KR20050078699A - Electrolessly-plated conductive powder and manufacturing method thereof - Google Patents

Abstract

The present invention provides a conductive electroless plating powder having a plating film having improved heat resistance and a method of manufacturing the same. The conductive electroless plating powder of the present invention is a conductive electroless plating powder in which a nickel film is formed by electroless plating on a core particle surface, wherein grain boundaries in the nickel film are mainly oriented in the thickness direction of the nickel film. It is characterized by. An electroless plating layer of gold may be formed on the outermost surface. The nickel film is formed by an electroless plating method using glycine or ethylenediamine as a complexing agent.

Description

Electrolessly-plated conductive powder and manufacturing method

The present invention relates to a conductive electroless plating powder and a method for producing the same, and more particularly, to a conductive electroless plating powder having a nickel film with improved heat resistance and a method for producing the same.

The present applicant proposed a method of electroless plating on the core powder of a synthetic resin, and after the precious metal ion was supported on the core powder of a synthetic resin by using a noble metal trapping surface treatment agent, it was introduced into a plating solution and subjected to electroless plating. (See Japanese Patent Laid-Open No. 61-64882). This method is called a so-called dry bath method, and the plating liquid contains a metal salt, a reducing agent, a complexing agent, a buffer, a stabilizer and the like. According to this method, there exists an advantage that the adhesiveness of a plating film and core material powder is improved. In order to further improve the adhesion, the present applicant has also proposed a method of further improving the electroless plating method (see Japanese Patent Laid-Open No. Hei 1-242782).

However, various performances required for electroless plating powder are becoming more stringent, and in recent years, stability at high temperature is required in addition to adhesion.

Accordingly, an object of the present invention is to provide a conductive electroless plating powder having a plated film having improved heat resistance and a method of manufacturing the same.

As a result of earnestly examining the inventors, the present inventors have formed a coating film having a structure different from that of the plating film described in JP-A-61-64882, that is, a structure in which fine metal particles exhibit a dense and substantially continuous film. I found out that this is achieved.

In the electroconductive electroless plating powder in which the nickel film was formed by electroless plating on the surface of the core particle, the grain boundary in the nickel film is mainly oriented in the thickness direction of the nickel film. The above object is achieved by providing an electroless plating powder.

Moreover, this invention is a preferable manufacturing method of the said electroless electroless plating powder, Comprising: The noble metal ion was trapped in the said core material powder which has the ability to trap a noble metal ion, or imparted the ability to capture a noble metal ion by surface treatment. Thereafter, this was reduced to carry the precious metal on the surface of the core powder,

Subsequently, the core powder is dispersed and mixed in an initial thin film forming solution containing a complexing agent of nickel ions, a reducing agent and an amine compound, and nickel ions are reduced to form an initial thin film of nickel on the surface of the core powder.

Subsequently, two solutions of the nickel ion-containing liquid and the reducing agent-containing liquid containing the complexing agent and the same kind of complexing agent were separately added simultaneously to the core powder and the aqueous suspension containing the complexing agent on which the initial thin film was formed. The above object is achieved by providing a method for producing a conductive electroless plating powder, which causes an electroless plating reaction.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated, referring drawings based on the preferable embodiment. In the electroconductive electroless plating powder (hereinafter, also simply referred to as plating powder) of the present invention, a nickel film is formed on the surface of the core material powder by an electroless plating method.

In the nickel film formed on the surface of the core material powder, grain boundaries in the nickel film are mainly oriented in the thickness direction of the nickel film. That is, the crystal | crystallization in a nickel film has a columnar structure mainly extended in the thickness direction of the said film. Whether or not the grain boundary of the nickel film is oriented in the thickness direction can be visually observed by a scanning electron microscope (hereinafter also referred to as SEM). Specifically, when the thickness direction cross section of the nickel film is observed by SEM at an magnification of up to 100000 times, when the columnar structure extending in the thickness direction of the film is observed, the grain boundaries are mainly oriented in the thickness direction. can do.

1 shows an SEM photograph showing an example of the plating powder of the present invention. The magnification is 50000 times. As can be seen from Fig. 1, the nickel film in the plating powder is composed of a plurality of columnar structures extending in the thickness direction of the nickel film. In Fig. 1, the height of each columnar structure is larger than its width. Depending on the method of forming the nickel film, the height and width of the columnar structure may be almost the same or may be larger than the height. It may also be a truncated spindle shape or an inverted shape. On the other hand, in the SEM photograph (magnification: 50000x) of the electroless nickel-plated powder shown in FIG. 2 which is a conventional product, a hump-shaped grain boundary is observed in the thickness direction cross section of a nickel film.

As can be seen from FIG. 1, in the plating powder of the present invention, the nickel film has a plurality of columnar structures extending in the thickness direction without a gap, forming a dense and homogeneous continuous film. On the other hand, the nickel film of the plating powder shown in FIG. 2 which is a conventional product is grainy and heterogeneous. As can be seen from the examples described later, it has been found by the present inventors that the nickel film having the columnar structure shown in FIG. 1 has high heat resistance and thus the conductivity of the plating powder is less likely to decrease even under high temperature conditions.

An example of the procedure of SEM observation of the cross section of the nickel film in plating powder is as follows. 50 parts by weight of plated powder, 100 parts by weight of Epicoat 815 (manufactured by Japan Epoxy Resin Co., Ltd.), 5 parts by weight of Epicure (manufactured by Japan Epoxy Resin Co., Ltd.), and kneaded in a 110 ° C. dryer for 10 minutes A 10 mm x 2 mm sample is molded. After the obtained sample was bent and broken, the site | part in which the fracture surface of the plating film is shown is observed by SEM.

As a result of performing X-ray diffraction measurement, the present inventors found that the nickel film of the plated powder of the present invention has some amorphous portions in addition to the crystalline portion, and a state in which crystalline and amorphous mixtures are common. In particular, the crystal form of the nickel film is not critical in the present invention, and if it has a columnar structure, the desired heat resistance is expressed regardless of whether the nickel film is crystalline or amorphous.

The thickness of the nickel film affects not only the adhesion and the heat resistance, but when the film is too thick, peeling from the core powder tends to occur and the conductivity tends to be lowered. On the contrary, if the film is too thin, the desired conductivity cannot be obtained. From this viewpoint, the thickness of the nickel film is preferably 0.005 to 10 µm, particularly about 0.01 to 2 µm. The thickness of the nickel film can be measured by SEM observation, or can be calculated by addition amount or chemical analysis of nickel ions.

Moreover, depending on the kind of reducing agent used when forming a nickel film by electroless plating, a nickel film may be an alloy of nickel and another element. For example, when sodium hypophosphite is used as the reducing agent, the obtained nickel film is made of a nickel-phosphorus alloy. However, in the present invention, such a nickel alloy film is also called a broad nickel film.

In the plating powder of the present invention, the above-described nickel film is formed on the surface of the core material powder. From the viewpoint of further improving the conductivity of the plating powder, a thin gold plating layer may be formed on the outermost surface. The gold plating layer is formed by electroless plating similarly to the nickel film. The thickness of a gold plating layer is generally about 0.001-0.5 micrometer. The thickness of the gold plating layer can be calculated by the amount of gold ions added or by chemical analysis.

There is no restriction | limiting in particular in the kind of core material powder in which a nickel film is formed, Both organic powder and inorganic powder are used. In consideration of the electroless plating method described later, it is preferable that the core material powder can be dispersed in water. Therefore, the core powder is preferably substantially insoluble in water, and more preferably, does not dissolve or deteriorate in acid or alkali. Dispersible in water means that the suspension can be formed substantially dispersed in water so that the nickel film can be formed on the surface of the core powder by the usual dispersing means such as stirring.

There is no restriction | limiting in particular in the shape of core powder. In general, the core material powder may be in the form of powder, but may be other shapes, such as fibrous, hollow, plate, needle, or indefinite. The size of the core powder is selected according to the specific use of the plating powder of the present invention. For example, when using the plating powder of this invention as an electrically-conductive material for an electronic circuit connection, it is preferable that a core material powder is spherical particle about 0.5-1000 micrometers of average particle diameters.

The core powder is specifically, an inorganic material, including metals (including alloys), glass, ceramics, silica, carbon, metals or nonmetal oxides (including functions), metal silicates containing aluminosilicates, metal carbides, metal nitrides, Metal carbonates, metal sulfates, metal phosphates, metal sulfides, metal acid salts, metal halides, carbon and the like. Examples of the organic substance include thermoplastic resins such as natural fibers, natural resins, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylic acid ester, polyacrylonitrile, polyacetal, ionomer, and polyester, and alkyd resin. , Phenol resins, urea resins, benzoguanamine resins, melamine resins, xylene resins, silicone resins, epoxy resins or diallylphthalates. You may use these individually or in mixture of 2 or more types.

The core powder is preferably surface-modified such that its surface has the ability to trap precious metal ions or has the capacity to trap precious metal ions. It is preferable that a noble metal ion is palladium or silver ion. Having a capturing ability of a noble metal ion means that the noble metal ion can be trapped with a chelate or salt. For example, when an amino group, an imino group, an amide group, an imide group, a cyano group, a hydroxyl group, a nitrile group, a carboxyl group, or the like is present on the surface of the core powder, the surface of the core powder has the ability to trap precious metal ions. In the case of surface modification to have the capturing ability of the noble metal ion, for example, the method described in JP 61-64822 A can be used.

Next, the preferable manufacturing method of the plating powder of this invention is demonstrated. The manufacturing method of plating powder is divided roughly into (1) catalysis process process, (2) initial thin film formation process, and (3) electroless plating process. In the catalysis treatment step (1), after trapping a noble metal ion in a core powder having a capturing ability of a noble metal ion or giving a capturing ability of a noble metal ion by surface treatment, the noble metal is reduced to reduce the surface of the core powder. Soaked in In the initial thin film forming step of (2), the core powder containing the precious metal is dispersed and mixed in the initial thin film forming solution containing a complexing agent of nickel ions, a reducing agent and an amine compound, and the nickel ions are reduced to reduce the surface of the core powder. An initial thin film of nickel is formed on the film. In the electroless plating step of (3), the nickel ion-containing liquid containing the core powder in which the initial thin film of nickel was formed, and the aqueous suspension containing the said complexing agent, and the complexing agent which consists of the said amine compound of the said complexing agent, and Two liquids of the reducing agent-containing liquid are added simultaneously and electroless plating reaction is performed. Hereinafter, each process is explained in full detail.

(1) Catalytic Treatment

In the case where the core powder itself has a capturing ability of noble metal ions, a direct catalytic treatment is performed. If not, surface modification is required. In the surface modification treatment, the core powder is added to water or an organic solvent in which the surface treatment agent is dissolved, and then sufficiently stirred and dispersed, and the powder is separated and dried. The amount of the surface treating agent can be obtained by adjusting the amount of the surface treatment agent in the range of 0.3 to 100 mg per 1 m 2 of the surface area of the powder, depending on the kind of the core powder.

Next, the core powder is dispersed in a sparse acidic aqueous solution of a noble metal salt such as palladium chloride or silver nitrate. 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 mole per 1 m 2 of the surface area of the powder. The core 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. Accordingly, the precious metal is supported on the surface of the core powder. As the reducing agent, for example, sodium hypophosphite, sodium borohydride, potassium borohydride, dimethylamine borane, hydrazine, formalin and the like are used.

Before the noble metal ions are trapped on the surface of the core 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 on the surface of the powder, for example, the surface-modified core powder may be added to an aqueous solution of tin tin chloride and stirred for a predetermined time.

(2) Initial thin film formation process

The initial thin film forming step is performed for the purpose of uniform deposition of nickel in the core powder and the smoothing of the surface of the core powder. In the initial thin film forming step, first, the core material powder on which the noble metal is loaded is sufficiently dispersed in water. For dispersing, a shear dispersing device such as a colloid mill or homogenizer can be used. When disperse | distributing a 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 solution containing a complexing agent of nickel ions, a reducing agent and an amine compound. As a result, the reduction reaction of nickel ions is initiated, and an initial thin film of nickel is formed on the surface of the core powder. As described above, the initial thin film forming step is performed for the purpose of uniform precipitation and smoothing the surface of the core powder, so that the formed initial thin film of nickel may be thin enough to smooth the surface of the core powder. From this viewpoint, the thickness of the initial thin film is preferably 0.001 to 2 µm, particularly 0.005 to 1 µm. The thickness of the initial thin film can be calculated by the amount of nickel ions added and chemical analysis. In addition, the complexing agent is not consumed by reduction of nickel ions.

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 × 10 ⁻⁴ to 1.0 mol / liter, particularly 1.0 × 10 ⁻³ to 0.1 mol / liter. 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 / liter, particularly 2.0 × 10 ⁻³ to 0.2 mol / liter. 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 important to contain a complexing agent in the initial thin film forming liquid. By containing a complexing agent in this and the nickel ion containing liquid mentioned later, the nickel film which has columnar structure can be formed easily. A complexing agent is a compound which has a complexing effect with respect to the metal ion used for plating. In the present invention, a compound having an amino group such as an amine compound, for example, glycine, alanine, ethylenediamine, diethylenetriamine, triethylenetetramine, pentaethylenehexamine, is used as the complexing agent. These complexing agents can be used 1 type or 2 or more types. Of these complexing agents, in particular, glycine or ethylenediamine is preferably used because the nickel film having a columnar structure can be more easily formed. The concentration of the complexing agent affects the formation of the nickel film having a columnar structure. In view of this and 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 / liter, particularly 0.006 to 4 mol / liter.

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

The aqueous suspension obtained by mixing the aqueous suspension containing the core powder and the initial thin film forming liquid is then sent to the electroless plating process described later. In the aqueous suspension before being sent to the electroless plating process, the ratio of the total surface area of the core material powder contained in the aqueous suspension to the volume of the aqueous suspension (this ratio is generally called a load) is 0.1 to 15. It is preferable that it is m <2> / liter, especially 1-10 m <2> / liter in the point which the nickel film which has columnar structure can be formed easily. If the load is too high, the reduction of nickel ions in the liquid phase is severe in the electroless plating process described later, and a large amount of nickel fine particles are generated in the liquid phase, which adheres to the surface of the core powder, making it difficult to form a uniform nickel film. Become.

(3) electroless plating process

In the electroless plating process, three liquids of (a) the core powder in which the initial thin film was formed and the aqueous suspension containing the said complexing agent, (b) nickel ion containing liquid, and (c) reducing agent containing liquid are used. The aqueous suspension of (a) may be used as it is obtained in the initial thin film formation step described above.

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 / liter, particularly 0.5 to 1.0 mol / liter, in that the nickel film having a columnar structure can be easily formed.

It is important that the nickel ion-containing liquid contain a complexing agent of the same kind as the complexing agent contained in the aqueous suspension. That is, it is important to contain the same kind of complexing agent in both the aqueous suspension of (a) and the nickel ion-containing liquid of (b). By doing in this way, the nickel film which has columnar structure can be formed easily. Although the reason is not clear, the presence of the complexing agent in both the aqueous suspension of (a) and the nickel ion-containing liquid of (b) stabilizes the nickel ions and prevents the rapid progress of the reduction reaction. 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 / liter, particularly 0.012 to 8 mol / liter.

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 was 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 nickel ions, it is preferable to adjust the concentration to 0.1 to 20 mol / liter, particularly 1 to 10 mol / liter.

The aqueous suspension of (a) and the nickel ion-containing liquid of (b) may be added to the complexing agent of the amine compound described above, and another kind of complexing agent may be added. Examples of such complexing agents include organic carboxylic acids or salts thereof, such as citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid or gluconic acid, or alkali metal salts or ammonium salts thereof. When using another kind of complexing agent together, it is preferable to add the same kind to the aqueous suspension of (a) and the nickel ion containing liquid of (b) similarly to the complexing agent of an amine compound.

To the aqueous suspension of (a), two liquids of the nickel inon-containing liquid of (b) and the reducing agent-containing liquid of (c) are separately added simultaneously. In this way, nickel ions are reduced, and nickel is precipitated on the surface of the core material powder to form a film. 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 a columnar structure. Therefore, it is preferable to control the precipitation rate of nickel to 1-10000 nanometers / hour, especially 5 to 300 nanometers / hour by adjusting the addition rate of two liquids. The precipitation rate of nickel can be calculated by calculating from the addition rate of the nickel ion-containing liquid.

During the addition of the two liquids to the aqueous suspension, the concentration of the complexing agent in the aqueous suspension is not constant, and the increase in the amount of the aqueous suspension due to the addition of the two liquids and the concentration of the complexing agent contained in the nickel ion-containing liquid Changes due to addition. In the present production method, it is particularly advantageous to keep the concentration of the complexing agent in the aqueous suspension in the range of 0.003 to 10 mol / liter, especially 0.006 to 4 mol / litre, in consideration of the solubility of the complexing agent. It turns out that the inventor's review. By maintaining the concentration of the complexing agent in the aqueous suspension during the addition of the two liquids within the above range, a nickel film having a columnar structure can be formed more easily. In order to maintain the concentration of the complexing agent in the aqueous suspension within the above range, the addition rate (nickel precipitation rate) of the nickel ion-containing liquid and the reducing agent-containing liquid, or the initial concentration of the complexing agent in the aqueous suspension or the nickel ion-containing liquid What is necessary is just to adjust the density | concentration of a complexing agent. These values are as mentioned above.

While adding the two liquids to the aqueous suspension, it is preferable to keep the above-mentioned load in the range of 0.1 to 15 m 2 / liter, especially 1 to 10 m 2 / liter. In this way, nickel can be uniformly precipitated and a nickel film having a columnar structure can be more easily formed. For the same reason, it is also preferable that the loading amount at the time when the addition of the two liquids is finished and the reduction of the nickel ions is completed.

In this way, a plated powder in which a nickel film is formed on the surface of the core material powder is obtained. And the grain boundary in the nickel film in this plating powder is mainly oriented in the thickness direction of the said nickel film.

Although depending on the type of reducing agent used, the pH of the aqueous suspension during the reduction reaction of nickel ions is preferably maintained in the range of 3 to 13, especially 4 to 11, in that it prevents the formation of water-insoluble precipitates of nickel. Do. In order to adjust pH, what is necessary is just to add a predetermined amount of pH adjusters, such as sodium hydroxide, in a reducing agent containing liquid.

The obtained plating powder is separated after filtration and washing with water are repeated several times. In addition, you may perform the formation process of the gold plating layer as an uppermost layer on a nickel film as an addition process. Formation of a gold plating layer can be performed according to a conventionally well-known electroless plating method. For example, a gold-plated layer is formed on a nickel film by adding an electroless plating solution containing ethylenediaminetetraacetic acid tetrasodium, trisodium citrate and potassium cyanide, and adjusting the pH to sodium hydroxide in an aqueous suspension of plating powder. do.

The plating powder obtained as described above is suitably used as an anisotropic conductive film (ACF), a heat seal connector (HSC), or a conductive material for connecting the electrodes of the liquid crystal display panel to the circuit board of the LSI chip for driving. .

The present invention is not limited to the above embodiment. For example, in the above embodiment, a nickel film having a columnar structure was formed on the surface of the core powder, but a nickel film having a columnar structure was formed on the surface of the core powder on the surface of the powder in which a metal film was formed. You may be. In addition, the manufacturing method of the plating powder of this invention is not restrict | limited to the method mentioned above.

EXAMPLE

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 1-4]

(1) Catalytic Treatment

Spherical silica having an average particle diameter of 12 µm and a specific gravity of 2.23 was used as the core material powder. The 40g was poured into 400 milliliters of aqueous conditioner aqueous solution ("Cleaner Conditioner 231" manufactured by Shipley). The concentration of the conditioner aqueous solution was 40 milliliters / liter. Subsequently, the mixture was stirred for 30 minutes while giving an ultrasonic wave at a liquid temperature of 60 ° C to perform surface modification and dispersion treatment of the core powder. The aqueous solution was filtered and the heartwood powder which was once repulsed with water was used as a slurry of 200 milliliters. Into this slurry was added 200 milliliters of aqueous tin chloride solution. The concentration of this aqueous solution was 5 × 10 ⁻³ mol / liter. 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 core powder. Subsequently, the aqueous solution was filtered and washed once with pulp. Subsequently, the core material powder was made into a 400 milliliter slurry and kept at 60 degreeC. 2 milliliters of 0.11 mol / liter palladium chloride aqueous solution was added with slurry stirring, using ultrasonic wave together. The stirring was kept for 5 minutes as it was, and the activation process which captures palladium ion on the surface of a core powder was performed. Subsequently, the aqueous solution was filtered, and the heartwood powder which was once repulsed and bathed was used as a slurry of 200 milliliters. The slurry was stirred while using ultrasonic waves, and 20 milliliters of a mixed aqueous solution of 0.017 mol / liter of dimethylamine borane and 0.16 mol / liter of boric acid was added thereto. It stirred for 2 minutes, using ultrasonic wave together at normal temperature, and the palladium ion reduction process was performed.

(2) Initial thin film formation process

The 200 milliliter slurry obtained by the process of (1) was added to the initial thin film forming liquid of (a) shown in Table 1, stirring, and it was made into the aqueous suspension. The initial thin film formation liquid was warmed to 75 ° C., and the liquid amount was 1.8 liters. The generation of hydrogen was recognized immediately after the slurry was added to confirm the onset of initial thin film formation. After 1 minute, 0.063 mol of sodium hypophosphite was added and stirring was continued for 1 minute. The loading of the aqueous suspension was 4.5 m 2 / liter.

(3) electroless plating process

To the aqueous suspension obtained in the initial thin film formation step, two liquids of the nickel ion-containing liquid of (b) and the reducing agent-containing liquid of (c) shown in Table 1 were added at the addition rates shown in Table 1, respectively. The addition amount was 870 milliliters, respectively. Hydrogen evolution was recognized immediately after addition of the two liquids, and the start of the plating reaction was confirmed. While the addition of the two liquids was completed, the concentration of the complexing agent with amino groups in the aqueous suspension was maintained at the concentration shown in Table 1. After the addition of the two liquids was completed, stirring was continued while maintaining the temperature of 75 ° C until the foaming of hydrogen stopped. The load amount after completion of addition of the two liquids was 2.4 m 2 / liter. The aqueous suspension was then filtered and the filtrate was washed three times with pulp and dried in a 110 ° C. vacuum dryer. In this way, the plating powder which has a nickel-phosphorus alloy plating film was obtained. As a result of observing the cross section of the plated film of the plated powder obtained by SEM with a magnification of 50000 times, as shown in Fig. 1, the grain boundaries of the film were mainly oriented in the thickness direction cross section of the film. The thickness of the plating film computed from the addition amount of nickel ion was 0.54 micrometer.

[Examples 5-8]

1 liter of the electroless plating liquid for gold plating was prepared. The electroless plating solution contains 0.027 mol / liter of tetrasodium ethylenediamine tetraacetate, 0.038 mol / liter of trisodium citrate and 0.01 mol / liter of potassium cyanide, and the pH is adjusted to 6 by aqueous sodium hydroxide solution. . While stirring the electroless plating liquid of 60 degreeC of liquid temperature, 33g of plating powders obtained in Examples 1-4 were added to this plating liquid, and gold plating process was performed for 20 minutes. The liquid was then filtered, and the filtrate was repulsed three times and then dried in a drier at 110 ° C. By doing in this way, the plating powder in which the gold electroless plating layer was formed on the nickel film was obtained. The thickness of the gold plating layer computed from the addition amount of gold ion was 0.025 micrometer.

EXAMPLE 9

(1) Catalytic Treatment

A spherical benzoguanamine-melamine-formalin resin (manufactured by Nippon Shokubai Co., Ltd., trade name "Ester") having an average particle diameter of 14 µm and a specific gravity of 1.39 was used as the core powder. The 30g was made into 400 milliliters of slurry, and it kept at 60 degreeC. 2 milliliters of 0.11 mol / liter palladium chloride aqueous solution was added, stirring ultrasonic slurry together. The stirring was kept for 5 minutes as it was, and the activation process which captures palladium ion on the surface of a core powder was performed. Subsequently, the aqueous solution was filtered, and the heartwood powder which was once repulsed and wetted was used as a slurry of 200 milliliters. The slurry was stirred while using ultrasonic waves, and 20 milliliters of a mixed aqueous solution of 0.017 mol / liter of dimethylamine borane and 0.16 mol / liter of boric acid was added thereto. The mixture was stirred for 2 minutes while using ultrasonic waves at room temperature to reduce palladium ions.

(2) Initial thin film formation process

The 200 milliliters of the slurry obtained in the step (1) was added to the initial thin film forming solution of (a) shown in Table 1 with stirring to form an aqueous suspension. The initial thin film formation liquid was warmed to 75 ° C., and the liquid amount was 1.8 liters. Immediately after the slurry was introduced, the generation of hydrogen was recognized to confirm the onset of initial thin film formation. After 1 minute, 0.042 mol of sodium hypophosphite was added and stirring was continued for 1 minute. The loading of the aqueous suspension was 4.6 m 2 / liter.

(3) electroless plating process

To the aqueous suspension obtained in the initial thin film formation step, two liquids of the nickel ion-containing liquid of (b) and the reducing agent-containing liquid of (c) shown in Table 1 were added at the addition rates shown in Table 1, respectively. The addition amount was 409 milliliters, respectively. The generation of hydrogen was recognized immediately after addition of the two liquids, and the start of the plating reaction was confirmed. While the addition of the two liquids was completed, the concentration of the complexing agent with amino groups in the aqueous suspension was maintained at the concentration shown in Table 1. After the addition of the two liquids was completed, stirring was continued while maintaining the temperature of 75 ° C until the foaming of hydrogen stopped. The load amount after completion of addition of the two liquids was 3.3 m 2 / liter. Subsequently, the aqueous suspension was filtered, the filtrate was washed three times with pulp, and then dried in a 110C vacuum dryer. In this way, the powder which has a nickel-phosphorus alloy plating film was obtained. As a result of observing the cross section of the plated film of the plated powder obtained by SEM with a magnification of 50000 times, as shown in Fig. 1, the grain boundaries of the film were mainly oriented in the thickness direction cross section of the film. The thickness of the plating film computed from the addition amount of nickel ion was 0.26 micrometer.

EXAMPLE 10

Except using 21.36g of plating powder obtained in Example 9, it carried out similarly to Example 5, and obtained the plating powder in which the gold electroless plating layer was formed on the nickel film. The thickness of the gold plating layer computed from the addition amount of gold ion was 0.025 micrometer.

EXAMPLE 11

(1) Catalytic Treatment

A spherical acrylic resin having an average particle diameter of 10 µm and a specific gravity of 1.33 was used as the core material powder. 20 g of the slurry was used as a slurry of 200 milliliters, and 200 milliliters of aqueous tin chloride solution was added to the slurry. The concentration of this aqueous solution was 5 × 10 ⁻³ mol / liter. It stirred at normal temperature for 5 minutes, and performed the sensitization process which makes tin ion adsorb | suck to the surface of core powder. Subsequently, the aqueous solution was filtered and washed once with pulp. Subsequently, the core material powder was made into a 400 milliliter slurry and kept at 60 degreeC. 2 milliliters of 0.11 mol / liter 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 a core powder was performed. Subsequently, the aqueous solution was filtered, and the heartwood powder which was once repulsed and wetted was used as a 200 milliliter slurry. The slurry was stirred while using ultrasonic waves, and 20 milliliters of a mixed aqueous solution of 0.017 mol / liter of dimethylamine borane and 0.16 mol / liter of boric acid was added thereto. The mixture was stirred for 2 minutes while using ultrasonic waves at room temperature to reduce palladium ions.

(2) Initial thin film formation process

The 200 milliliters of the slurry obtained in the step (1) was added to the initial thin film forming solution of (a) shown in Table 1 with stirring to form an aqueous suspension. The initial thin film formation liquid was warmed to 75 ° C., and the liquid amount was 1.8 liters. Immediately after the slurry was injected, hydrogen was recognized and the start of the plating reaction was confirmed. After 1 minute, 0.042 mol of sodium hypophosphite was added and stirring was continued for 1 minute. The loading of the aqueous suspension was 4.5 m 2 / liter.

(3) electroless plating process

To the aqueous suspension obtained in the initial thin film formation step, two liquids of the nickel ion-containing liquid of (b) and the reducing agent-containing liquid of (c) shown in Table 1 were added at the addition rates shown in Table 1, respectively. The addition amount was 404 milliliters, respectively. The generation of hydrogen was recognized immediately after addition of the two liquids, and the start of the plating reaction was confirmed. While the addition of the two liquids was completed, the concentration of the complexing agent having an amino group in the aqueous suspension was maintained at the concentration shown in Table 1. The load amount after completion of addition of the two liquids was 3.2 m 2 / liter. After the addition of the two liquids was completed, stirring was continued while maintaining the temperature of 75 ° C until the foaming of hydrogen stopped. Subsequently, the aqueous suspension was filtered, the filtrate was washed three times with pulp, and then dried in a 110C vacuum dryer. In this way, the powder which has a nickel-phosphorus alloy plating film was obtained. As a result of observing the cross section of the plated film of the plated powder obtained by SEM with a magnification of 50000 times, as shown in Fig. 1, the grain boundaries of the film were mainly oriented in the thickness direction cross section of the film. The thickness of the plating film computed from the addition amount of nickel ion was 0.26 micrometer.

EXAMPLE 12

Except using 17.0g of plating powder obtained in Example 11, it carried out similarly to Example 5, and obtained the plating powder in which the gold electroless plating layer was formed on the nickel film. The thickness of the gold plating layer computed from the addition amount of gold ion was 0.025 micrometer.

[Comparative Example 1]

In this comparative example, the electroless plating bath method conventionally performed was adopted. Up to the catalytic treatment step was the same as in Example 1. In an electroless plating solution, 0.11 mol / liter of nickel sulfate, 0.24 mol / liter of sodium hypophosphite, 0.26 mol / liter of sodium malate, 0.18 mol / liter of sodium acetate, and 2 × 10 ⁻⁶ mol / liter of lead acetate And pH adjusted to 5 was used. The 6-liter electroless plating solution was warmed to 75 ° C, dried, and the core material powder subjected to the catalyzed treatment was added to the bath, stirred and dispersed, to initiate a reduction reaction of nickel. A pH automatic control device was used and 5 mol / liter sodium hydroxide aqueous solution was added to maintain the pH of the liquid during the reduction reaction at 5. Moreover, when reaction stopped in the middle, 2 mol / liter sodium hypophosphite aqueous solution was added little by little, and reaction was continued. If the solution did not foam even after adding an aqueous sodium hypophosphite solution, all the additions were stopped, the solution was filtered, the filtrate was washed three times, and then dried in a vacuum dryer at 110 ° C. By doing in this way, the powder which has a nickel-phosphorus alloy plating film was obtained. As a result of observing the cross section of the plated film of the obtained powder by SEM with an enlarged magnification of 50000 times, as shown in Fig. 2, a grain-shaped grain boundary in the shape of a film was observed in the cross section in the thickness direction of the film. Since this plating powder was manufactured by the electroless plating system conventionally performed, the fine nickel decomposition product was mixed and it was difficult to put it into practical use.

[Comparative Example 2]

The core powder after the catalyzed treatment obtained in the same manner as in Example 1 was used as a slurry of 200 milliliters, which was added to the initial thin film forming solution of (a) shown in Table 1 with stirring to form an aqueous suspension. The initial thin film formation liquid was warmed to 75 ° C., and the liquid amount was 1.8 liters. Immediately after the slurry was introduced, the generation of hydrogen was recognized to confirm the onset of initial thin film formation. After 1 minute, 0.063 mol of sodium hypophosphite was added and stirring was continued for 1 minute. Two liquids of the nickel ion-containing liquid of (b) and the reducing agent-containing liquid of (c) shown in Table 1 were added to this aqueous suspension at the addition rates shown in Table 1, respectively. The addition amount was 870 milliliters, respectively. The generation of hydrogen was recognized 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 the temperature of 75 ° C until the foaming of hydrogen stopped. Subsequently, the aqueous suspension was filtered, the filtrate was washed three times with pulp, and then dried in a 110C vacuum dryer. In this way, the powder which has a nickel-phosphorus alloy plating film was obtained. As a result of observing the cross section of the plated film of the plated powder obtained by SEM with an enlarged magnification of 50000 times, as in FIG. The thickness of the plating film computed from the addition amount of nickel ion was 0.54 micrometer.

(Comparative Example 3)

A plating powder in which a gold electroless plating layer was formed on a nickel film was obtained in the same manner as in Example 5 except that 33 g of the plating powder obtained in Comparative Example 2 was used. The thickness of the gold plating layer computed from the addition amount of gold ion was 0.025 micrometer.

[Performance evaluation]

About the plating powder obtained in Examples 1-12 and Comparative Examples 1-3, the volume specific resistance was measured with the following method, and heat resistance was also evaluated. These results are shown in Table 2 below.

(Measurement of volume specific resistance)

In a resin cylinder of 10 mm in diameter, placed vertically, 1.0 g of plated powder was placed, and the electrical resistance between the upper and lower electrodes was measured under a load of 10 kg to obtain a volume specific resistance.

[Heat Resistance Evaluation of Plating Film]

The plating powder was stored for 24 hours, 48 hours, 72 hours, 96 hours, and 120 hours under an oxidizing atmosphere at 200 ° C. About the plating powder after storage, the volume specific resistance value was measured in accordance with the method mentioned above, and the resistance value was made into the measure of heat resistance.

(a) Initial thin film formation liquid (mol / l) (b) Nickel ion-containing liquid (mol / l) (c) Reducing agent-containing liquid (mol / l) Addition rate ml / min Complexing agent concentration with amino group mol / l Example 1 Glycine 0.27 Nickel Sulfate 0.013 Sodium Hypophosphite 0.032 Glycine 0.54 Nickel Sulfate 0.86 Sodium hypophosphite 2.57 Sodium hydroxide 2.6 7 0.27 Example 2 Ethylenediamine 0.33 Nickel Sulfate 0.013 Sodium Hypophosphite 0.032 Ethylenediamine 0.66 Nickel Sulfate 0.86 Sodium hypophosphite 2.57 Sodium hydroxide 2.6 7 0.33 Example 3 Glycine 0.27 Sodium Tartrate 0.087 Nickel Sulfate 0.013 Sodium Hypophosphite 0.032 Glycine 0.54 Sodium Tartrate 0.17 Nickel Sulfate 0.86 Sodium hypophosphite 2.57 Sodium hydroxide 2.6 7 0.27 Example 4 Glycine 2.0 Nickel Sulfate 0.013 Sodium Hypophosphite 0.032 Glycine 4.0 Nickel Sulfate 0.86 Sodium hypophosphite 2.57 Sodium hydroxide 2.6 7 2.00 Example 9 Glycine 0.27 Nickel Sulfate 0.0086 Sodium Hypophosphite 0.021 Glycine 0.54 Nickel Sulfate 0.86 Sodium hypophosphite 2.57 Sodium hydroxide 2.6 3 0.27-0.30 Example 11 Glycine 0.27 Nickel Sulfate 0.0086 Sodium Hypophosphite 0.021 Glycine 0.54 Nickel Sulfate 0.86 Sodium hypophosphite 2.57 Sodium hydroxide 2.6 3 0.27-0.30 Comparative Example 2 Nickel sulfate 0.013 sodium hypophosphite 0.032 Nickel Sulfate 0.86 Sodium hypophosphite 2.57 7 -

Volume specific resistance (mΩcm) After plating 24 hours later 48 hours later After 72 hours 96 hours later 120 hours later  Example 1 24 59 66 95 92 91  Example 2 19 32 50 78 90 93  Example 3 24 48 63 85 89 98  Example 4 20 50 70 84 90 101  Example 5 4.5 4.8 4.9 5.2 4.6 6.3  Example 6 3.2 5 5.5 5.4 5.6 5.9  Example 7 4.2 5.2 5.2 5.3 6 6  Example 8 3.8 4.9 5 5.3 5.9 6.3  Example 9 45 56 58 74 94 110  Example 10 2.2 4.1 5.8 9 10 10  Example 11 42 60 63 88 98 105  Example 12 4.3 4.2 8.8 10 11 10  Comparative Example 1 Not measurable ^* Not measurable ^* Not measurable ^* Not measurable ^* Not measurable ^* Not measurable ^*  Comparative Example 2 48 30000 More than 100000 More than 100000 More than 100000 More than 100000  Comparative Example 3 4.2 1200 23000 More than 100000 More than 100000 More than 100000

*: The fine nickel decomposition product was mixed and could not be measured.

The results of Table 2 show that the plating powder (inventive product) of each example had a sufficiently low electrical resistance and a small increase in electrical resistance even when stored for a long time at a high temperature, so that the heat resistance was sufficiently high. On the other hand, although the plating powder of a comparative example has low electric resistance, it turns out that electric resistance increases by long time storage, and heat resistance is low.

As described above, according to the present invention, the heat resistance of the electroless electroless plating powder is improved, and the increase in the electrical resistance becomes small even when stored at a high temperature for a long time.

1 is a scanning electron micrograph showing an example of a cross section of a plated film of the conductive electroless plating powder of the present invention.

2 is a scanning electron micrograph showing an example of a cross section of a plated film of a conventional conductive electroless plating powder.

Claims (6)

In the electroless electroless plating powder in which the nickel film was formed on the surface of the core particle by the electroless plating method, the grain boundary in the nickel film is mainly oriented in the thickness direction of the nickel film. . The conductive electroless plating powder according to claim 1, wherein a gold electroless plating layer is formed on the outermost surface. In the method for producing a conductive electroless plating powder according to claim 1, After capturing the precious metal ion in the core powder having the capturing ability of the precious metal ion or giving the capturing ability of the precious metal ion by surface treatment, the precious metal ion is reduced to carry the precious metal on the surface of the core powder, Subsequently, the core powder is dispersed and mixed in an initial thin film forming solution containing a complexing agent of nickel ions, a reducing agent and an amine compound, and nickel ions are reduced to form an initial thin film of nickel on the surface of the core powder. Subsequently, two solutions of the nickel ion-containing liquid and the reducing agent-containing liquid containing the complexing agent and the same kind of complexing agent were separately added simultaneously to the core powder and the aqueous suspension containing the complexing agent on which the initial thin film was formed. A method for producing a conductive electroless plating powder, characterized by performing an electroless plating reaction. The concentration of the complexing agent in the aqueous suspension is 0.003 to 10 mol / liter in the process of adding the nickel ion-containing liquid and the reducing agent-containing liquid to the aqueous suspension containing the core powder. Conductive electroless plating powder which adjusts the addition amount of the said nickel ion containing liquid and the said reducing agent containing liquid, or the initial concentration of the said complexing agent in the said aqueous suspension, or the density | concentration of the said complexing agent in the said nickel ion containing liquid so that it may remain in the range of Manufacturing method. The method for producing a conductive electroless plating powder according to claim 3 or 4, wherein the complexing agent is glycine or ethylenediamine. The said aqueous suspension with respect to the volume of the said aqueous suspension before adding the said nickel ion containing liquid and the said reducing agent containing liquid to the aqueous suspension containing the said core material powder. The manufacturing method of the electroconductive electroless plating powder whose ratio of the total surface area of the said core material powder contained in a sieve is 0.1-15 m <2> / liter.