (pure palladium plating bath). In particular, when the amount of the dispersing agent used is in the range of 1 to 10 g / L with respect to the volume of the liquid (pure palladium plating bath), the adhesion of the palladium coating is improved and the effect of further suppressing the generation of aggregated particles is enhanced .

The pH of the electroless palladium plating reaction is preferably 3 to 10, more preferably 4 to 7 because a stable precipitation rate is obtained. For pH adjustment, for example, sulfuric acid, hydrochloric acid, sodium hydroxide, ammonia water and the like can be used. The reaction temperature is preferably from 20 to 90 캜, particularly from 40 to 80 캜, from the viewpoint of obtaining a smooth and dense coating film.

In addition, the pure palladium plating bath may contain a common additive such as a stabilizer. As the pure palladium plating bath containing such an additive, for example, a commercially available product commercially available from Nippon Kanzhen Kabushiki Kaisha, Kojima Kagaku Kohin Kabushiki Kaisha, and Chuo Kagaku Kogyo Kabushiki Kaisha may be used.

Next, a reduction type electroless palladium plating method using hypophosphoric acid or a salt thereof as the reducing agent (D2) will be described. (D2), a palladium-phosphorus plating bath is used. The palladium-phosphorus plating bath is composed of an aqueous solution containing a palladium compound, a reducing agent of hypophosphoric acid or its salt, and a complexing agent as essential components. In the present invention, the palladium-phosphorus plating bath, the dispersant, and the nickel-coated particles are mixed to perform reduction electroless palladium plating treatment.

As the palladium compound, the reducing agent, the complexing agent and the dispersing agent, the same amount as that of the reduced electroless palladium plating method of the above-mentioned (D1) can be used in the same addition amount.

In the reduced palladium plating method of (D2), the phosphorus content in the palladium coating is adjusted by adjusting the amount of the reducing agent to the palladium ion in a specific range. Generally, the phosphorus content in the palladium coating increases as the amount of the hypophosphorous acid or its salt of the reducing agent is increased relative to the palladium ion. In the reduced electroless palladium plating of (D2), it is preferable to set the molar ratio of the reducing agent to palladium ion to a lower range than the conventional one. That is, the phosphorus content in the palladium coating is adjusted to 3 wt% or less, preferably 0.5 to 3 wt% by reducing electroless palladium plating treatment by setting the molar ratio of the reducing agent to the palladium ion to 0.1 to 100. If the amount of the reducing agent added to the palladium ion is less than 0.1, the precipitation rate decreases and it is not practical. On the other hand, if the amount of the reducing agent is larger than 100, the phosphorus content in the palladium film becomes greater than 5 wt% Or less. In particular, in the present invention, the molar ratio of the reducing agent to palladium ions is preferably in the range of 1 to 30. [

The pH of the electroless palladium-phosphorus plating reaction is preferably 5 to 10, more preferably 5.5 to 9. By setting the pH within this range, the stability of the plating solution is enhanced and defects such as cracks are less likely to occur in the palladium coating. For adjustment of the pH, for example, sulfuric acid, hydrochloric acid, sodium hydroxide, ammonia water and the like can be used. The reaction temperature is preferably 25 to 80 DEG C, particularly 40 to 70 DEG C, from the viewpoint of obtaining a smooth and dense coating film.

In addition, the palladium-phosphorus plating bath may contain a common additive such as a stabilizer. As the palladium-phosphorus plating bath containing such an additive, for example, a commercially available product commercially available from Kojima Kagaku Co., Ltd., Ishihara Yakuhin Kabushiki Kaisha, etc. can be used.

Next, the method of plating the substituted electroless palladium of (D3) will be described. (D3), a substitutional electroless palladium plating is carried out by a substitution reaction of palladium ions and nickel ions to form a palladium-plated film on the nickel-coated particles.

The substitutional electroless palladium plating bath is composed of an aqueous solution containing a palladium compound and a complexing agent as essential components. In the present invention, the substitutional electroless palladium plating bath contains a dispersant and the nickel-coated particles to carry out the substitutional electroless palladium plating treatment.

The palladium compound, the complexing agent and the dispersing agent can be used in the same amount as that in the above-mentioned reduced electroless palladium plating method of (D1). In the case of using a tetraammine palladium salt as the palladium compound, a dense palladium film is preferably obtained.

When the substitutional electroless palladium plating reaction is carried out at a pH of 3 to 10, particularly 4 to 8, a smooth and dense film is easily obtained, which is preferable. For pH adjustment, for example, sulfuric acid, hydrochloric acid, sodium hydroxide, ammonia water and the like can be used. The reaction temperature is preferably from 25 to 80 캜, particularly from 30 to 70 캜, because the reaction speed is as high as practicable, and a precise palladium film is easily obtained.

After completion of the plating reaction of (D1) to (D3), the powder is separated by filtration by a conventional method and dried to obtain a conductive powder. If necessary, the conductive powder may be subjected to a pulverizing step using a ball mill as described in the method for producing the nickel-coated particles described above. By carrying out the pulverizing step, the ratio of the primary particles to the weight of the conductive powder can be more easily set within the above-mentioned range.

The conductive particles of the present invention thus obtained are suitably used, for example, as an anisotropic conductive film (ACF), a heat seal connector (HSC), a conductive material for connecting electrodes of a liquid crystal display panel to a circuit board of a driving LSI chip do. In particular, the conductive powder of the present invention is preferably used as a conductive filler of a conductive adhesive.

The conductive adhesive agent is preferably used as an anisotropic conductive adhesive agent which is disposed between two substrates on which an electrically conductive substrate is formed and conducts by bonding the electrically conductive substrate by heating and pressing. The anisotropic conductive adhesive includes the conductive particles of the present invention and the adhesive resin. The adhesive resin is not particularly limited as long as it is insulating and used as an adhesive resin. Thermoplastic resin and thermosetting property, and it is preferable that adhesion performance is exhibited by heating. Such adhesive resins include, for example, a thermoplastic type, a thermosetting type, and an ultraviolet curing type. There are also so-called semi-thermosetting type, thermosetting type and ultraviolet curing type combined type which exhibit the intermediate property between the thermoplastic type and the thermosetting type. These adhesive resins can be appropriately selected in accordance with the surface characteristics of the circuit board or the like to be adhered or the use form thereof. Particularly, an adhesive resin comprising a thermosetting resin is preferable in view of excellent material strength after bonding.

Specific examples of the adhesive include ethylene-vinyl acetate copolymer, carboxyl-modified ethylene-vinyl acetate copolymer, ethylene-isobutyl acrylate copolymer, polyamide, polyimide, polyester, polyvinyl ether, polyvinyl butyral, poly Butadiene rubber, styrene-butadiene rubber, styrene-butadiene rubber, styrene-butadiene rubber, styrene-butadiene rubber, styrene-butadiene rubber, styrene-butadiene rubber, One or two selected from the group consisting of an isoprene copolymer, an acrylonitrile-butadiene rubber (hereinafter referred to as NBR), a carboxyl-modified NBR, an amine-modified NBR, an epoxy resin, an epoxy ester resin, an acrylic resin, Or a combination of two or more of them. Of these, styrene-butadiene rubber, SEBS and the like are preferable as the thermoplastic resin because of excellent reworkability. As the thermosetting resin, an epoxy resin is preferable. Of these, an epoxy resin is most preferable from the viewpoint of high adhesion, heat resistance, electrical insulation, low melt viscosity and connection at low pressure.

As the epoxy resin, a commonly used epoxy resin can be used as long as it is a polyvalent epoxy resin having two or more epoxy groups in a molecule. Specific examples thereof include novolak resins such as phenol novolak and cresol novolak; polyhydric phenols such as bisphenol A, bisphenol F, bisphenol AD, resorcin and bishydroxydiphenyl ether; polyhydric phenols such as ethylene glycol, neopentyl glycol, glycerol, trimethylol Propane and polypropylene glycol, polyamino compounds such as ethylenediamine, triethylenetetramine and aniline, polyhydric carboxy compounds such as adipic acid, phthalic acid and isophthalic acid, and epichlorohydrin or 2-methyl epichlorohydrin And glycidyl type epoxy resins obtained by reacting hydrin. And aliphatic and alicyclic epoxy resins such as dicyclopentadiene epoxide and butadiene dimer diepoxide. These may be used alone or in combination of two or more.

It is preferable to use a high-purity product in which the impurity ions (such as Na and Cl) and hydrolyzable chlorine are reduced in the above-mentioned various adhesive resins from the viewpoint of prevention of ion migration.

The amount of the conductive particles of the present invention in the anisotropic conductive adhesive is usually 0.1 to 30 parts by weight, preferably 0.5 to 25 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the adhesive resin component. When the amount of the conductive particles used is within this range, it is possible to suppress the increase of the connection resistance and the melt viscosity, thereby improving the connection reliability and sufficiently securing the anisotropy of the connection.

In addition to the conductive particles and the adhesive resin described above, additives known in the art can be blended into the anisotropically conductive adhesive, and the blending amount thereof can be within the range known in the art. Examples of other additives include additives such as a tackifier, a reactive additive, an epoxy resin curing agent, a metal oxide, a photoinitiator, a sensitizer, a curing agent, a vulcanizing agent, a deterioration inhibitor, a heat resistant additive, a thermal conductivity improving agent, a softening agent, And the like can be exemplified.

Examples of the tackifier include rosin, rosin derivatives, terpene resins, terpene phenol resins, petroleum resins, coumarone-indene resins, styrene resins, isoprene resins, alkylphenol resins and xylene resins. Examples of the reactive auxiliary agent, that is, the crosslinking agent include polyols, isocyanates, melamine resins, urea resins, utopin, amines, acid anhydrides, peroxides and the like. The epoxy resin curing agent is not particularly limited 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; Organic acid anhydrides such as phthalic anhydride, methylnaphthalic anhydride, hexahydrophthalic anhydride, and pyromellitic anhydride; Novolak resins such as phenol novolak and cresol novolak, and the like. These may be used alone or in combination of two or more. In addition, a latent curing agent can be used depending on the application and the necessity. Examples of the latent curing agent that can be used include imidazole-based, hydrazide-based, boron trifluoride-amine complexes, sulfonium salts, amine imides, salts of polyamines, dicyandiamides and the like and modifications thereof. These may be used alone or as a mixture of two or more kinds.

The anisotropic conductive adhesive may be prepared by blending the conductive particles and the adhesive resin of the present invention and, if necessary, a curing agent and various additives, using a manufacturing apparatus widely used among those skilled in the art. When the adhesive resin is a thermosetting resin, By mixing, in the case of a thermoplastic resin, it is produced by melt-kneading at a temperature equal to or lower than the softening point of the adhesive resin, specifically about 50 to 130 ° C, and more preferably about 60 to 110 ° C. The anisotropic conductive adhesive thus obtained may be applied or may be applied in the form of a film.

<Examples>

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to these embodiments. Unless specifically stated otherwise, "%" means "% by weight".

[Production of nickel-coated particle sample N1]

(1) Step A1

(Total particle size: 3 μm, manufactured by Nippon Shokubai Co., Ltd .; trade name: Soliostar, coefficient of variation (CV): 3.2%]] having a true specific gravity of 1.1 was added to the core particles ² ). 9 g thereof was added to 400 mL of a conditioner aqueous solution ("Cleaner-conditioner 231" manufactured by Rohm and Haas Electronic Materials) with stirring. The concentration of the conditioner aqueous solution was 40 ml / L. Subsequently, the mixture was stirred for 30 minutes while applying ultrasonic waves at a liquid temperature of 60 占 폚 to carry out surface modification and dispersion treatment of the core particles. The aqueous solution was filtered to make a 200 mL slurry of the core material particles that had been washed once with repulp. 200 ml of an aqueous solution of tin chloride was added to this slurry. The concentration of this aqueous solution was 5 × 10 ^-3 mol / L. The mixture was stirred at room temperature for 5 minutes, and subjected to a sensitization treatment in which tin ions were adsorbed on the surface of the core particles. Subsequently, the aqueous solution was filtered and rinsed with water once. The core particles were then made into 400 ml slurry and maintained at 60 占 폚. 2 mL of a 0.11 mol / L aqueous solution of palladium chloride was added while stirring the slurry using ultrasonic waves. The same stirring state was maintained for 5 minutes to carry out an activation treatment for trapping palladium ions on the surface of the core material particles.

Then, an electroless plating bath 3 composed of an aqueous solution of 20 g / L of sodium tartrate, 5.4 g / L of sodium hypophosphite, nickel sulfate hexahydrate (0.45 g / L in anhydrous form) and 5 g / L of polyethylene glycol L was heated to 70 占 폚, and 9 g of core particles carrying palladium on this electroless plating bath was introduced to start the A1 process. It was confirmed that the foaming of the hydrogen which had been stirred for 5 minutes was stopped, and the step A1 was completed.

(2) Step A2

300 mL of a mixed aqueous solution containing 224 g / L of nickel sulfate aqueous solution, 210 g / L of sodium hypophosphite and 80 g / L of sodium hydroxide was used, and these were mixed with a slurry of the core material particles obtained in the step A1, To initiate the electroless plating A2 process. All the addition rates were 2.5 mL / min. The pH from the start of dropping to the end of dropping was 5.8 to 6.2, and the deposition amount of nickel per hour was 48 nm. After the whole amount of the liquid was added, stirring was continued for 5 minutes while maintaining the temperature at 70 캜. Subsequently, the liquid was filtered, the filtrate was washed three times, and then dried with a vacuum dryer at 100 ° C to obtain a nickel-coated particle sample N1 having a nickel-phosphorus alloy coating.

[Production of nickel-coated particle sample N2]

(1) Step B1

The core particles used in the production of N1 were subjected to the same surface modification treatment as that in the A1 process to carry out an activation treatment for trapping palladium on the surface of the core material. Subsequently, 3 L of an electroless plating bath consisting of 20 g / L of sodium tartrate, 4.5 g / L of nickel sulfate hexahydrate, 5.4 g / L of sodium hypophosphite and 5 g / L of polyethylene glycol dissolved was dissolved in 70 Deg.] C, and 9 g of the core material particles carrying palladium on this electroless plating bath were introduced to start the B1 step. The mixture was stirred for 5 minutes to confirm that the foaming of hydrogen stopped, and the step B1 was completed.

(2) Step B2

300 mL of a mixed aqueous solution containing 224 g / L of an aqueous solution of nickel sulfate, 210 g / L of sodium hypophosphite and 80 g / L of sodium hydroxide was used, and these were added to the slurry of the core material particles obtained in the step B1, And the mixture was continuously added by fractionation pump to initiate the electroless plating B2 process. All the addition rates were 2.5 mL / min. After the whole amount of the liquid was added, stirring was continued for 5 minutes while maintaining the temperature at 70 캜. Subsequently, the liquid was filtered, the filtrate was washed three times, and then dried with a vacuum dryer at 100 ° C to obtain a nickel-coated particle sample N2 having a nickel-phosphorus alloy coating.

[Preparation of nickel-coated particle N3 (comparative product)]

The surface of the core material was subjected to surface modification treatment with respect to the core material particles used in the production of N1, palladium was captured on the surface of the core material, and 20 g / L of sodium tartrate and 5 g / L of polyethylene glycol Was added to 3 L of the aqueous solution with stirring and sufficiently stirred and dispersed to prepare an aqueous slurry. Then, an aqueous slurry containing 224 g / L of an aqueous solution of nickel sulfate, 210 g / L of sodium hypophosphite and 80 g / 300 mL of the mixed aqueous solution was used. The addition rates were 5 mL / min. After the whole amount of the liquid was added, stirring was continued for 5 minutes while maintaining the temperature at 70 캜. Subsequently, the liquid was filtered, the filtrate was washed three times, and then dried with a vacuum dryer at 100 ° C to obtain a nickel-coated particle sample N3 having a nickel-phosphorus alloy coating. By this method, a film excellent in smoothness was obtained.

[Preparation of nickel-coated particle N4 (comparative product)]

The surface of the core material used in the production of N1 was subjected to the same surface modification treatment as that in the step A1, and an activation treatment for capturing palladium on the surface of the core material was carried out. Subsequently, a nickel-coated particle sample N4 having a nickel-phosphorus alloy coating film was obtained, except that polyethylene glycol was not added to the plating bath.

[Evaluation of physical properties of nickel-coated particles]

The average particle diameter of the nickel-coated particles N1 to N4, the thickness of the nickel coating, and the adhesion of the nickel coating were measured and evaluated, respectively. Further, the number of protruding core bodies having a height of 50 nm or more and the aspect ratio of the protruding core bodies having a height of 50 nm were measured. Each physical property was evaluated by the following method. These results are shown in Table 1.

[Thickness of Nickel Coating]

The nickel-coated particles were immersed in aqua regia to dissolve the nickel coating, ICP or chemical analysis of the coating component, and the thickness of the nickel coating was calculated from the following equations (3) and (4).

<Expression 3>

<Formula 4>

Wherein, r is the radius (μm), t is the thickness of the nickel coating film, d ₁ is the proportion of the nickel coating film, d ₂ is the proportion of the core material particles, W, Ni content (% by weight) of core particle.

[Number of protrusion core bodies and aspect ratio]

SEM was used to enlarge the nickel-coated particles by 30,000 times to observe 10 fields of view to calculate the average value of aspect ratios for the number of protruding core bodies having a height of 50 nm or more and the protruding core bodies having a height of 50 nm or more .

[Adhesion of Nickel Coating]

2 g of nickel-coated particles and 90 g of zirconia beads having a diameter of 1 mm were placed in a 100 mL beaker, and 10 mL of toluene was further added. After stirring for 10 minutes with an agitator, the zirconia beads and the slurry were separated and dried. The dried nickel-coated particles were magnified 2000 times using SEM to observe the 10 field of view, and the average value of the number of peeling pieces generated by stirring was calculated. The number of delamination pieces was less than 10, the delamination was 10, the number of delamination was 30, and the number of delamination was more than 30 pieces.

[Examples 1 to 3]

10 g / L of EDTA-2 Na, 10 g / L of citric acid-2 Na and 20 g / L of tetraammine palladium hydrochloride (Pd (NH ₃ ) ₄ Cl ₂ ) solution (2 g / L as palladium) An electroless palladium plating solution consisting of methyl cellulose (molecular weight: 250000, etherification degree: 0.9) and 100 ppm was prepared. 0.65 L of this palladium plating solution (Example 1), 1.3 L (Example 2) and 2.6 L (Example 3) were heated to 70 캜. With stirring, 10 g of the nickel-coated particle sample (N1) obtained above was added. Thus, electroless plating was performed on the surface of the particles. The treatment time was 60 minutes. After completion of the treatment, the liquid was filtered and the filtrate was repulped three times. Followed by drying in a vacuum dryer at 110 deg. Thus, the nickel-phosphorus alloy film was coated with palladium plating.

[Example 4]

A solution of 10 g / L ethylenediamine, 10 g / L sodium formate and 20 g / L tetraammine palladium hydrochloride (Pd (NH ₃ ) ₄ Cl ₂ ) solution (2 g / L as palladium), carboxymethylcellulose 250000, etherification degree: 0.9) and 100 ppm of palladium. 1.3 L of the palladium plating solution was heated to 70 캜, and 10 g of the nickel-coated particle sample (N1) obtained above was added thereto while stirring. Thus, electroless plating was performed on the surface of the particles. The treatment time was 30 minutes. After the completion of the treatment, the liquid was separated by filtration. Thereafter, the same processes as in Example 1 were carried out, and palladium plating coating treatment was performed on the nickel-phosphorus alloy film.

[Example 5]

10 g / L of ethylene diamine, 50 g / L of sodium hypophosphite in and 20 g / L of tetra-ammin palladium hydrochloride _{(Pd (NH 3) 4 Cl} 2) solution (2 g / L as palladium), carboxymethyl cellulose ( A molecular weight of 250,000, and an etherification degree of 0.9) of 100 ppm. 1.3 L of the palladium plating solution was heated to 50 캜, and 10 g of the nickel-coated particle sample (N1) obtained above was added thereto while stirring. Thus, electroless plating was performed on the surface of the particles. The treatment time was 30 minutes. After the completion of the treatment, the liquid was separated by filtration. Thereafter, the same processes as in Example 1 were carried out, and palladium plating coating treatment was performed on the nickel-phosphorus alloy film.

[Examples 6 and 7]

The procedure of Example 5 was repeated except that the concentration of sodium hypophosphite was changed to 10 g / L (Example 6) and 25 g / L (Example 7), palladium-phosphorus plating treatment was performed on the nickel alloy film Respectively.

[Examples 8 to 10]

The procedure of Example 2, Example 4, and Example 5 was repeated except that N2 was used as the nickel-coated particles, and palladium-phosphorus plating coating treatment was performed on the nickel-phosphorus alloy film.

[Comparative Examples 1 to 3]

The procedure of Example 2, Example 4, and Example 5 was repeated except that N3 was used as the nickel-coated particles, and palladium plating or palladium-phosphorus plating coating treatment was performed on the nickel-phosphorus alloy film.

[Comparative Examples 4 to 6]

The procedure of Example 2, Example 4, and Example 5 was repeated except that N4 was used as the nickel-coated particles, and palladium plating or palladium-phosphorus plating coating treatment was performed on the nickel-phosphorus alloy film.

[Comparative Example 7]

The procedure of Example 5 was repeated except that the concentration of sodium hypophosphite was changed to 200 g / L, and palladium-phosphorus plating coating treatment was performed on the nickel alloy film.

[Reference Example 1 (gold plating)]

An electroless gold plating solution consisting of 10 g / L of EDTA-4 Na, 10 g / L of citric acid-2 Na and 2.9 g / L of gold potassium cyanide (2.0 g / L as Au) was prepared. 2 liters of the gold plating solution was heated to 79 DEG C, and 10 g of the nickel-coated particles N1 was added thereto while stirring. Thus, electroless plating was performed on the surface of the particles. The treatment time was 20 minutes. After completion of the treatment, the liquid was filtered and the filtrate was repulped three times. Followed by drying in a vacuum dryer at 110 deg. Thus, the nickel-phosphorus alloy film was subjected to gold plating coating treatment.

[Evaluation of physical properties of conductive powder]

The thickness of the palladium coating, the thickness of the gold coating, the phosphorus content in the palladium coating, the number of protrusions having a height of 50 nm or more, the height of the protrusions having a height of 50 nm or more, the average particle diameter of the conductive particles obtained in Examples, And the ratio of the primary particles to each other were measured and evaluated. These results are shown in Table 2 below. Further, adhesion, conductivity, occurrence of short (electrical reliability) and resistance value of the palladium coating or gold coating were measured and evaluated, respectively. These results are shown in Table 3 below. The particle size of the conductive particles, the number of protrusions having a height of 50 nm or more, the aspect ratio of the protrusions having a height of 50 nm or more, and the adhesion of the palladium coating or gold coating were measured and evaluated in the same manner as in the nickel covering particles. The thickness of the nickel film, the thickness of the palladium film or gold film, the phosphorus content in the palladium film, the conductivity, the occurrence (electrical reliability), and the resistance value of the shot were measured and evaluated as follows.

[Thickness of Nickel Coating after Palladium Plating or Gold Plating]

The conductive particles were immersed in aqua regia to dissolve the metal coating, ICP or chemical analysis of the coating component, and the thickness of the nickel coating was calculated from the following equations (5) and (6).

<Expression 5>

<Expression 6>

Wherein, r is the radius of the core material particles (μm), t is the thickness of the nickel coating film, d ₁ is the proportion of the nickel coating film, d ₂ is the proportion of the core material particles, W is a nickel content (wt.%), X is gold Or the content of palladium.

[Thickness of Gold Film and Palladium Film]

The conductive particles were immersed in aqua regia to dissolve the nickel, gold or palladium coating, ICP or chemical analysis of the coating component, and the thickness of the gold or palladium coating was calculated from the following 7 and 8.

<Expression 7>

<Expression 8>

In the formula, u is the thickness of gold or palladium, d ₃ is the specific gravity of the gold or palladium coating, d ₄ is the specific gravity of the Ni product, and X is the content of gold or palladium (wt%). Here, the specific gravity d ₄ of the Ni product is calculated. The specific gravity was calculated using the following equation (9).

<Expression 9>

[Phosphorus content in palladium film]

The nickel particles before the palladium coating were immersed in aqua regia to dissolve the nickel coating, and the component of the coating was subjected to ICP or chemical analysis to calculate the metallization ratio. Further, after dissolving the nickel and palladium coatings of the palladium-coated particles, ICP or chemical analysis of the coating components was performed to calculate the metallization ratio, and the phosphorus content in the palladium coating was calculated by the following calculation formula.

The phosphorus content (g) in the nickel-

<Expression 10>

The phosphorus content (g) in the palladium-

<Expression 11>

The palladium content (g) in the palladium-

<Expression 12>

Therefore, the phosphorus content E (% by weight) in the palladium coating is

<Expression 13>

V is the weight (g) of the nickel-coated particles before the palladium treatment, Y ₁ is the phosphorus content (wt%) of the nickel-coated particles, Y ₂ is the phosphorus content (wt%) of the palladium coating particles, W is the metallization rate to be. However, since the elution of nickel and phosphorus from the nickel film was very small, it was calculated as 0.

[Conductivity, occurrence of short (electrical reliability), resistance value]

100 parts of an epoxy resin, 150 parts of a curing agent and 70 parts of toluene were mixed to prepare an insulating adhesive. And 15 parts of the conductive particles were blended to obtain a paste. The paste was applied on a silicone-treated polyester film using a bar coater and dried. Using the obtained coated film, a connection was made between a glass on which the entire surface was vapor-deposited with aluminum and a polyimide film substrate on which a copper pattern was formed with a pitch of 50 μm. The conductivity of the conductive particles was evaluated by measuring the conduction resistance between the electrodes. The evaluation was evaluated as?, The resistance value was 2? Or less,? Was 2 to 5? And? Was 5 or more. In addition, the presence or absence of occurrence of a shot was also observed. Further, the resistance value measured after holding at 500 캜 under the condition of 85 캜 and 85% RH was also measured.

Claims (4)

A conductive powder comprising conductive particles having a nickel or nickel alloy coating formed on the surface of core particles having an average particle diameter of 1 to 50 占 퐉 and further coated with a palladium or palladium alloy coating on the surface of the nickel-
The conductive particles having at least 5 protrusions each having a height of 50 nm or more and an aspect ratio of 1.0 or more and protruding from the surface of the palladium or palladium alloy coating film and continuing with the palladium or palladium alloy coating,
The content of phosphorus in the palladium or palladium alloy coating is 3 wt% or less,
In the conductive powder, the proportion of the primary particles in the conductive particles is 85% by weight or more based on the weight of the conductive powder. The conductive powder according to claim 1, wherein the palladium or palladium alloy coating has a thickness of 5 to 500 nm. The conductive powder according to claim 1, wherein the nickel or nickel alloy coating has a thickness of 10 to 300 nm. A conductive material comprising the conductive powder according to any one of claims 1 to 3 and an insulating resin.