JP3417699B2 - Conductive electroless plating powder - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electroless plating powder capable of imparting excellent dispersibility and high electroconductivity when blended in various matrix materials, especially in a plastic material for electronic equipment. The present invention relates to a conductive electroless plated powder suitable for electrically connecting minute parts of a class.

[0002]

2. Description of the Related Art Plastic materials with conductivity are
It is widely used as a member for preventing static electricity, absorbing electric waves, shielding electromagnetic waves, etc. of electronic devices and their parts. As a method for imparting conductivity to a plastic material, conventionally, a means for dispersing and compositing a fine powdery conductive filler in a matrix resin component has been the main technique, and for the conductive filler, for example, Cu, Fe, or Ni is used. In general, powder-based materials, metal-based materials such as fibers or foil pieces, carbon-based materials such as graphite powder, carbon black, and carbon fiber chops are commonly used.
In addition, titanium dioxide pigment as the colorable conductive filler is coated with stannic oxide on the substrate surface (Japanese Patent Publication No.
58-39175) and those coated with stannic oxide and antimony (Japanese Patent Laid-Open No. 56-41603) are known, and moreover, as a transparent conductive filler on the particle surface of a titanium dioxide base material. Conductive titanium dioxide powder provided with a coating layer of tin oxide and antimony oxide in a specific ratio (Japanese Patent Laid-Open No. 61-
No. 141616) has been proposed.

Recently, the connection between the electrodes of the liquid crystal display panel and the driving LSI, the connection of the LSI chip to the circuit board,
In addition, a plastic material with conductivity is used as a conductive material for electrically connecting minute parts of electronic equipment such as connection between electrode terminals with a fine pitch, but it is particularly advanced and reproducible for these purposes. Conductive performance with good properties is required. Therefore, the conductive plastic material according to the above-mentioned conventional technique cannot secure the conductive performance and dispersibility that sufficiently satisfy the required characteristics, and there is a problem that it is not possible to cope with it. The applicant of the present invention has previously found that a conductive filler composed of an electroless plating powder in which fine metal particles are previously deposited as a dense and substantially continuous film on the surface of an organic or inorganic substrate by an electroless plating method (Japanese Unexamined Patent Application Publication No. Hei 1 (Kokai) 1). -242782 publication)
However, when the electroless plating film of the electroless plating powder is made of Ni, Ag, Au, etc., it is possible to impart excellent high conductivity performance satisfying the strict requirements for the above-mentioned special electronic device applications. It will be possible.

[0004]

However, Japanese Patent Laid-Open No. 1-
The electroless plating powder described in Japanese Patent No. 242782 has a drawback that base particles are aggregated with each other during the electroless plating process, and as the film thickness of the metal plating layer is increased, the agglomeration becomes large and becomes strong and the dispersibility is impaired. Since the dispersibility of the conductive powder has a great influence on the conductive performance when mixed with the plastics material, reproducible high conductive performance cannot be expected unless the backward dispersion phenomenon is eliminated.

The inventors of the present invention have made extensive studies on such unsolved problems. As a result, when a Ni or Ni-Au electrolytic plating film is formed by using hard spherical carbon fine particles as a base material for electroless plating, electroless plating is performed. The phenomenon that the base particles do not agglomerate with each other during the plating process does not occur, and the conductive performance is further effectively improved by selectively using the spherical carbon fine particles having a specific particle size, the surface of which has a fine uneven rough surface. I confirmed the facts.

The present invention was developed on the basis of the above-mentioned findings, and an object of the present invention is to provide a conductive electroless plating which can always impart excellent dispersibility and high conductivity to a target matrix component. To provide powder.

[0007]

Means for Solving the Problems In order to achieve the above object, the electroless electroless plated powder according to the present invention has a skeleton made of glassy carbon, and other carbon fine particles are integrally attached to the surface layer part. The formed spherical carbon particles having an average particle size of 1 to 50 μm having a rough surface with fine irregularities are used as a base material, and a Ni coating or Ni-A is formed on the surface of the base material by electroless plating.
The constitutional feature is that a multi-layered film of u is formed.

The first requirement of the present invention is that spherical carbon particles having an average particle diameter of 1 to 100 μm are selected as the electroless plating base material having glassy carbon as a skeleton and a finely rough surface on the surface layer thereof. is there. This base material is a spherical carbon fine particle having a special property in which other carbon fine particles are integrally attached to the surface of the spherical glassy carbon fine particle to form a fine uneven rough surface on the surface layer portion.

The above-mentioned base material is, for example, spherical particles of a resin having a high carbonization residual rate which is converted into glassy carbon by carbonization treatment and fine particles of bulk mesophase pitch having a particle diameter of 10 μm or less are dry-mixed to the spherical particle surface. After depositing bulk mesophase pitch, 250 ~ 3 in oxidizing atmosphere
A method of performing heat stabilization treatment in a temperature range of 50 ° C., followed by firing carbonization and / or graphitization in a non-oxidizing atmosphere, or spherical particles of the same resins as above and carbon black,
Graphite powder, coke powder, etc. are dry-mixed to adhere these carbonaceous substances to the spherical particle surfaces, and then heat-stabilized in a temperature range of 100 to 400 ° C. in an oxidizing atmosphere, and then similarly non-oxidizing. It can be produced by a method of firing carbonization and / or graphitization in an atmosphere. As a resin with a high carbonization residual rate that is converted to glassy carbon of the skeleton,
Phenolic resin, naphthalene resin, furan resin,
One kind or a mixture of two or more kinds of divinylbenzene polymer, styrene-divinylbenzene polymer and the like is used. According to such a manufacturing method, spherical particles of a resin as a core material in the carbonization process are converted into hard glassy carbon to form a skeleton, and the bulk mesophase pitch and the carbonaceous substance attached to the spherical particle surface are soft. It becomes carbon fine particles and adheres integrally to the surface of the skeleton portion, and is formed as a fine uneven rough surface on the surface layer portion.

As the spherical carbon particles for a substrate having such a unique grain property, those having an average particle size of 1 to 50 μm, preferably 10 to 30 μm are used. It is practically impossible to obtain fine particles having an average particle size of less than 1 μm, and if the average particle size exceeds 50 μm, the specific surface area becomes small, which causes a decrease in conductivity. This adjustment of the particle size can be easily performed by classifying the particle size of the spherical fine particles serving as the skeleton in advance within a certain range in consideration of the carbonization shrinkage of the resins.

The second requirement of the present invention is that a Ni coating or a Ni-Au multi-layer coating is formed on the surface of the substrate by electroless plating. The Ni coating coats the Ni plating layer firmly with the spherical carbon substrate to form an excellent conductive coating, and when forming a Ni-Au multi-layer coating, is good as the upper Au coating. This is because it effectively functions as an intermediate layer that secures excellent adhesion. In addition, Ni-
The Au multilayer coating is used because the conductivity can be further improved as compared with the Ni single coating. Therefore, whether to form a Ni single-layer coating or a Ni-Au multilayer coating may be appropriately determined depending on the purpose of use. The preferred thickness of the electroless plating layer to be formed is 1 Ni film
The range is 0 to 200 nm and the Au coating is 10 to 50 nm.

The conductive electroless plated powder according to the present invention is
The skeleton is made of glassy carbon, and the surface layer has a micro-roughened rough surface due to other carbon particles.
Of the spherical carbon particles as a base material, and after capturing palladium ions on the surface of the base material, a catalytic treatment step of reducing the palladium ions to support palladium on the surface of the base material, and a base material subjected to the catalytic treatment It can be manufactured by adding a complexing agent to the above aqueous slurry to sufficiently disperse it, and then performing an electroless plating step of separately adding at least two Ni electroless plating solutions to form a Ni coating film. In addition, Ni-
To form the Au multi-layer coating, the electroless plating of Au is performed on the base material on which the Ni coating is formed in the above step,
A method of coating the upper surface of the plating layer with an Au film is adopted.

The specific means of the electroless plating method is as follows. First, a modification treatment for imparting a catalyst capturing ability to the surface of the spherical carbon particles as the base material is performed. The catalyst scavenging ability is a function by which the surface of the base material can capture palladium ions as a chelate or a salt in the catalysis treatment step, and the modification can be carried out according to the method described in JP-A-61-64882. For the purpose of the present invention, it is preferable to apply a substrate whose surface is treated with an epoxy resin which is cured by an amino group-substituted organosilane coupling agent or an amine curing agent.

In the catalysis treatment step, the base material provided with the ability to capture the catalyst by the reforming is sufficiently dispersed in a dilute acidic aqueous solution of palladium chloride to capture the palladium ion on the surface, and then the captured palladium ion. Is subjected to a reduction treatment to support palladium on the surface of the base material particles. At this time, the concentration of the palladium chloride aqueous solution is 0.05
The reducing agent is sodium hypophosphite, sodium borohydride, potassium borohydride,
Dimethylamine borane, hydrazine or formalin are used. The amount of the reducing agent added varies depending on the particle size of the base material, but is generally in the range of 0.01 to 10 g / l with respect to the aqueous solution.

In the electroless plating step, the base particles which have been subjected to the catalytic treatment as the first step are dispersed in water sufficiently uniformly, and the dispersion concentration is 2-500 g / l, preferably 5-300 g / l aqueous slurry. To prepare. The dispersion operation can be carried out by ordinary stirring, high-speed stirring, or a shearing dispersion device such as a colloid mill or a homogenizer. Then, a complexing agent is added to the aqueous slurry to sufficiently disperse it. Examples of complexing agents include citric acid, hydroxyacetic acid, tartaric acid,
Malic acid, lactic acid, carboxylic acid (salt) such as gluconic acid or its alkali metal salts and ammonium salts, amino acids such as glycine, amine acids such as ethylenediamine and alkylamines, other ammonium, EDTA, pyrophosphoric acid (salt), etc. At least one compound having a complexing effect on Ni ions is used. The complexing agent is usually added in the form of an aqueous solution, but its concentration is set in the range of 1 to 100 g / l, preferably 5 to 50 g / l. The preferred pH of the aqueous slurry at this stage is in the range 4-14.

In the aqueous slurry thus prepared,
At least two aqueous solutions of nickel salt, sodium hypophosphite and sodium hydroxide are used as the electroless plating solution.
The electroless plating reaction is performed by separately and simultaneously adding as a liquid. When the electroless plating solution is added to the aqueous slurry, the plating reaction immediately starts, but the Ni coating formed can be controlled to have a desired film thickness by adjusting the addition amount. After the completion of addition of the electroless plating solution, stirring is continued while maintaining the solution temperature for a while after the generation of hydrogen gas is not completely observed, and the reaction is completed.

The Ni film is formed as a dense and continuous thin film by the above steps, and the electroless Au film is further formed on the surface of the Ni film.
N that has better conductivity by plating
A multi-layer coating of i-Au can be formed. The formation of the Au coating is carried out by using EDTA-4N
a, citric acid-2Na and potassium gold cyanide, which are added to a heated electroless plating solution whose pH is adjusted to a weakly acidic region with an aqueous sodium hydroxide solution with stirring to perform plating treatment, and then gold cyanide Potassium, EDTA-4
This is performed by an operation of separately adding a mixed aqueous solution of Na and citric acid-2Na and a mixed aqueous solution of potassium borohydride and sodium hydroxide to cause a plating reaction.

[0018]

The conductive electroless plated powder of the present invention has an average particle size having a fine rugged rough surface formed of glassy carbon as a base material and other carbon fine particles integrally attached to the surface layer. It is characterized by a unique composite structure in which spherical carbon particles of 1 to 50 μm are selectively used and a Ni single coating or a Ni-Au multilayer coating is formed on the surface of this substrate by electroless plating. In this composite structure, the glassy carbon that constitutes the base material skeleton is extremely hard, so it does not break due to the load of external force during compounding or other operation processes, and it intervenes on the surface as a micro-roughened rough surface. Since the carbon fine particles are integrally attached to the skeleton portion, they are not easily removed.

The conductive electroless plated powder of the present invention exhibits excellent conductive performance because it has high conductivity of Ni alone or N.
It is presumed that the surface layer portion coated with the i-Au multilayer has a finely roughened rough surface, and the particles come into contact with each other in a state close to surface contact. In addition, because the carbon fine particles on the micro-roughened rough surface are soft, they are deformed when a load is applied to further increase the contact area between the particles, which also causes a decrease in contact resistance. In addition, the reason why the dispersibility is improved is that the carbon particles that are the base material are essentially inert and have appropriate lubricity, and this material property is a good fluidizing action of the substantially spherical particle shape. This is because, in combination with this, it effectively functions to prevent a phenomenon in which the base particles are aggregated with each other during the electroless plating process. Through such a unique action, it is possible to always mix the matrix material with good dispersibility and to impart high conductivity performance.

[0020]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples.

Examples 1 to 4 (1) Production of base material; commercially available spherical phenol resin and particle size 3 μm
Coal-based bulk mesophase pitch fine powder having a particle size of m or less was dry-mixed sufficiently uniformly, and the bulk mesophase fine powder was uniformly adhered to the surface of the spherical phenol resin particles. After heat-stabilizing these particles in air at a temperature of 280 ° C., they are carbonized at a temperature of 1000 ° C. in a firing furnace maintained in a nitrogen atmosphere, and the skeleton is made of glassy carbon, and the surface layer part is formed. Spherical carbon particles having fine irregularities rough surface formed by integrally adhering pitch carbonized fine particles were obtained. The spherical carbon particles have an average particle size of 19.0 μm and a bulk density of 0.8 to
It had a property of 0.9 g / cc and a true specific gravity of 1.40 to 1.56.

(2) Ni electroless plating treatment; 10 g of the above-mentioned base material particles was added to a conditioner solution [made by Shipley, "Cleaner conditioner 231"] 40 ml / l aqueous solution 20.
The mixture was added to 0 ml with stirring, followed by stirring for 5 minutes for surface modification. The aqueous solution was filtered and washed once with repulp water, and the base particles were washed with 1 g / l stannous chloride aqueous solution at room temperature 200
It was immersed in ml for 5 minutes, filtered, washed and sensitized.
Then 0.1 g / l palladium chloride solution and 0.1
200 ml of a catalyzed liquid consisting of ml / l hydrochloric acid was added with stirring, followed by stirring for 5 minutes to capture palladium ions. The aqueous solution was filtered, and the base material powder washed once with repulp water was immersed in a 1 g / l aqueous solution of sodium hypophosphite at room temperature for 5 minutes for reduction treatment to support palladium on the surface of the base material. The base material was added to each complexing agent aqueous solution shown in Table 1 heated to a temperature of 65 ° C. with stirring and sufficiently dispersed by stirring to prepare an aqueous slurry, and then 3 g of sodium hypophosphite was added to each aqueous slurry. It was charged and dissolved by stirring.

[0023]

[Table 1]

When sodium hypophosphite was added, foaming soon started with the generation of hydrogen gas, but when the foaming stopped for a while, the Ni electroless plating solution shown in Table 2 was used.
Separately, the liquid and the liquid b were added at the same time with stirring at an addition rate of 5 ml / min while stirring 80 ml each.

[0025]

[Table 2]

After the total amount of the Ni electroless plating solution was added, stirring was continued while maintaining the temperature of 65 ° C. until the bubbling of hydrogen stopped. Then, the plating solution was filtered, the filtered product was repulped three times, and then dried at 100 ° C. in a vacuum dryer to obtain a powder having a Ni coating. All the filtrates after the plating reaction were colorless and transparent, and it was confirmed that the supplied plating solution was completely consumed in the plating reaction. When the obtained Ni electroless plated particles were observed with an electron microscope,
It was confirmed that all of them were spherical particles having a uniform and smooth coating layer of fine Ni metal particles, and that the plating film was formed as a dense and substantially continuous film.

(3) Au electroless plating treatment: 10.0 g of the Ni electroless plated particles obtained in the above step was added to EDTA.
-4Na (10g / l), citric acid-2Na (10g / l) and potassium gold cyanide (3.0g / l, 2.1g / l as Au) composition adjusted to pH 6 with aqueous sodium hydroxide It was added to the electroless plating solution (solution A) at 60 ° C. with stirring and subjected to Au plating treatment for 10 minutes. Then, potassium gold cyanide (10 g / l, 6.8 g / l as Au), EDTA-4
Mixed aqueous solution of Na (10g / l) and citric acid-2Na (10g / l) (liquid B), mixed aqueous solution of potassium borohydride (30g / l), sodium hydroxide (60g / l) (liquid C) ) Was added individually and simultaneously for 20 minutes through the feed pump. The amounts of A liquid, B liquid and C liquid at this time were set to the amounts shown in Table 3.

[0028]

[Table 3]

Subsequently, the liquid is filtered, and the filtered material is repulped and washed three times, and then dried at a temperature of 100 ° C. by a hot air dryer to subject the Ni coating to Au electroless plating treatment, and the base material surface is treated with Ni. A multi-layer coating of Au was formed.

(4) Evaluation of physical properties; average particle diameter of the electroless electroless plated powder thus obtained, film thickness and electroconductivity of Ni coating film after Ni electroless plating treatment, after Au electroless plating treatment The film thickness and conductivity of the Ni-Au multilayer coating film were measured and evaluated, and the results are shown in Table 4. The plating film thickness was calculated by the following formula. Where r is the radius of the base material particles (μm) and t is the plating film thickness (μm)
m), d ₁ is the specific gravity of the plating film, and d ₂ is the specific gravity of the base material particles.
The conductivity was evaluated by placing 1.5 g of the plating powder in a vertically standing resin cylinder having an inner diameter of 10 mm and measuring the electrical resistance between the upper and lower electrodes under a load of 5 kg. For comparison, the properties of the spherical carbon particles having a micro-roughened rough surface used for the base material are also shown in Table 4 (Comparative Example 1).

1 and 2 show Ni-A according to the first embodiment.
It is an electron microscope (SEM) photograph of a conductive electroless plated powder on which a u multilayer coating is formed. From these figures, it is recognized that the state of the powder is such that the plating layer has a rough surface with fine irregularities along the surface layer of the base material.

Comparative Example 2 Commercially available spherical phenol resin (average particle size 14
(μm) is heat-stabilized in air at a temperature of 280 ° C. and then heated in a nitrogen atmosphere at 100 ° C. in a firing furnace.
Carbonization treatment was performed at a temperature of 0 ° C. to obtain truly spherical carbon particles which were entirely composed of glassy carbon and had a smooth surface. Its properties are an average particle size of 10 μm and a bulk density of 0.8-0.
The true specific gravity was 9 g / cc and 1.35 to 1.40. The base material was subjected to Ni electroless plating under the same conditions as in Example 1, and further subjected to Au electroless plating as an upper layer. The properties of the obtained electroless plated powder were measured and evaluated, and are also shown in Table 4.

[0033]

[Table 4] [Table Note] The electric resistance value of Comparative Example 1 is a measured value of the base material itself.

As shown in Table 4, the conductivity of the example products satisfying the requirements of the present invention is superior to that of the comparative example, and particularly N
It can be seen that the i-Au multi-layer plated product exhibits a high degree of electrical conductivity. It was also found that the electroless plated powders of the examples did not aggregate during the electroless plating process and were easily dispersed uniformly when dispersed in the resin.

[0035]

As described above, according to the present invention, a spherical carbon fine particle having a skeleton made of glassy carbon and a surface layer portion integrally covered with other carbon fine particles and having a minute uneven rough surface is used as a base material. It is possible to provide an electroless plated powder having excellent dispersibility and conductive performance in which fine metal particles of Ni or Ni-Au are densely formed on the surface as a substantially continuous film. Therefore, as a conductive filler that imparts conductivity to a plastic material or the like, connection between electrodes of a liquid crystal display panel and a driving LSI, L
It is expected to be extremely useful as a conductive material for connecting an SI chip to a circuit board and other connection between electrode terminals having a fine pitch.

[Brief description of drawings]

1 is an electron microscope enlarged photograph (magnification: 500 times) showing a particle structure of a conductive electroless plated powder according to Example 1. FIG.

FIG. 2 is an electron microscope enlarged photograph (magnification: 2000 times) showing a particle structure of a conductive electroless plated powder according to Example 1.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C23C 18/31 H01B 1/00

Claims (2)

(57) [Claims] 1. A spherical carbon particle having an average particle diameter of 1 to 50 μm, which has a skeleton made of glassy carbon and has fine irregularities and rough surfaces formed by integrally adhering other carbon particles to the surface layer, as a base material, N on the surface of the base material by electroless plating
A conductive electroless plated powder characterized by being formed with an i coating. 2. A spherical carbon fine particle having an average particle size of 1 to 50 μm having a skeleton made of glassy carbon and having a fine uneven rough surface formed by integrally adhering other carbon fine particles to the surface layer, as a base material, A conductive electroless plated powder, comprising a Ni-Au multilayer coating formed on the surface of the base material by an electroless plating method.