JP2003253474A - Conductive particle having excellent press-contacting performance and coating material blending the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conducive particle coated with a noble metal and having excellent performance to press-contacting. <P>SOLUTION: The conductive particle is structured by covering the whole surface of Ni particles having 1 to 10 μm average particle diameter with 0.1-1 mass% base plated layer composed of the noble metal and a Ni alloy and 1-10 mass% finish plated layer composed of the noble metal successively from the surface side of the Ni particles. As the noble metal, one of Au, Ag and Pd is suitably used. It is particularly preferable that the alloy composition of the noble metal with Ni in the base plated layer is (75:25) to (25:75) by atom.% and the diameter of the crystallites is ≤100 nm calculated from the half-band width of X-ray diffraction lines by using a Scherrer's formula. The base plated layer and the finish plated layer can be formed by the sputtering method. The conductive particles can be used by being blended in a coating material as a pigment. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive particle in which the outermost surface of a Ni particle is coated with a noble metal plating, which is particularly suitable for use in laminated electronic parts and has excellent pressure resistance, and the conductive particle. It relates to a paint using.

[0002]

2. Description of the Related Art Conductive particles are deformed by pressure bonding in laminated electronic parts used in electronic parts that are becoming smaller and smaller.
There is a growing demand for anisotropic conductive fillers that conduct electricity between specific electrodes or in a specific direction. In the case of conductive particles to which stress such as pressure bonding is applied, deformable organic particles are used as a base material, and an electroless Ni-P alloy plating layer is formed as a base plating layer on the surface of the organic particles. Conductivity is secured by providing an electroless Au plating layer as a finish plating layer thereon. In such a conventional electroless plating technique, it is impossible to directly perform electroless Au plating on organic particles that are insulators.
It was indispensable to form an electroless Ni-P alloy plating layer as a base plating layer.

[0003]

However, since the Ni-P alloy layer is hard and brittle, it has been a starting point for cracking and peeling during pressure bonding. Therefore, the finish plating layer was easily cracked or peeled off. As a result, it is often the case that a conduction failure is partially caused and the operability of the corresponding electronic component is greatly damaged. In addition, the conventional conductive particles easily react with the resin in the paint, and there is a problem in the paint stability.
Moreover, since the electroless plating method produces a large amount of waste liquid,
The processing was also a big problem.

The present invention is a conductive particle in which the particles themselves are excellent in deformability such as pressure bonding, and the noble metal layer on the surface of the particles is not cracked or peeled off during pressure bonding and maintains stable conductivity. An object of the present invention is to provide a material in which the amount of expensive precious metal used is reduced as much as possible, and to provide a coating material using the same. Furthermore, in the production of conductive particles, it is voluntary to provide those that do not cause environmental problems such as waste liquid.

[0005]

According to the research of the inventor,
It was found that Ni particles can be preferably used as a particle base material having a sufficient deformability at the time of pressure bonding. In that case, it was found that the particle size was required to be as small as 10 μm or less in consideration of conduction characteristics in the conductor paste. However, it was not easy to coat such a fine Ni particle surface with a thin and uniform noble metal coating tightly so as not to crack or peel off during pressure bonding. The target coating cannot be formed simply by using a thin film forming technique such as a sputtering method. It requires some ingenuity.

As a result of repeated studies, it has been found that the desired noble metal coating can be realized by previously plating the surface of the Ni particles as the base material with an alloy plating of the noble metal and Ni as an undercoating layer. At that time, it is important that the noble metal element forming the undercoat plating layer is the same as the element of the desired noble metal coating and that the crystallite diameter of the undercoat plating is as small as possible. When a precious metal coating is formed on this base plating layer, it becomes possible to cover the entire particle with a very small amount of 1-10% by weight of the precious metal coating. It is very excellent in the property (that is, pressure resistance). The present invention has been completed based on such findings.

That is, the above-mentioned purpose is to obtain an average particle size of 1 to 10 μm
The entire surface of the Ni particles is covered with a multilayer coating of 0.1 to 1% by mass of a base plating layer made of a noble metal and an Ni alloy and 1 to 10% by mass of a finish plating layer made of the noble metal from the surface side. Is achieved by conductive particles. Here, the average particle diameter means the diameter of particles corresponding to 50% of the number frequency% measured by the laser diffraction method. It should be noted that the diameter of one particle is defined as a true spherical particle of 1/2 diameter obtained by measuring the major axis and the minor axis. The noble metal refers to gold (Au), silver (Ag) and platinum group (Ru, Rh, Pd, Os, Ir, Pt). “Mass%” of the undercoat plating layer and the finish plating layer means the ratio (%) of the mass of each plating layer to the mass of the conductive particles covered with the multilayer coating.

Further, the present invention particularly provides that the noble metal in the undercoat plating layer and the finish plating layer is any one of Au, Ag and Pd (palladium).

Further, the alloy composition of the noble metal and Ni in the undercoat plating layer is in the range of 75:25 to 25:75 in atomic%, and the crystallite diameter is from the half width of X-ray diffraction to Scherrer's formula. Provided is a value calculated in step 100 nm (nanometer) or less. The crystallite size according to Scherrer's formula is calculated by the following formula (1). D = k × λ / β × cos θ ----- (1) where: D: crystallite diameter (nm) k: constant (k = 0.9 when measured X-ray is Cu kα) λ: measured X-ray Wavelength (nm) β: half-value width (radian) of diffraction line θ: Bragg angle (radian) of diffraction line.

Further, there is provided a base plating layer and a finish plating layer which are formed by a sputtering method. Further, the present invention provides a coating material containing the above conductive particles.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The conductive particles of the present invention have an average particle size of 1 to 10
Fine Ni particles of μm are used. A typical embodiment will be described. The physical vapor deposition method (P
VD), 0.1 to 1 mass% of a noble metal such as Au, Ag and Pd and an alloy of Ni are coated to form an undercoat plating layer, and 1 to 10 mass% of the same kind of precious metal as described above is further formed thereon. Overturn to form a finish plating layer. The surface layer of the particle has such a two-layer plating structure. This underplating layer is controlled so that the crystallite diameter is 100 nm or less as a value calculated by Scherrer's formula from the half width of X-ray diffraction. The control is performed, for example, as described later, in the physical vapor deposition by changing the atomic ratio of the noble metal and Ni constituting the undercoat plating layer from 75:25 to 25: 7.
It becomes possible by setting the range to 5 and optimizing the deposition rate and the temperature of the Ni particles. Among the physical vapor deposition methods, the sputtering method is preferable to the vacuum vapor deposition method and the ion plating method.

In the case of the conductive particles thus obtained, N
The base plating layer existing between the i-particles and the noble metal finish plating layer improves the adhesion of the finish plating layer and makes cracking and peeling less likely to occur during processing. In addition, the undercoat plating layer has a "leveling effect" for thinly and uniformly applying the finish plating layer, so that it is possible to greatly reduce the amount of the noble metal required to cover the entire particles.

The conductive particles are less expensive than the conventional electroless plating method because the amount of precious metal used is extremely small. Furthermore, since it has excellent pressure resistance, it can be widely used as an internal electrode or internal conductor forming paste for various laminated electronic components. In particular, the base plating layer made of an alloy of a noble metal and Ni has improved "brittleness" of the conventional electroless Ni-P plating layer, and greatly contributes to prevention of cracking and peeling.

In recent years, the miniaturization of electronic equipment has progressed, and the wave of miniaturization has inevitably reached internal electronic components. As a result, the "laminated type" of electronic components is becoming the mainstream. A laminated capacitor or inductor used for a laminated component is obtained by laminating a magnetic layer on a conductor layer made of a conductive powder and integrally sintering the layers. The performance of the conductor forming paste forming the conductor layer is the most important factor for determining the performance of the laminated electronic component.

In addition, anisotropic conductive fillers are used in electrode parts such as liquid crystals for deforming conductive particles by pressure bonding so as to conduct electricity between specific electrodes or in a specific direction, and the demand thereof is increasing. Since the distance between the electrodes is becoming smaller due to the demand for improving the resolution of liquid crystal screens, the diameter of the conductive particles used is also extremely small, 10 μm or less. As a result, in order to secure the electrical conductivity (contact resistance) between the electrodes, particles have been required to have greater deformability than ever before.

Since the conductive particles of the present invention have extremely high durability against cracking and peeling of the conductive metal layer on the surface when stress such as pressure is applied, it is possible to meet such strict requirements. The conductive particles disclosed herein are particularly suitable for such applications.

The shape of the Ni particles as the base material is not particularly limited. Granular, porous, spike-shaped, filament-shaped or whisker-shaped carpone Ni particles, spherical atomized Ni particles, lump-shaped crushed Ni particles and the like can be used. It is preferable to use spherical or granular Ni particles in order to exhibit excellent conductivity and reduce anisotropy. In addition, metallic particles such as Co particles, Cu particles, Al particles, Zn particles, brass particles, and stainless particles, ceramic particles such as alumina particles, silica particles, titania particles, and zirconia particles, acrylic resin particles, silicone resin particles The technology of the present invention can be applied to plastic particles such as fluororesin particles and urethane resin particles.

In the present invention, the Ni particles need to have a particle size of 1 to 10 μm. When the particle size is less than 1 μm, the particles are likely to aggregate with each other, and it becomes difficult to uniformly coat the Ni particles with the noble metal. In addition, it is necessary to increase the coating amount of the noble metal as the surface area increases, which increases the manufacturing cost. On the other hand, if the particle size exceeds 10 μm, it becomes necessary to mix a large amount of Ni particles in the conductor forming paste, which tends to cause poor conduction, making it difficult to use as a conductive paste. Ni with an average particle size exceeding 10 μm
The particles can be coated with the noble metal relatively easily by the conventional electroless plating method. However, it has been technically extremely difficult to perform uniform plating on fine Ni particles having an average particle diameter of 10 μm or less as used in the present invention.

The alloy composition of the noble metal and Ni which is the undercoat layer is preferably in the range of 75:25 to 25:75 in atomic%, and most preferably 50:50. If the atomic% is far away from this range, it becomes difficult to reduce the crystallite diameter due to the difference in lattice constant. The possible reasons are as follows. The metal crystal structures of Ni and the noble metals Au, Ag, and Pd are common to the face-centered cubic lattice, but have different lattice constants. The lattice constant a of Ni is 3.51 angstrom, which is the smallest among these, Au is 4.070 angstrom, Ag is 4.078 angstrom, and Pd is 3.882.
It is angstrom and is larger than the lattice constant of Ni by 15.7%, 16.0% and 10.4%, respectively. When the crystal lattice of the underplating layer made of an alloy of a noble metal and Ni is formed by the sputtering method, it is considered that the difference in the lattice constant between the noble metal and Ni as described above is a factor for making the crystallite diameter finer. To be

The formation of the undercoat plating layer proceeds by the process of generation of nuclei → growth of nuclei → continuous film formation. However, by making the crystallite diameter of the undercoat plating layer finer, a finer process is obtained. It becomes possible to generate a large number of nuclei. As a result, a large number of fine plating nuclei can be formed on the entire surface of the Ni particles even with a small amount of base plating of 0.1 to 1% by mass. If such an underplating layer is not formed, the growth of the nucleus is likely to be biased, and therefore the entire surface of the particle cannot be completely covered by a small amount of precious metal plating of 1 to 10% by mass. . Conventionally, in general, a large amount of noble metal plating of at least 30 to 50 mass% was required to uniformly coat the entire surface of Ni particles having a particle size of about 10 μm. According to the technique disclosed in the present specification, this can be reduced to 10% by mass or less, and a significant cost reduction can be realized.

However, if the coating amount of the base plating layer is less than 0.1% by mass, it becomes difficult to form fine nuclei on the entire surface of the Ni particles. On the other hand, the coating amount of the base plating layer is 1% by mass.
If it exceeds, peeling easily occurs from the Ni particles at the time of pressure bonding, and the coating time becomes long, resulting in an increase in cost.

As a result of a detailed study, it was possible to form the above-mentioned thin and tight noble metal finishing plating layer when the crystallite diameter of this undercoating layer was set to 100 nm or less. A more preferable crystallite size is 50 nm or less.

This base plating layer also has the effect of reinforcing the soft noble metal plating layer and improving wear resistance. Further, it is known that when the crystal grains become finer, excellent deformability is exhibited due to the slip effect of the crystal grain boundaries. When the crystallite diameter of the underplating layer is as small as 100 nm or less,
It is considered that due to the grain boundary sliding effect due to the refinement of crystal grains, cracking and peeling are less likely to occur even if a large deformation is given.

In order to reduce the crystallite diameter of the undercoat plating layer to 100 nm or less, the sputtering rate should be reduced and N
It was found that the temperature of the i particles should be kept low. Specifically, the noble metal-
The coating speed of the Ni alloy may be set to about 0.01 g / hr per 1 g of the Ni particles, and the temperature of the Ni particles may be kept at 200 ° C. or lower.

The types of precious metals are Au (gold) and Ag.
(Silver) and Pd (palladium) are preferable, but Pt (platinum), Ru (ruthenium), Rh (rhodium) and the like can also be used. Also, these alloys can be used. When using a plurality of noble metal elements as an alloy, the noble metal forming the undercoat plating layer should also contain the plurality of elements. The coating amount of the noble metal in the finish plating layer is 1 to 10% by mass, preferably 3 to 5% by mass. When the coating amount is less than 1% by mass, it is difficult to form a continuous coating film, that is, it is difficult to cover the entire particles with the coating film, resulting in insufficient conductivity. On the other hand, when the coating amount exceeds 10% by mass, the amount of the noble metal used increases and the sputtering time becomes long, resulting in an increase in cost.

As the coating method, since the delicate control of the coating state and the densification of the coating are required as described above, the sputtering method in which the kinetic energy of the noble metal at the time of adhering to the Ni particles is high is desirable. In the case of the electroless plating method, the surface of the Ni particles is previously activated by Pd or the like as a pretreatment, and the Pd adhered portion becomes the nucleus generation point during the formation of the metal film during the progress of the electroless plating. It is said that Since this Pd adhesion utilizes a simple adsorption phenomenon, the adhesion density is not so high. On the other hand, in the case of the sputtering method, the noble metal atoms excited to the plasma state repeatedly collide with the surface of the Ni particles at a high speed, so that the density of nucleation points during the formation of the metal coating becomes extremely high. is there.

As a method of forming the coating layer on the surface of the particles by using the sputtering method, for example, the technique previously disclosed by the inventors in Japanese Patent Laid-Open No. 2-153068 can be applied.
If this is used, Ni particles can be put in a rotating barrel and irradiated with an alloy of noble metal and Ni sputtered from a target or particles of noble metal while stirring, and the Ni particle surface can be uniformly coated. .

When the noble metal and Ni alloy are coated by the sputtering method, targets having various shapes as shown below can be used. A method in which a target composed of a plurality of crystalline phases, which have the same average composition as the alloy to be created, but are not a single phase, is prepared by a sintering method or a melting method. A method of using a "combined target" in which the metal to be alloyed is embedded in a metal plate that is composed of the main components of the alloy to be created. A method of combining a plurality of single metal targets to obtain a sputtering coating having an alloy composition to be produced.
In any case, it is possible to obtain a predetermined noble metal-Ni alloy coating in which each metal element is uniformly solid-dissolved. Other,
A vacuum deposition method can also be used, but it is not always easy to maintain a constant alloy composition of Au, Ag, Pd and the like because Ni and Ni have large melting points and vapor pressures.

When Ni particles which are in stock for a long time after production and have a thick oxide film formed on the surface are used,
The oxide film on the surface may be dissolved and removed in advance with an aqueous solution of dilute sulfuric acid, dilute hydrochloric acid or the like, immediately followed by vacuum drying at a low temperature of 100 ° C. or lower, and then the underlying plating layer may be formed. Further, when the base plating and the finish plating are continuously performed, the surface of the finish plating layer is hardly oxidized, so that the conductive particles having excellent adhesion can be obtained.

In order to improve the dispersibility in the paint,
After coating the noble metal, surface treatment may be performed with various silane coupling agents or titanate coupling agents. In order to prevent the change in the conductivity of the coating film with time as much as possible, after coating with a noble metal, the surface is coated with an antioxidant such as hydroquinone, triethanolamine, O-sulfobenzimide or N-octadecanoylbenzenesulfonylamide. You may give a process.

[0031]

EXAMPLES The present invention will be described below with reference to examples and comparative examples. The conditions and results of each Example / Comparative Example are shown in Table 1 below. [Examples 1, 2 and 3] Ni particle powder (I
NCO Type 123, spike shape) is used to coat the surface of the particles by sputtering with alloys of Au and Ni of various compositions so that the coating amount is 0.1, 0.5, or 1 mass%. A base plating layer was formed.
The crystallite diameter of this undercoat layer was in the range of 45 to 90 nm as a result of calculation from Scherrer's formula. On top of that,
1, 5, or 10 mass% Au by sputtering method
Was coated to form a finish plating layer. These were mixed in an epoxy resin-based paint at 5 vol% (depending on the bulk volume) to form a film having a thickness of 25 μm. Then, these were sandwiched between glass substrates coated with thermoplastic polyether sulfone resin, and thermocompression bonded for 15 seconds at a pressure of 20 kg / cm ² and a temperature of 150 ° C. The obtained resin-conductive particle composite was used as a test piece.

About this test piece, with an optical microscope,
The cross-section of the particles thermocompressed and the surface state of the coating film were observed, and the pressure resistance was evaluated according to the following criteria. ◯: Neither film cracking nor film peeling was observed. Δ: Film cracking was observed, but film peeling did not occur. X: The peeling of the coating film was recognized. Further, the resistivity of the above test piece was measured by the 4-terminal method. The evaluation criteria are as follows. ◯: Resistivity is less than 3 × 10 ⁴ Ω · cm, and conductivity is good. ×: Resistivity is 3 × 10 ⁴ Ω · cm or more, and conductivity is poor.

[Comparative Example 1] Using the same Ni particles as in Examples 1 to 3, test pieces were prepared in the same manner as in Examples 1 to 3, and the pressure resistance and resistivity were evaluated. However, the composition of the base plating layer was Au: Ni = 90: 10 (atomic ratio), and the coating amount was 2 mass%. Underplating layer has a crystallite diameter of 400
It was as large as nm. The finish plating layer was coated with 20% by mass of Au.

Comparative Example 2 Using the same Ni particles as in Examples 1 to 3, test pieces were prepared in the same manner as in Examples 1 to 3, and the pressure resistance and resistivity were evaluated. However, the composition of the base plating layer was Au: Ni = 10: 90 (atomic ratio), and the coating amount was 0.05 mass%. The crystallite diameter of the undercoat layer is
It was as large as 163 nm. The finish plating layer was coated with 0.1% by mass of Au.

[Comparative Example 3] A test piece was prepared in the same manner as in Examples 1 to 3 except that the same Ni particles as in Examples 1 to 3 were used and no undercoating layer was applied. The sex and resistivity were evaluated. Finish plating layer is 10% by mass of Au
Coated.

[Comparative Example 4] Instead of the sputtering method of Comparative Example 3, an electroless plating method was used to form a finish plating layer.

[Examples 4, 5, 6] Ni having an average particle size of 10 μm
Using particle powder (Type HDNP manufactured by INCO, granular),
The surface of the particles was coated with an alloy of Ag and Ni having various compositions so as to have a coating amount of 0.1, 0.5, or 1 mass% by a sputtering method to form a base plating layer. The crystallite diameter of this undercoat layer was in the range of 50 to 100 nm as a result of calculation from Scherrer's formula. Furthermore, 1, 5 or 10 mass% by sputtering method
Was coated with Ag to form a finish plating layer. About these, the test piece was produced by the method similar to Examples 1-3 (the resin used is also the same), and pressure resistance and resistivity were evaluated.

[Comparative Example 5] Using the same Ni particles as in Examples 4 to 6, test pieces were prepared in the same manner as in Examples 4 to 6, and the pressure resistance and resistivity were evaluated. However, the composition of the base plating layer was Ag: Ni = 90: 10 (atomic ratio), and the coating amount was 2 mass%. The crystallite diameter of the undercoat layer is 500
It was as large as nm. The finish plating layer was coated with 20% by mass of Ag.

[Comparative Example 6] Using the same Ni particles as in Examples 4 to 6, a test piece was prepared in the same manner as in Examples 4 to 6, and the pressure resistance and resistivity were evaluated. However, the composition of the base plating layer was Ag: Ni = 10: 90 (atomic ratio), and the coating amount was 0.05 mass%. The crystallite diameter of the undercoat layer is
It was as large as 220 nm. The finish plating layer was coated with 0.1% by mass of Ag.

[Comparative Example 7] Using the same Ni particles as in Examples 4 to 6, a test piece was prepared in the same manner as in Examples 4 to 6 except that the undercoat plating layer was not applied, and pressure resistance was applied. The sex and resistivity were evaluated. Finish plating layer is 10% by mass of Ag
Coated.

Comparative Example 8 A finishing plating layer was formed by using an electroless plating method instead of the sputtering method of Comparative Example 7.

[Examples 7, 8 and 9] Ni having an average particle size of 10 μm
Particle powder (INCO Type 255, filament)
By using Pd and Ni alloys of various compositions on the surface of the particles by sputtering,
Alternatively, coating was performed so as to be 1% by mass to form a base plating layer. The crystallite diameter of this undercoat layer was in the range of 48 to 93 nm as a result of calculation from Scherrer's formula.
Further, Pd of 1, 5, or 10 mass% was coated thereon by a sputtering method to form a finish plating layer. About these, the test piece was produced by the method similar to Examples 1-3 (the resin used is also the same), and pressure resistance and resistivity were evaluated.

[Comparative Example 9] Using the same Ni particles as in Examples 7 to 9, a test piece was prepared in the same manner as in Examples 7 to 9 and evaluated for pressure resistance and resistivity. However, the composition of the base plating layer was Pd: Ni = 90: 10 (atomic ratio), and the coating amount was 2 mass%. The crystallite diameter of the underlying plating layer is 460
It was as large as nm. The finish plating layer was coated with 20% by mass of Ag.

[Comparative Example 10] Using the same Ni particles as in Examples 7 to 9, test pieces were prepared in the same manner as in Examples 7 to 9, and the pressure resistance and resistivity were evaluated. However, the composition of the underlying plating layer was Pd: Ni = 10: 90 (atomic ratio), and the coating amount was 0.05% by mass. The crystallite diameter of the undercoat layer is
It was as large as 185 nm. The finish plating layer was coated with 0.1% by mass of Pd.

[Comparative Example 11] Using the same Ni particles as in Examples 7 to 9, a test piece was prepared in the same manner as in Examples 7 to 9 except that the undercoat plating layer was not applied. The sex and resistivity were evaluated. Finished plating layer contains 10% by mass of Pd
Coated.

Comparative Example 12 A finishing plating layer was formed by using an electroless plating method instead of the sputtering method of Comparative Example 11. The above results are summarized in Table 1.

[0047]

[Table 1]

From these results, it can be seen that the conductive particles of the present invention have excellent pressure resistance and low resistivity. Further, it is understood that the sputtering method is more suitable as the coating method than the electroless plating method. The underplating layer made of an alloy of a noble metal and Ni formed by the sputtering method is firmly bonded to Ni particles and has a very thin film thickness, so that peeling due to internal strain such as thermal stress is unlikely to occur.

[0049]

As described above, the conductive particles of the present invention are most characterized in that they have the undercoat plating layer.
For this reason, it is possible to provide conductive particles that are excellent in pressure resistance and are resistant to cracking or peeling of the plating layer on the surface even during pressure bonding accompanied by deformation. The laminated electronic component using this is excellent in operability, and the stability and reliability of the electrode are also improved. In addition, since the conductive particles of the present invention can be manufactured by using the sputtering method, no waste liquid is generated.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) C22C 5/02 C22C 5/02 5/04 5/04 5/06 5/06 Z 19/03 19/03 L C23C 14/00 C23C 14/00 A 14/14 14/14 GF Term (reference) 4J037 AA04 AA18 AA22 AA25 CA03 DD05 DD13 EE04 EE18 EE23 FF11 FF18 4J038 EA011 HA066 KA12 BA02 BA02 BA05 BA22 BA02 BA02 BA02 BA02 BA05 EA01 4K044 AA06 AB01 BA06 BA08 BB03 BC14 CA13 CA15 CA29

Claims (5)

[Claims] 1. The entire surface of the Ni particles having an average particle size of 1 to 10 μm is composed of an alloy of a noble metal and Ni from the surface side of the Ni particle.
Conductive particles covered with a multilayer coating consisting of 1% by mass of a base plating layer and 1 to 10% by mass of a noble metal finish plating layer. 2. The conductive particle according to claim 1, wherein the noble metal is any of Au, Ag and Pd. 3. The noble metal and Ni alloy composition of the undercoat layer is in the range of 75:25 to 25:75 in atomic%, and the crystallite diameter thereof is from the half width of X diffraction to the Scherrer's formula. The conductive particle according to claim 1, which has a calculated value of 100 nm or less. 4. The base plating layer and the finish plating layer are formed by a sputtering method.
3. The conductive particles according to item 3. 5. A paint containing the conductive particles according to claim 1 as a pigment.