JP2020174051A - Conductive particle, conductive material and connection structure - Google Patents

Abstract

To provide a conductive particle that can reduce connection resistance when electrically connecting between electrodes, and can improve connection reliability between electrodes at high temperature.SOLUTION: A conductive particle has a base particle, a first conductive layer, and a gold layer containing gold, the first conductive layer being disposed on the surface of the base particle, the gold layer being disposed on the external surface of the first conductive layer, and the gold layer having a crystallite size of more than 15 nm to 300 nm or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to conductive particles having base particles and a conductive layer arranged on the surface of the base particles. The present invention also relates to a conductive material and a connecting structure using the above conductive particles.

Anisotropic conductive materials such as anisotropic conductive pastes and anisotropic conductive films are widely known. In the anisotropic conductive material, a plurality of conductive particles are dispersed in the binder resin.

In order to obtain various connection structures, the anisotropic conductive material may be used, for example, for connecting a flexible printed circuit board and a glass substrate (FOG (Film on Glass)) or connecting a semiconductor chip and a flexible printed circuit board (COF (COF). It is used for Chip on Film)), connection between a semiconductor chip and a glass substrate (COG (Chip on Glass)), and connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)).

As an example of the above conductive particles, Patent Document 1 below discloses conductive particles including a nickel layer and a gold layer formed on the nickel layer and having an average thickness of 300 Å or less. ing. In these conductive particles, the gold layer is the outermost layer. Further, in these conductive particles, the element composition ratio (Ni / Au) of nickel and gold on the surface of the conductive particles by X-ray photoelectron spectroscopy is 0.4 or less. In the example of Patent Document 1, a nickel layer containing nickel and phosphorus is formed, and a gold layer having a thickness of 15 nm or more and 28 nm or less is formed.

In the examples of Patent Document 2 below, conductive particles in which a nickel plating layer is formed on the surface of crosslinked polystyrene particles and a gold plating layer is formed on the outer surface of the nickel plating layer are disclosed. There is. In the example of Patent Document 2, a nickel layer containing nickel and phosphorus is formed, and a gold layer having a thickness of 20 nm is formed.

Patent Document 3 below discloses conductive particles including core particles, a Ni plating layer, a noble metal plating layer, and a rust preventive film. The Ni plating layer covers the core particles and contains Ni. The noble metal plating layer covers at least a part of the Ni plating layer and contains at least one of Au and Pd. The rust preventive film covers at least one of the Ni plating layer and the noble metal plating layer, and contains an organic compound.

JP-A-2009-102731 JP-A-2009-280790 Japanese Unexamined Patent Publication No. 2013-20721

When conventional conductive particles as described in Patent Documents 1 to 3 are used to electrically connect the electrodes to obtain a connection structure, the connection resistance may increase. Further, when conductive particles exposed to a high temperature are used, or when a connection structure using the conductive particles is exposed to a high temperature, there is a problem that the connection resistance tends to increase.

An object of the present invention is to provide conductive particles capable of lowering the connection resistance and increasing the connection reliability between the electrodes at a high temperature when the electrodes are electrically connected. is there. Another object of the present invention is to provide a conductive material and a connecting structure using the above conductive particles.

According to a broad aspect of the present invention, the substrate particles, the first conductive layer, and the gold layer containing gold are provided, and the first conductive layer is arranged on the surface of the substrate particles. Provided are conductive particles in which the gold layer is arranged on the outer surface of the first conductive layer, and the crystallite size in the gold layer exceeds 15 nm and is 300 nm or less.

In certain aspects of the conductive particles according to the present invention, the first conductive layer comprises nickel, copper, tungsten or molybdenum.

In certain aspects of the conductive particles according to the present invention, the first conductive layer is a nickel layer containing nickel.

In a particular aspect of the conductive particles according to the present invention, the first conductive layer is a nickel layer containing nickel and phosphorus.

In certain aspects of the conductive particles according to the present invention, the thickness of the gold layer is preferably 30 nm or less, and in other specific aspects, the thickness of the gold layer is less than 15 nm.

In a specific aspect of the conductive particles according to the present invention, the outer surface of the gold layer is rust-proofed.

In a specific aspect of the conductive particles according to the present invention, the outer surface of the gold layer is rust-proofed with a compound having an alkyl group having 6 to 22 carbon atoms.

In a specific aspect of the conductive particles according to the present invention, the outer surface of the gold layer is rust-proofed with a phosphorus-free compound.

In a specific aspect of the conductive particles according to the present invention, the nickel layer contains nickel and phosphorus, and phosphorus is more on the gold layer side than on the base particle side in the thickness direction of the nickel layer. It is unevenly distributed so that there are many.

In certain aspects of the conductive particles according to the present invention, the conductive particles have a plurality of protrusions on the outer surface of the gold layer.

In certain aspects of the conductive particles according to the present invention, the conductive particles raise the outer surface of the gold layer so as to form a plurality of the protrusions inside or inside the gold layer. It has multiple core materials.

In a specific aspect of the conductive particles according to the present invention, the Mohs hardness of the material of the core material is 5 or more.

In a specific aspect of the conductive particles according to the present invention, the surface area of the portion having the protrusion is 30% or more in the total surface area of the outer surface of the gold layer of 100%.

In certain aspects of the conductive particles according to the present invention, the conductive particles include an insulating material disposed on the outer surface of the gold layer.

According to a broad aspect of the present invention, there is provided a conductive material containing the above-mentioned conductive particles and a binder resin.

According to a broad aspect of the present invention, a first connection target member having a first electrode on the surface, a second connection target member having a second electrode on the surface, the first connection target member, and the above. It is provided with a connecting portion connecting the second connection target member, and the connecting portion is formed of the above-mentioned conductive particles or a conductive material containing the conductive particles and a binder resin. Provided is a connecting structure in which the first electrode and the second electrode are electrically connected by the conductive particles.

The conductive particles according to the present invention include base particles, a first conductive layer, and a gold layer containing gold, and the first conductive layer is arranged on the surface of the base particles. Since the gold layer is arranged on the outer surface of the first conductive layer and the crystallite size in the gold layer exceeds 15 nm and is 300 nm or less, the conductive particles according to the present invention can be used. When the electrodes are electrically connected to each other, the connection resistance can be lowered and the connection reliability between the electrodes can be improved at a high temperature.

FIG. 1 is a cross-sectional view showing conductive particles according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view showing conductive particles according to a second embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing a connection structure using conductive particles according to the first embodiment of the present invention.

The details of the present invention will be described below.

(Conductive particles)
As a result of investigating the problem that the connection resistance tends to increase when the conductive particles exposed to a high temperature are used or the connection structure using the conductive particles is exposed to a high temperature, the present inventors have investigated. It has been found that the main cause is the precipitation of metallic substances such as nickel in the inner layer of the noble metal layer which is the surface layer of the conductive layer. Then, as a means for suppressing the precipitation of the above-mentioned metallic substance, those skilled in the art try to coat the noble metal in the outer layer in a dense state, but by daringly adopting a relatively large crystallite size, the above-mentioned problem is solved. I found out to do.

The conductive particles according to the present invention include base particles, a first conductive layer, and a gold layer containing gold (second conductive layer). The first conductive layer is arranged on the surface of the base particles. The gold layer is arranged on the outer surface of the first conductive layer.

In the conductive particles according to the present invention, the gold layer has a crystal structure, and the crystallite size in the gold layer exceeds 15 nm and is 300 nm or less.

By adopting the above-described configuration of the conductive particles according to the present invention, the connection resistance can be lowered when the electrodes are electrically connected by using the conductive particles according to the present invention. Further, the connection reliability at high temperature can be improved. Further, the variation in connection resistance can be reduced and the connection reliability can be improved.

Further, when the inner conductive layer contains nickel, nickel is easily corroded. Therefore, when nickel is deposited, the connection resistance between the electrodes is likely to increase. In the present invention, when the first conductive layer contains nickel, an increase in connection resistance can be sufficiently suppressed.

In the present invention, it is possible to suppress an increase in connection resistance when a connection structure is produced by using conductive particles that have been stored for a long period of time at a high temperature or the like. Further, even when the connection structure is stored for a long period of time at a high temperature or the like, an increase in connection resistance can be suppressed. For example, the connection resistance is unlikely to increase even at a high temperature of 90 ° C. or higher.

In the conductive particles according to the present invention, since the crystallite size in the gold layer is relatively large, the crystal gap in the gold layer is narrowed, and as a result, the metal in the first conductive layer is deposited on the outer gold layer. Is presumed to be suppressed.

The crystallite size can be measured using an X-ray diffractometer. Examples of the X-ray diffractometer include "RINT2500VHF" manufactured by Rigaku Denki Co., Ltd.

The crystallite size is represented by the following formula (1).

Crystalline size (nm) = K · λ / (β · cos θ)… Equation (1)
K: Scherrer constant λ: Wavelength of X-ray tube used β: Diffraction line spread due to crystallite size θ: Diffraction angle 2θ / θ

As a method for increasing the crystallite size in the gold layer above the above lower limit and below the above upper limit, a method for controlling the gold concentration in the plating solution, a method for controlling the temperature of the plating solution, and a method for adjusting metallic crystals in the plating solution. Examples thereof include a method of adding an agent and a method of adding a reducing agent in the plating solution. By these methods, it can be achieved that the crystallite size exceeds the above lower limit and becomes equal to or less than the above upper limit. In particular, the method of adding a reducing agent is effective in coarsening the crystallite size in the gold layer.

Examples of the above-mentioned reducing agent include formalin, formic acid, oxalic acid, hydrazine monohydrate, sodium hypophosphate, dimethylamine borane, sodium borohydride, potassium borohydride and the like. The reducing agent is preferably dimethylamine borane.

The thickness of the gold layer is preferably 30 nm or less, and preferably less than 15 nm.

When the thickness of the gold layer exceeds 30 nm, the connection resistance between the electrodes and the connection reliability between the electrodes at high temperature do not matter so much, but when the thickness of the gold layer is 30 nm or less, the electrode Connection resistance between electrodes and connection reliability between electrodes at high temperatures can be major issues. Further, when the thickness of the gold layer is 15 nm or more, even if the connection resistance between the electrodes and the connection reliability between the electrodes at a high temperature do not matter so much, the thickness of the gold layer is less than 15 nm. The connection resistance between the electrodes and the connection reliability between the electrodes at a high temperature may become a big problem. In the present invention, even if the thickness of the gold layer is 30 nm or less and the thickness of the gold layer is less than 15 nm, the crystallite size of the gold layer exceeds the lower limit and is equal to or less than the upper limit. The connection resistance between the electrodes can be lowered, and the connection reliability between the electrodes can be further improved at a high temperature.

In the conductive particles according to the present invention, it is preferable that the outer surface of the gold layer is rust-proofed. When the outer surface of the gold layer is rust-proofed, it is possible to suppress an increase in connection resistance when a connection structure is produced using conductive particles that have been stored for a long period of time at high temperatures. it can. Further, even when the connection structure is stored for a long period of time at a high temperature or the like, an increase in connection resistance can be suppressed. In particular, when the outer surface of the gold layer is rust-proofed, even if the thickness of the gold layer is thin and the first conductive layer (nickel layer or the like) is inside the gold layer, the connection is made. The increase in resistance can be suppressed. Further, if the thickness of the gold layer is considerably thin, the first conductive layer (nickel layer or the like) may be partially exposed due to the presence of pinholes or the like in the conductive particles. Even if the nickel layer is partially exposed, if the outer surface of the gold layer is rust-proofed, an increase in connection resistance can be suppressed.

The conductive particles can be obtained, for example, by arranging the first conductive layer (nickel layer or the like) on the surface of the base material particles and on the outer surface of the first conductive layer (nickel layer or the like). It can be obtained through the process of arranging the gold layer. Further, the conductive particles provided with the rust preventive film can be obtained through a step of rust preventive treatment on the outer surface of the gold layer.

Hereinafter, the present invention will be clarified by explaining specific embodiments and examples of the present invention with reference to the drawings. In the referenced drawings, the size and thickness are appropriately changed from the actual size and thickness for convenience of illustration.

FIG. 1 is a cross-sectional view showing conductive particles according to the first embodiment of the present invention.

As shown in FIG. 1, the conductive particle 1 includes a base particle 2, a nickel layer 3 (first conductive layer), and a gold layer 4. The nickel layer 3 contains nickel. The gold layer 4 contains gold. The crystallite size in the gold layer 4 exceeds the above lower limit and is equal to or less than the above upper limit. The nickel layer 3 and the gold layer 4 are conductive layers. The gold layer 4 is the outermost layer of the conductive layer. In the conductive particles 1, a multi-layered conductive layer is formed. Although the nickel layer 3 is adopted in this embodiment and the embodiment described later, a first conductive layer containing a metal other than nickel may be adopted instead of the nickel layer 3.

The nickel layer 3 is arranged on the surface of the base particle 2. A nickel layer 3 is arranged between the base particle 2 and the gold layer 4. The gold layer 4 is arranged on the outer surface of the nickel layer 3. The conductive particles 1 are coated particles in which the surface of the base particle 2 is coated with the nickel layer 3 and the gold layer 4.

Although not shown, the outer surface of the gold layer 4 is rust-proofed. Therefore, the conductive particles 1 are provided with a rust preventive film on the outer surface of the gold layer 4.

The conductive particles 1 do not have a core substance. The conductive particles 1 have no protrusions on the conductive surface. The conductive particles 1 are spherical. The nickel layer 3 and the gold layer 4 have no protrusions on their surfaces. As described above, the conductive particles according to the present invention do not have to have conductive protrusions and may be spherical. Further, the conductive particles 1 do not have an insulating substance. However, the conductive particles 1 may have an insulating substance arranged on the surface of the gold layer 4.

Further, the nickel layer 3 is directly laminated on the surface of the base particle 2 in the conductive particle 1. Another conductive layer may be arranged between the base particle 2 and the nickel layer 3. The nickel layer 3 may be arranged on the surface of the base particle 2 via another conductive layer.

FIG. 2 is a cross-sectional view showing conductive particles according to a second embodiment of the present invention.

The conductive particles 21 shown in FIG. 2 include base particles 2, a nickel layer 22, a gold layer 23, a core substance 24, and an insulating substance 25. The nickel layer 22 contains nickel. The crystallite size in the gold layer 23 is not less than the above lower limit and not more than the above upper limit. The nickel layer 22 is arranged on the surface of the base particle 2. The gold layer 23 is arranged on the outer surface of the nickel layer 22.

Although not shown, the outer surface of the gold layer 23 is rust-proofed. Therefore, the conductive particles 21 are provided with a rust preventive film on the outer surface of the gold layer 23.

The conductive particles 21 have protrusions 21a on the conductive surface. There are a plurality of protrusions 21a. The nickel layer 22 and the gold layer 23 have a plurality of protrusions 22a and 23a on the outer surface. A plurality of core substances 24 are arranged on the surface of the base particle 2. The plurality of core materials 24 are embedded in the nickel layer 22 and the gold layer 23. The core material 24 is arranged inside the protrusions 21a, 22a, and 23a. The nickel layer 22 and the gold layer 23 are coated with a plurality of core substances 24. The outer surfaces of the nickel layer 22 and the gold layer 23 are raised by the plurality of core materials 24, and protrusions 21a, 22a, and 23a are formed. As described above, the conductive particles according to the present invention may have protrusions on the conductive surface. The conductive particles according to the present invention may have protrusions on the outer surface of the conductive layer. Further, the conductive particles according to the present invention may not have protrusions on the outer surface of the first conductive layer (nickel layer or the like) and may have protrusions on the outer surface of the gold layer. The conductive particles according to the present invention may include a plurality of core substances in which the outer surface of the gold layer is raised so as to form a plurality of protrusions inside or inside the gold layer. The core material may be located inside the first conductive layer or may be located outside the first conductive layer.

The conductive particles 21 have an insulating material 25 arranged on the outer surface of the gold layer 23. At least a part of the outer surface of the gold layer 23 is covered with the insulating material 25. The insulating substance 25 is formed of an insulating material and is an insulating particle. As described above, the conductive particles according to the present invention may have an insulating substance arranged on the outer surface of the gold layer.

The details of the base particles and the conductive layer will be described below.

[Base particles]
Examples of the base material particles include resin particles, inorganic particles other than metal particles, organic-inorganic hybrid particles, and metal particles. The base material particles are preferably base particles excluding metal particles, and more preferably resin particles, inorganic particles excluding metal particles, or organic-inorganic hybrid particles. The base material particles may be core-shell particles.

The base material particles are more preferably resin particles or organic-inorganic hybrid particles, and may be resin particles or organic-inorganic hybrid particles. The use of these preferred substrate particles results in more suitable conductive particles due to the electrical connection between the electrodes.

When connecting the electrodes using the conductive particles, the conductive particles are placed between the electrodes and then pressure-bonded to compress the conductive particles. When the base material particles are resin particles or organic-inorganic hybrid particles, the conductive particles are easily deformed during the pressure bonding, and the contact area between the conductive particles and the electrode becomes large. Therefore, the connection resistance between the electrodes becomes even lower.

Various organic substances are preferably used as the resin for forming the resin particles. Examples of the resin for forming the resin particles include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene and polybutadiene; acrylic resins such as polymethylmethacrylate and polymethylacrylate; poly. Alkylene terephthalate, polycarbonate, polyamide, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polysulfone, polyphenylene Polymers obtained by polymerizing one or more of various polymerizable monomers having an oxide, polyacetal, polyimide, polyamideimide, polyether ether ketone, polyether sulfone, and ethylenically unsaturated group, etc. Can be mentioned. Since resin particles having arbitrary physical properties at the time of compression suitable for a conductive material can be designed and synthesized, and the hardness of the base material particles can be easily controlled within a suitable range, a resin for forming the resin particles. Is preferably a polymer obtained by polymerizing one or more polymerizable monomers having a plurality of ethylenically unsaturated groups.

When the resin particles are obtained by polymerizing a monomer having an ethylenically unsaturated group, the monomer having an ethylenically unsaturated group includes a non-crosslinkable monomer and a crosslinkable simple monolith. A metric is mentioned.

Examples of the non-crosslinkable monomer include styrene-based monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth) acrylic acid, maleic acid, and maleic anhydride; and methyl ( Meta) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) Alkyl (meth) acrylates such as meta) acrylate and isobornyl (meth) acrylate; oxygen atoms such as 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, polyoxyethylene (meth) acrylate and glycidyl (meth) acrylate. Contains (meth) acrylates; nitrile-containing monomers such as (meth) acrylonitrile; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, and propyl vinyl ether; acid vinyl esters such as vinyl acetate, vinyl butyrate, vinyl laurate, vinyl stearate, etc. Classes: unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene; halogen-containing monomers such as trifluoromethyl (meth) acrylate, pentafluoroethyl (meth) acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene. Can be mentioned.

Examples of the crosslinkable monomer include tetramethylol methanetetra (meth) acrylate, tetramethylol methanetri (meth) acrylate, tetramethylol methanedi (meth) acrylate, trimethyl propanetri (meth) acrylate, and dipenta. Elythritol hexa (meth) acrylate, dipenta erythritol penta (meth) acrylate, glycerol tri (meth) acrylate, glycerol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) Polyfunctional (meth) acrylates such as acrylates, (poly) tetramethylene glycol di (meth) acrylates, 1,4-butanediol di (meth) acrylates; triallyl (iso) cyanurate, triallyl trimellitate, divinylbenzene, Examples thereof include silane-containing monomers such as diallyl phthalate, diallyl acrylamide, diallyl ether, γ- (meth) acryloxipropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane.

The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group by a known method. Examples of this method include a method of suspension polymerization in the presence of a radical polymerization initiator, a method of swelling a monomer together with a radical polymerization initiator using non-crosslinked seed particles, and the like.

When the base material particles are inorganic particles other than metal particles or organic-inorganic hybrid particles, examples of the inorganic material for forming the base material particles include silica, alumina, barium titanate, zirconia, and carbon black. .. It is preferable that the inorganic substance is not a metal. The particles formed of the silica are not particularly limited, but for example, after hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, firing is performed if necessary. Examples include particles obtained by doing so. Examples of the organic-inorganic hybrid particles include organic-inorganic hybrid particles formed of a crosslinked alkoxysilyl polymer and an acrylic resin.

The organic-inorganic hybrid particles are preferably core-shell type organic-inorganic hybrid particles having a core and a shell arranged on the surface of the core. It is preferable that the core is an organic core. It is preferable that the shell is an inorganic shell. From the viewpoint of effectively lowering the connection resistance between the electrodes, the base particle is preferably an organic-inorganic hybrid particle having an organic core and an inorganic shell arranged on the surface of the organic core.

Examples of the material for forming the organic core include the resin for forming the resin particles described above.

Examples of the material for forming the inorganic shell include the above-mentioned inorganic substances for forming the base particles. The material for forming the inorganic shell is preferably silica. The inorganic shell is preferably formed by forming a metal alkoxide into a shell-like material by a sol-gel method on the surface of the core and then firing the shell-like material. The metal alkoxide is preferably a silane alkoxide. The inorganic shell is preferably formed of silane alkoxide.

When the base material particles are metal particles, examples of the metal for forming the metal particles include silver, copper, nickel, silicon, gold, and titanium. However, it is preferable that the base material particles are not metal particles.

The particle size of the base particles is preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 2 μm or more, preferably 5 μm or less, and more preferably 3 μm or less. When the particle diameter of the base material particles is not less than the above lower limit and not more than the above upper limit, small conductive particles can be obtained even if the distance between the electrodes is small and the thickness of the conductive layer is increased.

The particle size of the base material particles indicates the diameter when the base material particles are spherical, and indicates the maximum diameter when the base material particles are not spherical.

[Conductive layer]
The conductive particles have a first conductive layer as the conductive layer. Examples of the metal in the first conductive layer include nickel, palladium, copper, tungsten, molybdenum, cobalt, platinum, ruthenium, iridium, chromium and titanium. The point that precipitation is effectively suppressed by the gold layer described later, the point that the gold layer described later can be uniformly precipitated to cover the first conductive layer, and the adhesion between the gold layer described later and the first conductive layer is high. From the viewpoint of excellent hardness of the first conductive layer, the first conductive layer preferably contains nickel, copper, tungsten or molybdenum, and the first conductive layer is preferably a nickel layer containing nickel. .. The first conductive layer preferably contains nickel and copper, tungsten or molybdenum.

The nickel layer includes not only the case where only nickel is used as the metal but also the case where nickel and another metal are used. The nickel layer may be a nickel alloy layer.

From the viewpoint of further lowering the connection resistance between the electrodes, the nickel layer preferably contains phosphorus or boron, and preferably contains copper, tungsten or molybdenum. In this case, one or more of phosphorus and boron can be used for the nickel layer, and one or more of copper, tungsten and molybdenum can be used. The nickel layer preferably contains tungsten or molybdenum, and more preferably tungsten, because the conductive layer and the protrusions are effectively hardened. The harder the conductive layer and protrusions, the easier it is for the oxide film to be effectively removed.

Metals other than nickel in the nickel layer include silver, copper, platinum, zinc, iron, tin, lead, aluminum, cobalt, indium, palladium, chromium, titanium, antimony, bismuth, tarium, germanium, cadmium, silicon, and tungsten. , Molybdenum and tin-doped indium oxide (ITO) and the like. Only one of these metals may be used, or two or more of these metals may be used in combination.

The nickel layer preferably contains nickel as a main metal. The nickel content is preferably 50% by weight or more in 100% by weight of the entire nickel layer. In 100% by weight of the entire nickel layer, the nickel content is preferably 65% by weight or more, more preferably 80% by weight or more, and further preferably 90% by weight or more. When the nickel content is at least the above lower limit, the connection resistance between the electrodes becomes even lower.

From the viewpoint of further lowering the connection resistance between the electrodes, the nickel layer preferably contains phosphorus. The phosphorus content in 100% by weight of the entire nickel layer preferably exceeds 0% by weight, more preferably 0.1% by weight or more, still more preferably 2% by weight or more, preferably 20% by weight or less, and more preferably. It is 15% by weight or less. When the phosphorus content is at least the above lower limit and at least the above upper limit, the connection resistance becomes even lower.

In order to further reduce the connection resistance between the electrodes and further enhance the connection reliability between the electrodes at high temperature, the phosphorus content in 100% by weight of the entire nickel layer should be less than 5% by weight. Is more preferable. From the viewpoint of effectively exhibiting both low connection resistance between electrodes and high connection reliability between electrodes at high temperature, the phosphorus content is 0% by weight in 100% by weight of the entire nickel layer. It exceeds, more preferably 0.1% by weight or more, still more preferably 2% by weight or more. When the phosphorus content is at least the above lower limit, the connection resistance becomes even lower. From the viewpoint of further lowering the connection resistance, the phosphorus content is preferably 4.9% by weight or less, more preferably 4% by weight or less, still more preferably 3% by weight or less in 100% by weight of the entire nickel layer. is there.

It is preferable that the phosphorus content is different so that the phosphorus content on the gold layer side (outside) is higher than the phosphorus content on the base particle side (inner side) in the thickness direction of the nickel layer. It is preferable that the phosphorus content has a gradient. In the thickness direction of the nickel layer, it is preferable that phosphorus is unevenly distributed so that it is more abundant on the gold layer side than on the base particle side. Due to the presence of such a concentration difference and a concentration gradient, the reliability of the connection resistance is further increased.

In the thickness direction of the nickel layer, phosphorus is unevenly distributed so as to be present in a region having a thickness of 1/2 on the gold layer side rather than a region having a thickness of 1/2 on the substrate particle side. preferable.

The absolute value of the difference between the phosphorus content in the entire region having a thickness of 1/2 on the substrate particle side and the phosphorus content in the entire region having a thickness of 1/2 on the gold layer side is preferably 2% by weight. As mentioned above, it is more preferably 5% by weight or more, further preferably 10% by weight or more, and preferably 19% by weight or less. When the absolute value of the difference in phosphorus content is not less than the above lower limit and not more than the above upper limit, the reliability of the connection resistance is further increased.

In 100% by weight of the entire nickel layer, the content of boron preferably exceeds 0% by weight, more preferably 0.1% by weight or more, further preferably 1% by weight or more, preferably 20% by weight or less, and more preferably. It is 15% by weight or less, more preferably 10% by weight or less, and particularly preferably 5% by weight or less. When the boron content is not more than the above lower limit and the above upper limit, the resistance of the nickel layer becomes even lower, and the nickel layer contributes to the reduction of the connection resistance.

In 100% by weight of the nickel layer, the copper content, the tungsten content and the molybdenum content are preferably 0.1% by weight or more, more preferably 5% by weight or more, preferably 20% by weight or less, more preferably. It is 10% by weight or less. When the copper content, the tungsten content and the molybdenum content are equal to or more than the above lower limit and not more than the above upper limit, the connection resistance between the electrodes is effectively lowered.

The thickness of the first conductive layer (nickel layer or the like) is preferably 30 nm or more, more preferably 60 nm or more, preferably 200 nm or less, and more preferably 100 nm or less. When the thickness of the first conductive layer is not less than the above lower limit and not more than the above upper limit, the oxide film on the surface of the electrode is removed more effectively, and the connection resistance between the electrodes is further lowered. The thickness of the first conductive layer indicates the average thickness of the nickel layer in the conductive particles.

The conductive particles have the gold layer as the conductive layer. The gold layer includes not only the case where only gold is used as the metal but also the case where gold and another metal are used. The gold layer may be a gold alloy layer. In the above conductive particles, it is preferable to provide a gold layer as the outermost layer of the conductive layer. It is preferable that the gold layer is arranged on the outermost surface of the conductive layer.

Examples of metals other than gold in the gold layer include silver, copper, platinum, zinc, iron, tin, lead, aluminum, cobalt, indium, nickel, palladium, chromium, titanium, antimony, bismuth, tarium, germanium, and cadmium. , Silicon, tungsten, molybdenum, tin-doped indium oxide (ITO) and the like. Only one of these metals may be used, or two or more of these metals may be used in combination.

The gold layer preferably contains gold as the main metal. The gold content is preferably 50% by weight or more in 100% by weight of the entire gold layer. The gold content in 100% by weight of the entire gold layer is preferably 90% by weight or more, more preferably 95% by weight or more, and further preferably 99.9% by weight or more. When the gold content is at least the above lower limit, the electrodes and the conductive particles come into contact with each other more appropriately, and the connection resistance between the electrodes becomes even lower.

The thickness of the gold layer is preferably 60 nm or less, more preferably 30 nm or less, even more preferably less than 15 nm, still more preferably 10 nm or less, particularly preferably less than 10 nm, preferably 3 nm or more, and more preferably 5 nm or more. When the thickness of the gold layer is at least the above lower limit and at least the above upper limit, an increase in connection resistance is effectively suppressed. In the conductive particles according to the present invention, even if the thickness of the gold layer is thin, the connection resistance between the electrodes can be lowered because the gold layer is dense, and the variation in the connection resistance between the electrodes can be suppressed. be able to. Further, the thickness of the gold layer does not have to be a continuous film, and when the outer surface of the gold layer is rust-proofed, the thickness of the gold layer is thin and nickel is inside the gold layer. Despite the presence of layers, the increase in connection resistance can be effectively suppressed.

The method for forming the conductive layer is not particularly limited. Examples of the method for forming the conductive layer include a method by electroless plating, a method by electroplating, a method by physical vapor deposition, and a method of coating a metal powder or a paste containing a metal powder and a binder on the surface of particles. Can be mentioned. Among them, the method by electroless plating is preferable because the formation of the conductive layer is easy. Examples of the method by physical vapor deposition include methods such as vacuum vapor deposition, ion plating, and ion sputtering.

Examples of the method for controlling the content of nickel and phosphorus in the conductive layer include a method of controlling the pH of the nickel plating solution when the conductive layer is formed by electroless nickel plating, and a method of controlling the conductive layer by electroless nickel plating. Examples thereof include a method of adjusting the concentration of the phosphorus-containing reducing agent and a method of adjusting the nickel concentration in the nickel plating solution at the time of forming the nickel plating solution.

In the method of forming by electroless plating, a catalysis step and an electroless plating step are generally performed. Hereinafter, an example of a method of forming an alloy plating layer containing nickel and phosphorus on the surface of resin particles by electroless plating will be described.

In the above-mentioned catalystization step, a catalyst serving as a starting point for forming a plating layer by electroless plating is formed on the surface of the resin particles.

As a method of forming the catalyst on the surface of the resin particles, for example, the resin particles are added to a solution containing palladium chloride and tin chloride, and then the surface of the resin particles is activated by an acid solution or an alkaline solution. A method of precipitating palladium on the surface of the resin particles, and after adding the resin particles to a solution containing palladium sulfate and aminopyridine, the surface of the resin particles is activated by a solution containing a reducing agent to obtain the resin particles. Examples thereof include a method of precipitating palladium on the surface. As the reducing agent, a phosphorus-containing reducing agent is preferably used.

In the electroless plating step, a nickel plating bath containing a nickel-containing compound and the phosphorus-containing reducing agent is preferably used. By immersing the resin particles in the nickel plating bath, nickel can be precipitated on the surface of the resin particles on which the catalyst is formed, and a conductive layer containing nickel and phosphorus can be formed.

Examples of the nickel-containing compound include nickel sulfate and nickel chloride. The nickel-containing compound is preferably a nickel salt. Examples of the phosphorus-containing reducing agent include sodium hypophosphite and the like. Moreover, you may use a boron-containing reducing agent. Examples of the boron-containing reducing agent include dimethylamine borane, sodium borohydride, potassium borohydride and the like.

The particle size of the conductive particles is preferably 0.5 μm or more, more preferably 1 μm or more. The particle size of the conductive particles is preferably 100 μm or less, more preferably 20 μm or less, still more preferably 5 μm or less, and particularly preferably 3 μm or less. When the particle diameter of the conductive particles is equal to or greater than the above lower limit and equal to or less than the above upper limit, the contact area between the conductive particles and the electrodes becomes sufficiently large when the electrodes are connected using the conductive particles, and the conductivity is increased. It becomes difficult to form agglomerated conductive particles when forming the layer. In addition, the distance between the electrodes connected via the conductive particles does not become too large, and the conductive layer does not easily peel off from the surface of the base particles.

The particle diameter of the conductive particles indicates the diameter when the conductive particles are spherical, and indicates the maximum diameter when the conductive particles are not spherical.

The conductive particles according to the present invention preferably have protrusions on the conductive surface. The first conductive layer (nickel layer or the like) preferably has protrusions on the outer surface. The gold layer preferably has protrusions on the outer surface. An oxide film is often formed on the surface of the electrode connected by the conductive particles. By using conductive particles having conductive protrusions, the oxide film is effectively removed by the protrusions by arranging the conductive particles between the electrodes and then crimping them. Therefore, the electrodes and the conductive particles can be brought into contact with each other more reliably, and the connection resistance between the electrodes can be further reduced. Further, when the conductive particles have an insulating substance on the surface, or when the conductive particles are dispersed in the resin and used as a conductive material, the protrusions of the conductive particles provide insulation between the conductive particles and the electrode. Substances or resins can be effectively eliminated. Therefore, the conduction reliability between the electrodes can be improved.

It is preferable that the number of the protrusions is plurality. The number of protrusions on the outer surface of the conductive layer per one conductive particle is preferably 3 or more, and more preferably 5 or more. The upper limit of the number of the protrusions is not particularly limited. The number of the protrusions is preferably 1000 or less, more preferably 800 or less. The upper limit of the number of protrusions can be appropriately selected in consideration of the particle size of the conductive particles and the like.

The average height of the plurality of protrusions is preferably 0.001 μm or more, more preferably 0.05 μm or more, preferably 0.9 μm or less, and more preferably 0.2 μm or less. When the average height of the protrusions is at least the above lower limit and at least the above upper limit, the connection resistance between the electrodes is effectively lowered. The average height of the protrusions can be calculated by the following method. The 50 conductive particles of the present invention are observed with an electron microscope or an optical microscope, and the heights of all the protrusions on the peripheral edge of the observed conductive particles are measured. It is obtained by measuring the height of the convex portion with the surface on which the protrusion is not formed as a reference surface and calculating the average value.

From the viewpoint of effectively lowering the connection resistance and effectively increasing the connection reliability between the electrodes under high temperature and high humidity, the surface area of the portion having the protrusions in the total surface area of the outer surface of the gold layer is 100%. Is preferably 10% or more, more preferably 20% or more, still more preferably 30% or more. The upper limit of the ratio of the surface area of the portion having the protrusions to the total surface area of the outer surface of the gold layer is not particularly limited, but is usually 100% or less, preferably 99% or less.

The ratio of the surface area of the portion having the protrusion can be calculated by the following method. It is obtained by observing 50 conductive particles of the present invention with an electron microscope or an optical microscope, measuring the ratio of the area of the portion appearing as a protrusion on the normal projection surface, and calculating the average value.

[Core material]
By embedding the core material in the conductive layer (first conductive layer and gold layer), it is easy to make the first conductive layer and gold layer have a plurality of protrusions on the outer surface. is there. However, in order to form protrusions on the outer surface of the conductive particles and the conductive layer, it is not always necessary to use the core material, and it is preferable not to use the core material. It is preferable that the conductive particles do not have a core substance for raising the outer surface of the conductive portion inside and inside the conductive layer. It is preferable that the conductive layer does not contain a core substance for raising the outer surface of the conductive layer inside and inside the conductive layer.

As a method of forming the above-mentioned protrusions, a method of forming a conductive layer by electroless plating after adhering a core substance to the surface of the base material particles, and a method of forming a conductive layer by electroless plating on the surface of the base material particles. After that, a method of adhering a core substance and further forming a conductive layer by electroless plating can be mentioned. As another method for forming the protrusions, after forming a first conductive layer (nickel layer or the like) on the surface of the base material particles, a core substance is placed on the first conductive layer, and then the core substance is arranged. Examples thereof include a method of forming a second conductive layer (gold layer, etc.) and a method of adding a core substance in the middle of forming a conductive layer (nickel layer, gold layer, etc.) on the surface of the base particle. ..

As a method of arranging the core substance on the surface of the base particle, for example, the core substance is added to the dispersion liquid of the base particle, and the core substance is placed on the surface of the base particle, for example, Van der Waals force. Examples thereof include a method of accumulating and adhering the base material, and a method of adding the core substance to the container containing the base material particles and adhering the core material to the surface of the base material particles by mechanical action such as rotation of the container. .. Among them, since it is easy to control the amount of the core substance to be adhered, a method of accumulating the core substance on the surface of the base material particles in the dispersion liquid and adhering the core substance is preferable.

Examples of the substance constituting the core substance include a conductive substance and a non-conductive substance. Examples of the conductive substance include metals, metal oxides, conductive non-metals such as graphite, and conductive polymers. Examples of the conductive polymer include polyacetylene and the like. Examples of the non-conductive substance include silica, alumina, barium titanate and zirconia. Among them, metal is preferable because the conductivity can be increased and the connection resistance can be effectively lowered. The core material is preferably metal particles.

Examples of the metal include metals such as gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium and cadmium, and tin-lead. Examples thereof include alloys composed of two or more kinds of metals such as alloys, tin-copper alloys, tin-silver alloys, tin-lead-silver alloys and tungsten carbide. Of these, nickel, copper, silver or gold is preferred. The metal for forming the core substance may be the same as or different from the metal for forming the conductive layer. The metal for forming the core substance preferably contains a metal for forming the conductive layer. The metal for forming the core substance preferably contains nickel. The metal for forming the core substance preferably contains nickel.

Specific examples of the material of the core material include barium titanate (Mohs hardness 4.5), nickel (Mohs hardness 5), silica (silicon dioxide, Mohs hardness 6-7), titanium oxide (Mohs hardness 7), and zirconia. (Mohs hardness 8 to 9), alumina (Mohs hardness 9), tungsten carbide (Mohs hardness 9), diamond (Mohs hardness 10) and the like can be mentioned. The inorganic particles are preferably nickel, silica, titanium oxide, zirconia, alumina, tungsten carbide or diamond, more preferably silica, titanium oxide, zirconia, alumina, tungsten carbide or diamond, and titanium oxide or zirconia. , Alumina, Tungsten Carbide or Diamond, and particularly preferably Zirconia, Alumina, Tungsten Carbide or Diamond. The Mohs hardness of the material of the core material is preferably 5 or more, more preferably 6 or more, still more preferably 7 or more, and particularly preferably 7.5 or more.

The shape of the core substance is not particularly limited. The shape of the core material is preferably lumpy. Examples of the core material include particulate lumps, agglomerates in which a plurality of fine particles are aggregated, and amorphous lumps.

The average diameter (average particle size) of the core substance is preferably 0.001 μm or more, more preferably 0.05 μm or more, preferably 0.9 μm or less, and more preferably 0.2 μm or less. When the average diameter of the core material is at least the above lower limit and at least the above upper limit, the connection resistance between the electrodes is effectively lowered.

The "average diameter (average particle diameter)" of the core substance indicates a number average diameter (number average particle diameter). The average diameter of the core material is obtained by observing 50 arbitrary core materials with an electron microscope or an optical microscope and calculating an average value.

[Insulating material]
The conductive particles according to the present invention preferably include an insulating substance arranged on the outer surface of the conductive layer (the gold layer). In this case, if conductive particles are used for the connection between the electrodes, a short circuit between adjacent electrodes can be prevented. Specifically, when a plurality of conductive particles come into contact with each other, an insulating substance exists between the plurality of electrodes, so that it is possible to prevent a short circuit between the electrodes adjacent to each other in the lateral direction rather than between the upper and lower electrodes. By pressurizing the conductive particles with the two electrodes at the time of connection between the electrodes, the insulating substance between the conductive layer of the conductive particles and the electrodes can be easily removed. When the conductive particles have a plurality of protrusions on the outer surface of the conductive layer, the insulating substance between the conductive layer of the conductive particles and the electrodes can be easily removed.

The insulating material is preferably insulating particles because the insulating material can be more easily removed during crimping between the electrodes.

Specific examples of the insulating resin that is the material of the insulating material include polyolefins, (meth) acrylate polymers, (meth) acrylate copolymers, block polymers, thermoplastic resins, crosslinked products of thermoplastic resins, and thermosetting. Examples include sex resins and water-soluble resins.

Examples of the polyolefins include polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer and the like. Examples of the (meth) acrylate polymer include polymethyl (meth) acrylate, polyethyl (meth) acrylate, and polybutyl (meth) acrylate. Examples of the block polymer include polystyrene, styrene-acrylic acid ester copolymer, SB type styrene-butadiene block copolymer, SBS type styrene-butadiene block copolymer, and hydrogenated products thereof. Examples of the thermoplastic resin include vinyl polymers and vinyl copolymers. Examples of the thermosetting resin include epoxy resin, phenol resin, melamine resin and the like. Examples of the water-soluble resin include polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyvinylpyrrolidone, polyethylene oxide, methyl cellulose and the like. Of these, a water-soluble resin is preferable, and polyvinyl alcohol is more preferable.

Examples of the method of arranging the insulating substance on the surface of the conductive layer include a chemical method and a physical or mechanical method. Examples of the chemical method include an interfacial polymerization method, a suspension polymerization method in the presence of particles, and an emulsion polymerization method. Examples of the physical or mechanical method include spray drying, hybridization, electrostatic adhesion method, spraying method, dipping and vacuum deposition methods. Among them, since the insulating substance is difficult to be detached, the method of arranging the insulating substance on the surface of the conductive layer via a chemical bond is preferable.

The outer surface of the conductive layer (the gold layer) and the surface of the insulating particles may each be coated with a compound having a reactive functional group. The outer surface of the conductive layer and the surface of the insulating particles may not be directly chemically bonded, or may be indirectly chemically bonded by a compound having a reactive functional group. After introducing a carboxyl group into the outer surface of the conductive layer, the carboxyl group may be chemically bonded to a functional group on the surface of the insulating particles via a polymer electrolyte such as polyethyleneimine.

The average diameter (average particle diameter) of the insulating substance can be appropriately selected depending on the particle diameter of the conductive particles, the use of the conductive particles, and the like. The average diameter (average particle size) of the insulating substance is preferably 0.005 μm or more, more preferably 0.01 μm or more, preferably 1 μm or less, and more preferably 0.5 μm or less. When the average diameter of the insulating substance is at least the above lower limit, it becomes difficult for the conductive layers of the plurality of conductive particles to come into contact with each other when the conductive particles are dispersed in the binder resin. When the average diameter of the insulating particles is not more than the above upper limit, it is not necessary to make the pressure too high in order to eliminate the insulating substance between the electrodes and the conductive particles when connecting the electrodes, and the temperature becomes high. There is no need to heat it.

The "average diameter (average particle diameter)" of the insulating substance indicates a number average diameter (number average particle diameter). The average diameter of the insulating substance is determined by using a particle size distribution measuring device or the like.

[Rust prevention treatment]
The outer surface of the gold layer is rust-proofed in order to suppress corrosion of conductive particles and reduce connection resistance between electrodes.

From the viewpoint of further enhancing the conduction reliability, the outer surface of the gold layer is preferably rust-proofed with a compound having an alkyl group having 6 to 22 carbon atoms. The surface of the gold layer may be rust-proofed with a phosphorus-free compound, or may be rust-proofed with a phosphorus-free compound having an alkyl group having 6 to 22 carbon atoms. From the viewpoint of further enhancing conduction reliability, it is preferable that the outer surface of the gold layer is rust-proofed with an alkylphosphoric acid compound or an alkylthiol. By the rust preventive treatment, a rust preventive film can be formed on the outer surface of the gold layer.

The rust preventive film is preferably formed of a compound having an alkyl group having 6 to 22 carbon atoms (hereinafter, also referred to as compound A). The outer surface of the gold layer is preferably surface-treated with the compound A. When the number of carbon atoms of the alkyl group is 6 or more, rust is less likely to occur in the entire conductive layer, and in particular, rust is less likely to occur in the nickel layer. When the number of carbon atoms of the alkyl group is 22 or less, the conductivity of the conductive particles becomes high. From the viewpoint of further increasing the conductivity of the conductive particles, the number of carbon atoms of the alkyl group in the compound A is preferably 16 or less. The alkyl group may have a linear structure or a branched structure. The alkyl group preferably has a linear structure.

The compound A is not particularly limited as long as it has an alkyl group having 6 to 22 carbon atoms. The compound A has a phosphoric acid ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof, a subphosphate ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof, and an alkyl group having 6 to 22 carbon atoms. It is preferably at least one selected from the group consisting of an alkoxysilane, an alkylthiol having an alkyl group having 6 to 22 carbon atoms, and a dialkyldisulfide having an alkyl group having 6 to 22 carbon atoms. That is, the compound A having an alkyl group having 6 to 22 carbon atoms is at least one selected from the group consisting of a phosphoric acid ester or a salt thereof, a phosphite ester or a salt thereof, an alkoxysilane, an alkylthiol and a dialkyldisulfide. Is preferable. By using these preferable compounds A, it is possible to make the conductive layer more resistant to rust. From the viewpoint of making rust less likely to occur, the compound A is preferably a phosphoric acid ester or a salt thereof, a phosphite ester or a salt thereof, or an alkylthiol, and the phosphoric acid ester or a salt thereof. Alternatively, it is more preferably a phosphite ester or a salt thereof. As the compound A, only one kind may be used, or two or more kinds may be used in combination.

The compound A preferably has a reactive functional group that can react with the outer surface of the nickel layer, and preferably has a reactive functional group that can react with the outer surface of the gold layer. The compound A preferably has a reactive functional group capable of reacting with the insulating substance. The rust preventive film is preferably chemically bonded to the gold layer. The rust preventive film is preferably chemically bonded to the insulating substance. It is more preferable that the rust preventive film is chemically bonded to both the gold layer and the insulating substance. Due to the presence of the reactive functional groups and the chemical bonds, the rust-preventive film is less likely to peel off, and as a result, rust is less likely to occur on the gold layer, and an insulating substance is released from the surface of the conductive particles. It becomes more difficult to detach unintentionally.

Examples of the phosphoric acid ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof include phosphoric acid hexyl ester, phosphoric acid heptyl ester, phosphoric acid monooctyl ester, phosphoric acid monononyl ester, and phosphoric acid monodecyl ester. Organophosphate monoundecyl ester, phosphate monododecyl ester, phosphate monotridecyl ester, phosphate monotetradecyl ester, phosphate monopentadecyl ester, phosphate monohexyl ester monosodium salt, phosphate monoheptyl ester monosodium Salt, monooctyl phosphate monosodium salt, mononoyl phosphate monosodium salt, monodecyl phosphate monosodium salt, monoundecyl phosphate monosodium salt, monododecyl phosphate monosodium salt, phosphate Examples thereof include a monotridecyl ester monosodium salt, a monotetradecyl phosphate monosodium salt, and a monopentadecyl phosphate monosodium salt. The potassium salt of the above-mentioned phosphoric acid ester may be used.

Examples of the phosphite ester having an alkyl group having 6 to 22 carbon atoms or a salt thereof include hexyl phosphite ester, heptyl phosphite ester, monooctyl phosphite ester, monononyl phosphite ester, and sub-phosphate. Monodecyl phosphate, monoundecyl phosphite, monododecyl phosphite, monotridecyl phosphite, monotetradecyl phosphite, monopentadecyl phosphite, monohexyl phosphite Ester monosodium salt, phosphite monoheptyl ester monosodium salt, phosphite monooctyl ester monosodium salt, phosphite monononyl ester monosodium salt, phosphite monodecyl ester monosodium salt, phosphite monoun Decyl ester monosodium salt, phosphite monododecyl ester monosodium salt, phosphite monotridecyl ester monosodium salt, phosphite monotetradecyl ester monosodium salt, phosphite monopentadecyl ester monosodium salt, etc. Can be mentioned. The potassium salt of the above phosphite ester may be used.

Examples of the alkoxysilane having an alkyl group having 6 to 22 carbon atoms include hexyltrimethoxysilane, hexyltriethoxysilane, heptyltrimethoxysilane, heptyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, and nonyltri. Methoxysilane, nonyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, undecyltrimethoxysilane, undecyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, tridecyltrimethoxysilane, tridecyltriethoxysilane Examples thereof include silane, tetradecyltrimethoxysilane, tetradecyltriethoxysilane, pentadecyltrimethoxysilane, and pentadecyltriethoxysilane.

Examples of the alkyl thiol having an alkyl group having 6 to 22 carbon atoms include hexyl thiol, heptyl thiol, octyl thiol, nonyl thiol, decyl thiol, undecyl thiol, dodecyl thiol, tridecyl thiol, tetradecyl thiol and pentadecyl. Examples thereof include thiols and hexadecylthiols. The alkyl thiol preferably has a thiol group at the end of the alkyl chain.

Examples of the dialkyl disulfide having an alkyl group having 6 to 22 carbon atoms include dihexyl disulfide, diheptyl disulfide, dioctyl disulfide, dinonyl disulfide, didecyl disulfide, diundecyl disulfide, didodecyl disulfide, ditridecyl disulfide, and ditetra. Examples thereof include decyl disulfide, dipenta decyl disulfide and dihexadecyl disulfide.

(Conductive material)
The conductive material according to the present invention includes the above-mentioned conductive particles and a binder resin. The conductive particles are preferably dispersed in the binder resin and used, and are preferably dispersed in the binder resin and used as the conductive material. The conductive material is preferably an anisotropic conductive material. The conductive material is preferably used for electrical connection between electrodes. The conductive material is preferably a circuit connection material.

The binder resin is not particularly limited. As the binder resin, a known insulating resin is used.

Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, and elastomers. Only one kind of the binder resin may be used, or two or more kinds may be used in combination.

Examples of the vinyl resin include vinyl acetate resin, acrylic resin, styrene resin and the like. Examples of the thermoplastic resin include polyolefin resins, ethylene-vinyl acetate copolymers, and polyamide resins. Examples of the curable resin include epoxy resin, urethane resin, polyimide resin, unsaturated polyester resin and the like. The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin, or a moisture curable resin. The curable resin may be used in combination with a curing agent. Examples of the thermoplastic block copolymer include a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a hydrogenated additive of a styrene-butadiene-styrene block copolymer, and a styrene-isoprene. -Hydrogen additives for styrene block copolymers and the like can be mentioned. Examples of the elastomer include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.

In addition to the conductive particles and the binder resin, the conductive material includes, for example, a filler, a bulking agent, a softening agent, a plasticizer, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, a heat stabilizer, and a photostabilizer. It may contain various additives such as an agent, an ultraviolet absorber, a lubricant, an antistatic agent and a flame retardant.

The conductive material according to the present invention can be used as a conductive paste, a conductive film, or the like. When the conductive material according to the present invention is a conductive film, a film containing no conductive particles may be laminated on the conductive film containing the conductive particles. The conductive paste is preferably an anisotropic conductive paste. The conductive film is preferably an anisotropic conductive film.

The content of the binder resin in 100% by weight of the conductive material is preferably 10% by weight or more, more preferably 30% by weight or more, still more preferably 50% by weight or more, particularly preferably 70% by weight or more, preferably 99% by weight. It is 99% by weight or less, more preferably 99.9% by weight or less. When the content of the binder resin is not less than the above lower limit and not more than the above upper limit, the conductive particles are efficiently arranged between the electrodes, and the connection reliability of the connection target member connected by the conductive material is further improved.

The content of the conductive particles in 100% by weight of the conductive material is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, preferably 40% by weight or less, more preferably 20% by weight or less. More preferably, it is 10% by weight or less. When the content of the conductive particles is not less than the above lower limit and not more than the above upper limit, the conduction reliability between the electrodes is further increased.

(Connection structure)
A connection structure can be obtained by connecting the members to be connected using the conductive particles or a conductive material containing the conductive particles and a binder resin.

The connection structure includes a first connection target member, a second connection target member, and a connection portion connecting the first and second connection target members, and the connection portion has the above-mentioned conductivity. It is preferably a connection structure formed of particles or a conductive material containing the above-mentioned conductive particles and a binder resin. When conductive particles are used, the connecting portion itself is the conductive particles. That is, the first and second connection target members are connected by the conductive particles.

FIG. 3 schematically shows a connection structure using conductive particles according to the first embodiment of the present invention in a cross-sectional view.

The connection structure 51 shown in FIG. 3 connects a first connection target member 52, a second connection target member 53, and a connection portion 54 connecting the first and second connection target members 52 and 53. Be prepared. The connecting portion 54 is formed by curing a conductive material containing the conductive particles 1. In FIG. 3, the conductive particles 1 are shown schematically for convenience of illustration. Conductive particles 21 and the like may be used instead of the conductive particles 1.

The first connection target member 52 has a plurality of first electrodes 52a on the surface (upper surface). The second connection target member 53 has a plurality of second electrodes 53a on the surface (lower surface). The first electrode 52a and the second electrode 53a are electrically connected by one or more conductive particles 1. Therefore, the first and second connection target members 52 and 53 are electrically connected by the conductive particles 1.

The method for manufacturing the connection structure is not particularly limited. As an example of a method for manufacturing a connection structure, the conductive material is arranged between a first connection target member and a second connection target member, and after obtaining a laminate, the laminate is heated and pressurized. The method and the like can be mentioned. The pressurizing pressure is about 9.8 × 10 ^{4 to} 4.9 × 10 ⁶ Pa. The heating temperature is about 120 to 220 ° C.

Specific examples of the connection target member include electronic components such as semiconductor chips, capacitors and diodes, and electronic components such as printed circuit boards, flexible printed circuit boards, glass epoxy boards and circuit boards such as glass substrates. The connection target member is preferably an electronic component. The conductive particles are preferably used for electrical connection of electrodes in electronic components.

Examples of the electrodes provided on the connection target member include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, silver electrodes, molybdenum electrodes and tungsten electrodes. When the connection target member is a flexible printed substrate, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, or a copper electrode. When the member to be connected is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, or a tungsten electrode. When the electrode is an aluminum electrode, it may be an electrode formed only of aluminum, or an electrode in which an aluminum layer is laminated on the surface of a metal oxide layer. Examples of the material of the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal element include Sn, Al and Ga.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

In order to obtain conductive particles, the following base particles were prepared.

Base particle A: Resin particles; Divinylbenzene copolymer resin particles having a particle diameter of 3.0 μm (“Micropearl SP-203” manufactured by Sekisui Chemical Co., Ltd.)

Base particle B: Resin particles; Resin particles having a particle size of 3.0 μm, made by polymerizing divinylbenzene and PTMGA (manufactured by Kyoeisha Chemical Co., Ltd.) at a weight ratio of 3: 7.

Base particle C:
The surface of divinylbenzene copolymer resin particles (“Micropearl SP-2025” manufactured by Sekisui Chemical Co., Ltd.) having a particle size of 2.5 μm was coated with a silica shell (thickness 250 nm) using a condensation reaction by a sol-gel reaction. A core-shell type organic-inorganic hybrid particle (base particle C) having a particle diameter of 3.0 μm was obtained.

Base particle D:
300 g of a 0.13 wt% ammonia aqueous solution was placed in a 500 mL reaction vessel equipped with a stirrer and a thermometer. Next, in an aqueous ammonia solution in the reaction vessel, 4.1 g of methyltrimethoxysilane, 19.2 g of vinyltrimethoxysilane, and 0.7 g of silicone alkoxy oligomer (“X-41-1053” manufactured by Shin-Etsu Chemical Co., Ltd.) The mixture with was added slowly. After advancing the hydrolysis and condensation reaction with stirring, 2.4 mL of a 25 wt% aqueous ammonia solution was added, and then the particles were isolated from the aqueous ammonia solution, and the obtained particles were subjected to an oxygen partial pressure of ^10-17 atm. , 350 ° C. for 2 hours to obtain organic-inorganic hybrid particles (base particle D) having a particle size of 3.0 μm.

Base particle E: Base particle E having a particle diameter of 2.5 μm, which differs from the base particle A only in particle size.

Base particle F: Base particle F having a particle diameter of 10.0 μm, which differs only from the base particle A in particle size.

The following rust preventives (compounds) were used for rust preventive treatment.

Rust inhibitor A: 2-ethylhexyl azid phosphate

Rust inhibitor B: Lauryl azid phosphate

Rust inhibitor C: Steariazid phosphate

(Example 1)
(1) Preparation of Nickel Layer 10 parts by weight of the base particle A is dispersed in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution using an ultrasonic disperser, and then the solution is filtered. The base particle A was taken out. Next, the base particle A was added to 100 parts by weight of a 1 wt% dimethylamine borane solution to activate the surface of the substrate particle A. The surface-activated substrate particles A were thoroughly washed with water, and then added to 500 parts by weight of distilled water and dispersed to obtain a suspension.

Further, a nickel plating solution (pH 9.0) containing nickel sulfate 0.25 mol / L, sodium hypophosphite 0.25 mol / L, and sodium citrate 0.15 mol / L was prepared.

While stirring the obtained suspension at 70 ° C., the nickel plating solution was gradually added dropwise to the suspension to perform electroless nickel plating. Then, the suspension was filtered to take out the particles, washed with water, and dried to obtain particles in which the nickel-phosphorus alloy conductive layer (thickness 102 nm) was arranged on the surface of the base particle A.

(2) Formation of Gold Layer Particles in which a nickel-phosphorus alloy conductive layer (thickness 102 nm) is arranged on the surface of the base particle A are thoroughly washed with water, and then added to 500 parts by weight of distilled water and dispersed to suspend the particles. A turbid liquid (1) was obtained.

2 L of gold plating solution (pH 9.0) containing 0.01 mol / L of potassium gold cyanide, 0.20 mol / L of sodium citrate, 0.08 mol / L of ethylenediaminetetraacetic acid, and 0.5 mol / L of sodium hydroxide. I prepared.

Further, 1.5 L of a reducing agent solution (pH 9.0) containing 0.08 mol / L of dimethylamine borane and 0.1 mol / L of sodium hydroxide was prepared.

While stirring the obtained suspension (1) at 55 ° C., 0.5 L of the above gold plating solution was gradually added dropwise to the suspension to perform replacement gold plating.

Next, 1.5 L of the gold plating solution and 1.5 L of the reducing agent solution were gradually added dropwise to the suspension at the same time to perform reduction gold plating.

Then, the suspension was filtered to take out the particles, washed with water, and dried to obtain particles in which a gold layer (thickness 14 nm) was arranged on the outer surface of the nickel-phosphorus alloy conductive layer.

(3) Rust Prevention Treatment By dispersing the particles using the rust preventive agent A, conductive particles having the outer surface of the gold layer treated with rust prevention were obtained.

(Example 2)
Prepare 2 L of gold plating solution (pH 9.0) containing 0.01 mol / L of potassium gold cyanide, 0.20 mol / L of sodium citrate, 0.08 mol / L of ethylenediaminetetraacetic acid, and 0.5 mol / L of sodium hydroxide. did.

Further, 0.5 L of a reducing agent solution (pH 9.0) containing 0.08 mol / L of dimethylamine borane and 0.1 mol / L of sodium hydroxide was prepared.

While stirring the suspension (1) obtained in Example 1 at 45 ° C., 1.5 L of the above gold plating solution was gradually added dropwise to the suspension to perform replacement gold plating.

Next, 0.5 L of the gold plating solution and 0.5 L of the reducing agent solution were gradually added dropwise to the suspension at the same time to perform reduction gold plating.

Then, the suspension was filtered to take out the particles, washed with water, and dried to obtain particles in which a gold layer (thickness 14 nm) was arranged on the outer surface of the nickel-phosphorus alloy conductive layer.

Conductive particles were obtained in the same manner as in Example 1 except that the above changes were made.

(Example 3)
Conductive particles were obtained in the same manner as in Example 1 except that the rust preventive treatment was not performed.

(Example 4)
Prepare 2 L of gold plating solution (pH 9.0) containing 0.013 mol / L of potassium gold cyanide, 0.20 mol / L of sodium citrate, 0.08 mol / L of ethylenediaminetetraacetic acid, and 0.5 mol / L of sodium hydroxide. did.

Further, 1.5 L of a reducing agent solution (pH 9.0) containing 0.08 mol / L of dimethylamine borane and 0.1 mol / L of sodium hydroxide was prepared.

While stirring the suspension (1) obtained in Example 1 at 55 ° C., 0.5 L of the above gold plating solution was gradually added dropwise to the suspension to perform replacement gold plating.

Next, 1.5 L of the gold plating solution and 1.5 L of the reducing agent solution were gradually added dropwise to the suspension at the same time to perform reduction gold plating.

Then, the suspension was filtered to take out the particles, washed with water, and dried to obtain particles in which a gold layer (thickness 22 nm) was arranged on the outer surface of the nickel-phosphorus alloy conductive layer.

Conductive particles were obtained in the same manner as in Example 1 except that the gold plating conditions were changed to the above.

(Example 5)
Prepare 2 L of gold plating solution (pH 9.0) containing 0.02 mol / L of potassium gold cyanide, 0.20 mol / L of sodium citrate, 0.10 mol / L of ethylenediaminetetraacetic acid, and 0.5 mol / L of sodium hydroxide. did.

Further, 1.5 L of a reducing agent solution (pH 9.0) containing 0.08 mol / L of dimethylamine borane and 0.1 mol / L of sodium hydroxide was prepared.

While stirring the suspension (1) obtained in Example 1 at 55 ° C., 0.5 L of the above gold plating solution was gradually added dropwise to the suspension to perform replacement gold plating.

Next, 1.5 L of the gold plating solution and 1.5 L of the reducing agent solution were gradually added dropwise to the suspension at the same time to perform reduction gold plating.

Then, the suspension was filtered to take out the particles, washed with water, and dried to obtain particles in which a gold layer (thickness 29 nm) was arranged on the outer surface of the nickel-phosphorus alloy conductive layer.

Conductive particles were obtained in the same manner as in Example 1 except that the gold plating conditions were changed to the above.

(Example 6)
By dispersing the particles using the rust preventive agent B, conductive particles were obtained in the same manner as in Example 1 except that the outer surface of the gold layer was rust-proofed.

(Example 7)
By dispersing the particles with the rust preventive agent C, conductive particles were obtained in the same manner as in Example 1 except that the outer surface of the gold layer was rust-proofed.

(Example 8)
The base particle A was etched and washed with water. Next, the base particle A was added to 100 mL of a palladium-catalyzed solution containing 8% by weight of a palladium catalyst, and the mixture was stirred. Then it was filtered and washed. The base particle A was added to a 0.5 wt% dimethylamine borane solution having a pH of 6 to obtain a base particle A to which palladium was attached.

The base particle A to which palladium was attached was stirred in 300 mL of ion-exchanged water for 3 minutes and dispersed to obtain a dispersion liquid. Next, 1 g of a metallic nickel particle slurry (average particle diameter 100 nm) was added to the dispersion over 3 minutes to obtain base particle A to which the core substance was attached.

A nickel layer and a gold layer were formed in the same manner as in Example 1 except that the base particle A to which the core substance was attached was used to obtain conductive particles.

(Example 9)
An electroless nickel plating solution containing sodium hypophosphite was prepared. Further, a late electroless nickel plating solution containing sodium hypophosphite was prepared.

Further, a plating solution for forming protrusions containing 2.18 mol / L of sodium hypophosphite and 0.05 mol / L of sodium hydroxide was prepared.

The electroless plating treatment was performed using the base particle A and the electroless nickel plating solution of the previous term. Next, in order to form protrusions on the conductive layer, a plating solution for forming protrusions was gradually dropped to form protrusions. Nickel plating was performed while dispersing the Ni protrusion nuclei generated in the plating solution by ultrasonic stirring. By electroless plating using the above-mentioned late electroless nickel plating solution, particles in which a nickel layer (nickel-phosphorus alloy conductive layer, thickness 102 nm) and precipitation protrusions were formed on the surface of the resin particles were obtained. .. Then, a gold layer was formed in the same manner as in Example 1 to obtain conductive particles.

(Example 10)
100 mmol of methyl methacrylate and N, N, N-trimethyl-N-2-methacryloyloxyethyl in a 1000 mL separable flask equipped with a four-neck separable cover, stirring blade, three-way cock, cooling tube and temperature probe. A monomer composition containing 1 mmol of ammonium chloride and 1 mmol of 2,2'-azobis (2-amidinopropane) dihydrochloride was weighed in ion-exchanged water so as to have a solid content of 5% by weight, and then at 200 rpm. The mixture was stirred and polymerized at 70 ° C. for 24 hours under a nitrogen atmosphere. After completion of the reaction, the reaction was freeze-dried to obtain insulating particles having an ammonium group on the surface, having an average particle diameter of 220 nm and a CV value of 10%.

The insulating particles were dispersed in ion-exchanged water under ultrasonic irradiation to obtain a 10 wt% aqueous dispersion of the insulating particles.

10 g of the conductive particles obtained in Example 8 was dispersed in 500 mL of ion-exchanged water, 4 g of an aqueous dispersion of insulating particles was added, and the mixture was stirred at room temperature for 6 hours. After filtering with a 3 μm mesh filter, the mixture was further washed with methanol and dried to obtain conductive particles to which insulating particles were attached.

When observed with a scanning electron microscope (SEM), only one coating layer of insulating particles was formed on the surface of the conductive particles. When the covering area of the insulating particles (that is, the projected area of the particle diameter of the insulating particles) was calculated for an area of 2.5 μm from the center of the conductive particles by image analysis, the covering ratio was 30%.

(Example 11)
An electroless nickel plating solution containing dimethylamine borane was prepared. Further, a late electroless nickel plating solution containing dimethylamine borane was prepared.

Further, a plating solution for forming protrusions containing 2.0 mol / L of dimethylamine borane and 0.05 mol / L of sodium hydroxide was prepared.

The electroless plating treatment was performed using the base particle A and the electroless nickel plating solution of the previous term. Next, in order to form protrusions on the conductive layer, a plating solution for forming protrusions was gradually dropped to form protrusions. Nickel plating was performed while dispersing the Ni protrusion nuclei generated in the plating solution by ultrasonic stirring. By electroless plating using the above-mentioned late electroless nickel plating solution, particles in which a nickel layer (nickel-boron alloy conductive layer, thickness 102 nm) and precipitation protrusions were formed on the surface of the resin particles were obtained. .. Then, a gold layer was formed in the same manner as in Example 1 to obtain conductive particles.

(Example 12)
An electroless nickel plating solution containing sodium hypophosphite and sodium tungstate was prepared. Further, a late electroless nickel plating solution containing sodium hypophosphite and sodium tungstate was prepared.

Further, a plating solution for forming protrusions containing 2.18 mol / L of sodium hypophosphite and 0.05 mol / L of sodium hydroxide was prepared.

The electroless plating treatment was performed using the base particle A and the electroless nickel plating solution of the previous term. Next, in order to form protrusions on the conductive layer, a plating solution for forming protrusions was gradually dropped to form protrusions. Nickel plating was performed while dispersing the Ni protrusion nuclei generated in the plating solution by ultrasonic stirring. By performing electroless plating with the above late electroless nickel plating solution, particles in which a nickel layer (nickel-tungsten-phosphorus alloy conductive layer, thickness 102 nm) and precipitation protrusions are formed on the surface of the resin particles are formed. Obtained. Then, a gold layer was formed in the same manner as in Example 1 to obtain conductive particles.

(Example 13)
An electroless nickel plating solution containing dimethylamine borane and sodium tungstate was prepared. Further, a late electroless nickel plating solution containing dimethylamine borane and sodium tungstate was prepared.

Further, a plating solution for forming protrusions containing 2.0 mol / L of dimethylamine borane and 0.05 mol / L of sodium hydroxide was prepared.

The electroless plating treatment was performed using the base particle A and the electroless nickel plating solution of the previous term. Next, in order to form protrusions on the conductive layer, a plating solution for forming protrusions was gradually dropped to form protrusions. Nickel plating was performed while dispersing the Ni protrusion nuclei generated in the plating solution by ultrasonic stirring. By performing electroless plating with the above late electroless nickel plating solution, particles in which a nickel layer (nickel-tungsten-boron alloy conductive layer, thickness 102 nm) and precipitation protrusions are formed on the surface of the resin particles are formed. Obtained. Then, a gold layer was formed in the same manner as in Example 1 to obtain conductive particles.

(Example 14)
Conductive particles were obtained in the same manner as in Example 1 except that the base particle A was changed to the base particle B.

(Example 15)
A nickel layer (nickel-phosphorus alloy conductive layer) and a gold layer were formed in the same manner as in Example 1 except that the base particle A was changed to the base particle C to obtain conductive particles.

(Example 16)
A nickel layer (nickel-phosphorus alloy conductive layer) and a gold layer were formed in the same manner as in Example 1 except that the base particle A was changed to the base particle D to obtain conductive particles.

(Example 17)
A nickel layer (nickel-phosphorus alloy conductive layer) and a gold layer were formed in the same manner as in Example 1 except that the base particle A was changed to the base particle E to obtain conductive particles.

(Example 18)
A nickel layer (nickel-phosphorus alloy conductive layer) and a gold layer were formed in the same manner as in Example 1 except that the base particle A was changed to the base particle F to obtain conductive particles.

(Example 19)
(1) Formation of Nickel Layer 10 parts by weight of the base particle A is dispersed in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution using an ultrasonic disperser, and then the solution is filtered. The base particle A was taken out. Next, the base particle A was added to 100 parts by weight of a 1 wt% dimethylamine borane solution to activate the surface of the substrate particle A. The surface-activated substrate particles A were thoroughly washed with water, and then added to 500 parts by weight of distilled water and dispersed to obtain a suspension.

Further, a nickel plating solution (pH 7.0) containing nickel sulfate 0.25 mol / L, sodium hypophosphite 0.25 mol / L, sodium citrate 0.15 mol / L and sodium tungstate 0.12 mol / L was prepared. did.

While stirring the obtained suspension at 60 ° C., the nickel plating solution was gradually added dropwise to the suspension to perform electroless nickel plating. Subsequently, a nickel plating solution (pH 10.0) containing nickel sulfate 0.25 mol / L, sodium hypophosphite 0.25 mol / L, sodium citrate 0.15 mol / L and sodium tungstate 0.12 mol / L was applied. It was gradually added dropwise to the suspension for electroless nickel plating. Then, the suspension was filtered to take out the particles, washed with water, and dried to obtain particles in which a nickel-tungsten-phosphorus alloy conductive layer (thickness 102 nm) was arranged on the surface of the base particle A. ..

A gold layer was formed in the same manner as in Example 1 except that the obtained particles were used to obtain conductive particles.

(Comparative Example 1)
Prepare 2 L of gold plating solution (pH 9.0) containing 0.01 mol / L of potassium gold cyanide, 0.20 mol / L of sodium citrate, 0.08 mol / L of ethylenediaminetetraacetic acid, and 0.5 mol / L of sodium hydroxide. did.

While stirring the obtained suspension at 45 ° C., 2.0 L of the above gold plating solution was gradually added dropwise to the suspension to perform replacement gold plating.

Then, the suspension was filtered to take out the particles, washed with water, and dried to obtain particles in which a gold layer (thickness 14 nm) was arranged on the outer surface of the nickel-phosphorus alloy conductive layer.

Conductive particles were obtained in the same manner as in Example 1 except that a gold layer was formed under the above gold plating conditions.

(Comparative Example 2)
Prepare 2 L of gold plating solution (pH 9.0) containing 0.01 mol / L of potassium gold cyanide, 0.20 mol / L of sodium citrate, 0.08 mol / L of ethylenediaminetetraacetic acid, and 0.5 mol / L of sodium hydroxide. did.

Further, 1.9 L of a reducing agent solution (pH 9.0) containing 0.08 mol / L of dimethylamine borane and 0.1 mol / L of sodium hydroxide was prepared.

While stirring the suspension (1) obtained in Example 1 at 60 ° C., 0.1 L of the above gold plating solution was gradually added dropwise to the suspension to perform replacement gold plating.

Next, 1.9 L of the gold plating solution and 1.9 L of the reducing agent solution were gradually added dropwise to the suspension at the same time to perform reduction gold plating.

Then, the suspension was filtered to take out the particles, washed with water, and dried to obtain particles in which a gold layer (thickness 14 nm) was arranged on the outer surface of the nickel-phosphorus alloy conductive layer.

Conductive particles were obtained in the same manner as in Example 1 except that the above changes were made.

(Evaluation)
(1) Crystallite size (crystal size)
Using an X-ray diffractometer (“RINT2500VHF” manufactured by Rigaku Denki Co., Ltd.), the natural width of the diffraction line peculiar to the device depending on the diffraction angle was calculated by function approximation, and the spread of the obtained diffraction line was “no lattice distortion at all”. When it can be assumed that there is no such thing, the half-value width or the integral width representing the spread is substituted into Scherrer's equation to calculate the crystallite size.

Crystallite size (nm) = K · λ / (β · cosθ)
K: Scherrer constant λ: Wavelength of X-ray tube used β: Diffraction line spread due to crystallite size θ: Diffraction angle 2θ / θ

The crystallite size (crystal size) was determined according to the following criteria.

[Criteria for determining crystallite size (crystal size)]
A: Crystal size exceeds 100 nm and 300 nm or less B: Crystal size exceeds 15 nm and 100 nm or less C: Crystal size exceeds 15 nm

(2) Content of Nickel, Phosphorus and Boron in 100% by Weight of Nickel Layer (Conductive Layer) A thin film section of the obtained conductive particles was prepared using a focused ion beam. The contents of nickel, phosphorus, and boron in the conductive layer were measured by an energy dispersive X-ray analyzer (EDS) using a transmission electron microscope FE-TEM (“JEM-2010FEF” manufactured by JEOL Ltd.). The content in the entire nickel layer was determined.

(3) Initial connection resistance The obtained conductive particles are added to "Struct Bond XN-5A" manufactured by Mitsui Chemicals, Inc. so that the content is 10% by weight, and dispersed to obtain an anisotropic conductive paste. Made.

A transparent glass substrate having an ITO electrode pattern having an L / S of 20 μm / 20 μm on the upper surface was prepared. Further, a semiconductor chip having a gold electrode pattern having an L / S of 20 μm / 20 μm on the lower surface was prepared.

An anisotropic conductive paste immediately after production was applied onto the transparent glass substrate so as to have a thickness of 30 μm to form an anisotropic conductive paste layer. Next, the semiconductor chips were laminated on the anisotropic conductive paste layer so that the electrodes face each other. After that, while adjusting the temperature of the head so that the temperature of the anisotropic conductive paste layer becomes 185 ° C., the pressure heating head is placed on the upper surface of the semiconductor chip, and a pressure of 1 MPa is applied to form the anisotropic conductive paste layer. Curing at 185 ° C. gave a connection structure.

The connection resistance between the upper and lower electrodes of the obtained connection structure was measured by the 4-terminal method. The average value of the two connection resistors was calculated. From the relationship of voltage = current x resistance, the connection resistance can be obtained by measuring the voltage when a constant current is passed. The initial connection resistance was judged according to the following criteria.

[Criteria for initial connection resistance]
○ ○: Connection resistance is 2.0Ω or less ○: Connection resistance is more than 2.0Ω, 3.0Ω or less △: Connection resistance is more than 3.0Ω, 5.0Ω or less ×: Connection resistance is more than 5.0Ω

(4) Connection resistance after reliability test (conduction reliability)
The connection structure obtained in the above (3) initial evaluation of connection resistance was left under the condition of 95 ° C. 150 hours after the start of leaving, the connection resistance between the electrodes was measured by the 4-terminal method in the same manner as in the evaluation of the initial connection resistance in (3) above. The connection resistance after the reliability test was judged according to the following criteria.

[Criteria for connecting resistance after reliability test]
○ ○: The average value of the connection resistance (after leaving) is less than 125% compared to the average value of the connection resistance (before leaving) ○: The average value of the connection resistance (after leaving) compared to the average value of the connection resistance (before leaving) Values are 125% or more and less than 150% Δ: Mean value of connection resistance (after leaving) is 150% or more and less than 200% compared to the average value of connection resistance (before leaving) ×: Mean of connection resistance (before leaving) Compared to the value, the average value of connection resistance (after leaving) is 200% or more.

The results are shown in Table 1 below.

In the evaluation of the connection resistance after the above (4) reliability test, the obtained connection structure was left to stand under the condition of 95 ° C. Evaluation of the connection resistance after the above (4) reliability test regarding the tendency of the connection resistance to increase even when the connection structure is obtained after the conductive particles are left at 95 ° C. before obtaining the connection structure. A tendency similar to the result was seen.

1 ... Conductive particles 2 ... Base particles 3 ... Nickel layer (first conductive layer)
4 ... Gold layer 21 ... Conductive particles 21a ... Protrusions 22 ... Nickel layer (first conductive layer)
22a ... Protrusion 23 ... Gold layer 23a ... Protrusion 24 ... Core material 25 ... Insulating material 51 ... Connection structure 52 ... First connection target member 52a ... First electrode 53 ... Second connection target member 53a ... Second Electrode 54 ... Connection

Claims (15)

It comprises base particles, a first conductive layer, and a gold layer containing gold.
The first conductive layer is arranged on the surface of the base particles, and the first conductive layer is arranged on the surface of the base particles.
The gold layer is arranged on the outer surface of the first conductive layer.
Conductive particles having a crystallite size of more than 15 nm and not more than 300 nm in the gold layer. The conductive particles according to claim 1, wherein the first conductive layer contains nickel, copper, tungsten or molybdenum. The conductive particles according to claim 1 or 2, wherein the first conductive layer is a nickel layer containing nickel. The conductive particles according to claim 3, wherein the first conductive layer is a nickel layer containing nickel and phosphorus. The conductive particle according to any one of claims 1 to 4, wherein the outer surface of the gold layer is rust-proofed. The conductive particles according to claim 5, wherein the outer surface of the gold layer is rust-proofed with a compound having an alkyl group having 6 to 22 carbon atoms. The conductive particles according to claim 5 or 6, wherein the outer surface of the gold layer is rust-proofed with a phosphorus-free compound. The nickel layer contains nickel and phosphorus and contains
The conductivity according to any one of claims 1 to 7, wherein phosphorus is unevenly distributed on the gold layer side rather than on the base particle side in the thickness direction of the nickel layer. particle. The conductive particle according to any one of claims 1 to 8, which has a plurality of protrusions on the outer surface of the gold layer. The conductive particle according to claim 9, further comprising a plurality of core substances that raise the outer surface of the gold layer so as to form the plurality of protrusions inside or inside the gold layer. The conductive particle according to claim 10, wherein the material of the core substance has a Mohs hardness of 5 or more. The conductive particle according to any one of claims 9 to 11, wherein the surface area of the portion having the protrusion is 30% or more in the total surface area of the outer surface of the gold layer of 100%. The conductive particle according to any one of claims 1 to 12, comprising an insulating material arranged on the outer surface of the gold layer. A conductive material containing the conductive particles according to any one of claims 1 to 13 and a binder resin. A first connection target member having a first electrode on its surface,
A second connection target member having a second electrode on the surface,
A connecting portion that connects the first connecting target member and the second connecting target member is provided, and the connecting portion is formed of the conductive particles according to any one of claims 1 to 13. Or is formed of a conductive material containing the conductive particles and a binder resin.
A connecting structure in which the first electrode and the second electrode are electrically connected by the conductive particles.

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