KR101305574B1 - Conductive powder plated by electroless plating and process for producing the same - Google Patents

Abstract

It is an object of the present invention to provide a conductive electroless plating powder having excellent plating adhesion and an industrially advantageous method for producing the same, even without using chromic acid, permanganic acid, or the like, which are environmental pollutants. . The electroconductive electroless plating powder of the present invention is characterized in that the surface of the core material powder is coated with melamine resin, and a metal film is further formed by electroless plating. Contacting the condensate to carry out the polymerization reaction of the initial condensate to obtain a core material powder coated with melamine resin, followed by supporting the precious metal on the surface of the core material powder coated with melamine resin, followed by supporting the precious metal It characterized by including the process of electroless-plating the made core material powder.

Conductive electroless plating powder, core material powder, melamine resin, precious metal

Description

Conductive electroless plating powder and manufacturing method therefor {CONDUCTIVE POWDER PLATED BY ELECTROLESS PLATING AND PROCESS FOR PRODUCING THE SAME}

The present invention relates to a conductive electroless plating powder and a manufacturing method thereof.

Conventionally, when producing an electroless plated product including conductive electroless plating powder, when the plated object is hydrophobic, it has been necessary to hydrophilize its surface to improve the adhesion between the metal film and the plated object. As a means of improving the adhesiveness, a powerful oxidizing agent such as chromic acid and permanganic acid has been conventionally used.

However, these oxidants have a problem of high environmental load. When appropriate reduction and washing are performed, chromium and manganese are rarely left in the plated product, but complete removal is very difficult.

Therefore, as a hydrophilic treatment method with less environmental load, for example, Patent Document 1 below discloses an aminosilane-based compound, a glycol compound, a nitrile compound, a titanate compound, a butadiene polymer, an unsaturated fatty acid such as linoleic acid, linolenic acid, or the like in a synthetic resin material. A method of coating the synthetic resin material with a noble metal trapping surface treatment material selected from the above to carry noble metal ions and then electroless plating treatment has been proposed.

However, in the method described in Patent Document 1, it is difficult to obtain particularly excellent plating adhesion to fine particles having an average particle diameter of 20 µm or less, and for example, it is difficult to use for the use of fine pitch connection.

Patent Document 1: Japanese Patent Application Laid-Open No. 61-64882

[PROBLEMS TO BE SOLVED BY THE INVENTION]

Accordingly, an object of the present invention is to provide a conductive electroless plating powder having excellent plating adhesion and an industrially advantageous manufacturing method thereof without using chromic acid, permanganic acid, or the like, which are environmental pollutants, and in particular even fine particles having an average particle diameter of 20 µm or less. Is in.

Means for Solving the Invention

The present invention achieves the above object by providing a conductive electroless plating powder, wherein the surface of the core material powder is coated with a melamine resin and a metal film is formed by electroless plating.

BEST MODE FOR CARRYING OUT THE INVENTION [

Hereinafter, the present invention will be described based on its preferred embodiments. In the electroconductive electroless plating powder (hereinafter, also simply referred to as plating powder) of the present invention, the surface of the core material powder is coated with melamine resin, and a metal film is formed by electroless plating.

There is no restriction | limiting in particular in the kind of core material powder used by this invention, Both organic powder and inorganic powder are used. The core material powder may be hydrophobic or hydrophilic on its surface. Naturally, the method of this embodiment is especially effective for the core material powder whose surface is hydrophobic. The core material powder is preferably substantially insoluble in water, and more preferably, does not dissolve or deteriorate in acid or alkali.

There is no restriction | limiting in particular in the shape of core material powder. Generally, the core material powder may be in the form of powder, but may be in other shapes, for example, fibrous, hollow, plate or needle, or may have a large number of protrusions on the surface of the particle, or may be irregular. In the present invention, spherical ones of them are particularly preferable in terms of excellent filling properties when used as a conductive filler.

Specific examples of the core material powder include metals (including alloys), oxides of metals, glass, ceramics, silica, carbon, metals or nonmetals (including functions), aluminosilicates, metal silicates, metal carbides, and metals as inorganic materials. Nitrides, metal carbonates, metal sulfates, metal phosphates, metal sulfides, metal salts, metal halides and carbon. As organic substances, thermoplastic resins such as natural fiber, natural resin, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylic acid ester, polyacrylonitrile, polyacetal, ionomer, polyester, alkyd resin, phenol resin , Urea resin, benzoguanamine resin, melamine resin, xylene resin, silicone resin, epoxy resin or diallyl phthalate resin and the like. These may be used independently and may be used as a mixture of 2 or more types.

As other preferable physical properties of the core material powder to be used in the present invention, those having an average particle diameter of 0.5 to 100 µm, especially 0.8 to 80 µm, and more preferably 1 to 20 µm, suppress aggregation of the plating process and conduct conductive particles after electroless plating. It is preferable from the viewpoint of coping with narrow pitch. In addition, the average particle diameter of a core material powder shows the value measured using the electrical resistance method.

In addition, the particle size distribution of the core material powder measured by the method mentioned above has a width | variety. In general, the width of the particle size distribution of the powder can be obtained by the variation coefficient represented by the following equation (1).

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

The larger the coefficient of variation indicates that the distribution has a width, while the smaller the coefficient of variation indicates that the particle size distribution is sharp. In this embodiment, it is preferable that this variation coefficient is 50% or less, especially 30% or less, and also 20% or less as core material powder. This is because, when the plating powder obtained by the present invention is used as the conductive particles in the anisotropic conductive film, there is an advantage that the contribution ratio effective for the connection is increased.

Although the coating amount of melamine resin changes with kinds, shapes, etc. of the core material powder to be used, it is preferable to set it as 0.1-15 weight% in most cases, Preferably it is 0.5-10 weight%. The reason for this is that when the coating amount of the melamine resin is less than 0.1% by weight, the coating amount is insufficient and the plating powder excellent in the plating adhesion tends not to be obtained. This is because fine granular melamine resin is generated singly in the step of obtaining the core material powder and remains as foreign matter. In addition, the melamine resin may be modified.

Although the metal film in electroconductive electroless plating powder is a single layer structure of a single metal normally, it may be a multilayered structure by 2 or more types of dissimilar metals according to the objective. In addition, the metal film may be either crystalline or amorphous depending on the kind or plating conditions. In addition, the metal film may be magnetic or nonmagnetic. The metal here includes alloys (for example, nickel-phosphorus alloys and nickel-boron alloys) in addition to the metal alone. Examples of the metal that can be used include Ni, Fe, Cu, Co, Pd, Ag, Au, Pt, Sn and the like. It is preferable that the thickness of a metal film is 0.001-2 micrometers, especially 0.005-1 micrometer. The thickness of the metal film can be calculated from the amount of nickel ions added and chemical analysis.

Ni is preferable from an economic point of view. In the following embodiment, although nickel is mentioned as a metal and demonstrated, the metal which can be used is not limited to this.

In the manufacturing method of this embodiment, the core material powder and the initial condensate of melamine resin are brought into contact with each other, and the polymerization reaction of the initial condensate is carried out to obtain a core material powder coated with melamine resin, followed by the core coated with melamine resin. The step of supporting a precious metal on the surface of the ash powder, followed by the step of electroless plating the core material powder on which the precious metal is supported, but in particular (1) the step of obtaining a core material powder coated with melamine resin, (2 By including the catalyzing treatment step, the initial thin film forming step and the electroless plating step, plating powder of stable quality can be industrially advantageously obtained.

The melamine resin coating step of the core material powder of (1) is a step of bringing the core material powder and the initial condensate of the melamine resin into contact with each other to carry out the polymerization reaction of the initial condensate to obtain the core material powder coated with the melamine resin.

In addition, in this invention, the initial condensate of a melamine resin means that a condensation reaction occurs by heating or addition of an acid catalyst, and a melamine resin is produced | generated. The initial condensate of the melamine resin may be commercially available, or may be used as the initial condensate of the melamine resin obtained by reacting the melamine compound and the aldehyde compound.

As said melamine compound, for example, the melamine compound which substituted the hydrogen of the melamine and the amino group of melamine by the alkyl group, the alkenyl group, and the phenyl group (for example, refer Unexamined-Japanese-Patent No. 09-143238), and the amino group of melamine Substituted melamine compounds in which hydrogen is substituted with a hydroxyalkyl group or an aminoalkyl group (see, for example, Japanese Patent Application Laid-Open No. Hei 5-202157) and the like, but are industrially easily available and inexpensive. Melamine is preferred. In addition, some of the melamine compounds may be added to urea, thiourea, urea such as ethylene urea, guanamines such as benzoguanamine and acetoguanamine, phenols such as phenol, cresol, alkylphenol, resorcinol, hydroquinone and pyrogallol, It may be substituted with aniline.

Examples of the aldehyde compound include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, furfural and the like, and formaldehyde and paraformaldehyde are preferable in view of reactivity with the melamine compound. The addition amount of the aldehyde compound is preferably 1.1 to 6.0 times mole, preferably 1.2 to 4.0 times mole in molar ratio relative to the melamine compound.

Although water is especially preferable as a solvent which can be used, it can also be used as a mixed solvent of water and an organic solvent. In this case, as the organic solvent which can be used, it is preferable to use a solvent which can dissolve the initial condensate of melamine resin, for example, alcohols such as methanol, ethanol, propanol, dioxane, tetrahydrofuran, 1,2 And polar solvents such as ethers such as -dimethoxyethane, dimethylformamide, and dimethyl sulfoxide.

The reaction of the melamine compound and the aldehyde compound is carried out at pH 8-9, and the reaction can be carried out by adding a base as necessary. As a base which can be used, common alkali agents, such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonia water, can be used, for example. The initial condensate of a melamine resin having a molecular weight of usually about 200 to 700 at a reaction temperature of 25 to 100 ° C can be obtained.

In addition, the initial condensate of the melamine resin modified by alcohol can be obtained by reacting the initial condensate of the melamine resin with alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol in the presence of a trace amount of an acidic substance. .

Although the addition amount of the initial condensate of the said melamine resin changes with kinds of core material powder to be used, it is preferable to set it as 0.1-15 weight% in most cases, Preferably it is 0.5-10 weight%.

In this invention, the reaction operation in the process of obtaining the core material powder which coat | covered this melamine resin of this (1) produces the solvent containing the said core material powder, The initial condensate of the said melamine resin is made to the said solvent. A method of adding and performing the polymerization reaction of the initial condensate, a method of adding the core material powder to a solvent containing the initial condensate of the melamine resin, and performing a polymerization reaction of the initial condensate, or a core material powder, the melamine compound and A predetermined amount of an aldehyde compound is added, and if necessary, an alkali agent can be added to perform a polymerization reaction of the initial condensate of melamine resin as it is in a solvent. In addition, a polymerization reaction adds an acid catalyst as needed and reacts at 40-100 degreeC under heating, and after completion | finish of reaction, it solid-separates by the conventional method, and then performs drying at 60-180 degreeC, or keeps the reaction liquid as it is. By spray-drying, the core material powder coated with melamine resin can be obtained.

Although it does not restrict | limit especially as an acid catalyst which can be used for the said polymerization reaction, For example, sulfonic acids, such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, methanesulfonic acid, benzenesulfonic acid, paratoluenesulfonic acid, alkylbenzenesulfonic acid, sulfamic acid, formic acid, oxalic acid And organic acids such as benzoic acid and phthalic acid can be used.

In the catalysis treatment step (2), after the noble metal ions are trapped in the core material powder having the capturing ability of the noble metal ions or imparting the capturing ability of the noble metal ions by surface treatment, the catalyst is reduced to reduce the noble metal ions to the core material powder. It is a process to be supported on the surface of the. In the initial thin film forming step (3), the core material powder carrying the noble metal is dispersed and mixed in the initial thin film forming liquid containing nickel ions, the reducing agent and the complexing agent, and the nickel ions are reduced to form nickel on the surface of the core material powder. Is the process of forming an initial thin film. The electroless plating process of (4) is a process of manufacturing the plating powder which has a nickel film on the surface of core material powder by electroless plating. Hereinafter, each process is demonstrated.

(2) catalysis treatment process

The core material powder coated with the melamine resin obtained in the step (1) is surface-modified so that its surface has the ability to trap precious metal ions or has the capacity to capture precious metal ions. The noble metal ions are preferably palladium or silver ions. The fact that a noble metal ion has a trapping capability means that the noble metal ion can be trapped as a chelate or a salt.

Subsequently, the core material powder is dispersed in an acidic aqueous solution in which noble metal salts such as palladium chloride and silver nitrate are lean. As a result, noble metal ions are trapped on the powder surface. The noble metal salt concentration is sufficient in the range of 1 × 10 ⁻⁷ to 1 × 10 ⁻² mol per m 2 of surface area of the powder. The core material powder in which the precious metal ions are captured is separated from the system and washed with water. Subsequently, the core material powder is suspended in water, and a reducing agent is added thereto to reduce the precious metal ions. As a result, the precious metal is supported on the surface of the core material powder. As the reducing agent, for example, sodium hypophosphite, sodium borohydride, potassium borohydride, dimethylamine borane, hydrazine, formalin and the like are used.

Before capturing the precious metal ions on the surface of the core material powder, a susceptibility treatment may be performed in which tin ions are adsorbed on the surface of the powder. In order to adsorb tin ions to the surface of the powder, for example, the surface-modified core material powder may be added to an aqueous solution of the first tin chloride and stirred for a predetermined time.

(3) initial thin film formation process

The initial thin film forming step is mainly performed for the purpose of smoothing out uniform deposition of nickel into the core material powder. In the initial thin film formation step, first, the core material powder on which the precious metal is supported is sufficiently dispersed in water. For dispersion, a shear dispersion device such as a colloid mill or a homogenizer can be used. When disperse | distributing core material powder, dispersing agents, such as surfactant, can be used as needed, for example. The aqueous suspension thus obtained is dispersed and mixed in an initial thin film forming liquid containing nickel ions, a reducing agent and a complexing agent. As a result, a reduction reaction of nickel ions is initiated, and an initial thin film of nickel is formed on the surface of the core material powder. As mentioned above, since the initial thin film formation process is mainly performed for the purpose of uniform precipitation, it is preferable that the initial thin film of nickel formed is thin enough to smooth the surface of the core material powder. In this respect, the thickness of the initial thin film is preferably 0.001 to 2 mu m, in particular 0.005 to 1 mu m. The thickness of the initial thin film can be calculated from the amount of nickel ions added or chemical analysis.

From the viewpoint of forming the initial thin film of the above-mentioned thickness, the concentration of nickel ions in the initial thin film forming liquid is preferably 2.0 x 10 ^-4 to 1.0 mol / l, particularly 1.0 x 10 ^-3 to 0.1 mol / l. . As the nickel ion source, a water-soluble nickel salt such as nickel sulfate or nickel chloride is used. From the same point of view, the concentration of the reducing agent in the initial thin film forming liquid is preferably 4 × 10 ⁻⁴ to 2.0 mol / L, particularly 2.0 × 10 ⁻³ to 0.2 mol / L. As a reducing agent, the same thing as what is used for reduction of the noble metal ion mentioned above can be used.

It is preferable to contain a complexing agent in the initial thin film formation liquid. A complexing agent is a compound which has a complex formation effect with respect to the metal ion used for plating. In this embodiment, an organic carboxylic acid or its salt, for example, citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid or gluconic acid or its alkali metal salt or ammonium salt can be used as a complexing agent. Moreover, the compound which has amino groups, such as an amine compound, for example, glycine, alanine, ethylenediamine, diethylenetriamine, triethylenetetramine, pentaethylene hexamine, can also be used. These complexing agents can be used 1 type or 2 or more types. In view of the solubility of the complexing agent, the amount of the complexing agent in the initial thin film forming liquid is preferably 0.003 to 10 mol / L, in particular 0.006 to 4 mol / L.

Since the initial thin film can be easily formed, the concentration of the core material powder in the aqueous suspension is preferably 0.1 to 500 g / l, particularly 0.5 to 300 g / l.

The aqueous suspension obtained by mixing the aqueous suspension containing the core material powder and the initial thin film forming liquid is then used in the electroless plating step described later. In the aqueous suspension before being used in the electroless plating process, the ratio of the total sum of the surface areas of the core material powder contained in the aqueous suspension to the volume of the aqueous suspension (this ratio is generally referred to as loading) It is preferable that it is 0.1-15 m <2> / L, Especially 1-10 m <2> / L in the point which can easily form the nickel film which has a film excellent in adhesiveness. If the load is too high, the reduction of nickel ions in the liquid phase is severe in the electroless plating step described later, and a large amount of nickel fine particles are generated in the liquid phase, which adheres to the surface of the core material powder to form a uniform nickel film. It becomes difficult to do it.

(3) electroless plating process

In the electroless plating step, three liquids (a) the core material powder in which the initial thin film was formed, and an aqueous suspension containing the complexing agent, (b) nickel ion-containing liquid and (c) reducing agent-containing liquid are used. The aqueous suspension of (a) can use what was obtained at the initial thin film formation process mentioned above as it is.

Apart from the aqueous suspension of (a), two liquids of the nickel ion containing liquid of (b) and the reducing agent containing liquid of (c) are prepared. The nickel ion-containing liquid is an aqueous solution of a water-soluble nickel salt such as nickel sulfate or nickel chloride which is a nickel ion source. The concentration of nickel ions is preferably 0.1 to 1.2 mol / l, particularly 0.5 to 1.0 mol / l, because the nickel film having excellent adhesion can be easily formed.

It is preferable to contain the complexing agent of the same kind as the complexing agent contained in the aqueous suspension in a nickel ion containing liquid. That is, it is preferable to contain the same kind of complexing agent in both the aqueous suspension of (a) and the nickel ion containing liquid of (b). Thereby, the nickel film excellent in adhesiveness can be formed easily. Although the reason is not clear, the inclusion of a complexing agent in both the aqueous suspension of (a) and the nickel ion-containing liquid of (b) impedes that the nickel ions are stabilized and that the reduction reaction proceeds rapidly. I guess.

The concentration of the complexing agent in the nickel ion-containing liquid of (b) also affects the formation of the nickel film similarly to the concentration of the complexing agent in the aqueous suspension of (a). In view of this and the solubility of the complexing agent, the amount of the complexing agent in the nickel ion-containing liquid is preferably 0.006 to 12 mol / l, particularly 0.012 to 8 mol / l.

The reducing agent-containing liquid of (c) is generally an aqueous solution of a reducing agent. As a reducing agent, the same thing as what is used for reduction of the noble metal ion mentioned above can be used. In particular, it is preferable to use sodium hypophosphite. Since the concentration of the reducing agent affects the reduced state of the nickel ions, it is preferable to adjust the concentration to 0.1 to 20 mol / l, in particular to 1 to 10 mol / l.

To the aqueous suspension of (a), two liquids, a nickel ion-containing liquid of (b) and a reducing agent-containing liquid of (c), are added separately and simultaneously. As a result, nickel ions are reduced, and nickel is deposited on the surface of the core material powder to form a film thereof. The addition rate of the nickel ion-containing liquid and the reducing agent-containing liquid is effective to control the deposition rate of nickel. The deposition rate of nickel affects the formation of a nickel film having good adhesion. Therefore, it is preferable to control the precipitation rate of nickel to 1-10000 nm / hour, especially 5-300 nm / hour by adjusting the addition rate of 2 liquids. The precipitation rate of nickel can be obtained by calculating from the addition rate of nickel ion containing liquid.

While adding 2 liquids to the aqueous suspension, it is preferable to keep the load in the range of 0.1 to 15 m 2 / l, in particular 1 to 10 m 2 / l. As a result, nickel is uniformly deposited. For the same reason, it is also preferable that the loading amount at the time when addition of the two liquids is completed and reduction of nickel ions is completed is in this range.

Although it depends also on the kind of reducing agent used, during the reduction reaction of nickel ions, the pH of the aqueous suspension is maintained in the range of 3 to 13, especially 4 to 11, to prevent the formation of water-insoluble precipitates of nickel. It is preferable at the point. In order to adjust pH, pH regulators, such as sodium hydroxide, can be added a predetermined amount in a reducing agent containing liquid, for example.

The obtained plating powder is separated after filtration and washing with water are repeated several times. Moreover, as an addition process, the formation process of the gold plating layer as an uppermost layer on a nickel film can also be performed. The gold plating layer can be formed by a conventionally known electroless plating method. For example, a gold plating layer is formed on a nickel film by adding an electroless plating solution containing sodium ethylenediamine tetra tetraacetate, trisodium citrate, and potassium cyanide to the aqueous suspension of the plating powder, and adjusted to pH with sodium hydroxide. do. The thickness of the gold plating layer is generally about 0.001 to 0.5 µm. The thickness of the gold plating layer can be calculated from the amount of gold ions added and chemical analysis.

In this way, the plating powder in which the nickel film is formed on the surface of the core material powder is obtained. The nickel film in this plating powder becomes excellent in adhesiveness with the core material powder. The thickness of the nickel film greatly affects its adhesiveness and heat resistance, and when the film is too thick, peeling from the core material powder tends to occur and the conductivity tends to be lowered. On the contrary, even if a film is too thin, desired electroconductivity will not be obtained. From these viewpoints, it is preferable that the thickness of a nickel film is about 0.005-10 micrometers, especially about 0.01-2 micrometers. The thickness of the nickel film can be measured not only from observation with a scanning electron microscope, but also from the amount of nickel ions added and chemical analysis.

The plating powder of this invention obtained in this way is an anisotropically conductive film (ACF), a heat-sealing connector (HSC), a conductive material for connecting the electrode of a liquid crystal display panel to the circuit board of a LSI chip for driving, etc., for example. It is preferably used for the use.

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 this embodiment.

[Examples 1 to 3]

(1) melamine resin coating process

100 parts by weight of the core material powder, 100 parts by weight of water, 3 parts by weight of melamine, and 8 parts by weight of 37% formalin were injected into a four-necked flask equipped with a cooler, and a 5% aqueous sodium carbonate solution was added thereto under stirring to prepare a pH of 9.0. . The temperature was then raised to 75 ° C., and the reaction was carried out under stirring for 2 hours. After completion of the reaction, the core material powder coated with the melamine resin was obtained by cooling, filtration and washing with water and drying and curing at 150 ° C for 6 hours under reduced pressure (5 mmHg or less).

(2) catalysis treatment process

200 ml of 1st tin chloride aqueous solution was thrown into 200 ml of aqueous slurry containing 7.5 weight% of the melamine coating core material powder obtained by the process of (1). 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 susceptibility treatment in which tin ions were adsorbed onto the surface of the melamine-coated core material powder. The aqueous solution was then filtered, repulsed once and washed with water. Subsequently, 400 ml of an aqueous slurry containing 3.75 wt% of melamine-coated core material powder was prepared and maintained at 60 ° C. 2 ml of 0.11 mol g / l palladium chloride aqueous solution was added, stirring ultrasonic slurry together. The stirring state was maintained for 5 minutes as it was, and the activation process which captures palladium ion on the surface of the melamine coating core material powder was performed. Subsequently, the aqueous solution was filtered and repulsed and washed once. Subsequently, 200 ml of an aqueous slurry containing 7.5 wt% of melamine-coated core material powder was prepared. The slurry was stirred while using ultrasonic waves, and 20 ml of a mixed aqueous solution of 0.017 mol / l dimethylamine borane and 0.16 mol / l boric acid was added thereto. It stirred for 2 minutes, using ultrasonic wave together at normal temperature, and the reduction process of palladium ion was performed.

(3) initial thin film formation process

200 ml of an aqueous slurry containing 7.5% by weight of the melamine-coated core material powder treated in the step (2) contains 0.087 mol / l sodium tartrate, 0.005 mol / l nickel sulfate and 0.012 mol / l sodium hypophosphite It stirred and added to the initial thin film formation liquid to make an aqueous suspension. The initial thin film formation liquid was warmed to 75 ° C., and the liquid amount was 2 L. Immediately after the slurry injection, hydrogen evolution was observed, confirming the onset of initial thin film formation.

(4) electroless plating process

The aqueous suspension obtained in the initial thin film formation process contained a nickel ion solution containing 0.86 mol / L nickel sulfate and 0.17 mol / L sodium tartrate, and 2.57 mol / L sodium hypophosphite and 2.6 mol / L sodium hydroxide. Two liquids of the reducing agent containing liquid contained were added at the addition rate of 8 ml / min, respectively. The amount of addition was adjusted so that the amount of the added solution was 0.2 µm, respectively. The generation of hydrogen was observed immediately after addition of the two liquids, and the start of the plating reaction was confirmed. After the addition of the two liquids was completed, stirring was continued while maintaining a temperature of 75 ° C. until the foaming of hydrogen stopped. The aqueous suspension was then filtered and the filtrate was repulsed three times and then dried in a 110 ° C. vacuum dryer. This obtained the plating powder which has a nickel-phosphorus alloy plating film.

[Comparative Examples 1 to 3]

In Examples 1-3, plating powder was obtained by the same operation except not having performed the process of (1).

[Comparative Examples 4 to 6]

In Example 1, plating powder was obtained by operation similar to Examples 1-3, except having changed the process of (1) to the following (1-1) process.

(1-1) process

To 100 parts by weight of an aqueous solution containing 1.0% by weight of the surface treating agent shown in Table 1, 10 parts by weight of the same styrene resin used in Example 1 was added and immersed at room temperature for 1 hour. Subsequently, the core material powder which dried at 110 degreeC and coated the surface treating agent was produced.

[Comparative Example 7]

In Example 1, plating powder was obtained by operation similar to Example 1 except having changed the process of (1) to the following (1-2) process.

(1-2) process

100 weight part of core materials powder was thrown in 2 L of etching liquid containing 2.0 mol / L of chromic anhydrides, and 3.6 mol / L of sulfuric acid, and it heated up at 70 degreeC, and stirred for 10 minutes. Subsequently, filtration and washing were repeated to obtain a core material powder subjected to an etching treatment.

About the obtained plating powder, the thickness of the plating film and the adhesiveness of the plating film were measured and evaluated by the following method. The results are shown in Table 2. In addition, the amount of chromium remaining in the plating powder was measured, and the results were also listed in Table 2.

[Thickness of plating film]

The plating powder was immersed in nitric acid to dissolve the plating film, and the coating component was quantified by ICP or chemical analysis to calculate the thickness by the following equations (2) and (3).

A = [(r + t) ³ -r ³ ] d ₁ / rd ₂

A = W / 100-W

Where r is the radius of the core material powder (μm), t is the thickness of the plated film (μm), d ₁ is the specific gravity of the plated film, d ₂ is the specific gravity of the core material powder, and W is the metal content (weight%). Indicates.

[Adhesion of Plating Film]

2.2 g of plating powder and 90 g of zirconia beads having a diameter of 3 mm were placed in a 100 ml mayonnaise bottle. In addition, 10 ml of toluene was added to a mayonnaise bottle using a hole pipette. The inside of mayonnaise bottle was stirred at 400 rpm for 10 minutes using the stirrer (three-one motor). After the completion, the plated powder and the zirconia beads were separated. Plating powder was observed with the scanning electron microscope, and the peeling degree of a plating film was evaluated on the following references | standards.

(Circle): Peeling of the plating film was not observed.

X: Peeling of the plating film was observed.

[Chrome content]

The plating powder was immersed in nitric acid to dissolve the plating film, and thermal decomposition was performed by adding sulfuric acid. The amount of chromium was measured by ICP from the obtained decomposition solution.

Note) surface treatment agent 1; γ-aminopropyltriethoxysilane, surface treatment agent 2; N-β (aminoethyl) γ-aminopropyltrimethoxysilane, surface treatment agent 3; γ-methacryloxypropyltrimethoxysilane

Note) N.D. indicates that the detection limit is 0.002 mg / g-plated powder or less.

As is apparent from the results shown in Table 2, it was found that the plating powder (inventive product) of each example was excellent in the adhesion of the plating film and substantially did not contain chromium. On the other hand, although the plating powder of Comparative Examples 1-6 does not contain chromium, it turned out that plating is easy to peel. Moreover, although the plating powder of the comparative example 7 was excellent in the adhesiveness of a plating film, it turned out that chromium is contained in plating powder.

According to the present invention, even without using chromic acid, permanganic acid or the like for the hydrophilization treatment, it is possible to obtain an electroless electroless plating powder having excellent plating adhesion even for fine particles having an average particle diameter of 20 µm or less, and the electroless electroless plating of the present invention. The powder is preferably used, for example, for anisotropic conductive films (ACFs), heat-sealed connectors (HSCs), and conductive materials for connecting electrodes of liquid crystal display panels to circuit boards of LSI chips for driving, for use in polarizing plates, and the like.

Claims (6)

The surface of the core material powder is coated with a melamine resin by a method of contacting the core material powder having an average particle diameter of 1 to 20 µm with the initial condensate of melamine resin in a solvent to carry out the polymerization reaction of the initial condensate in a solvent. A conductive electroless plating powder, wherein a metal film is formed on the surface of the coated core material powder by electroless plating. The conductive electroless plating powder according to claim 1, wherein the core material powder is hydrophobic. The conductive electroless plating powder according to claim 1 or 2, wherein the initial condensate of the melamine resin is produced by reacting a melamine compound with an aldehyde compound at a pH of 8 to 9. The conductive electroless plating powder according to claim 3, wherein the initial condensate of the melamine resin is produced by reacting a melamine compound, an aldehyde compound, and a base at a pH of 8 to 9. Electroconductive plating metal powder of Claim 1 or 2 which uses a spherical thing as said core material powder. The core material powder having an average particle diameter of 1 to 20 µm and the initial condensate of melamine resin are brought into contact with each other in a solvent, and the polymerization reaction of the initial condensate is carried out in a solvent to obtain a core material powder coated with melamine resin, followed by the melamine resin. And a step of supporting a noble metal on the surface of the core material powder coated thereon, followed by electroless plating the core material powder on which the noble metal is supported.