JPH10101962A - Electroconductive electrolessly plated powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroconductive electrolessly plated powder which is scarcely deteriorated in electric conductivity after being aged according to the humidity resistance test. SOLUTION: This powder is prepared by applying 0.03-65wt.%, based on the core particle, gold or palladium to the outermost surface of a core particle comprising a metallic particle, desirably a nickel particle and having a mean particle diameter of 1-50μm by the electroless plating process. It has an aspect ratio of 2 or below, an electric resistance of 0.1Ω.cm or below after being aged for 500hr and a variation rate of resistance Ωv=|Ωa-Ωb|/Ωa<=20 (wherein Ωa is the electric resistance before the aging test, and Ωb is that after the test).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless electroless plating powder having excellent moisture resistance, which is dispersed and blended in a plastic material to electrically connect minute parts of electronic equipment. Excellent heat resistance suitable for purposes such as conductive film) and HSC (heat seal connector),
The present invention relates to a conductive electroless plating powder that imparts dispersibility, adhesion, and high conductivity.

[0002]

2. Description of the Related Art Plastics materials provided with conductivity are widely used for members for preventing static electricity, absorbing radio waves or shielding electromagnetic waves of electronic devices and parts. As a method for imparting conductivity to a plastic material, there is a means for dispersing and complexing a fine powdered conductive filler into a matrix resin component. Examples of such conductive fillers include carbon powders such as carbon powder, carbon fiber, and carbon flake; metal powders such as Ag, Ni, Cu, Zn, Al, and stainless steel; and metal powders such as metal flake and metal fiber; ₂ (Sb-doped), in ₂ O ₃ (Sn-doped), ZnO (Al-doped) fine particles of a metal oxide such as, mica, glass beads, glass fibers, whiskers such as carbon fiber, potassium titanate, barium sulfate, There is known a system in which a base filler such as zinc oxide or titanium oxide is conductively coated by electroless plating, vacuum deposition, or the like.

[0003] In addition, antimony is doped on the surface of a white powder base material such as titanium dioxide, silica, mica, silicate, alumina, barium sulfate, etc., which is made conductive by electroless plating. (See JP-A-56-41603, JP-A-62-181371, JP-A-2-218768, JP-A-5-116930, and JP-A-7-50)
No. 8491), a flat or scaly fine powder of base metal particles such as stainless steel or nickel coated with a noble metal such as palladium or gold (Japanese Patent Laid-Open No. 2-66101), and two layers on the surface of the base metal particles. Those coated with the different noble metals described above so that the surface layer becomes palladium (JP-A-60-233166) and those coated with inorganic powder (JP-A-60-181294, JP-A-60-181294, 59-
182961), those obtained by plating various inorganic or organic base materials (Japanese Patent Application Laid-Open No. 1-224282), and those obtained by applying metal plating to special resin particles such as benzoguanamine and styrene (Japanese Patent Application Laid-Open No. No. 49632, JP-A-60-12603) and the like have been proposed.

Further, the above-mentioned conductive material is used as a conductive material for electrically connecting minute parts of electronic equipment, such as connection between electrodes of a liquid crystal display panel and a circuit board of a driving LSI chip, and connection between electrode terminals of a fine pitch. Plastic materials provided with conductivity by such conductive fillers are used, but for these purposes, particularly high conductive properties with good reproducibility are required.

In addition, TAB (Tape Automated)
electrodes (attached bonding) and PCB (P
Conventionally, the connection with the printed circuit board (printed circuit board) is performed by soldering, but other connection methods have been demanded in view of an increase in connection density and environmental problems related to soldering. Although the input side has a lower connection resistance than the output side, a stable connection with a low resistance is required to operate the IC stably. In addition, since a larger current flows than the output side, there is a problem in that heat is usually larger than the radiation amount, the connection is heated, and the connection resistance is increased.

[0006]

When used in such a high voltage area as described above, there is a drawback that the particle surface of the core material is oxidized and the conductivity is reduced, and the demand cannot be sufficiently satisfied. The present inventors have made extensive studies on such unresolved issues, and as a result, for example, ACF and HSC
As for conductive particles used in places with high conductive performance and high operating voltage, specific particles in which the surface of the core material particles are coated with gold or palladium by electroless plating are highly conductive to matrix components. The present inventors have found that the present invention exhibits high performance and high thermal reliability, and have completed the present invention.

[0007]

That is, according to the present invention, gold or palladium is applied to the outermost surface layer of the core material particles having an average particle size of 1 to 50 μm by electroless plating with respect to the core material particles.
In a conductive electroless plating powder coated with 3 to 65 wt%, the length ratio of the length and width is 2 or less, and the electric resistance after an aging test for 500 hours is 0.1 Ω · cm or less, and The resistance change rate Ωv = | Ωa−Ωb | / Ω
a ≦ 20 (where Ωa is the electrical resistance before the aging test,
Ωb indicates the electric resistance after the aging test. The present invention provides a conductive electroless plating powder characterized in that:

In the present invention, the core particles are preferably metal particles, and the metal particles are preferably nickel particles. Further, as the nickel particles, nickel particles having fine irregularities on the surface are preferable. Further, the core material particles may be previously coated with at least one layer of a conductive metal.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Core material particles applicable in the present invention, metal and inorganic,
Organic powder, including all materials that can be electrolessly plated. These may be either natural products or synthetic products.

With respect to such core material particles, for example, as the metal powder, nickel, copper, iron and the like or alloys thereof can be mentioned.

The inorganic powder includes glass, ceramics, metal oxides, metal hydroxides, metal silicates including aluminosilicates, metal carbonates, metal nitrides, metal sulfates, metal phosphates, metal phosphates, and the like. Sulfides, metal salts, metal halides or carbon.

Organic powders include natural fibers, natural resins, polyethylene, polypropylene, polyvinyl chloride,
Polystyrene, polybutene, polyamide, polyacrylate, polyacrylonitrile, polyacetal,
Thermoplastic resins such as ionomers, polyesters, etc., alkyd resins, phenolic resins, urea resins, melamine resins, xylylene resins, silicone resins, epoxy resins or diaryl phthalate resins, or their binary or ternary resins Based copolymer resins.

When used for ACF or HSC, metal particles, particularly nickel particles, are preferred. It is preferable that the nickel particles have a large specific surface area due to minute irregularities in their surface shape, and a large specific surface area in order to increase a connection area in order to flow a high current.

The particle diameter of the core particles is not particularly limited, but is 1 to 50 μm, preferably 4 to 20 μm in average particle diameter. The reason for this is that a material having a sharp particle size distribution cannot be obtained for a material outside this range, and there is no necessity for industrial production from the viewpoint of practical use.

The feature of the electroless electroless plating powder according to the present invention is that the core material particles are used as they are, or the core material particles are electrolessly plated by nickel, silver, iron, palladium or other metal having good conductivity. To at least one coated
The outermost layer is coated with gold or palladium.

Next, the feature of the electroless electroless plating powder of the present invention is that the length-to-width ratio of the particles is 2 or less, preferably 1.
It is desirably 7 or less. In the case of flat or scaly particles having a length ratio of more than 2, when used in applications such as ACF and HSC, the particles are likely to come into contact with each other and become conductive, which is not preferable.

Next, the conductive electroless plating powder of the present invention is characterized in that the particles have an electric resistance of 0.1 Ω · cm or less after an aging test for 500 hours and a resistance change rate Ωv = | Ωa−Ωb | / Ωa ≦ 20.

Here, the aging test for 500 hours means that the electroless electroless plating powder is heated at 60 ° C. and 9 ° C. in a constant temperature and high humidity bath.
This is the electric resistance after being left for 500 hours under the condition of 5% RH. The resistance change rate Ωv is a value obtained by dividing the absolute value of the difference between the electric resistance Ωa before the aging test and the electric resistance Ωb after the aging test by the electric resistance before the aging test.

The electric resistance after the test is 0.1 Ω ·
cm, the durability as conductive particles is lacking, and in many cases, the surface of such particles is oxidized,
It is not preferable because the performance as the conductive performance is deteriorated.

In particular, the rate of change in electric resistance Ωv after the aging test needs to be 20 or less. The reason for this is
This is because the above-mentioned functional conductive material for precision electronic materials needs to have long-term stable conductivity under an atmosphere of use environment, and if it is less than this value, sufficient reliability can be obtained.

If the rate of change in resistance Ωv after the aging test for 5000 hours exceeds 20, the particle surface may not be densely and continuously coated with a metal,
In many cases, there is a problem in the plating coating treatment, and it is not suitable as a functional conductive material.

All electroless plating reactions based on reactions such as substitution, chemical reduction, and disproportionation reaction can be applied to the metal coating by the electroless plating method. Since such a metal plating coating is coated in tight contact with the core material particles and forms an electroless plating layer having good peel resistance,
The above effects can be provided.

In the present invention, the coating amount of gold or palladium coated on the outermost surface layer of the core material particles depends on the purpose of use, the core material,
Depending on the coating metal, etc., 0.0
3 to 65 wt%, preferably 0.3 to 15 wt%
It is. Further, such a metal film thickness is 10 to 1000 °, preferably 50 to 500 °.

The electroless electroless plating powder according to the present invention is extremely useful especially for an anisotropic conductive film (ACF), a heat seal connector (HSC) and the like. Normal,
ACF is mainly used for liquid crystal panel (LCD) or TCP (T
ape Carrier Package) and FPC
(Flexible Printed Circuit
t).

[0025] The heat seal connector has a thermocompression resin silver carbon ink conductive line on a polyester film, and the surface thereof is covered with a thermoplastic synthetic rubber adhesive having conductive particles. It is. The method is used in a method in which the heat-sealing agent application surface is positioned on each of the electrodes to be connected, pressed and fixed by heating.

The conductive material comprising the electroless electroless plating powder of the present invention, in which the metal particles are used as core material particles, exhibits high conductivity and high thermal reliability with respect to the matrix component in the above-mentioned applications, and exhibits excellent performance. It is shown.

In order to obtain such a conductive electroless plating powder, a complexing agent is added to an aqueous slurry of core material particles and sufficiently dispersed, and then at least two kinds of chemicals constituting a metal electroless plating solution are added. And performing an electroless plating step of forming a metal coating. Alternatively, an electroless plating step may be performed in which a core material particle is put into an electroless plating bath prepared by dissolving a pre-configured chemical and adjusting to a desired pH to form a metal film.

The specific means of the electroless plating method is performed as follows. The nickel particles are sufficiently uniformly dispersed in water, and the dispersion concentration is 2 to 500 g / l, preferably 5 to 300 g / l.
A g / l aqueous slurry is prepared. The dispersing operation can be usually performed by stirring, high-speed stirring, or a shearing dispersing device such as a colloid mill or a homogenizer. Next, a complexing agent is added to the aqueous slurry and sufficiently dispersed. Examples of complexing agents include carboxylic acids (salts) such as citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid or alkali metal salts or ammonium salts thereof,
Amino acids such as glycine, amine acids such as ethylenediamine and alkylamine, other ammonium, EDT
At least one compound having a complexing effect on metal ions, such as A or pyrophosphoric acid (salt), is used. The complexing agent is usually added in the form of an aqueous solution.
It is set in the range of 100 g / l, preferably 5 to 50 g / l. The preferred pH of the aqueous slurry at this stage is 4
~ 14.

[0029] The aqueous slurry thus prepared is
As an electroless plating solution, for example, potassium gold cyanide,
The electroless plating reaction is performed by adding each aqueous solution of a plating metal salt such as palladium chloride, a reducing agent such as borohydride and sodium hypophosphite, and a pH adjusting agent such as sodium hydroxide.

In the electroless plating method, nickel particles may be added to the electroless plating bath, which is the reverse of the electroless plating method. Through the above steps, the metal film is formed as a dense and continuous thin film. Hereafter, it is collected as a product by post-processing in a conventional manner.

The conductive electroless plating powder coated with the metal film by the electroless plating method as described above has a coating metal layer formed as a dense and continuous thin film. The particle size is slightly larger than that of the particle base material, and does not substantially change the particle size distribution and the like.

The conductive electroless plating powder of the present invention is used for ACF, HSC, etc., and such ACF, HSC, etc. are roughly classified into a type using a thermoplastic resin and a thermosetting resin as an adhesive. For example, Japanese Patent Application No. 59-120436
Gazette, Japanese Patent Application No. 60-191228, Japanese Patent Application No. 60-191228,
-274394, Japanese Patent Application No. 61-287974, Japanese Patent Application No. 62-244142, Japanese Patent Application No. 63-1.
No. 53534, Japanese Patent Application No. 63-305591,
Japanese Patent Application No. 64-47084, Japanese Patent Application No. 64-8187
No. 8, Japanese Patent Application No. 1-4649, Japanese Patent Application No. 1-2
It can be prepared based on known methods described in Japanese Patent Application No. 51787, Japanese Patent Application No. 1-261478, Japanese Patent Application No. 5-32799, and the like.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

Examples 1 to 3 Nickel particles 10 having a true specific gravity of 8.9, an average particle diameter of 9.0 μm, an aspect ratio of 1.1 and a particle surface having fine irregularities.
0 g was stirred in an aqueous solution of hydrochloric acid 50 ml / l for 5 minutes. This was filtered, and the nickel powder washed once with repulping water was mixed with EDTA-4Na (10 g / l) and citric acid-2N.
a (10 g / l) was added to 1 liter of a mixed aqueous solution having a temperature of 60 ° C. and adjusted to pH 6 with stirring. Then, potassium gold cyanide (10 g / 1, 6.8 g / l as Au), EDTA-4Na (10 g / l)
And a mixed aqueous solution (liquid A) of citric acid-2Na (10 g / l) and a mixed aqueous solution (liquid B) of potassium borohydride (30 g / l) and sodium hydroxide (60 g / l) were individually and separately passed through a liquid sending pump. It was added at the same time for 20 minutes.
At this time, the liquid A amount and the liquid B amount were set to the amounts shown in Table 1.

[0035]

[Table 1]

Subsequently, the solution was filtered, and the filtrate was washed three times with repulping, dried at a temperature of 100 ° C. with a hot air drier, and subjected to electroless plating coating on nickel powder to form a gold coating on the particle surface. Formed.

Examples 4-5 Nickel particles 10 having a true specific gravity of 8.9, an average particle diameter of 10 μm, and a vertical / horizontal length ratio of 1.2 and having fine irregularities on the particle surface.
0 g was stirred in an aqueous solution of hydrochloric acid 50 ml / l for 5 minutes. This was filtered, and the nickel powder washed once with repulping water was added to palladium chloride (1.77 g / l), ethylenediamine (4.81 g / l), and sodium hypophosphite (6.36 g / l).
1 and 20 mg / l of thioglycolic acid, which were added with stirring to an electroless plating solution at a solution temperature of 60 ° C. adjusted to pH 8 with hydrochloric acid, and subjected to a plating treatment for 30 minutes. Table 2 shows the electroless palladium plating solution at this time.

[0038]

[Table 2]

Subsequently, the solution was filtered, and the filtrate was washed three times with repulping, dried at a temperature of 100 ° C. with a hot air drier, and subjected to electroless plating coating on nickel powder to form a gold coating on the particle surface. Formed.

The gold and palladium coating amounts were measured by
The obtained plating powder was dissolved in aqua regia and quantified by ICP and chemical analysis. The conductivity (electric resistance) 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 electric resistance between the upper and lower electrodes under a load of 5 kg. Was.

Example 6 A styrene resin having a true specific gravity of 1.05, an average particle diameter of 3.0 μm, and an aspect ratio of 1.01 was coated with Ni plating by an electroless plating method using a core material. Gold coating was performed in the same manner as described above. The results are shown in Table 3.

Example 7 Ni plating was performed using a benzoguanamine resin having a true specific gravity of 1.40, an average particle diameter of 4.6 μm, and an aspect ratio of 1.0 as a core material, followed by coating with Ni. Gold coating was performed in a suitable manner. The results are shown in Table 3.

Comparative Examples 1-2 For comparison, a nickel powder (Comparative Example 1) used for the core material of Examples 1-3 and a nickel powder obtained by reducing the nickel powder to improve its electrical properties ( Table 3 also shows Comparative Example 2).

Comparative Example 3 500 g of the core material particles of Example 1 were pretreated under the same conditions as in Example 1, and then mixed aqueous solution 1 of Example 1 with the same composition was prepared.
It was charged into a liter with stirring. Next, 15 ml each of solution A and solution B having the same composition as in Example 1 were added separately and simultaneously for 5 minutes through a liquid sending pump. The plating solution was filtered, and the filtrate was washed three times with repulping.
Dry at a temperature of 00 ° C. The plating film thus obtained was analyzed in the same manner as in Example 1, and is shown in Table 3.

(Aging test) The plating powder obtained in Examples 1 to 7, the nickel powder of Comparative Examples 1 and 2, and the plating powder of Comparative Example 3 were subjected to a constant temperature and humidity bath at 60 ° C. and 95% RH for 250 days. Table 3 also shows the results of the evaluation of the conductivity (electric resistance) after the aging test for 500 hours and 500 hours. Table 4 shows the resistance change rate after each aging test result.

[0046]

[Table 3]

[0047]

[Table 4]

(Note) Ωv1 indicates a resistance change rate after 250 hours of aging. Ωv2 indicates a resistance change rate after 500 hours of aging.

As shown in Tables 3 and 4, the conductivity of the examples satisfying the requirements of the present invention is superior to that of the comparative examples. In particular, the deterioration of the electric resistance after aging is small, and the environmental resistance is low. It turns out that it is excellent.

(Conductive Film Test) 3 g of the electroless electroless plating powder of Examples 1 and 2 was added to 100 g of acrylic resin,
After uniformly dispersing in a resin solution of 120 g of methyl ethyl ketone and 25 g of toluene, it was applied to release paper using an applicator and dried to obtain a conductive film having a thickness of 25 μm. In addition, as Comparative Example 4, a conductive film was similarly obtained using flat nickel particles having a true specific gravity of 8.9, an average particle diameter of 40 μm, and an aspect ratio of 2.5.

Next, the conductive film is formed on a flexible substrate having a conductive substrate formed thereon (the conductive substrate has a width of 0.1 mm,
The distance between the conductive bases is 0.1 mm) and placed between two sheets, and heated at a temperature of 110 ° C. under a pressure of 50 kg / cm ² for 15 minutes.
The two substrates were adhered for a second. Although the particles of Examples 1 and 2 were conductive, the sample of Comparative Example 4 was short-circuited between the electrodes.

[0052]

As described above, according to the present invention, it is possible to provide a conductive electroless plating powder with little deterioration in conductivity after aging based on a moisture resistance test. Therefore,
Conventionally, it is extremely useful for applications requiring high conductive performance for ACF and HSC.

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Claims (5)

[Claims] 1. An electroless electroless material comprising a core material particle having an average particle size of 1 to 50 μm and the outermost surface layer coated with gold or palladium by 0.03 to 65 wt% with respect to the core material particle by an electroless plating method. The plating powder has a length-to-width ratio of 2 or less, and an electric resistance after an aging test for 500 hours of 0.1 Ω · cm or less, and a resistance change rate Ωv
= | Ωa−Ωb | / Ωa ≦ 20 (where Ωa indicates the electric resistance before the aging test, and Ωb indicates the electric resistance after the aging test). 2. The conductive electroless plating powder according to claim 1, wherein the core material particles are metal particles. 3. The metal particles are nickel particles.
A conductive electroless plating powder as described in the above. 4. The conductive electroless plating powder according to claim 3, wherein the nickel particles are nickel particles having fine irregularities on the surface. 5. The conductive electroless plating powder according to claim 1, wherein the core material particles may be previously coated with at least one layer of a conductive metal.