TW201542831A - Conductive particle, conductive powder, conductive polymer composition and anisotropic conductive sheet - Google Patents

Abstract

The invention provides a conductive particle, which is cheaper than conventional ones and has sufficiently high conductivity, and a conductive powder, a conductive polymer composition and an anisotropic conductive sheet comprising the conductive particle. The conductive particle 10 according to the embodiments of the invention comprises: a spherical core 12 comprising Ni and P, a Pd-plated layer 14 covering the surface of the core 12, and an Au-plated layer 16 covering the surface of the Pd-plated layer 14.

Description

Conductive particles, conductive powder, conductive polymer composition, and anisotropic conductive sheet

The present invention relates to a conductive particle having a core having a main component of Ni, and a conductive powder, a conductive polymer composition, and an anisotropic conductive sheet containing such conductive particles.

The polymer composition containing the conductive particles is widely used for electrical connection between electronic components, for example, as an anisotropic conductive sheet (ACF) or an anisotropic conductive paste (ACP) having conductivity only in the thickness direction. In particular, an anisotropic conductive sheet is widely used for forming an electrical connection in a small electric device such as a mobile phone. Further, an anisotropic conductive sheet using a rubber (including a synthetic rubber) as a polymer as a pressure-sensitive anisotropic conductive sheet is also used for formation of a temporary electrical connection in an inspection (for example, impedance measurement) of a wiring board or the like (for example, PCR ( Registered trademark of JSR Co., Ltd.)).

For example, Patent Documents 1 to 3 disclose an anisotropic conductive sheet using conductive particles having ferromagnetic properties. In the anisotropic conductive sheets, the conductive particles are arranged in the thickness direction and are dispersedly distributed in the in-plane direction of the sheet. When the sheet is pressed in the thickness direction, the conductive particles arranged in the thickness direction are close to each other to form a conductive path. The conductive particles having strong magnetic properties are aligned in the thickness direction by a magnetic field.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: International Publication No. 02/13320

Patent Document 2: International Publication No. 2004/021018

Patent Document 3: Japanese Patent Laid-Open Publication No. 2012-174417

Patent Document 4: Japanese Patent Laid-Open No. 2006-131978

Patent Document 5: Japanese Patent Laid-Open Publication No. 2009-197317

However, in order to obtain a sufficiently high conductivity (a sufficiently low volume resistivity, for example, 0.3 × 10 ^-5 Ω ‧ m or less), a conventional conductive particle forms Au (gold) having a thickness of, for example, 200 nm (0.2 μm). Plating, there is a problem of high cost. Further, in applications requiring high moisture resistance reliability, it is difficult to use a metal other than Au for the plating layer.

The present invention has been made to solve the above problems, and provides conductive particles which are relatively inexpensive and have sufficiently high conductivity and moisture resistance reliability, and conductive powders containing such conductive particles, and conductivity. A polymer composition and an anisotropic conductive sheet are intended.

The conductive particles according to the embodiment of the present invention include a spherical core including Ni and P, a Pd plating layer covering the surface of the core, and an Au plating layer covering the surface of the Pd plating layer.

In some embodiments, the Pd plating layer is an electroless reduction coating.

In some embodiments, the Au plating layer is an electrolessly substituted plating layer.

In some embodiments, the thickness of the Pd plating layer is larger than the thickness of the Au plating layer, and the thickness of the Au plating layer is 5 nm or more and less than 40 nm. The thickness of the above Pd plating layer is preferably more than 5 nm and less than 300 nm.

In some embodiments, the core further comprises Cu and Sn.

In some embodiments, the diameter of the core is 1 μm or more and 100 μm or less. The diameter of the above core is preferably 3 μm or more.

The conductive powder system according to the embodiment of the present invention contains the powder of the conductive particles according to any one of the above aspects, and the median diameter d50 in the cumulative volume distribution curve is 3 μm or more and 100 μm or less, and [(d90- D10) / d50] ≦ 0.8.

The conductive polymer composition according to the embodiment of the present invention includes the conductive powder and the polymer, and the polymer is, for example, a rubber, a thermoplastic resin or a thermosetting resin.

The anisotropic conductive sheet according to the embodiment of the present invention is formed of the above-described conductive polymer composition, and the conductive particles are arranged in the thickness direction.

According to the embodiment of the present invention, it is possible to provide conductive particles which are inexpensive and have sufficiently high conductivity and moisture resistance, and conductive powders and conductive polymer compositions containing such conductive particles and Anisotropic conductive sheet.

10‧‧‧Electrical particles

12‧‧‧nuclear (NiP nuclear)

14‧‧‧Pd plating

16‧‧‧Au plating

Fig. 1 is a schematic cross-sectional view showing conductive particles using an embodiment of the present invention.

Fig. 2 is a view showing a cross-sectional SEM image of the electroconductive particles of the examples.

Fig. 3 is a graph showing the dependence of the volume resistivity of the conductive particles (Pd plating layer + Au plating layer) of the example and the conductive particles of the reference example (without Au plating layer) on the thickness of the Pd plating layer. table.

Fig. 4 is a graph showing the dependence of the volume resistivity of the conductive particles of the comparative example (without Pd plating) on the thickness of the Au plating layer.

Fig. 5 is a view showing the structure of a device used for the measurement of the volume resistivity of the conductive particles.

Hereinafter, the conductive particles, the conductive powder, the conductive polymer composition, and the anisotropic conductive sheet according to the embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is a schematic cross-sectional view showing a conductive particle 10 according to an embodiment of the present invention. The conductive particles 10 have a spherical core 12, a Pd (palladium) plating layer 14 covering the surface of the core 12, and an Au plating layer 16 covering the surface of the Pd plating layer 14. The core 12 system contains Ni (nickel) and P (phosphorus). The diameter of the core 12 is, for example, 1 μm or more and 100 μm or less. If the diameter of the core 12 is less than 1 μm, since the aggregation of the core 12 becomes severe, it is difficult to treat it as a powder. If the diameter of the core 12 exceeds 100 μm, it overflows from the conductive path, and for example, the possibility of causing a short circuit between adjacent wirings becomes high. The diameter of the core 12 is preferably 3 μm or more, and preferably 30 μm or less. If the diameter of the core 12 is 3 μm or more, the aggregation of the core 12 is moderated when Pd plating is performed, which is practical. If the diameter of the core 12 is 30 μm or less, the overflow from the conductive path is reduced or eliminated. The conductive powder which is an aggregate of the conductive particles 10 is preferably a powder having a cumulative volume distribution curve having a median diameter d50 of 3 μm or more and 100 μm or less and [(d90-d10)/d50]≦0.8. The median diameter d50 can be used as an index of the average particle diameter of the conductive powder. In addition, when [(d90-d10)/d50] exceeds 0.8, the variation in particle diameter is too large, and there are conductive particles having a small particle diameter which are not in contact with the wiring or the electrode in the conductive path, and thus the connection reliability is lowered. . D10 and d90 represent particle sizes of cumulative volume fractions of 10% and 90%, respectively. In addition, unless otherwise stated, this note The particle size distribution in the book is obtained by the laser diffraction scattering method.

As the core 12 of the conductive particles 10, for example, the conductive particles described in Patent Document 4 or 5 can be suitably used. Since the NiP conductive powder produced by the production method described in Patent Document 5 is monodispersed and has a narrow particle size distribution, it has an advantage that it can easily produce a conductive powder satisfying the relationship of [(d90-d10)/d50]≦0.8. .

The core 12 has Ni as a main component and contains P (phosphorus), Cu (copper), and/or Sn (tin). P, Cu, and Sn are both intended to inhibit the growth or aggregation of the core during the nucleation of the core 12, and may be added as a raw material component in the reaction treatment liquid. In order to reduce the resistivity of the core 12 itself, the content of such elements in the core 12 is as small as possible. Specifically, the core 12 preferably contains 1 to 15% by mass of P, and more preferably 10% by mass or less, relative to the whole. When the content of P exceeds 15% by mass, the volume resistivity of the core 12 remarkably rises, which is not practical. Further, the core 12 preferably contains 0.01% by mass to 18% by mass of Cu with respect to the whole. When the content of Cu exceeds 18% by mass, the adhesion between the core 12 and the Pd plating layer 14 may be lowered. Further, the core 12 preferably contains 0.05% by mass to 10% by mass of Sn relative to the whole. When the content of Sn exceeds 10% by mass, the adhesion between the core 12 and the Pd plating layer 14 may be lowered. Further, in addition to Ni, P, and Cu, the core 12 preferably contains Sn. In the case of producing the powder used in the core 12, since Cu and Sn act in the form of a catalyst poison of the nucleation reaction, it is easy to produce a powder having a narrow particle size distribution by monodispersion. Further, Cu and Sn are subjected to eutectoid growth during the growth of the NiP conductive particles.

The Pd plating layer 14 is preferably an electroless reduction coating. The electroless reduction coating has no adhesion which is inferior to the electroless substitution coating, and pinholes occur less than the electroless substitution coating. The Au plating layer 16 is preferably an electroless replacement plating layer. The adhesion of the electroless-substituted Au plating layer to the Pd plating layer 14 is superior to that of the non-electrolytic reduction Au plating layer. Electroless substitution plating The Au reaction is accompanied by dissolution of the Pd plating layer 14, so that the thickness of the Pd plating layer 14 is preferably larger than the thickness of the Au plating layer 16, and the thickness of the Au plating layer 16 is less than 40 nm. If the thickness of the Au plating layer exceeds 40 nm, there is no particular change in characteristics and waste in cost. The thickness of the Pd plating layer 14 is preferably more than 5 nm and less than 300 nm. When the Pd plating layer is 5 nm or less, when the electroless substitution Au plating is performed on the Pd plating layer, the Pd plating layer is completely dissolved. When all of the Pd plating layer is dissolved, there is a possibility that the adhesion of the Au plating layer is lowered or Au is not precipitated. Further, when the thickness of the Pd plating layer exceeds 300 nm, there is no particular change in characteristics and waste in cost. In view of the above, in the case where the reliability is further improved, it is preferable that the thickness of the Pd plating layer exceeds 50 nm and is less than 200 nm.

The conductive particles 10 according to the embodiment of the present invention have a Pd plating layer 14 covering the surface of the core 12 and an Au plating layer 16 covering the surface of the Pd plating layer 14, and thus are more inexpensive and have sufficiently high conductivity and moisture resistance. Sex. The reason for this will be described below, but the following description does not limit the use of the embodiment of the present invention.

As a method of forming an Au plating layer on particles containing Ni as a main component (abbreviated as Ni particles), there are electroless reduction type Au plating and electroless substitution type Au plating. In general, plating of particles (powder) does not use electroplating (due to aggregation of particles), so "non-electrolytic" is omitted below and is simply referred to as "reduced type" or "substituted type".

When the Ni particles are subjected to substitutional Au plating, Ni is eluted into the plating solution, and electrons released by ionization of Ni are received by Au ions in the plating solution, and Au is precipitated on the surface of the Ni particles. Since the position where Ni is eluted does not necessarily coincide with the position where Au precipitates, a large number of pinholes are formed on the substituted Au plating layer. When a moisture resistance test (for example, a pressure cook test) is performed, moisture invaded from the pinhole oxidizes Ni to form a hydroxide. A part of the hydroxide is present on the Au plating layer, and as a result, there is a problem that the conductivity is lowered. In addition, the substitution of the Au plating layer with the Ni particles is higher than that of the following reduction plating layer, but the plating cannot be increased. Layer thickness. For example, it is difficult to form an Au plating layer having a thickness exceeding 100 nm, particularly 200 nm or more, by substitution plating.

On the other hand, in the Au plating system, since Au ions in the plating solution are precipitated as Au by receiving electrons from the reducing agent, there is no elution of Ni. Therefore, the pinhole for reducing the Au plating layer is less than that of the Au plating layer, and an Au plating layer having a thickness of 200 nm or more can be formed. However, the adhesion between the reduced Au plating layer and the Ni particles is low, and when a moisture resistance test (for example, a pressure cooking test) is performed, there is a problem that the reduced Au plating layer is peeled off.

Further, the Au plating layer is first formed on the surface of the Ni particles, and the Au plating layer is used in combination with the substitution plating layer. Although the above problem can be solved, in order to obtain sufficient conductivity, the entire thickness of the Au plating layer must be about 200 nm or more. Therefore, the cost is higher.

On the other hand, the conductive particles 10 according to the embodiment of the present invention have a core including Ni and P (hereinafter referred to as "NiP core") 12, a Pd plating layer 14, and an Au plating layer 16 covering the Pd plating layer 14. Since Pd is cheaper than Au, the conductive particles 10 are inexpensive at least because of the Pd plating layer and the conductive particles having only the Au plating layer.

Further, the Pd plating layer 14 has good adhesion to both the NiP core 12 and the Au plating layer 16, and does not cause peeling. Further, although not as good as Au, Pd still has high conductivity. For example, a Pd plating layer having a thickness of about 100 nm has a volume resistivity of 0.3 × 10 ^-5 Ω ‧ m or less, which is sufficiently low. Further, Pd has a higher ionization tendency (lower oxidation-reduction potential) than Au, and is easily oxidized. However, since the Pd plating layer 14 is covered with the Au plating layer 16, the conductive particles 10 have high moisture resistance reliability.

The Pd plating layer 14 is preferably a reduced plating layer. Compared with the film formed by the substitution plating, the film formed by the reduction plating has less pinholes and is dense, and grain boundary corrosion is less likely to occur. Moreover, the reduction plating is easier to form a thick plating layer than the substitution plating. Due to Pd The redox potential is between the redox potential of Ni and the redox potential of Au, so the substitution reaction of Pd and Ni is not as intense as the substitution reaction of Au and Ni. As a result, it is considered that the adhesion between the Pd reduction plating layer 14 and the NiP core 12 is higher than the adhesion between the Au reduction plating layer and the NiP core 12. When the Au reduction plating layer is directly formed on the NiP core 12, it is considered that the intense substitution reaction of Au and Ni which occurs as a side reaction during Au reduction plating causes the adhesion between the Au reduction plating layer and the NiP core 12 to decrease.

The Au plating layer 16 is preferably a replacement plating layer. The difference between the oxidation-reduction potential of Au and Pd is small, and the substitution reaction between Au and Pd is less likely to occur. The Au plating layer 16 can be formed on the Pd plating layer 14 by the substitution reaction of the grain boundary and/or pinholes passing through the Pd plating layer 14 and Ni contained in the NiP core 12. By adjusting the thickness of the Pd plating layer 14, the thickness of the Au plating layer 16 formed by the substitution plating can be controlled. The reason is that if the grain boundary and/or the pinhole are covered with the Au plating layer by the substitution plating, the Au plating layer 16 is stopped. Preferably, the thickness of the Pd plating layer 14 is greater than the thickness of the Au plating layer 16, and the thickness of the Au plating layer 16 is less than 40 nm. If the thickness of the Au plating layer 16 exceeds 40 nm, there is no particular change in characteristics and waste in cost. For example, if the thickness of the Pd plating layer 14 exceeds, for example, 100 nm, the Au plating layer 16 having a thickness of less than 30 nm can be formed.

Further, the Au plating layer 16 can also function as a reduction plating layer. Since the substitution reaction of the side reaction Au and Pd at the time of reduction plating does not easily occur, the adhesion between the Au plating layer and the Pd plating layer 14 is sufficiently high. However, in order to control the thickness of the Au plating layer 16, in particular, in order to form the thin Au plating layer 16 of less than 40 nm with good reproducibility, it is preferable to replace the plating.

The conductive particles 10 according to the embodiment of the present invention can be obtained, for example, by the following method.

First, a NiP powder containing NiP particles as the NiP core 12 is prepared. The NiP powder is preferably produced by the method described in Patent Document 5. Specifically, nickel sulfate hexahydrate and copper sulfate pentahydrate are prepared in such a manner that the molar ratio of Ni to Cu is Ni/Cu=239, and dissolved in pure water to prepare a metal salt aqueous solution 15 (dm ³ ). . Next, sodium acetate was dissolved in pure water to a concentration of 1.0 (kmol/m ³ ), and sodium hydroxide was further added to prepare a pH-adjusted aqueous solution 15 (dm ³ ). Then, the aqueous metal salt solution and the pH-prepared aqueous solution were stirred and mixed to form a mixed aqueous solution of 30 (dm ³ ), and the pH was measured to be 8.1. Then, the above mixed aqueous solution was maintained at 343 (K) by heating with an external heater while bubbling with N ₂ gas, and stirring was continued. Next, an aqueous reducing agent solution 15 (dm ³ ) obtained by dissolving sodium phosphonate in a concentration of 1.8 (kmol/m ³ ) in pure water was prepared, and this was also heated to 343 (K) by an external heater. Then, the 30 (dm ³ ) mixed aqueous solution and the 15 (dm ³ ) reducing agent aqueous solution were prepared and mixed at a temperature of 343 ± 1 (K), and a NiP powder was obtained by an electroless reduction method.

(plated Pd)

A plated Pd bath (for example, Pallet LMII manufactured by Kojima Chemical Co., Ltd., having a Pd concentration of 10 g/L (liter)) of 300 mL was prepared.

A reducing solution containing sodium formate as a main component (for example, Pallet II manufactured by Kojima Chemical Co., Ltd.) was prepared in an amount of 550 mL.

The Pd plating bath was mixed with the reducing solution, and then diluted with pure water to obtain 3 L of Pd plating solution (pH 5.5). The Pd plating solution was stirred while being heated at 328 K by an external heater.

Prepared 300 mL of the reducing solution diluted with pure water (pH 5.5). NiP powder (mass 50 g) was mixed in a reducing aqueous solution, and stirred at room temperature for 10 minutes.

Thereafter, the reduced aqueous solution in which the NiP powder is dispersed is mixed in the above plating In the liquid, the Pd plating layer 14 is formed by reduction plating.

Accordingly, the NiP core 12 covered by the Pd plating layer 14 is obtained. When Pd reduction plating is performed under the above conditions, a Pd plating layer 14 having a thickness of about 115 nm can be obtained.

Further, by adjusting the mixing ratio of the Pd plating bath: reducing solution in the Pd plating step to 300 mL: 550 mL, the thickness of the Pd plating layer can be controlled. For example, when the mixing ratio of the Pd plating bath: reducing solution is 420 mL: 790 mL, and 35 g of the NiP core 12 is plated, a Pd plating layer having a thickness of about 240 nm can be obtained.

(plated Au)

0.1 g of sodium lauryl sulfate and 0.9 g of potassium gold cyanide were mixed in 200 mL of Au plating bath (for example, Dip G-FP manufactured by Kojima Chemical Co., Ltd.), and diluted with pure water to prepare an Au plating solution (pH 4.0). ) 2L. The Au plating solution was heated while maintaining the temperature at 334 K by an external heater.

Next, the powder (mass 35 g) of the NiP core 12 covered with the Pd plating layer 14 was mixed in 100 mL of an aqueous solution in which citric acid monohydrate was dissolved at a concentration of 20 g/L, and stirred at room temperature for 5 minutes.

Thereafter, the aqueous solution in which the citric acid monohydrate was dissolved and the NiP powder were mixed in the Au plating solution, and the Au plating layer 16 was formed by substitution plating. When Au-plated plating is performed under the above conditions, an Au plating layer 16 having a thickness of about 20 nm can be obtained.

Accordingly, the conductive particles 10 in which the NiP core 12 is covered by the Pd plating layer 14 and the Au plating layer 16 are obtained. Fig. 2 shows a cross-sectional SEM image of the electroconductive particle 10 of the embodiment thus obtained. A state in which the NiP core 12 is covered by the Pd plating layer 14 can be confirmed. Further, since the Au plating layer 16 has a thickness of 20 nm and is thin, it is difficult to confirm its existence in the SEM image.

Further, the Pd plating layer 14 and the Au plating layer 16 which the conductive particles 10 have The thickness can be determined by, for example, the following formula, based on the composition of the conductive particles 10, the density of the NiP core 12, the particle diameter (median diameter) of the NiP core 12, and the density of Pd and Au. The composition analysis of the conductive particles 10 can be carried out by dissolving a predetermined amount of the conductive particles 10 in aqua regia, diluting with pure water, and then using an ICP emission spectrometer.

Coating thickness (μm) = (mass % of plating layer / 100) × (1/ density of elements constituting the plating layer (g / cm ³ )) × (total surface area of 1 / NiP core (cm ² )) × 10,000

Wherein, Au has a density of 19.32g / cm ^3, Pd a density of 11.99g / cm ^3, the density of NiP particles is 7.8g / cm ^3, the total surface area of the core is a core NiP surface area (e.g., a median particle diameter d50 The product of the sphere surface area) and the total number of NiP cores contained in the sample.

The experimental examples are shown below, and the characteristics of the conductive particles 10 according to the embodiment of the present invention will be described in further detail. The experimental examples shown here are Examples 1 to 4 (Pd plating + Au plating), Reference Examples 1 to 4 (without Au plating), and Comparative Examples 1 to 4 (without Pd plating). In Examples 1 to 4, Au plating layers were formed on the Pd plating layers of Reference Examples 1 to 4, respectively, and Comparative Examples 1 to 4 directly formed Au replacement plating layers on the NiP cores 12.

In all the experimental examples, the NiP powder for the NiP core 12 had a median diameter d50 of 20.0 μm, and a powder of [(d90-d10)/d50] of 0.7 was used. The NiP powder has a composition containing 6.3% by mass of P, 3.3% by mass of Cu, 0.2% by mass of Sn, and the balance Ni as a whole.

As described above, the thickness of the Pd plating layer in the examples and the reference examples was changed by adjusting the mixing ratio of the plating Pd bath and the reducing liquid. As described above, the thickness of the Au plating layer in the examples is limited by the presence of a Pd plating layer having a thickness exceeding 100 nm, and in any of the examples, the thickness of the Au plating layer is about 20 nm. Further, the thickness of the Au plating layer in the comparative example was changed by adjusting the plating time and/or the gold potassium cyanide concentration of the plating solution.

The thicknesses and volume resistivities of the respective plating layers of the conductive powders of the examples, the reference examples, and the comparative examples are shown in Tables 1 to 3 and FIGS. 3 to 4. 3 is a graph showing the dependence of the volume resistivity of the conductive particles (Pd plating layer + Au plating layer) of the example and the conductive particles of the reference example (without Au plating layer) on the thickness of the Pd plating layer, and FIG. 4 shows a comparative example ( A graph of the dependence of the volume resistivity of the conductive particles without Pd plating on the Au plating thickness.

As described above, the thickness of the plating layer is determined by calculation based on the composition analysis of the conductive powder. Moreover, the volume resistivity of each conductive powder was measured using the apparatus shown in FIG. 1.15 g of the powder sample was placed in a cylinder having an inner diameter of 11 mm, and the overall resistance value was measured by a resistance meter (resistance meter 3541 of the day-mounted electric mechanism) while a load of 22 MPa was applied by a jig (piston) made of Cu. Based on the resistance value, the volume resistivity was obtained by the following formula.

Volume resistivity = (integral resistance value - resistance value of fixture) × π × (11/2) ² × 100 / thickness

Further, the thickness of the above formula is expressed in cm units in terms of the thickness (parallel to the pressing direction) of the powder in the measuring cylinder when the above-described load is applied.

[Table 2]

As can be seen from FIG. 3 and Tables 1 and 2, the conductive powders of the Pd plating layers having a thickness of about 115 nm or more (Examples 1 to 4 and Reference Examples 1 to 4) have a volume resistivity of 0.3 × 10 ^-5 Ω··m or less. , low enough. When the thickness of the Pd plating layer is increased to about 240 nm, even if only the Pd plating layer (Reference Example 4), the volume resistivity is 0.22 × 10 ^-5 Ω ‧ m or less. As is apparent from the comparison between Table 1 and Table 2, when an Au plating layer having a thickness of about 20 nm is formed on the Pd plating layer, the volume resistivity is lowered. Although the degree of volume resistivity reduction is small, by forming the Au plating layer, an increase in volume resistivity due to oxidation of the Pd plating layer can be suppressed. The Au plating improves the moisture resistance reliability of the conductive powder. In the conductive cooking samples of Examples 1 to 4 (conditions: 125 ° C, 95 RH %, 2.2 atm), no increase in volume resistivity or change in appearance was observed even after 100 hours.

On the other hand, as is clear from Table 3 and Fig. 4, when only the Au plating layer was formed on the NiP particles, even if the thickness of the Au plating layer was about 47 nm, the volume resistivity was 0.47 × 10 ^-5 Ω ‧ m. In other words, the conductive particles 10 of Examples 1 to 4 have a content ratio of Au which is less than one-half of the content of Au of the conductive particles of Comparative Example 4, but the conductive of Examples 1 to 4 The volume resistivity of the particles 10 was less than one-half of that of the conductive particles of Comparative Example 4.

Accordingly, according to the embodiment of the present invention, conductive particles which are less expensive and have sufficiently high conductivity and moisture resistance reliability, and conductive powder containing such conductive particles can be obtained.

The conductive polymer composition according to the embodiment of the present invention contains the conductive powder and the polymer. Further, the polymer is electrically insulating unless otherwise specified. As the polymer, various known polymer materials can be used depending on the application. The polymer material is, for example, a rubber, a thermoplastic resin, a thermosetting resin or a photocurable resin. The conductive polymer composition according to the embodiment of the present invention can be widely used for an anisotropic conductive sheet (ACF), an anisotropic conductive paste (ACP), or the like. The content of the conductive particles can be appropriately set depending on the use, and the volume percentage is about 3% or more and 50% or less, preferably 5% or more and 30% or less.

The conductive particles 10 constituting the above-mentioned conductive powder exhibit ferromagic properties because they have the core 12 mainly composed of Ni. Therefore, in the polymer composition of the embodiment of the present invention, an anisotropic conductive sheet in which conductive particles are arranged in the thickness direction by a magnetic field can be formed as described in Patent Documents 1 to 3. Here, when rubber (or synthetic rubber) is used as the polymer, a pressure-sensitive anisotropic conductive sheet can be obtained. The pressure-sensitive anisotropic conductive sheet exhibits conductivity only when pressure (compression) is applied in the thickness direction of the sheet, and has a property of restoring insulation when the pressurization is stopped. The pressure-sensitive anisotropic conductive sheet is suitably used for temporarily forming an electrical connection in inspection of a wiring board or a semiconductor device. As the rubber, various known rubbers (including synthetic rubber) can be used. From the viewpoints of workability, heat resistance and the like, a hardening type ruthenium rubber is preferred.

ACF or ACP can also be used to form liquid crystal display devices, tablets, Electrical connection in electrical equipment such as mobile phones. In such applications, a thermosetting resin or a photocurable resin is used as the polymer. As the thermosetting resin, for example, various epoxy resins can be used, and as the photocurable resin, an acrylic resin can be used.

(industrial availability)

The present invention is applicable to conductive particles, conductive powders, conductive polymer compositions, and anisotropic conductive sheets.

10‧‧‧Electrical particles

12‧‧‧nuclear (NiP nuclear)

14‧‧‧Pd plating

16‧‧‧Au plating

Claims (9)

A conductive particle having a spherical core containing Ni and P, a Pd plating layer covering the surface of the core, and an Au plating layer covering the surface of the Pd plating layer. The conductive particles according to claim 1, wherein the Pd plating layer is an electroless reduction plating layer. The conductive particles according to claim 1 or 2, wherein the Au plating layer is an electroless substitution plating layer. The conductive particles according to any one of claims 1 to 3, wherein the thickness of the Pd plating layer is larger than the thickness of the Au plating layer, and the thickness of the Au plating layer is 5 nm or more and less than 40 nm. The conductive particles according to any one of claims 1 to 4, wherein the core further comprises Cu and Sn. The conductive particles according to any one of claims 1 to 5, wherein the core has a diameter of 1 μm or more and 100 μm or less. An electroconductive powder comprising the electroconductive particle according to any one of claims 1 to 6, wherein the median diameter d50 in the cumulative volume distribution curve is 3 μm or more and 100 μm or less, and [( D90-d10)/d50]≦0.8. A conductive polymer composition comprising the conductive powder of the seventh aspect of the patent application and a polymer, the polymer rubber, a thermoplastic resin or a thermosetting resin. An anisotropic conductive sheet formed of the conductive polymer composition of the eighth application of the patent application, wherein the conductive particles are arranged in the thickness direction.