WO2007119417A1

WO2007119417A1 - Conductive powder plated by electroless plating and process for producing the same

Info

Publication number: WO2007119417A1
Application number: PCT/JP2007/055497
Authority: WO
Inventors: Masaaki Oyamada; Yasuhiro Abe
Original assignee: Nippon Chemical Industrial Co., Ltd
Priority date: 2006-03-28
Filing date: 2007-03-19
Publication date: 2007-10-25
Also published as: TW200745377A; KR101305574B1; CN101415863A; CN101415863B; JP4849930B2; JP2007262495A; KR20080111022A; TWI419996B

Abstract

A conductive powder plated by electroless plating which, even when composed of fine particles having an average particle diameter of, in particular, 20 µm or smaller, has excellent deposit adhesion imparted thereto without using chromic acid, which is causative of environmental pollution, permanganic acid, etc.; and a process for industrially advantageously producing the powder. The conductive powder plated by electroless plating is characterized by comprising a core powder coated with a melamine resin and a metallic coating film deposited thereon by electroless plating. The process is characterized by comprising: a step in which a core powder is brought into contact with an initial condensate for a melamine resin and the initial condensate is polymerized to obtain a core powder coated with a melamine resin; a step in which a noble metal is deposited on the surface of the core powder coated with the melamine resin; and a step in which the core powder having the noble metal deposited thereon is plated by electroless plating.

Description

Specification

Conductive electroless plating powder and method for producing the same

Technical field

[0001] The present invention relates to a conductive electroless plating powder and a method for producing the same.

Background art

Conventionally, when manufacturing electroless plating products such as conductive electroless plating powder, when the object to be coated is hydrophobic, the surface is hydrophilized to form a metal film. It is necessary to improve the adhesion between the cover and the object to be covered. Conventionally, strong oxidizing agents such as chromic acid and permanganic acid have been used as means for improving adhesion.

[0003] However, these oxidants have a large environmental burden! /. With appropriate reduction and cleaning treatment, chromium and manganese will hardly remain in the plated product, but complete removal is very difficult.

[0004] Therefore, as a hydrophilization treatment method with a small environmental load, for example, in Patent Document 1 below, an aminosilane compound, a glycol compound, a nitrile compound, a titanate compound, a butadiene polymer, and linoleic acid are used as a synthetic resin material. Unsaturated fatty acids such as linolenic acid, etc. A method is proposed in which the synthetic resin material is coated with a selected noble metal-capturing surface treatment material to carry noble metal ions, and then electroless plating is performed. .

[0005] However, in the method described in Patent Document 1, it is difficult to obtain a material having excellent adhesiveness particularly for fine particles having an average particle diameter of 20 μm or less. Difficult to use.

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

Disclosure of the invention

Problems to be solved by the invention

[0006] Therefore, the object of the present invention is to provide a conductive material having excellent adhesion without using chromic acid, permanganic acid, or the like, which causes environmental pollution, especially fine particles having an average particle diameter of 20 μm or less. An electroless electroless powder and an industrially advantageous production method thereof. Means for solving the problem [0007] The present invention provides a conductive electroless plating powder characterized in that the surface of the core powder is coated with melamine resin and a metal film is formed by electroless plating. By doing so, the above-mentioned purpose is achieved.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described based on preferred embodiments thereof. The conductive electroless plating powder of the present invention (hereinafter also simply referred to as a platter powder) is obtained by coating the surface of the core material powder with melamine resin and further forming a metal film by electroless platter. It will be.

[0009] Either an organic powder or an inorganic powder is used, with no particular restriction on the type of core powder used in the present invention. The surface of the core material powder may be hydrophobic or hydrophilic. However, the method of the present embodiment is particularly effective for the core material powder having a hydrophobic surface. The core powder is preferably substantially insoluble in water, and more preferably does not dissolve or change in acid or alkali.

[0010] The shape of the core powder is not particularly limited. In general, the core powder can be in the form of a powder, but other shapes such as fibers, hollows, plates, and needles can be used. It may be a thing. In the present invention, among these, a spherical one is particularly preferable in that it has excellent filling properties when used as a conductive filler.

[0011] As specific examples of the core material powder, as an inorganic substance, metal (including an alloy), glass, ceramics

, Silica, carbon, metal or non-metal oxides (including hydrates), metal silicates including aluminosilicates, metal carbides, metal nitrides, metal carbonates, metal sulfates, metal phosphates, Examples thereof include metal sulfides, metal acid salts, metal halides, and carbon. Organic substances include natural fiber, natural resin, polyethylene, polypropylene, polychlorinated butyl, polystyrene, polybutene, polyamide, polyacrylic acid ester, polyacrylic nitrile, polyacetal, ionomer, polyester and other thermoplastic resin, alkyd Examples of the resin include resin, phenol resin, urea resin, benzoguanamine resin, melamine resin, xylene resin, silicone resin, epoxy resin, and diallyl phthalate resin. These may be used alone or as a mixture of two or more.

[0012] As another preferable physical property of the core powder used in the present invention, the average particle size is 0.5 to 100. μm, especially 0.8 to 80 μm, especially 1 to 20 μm suppresses agglomeration during the plating process, and is particularly effective from the viewpoint of adapting to a narrow pitch as electroconductive particles after electroless plating. Preferred. In addition, the average particle diameter of core material powder shows the value measured using the electrical resistance method.

[0013] Furthermore, the particle size distribution of the core material powder measured by the method described above has a range. In general, the width of the particle size distribution of the powder is represented by a coefficient of variation represented by the following calculation formula (1).

Coefficient of variation (%) = (standard deviation Z average particle size) X 100 Formula (1) A large coefficient of variation indicates that there is a range of distribution, while a small coefficient of variation indicates that the particle size distribution is sharp. Indicates that there is. In the present embodiment, it is preferable to use a core material powder having a coefficient of variation of 50% or less, particularly 30% or less, particularly 20% or less. The reason for this is that 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 effective contribution ratio for connection is increased.

[0014] The coating amount of melamine rosin varies depending on the type and shape of the core powder used, but in many cases it is 0.1 to 15% by weight, preferably 0.5 to 10% by weight. desirable. The reason for this is that when the coating amount of melamine resin is less than 0.1% by weight, the coating amount is insufficient and the plating adhesion tends to be difficult to obtain due to excellent plating adhesion. This is because in the step (1) of obtaining the core powder coated with melamine resin, fine particle melamine resin is generated alone and tends to remain as a foreign substance. Further, the melamine rosin may be modified.

[0015] The metal film in the electroless electroless plating powder is usually a single metal single layer structure. If desired, the metal film may have a multilayer structure of two or more different metals. In addition, the metal film may be crystalline or amorphous depending on the type and staking conditions. Furthermore, the metal film may be magnetic or non-magnetic. The metal here includes not only a simple metal but also an alloy (for example, a nickel-phosphorus alloy or a nickel-boron alloy). Usable metals include Ni, Fe, Cu, Co, Pd, Ag, Au, Pt, and Sn. The thickness of the metal film is preferably 0.001 to 2 μm, particularly preferably 0.001 to 1 μm. The thickness of the metal film can be calculated based on the amount of nickel ions added and the chemical analysis ability.

[0016] Ni is also preferable in terms of economic viewpoint. In the following embodiment, nickel is used as an example of the metal. Although explained, the metal that can be used is not limited to this.

[0017] The production method of the present embodiment includes a step of contacting a core material powder and an initial condensate of melamine resin, and performing a polymerization reaction of the initial condensate to obtain a core material powder coated with melamine resin Next, a step of supporting a noble metal on the surface of the core material powder coated with the melamine resin, and a step of subjecting the core material powder supporting the noble metal to an electroless plating process in the next step. However, by including (1) a step of obtaining a core powder coated with melamine rosin, (2) a catalytic treatment step, (3) an initial thin film formation step, and (4) an electroless plating step, Stable quality plating powder can be advantageously obtained industrially.

[0018] In the step (1), the core material powder is coated with the melamine resin by bringing the core material powder and the initial condensate of the melamine resin into contact with each other to perform a polymerization reaction of the initial condensate. This is a step of obtaining a core powder.

[0019] In the present invention, the initial condensate of melamine resin means a product in which a condensation reaction is caused by heating or addition of an acid catalyst to produce melamine resin. The initial condensate of melamine resin may be a commercially available product, or a product obtained by reacting a melamine compound with an aldehyde compound is used as the initial condensate of melamine resin. May be.

[0020] Examples of the melamine compound include melamine, a melamine compound obtained by substituting hydrogen of an amino group of melamine with an alkyl group, a alkenyl group, or a phenol group (for example, JP 09-1432 38 A). ), Substituted melamine compounds in which the hydrogen of the amino group of melamine is substituted with a hydroxyalkyl group or an aminoalkyl group (for example, see JP-A-5-202157), etc. Melamine is preferred because it is readily available and inexpensive. Some of the melamine compounds are also urea, thiourea, ethylene urea and other ureas, benzoguanamine, acetoguanamine and other guanamines, phenol, cresol, alkylphenol, resorcin, hydroquinone, pyrogallol and other phenols, -It may be substituted with phosphorus.

[0021] Examples of the aldehyde compound include formaldehyde, paraformaldehyde, acetoaldehyde, benzaldehyde, furfural and the like, and formaldehyde and paraformaldehyde are preferable in terms of reactivity with the melamine compound. The addition amount of the aldehyde compound is 1.1 to 6.0 times mol, preferably 1.2 to 4.0 in terms of a molar ratio to the melamine compound. It is preferred to be double moles.

[0022] The solvent that can be used is particularly preferably water, but may be used as a mixed solvent of water and an organic solvent. In this case, as the organic solvent that can be used, it is preferable to use a solvent that can dissolve the initial condensate of melamine resin, for example, alcohols such as methanol, ethanol, and propanol, dioxane, tetrahydrofuran, 1

, Ethers such as 2-dimethoxyethane, and polar solvents such as dimethylformamide and dimethyl sulfoxide.

[0023] The reaction of the melamine compound and the aldehyde compound is carried out at a pH of 8 to 9. If necessary, the reaction can be carried out by adding a base group. Usable bases such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and aqueous ammonia can be used as the base that can be used. Reaction temperature is 25-: An initial condensate of melamine rosin having a molecular weight of about 200-700 with LOO can be obtained.

[0024] Further, the melamine modified with alcohol by reacting the initial condensate of melamine resin with alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol in the presence of a small amount of acidic substance. An initial condensate of rosin can be obtained.

[0025] The amount of the initial condensate of melamine rosin varies depending on the type of the core powder used, but in many cases is 0.1 to 15% by weight, preferably 0.5 to 10% by weight. It is desirable to do.

[0026] In the present invention, the reaction operation in the step (1) of obtaining the core material powder coated with melamine rosin comprises preparing a solvent containing the core material powder and adding the solvent to the solvent. A method of adding an initial condensate of melamine resin and performing a polymerization reaction of the initial condensate, and adding the core powder to a solvent containing the initial condensate of melamine resin and polymerizing the initial condensate Method for carrying out reaction, or core material powder, melamine compound and aldehyde compound, a predetermined amount is added, and if necessary, an alkali agent is added and an initial condensate of melamine resin is directly added in a solvent. The method of performing the polymerization reaction can be used. In addition, the polymerization reaction may be carried out by adding an acid catalyst if necessary, and the reaction is carried out under heating at 40 to LOO ° C. After completion of the reaction, solid-liquid separation is carried out by a conventional method, followed by drying at 60 to 180 ° C Alternatively, spray-dry the reaction solution as it is and cover with melamine rosin. Covered core powder can be obtained.

[0027] The acid catalyst that can be used in the polymerization reaction is not particularly limited. 1S For example, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, methanesulfonic acid, benzenesulfonic acid, paratoluenesulfonic acid, alkylbenzenesulfonic acid In addition, sulfonic acids such as sulfamic acid, and organic acids such as formic acid, oxalic acid, benzoic acid, and phthalic acid can be used.

[0028] In the catalytic treatment step (2), noble metal ions are captured by a core material powder that has the ability to capture noble metal ions or that has been provided with a surface treatment. This is a step of reducing this and supporting the noble metal on the surface of the core powder. In the initial thin film forming step (3), the core material powder on which the noble metal is supported is dispersed and mixed in the initial thin film forming liquid containing nickel ions, a reducing agent and a complexing agent, and the nickel ions are reduced. This is a process of forming an initial nickel thin film on the surface of the core powder. The electroless plating process (4) is a process for producing a plating powder having a nickel coating on the surface of the core powder by electroless plating. Hereinafter, each process is explained in full detail.

[0029] (2) Catalytic treatment process

The core material powder coated with the melamine resin obtained in the step (1) is surface-modified so that the surface thereof has a precious metal ion capturing ability or a precious metal ion capturing ability. The noble metal ions are preferably palladium or silver ions. Having a precious metal ion scavenging ability means that the precious metal ion can be captured as a chelate or salt.

[0030] Next, the core powder is dispersed in a dilute 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. Noble metal salt concentration is sufficient surface area lm ² per 1 X 10- ⁷ ~1 X 10- ² mol per mol of silver powder. The core powder with the precious metal ions captured is separated from the system and washed with water. Subsequently, the core powder is suspended in water, and a reducing agent is added thereto to reduce the precious metal ions. As a result, the noble metal is supported on the surface of the core powder. Examples of the reducing agent include sodium hypophosphite, sodium borohydride, potassium borohydride, dimethylamine borane, hydrazine, formalin and the like.

[0031] Before the noble metal ions are trapped on the surface of the core powder, a sensitivity treatment for adsorbing tin ions on the powder surface may be performed. To adsorb tin ions on the powder surface, for example, The surface-modified core material powder may be put into an aqueous stannous chloride solution and stirred for a predetermined time.

[0032] (3) Initial thin film formation process

The initial thin film forming step is mainly performed for the purpose of smoothing the uniform precipitation of nickel on the core powder. In the initial thin film forming step, first, the core powder carrying the noble metal is sufficiently dispersed in water. For dispersion, a shearing dispersion device such as a colloid mill or a homogenizer can be used. In dispersing the core powder, for example, a dispersant such as a surfactant can be used as necessary. 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. This initiates a nickel ion reduction reaction, and an initial nickel thin film is formed on the surface of the core powder. As described above, since the initial thin film forming step is mainly performed for the purpose of uniform precipitation, the initial thin film of nickel to be formed 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 preferably 0.001 to 1 μm. The initial thin film thickness can be calculated from the amount of nickel ions added and the ability to analyze the ions.

[0033] From the viewpoint of forming the initial film thickness described above, in the initial thin film forming liquid -. Tsu Ke concentration Noreion ί or 2. 0 X 10- ⁴ ~1 0 Monore / Rittonore, especially 1. 0 X 10 — ^{3 to} 0.1 monolayer / liter is preferable. As the nickel ion source, a water-soluble nickel salt such as nickel sulfate or nickel chloride is used. From the same viewpoint, it is preferable that the initial concentration ί of the reducing agent in the thin film-forming solution or ⁴ X 10- 4 ~2. 0 Monore / Rittonore, especially 2. 0 X 10- ³ ~0. 2 Monore / liters . As the reducing agent, those similar to those used for the reduction of the noble metal ions described above can be used.

[0034] The initial thin film forming liquid preferably contains a complexing agent. The complexing agent is a compound that has a complex forming action on the metal ion to be plated. In the present embodiment, an organic carboxylic acid or a salt thereof such as citrate, hydroxyacetic acid, tartaric acid, malic acid, lactic acid or dulconic acid or an alkali metal salt or ammonium salt thereof can be used as a complexing agent. In addition, amine groups such as glycine, alanine, ethylenediamine, diethylenetriamine, triethylenetetramine, pentaethylenehexamine and other amino groups A compound having can also be used. These complexing agents can be used alone or in combination of two or more. From the viewpoint 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 monole / Ritsunore, particularly 0.006 to 4 monore / Ritsunore! /.

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

[0035] The aqueous suspension obtained by mixing the aqueous suspension containing the core powder and the initial thin film forming liquid is then subjected to an electroless plating process described later. In the aqueous suspension before being subjected to the electroless plating process, the ratio of the total surface area of the core powder contained in the aqueous suspension to the volume of the aqueous suspension ( This ratio is generally referred to as the load amount) 0.1 to 15 m ² / l, especially 1 to LOm ² / l, which is a point force that can easily form a nickel film with excellent adhesion. preferable. If the load is too high, nickel ions in the liquid phase are severely reduced 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. Therefore, it becomes difficult to form a uniform nickel film.

[0036] (3) Electroless plating process

For the electroless plating process, (a) a core powder on which an initial thin film is formed and an aqueous suspension containing the complexing agent, (b) a nickel ion-containing liquid, and (c) a reducing agent Use 3 liquids. As the aqueous suspension (a), the one obtained in the above-described initial thin film forming step may be used as it is.

[0037] Separately from the aqueous suspension (a), two liquids are prepared: a nickel ion-containing liquid (b) and a reducing agent-containing liquid (c). The nickel ion-containing liquid is an aqueous solution of a water-soluble nickel salt such as nickel sulfate or nickel chloride as a nickel ion source. The nickel ion concentration should be 0.1 to 1.2 monolith / lit nore, especially 0.5 to 1.0 monolet / lit nore, and it can easily form a nickel film with excellent strength and adhesion. Preferred from.

[0038] The nickel ion-containing liquid preferably contains a complexing agent of the same type as the complexing agent contained in the aqueous suspension. That is, it is preferable that the same kind of complexing agent is contained in both the aqueous suspension (a) and the nickel ion-containing liquid (b). This makes it possible to easily form a nickel film having excellent adhesion. The reason for this is not clear, but ( By adding a complexing agent to both the aqueous suspension of a) and the nickel ion-containing liquid of (b), nickel ions are stabilized and the reduction reaction is prevented from proceeding rapidly. It is speculated that it is also the power that can be.

[0039] The concentration of the complexing agent in the nickel ion-containing liquid (b) affects the formation of the nickel film in the same manner as the concentration of the complexing agent in the aqueous suspension (a). From this viewpoint 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 Z liter, particularly preferably 0.012 to 8 mol Z liter.

[0040] The reducing agent-containing liquid (c) is generally an aqueous solution of a reducing agent. As the reducing agent, those similar to those used for the reduction of the noble metal ions described above can be used. It is particularly preferable to use sodium hypophosphite. Since the concentration of the reducing agent affects the reduction state of nickel ions, it is preferable to adjust the concentration within the range of 0.1 to 20 mol Z liter, particularly 1 to 10 mol Z liter.

[0041] To the aqueous suspension of (a), two liquids, the nickel ion-containing liquid (b) and the reducing agent-containing liquid (c), are added individually and simultaneously. As a result, nickel ions are reduced, and nickel is deposited on the surface of the core powder to form a film. The addition rate of the nickel ion-containing solution and the reducing agent-containing solution is effective in controlling the nickel deposition rate. The deposition rate of nickel affects the formation of a nickel film with good adhesion. Therefore, it is preferable to control the nickel deposition rate by adjusting the addition rate of both solutions at 1 to: LOOOOnmZ, particularly 5 to 300 nm / hour. The deposition rate of nickel can be obtained by calculation from the addition rate of the nickel ion-containing liquid.

[0042] While 2 solution are添Ka卩aqueous suspension, the load 0. l~15m ² / l, is preferably kept in a range especially of 1 to 10 m ² / liter. As a result, nickel is deposited uniformly. For the same reason, it is also preferable that the load amount is within this range when the addition of the two liquids is completed and the reduction of nickel ions is completed! /.

[0043] Force depending on the type of reducing agent used During the reduction reaction of nickel ions, the pH of the aqueous suspension is kept in the range of 3 to 13, especially 4 to: Force of water insoluble precipitation of nickel This is preferable from the viewpoint of preventing the formation of products. In order to adjust the pH, for example, a predetermined amount of a pH adjusting agent such as sodium hydroxide may be added to the reducing agent-containing solution. [0044] The obtained plating powder is separated after filtration and washing several times. Further, as an additional step, a gold-plated layer forming step as the uppermost layer may be performed on the nickel film. The gold plating layer can be formed according to a conventionally known electroless plating method. For example, to an aqueous suspension of plating powder, add an electroless plating solution containing tetrasodium ethylenediammine tetraacetate, trisodium citrate and potassium cyanate and adjusted to pH with sodium hydroxide. Thus, a gold plating layer is formed on the nickel film. The thickness of the gold plating layer is generally about 0.001 to 0.5 m. The thickness of the gold plating layer can be calculated from the amount of gold ions added and the ability to analyze the ions.

[0045] In this way, a plating powder in which a nickel film is formed on the surface of the core material powder is obtained. The nickel coating on the plated powder has excellent adhesion to the core powder. The thickness of the nickel film has a slight effect on its adhesion and heat resistance. If the film is too thick, the core powder tends to fall off and the conductivity tends to decrease. On the other hand, if the skin is too thin, the desired conductivity cannot be obtained. From these viewpoints, the thickness of the nickel film is preferably about 0.005 to 10 / ζ πι, particularly about 0.01 to 2 / ζ πι. The thickness of the nickel film can be measured, for example, by observation with a scanning electron microscope, and the amount of nickel ion added and the ability to analyze chemistry can also be calculated.

[0046] The plating powder of the present invention obtained by force is used for connecting, for example, an anisotropic conductive film (ACF), a heat seal connector (HSC), and an electrode of a liquid crystal display panel to a circuit board of an LSI chip for driving. It is suitably used for applications such as conductive materials and polarizing plates.

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 the powerful embodiments.

[Example 1 3]

(1) Melamine rosin coating process

Charge 100 parts by weight of the core powder shown in Table 1, 100 parts by weight of water, 3 parts by weight of melamine, and 8 parts by weight of 37% formalin in a four-necked flask with a condenser, and add 5% aqueous sodium carbonate solution with stirring. The pH was adjusted to 9.0. Next, the temperature was raised to 75 ° C, and the reaction was carried out with stirring for 2 hours. After completion of the reaction, it is cooled, filtered, washed with water, and dried under reduced pressure (5 mmHg or less) at 150 ° C for 6 hours. By curing, a core material powder coated with 2.1% by weight of melamine resin was obtained.

[0049] (2) Catalytic treatment process

200 ml of an aqueous stannous chloride solution was added to 200 ml of an aqueous slurry containing 7.5% by weight of the melamine-coated core material powder obtained in the step (1). The concentration of this aqueous solution was filed at 5 X 10- ³ mol / L. The mixture was agitated at room temperature for 5 minutes and subjected to a susceptibility treatment to adsorb tin ions on the surface of the melamine-coated core material powder. Subsequently, the aqueous solution was filtered, repulped once and washed with water. Next, 400 mL of an aqueous slurry containing 3.75% by weight of melamine-coated core material powder was prepared and maintained at 60 ° C. While stirring the slurry using ultrasonic waves, 2 mL of a 0.11 mol g ZL palladium chloride aqueous solution was added. The state of stirring as it was was maintained for 5 minutes, and an active soot treatment was performed to trap palladium ions on the surface of the melamine-coated core powder. Next, the aqueous solution was filtered and washed once with repulp hot water. Next, 200 ml of an aqueous slurry containing 7.5% by weight 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 0.117 mol / liter dimethylamine borane and 0.16 mol Z liter boric acid was added thereto. The palladium ion was reduced by stirring for 2 minutes while using ultrasonic waves at room temperature.

(3) Initial thin film formation process

[0050] 200 mL of an aqueous slurry containing 7.5% by weight of the melamine-coated core powder treated in the step (2) was mixed with 0.087 mol ZL sodium tartrate, 0.005 mol ZL nickel sulfate and 0.012 mol ZL. Sodium hypophosphite was added to the initial thin film forming solution with stirring to form an aqueous suspension. The initial thin film forming liquid was heated to 75 ° C and the liquid volume was 2 L. Immediately after the slurry was charged, hydrogen generation was observed, confirming the start of initial thin film formation.

(4) Electroless plating process

[0051] The aqueous suspension obtained in the initial thin film formation step was mixed with a nickel ion-containing liquid consisting of 0.86 mol ZL of nickel sulfate and 0.17 mol ZL of sodium tartrate and 2.57 mol ZL of hypophosphorous acid. Two solutions, sodium acid and 2.6 mol / L of a reducing agent-containing solution that also has sodium hydroxide strength, were added at an addition rate of 8 mLZ each. The amount of the added solution was adjusted so that the deposited film thickness was 0.2 microns. Hydrogen generation was observed immediately after the addition of the two solutions, confirming the start of the plating reaction. After the addition of two liquids is complete, hydrogen bubbling stops Stirring was continued while maintaining a temperature of 75 ° C. Next, the aqueous suspension was filtered, and the filtrate was washed with repulp three times and dried in a vacuum dryer at 110 ° C. As a result, a plating powder having a nickel lurin alloy plating film was obtained.

[Comparative Example 1 3]

In Examples 1 to 3, plating powder was obtained by the same operation except that the step (1) was not performed.

[Comparative Example 4 6]

In Example 1, except that the step (1) was replaced with the following step (1-1), a plated powder was obtained in the same manner as in Examples 1-3.

(1 1) Process

10 parts by weight of the same styrene resin used in Example 1 was added to 100 parts by weight of an aqueous solution containing 1.0% by weight of the surface treating agent shown in Table 1, and immersed for 1 hour at room temperature. Next, it was dried at 110 ° C. to prepare a core powder coated with the surface treatment agent.

[Comparative Example 7]

In Example 1, a plated powder was obtained in the same manner as in Example 1, except that the step (1) was replaced with the following step (1-2).

(1 2) Process

Chloric anhydride 2.0 mol ZL, sulfuric acid 3.6 mol ZL strength 100 parts by weight of the core powder was charged in 2 L of an etching solution, heated to 70 ° C., and stirred for 10 minutes. Next, filtration and washing were repeated to obtain a core material powder subjected to etching treatment.

[0055] The thickness of the plating film and the adhesion of the plating film were measured and evaluated for the obtained plating powder by the following method. The results are shown in Table 2. The amount of chromium remaining in the plating powder was measured, and the results are also shown in Table 2.

[Thickness of plating film]

The plating powder was immersed in nitric acid to dissolve the adhesive film, the film components were quantified by ICP or chemical analysis, and the thickness was calculated by the following equation.

A = [(r + t) ³ -r ³ ] d / rd

1 2

A = W / 100-W Where r is the radius of the core powder m), t is the thickness of the adhesive film m), and d is the adhesive film.

1

The specific gravity of, d is the specific gravity of the core powder, w is the metal content (% by weight).

2

[0057] [Adhesion of plating film]

2. 2 g of plating powder and 90 g of 3 mm diameter zircoyu beads were placed in a 100 ml mayonnaise bottle. Furthermore, 10 ml of toluene was added to the mayonnaise bottle using a whole pipette. The inside of the mayonnaise bottle was stirred for 10 minutes at 40 Orpm using a stirrer (three-one motor). After the completion, the plating powder and the zircoyu beads were separated. The plated powder was observed with a scanning electron microscope, and the degree of peeling of the plating film was evaluated according to the following criteria. ◯: Peeling of the plating film was not observed.

X: Peeling of the plating film was observed.

[Chromium content]

The plating powder was immersed in nitric acid to dissolve the adhesion film, and further sulfuric acid was added for thermal decomposition. The obtained solution strength was also measured by ICP for chromium.

[0059] [Table 1]

Note) Surface treatment agent 1; γ-Aminopropyltriethoxysilane, surface treatment agent 2; Ν-β (aminoethyl) γ-aminopropyltrimethoxysilane, surface treatment agent 3; γ-metaataryloxypropyltri Methoxysilane

[Table 2]

Note) N. D. indicates that the detection limit is 0.002 mgZg or less.

[0061] As can be seen from the results shown in Table 2, it can be seen that the plating powders of the respective examples (product of the present invention) are excellent in adhesion of the adhesive skin film and are substantially free of chromium. On the other hand, it can be seen that the plating powders of Comparative Examples 1 to 6 do not contain chromium, but are easily peeled off. Further, it can be seen that the plating powder of Comparative Example 7 is excellent in the adhesion of the plating film, but chromium is contained in the plating powder.

Industrial applicability

[0062] According to the present invention, even if chromic acid or permanganic acid is not used for the hydrophilization treatment, the electroconductivity is excellent in plating adhesion even for fine particles having an average particle diameter of 20 μm or less. Electroless plating powder can be obtained. The conductive electroless plating powder of the present invention is used for driving, for example, anisotropic conductive film (ACF), heat seal connector (HSC), and electrodes of liquid crystal display panels. It is suitable for use in conductive materials for connecting LSI chip circuit boards and polarizing plates.

Claims

The scope of the claims

[1] A conductive electroless plating powder characterized in that the surface of the core powder is coated with melamine resin and a metal film is formed by electroless plating.

[2] The conductive electroless plating powder according to [1], wherein the core powder is hydrophobic.

[3] The conductive electroless plating powder according to claim 1 or 2, wherein the average particle diameter of the core powder is 0.5 to LOO μm.

[4] The conductive electroless powder according to claim 1 or 2, wherein the core material powder has an average particle size of 1 to 20 μm.

[5] The conductive electroless plating powder according to any one of claims 1 to 4, wherein a spherical powder is used as the core powder.

[6] A step of contacting a core material powder with an initial condensate of melamine resin to carry out a polymerization reaction of the initial condensate to obtain a core material powder coated with melamine resin; A step of supporting a noble metal on the surface of the core powder coated with fat, and a step of subjecting the core powder supporting the noble metal to an electroless plating process in the next step. A method for producing electrolytic plating powder.