JP2007194083A - Conductive powder for anisotropic conductive rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide conductive powder for anisotropic conductive rubber excelling in dispersibility and conductivity. <P>SOLUTION: This conductive powder for the anisotropic conductive rubber containing flake-like conductive coat particles each having a conductive coat layer made of a conductive material on a surface of a core material formed out of a magnetic material is prepared. Since the flake-like conductive coat particles excel, in particular, conductivity as compared with spherical conductive coat particles, and can reduce the thickness of the conductive coat layer, reduction of magnetism of the core material can be suppressed, the conductive coat particles can be precisely arranged by magnetic force, and the pitch of a conductive part can be sufficiently reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive powder for anisotropic conductive rubber used as a constituent material of anisotropic conductive rubber.

  A conductive rubber having electrical anisotropy having electrical conductivity in the thickness direction and insulating properties in the plane direction is called anisotropic conductive rubber. Such anisotropic conductive rubber can be connected between the opposing electrodes and can be connected with high density contacts by simply pressing lightly, making it possible to connect various electronic components. Used as a connector. It is also used in inspection equipment for electric circuits. For example, by using an anisotropic conductive rubber sheet having a conductive portion penetrating in the thickness direction of the electrical insulating sheet, the anisotropic conductive rubber sheet is placed on the inspection substrate, and the conductive portion of the anisotropic conductive rubber sheet is placed. Are connected to electrodes of a surface mount LSI or electronic circuit board, which is an inspection object, and sandwiched between the inspection board and the inspection object, compressed, and electrically connected for inspection.

  As this type of anisotropic conductive rubber, conventionally, as shown in Patent Document 1, anisotropic conductive having a structure having a plurality of conductive portions in which conductive particles are arranged in the thickness direction in an electrically insulating material. A rubber sheet is known (see claim 1 of Patent Document 1). Such an anisotropic conductive rubber sheet is produced by, for example, producing a composition in which conductive particles having magnetism are mixed in an insulating rubber-like polymer, and molding the composition into a sheet shape, and then in the thickness direction. By applying a magnetic field to the conductive particles, the conductive particles are arranged in the thickness direction, and then cured, whereby the particles that become the conductive portions can be held and fixed (see paragraph [0011] of Patent Document 1). Accordingly, the conductive particles of the anisotropically conductive rubber sheet produced in this way are required to have magnetism as well as conductivity, so that the surfaces of metal particles exhibiting magnetism such as nickel, iron, cobalt, etc. are made conductive. Coated particle powder formed by coating an excellent noble metal is generally used (see paragraph [0015] of Patent Document 1).

  In recent years, miniaturization of conductive parts of conductive rubber sheets has been demanded as fine pitches of surface mount LSIs and electronic circuit boards have been increased. Therefore, the conductive particles of the anisotropic conductive rubber sheet are required to be particles that do not easily aggregate as particles that easily form fine conductive portions, that is, particles that are excellent in dispersibility, and spherical particles that are excellent in dispersibility. Particles are increasingly used (see paragraph [0021] of Patent Document 2).

JP-A-10-256701 Japanese Patent Laid-Open No. 11-204176

  However, although spherical coated particles are excellent in dispersibility, they are not the best in terms of conductivity. In particular, it has been found that when a conductive part is formed by arranging conductive particles in the thickness direction of a rubber sheet by magnetic force, it is difficult to obtain a conductive part having excellent conductivity.

  Therefore, the present invention is intended to provide a conductive powder for anisotropic conductive rubber that is excellent in dispersibility and also excellent in conductivity.

  In order to solve such a problem, the present invention provides a conductive powder for anisotropic conductive rubber used as a constituent material of anisotropic conductive rubber, which is a core material made of a material exhibiting magnetism (hereinafter referred to as “magnetic material”). Proposed is a conductive powder for anisotropic conductive rubber containing flaky conductive coat particles provided with a conductive coat layer made of a conductive material (hereinafter referred to as "conductive material") on the surface. .

  The flaky conductive coated particles are superior to the spherical conductive coated particles in that they are superior in conductivity and also ensure dispersibility. Therefore, the conductive pitch of the anisotropic conductive rubber is increased and the fine pitch is increased. It can correspond to. In particular, flaky conductive coating particles can realize excellent conductivity with a small amount of conductive material, compared to spherical conductive coating particles, and thus the thickness of the conductive coating layer can be reduced. . As a result, reduction in magnetism of the core material by the conductive coating layer can be suppressed and high magnetism can be ensured, so that the conductive coating particles are precisely arranged in a predetermined position (for example, in the thickness direction) by magnetic force. Can do. Moreover, since the flake shape, that is, the thickness is extremely thin, the width or area in the surface direction of the conducting portion can be further reduced, and fine pitch can be further increased.

  In the present invention, “flake shape” means a flat shape or a flaky shape having a fixed shape or an indeterminate shape in an arbitrary size and having a remarkably small thickness compared to the size of the shape in a plan view. Meaning.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, although embodiment of this invention is explained in full detail, the scope of the present invention is not limited to the following embodiment.
In this specification, “X to Y” (X and Y are arbitrary numbers) means “X or more and Y or less” unless otherwise specified, and “preferably larger than X, Y It includes the meaning of “smaller”.

The conductive powder of this embodiment is a conductive powder containing flaky conductive coat particles (hereinafter referred to as “flaked conductive coat particles”) as a main component.
In this case, the “main component” is a component that is contained in a proportion that can affect the function of the component, and includes the intention to allow other components to be included within a range that does not interfere with the function of the component. It is. The content ratio of the main component is not particularly limited and depends on the function of the main component, but is preferably 50% by mass or more, particularly 70% by mass or more, and particularly preferably 85% by mass or more.

  The conductive powder of the present embodiment may be composed of only flaky conductive coat particles or may contain spherical conductive coat particles (hereinafter referred to as “spherical conductive coat particles”). By mixing the spherical conductive particles with the flaky conductive coat particles, the flake conductive coat particles can be alleviated from agglomerating in layers, and the dispersibility can be further improved. That is, since the spherical conductive particles enter the gaps between the flaky conductive coat particles and work as spacers or rollers, dispersibility can be improved.

Both the flaky conductive coat particles and the spherical conductive coat particles (also collectively referred to as “conductive coat particles”) are laminated layers having a conductive coat layer made of a conductive material on the surface of a core material made of a magnetic material. Structured particles.
The conductive coat layer may be formed on the outermost surface, and an intermediate layer may be provided between the core material and the conductive coat layer. This intermediate layer may be provided with a catalyst layer made of Sn—Pd catalyst or Pd chloride catalyst, for example, in order to further stabilize the conductive coating layer. However, the present invention is not limited to this.

The core material of the conductive coated particles may be made of a material exhibiting magnetism. For example, metal particles exhibiting magnetism such as nickel, iron, and cobalt, or particles obtained by kneading the magnetic material in inorganic particles such as ceramics or organic particles such as resin can be used. Among them, it is particularly preferable to use magnetic metal particles made of nickel or a nickel alloy as a core material. In addition to excellent magnetism, it also has excellent conductivity.
The core material of the flaky conductive coat particles and the core material of the spherical conductive coat particles may be the same material or different materials.

The composition of the conductive coating layer of the conductive coating particles is not particularly limited as long as it is a conductive composition. For example, a noble metal such as gold, silver, platinum, palladium, or an alloy thereof can be used as a main component. It is preferable to select a material that is difficult to form a solid solution with a core made of metal particles.
In addition, from the viewpoint of magnetism and conductivity, a configuration in which a conductive coating layer made of gold or a gold alloy is formed on the surface of core material particles made of nickel or a nickel alloy can be cited as a preferred example.
The composition of the conductive coat layer of the flaky conductive coat particles and the conductive coat layer of the spherical conductive coat particles are preferably the same. By making the conductive coating layer have the same composition, the electrical conductivity can be further improved.

  The mass ratio of the conductive coat layer in the conductive coat particles, in other words, the mass ratio of the constituent component of the conductive coat layer in the total mass of the conductive coat particles depends on the particle diameter of the core particles, but the flaky conductivity In both the coated particles and the spherical conductive coated particles, the content is preferably 3 to 25% by mass, particularly 4 to 23% by mass, and further preferably 5 to 20% by mass.

The film thickness of the conductive coating layer depends on the composition of the conductive coating layer, but both the flaky conductive coating particles and the spherical conductive coating particles are 0.005 μm to 0.10 μm, particularly 0.005 μm to 0. .05 μm, and particularly preferably 0.005 μm to 0.03 μm. If the film thickness is less than 0.005 μm, it is difficult to obtain desired conductivity, whereas if the film thickness is greater than 0.10 μm, it is difficult to reduce the magnetism of the core material and obtain the desired magnetism.
Moreover, it is preferable that the film thicknesses of the conductive coating layer of the flaky conductive coating particles and the conductive coating layer of the spherical conductive coating particles are substantially the same from the viewpoint of further increasing the conductivity.

(Flake conductive coating particles)
The flaky conductive coat particles are flaky particles having a conductive coat layer on the surface of the core material particles, and preferably have an aspect ratio of 3 to 30. If it is lower than 3, desired conductivity cannot be obtained. On the other hand, if it exceeds 30, the strength of the particles will be insufficient, and it will be destroyed inside the conductive rubber, which is not preferable. From this viewpoint, 5 to 20, particularly 7 to 18, and particularly 8 to 15 are preferable.
As for the particle size of the flaky conductive coating particles, the center particle size (D50) is preferably 20 μm or less. If the aggregated particle size is large, the anisotropic conductivity may be adversely affected. In consideration of the fine pitch, it is more preferably 17 μm or less, and further preferably 13 μm or less.

The aspect ratio refers to the ratio of the major axis diameter to the thickness (major axis diameter / thickness) of each particle.
In the present invention, when “center particle size (D50)” is simply described, it means the center particle size (D50) measured by a laser scattering type particle size distribution analyzer.

(Spherical conductive coated particles)
The spherical conductive coat particle is a spherical particle having a conductive coat layer on the surface of the core particle, and has an aspect ratio of 1.0 to 1.5, particularly 1.0 to 1.4, especially 1. It is preferably 0.0 to 1.3. If the aspect ratio is 1.0 to 1.5, the conductivity can be increased.
The “aspect ratio” refers to the ratio between the longest diameter and the shortest diameter of each particle (longest diameter / shortest diameter).
The average particle size of the number particle size distribution is preferably 1 μm to 20 μm, more preferably 1.5 μm to 18 μm, and even more preferably 2 μm to 15 μm.

The average particle size ratio of the number particle size distribution in the flaky conductive coat particles and the spherical conductive coat particles is (average particle size of flaky conductive coat particles / average particle size of spherical conductive coat particles) = 1.2. Is preferably 10 to 10, more preferably 1.3 to 9, and still more preferably 1.4 to 8.
Here, “the average particle size of the number particle size distribution of the flaky conductive coat particles” means the average particle size of the major axis.

(Conductive powder (mixed powder))
The conductive powder of the present embodiment may be composed only of flaky conductive coat particles, or may be configured by mixing spherical conductive coat particles.
When the spherical conductive coat particles are mixed, it is preferable to adjust so that the content ratio of the flaky conductive coat particles does not become 50% by mass or less. When the content ratio of the flaky conductive coat particles is 50% by mass or less, the conductivity of the flaky conductive coat particles may be lost. Among them, the content ratio of the flaky conductive coat particles is preferably adjusted to 70% by mass or more, and more preferably 85% by mass or more from the viewpoint of suppressing aggregation and maintaining conductivity.

  The particle size of the mixed powder of flaky conductive coat particles and spherical conductive coat particles is preferably 25 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less as the center particle size (D50).

The volume resistivity (: dust resistance) of the conductive powder of the present invention (including the case where the spherical conductive coat particles are included or not included) is the electrical resistance measured in a pressurized state of 10 kN. It is preferably 5 × 10 ⁻⁴ Ω · cm or less. In order to obtain sufficient electrical conductivity stably, it is more preferable that it is 1 × 10 ⁻⁵ Ω · cm or less.

The saturation magnetization of the conductive powder of the present invention (including the case of including or not including spherical conductive coat particles) at a load magnetic field of 796 kA / m is preferably 40 Am ² / kg or more. Increasing the saturation magnetization is suitable for reducing the content of the conductive layer (nonmagnetic component), but if it is extremely reduced, sufficient conductivity cannot be obtained, so the balance between conductivity and saturation magnetization is considered. Then, particularly preferably in the range of 40~52Am ² / kg, inter alia 41~51Am ² / kg, more preferably in the range of particularly 43~51Am ² / kg among them.

  In addition, the electroconductive powder of this embodiment may also contain other components (particles) other than the flaky conductive coat particles and the spherical conductive coat particles as long as the effects of the present invention are not impaired.

(Production method)
Here, a method for producing a conductive powder composed only of flaky conductive coat particles will be described first, and then a method for producing a conductive powder comprising a mixed powder containing spherical conductive coat particles will be described. However, the manufacturing method of the conductive powder of the present invention is not limited to the manufacturing method described below.

  The conductive powder composed only of the flaky conductive coat particles can be produced by forming a conductive coat layer on the surface of the flaky core material particles and dispersing the powder as necessary.

Here, the flaky core material particles have a “major axis diameter / thickness ratio” of 3 to 30, particularly 5 to 20, especially 7 to 18, especially 8 to 8 in accordance with the flaky conductive coat particles. 15 is preferred.
The particle diameter of the flaky core material particles is preferably 1.2 μm to 25 μm, more preferably 1.8 μm to 22 μm, and still more preferably 2.5 μm to 18 μm, as the center particle diameter (D50).
Such flaky core particles can be obtained by a general mechanical processing technique. For example, it can be prepared by putting spherical particles together with glass beads into a dispersion medium and stirring. However, it is not limited to this method.

The method for forming the conductive coating layer on the surface of the core material particles is not particularly limited, but various plating methods can be employed. When the core particle is a metal particle, either a substitution method or a reduction method can be employed. When the core material is non-metallic, it is necessary to adopt a reduction method.
A commercially available plating solution can also be used when the conductive coating layer is plated by a substitution method.
When the conductive coating layer is plated by the reduction method, it is preferable to perform activation by imparting Pd to the surface of the core material.

In addition, it is preferable to use a Sn—Pd catalyst or a Pd chloride catalyst depending on the material of the core material when plating. In addition, the oxide layer on the surface of the core material is obtained by performing a reduction treatment using a reducing agent such as hydrazine or sodium borohydride (SBH) or an acid treatment using an acid such as sulfuric acid before plating. Is preferably removed.
Moreover, when electroless plating is performed, it is preferable to separate the solid and liquid after the treatment and dry in an atmosphere of 50 to 80 ° C.

  In the case where the particles are aggregated when the conductive coating layer is formed on the surface of the core material particles, it is preferable to disperse using an ultrasonic wave, a homogenizer or the like.

Next, a method for producing a conductive powder made of a mixed powder containing flaky conductive coat particles and spherical conductive coat particles will be described.
The conductive powder composed of the mixed powder containing the flaky conductive coat particles and the spherical conductive coat particles is obtained by mixing the flaky core particles and the spherical core particles, and the mixed core particles. It is preferable to manufacture by forming a conductive coating layer on the surface of the film.
If manufactured in this way, the conductive coating layers of the flaky conductive coating particles and the spherical conductive coating particles can be formed with the same composition and the same film thickness. On the other hand, when the conductive coating layer is formed and then mixed, the flaky particles and the spherical particles easily form aggregates, and the flaky conductive coating particles and the spherical conductive coat particles are uniformly mixed. In addition, it becomes difficult to achieve a fine pitch by agglomeration.

The flaky core material particles are the same as in the case where the flaky core material particles are formed only.
On the other hand, the spherical core particles have an aspect ratio of 1.0 to 1.5, particularly 1.0 to 1.4, and particularly 1.0 to 1.3, according to the spherical conductive coat particles. preferable.
The particle diameter of the spherical core particles is preferably 1 μm to 20 μm, more preferably 1.5 μm to 18 μm, still more preferably 2 μm to 15 μm, as the center particle diameter (D50).
Such spherical core particles can be obtained by known methods such as various atomization methods and reduction methods (for example, reducing spherical nickel hydroxide to obtain spherical nickel particles). It is not limited.

  The mixing ratio of the flaky core material particles to the spherical core material particles is blended so that the content ratio of the spherical core material particles is 50% by mass or less, particularly 30% by mass or less, and further 15% by mass or less. It is preferable to do this.

  When the flaky core material particles and the spherical core material particles are mixed, it is preferably added to a dispersion medium, for example, water, and mixed with stirring to form a slurry. In particular, when plating the conductive coating layer by the substitution method, it is preferable to mix and slurry in the catalyst activation treatment when plating the conductive coating layer by the reduction treatment or acid cleaning treatment, or when the conductive coating layer is plated by the reduction method. .

  The method itself for forming the conductive coating layer on the surface of the flaky core material particles and the spherical core material particles can be carried out in the same manner as in the case of only the flaky conductive coating particles. The same applies to the pretreatment for forming the conductive coating layer, but when mixing the spherical core material particles and the flaky core material particles, it is preferable to mix them from the pretreatment stage of the plating treatment. .

(Use)
An anisotropic conductive rubber sheet can be produced as follows using the conductive powder of the present invention.

  The conductive powder of the present invention is mixed in an insulating rubbery polymer to prepare a composition. After the composition is formed into a sheet, a magnetic field is applied in the thickness direction of the sheet to thicken the conductive particles. Arrange in the vertical direction. Next, the rubbery polymer is cross-linked and cured, and at the same time, the conductive particles are fixed, and a conductive portion extending in the thickness direction of the sheet is formed at a predetermined position of the anisotropic conductive rubber sheet. A rubber sheet can be manufactured.

  Under the present circumstances, it is preferable to mix | blend electroconductive powder in the ratio of 30-1000 mass parts with respect to 100 mass parts of rubber-like polymers, especially 50-750 mass parts. If it is smaller than 30 parts by mass, sufficient conductivity cannot be ensured and a good connection function cannot be obtained. On the other hand, when it exceeds 1000 parts by mass, the cured elastomer becomes brittle and it becomes difficult to use it as an anisotropic conductive rubber sheet.

  In addition, as needed, inorganic fillers, such as normal silica powder, colloidal silica, airgel silica, an alumina, can be contained. By including such an inorganic filler, thixotropy when uncured is ensured, viscosity is increased, dispersion stability of conductive particles is improved, and strength of the rubber sheet after curing is improved. be able to.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

<Measurement of aspect ratio>
In the case of flaky particles, a 1200-times magnification photograph was taken with a transmission electron microscope (TEM), the major axis diameter of any 100 particles was measured, and the average major axis diameter (A) was determined. In addition, the measurement sample was filled with an epoxy resin, and the cross section of the powder filled with resin was polished stepwise using a water-resistant sandpaper P400, P800, P1500, and a pure alumina powder 20% slurry, followed by a scanning electron microscope (SEM). ) Was taken 1000 times, the thickness of any 100 particles was measured, and the average thickness (B) was determined. Then, “major axis diameter / thickness ratio (A / B)” was calculated as an aspect ratio from (A) and (B) thus obtained.
In the case of spherical particles, the longest diameter of any 100 particles is measured to determine the average long diameter (A), while the shortest diameter of any 100 particles is measured to determine the average short diameter as described above. The diameter (B) was determined, and the “longest diameter / shortest diameter ratio (A / B)” was calculated as the aspect ratio (A / B).

<Measurement of center particle size (D50)>
Take a small amount of the powder to be measured in a beaker, add 2 or 3 drops of 3% Triton X solution (Kanto Chemical), and mix with the powder, then add 0.1% SN Dispersant 41 solution (San Nopco) 50mL Then, using a ultrasonic disperser TIPφ20 (Nippon Seiki Seisakusho, OUTPUT: 8, TUNING: 5), dispersion treatment was performed for 2 minutes to prepare a measurement sample. The center particle size (D50) of this measurement sample was determined using a laser diffraction / scattering particle size distribution analyzer MT3300 (manufactured by Nikkiso).

<Measurement of saturation magnetization>
Saturation magnetization was measured using a vibrating sample magnetometer VSM-P7 manufactured by Toei Industry Co., Ltd. with a load magnetic field of 796 kA / m.

<Measurement of specific surface area>
The specific surface area was measured by the BET 1-point method with a monosorb manufactured by Yuasa Ionics.

<Measurement of gold content>
The gold content was quantified by ICP after completely dissolving the measurement sample in a strong acid.

<Measurement of powder volume resistivity>
The volume resistivity of the powder, that is, the dust resistance, is 4 probe resistance in a state where 3 g of measurement sample is pressed with a press pressure of 10 kN by Loresta PD-41 type (manufactured by Mitsubishi Chemical Corporation) into a cylindrical pellet having a diameter of 20 mm. Measurement was performed using a measuring instrument Loresta GP (manufactured by Mitsubishi Chemical Corporation).

Example 1
(1) Core material pretreatment Flaky nickel powder composed of flaky nickel particles (major axis diameter: 7 μm, thickness: 1 μm, aspect ratio: 7.0, specific surface area (SSA): 0.59 m ² / g, D50 : 6.2 μm) was put into 500 mL of pure water kept at 40 ° C. and stirred for 5 minutes to make a slurry. Next, 5 g of SBH was added, and the reduction treatment was performed while maintaining stirring for 30 minutes.
Then, after solid-liquid separation with a Buchner funnel and washing with 500 mL of pure water, 100 mL of methanol was added for dehydration treatment to obtain cake-like particles (core material).

(2) Electroless plating treatment 1200 mL of pure water was heated to 80 ° C., 69 mL of an electroless plating solution (Muden Gold) manufactured by Okuno Pharmaceutical Co., Ltd., and potassium cyanide in an amount shown in Table 1 were added.
Next, the entire amount of cake-like particles (core material) obtained above was put into a slurry, and after stirring for 30 minutes, the mixture was solid-liquid separated, washed with 1000 mL of warm pure water, and 100 mL of methanol while being sucked. Then, 100 mL of acetone was sequentially added to perform dehydration treatment. To the obtained cake, 1200 ml of pure water was added, stirred and mixed to make a slurry, and ultrasonic dispersion treatment was performed for 10 minutes using an ultrasonic disperser TIPφ20 (Nippon Seiki Seisakusho, OUTPUT: 8, TUNING: 5). Dehydration treatment was performed. After that, it was transferred to a stainless steel bat, kept in an atmosphere at 70 ° C. for 12 hours and dried to obtain a conductive powder.

Saturation magnetization (Am ² / kg), major axis diameter (μm), thickness (μm), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm) of the obtained conductive powder The aspect ratio and the film thickness of the conductive coating layer were calculated and shown in Table 2.

The film thickness (A) of the conductive coat layer was calculated by the following calculation formula.
Film thickness (A) = {coat metal content / (coat metal specific gravity × 100)} / {core specific surface area × (1-coat metal content / 100)}

(Example 2)
Example 1 except that the same flake-like nickel particles as in Example 1 were used as core particles and the conductive coating layer was made thicker (in other words, the amount of potassium gold cyanide shown in Table 1 was added). 1 was performed to obtain a conductive powder.
Saturation magnetization (Am ² / kg), major axis diameter (μm), thickness (μm), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm) of the obtained conductive powder The aspect ratio and the film thickness of the conductive coating layer were calculated and shown in Table 2.

(Example 3)
Example 1 except that the same flake-like nickel particles as in Example 1 were used as core material particles, and the conductive coating layer was made thinner (in other words, the amount of potassium gold cyanide shown in Table 1 was added). The same treatment was performed to obtain a conductive powder.
Saturation magnetization (Am ² / kg), major axis diameter (μm), thickness (μm), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm) of the obtained conductive powder The aspect ratio and the film thickness of the conductive coating layer were calculated and shown in Table 2.

Example 4
Flakes of nickel particles (major axis diameter: 13 μm, thickness: 1 μm, aspect ratio: 13.0, specific surface area (SSA): 0.35 m ^{2 /} g, D50: 11.3 μm) different from Example 1 Except for the use as material particles, the same treatment as in Example 1 was performed to obtain a conductive powder.
Saturation magnetization (Am ² / kg), major axis diameter (μm), thickness (μm), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm) of the obtained conductive powder The aspect ratio and the film thickness of the conductive coating layer were calculated and shown in Table 2.

(Example 5)
Flaky nickel particles (major axis diameter: 4 μm, thickness: 1 μm, aspect ratio: 4.0, specific surface area (SSA): 1.21 m ^{2 /} g, D50: 2.1 μm) different from those of Example 1 Except for the use as material particles, the same treatment as in Example 1 was performed to obtain a conductive powder.
Saturation magnetization (Am ² / kg), major axis diameter (μm), thickness (μm), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm) of the obtained conductive powder The aspect ratio and the film thickness of the conductive coating layer were calculated and shown in Table 2.

(Example 6)
(1) Core material pretreatment 27 g of flaky nickel powder (major axis diameter: 7 μm, thickness: 1 μm, aspect ratio: 7.0, specific surface area (SSA): 0.59 m ^{2 /} g, D50: 6.2 μm) 3 g of spherical nickel powder composed of spherical nickel particles (aspect ratio: 1.2, D50: 6.9 μm) was put into 500 mL of pure water kept at 40 ° C. and stirred for 5 minutes to make a slurry. . Next, 5 g of SBH was added, and the reduction treatment was performed while maintaining stirring for 30 minutes. Then, after separating into solid and liquid with a Buchner funnel and washing with 500 mL of pure water, 100 mL of methanol was added and dehydration was performed to obtain cake-like mixed particles (core material). The moisture of the obtained cake was measured and weighed 30 g in terms of dry powder.

(2) Electroless plating treatment 1200 mL of pure water was heated to 80 ° C., 69 mL of an electroless plating solution (Muden Gold) manufactured by Okuno Pharmaceutical Co., Ltd., and potassium cyanide in an amount shown in Table 1 were added.
Next, the cake-like mixed particles (core material) obtained above are put into a slurry, and after stirring for 30 minutes, the mixture is solid-liquid separated, washed with 1000 mL of warm pure water, and methanol while sucking. 100 mL and 100 mL of acetone were sequentially added to perform dehydration treatment. To the obtained cake, 1200 ml of pure water was added, stirred and mixed to make a slurry, and ultrasonic dispersion treatment was performed for 10 minutes using an ultrasonic disperser TIPφ20 (Nippon Seiki Seisakusho, OUTPUT: 8, TUNING: 5). Dehydration treatment was performed. After that, it was transferred to a stainless steel bat, kept in an atmosphere at 70 ° C. for 12 hours and dried to obtain a conductive powder.

Saturation magnetization (Am ² / kg), major axis diameter (μm), thickness (μm), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm) of the obtained conductive powder The aspect ratio and the film thickness of the conductive coating layer were calculated and shown in Table 2.

The film thickness (A) of the conductive coat layer was calculated by the following calculation formula.
Film thickness (A) = {coat metal content / (coat metal specific gravity × 100)} / {core specific surface area × (1-coat metal content / 100)}
The “core material specific surface area” in the above formula is an arithmetic average value obtained by multiplying the core material specific surface areas of the core material flaky particles and the core material spherical particles by the mass ratio.

(Example 7)
A conductive powder was obtained by performing the same treatment as in Example 6 except that the amount of the core material mixed was 24 g of flaky nickel powder and 6 g of spherical nickel powder.
Saturation magnetization (Am ² / kg), major axis diameter (μm), thickness (μm), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm) of the obtained conductive powder The aspect ratio and the film thickness of the conductive coating layer were calculated and shown in Table 2.

(Example 8)
A conductive powder was obtained by performing the same treatment as in Example 6 except that a spherical nickel powder having an aspect ratio of 1.2 and a D50 of 3.0 μm was used as the spherical nickel powder.
Saturation magnetization (Am ² / kg), major axis diameter (μm), thickness (μm), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm) of the obtained conductive powder The aspect ratio and the film thickness of the conductive coating layer were calculated and shown in Table 2.

Example 9
Example 1 except that the same flake-like nickel particles as in Example 1 were used as core particles and the conductive coating layer was made thicker (in other words, the amount of potassium gold cyanide shown in Table 1 was added). 1 was performed to obtain a conductive powder.
Saturation magnetization (Am ² / kg), major axis diameter (μm), thickness (μm), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm) of the obtained conductive powder The aspect ratio and the film thickness of the conductive coating layer were calculated and shown in Table 2.

(Example 10)
Example 1 except that the same flake-like nickel particles as in Example 1 were used as core particles and the conductive coating layer was made thicker (in other words, the amount of potassium gold cyanide shown in Table 1 was added). 1 was performed to obtain a conductive powder.
Saturation magnetization (Am ² / kg), major axis diameter (μm), thickness (μm), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm) of the obtained conductive powder The aspect ratio and the film thickness of the conductive coating layer were calculated and shown in Table 2.

(Comparative Example 1)
The same treatment as in Example 1 was performed except that spherical nickel powder (aspect ratio: 1.2, specific surface area (SSA): 0.11 m ^{2 /} g, D50: 7.0 μm) was used as the core material particles, A conductive powder was obtained.
The obtained conductive powder was measured for saturation magnetization (Am ² / kg), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm), and the film thickness of the conductive coating layer. Is shown in Table 2.

(Comparative Example 2)
Comparative Example 1 except that the same spherical nickel particles as in Comparative Example 1 were used as core particles and the conductive coating layer was made thicker (in other words, the amount of potassium gold cyanide added in Table 1 was added). The same treatment was performed to obtain a conductive powder.
The obtained conductive powder was measured for saturation magnetization (Am ² / kg), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm), and the film thickness of the conductive coating layer. Is shown in Table 2.

(Comparative Example 3)
Except not performing a dispersion process, the process similar to the comparative example 1 was performed and the electroconductive powder was obtained.
The obtained conductive powder was measured for saturation magnetization (Am ² / kg), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm), and the film thickness of the conductive coating layer. Is shown in Table 2.

(Comparative Example 4)
Comparative Example 1 except that the same spherical nickel particles as in Comparative Example 1 were used as the core material particles and the conductive coating layer was made thinner (in other words, the amount of potassium gold cyanide shown in Table 1 was added). The same treatment was performed to obtain a conductive powder.
The obtained conductive powder was measured for saturation magnetization (Am ² / kg), specific surface area (m ² / g), D50 (μm) and volume resistivity (Ω · cm), and the film thickness of the conductive coating layer. Is shown in Table 2.

(Discussion)
FIG. 1 is a graph showing the relationship between the film thickness of the conductive coating layer and the volume resistivity (specific resistance) of the conductive powders obtained in the examples and comparative examples.
As shown in FIG. 1, in the conductive powder containing a large amount of flaky conductive coat particles, the volume resistivity (specific resistance) decreases in proportion to the film thickness of the conductive coat layer. It was confirmed that if the conductive powder contains a lot of particles, sufficient conductivity can be obtained even if the conductive coat layer (gold coat layer) is thin.
Further, in the case of conductive powder containing a large amount of flaky conductive coat particles, the conductivity is very good when the film thickness is large, and the effect is clear compared with the comparative example consisting of spherical conductive coat particles. It was. Furthermore, in the case of conductive powder containing a large amount of flaky conductive coat particles, an extremely thin film thickness is sufficient to obtain a volume resistivity (specific resistance) equivalent to that of the comparative example comprising spherical conductive coat particles. I understand.

In the case of a conductive powder containing a large amount of flaky conductive coat particles, the volume resistivity can be sufficiently obtained without increasing the thickness of the conductive coat layer even in the case of a powder consisting of particles having a very small particle size as in Example 5. It was found that can be lowered. On the other hand, in the case of the comparative example made of spherical conductive coat particles, it can be seen that the volume resistivity is high even if the film thickness is increased.
As a result, the conductive coated particles have a flaky shape, a conductive coating layer made of gold is formed on the surface of the particles, and magnetic metal particles are selected as the core particles. It has been found that conductivity that cannot be obtained with conductive powder made of coated particles can be obtained.
Moreover, when Example 1 (only flakes) is compared with Examples 6-8 (flakes and spherical mixture), Examples 6-8 (flakes and spherical mixtures) contain spherical conductive coat particles. Therefore, it was found that the volume resistivity is slightly high, but the dispersibility is good.

Compared with the Examples, Comparative Example 1 consisting only of spherical conductive coat particles had good dispersibility but was inferior in volume resistivity.
Although Comparative Example 2 shows the same volume resistivity as Example 5, it is necessary to increase the amount of gold used to obtain sufficient conductivity, and the saturation magnetization is insufficient. It turns out that it is not economical.
Further, Comparative Example 3 does not perform a dispersion treatment with respect to Comparative Example 1, in other words, the particles are held in an agglomerated state. For anisotropic conductive rubbers having a narrow pitch, it is difficult to obtain sufficient anisotropy, which is not preferable.
In Comparative Example 4, the film thickness of the conductive coating layer was set to the same level as in Example 2 or the like, but the conductivity was insufficient.

  In Example 9, the thickness of the conductive coating layer was made equivalent to that of Comparative Example 1, but the gold content was very high, and as a result, the conductivity was very good. Instead, the magnetism is low.

It is the graph which showed the relationship between the film thickness of a conductive coat layer, and volume resistivity (specific resistance) about the conductive powder obtained by the Example and the comparative example.

Claims (6)

  A conductive powder for anisotropic conductive rubber used as a constituent material for anisotropic conductive rubber, comprising a conductive coating layer made of a material exhibiting conductivity on the surface of a core material made of a material exhibiting magnetism Conductive powder for anisotropic conductive rubber, comprising conductive conductive particles in the form of particles.   The conductive powder for anisotropic conductive rubber according to claim 1, comprising flaky conductive coating particles.   The flaky conductive coated particles and spherical conductive coated particles provided with a conductive coated layer made of a conductive material on the surface of a core made of a magnetic material. Conductive powder for anisotropic conductive rubber.   4. The anisotropic conductive material according to claim 1, wherein the conductive coated particle comprises a conductive coating layer made of gold or a gold alloy on a surface of a metal particle exhibiting magnetism. 5. Conductive powder for rubber.   5. The conductive powder for anisotropic conductive rubber according to claim 1, wherein a mass ratio of the conductive coat layer to the conductive coat particles is 3 to 25 mass%. The conductive powder for anisotropic conductive rubber according to any one of claims 1 to 5, wherein the film thickness of the conductive coating layer is 0.005 µm to 0.10 µm.

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