conductive particles

Abstract

To provide a conductive particle that can effectively suppress the occurrence of connection failure.SOLUTION: The conductive particle comprises a base particle and a conductive portion disposed on the surface of the base particle. The conductive particle has a particle diameter of 30 μm or greater. A ratio of a resistance value of the conductive particle after 20 cycles of loading and unloading until 20% compressive deformation to a resistance value of the conductive particle after 1 cycle of loading and unloading until 20% compressive deformation is 1.5 or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to conductive particles in which a conductive portion is disposed on the surface of base material particles. The present invention also relates to a connection structure using the above conductive particles.

Background Art

[0002] In recent years, with the increase in the amount of information and the acceleration of communication speed accompanying the market expansion of IOT, 5G communication, VR, AR, artificial intelligence, and autonomous driving systems, etc., processors such as data servers, PCs, and mobile terminals are required to have a higher information processing speed.

[0003] As a method for processing a large amount of information at high speed, for example, improving the processing ability of a CPU (Central Processing Unit) can be mentioned. In order to improve the processing ability of the CPU, the multi-pinning and narrow pitch of the metal terminals (metal pins) of the socket (CPU socket) connecting the CPU and the motherboard are progressing.

[0004] An example of a socket using metal terminals (metal pins) is disclosed in Patent Document 1 below. Patent Document 1 below discloses an electronic component socket that is interposed between an electronic component such as a semiconductor element or a semiconductor device and a mounting substrate, detachably mounts the electronic component, and electrically connects the electronic component and the mounting substrate. In the above electronic component socket, connection terminals are provided on the mounting surface side of a socket body made of resin. This connection terminal is formed by adhering a conductor film to the outer surface of a resin bump provided integrally with the socket body and protruding from the socket body. In the above electronic component socket, the base end is joined to the inner surface of the conductor film, and the base end side is buried and sealed in the resin bump and the socket body to provide a connection terminal. This connection terminal is formed such that the tip side extends in a bent shape from the side opposite to the mounting surface of the socket body.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2003-297507 [Overview of the project] [Problems that the invention aims to solve]

[0006] Figure 5 is a schematic front cross-sectional view showing a connection structure using metal terminals. The connection structure 101 comprises a first connection target member 52, a second connection target member 53, and a connection portion 104. The first connection target member 52 has a plurality of first electrodes 52a on its surface (top surface). The second connection target member 53 has a plurality of second electrodes 53a on its surface (bottom surface). The connection portion 54 comprises an insulating member 31, a metal terminal (metal pin) 35, and a solder ball 34. The connection portion 104 is a socket portion formed by a socket. The first connection target member 52 is, for example, a motherboard, and the second connection target member 53 is, for example, a CPU.

[0007] Conventional sockets and the like make it extremely difficult to process the fine metal terminals (metal pins) needed to accommodate further increases in the number of pins and narrower pitches. Furthermore, miniaturizing the metal terminals (metal pins) reduces their strength, which can cause them to break or bend during CPU connection, resulting in connection failures.

[0008] Conventional sockets using metal terminals (metal pins) have difficulty accommodating further increases in the number of pins and narrower pitches, making it difficult to achieve high-speed information processing.

[0009] The object of the present invention is to provide conductive particles that can effectively suppress the occurrence of connection failures. Another object of the present invention is to provide a connection structure using the above conductive particles. [Means for solving the problem]

[0010] As a result of diligently investigating the above problems, the inventors of this invention have found that the above problems can be solved by using specific conductive particles instead of metal terminals (metal pins).

[0011] According to a broad aspect of the present invention, there is a conductive particle comprising a base particle and a conductive portion disposed on the surface of the base particle, wherein the particle diameter of the conductive particle is 30 μm or more, and the ratio of the resistance value of the conductive particle after loading and unloading until the conductive particle is compressed and deformed by 20% 20 times to the resistance value of the conductive particle after loading and unloading until the conductive particle is compressed and deformed by 20% once is 1.5 or less.

[0012] According to a broad aspect of the present invention, there is a conductive particle comprising a base particle and a conductive portion disposed on the surface of the base particle, wherein the particle diameter of the conductive particle is 30 μm or more, and in a compression test in which loading and unloading are repeated 20 times until the conductive particle is compressed and deformed by 20%, there is no bending portion in the compression displacement-compression load curve.

[0013] In a specific aspect of the conductive particles according to the present invention, in a compression test in which the load and unloading are repeated 20 times until the conductive particles are compressed and deformed by 30%, there are no bends in the compression displacement-compression load curve.

[0014] According to a broad aspect of the present invention, there is a conductive particle comprising a base particle and a conductive portion disposed on the surface of the base particle, wherein the particle diameter of the conductive particle is 30 μm or more, and the conductive particle is used to obtain a socket or connector.

[0015] In a particular aspect of the conductive particles according to the present invention, the material of the conductive portion includes a ductile metal.

[0016] In a particular aspect of the conductive particles according to the present invention, the conductive portion has a laminated structure of two or more layers, and the layers other than the outer surface of the conductive portion include a layer containing a ductile metal.

[0017] In a specific aspect of the conductive particles according to the present invention, the material of the outer surface of the conductive portion is gold, silver, copper, tin, zinc, nickel, beryllium, cobalt, palladium, platinum, rhodium, ruthenium, iridium, or an alloy thereof.

[0018] In a specific aspect of the conductive particles according to the present invention, the thickness of the layer containing the ductile metal is 0.6 μm or more.

[0019] In a specific aspect of the conductive particles according to the present invention, the thickness of the conductive portion is 0.3 μm or more and 20 μm or less.

[0020] In a specific aspect of the conductive particles according to the present invention, the thickness of the conductive portion is 0.6 μm or more and 20 μm or less.

[0021] In a specific aspect of the conductive particles according to the present invention, the ratio of the particle diameter of the conductive particles to the thickness of the conductive portion is 5 or more and 300 or less.

[0022] In a specific aspect of the conductive particles according to the present invention, the conductive particles have a plurality of protrusions on the outer surface of the conductive portion.

[0023] In a specific aspect of the conductive particles according to the present invention, the load required to compress the conductive particles by 20% is 50 N or less.

[0024] In a specific aspect of the conductive particles according to the present invention, the load required to compress the conductive particles by 30% is 100 N or less.

[0025] According to a broad aspect of the present invention, there is provided a connection structure including a first connection target member having a first electrode on its surface, a second connection target member having a second electrode on its surface, and a connection portion having an insulating member and conductive particles, wherein the conductive particles are the above-described conductive particles, and the first electrode and the second electrode are electrically connected by the conductive particles.

Advantages of the Invention

[0026] The conductive particles according to the present invention include base material particles and a conductive portion disposed on the surface of the base material particles. In the conductive particles according to the present invention, the particle diameter of the conductive particles is 30 μm or more. In the conductive particles according to the present invention, the ratio of the resistance value of the conductive particles after repeating the loading and unloading until 20% compression deformation of the conductive particles 20 times to the resistance value of the conductive particles after performing the loading and unloading until 20% compression deformation of the conductive particles once is 1.5 or less. In the conductive particles according to the present invention, since the above configuration is provided, the occurrence of connection failure can be effectively suppressed.

[0027] The conductive particles according to the present invention include base material particles and a conductive portion disposed on the surface of the base material particles. In the conductive particles according to the present invention, the particle diameter of the conductive particles is 30 μm or more. In the conductive particles according to the present invention, in the compression displacement-compression load curve in the compression test of repeating the loading and unloading until 20% compression deformation of the conductive particles 20 times, there is no bent portion. In the conductive particles according to the present invention, since the above configuration is provided, the occurrence of connection failure can be effectively suppressed.

[0028] The conductive particles according to the present invention include base material particles and a conductive portion disposed on the surface of the base material particles. In the conductive particles according to the present invention, the particle diameter of the conductive particles is 30 μm or more. The conductive particles according to the present invention are used to obtain a socket or a connector. In the conductive particles according to the present invention, since the above configuration is provided, the occurrence of connection failure can be effectively suppressed.

Brief Description of the Drawings

[0029] [Figure 1] FIG. 1 is a cross-sectional view showing conductive particles according to the first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing conductive particles according to the second embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view showing conductive particles according to the third embodiment of the present invention. [Figure 4] Figure 4 is a schematic front cross-sectional view showing a connection structure using conductive particles according to the first embodiment of the present invention. [Figure 5] Figure 5 is a schematic front cross-sectional view showing a connection structure using metal terminals. [Figure 6] Figure 6 is a schematic diagram illustrating the presence or absence of a bent portion in a two-dimensional graph showing the compressive displacement (X axis) - compressive load (Y axis) curve in a compression test of conductive particles according to one embodiment of the present invention. [Figure 7] Figure 7 is a schematic diagram illustrating the presence or absence of a bend in a two-dimensional graph showing the compressive displacement (X axis) - compressive load (Y axis) curve in a compression test of conductive particles according to one embodiment of the present invention. [Modes for carrying out the invention]

[0030] The details of the present invention will be described below.

[0031] (Conductive particles) The conductive particles according to the present invention comprise a base particle and a conductive portion disposed on the surface of the base particle. In the conductive particles according to the present invention, the particle diameter of the conductive particles is 30 μm or more. In the conductive particles according to the present invention, the ratio of the resistance value of the conductive particles after loading and unloading until the conductive particles are compressed and deformed by 20% 20 times to the resistance value of the conductive particles after loading and unloading until the conductive particles are compressed and deformed by 20% once is 1.5 or less.

[0032] The conductive particles according to the present invention comprise a base particle and a conductive portion disposed on the surface of the base particle. In the conductive particles according to the present invention, the particle diameter of the conductive particle is 30 μm or more. In the conductive particles according to the present invention, in a compression test in which the load and unloading are repeated 20 times until the conductive particle is compressed and deformed by 20%, there are no bends in the compression displacement-compression load curve.

[0033] The conductive particles according to the present invention comprise a base particle and a conductive portion disposed on the surface of the base particle. In the conductive particles according to the present invention, the particle diameter of the conductive particles is 30 μm or more. The conductive particles according to the present invention are used to obtain a socket or connector. The conductive particles according to the present invention are conductive particles that can be used to obtain a socket or connector.

[0034] Each of the conductive particles according to the present invention is equipped with the above-described configurations, thereby effectively suppressing the occurrence of connection failures.

[0035] In recent years, the expansion of markets such as IoT, 5G communication, VR, AR, artificial intelligence, and autonomous driving systems has led to an increase in the amount of information and faster communication speeds, creating an even greater demand for faster information processing speeds in processors for data servers, PCs, and mobile devices.

[0036] Methods for processing large amounts of information at high speed include, for example, improving the processing power of the CPU (Central Processing Unit). To improve the processing power of the CPU, there is a trend towards increasing the number of pins and narrowing the pitch of the metal terminals (metal pins) on the socket (CPU socket) that connects the CPU to the motherboard.

[0037] Conventional sockets and the like make it extremely difficult to process the fine metal terminals (metal pins) needed to accommodate further increases in the number of pins and narrower pitches. Furthermore, miniaturizing the metal terminals (metal pins) reduces their strength, which can cause them to break or bend during CPU connection, resulting in connection failures.

[0038] Conventional sockets using metal terminals (metal pins) have difficulty accommodating further increases in the number of pins and narrower pitches, making it difficult to achieve high-speed information processing.

[0039] The inventors of this invention have diligently investigated the above problems and have found that these problems can be solved by using specific conductive particles instead of metal terminals (metal pins). The conductive particles according to the present invention can effectively suppress the occurrence of cracks in the conductive part even when repeatedly compressed. For this reason, they can be used instead of metal terminals (metal pins) and can accommodate further narrowing of the pitch. As a result, it is possible to accommodate the increased speed of information processing in CPUs and the like.

[0040] Furthermore, since each of the conductive particles according to the present invention is equipped with the above-described configuration, the conductive portion is less likely to crack even when repeatedly compressed, thereby effectively suppressing connection failures during CPU connection and the like.

[0041] In this invention, using specific conductive particles greatly contributes to achieving the effects described above.

[0042] In the above-mentioned conductive particles, the ratio (R20 / R1) of the resistance value (R20) of the conductive particles after loading and unloading until the conductive particles are compressed and deformed by 20% 20 times to the resistance value (R1) of the conductive particles after loading and unloading until the conductive particles are compressed and deformed by 20% once is preferably satisfied within the following range. That is, the ratio (R20 / R1) is preferably 0.5 or more, more preferably 0.8 or more, preferably 1.5 or less, and more preferably 1.3 or less. When the ratio (R20 / R1) is above the lower limit and below the upper limit, the occurrence of connection failures can be suppressed even more effectively.

[0043] The above resistance values ​​(R1) and (R20) can be measured as follows.

[0044] Using a micro-compression testing machine, a load is applied to the smooth indenter end face of a cylindrical object (500 μm in diameter, made of BeCu / Au on stainless steel) at 25°C until the conductive particles are compressed and deformed by 20% towards the center of the conductive particles. This process of loading and unloading constitutes one cycle, and a total of 20 cycles of compression testing are performed. After the first cycle, the conductivity resistance is measured in the 20% compressed state and the resistance value (R1) is recorded. Similarly, after the 20th cycle, the conductivity resistance is measured in the 20% compressed state and the resistance value (R20) is recorded. Examples of micro-compression testing machines used include the "ENT-NEXUS" from Elionix Corporation and the "Microautograph MST-I" from Shimadzu Corporation.

[0045] In the above-mentioned conductive particles, it is preferable that there are no bends in the compression displacement-compression load curve obtained in a compression test in which the load and unloading are repeated 20 times until the conductive particles are compressed and deformed by 20%. In the above-mentioned conductive particles, it is preferable that there are no bends in the compression displacement-compression load curve (compression displacement curve) obtained in a compression test in which the load and unloading are repeated 20 times until the conductive particles are compressed and deformed by 30%.

[0046] In this invention, "no bending occurs" means that, during a compression test in which loading and unloading are repeated 20 times at a loading rate of 0.3 mN / sec until 20% or 30% compression is achieved, no abrupt displacement occurs in the compression displacement curve in the two-dimensional graph showing the relationship between compression displacement (X axis) and compression load (Y axis). For example, Figure 6 shows the results of a compression test in which loading and unloading is repeated once until 20% compression is achieved. Figure 6 shows a two-dimensional graph in which no bending occurs during the compression test. Note that Figure 6 is the result of a compression test in which loading and unloading is repeated once until 20% compression is achieved, and in this invention, even in a compression test in which loading and unloading is repeated 20 times until 20% compression is achieved, no bending occurs during the compression test.

[0047] Furthermore, in this invention, "the presence of a bend" means that during a compression test in which loading and unloading are repeated 20 times at a loading rate of 0.3 mN / second until a 20% or 30% compression is achieved, a sharp displacement occurs in the compression displacement curve in a two-dimensional graph showing the relationship between compression displacement (X axis) and compression load (Y axis). The sharp displacement of the compression displacement curve is caused, for example, by the formation of large cracks along the surface of conductive particles, with a length of 50% or more of the particle diameter. For example, Figure 7 shows the results of a compression test in which loading and unloading are repeated once until a 20% compression is achieved. Figure 7 shows a two-dimensional graph in which a bend exists during the compression test.

[0048] The presence or absence of the aforementioned bent portion can be confirmed specifically as follows.

[0049] Using a microcompression testing machine, a load is applied to the smooth end face of a cylindrical (500 μm diameter, diamond) indenter at 25°C, in the direction of the conductive particles' center, under a compression speed of 0.3 mN / sec, until the conductive particles are compressed and deformed by 20% or 30%. This process of loading and unloading constitutes one cycle, and a total of 20 cycles of compression tests are performed. During this time, the compressive displacement (μm) and compressive load (mN) are measured, and the presence or absence of a bend is confirmed in the compressive displacement curve, which shows the relationship between compressive displacement (X axis) and compressive load (Y axis). Examples of microcompression testing machines used include the "ENT-NEXUS" from Elionix Corporation and the "Microautograph MST-I" from Shimadzu Corporation.

[0050] From the viewpoint of more effectively suppressing the occurrence of connection failures, it is preferable that the load required to compress and deform the conductive particles by 20% is 50 N or less.

[0051] From the viewpoint of more effectively suppressing the occurrence of connection failures, it is preferable that the load required to compress and deform the conductive particles by 30% is 100 N or less.

[0052] The particle diameter of the conductive particles is 30 μm or more. Preferably, the particle diameter of the conductive particles is 100 μm or more, more preferably 200 μm or more, even more preferably 300 μm or more, preferably 2000 μm or less, more preferably 1000 μm or less, and even more preferably 600 μm or less. When the particle diameter of the conductive particles is above the lower limit and below the upper limit, it can be used more suitably to obtain a socket or connector. When the particle diameter of the conductive particles is above the lower limit and below the upper limit, the contact area between the conductive particles and the electrode can be sufficiently large, and aggregated conductive particles are less likely to form when forming the conductive part, and the conductive part is less likely to peel off from the surface of the base particle.

[0053] The particle diameter of the conductive particles described above is preferably the average particle diameter, and more preferably the number-average particle diameter. The particle diameter of the conductive particles can be determined, for example, by observing 50 arbitrary conductive particles with an electron microscope or optical microscope and calculating the average particle diameter of each conductive particle, or by using a particle size distribution analyzer. In observation with an electron microscope or optical microscope, the particle diameter of a single conductive particle is determined as the particle diameter at the equivalent diameter of a circle. In observation with an electron microscope or optical microscope, the average particle diameter at the equivalent diameter of a circle of any 50 conductive particles is approximately equal to the average particle diameter at the equivalent diameter of a sphere. In a particle size distribution analyzer, the particle diameter of a single conductive particle is determined as the particle diameter at the equivalent diameter of a sphere. It is preferable to calculate the average particle diameter of the conductive particles using a particle size distribution analyzer.

[0054] The coefficient of variation (CV value) of the particle size of the conductive particles is preferably 10% or less, more preferably 5% or less. When the coefficient of variation of the particle size of the conductive particles is below the upper limit, the contact area between the conductive particles and the electrode can be sufficiently large.

[0055] The coefficient of variation (CV value) mentioned above can be measured as follows.

[0056] CV value (%) = (ρ / Dn) × 100 ρ: Standard deviation of the particle size of conductive particles Dn: Average particle size of conductive particles

[0057] The shape of the conductive particles is not particularly limited. The conductive particles may be spherical, or other shapes, such as a rectangular prism, cylindrical shape, or flattened shape.

[0058] The present invention will be described in detail below with reference to the drawings.

[0059] Figure 1 is a cross-sectional view showing conductive particles according to the first embodiment of the present invention.

[0060] The conductive particle 1 shown in Figure 1 has a base particle 2 and a conductive portion 3. The conductive portion 3 is arranged on the surface of the base particle 2. In the first embodiment, the conductive portion 3 is in contact with the surface of the base particle 2. The conductive particle 1 is a coated particle in which the surface of the base particle 2 is covered with the conductive portion 3.

[0061] In conductive particle 1, the conductive portion 3 is a single-layer conductive layer. In conductive particle 1, the base particle 2 contains a conductive metal inside the base particle 2. In the conductive particle, the conductive portion may cover the entire surface of the base particle, or it may cover a part of the surface of the base particle. In the conductive particle, the conductive portion may be a single-layer conductive layer, or it may be a multilayer conductive layer composed of two or more layers.

[0062] Unlike the conductive particles 11 and 21 described later, conductive particle 1 does not have a core material. Conductive particle 1 does not have protrusions on its surface. Conductive particle 1 is spherical. The conductive part 3 does not have protrusions on its outer surface. Thus, the conductive particles according to the present invention do not need to have protrusions on their conductive surface, and may be spherical.

[0063] Figure 2 is a cross-sectional view showing conductive particles according to a second embodiment of the present invention.

[0064] The conductive particle 11 shown in Figure 2 comprises a base particle 2, a conductive portion 12, and a plurality of core materials 13. The conductive portion 12 is arranged on the surface of the base particle 2 so as to be in contact with the base particle 2.

[0065] In the conductive particle 11, the conductive portion 12 is a single-layer conductive layer. In the conductive particle 11, the base particle 2 contains a conductive metal inside the base particle 2. In the conductive particle, the conductive portion may cover the entire surface of the base particle, or it may cover a part of the surface of the base particle. In the conductive particle, the conductive portion may be a single-layer conductive layer, or it may be a multilayer conductive layer composed of two or more layers.

[0066] The conductive particle 11 has a plurality of protrusions 11a on its conductive surface. The conductive portion 12 has a plurality of protrusions 12a on its outer surface. A plurality of core materials 13 are arranged on the surface of the base particle 2. The plurality of core materials 13 are embedded within the conductive portion 12. The core materials 13 are positioned inside the protrusions 11a and 12a. The conductive portion 12 covers the plurality of core materials 13. The outer surface of the conductive portion 12 is raised by the plurality of core materials 13, forming the protrusions 11a and 12a.

[0067] Figure 3 is a cross-sectional view showing conductive particles according to a third embodiment of the present invention.

[0068] The conductive particle 21 shown in Figure 3 comprises a base particle 2, a conductive portion 22, and a plurality of core materials 13. The conductive portion 22 as a whole has a first conductive portion 22A on the base particle 2 side and a second conductive portion 22B on the side opposite to the base particle 2.

[0069] The conductive particles 11 and 21 differ only in their conductive portions. Specifically, conductive particles 11 have a single-layer conductive portion 12, while conductive particles 21 have a two-layer structure consisting of a first conductive portion 22A and a second conductive portion 22B. The first conductive portion 22A and the second conductive portion 22B are formed as separate conductive portions.

[0070] The first conductive portion 22A is located on the surface of the base particle 2. The first conductive portion 22A is located between the base particle 2 and the second conductive portion 22B. The first conductive portion 22A is in contact with the base particle 2. The second conductive portion 22B is in contact with the first conductive portion 22A. Therefore, the first conductive portion 22A is located on the surface of the base particle 2, and the second conductive portion 22B is located on the surface of the first conductive portion 22A. The conductive particle 21 has a plurality of protrusions 21a on its conductive surface. The conductive portion 22 has a plurality of protrusions 22a on its outer surface. The first conductive portion 22A has a plurality of protrusions 22Aa on its outer surface. The second conductive portion 22B has a plurality of protrusions 22Ba on its outer surface.

[0071] Further details about conductive particles are described below.

[0072] (base material particles) The material of the above-mentioned base material particles is not particularly limited. The material of the above-mentioned base material particles may be an organic material or an inorganic material. Examples of base material particles formed solely from the above-mentioned organic material include resin particles. Examples of base material particles formed solely from the above-mentioned inorganic material include inorganic particles excluding metals. Examples of base material particles formed from both the above-mentioned organic material and the above-mentioned inorganic material include organic-inorganic hybrid particles. From the viewpoint of further improving the compressibility of the base material particles, the above-mentioned base material particles are preferably resin particles or organic-inorganic hybrid particles, and more preferably resin particles.

[0073] Examples of the above organic materials include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; 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, polyethylene terephthalate, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyamide-imide, polyetheretherketone, polyethersulfone, divinylbenzene polymer, and divinylbenzene copolymer. Examples of the above divinylbenzene copolymer include divinylbenzene-styrene copolymer and divinylbenzene-(meth)acrylic acid ester copolymer. Since the compression characteristics of the above-mentioned base material particles can be easily controlled to a suitable range, it is preferable that the material of the above-mentioned base material particles is a polymer obtained by polymerizing one or more polymerizable monomers having ethylenically unsaturated groups.

[0074] When the above-mentioned base material particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, the polymerizable monomer having an ethylenically unsaturated group can be a non-crosslinked monomer or a crosslinked monomer.

[0075] The above non-crosslinked monomers include vinyl compounds such as styrene monomers like styrene, α-methylstyrene, and chlorostyrene; vinyl ether compounds such as methyl vinyl ether, ethyl vinyl ether, and propyl vinyl ether; vinyl acid ester compounds such as vinyl acetate, vinyl butyrate, vinyl laurate, and vinyl stearate; halogen-containing monomers such as vinyl chloride and vinyl fluoride; and (meth)acrylic compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, and cyclohexyl Alkyl (meth)acrylate compounds such as (meth)acrylate and isobornyl (meth)acrylate; oxygen atom-containing (meth)acrylate compounds such as 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate; nitrile-containing monomers such as (meth)acrylonitrile; halogen-containing (meth)acrylate compounds such as trifluoromethyl (meth)acrylate and pentafluoroethyl (meth)acrylate; olefin compounds such as diisobutylene, isobutylene, linearene, ethylene, and propylene as α-olefin compounds; and isoprene and butadiene as conjugated diene compounds.

[0076] The above crosslinkable monomers include vinyl monomers such as divinylbenzene, 1,4-divinyloxybutane, and divinylsulfone; polyfunctional (meth)acrylate compounds such as tetramethylolmethane tetra(meth)acrylate, polytetramethylene glycol diacrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate; and allyl compounds. Examples include triallyl(iso)cyanurate, triallyl trimellitate, diallyl phthalate, diallyl acrylamide, and diallyl ether; as silane compounds, silane alkoxide compounds such as tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, isopropyltrimethoxysilane, isobutyltrimethoxysilane, cyclohexyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diisopropyldimethoxysilane, trimethoxysilylstyrene, γ-(meth)acryloxypropyltrimethoxysilane, 1,3-divinyltetramethyldisiloxane, methylphenyldimethoxysilane, and diphenyldimethoxysilane;Examples include polymerizable double-bond-containing silane alkoxides such as vinyltrimethoxysilane, vinyltriethoxysilane, dimethoxymethylvinylsilane, dimethoxyethylvinylsilane, diethoxymethylvinylsilane, diethoxyethylvinylsilane, ethylmethyldivinylsilane, methylvinyldimethoxysilane, ethylvinyldimethoxysilane, methylvinyldiethoxysilane, ethylvinyldiethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane; cyclic siloxanes such as decamethylcyclopentasiloxane; modified (reactive) silicone oils such as one-ended modified silicone oil, two-ended silicone oil, and side-chain type silicone oil; and carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride.

[0077] The above-mentioned substrate particles can be obtained by polymerizing the polymerizable monomer having the above-mentioned ethylenically unsaturated group. The polymerization method is not particularly limited and includes known methods such as radical polymerization, ionic polymerization, polycondensation (condensation polymerization, condensation polymerization), addition condensation, living polymerization, and living radical polymerization. Another polymerization method is suspension polymerization in the presence of a radical polymerization initiator.

[0078] Examples of the inorganic materials mentioned above include silica, alumina, barium titanate, zirconia, carbon black, silicate glass, borosilicate glass, lead glass, soda-lime glass, and alumina silicate glass.

[0079] The above-mentioned base material particles may be organic-inorganic hybrid particles. The above-mentioned base material particles may also be core-shell particles. When the above-mentioned base material particles are organic-inorganic hybrid particles, examples of inorganic materials for the above-mentioned base material particles include silica, alumina, barium titanate, zirconia, and carbon black. It is preferable that the above-mentioned inorganic material is not a metal. The above-mentioned base material particles formed from silica are not particularly limited, but examples include base material particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, and then firing as necessary. Examples of the above-mentioned organic-inorganic hybrid particles include organic-inorganic hybrid particles formed from a crosslinked alkoxysilyl polymer and an acrylic resin.

[0080] The above organic-inorganic hybrid particles are preferably core-shell type organic-inorganic hybrid particles having a core and a shell disposed on the surface of the core. The core is preferably an organic core. The shell is preferably an inorganic shell. The above substrate particles are preferably organic-inorganic hybrid particles having an organic core and an inorganic shell disposed on the surface of the organic core.

[0081] Examples of materials for the above-mentioned organic core include the organic materials mentioned above.

[0082] Examples of materials for the inorganic shell include the inorganic substances listed above as materials for the base particles. The material for the inorganic shell is preferably silica. The inorganic shell is preferably formed by forming a shell-like substance from a metal alkoxide on the surface of the core using a sol-gel method, and then firing the shell-like substance. The metal alkoxide is preferably a silane alkoxide. The inorganic shell is preferably formed from a silane alkoxide.

[0083] The particle size of the above-mentioned base material particles is preferably 30 μm or larger. The particle size of the above-mentioned base material particles is preferably 100 μm or larger, more preferably 200 μm or larger, even more preferably 300 μm or larger, preferably 2000 μm or smaller, more preferably 1000 μm or smaller, and even more preferably 600 μm or smaller. When the particle size of the above-mentioned base material particles is above the lower limit and below the upper limit, it can be used more suitably to obtain a socket or connector. When the particle size of the above-mentioned base material particles is above the lower limit and below the upper limit, the contact area between the conductive particles and the electrode can be sufficiently large, and it becomes difficult for aggregated conductive particles to form when forming the conductive part, and the conductive part becomes less likely to peel off from the surface of the base material particles.

[0084] The particle size of the above-mentioned base material particles is particularly preferably 30 μm or more and 1000 μm or less. When the particle size of the above-mentioned base material particles is within the range of 30 μm or more and 1000 μm or less, aggregation becomes less likely when forming a conductive portion on the surface of the base material particles, and aggregated conductive particles are less likely to be formed. Furthermore, when the particle size of the above-mentioned base material particles is within the range of 100 μm or more and 800 μm or less, it can be used even more suitably to obtain sockets or connectors.

[0085] The particle size of the above-mentioned base material particles refers to the diameter if the base material particles are spherical, and if the base material particles are not spherical, it refers to the diameter assuming they are spherical to the extent of their volume.

[0086] The particle diameter of the above-mentioned substrate particles represents the number-average particle diameter. The particle diameter of the above-mentioned substrate particles can be determined by observing 50 arbitrary substrate particles with an electron microscope or optical microscope and calculating the average particle diameter of each substrate particle, or by using a particle size distribution analyzer. When observing with an electron microscope or optical microscope, the particle diameter of a single substrate particle is determined as the particle diameter at the equivalent diameter of a circle. When observing with an electron microscope or optical microscope, the average particle diameter at the equivalent diameter of a circle of any 50 substrate particles is approximately equal to the average particle diameter at the equivalent diameter of a sphere. When using a particle size distribution analyzer, the particle diameter of a single substrate particle is determined as the particle diameter at the equivalent diameter of a sphere. It is preferable to calculate the average particle diameter of the above-mentioned substrate particles using a particle size distribution analyzer. When measuring the particle diameter of conductive particles, for example, it can be measured as follows.

[0087] A resin body for conductive particle testing is prepared by adding conductive particles to Kulzer's "Technovit 4000" so that the conductive particle content is 30% by weight, and then dispersing them. A cross-section of the conductive particles is cut out using an ion milling device (Hitachi High-Technologies Corporation's "IM4000") so as to pass through the vicinity of the center of the conductive particles dispersed in the resin body for testing. Then, using a field emission scanning electron microscope (FE-SEM), 50 conductive particles are randomly selected, and the base particles of each conductive particle are observed. The particle diameter of the base particles in each conductive particle is measured, and these are arithmetic mean to obtain the particle diameter of the base particles.

[0088] (Conductive part) The conductive particles according to the present invention comprise a base particle and a conductive portion disposed on the surface of the base particle. The conductive portion preferably contains a metal. The metal constituting the conductive portion is not particularly limited.

[0089] Examples of metals constituting the conductive part and conductive metals include gold, silver, palladium, copper, platinum, zinc, iron, tin, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, beryllium, rhodium, ruthenium, iridium, bismuth, thallium, germanium, cadmium, silicon, tungsten, molybdenum, and alloys thereof. Examples of metals constituting the conductive part and conductive metals include tin-doped indium oxide (ITO) and solder. Only one type of metal may be used to constitute the conductive part, or two or more types may be used in combination.

[0090] From the viewpoint of more effectively lowering the connection resistance, the conductive part preferably contains nickel, gold, palladium, beryllium, cobalt, tin, silver, or copper, and more preferably contains nickel, gold, or copper.

[0091] From the viewpoint of more effectively suppressing the occurrence of cracks in the conductive part and more effectively suppressing the occurrence of connection failures, it is preferable that the material of the conductive part contains a ductile metal. It is preferable that the ductile metal has ductility. Specifically, it is preferable that the ductile metal has an elongation rate of 5% to 65% at 23°C, and more preferably 10% to 60% at 23°C. Examples of the ductile metal include gold, copper, zinc, tin, aluminum, titanium, and alloys thereof. Only one type of ductile metal may be used, or two or more types may be used in combination.

[0092] Furthermore, the elongation rate of the above-mentioned ductile metal at 23°C can be measured as follows.

[0093] A 1 μm thick ductile metal film is deposited on one side of a PET film (G2) (manufactured by Teijin DuPont, 20 mm x 50 mm size) using a ductile metal. A tensile test is performed, and the elongation at the point when the ductile metal film breaks is measured. The above elongation is measured using a tensile testing apparatus (Shimadzu Corporation "EZ-LX HS") at 23°C and a test speed of 1 mm / min. From the obtained results, the elongation rate is calculated using the following formula.

[0094] Growth rate (%) = (L1 - L0) / L0 × 100 L1: Length of the ductile metal film at break L0: Length of the ductile metal film before testing

[0095] The content of the ductile metal in 100% by weight of the metal material of the conductive part is preferably 10% by weight or more, more preferably 20% by weight or more, and even more preferably 40% by weight or more. There is no particular upper limit to the content of the ductile metal in 100% by weight of the metal material of the conductive part. The content of the ductile metal in 100% by weight of the metal material of the conductive part may be 100% by weight (total amount) or less than 100% by weight. If the content of the ductile metal is above the lower limit, the occurrence of cracks in the conductive part can be suppressed more effectively, and the occurrence of connection failures can be suppressed more effectively.

[0096] From the viewpoint of more effectively suppressing the occurrence of cracks in the conductive part and more effectively suppressing the occurrence of connection failures, the ductile metal preferably contains copper, tin, or zinc, more preferably contains copper or tin, and even more preferably contains copper.

[0097] In the conductive part containing copper, the copper content is preferably 10% by weight or more, more preferably 20% by weight or more, and even more preferably 40% by weight or more. There is no particular upper limit to the copper content in the conductive part containing copper. The copper content may be 90% by weight or less. When the copper content is above the lower limit, the occurrence of cracks in the conductive part can be suppressed more effectively, and the occurrence of connection failures can be suppressed more effectively.

[0098] The conductive part may be formed from a single layer. The conductive part may be formed from multiple layers. The conductive part may have a two-layer laminated structure, a two-layer or more-layer laminated structure, a three-layer laminated structure, or a three-layer or more-layer laminated structure. From the viewpoint of more effectively suppressing the occurrence of cracks in the conductive part and more effectively suppressing the occurrence of connection failures, it is preferable that the conductive part has a two-layer or more-layer laminated structure.

[0099] When the conductive part has a laminated structure of two or more layers, the material other than the outer surface of the conductive part preferably contains a ductile metal, and more preferably contains copper, tin, or an alloy thereof. When the material other than the outer surface of the conductive part is the above-mentioned preferred metal (ductile metal), the occurrence of cracks in the conductive part can be suppressed more effectively, and the occurrence of connection failures can be suppressed more effectively.

[0100] If the conductive part has a laminated structure of two or more layers, it is preferable that the conductive part includes a layer containing a ductile metal. If the conductive part has a laminated structure of two or more layers, it is preferable that the layers other than the outer surface of the conductive part include a layer containing a ductile metal. By having a layer other than the outer surface of the conductive part include a layer containing the ductile metal, the occurrence of cracks in the conductive part can be suppressed even more effectively, and the occurrence of connection failures can be suppressed even more effectively. In particular, if the outer surface is not a layer containing the ductile metal, the presence of a layer containing the ductile metal in the layers other than the outer surface can further effectively suppress the occurrence of cracks in the conductive part, and the occurrence of connection failures can be suppressed even more effectively.

[0101] In 100% by weight of the metal material that makes up the layer containing the above-mentioned malleable metal, the content of the above-mentioned malleable metal is preferably 30% by weight or more, more preferably 60% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more. There is no particular upper limit to the content of the above-mentioned malleable metal in 100% by weight of the metal material that makes up the layer containing the above-mentioned malleable metal. The content of the above-mentioned malleable metal in 100% by weight of the metal material that makes up the layer containing the above-mentioned malleable metal may be 100% by weight (total amount) or less than 100% by weight. If the content of the above-mentioned malleable metal is above the lower limit, the occurrence of cracks in the conductive part can be suppressed more effectively, and the occurrence of connection failures can be suppressed more effectively.

[0102] The thickness of the layer containing the ductile metal is preferably 0.6 μm or more, more preferably 1.0 μm or more, even more preferably 2.0 μm or more, and particularly preferably 4.0 μm or more. If the thickness of the layer containing the ductile metal is above the lower limit, the occurrence of cracks in the conductive part can be suppressed more effectively, and the occurrence of connection failures can be suppressed more effectively. The thickness of the layer containing the ductile metal is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 6 μm or less. If the thickness of the layer containing the ductile metal is below the upper limit, compressive deformation when force is applied perpendicularly to the conductive particles is not inhibited, and the contact area with the connecting member can be secured, thereby stabilizing the conductivity resistance. If there are multiple layers containing ductile metal, the above effects can be obtained if the total thickness of the layers containing ductile metal is above the lower limit and below the upper limit.

[0103] If the conductive part has a laminated structure of two or more layers, the material of the outer surface of the conductive part is preferably gold, silver, copper, tin, zinc, nickel, beryllium, cobalt, palladium, platinum, rhodium, ruthenium, iridium, or an alloy thereof, and more preferably gold, copper, or an alloy thereof. If the material of the outer surface of the conductive part is one of the preferred metals described above, the connection resistance can be more effectively reduced and the corrosion resistance can be more effectively increased.

[0104] The method for forming the conductive portion on the surface of the above-mentioned substrate particles is not particularly limited. Examples of methods for forming the conductive portion include electroless plating, electroplating, physical impact, mechanochemical reaction, physical vapor deposition or physical adsorption, and coating the surface of the substrate particles with metal powder or a paste containing metal powder and a binder. The method for forming the conductive portion is preferably electroless plating, electroplating, or physical impact. Examples of physical vapor deposition include vacuum deposition, ion plating, and ion sputtering. As for the physical impact method, a theta composer (manufactured by Tokuju Kogyo Co., Ltd.) can be used.

[0105] The thickness of the conductive portion is preferably 0.3 μm or more, more preferably 0.6 μm or more, even more preferably 1 μm or more, preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. The thickness of the conductive portion refers to the total thickness of the conductive portion if the conductive portion has a laminated structure of two or more layers. When the thickness of the conductive portion is above the lower limit and below the upper limit, the occurrence of cracks in the conductive portion can be suppressed more effectively, and the occurrence of connection failures can be suppressed more effectively. Furthermore, when the thickness of the conductive portion is above the lower limit and below the upper limit, sufficient conductivity can be obtained, and the hardening of the conductive particles can be prevented.

[0106] When the conductive portion has a laminated structure of two or more layers, the thickness of the outermost conductive layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, preferably 10 μm or less, and more preferably 8 μm or less. When the thickness of the outermost conductive layer is above the lower limit and below the upper limit, the coating by the outermost conductive layer becomes more uniform, and corrosion resistance can be more effectively improved. Furthermore, when the metal constituting the outermost layer is gold, the thinner the outermost layer, the lower the cost can be.

[0107] The thickness of the conductive portion can be measured, for example, by observing the cross-section of the conductive particle using a transmission electron microscope (TEM). It is preferable to calculate the thickness of the conductive portion of a single conductive particle by averaging the thickness of five arbitrary conductive portion thicknesses, and more preferably by averaging the thickness of the entire conductive portion. It is also preferable to determine the thickness of the conductive portion of a single conductive particle by calculating the average thickness of the conductive portion of each of 10 arbitrary conductive particles.

[0108] The ratio of the particle diameter of the conductive particles to the thickness of the conductive part (particle diameter of conductive particles / thickness of conductive part) is preferably 5 or more, more preferably 10 or more, even more preferably 20 or more, preferably 800 or less, more preferably 650 or less, and even more preferably 300 or less. When the above ratio (particle diameter of conductive particles / thickness of conductive part) is above the lower limit and below the upper limit, the occurrence of cracks in the conductive part can be suppressed more effectively, and the occurrence of connection failures can be suppressed more effectively.

[0109] (core substance) The conductive particles preferably have protrusions on the outer surface of the conductive portion. The conductive particles preferably have protrusions on the conductive surface. The protrusions preferably number in number. An oxide film is often formed on the surface of the electrode that comes into contact with the conductive particles. When conductive particles with protrusions on the surface of the conductive portion are used, the oxide film can be effectively removed by the protrusions by pressing the conductive particles and the electrode together. As a result, the electrode and the conductive portion make contact more reliably, the contact area between the conductive particles and the electrode can be sufficiently increased, and the connection resistance can be reduced more effectively. Furthermore, when conductive particles are dispersed in a binder and used as a conductive material, the protrusions of the conductive particles can more effectively remove the binder between the conductive particles and the electrode. As a result, the contact area between the conductive particles and the electrode can be sufficiently increased, and the connection resistance can be reduced more effectively.

[0110] Methods for forming the above-mentioned protrusions include a method in which a core material is attached to the surface of a base particle and then a conductive part is formed by electroless plating, and a method in which a conductive part is formed on the surface of a base particle by electroless plating, then a core material is attached, and then a conductive part is formed by electroless plating. Furthermore, it is not necessary to use the above-mentioned core material to form the above-mentioned protrusions.

[0111] Other methods for forming the above-mentioned protrusions include adding a core material during the process of forming the conductive portion on the surface of the substrate particles. Alternatively, to form the protrusions, a method may be used in which a conductive portion is formed on the substrate particles by electroless plating without using the above-mentioned core material, then plating is deposited in a protruding manner on the surface of the conductive portion, and then the conductive portion is formed by further electroless plating.

[0112] Methods for attaching a core material to the surface of base particles include adding the core material to a dispersion of base particles and accumulating and attaching the core material to the surface of the base particles by van der Waals forces, and adding the core material to a container containing base particles and attaching the core material to the surface of the base particles by mechanical action such as rotating the container. From the viewpoint of controlling the amount of core material to be attached, the method of attaching the core material to the surface of base particles is preferably one in which the core material is accumulated and attached to the surface of the base particles in a dispersion.

[0113] The materials constituting the core material mentioned above include conductive materials and non-conductive materials. Examples of conductive materials include metals, metal oxides, conductive nonmetals such as graphite, and conductive polymers. Examples of conductive polymers include polyacetylene. Examples of non-conductive materials include silica, alumina, titanium oxide, and zirconia. From the viewpoint of more effectively eliminating oxide films, it is preferable that the core material be hard. From the viewpoint of more effectively lowering the connection resistance between electrodes, it is preferable that the core material be a metal.

[0114] The above metals are not particularly limited. Examples of the above metals include gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, as well as alloys composed of two or more metals such as tin-lead alloys, tin-copper alloys, tin-silver alloys, tin-lead-silver alloys, and tungsten carbide. From the viewpoint of more effectively lowering the connection resistance between electrodes, the above metals are preferably nickel, copper, silver, or gold. The above metals may be the same as or different from the metals constituting the conductive part (conductive layer).

[0115] The shape of the core material is not particularly limited. The core material is preferably in the form of a lump. Examples of core material include particulate lumps, aggregates formed by the aggregation of multiple fine particles, and irregularly shaped lumps.

[0116] The particle size of the core material is preferably 0.001 μm or larger, more preferably 0.05 μm or larger, more preferably 0.9 μm or smaller, and more preferably 0.2 μm or smaller. When the particle size of the core material is above the lower limit and below the upper limit, the connection resistance between electrodes can be reduced even more effectively.

[0117] The particle diameter of the core material described above is preferably the average particle diameter, and more preferably the number-average particle diameter. The particle diameter of the core material can be determined by observing 50 arbitrary core materials with an electron microscope or optical microscope and calculating the average particle diameter of each core material, or by using a particle size distribution analyzer. In observation with an electron microscope or optical microscope, the particle diameter of one core material is determined as the particle diameter at the equivalent diameter of a circle. In observation with an electron microscope or optical microscope, the average particle diameter at the equivalent diameter of a circle of any 50 core materials is approximately equal to the average particle diameter at the equivalent diameter of a sphere. In a particle size distribution analyzer, the particle diameter of one core material is determined as the particle diameter at the equivalent diameter of a sphere. It is preferable to calculate the average particle diameter of the core material described above using a particle size distribution analyzer.

[0118] The number of protrusions per conductive particle is preferably three or more, more preferably five or more. There is no particular upper limit to the number of protrusions. The upper limit of the number of protrusions can be appropriately selected considering the particle size of the conductive particles, etc. If the number of protrusions is above the lower limit, the connection resistance between electrodes can be lowered even more effectively.

[0119] The number of protrusions can be calculated by observing any conductive particle with an electron microscope or optical microscope. Preferably, the number of protrusions is determined by observing 50 arbitrary conductive particles with an electron microscope or optical microscope and calculating the average number of protrusions on each conductive particle.

[0120] The height of the above-mentioned protrusion 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 height of the above-mentioned protrusion is above the lower limit and below the upper limit, the connection resistance between electrodes can be reduced even more effectively.

[0121] The height of the above-mentioned protrusions can be calculated by observing the protrusions on any conductive particle using an electron microscope or an optical microscope. Preferably, the height of the protrusions on a single conductive particle is calculated by taking the average height of all the protrusions on that conductive particle as the height of the protrusions on that single conductive particle. Preferably, the height of the protrusions can be determined by calculating the average height of the protrusions on 50 arbitrary conductive particles.

[0122] (Application) The conductive particles described above are preferably used to obtain sockets or connectors. The conductive particles described above are preferably used in place of metal terminals (metal pins) to obtain sockets or connectors. The conductive particles described above are preferably used in socket or connector applications. The conductive particles described above are preferably used in place of metal terminals (metal pins) to obtain sockets or connector applications. By using the conductive particles described above instead of metal terminals (metal pins), it is possible to accommodate further narrowing of the pitch and effectively suppress the occurrence of connection failures when connecting a CPU, etc. Examples of the sockets described above include CPU sockets, IC sockets, DIP sockets, PGA sockets, SiP sockets, LGA sockets, CSP sockets, QFN, QFP sockets, SOP sockets, and BGA sockets. Note that DIP sockets, PGA sockets, SiP sockets, LGA sockets, CSP sockets, QFN, QFP sockets, SOP sockets, and BGA sockets may each be part of an IC socket. Examples of the connectors described above include FPC connectors, board-to-board connectors, narrow-pitch connectors, DIN connectors, compression connectors, one-piece connectors, and card edge connectors.

[0123] (Conductive materials) The conductive particles are preferably dispersed in a binder and used as a conductive material. The conductive material comprises the conductive particles and a binder. The conductive particles are preferably dispersed in the binder and used as a conductive material. The conductive material is preferably used for electrical connections between electrodes. In the conductive material, since the conductive particles described above are used, the connection resistance between electrodes can be more effectively reduced, and the occurrence of aggregation between conductive particles can be more effectively suppressed. In the conductive material, since the conductive particles described above are used, the occurrence of connection failures can be more effectively suppressed.

[0124] The above-mentioned binder is not particularly limited. Known insulating resins and solvents can be used as the binder. The binder preferably contains a thermoplastic component (thermoplastic compound) or a curable component, and more preferably contains a curable component. Examples of the curable component include a photocurable component and a thermosetting component. The photocurable component preferably contains a photocurable compound and a photopolymerization initiator. The thermosetting component preferably contains a thermosetting compound and a thermosetting agent.

[0125] Examples of the binders mentioned above include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, elastomers, and solvents. Only one type of binder may be used, or two or more types may be used in combination.

[0126] Examples of vinyl resins include vinyl acetate resin, acrylic resin, and styrene resin. Examples of thermoplastic resins include polyolefin resin, ethylene-vinyl acetate copolymer, and polyamide resin. Examples of curable resins include epoxy resin, urethane resin, polyimide resin, and unsaturated polyester resin. The curable resin may be a room-temperature curing resin, a thermosetting resin, a photocuring resin, or a moisture-curing resin. The curable resin may be used in combination with a curing agent. Examples of thermoplastic block copolymers include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, and hydrogenated styrene-isoprene-styrene block copolymer. Examples of elastomers include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.

[0127] Examples of the above solvents include water and organic solvents. Organic solvents are preferred because they can be easily removed. Examples of the above organic solvents include alcohol compounds such as ethanol, ketone compounds such as acetone, methyl ethyl ketone, and cyclohexanone, aromatic hydrocarbon compounds such as toluene, xylene, and tetramethylbenzene, glycol ether compounds such as cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, and tripropylene glycol monomethyl ether, ester compounds such as ethyl acetate, butyl acetate, butyl lactate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and propylene carbonate, aliphatic hydrocarbon compounds such as octane and decane, and petroleum-based solvents such as petroleum ether and naphtha.

[0128] In addition to the conductive particles and binder, the conductive material may also contain various additives such as fillers, bulking agents, softeners, plasticizers, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents, and flame retardants.

[0129] The method for dispersing the conductive particles in the binder is not particularly limited and can be any conventionally known dispersion method. Examples of methods for dispersing the conductive particles in the binder include the following: A method in which the conductive particles are added to the binder and then mixed and dispersed using a planetary mixer or the like. A method in which the conductive particles are uniformly dispersed in water or an organic solvent using a homogenizer or the like, then added to the binder and mixed and dispersed using a planetary mixer or the like. A method in which the binder is diluted with water or an organic solvent, then the conductive particles are added and mixed and dispersed using a planetary mixer or the like.

[0130] The viscosity (η25) of the conductive material at 25°C is preferably 30 Pa·s or more, more preferably 50 Pa·s or more, preferably 400 Pa·s or less, and more preferably 300 Pa·s or less. When the viscosity of the conductive material at 25°C is above the lower limit and below the upper limit, the conductive material can be applied more uniformly to the member to be connected, and the occurrence of connection failures can be suppressed more effectively. The viscosity (η25) can be appropriately adjusted depending on the type and amount of the compounding components.

[0131] The viscosity (η25) described above can be measured, for example, using an E-type viscometer (TVE22L manufactured by Toki Sangyo Co., Ltd.) under conditions of 25°C and 5 rpm.

[0132] The conductive material described above can be used as a conductive paste, a conductive film, or the like. If the conductive material is a conductive film, a film without conductive particles may be laminated onto a conductive film containing conductive particles. The conductive paste is preferably an anisotropic conductive paste. The conductive film is preferably an anisotropic conductive film.

[0133] In 100% by weight of the conductive material, the binder content is preferably 10% by weight or more, more preferably 30% by weight or more, even more preferably 50% by weight or more, particularly preferably 70% by weight or more, preferably 99.99% by weight or less, and more preferably 99.9% by weight or less. When the binder content is above the lower limit and below the upper limit, conductive particles are efficiently arranged on the members to be connected, and the occurrence of connection failures can be suppressed even more effectively.

[0134] In 100% by weight of the above conductive material, the content of the above conductive particles is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, preferably 80% by weight or less, more preferably 60% by weight or less, even more preferably 40% by weight or less, particularly preferably 20% by weight or less, and most preferably 10% by weight or less. When the content of the above conductive particles is above the lower limit and below the upper limit, the conductive particles are efficiently arranged on the member to be connected, and the occurrence of connection failures can be suppressed even more effectively.

[0135] (Connection structure) The connection structure according to the present invention comprises a first connection target member having a first electrode on its surface, a second connection target member having a second electrode on its surface, and a connection portion having an insulating member and conductive particles. In the connection structure according to the present invention, the conductive particles are the conductive particles described above. In the connection structure according to the present invention, the first electrode and the second electrode are electrically connected by the conductive particles.

[0136] The above-mentioned connection portion is preferably a socket portion formed by a socket, or a connector portion formed by a connector.

[0137] Figure 4 is a schematic front cross-sectional view showing a connection structure using conductive particles according to the first embodiment of the present invention.

[0138] The connection structure 51 shown in Figure 4 comprises a first connection target member 52, a second connection target member 53, and a connection portion 54. The first connection target member 52 has a plurality of first electrodes 52a on its surface (upper surface). The second connection target member 53 has a plurality of second electrodes 53a on its surface (lower surface). The connection portion 54 comprises conductive particles 1, an insulating member 31, a solder paste portion 32, electrodes 33, and solder balls 34. The connection portion 54 is a socket portion. The insulating member 31 has a through-hole 31a that penetrates from the upper surface to the lower surface.

[0139] A solder ball 34 is placed on the first electrode 52a. An insulating member 31 is placed on the solder ball 34. An electrode 33 is placed on the insulating member 31. A solder paste portion 32 is placed on the electrode 33. Conductive particles 1 are placed on the solder paste portion 32. A second electrode 53a is placed on the conductive particles 1. Conductive paste for via filling is placed inside the through-hole 31a.

[0140] One solder ball 34, one electrode 33, one solder paste portion 32, one conductive particle 1, and one second electrode 53a are electrically connected to one first electrode 52a. Therefore, in the connection structure 51, the first electrode 52a and the second electrode 53a are electrically connected by the conductive particle 1.

[0141] Note that in Figure 4, conductive particle 1 is shown schematically for illustrative purposes. Other conductive particles such as conductive particles 11 and 21 may be used instead of conductive particle 1.

[0142] In the connection structure according to the present invention, since the conductive particles described above are used, the occurrence of cracks in the conductive part can be effectively suppressed even when the conductive particles are repeatedly compressed. For this reason, it can be used in place of metal terminals (metal pins) and can accommodate even narrower pitches. Furthermore, since the conductive particles according to the present invention can make the conductive part less prone to cracking even when repeatedly compressed, the occurrence of connection failures during CPU connection and the like can be effectively suppressed.

[0143] Examples of materials for the insulating member include ceramics and resins. Examples of resins include fluororesins, phenolic resins, epoxy resins, and polyimide resins. Examples of substrates on which the insulating member is provided include FR-1, FR-2, FR-3, FR-4, FR-5, XPC, CEM-1, CEM-3, glass polyimide substrates, glass PPO substrates, and BT substrates.

[0144] The first and second connection target members described above are not particularly limited. Examples of the first connection target member include a motherboard. Examples of the second connection target member include a semiconductor chip, IC package, CPU, etc.

[0145] Examples of electrodes provided on the first and second connected members include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, SUS electrodes, and tungsten electrodes. In the case of aluminum electrodes, they may be electrodes formed solely of aluminum, or electrodes in which an aluminum layer is laminated on the surface of a metal oxide layer. Examples of materials for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of trivalent metal elements include Sn, Al, and Ga.

[0146] The present invention will be specifically described below with reference to examples and comparative examples. The present invention is not limited to the following examples.

[0147] The following were prepared as base particles.

[0148] Base particle (S1): Divinylbenzene copolymer resin particles (Sekisui Chemical Co., Ltd. "Micropearl GS-L400", particle size 400 μm) Base particle (S2): Divinylbenzene copolymer resin particles (Sekisui Chemical Co., Ltd. "Micropearl SP-230", particle size 30 μm) Base particle (S3): Divinylbenzene copolymer resin particles (Sekisui Chemical Co., Ltd. "Micropearl GS-L600", particle size 600 μm) Base particle (S4): Divinylbenzene copolymer resin particles (Sekisui Chemical Co., Ltd. "Micropearl GS-L1000", particle size 1000 μm) Base particle (S5): Acrylic copolymer resin particles (Sekisui Chemical Co., Ltd. "Micropearl EZ4P-L400", particle size 400 μm) Base particle (S6): Divinylbenzene copolymer resin particles (Sekisui Chemical Co., Ltd. "Micropearl ELP-L400", particle size 400 μm)

[0149] (Example 1) Preparation of conductive particle 1: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S1). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 4.0 μm. Then, the outer surface of the copper-plated layer was electrolytically gold-plated to form a gold-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, a conductive particle 1 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a gold-plated layer was obtained as the conductive part.

[0150] (Example 2) Preparation of conductive particles 2: A base particle (S1) was electrolessly copper plated to form a copper plating layer with an average thickness of 0.3 μm on the surface of the base particle (S1). Then, electrolytic copper plating was performed until the average thickness of the entire copper plating layer reached 4.0 μm, forming a copper plating layer (first conductive part) with an average thickness of 4.0 μm. Next, electrolytic gold plating was performed on the outer surface of the copper plating layer to form a gold plating layer (second conductive part) with an average thickness of 0.5 μm. In this way, conductive particle 2 having a two-layer laminated structure of a copper plating layer and a gold plating layer was obtained as the conductive part.

[0151] (Example 3) Preparation of conductive particles 3: A base particle (S1) was electrolessly nickel-plated to form a nickel plating layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S1). Next, an electroplating solution containing copper and beryllium was used to electroplat the outer surface of the nickel plating layer to form a copper-beryllium alloy plating layer (copper:beryllium = 98% by weight:2% by weight) (second conductive part) with an average thickness of 4.0 μm. In this way, conductive particles 3 having a two-layer laminated structure of a nickel plating layer and a copper-beryllium alloy plating layer were obtained as the conductive part.

[0152] (Example 4) Preparation of conductive particles 4: A base particle (S1) was electrolessly nickel-plated to form a nickel plating layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S1). Next, an electroplating solution containing copper and zinc was used to electroplat the outer surface of the nickel plating layer to form a copper-zinc alloy plating layer (copper:zinc = 70% by weight:30% by weight) (second conductive part) with an average thickness of 4.0 μm. In this way, conductive particles 4 having a two-layer laminated structure of a nickel plating layer and a copper-zinc alloy plating layer were obtained as the conductive part.

[0153] (Example 5) Preparation of conductive particles 5: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S1). Next, an electroplating solution containing copper and tin was used to electroplat the outer surface of the nickel-plated layer to form a copper-tin alloy-plated layer (copper:tin = 98% by weight:2% by weight) (second conductive part) with an average thickness of 4.0 μm. In this way, conductive particles 5 having a two-layer laminated structure of a nickel-plated layer and a copper-tin alloy-plated layer were obtained as the conductive part.

[0154] (Example 6) Preparation of conductive particles 6: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S1). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 4.0 μm. Next, the outer surface of the copper-plated layer was electrolytically nickel-plated to form a nickel-plated layer (third conductive part) with an average thickness of 0.5 μm. Next, the outer surface of the nickel-plated layer was electrolytically gold-plated to form a gold-plated layer (fourth conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 6 having a four-layer laminated structure of nickel-plated layer, copper-plated layer, nickel-plated layer, and gold-plated layer as the conductive part were obtained.

[0155] (Example 7) Preparation of conductive particles 7: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S1). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 4.0 μm. Then, the outer surface of the copper-plated layer was electrolytically palladium-plated to form a palladium-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 7 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a palladium-plated layer were obtained as the conductive part.

[0156] (Example 8) Preparation of conductive particles 8: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S1). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 4.0 μm. Then, the outer surface of the copper-plated layer was electrolytically silver-plated to form a silver-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 8 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a silver-plated layer were obtained as the conductive part.

[0157] (Example 9) Fabrication of conductive particles 9: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S1). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 4.0 μm. Then, the outer surface of the copper-plated layer was electrolytically ruthenium-plated to form a ruthenium-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 9 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a ruthenium-plated layer as the conductive part were obtained.

[0158] (Example 10) Preparation of conductive particles 10: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S1). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 4.0 μm. Then, the outer surface of the copper-plated layer was electrolytically rhodium-plated to form a rhodium-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 10 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a rhodium-plated layer as the conductive part were obtained.

[0159] (Example 11) Preparation of conductive particles 11: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S1). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 4.0 μm. Then, the outer surface of the copper-plated layer was electrolytically iridium-plated to form an iridium-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 11 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and an iridium-plated layer as the conductive part were obtained.

[0160] (Example 12) Preparation of conductive particles 12: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S1). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 4.0 μm. Then, using an electrolytic plating solution containing gold and cobalt, the outer surface of the copper-plated layer was electrolytically gold-cobalt alloy-plated to form a gold-cobalt alloy-plated layer (gold:cobalt = 98% by weight:2% by weight) (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 12 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a gold-cobalt alloy-plated layer were obtained as the conductive part.

[0161] (Example 13) Preparation of conductive particles 13: Conductive particles 13 having a three-layer laminated structure of a nickel plating layer, a copper plating layer, and a gold plating layer were obtained in the same manner as in Example 1, except that nickel particles (average particle diameter: 400 nm) were adsorbed onto the base particle (S1) in advance as a protruding core material. The conductive particles 13 have multiple protrusions on the outer surface of the conductive portion.

[0162] (Example 14) Preparation of conductive particles 14: Conductive particles 14 having a three-layer laminated structure of a nickel plating layer, a copper plating layer, and a gold plating layer were obtained in the same manner as in Example 1, except that titanium oxide particles (average particle diameter: 400 nm) were adsorbed onto the base particle (S1) in advance as a protruding core material. The conductive particles 14 have multiple protrusions on the outer surface of the conductive portion.

[0163] (Example 15) Preparation of conductive particles 15: A base particle (S2) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.1 μm on the surface of the base particle (S2). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 0.6 μm. Then, the outer surface of the copper-plated layer was electrolytically gold-plated to form a gold-plated layer (third conductive part) with an average thickness of 0.03 μm. In this way, conductive particles 15 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a gold-plated layer were obtained as the conductive part.

[0164] (Example 16) Preparation of conductive particles 16: A base particle (S3) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S3). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 6.0 μm. Then, the outer surface of the copper-plated layer was electrolytically gold-plated to form a gold-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 16 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a gold-plated layer were obtained as the conductive part.

[0165] (Example 17) Preparation of conductive particles 17: A base particle (S4) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.5 μm on the surface of the base particle (S4). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 10.0 μm. Then, the outer surface of the copper-plated layer was electrolytically gold-plated to form a gold-plated layer (third conductive part) with an average thickness of 1.0 μm. In this way, conductive particles 17 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a gold-plated layer were obtained as the conductive part.

[0166] (Example 18) Preparation of conductive particles 18: A base particle (S2) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S2). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 5.0 μm. Then, the outer surface of the copper-plated layer was electrolytically gold-plated to form a gold-plated layer (third conductive part) with an average thickness of 0.03 μm. In this way, conductive particles 18 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a gold-plated layer were obtained as the conductive part.

[0167] (Example 19) Preparation of conductive particles 19: A base particle (S4) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.5 μm on the surface of the base particle (S4). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 2.5 μm. Then, the outer surface of the copper-plated layer was electrolytically gold-plated to form a gold-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 19 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a gold-plated layer were obtained as the conductive part.

[0168] (Example 20) Preparation of conductive particles 20: A base particle (S5) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S5). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 4.0 μm. Then, the outer surface of the copper-plated layer was electrolytically gold-plated to form a gold-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 20 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a gold-plated layer were obtained as the conductive part.

[0169] (Example 21) Preparation of conductive particles 21: A base particle (S6) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 0.3 μm on the surface of the base particle (S6). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 4.0 μm. Then, the outer surface of the copper-plated layer was electrolytically gold-plated to form a gold-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 21 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a gold-plated layer were obtained as the conductive part.

[0170] (Example 22) Preparation of conductive particles 22: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 2.3 μm on the surface of the base particle (S1). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 2.0 μm. Then, the outer surface of the copper-plated layer was electrolytically gold-plated to form a gold-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 22 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a gold-plated layer were obtained as the conductive part.

[0171] (Example 23) Preparation of conductive particles 23: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 2.8 μm on the surface of the base particle (S1). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 1.5 μm. Then, the outer surface of the copper-plated layer was electrolytically gold-plated to form a gold-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 23 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a gold-plated layer were obtained as the conductive part.

[0172] (Example 24) Preparation of conductive particles 24: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 3.3 μm on the surface of the base particle (S1). Next, the outer surface of the nickel-plated layer was electrolytically copper-plated to form a copper-plated layer (second conductive part) with an average thickness of 1.0 μm. Then, the outer surface of the copper-plated layer was electrolytically gold-plated to form a gold-plated layer (third conductive part) with an average thickness of 0.5 μm. In this way, conductive particles 24 having a three-layer laminated structure of a nickel-plated layer, a copper-plated layer, and a gold-plated layer were obtained as the conductive part.

[0173] (Comparative Example 1) Fabrication of conductive particles X1: A base particle (S1) was electrolessly nickel-plated to form a nickel-plated layer (first conductive part) with an average thickness of 5.0 μm on the surface of the base particle (S1). Next, the outer surface of the nickel-plated layer was electrolytically gold-plated to form a gold-plated layer (second conductive part) with an average thickness of 0.5 μm. In this way, a conductive particle X1 having a two-layer laminated structure of a nickel-plated layer and a gold-plated layer was obtained as the conductive part.

[0174] (evaluation) (1) Thickness of the conductive portion of the conductive particle The obtained conductive particles were added to Kulzer's "Technovit 4000" to a content of 30% by weight, dispersed, and used to create an embedded resin body for testing. An ion milling device (Hitachi High-Technologies Corporation's "IM4000") was used to cut a cross-section of the conductive particles dispersed in the embedded resin body, passing through the vicinity of the center of the particles.

[0175] Then, using a field emission transmission electron microscope (FE-TEM) (JEM-ARM200F, manufactured by JEOL Ltd.), the image magnification was set to 50,000x, and 10 conductive particles were randomly selected. The conductive portion of each conductive particle was then observed. The thickness of the conductive portion of each conductive particle was measured, and the arithmetic mean was taken to determine the thickness of the conductive portion.

[0176] (2) Particle size of conductive particles The particle size of the obtained conductive particles was calculated using a particle size distribution analyzer (Beckman Coulter's "Multisizer 4"). Specifically, the particle size was determined by measuring the particle size of approximately 100,000 conductive particles and calculating the average value.

[0177] Furthermore, from the obtained results, the ratio of the particle diameter of the conductive particles to the thickness of the conductive part (particle diameter of conductive particles / thickness of the conductive part) was calculated.

[0178] (3) Resistance of conductive particles For the obtained conductive particles, the resistance value (R1) of the conductive particles was measured after one loading and unloading cycle until the conductive particles were compressed and deformed by 20%, and the resistance value (R20) of the conductive particles was measured after 20 repetitions of loading and unloading until the conductive particles were compressed and deformed by 20%.

[0179] The above resistance values ​​(R1) and (R20) were measured as follows.

[0180] The following compression tests were performed using a micro-compression testing machine (ENT-NEXUS, manufactured by Elionix). Conductive particles were scattered on a substrate coated with Pt on a glass plate. A load was applied at 25°C using the smooth end face of a cylindrical indenter (500 μm in diameter, made of BeCu / Au on stainless steel) towards the center of the conductive particles until the particles were compressed and deformed by 20%, and then unloaded. This process constituted one cycle, and a total of 20 cycles of compression tests were performed. After the first cycle, when the substrate was compressed and deformed by 20%, the conductivity resistance was calculated from the voltage and current values ​​measured between the indenter and the substrate in the 20% compressed and deformed state, and this value was defined as the resistance (R1). After the 20th cycle, when the substrate was compressed and deformed by 20%, the conductivity resistance was similarly calculated in the 20% compressed and deformed state, and this value was defined as the resistance (R20).

[0181] From the obtained results, the ratio (R20 / R1) of the above resistance value (R20) to the above resistance value (R1) was calculated.

[0182] (4) Compression test of conductive particles For the obtained conductive particles, a compression test was conducted in which loading and unloading were repeated 20 times until the conductive particles were compressed and deformed by 20% or 30% (20% compression test or 30% compression test). The presence or absence of a bent portion was confirmed in the compression displacement-compression load curve.

[0183] The presence or absence of the above-mentioned bent section was confirmed as follows.

[0184] The following compression tests were performed using a micro-compression testing machine (Shimadzu Corporation's "Micro Autograph MST-I"). Conductive particles were scattered on a substrate coated with Pt on a glass plate. A load was applied at 25°C using the smooth end face of a cylindrical (500 μm diameter, diamond) indenter, in the direction of the conductive particles at a compression speed of 0.3 mN / sec, until the conductive particles were compressed and deformed by 20% or 30%. This process of unloading was considered one cycle, and a total of 20 cycles of compression tests were performed. The compressive displacement (μm) and compressive load (mN) during this period were measured, and the presence or absence of a bend was confirmed in the compressive displacement curve, which shows the relationship between compressive displacement (X axis) and compressive load (Y axis).

[0185] (5) Cracks in the conductive portion of conductive particles Twenty conductive particles were prepared after the compression test (20% compression test or 30% compression test) described in (4) above. The prepared conductive particles were observed using a scanning electron microscope (SEM) to check whether or not cracks had occurred in the conductive portion of the conductive particles. Cracks in the conductive portion of the conductive particles were determined under the following conditions.

[0186] [Criteria for determining cracks in the conductive portion of conductive particles] ○○○: No cracks have occurred in the conductive portion of the conductive particles. 〇〇: On the surface of the conductive part of the conductive particle, cracks with a length of less than 30% of the particle diameter are occurring along the surface of the conductive part. ○: Cracks with a length of 30% to less than 50% of the particle diameter occur along the surface of the conductive part of the conductive particle. ×: On the conductive surface of the conductive particle, a crack with a length of 50% or more of the particle diameter occurs along the surface of the conductive part.

[0187] (6) Connection failure in connection structure 1 Using the obtained conductive particles, a connecting structure (a connecting structure having the structure shown in Figure 4) was fabricated as follows.

[0188] A BGA board was prepared in which solder balls and metal pads (hereinafter referred to as LANDs) are electrically connected via through-holes. In this BGA board, conductive paste for via filling is placed inside the through-holes.

[0189] The BGA substrate was assembled into a package receiving unit equipped with a package fixing unit for securing the IC package. Next, solder paste was applied to the LAND on the upper surface of the BGA substrate using a dispenser. Conductive particles obtained using a ball mounter were placed on the applied solder paste. Then, it was heated in a reflow oven at 280°C for 3 minutes under a nitrogen atmosphere. In this way, an IC socket was obtained in which the LAND and the conductive particles were joined via solder, and the lower part of the BGA substrate assembled into the package receiving unit was joined to the electrical circuit board (motherboard) via solder.

[0190] To mount the IC package (CPU) into the obtained IC socket, the lever on the package fixing unit was pulled up to open the pressure cover, and the IC socket was set in the package receiving unit so that the LAND portion at the bottom of the IC package made contact with the conductive particles placed on the BGA substrate. With the pressure cover lowered, the lever was pushed down, causing the pressure cover to push the IC package down from above, applying a vertical load toward the contacts to the IC package, and thus creating a connection structure.

[0191] The obtained connection structures were observed using a scanning electron microscope (SEM) to check whether or not connection failures had occurred. Connection failure 1 was determined according to the following criteria.

[0192] [Criteria for determining connection failure 1] ○: No connection problems have occurred. ×: Connection problem occurred.

[0193] (7) Connection failure in connection structure 2 Two printed circuit boards (10mm x 10mm) were prepared as the first and second connection target components. Each printed circuit board had 121 through-electrodes formed on its surface at a 0.8mm pitch. Solder paste (M705-GRN360-K2-V, manufactured by Senju Metal Industries Co., Ltd.) was applied to the LAND of the first connection target component. The resulting conductive particles were placed on all the LANDs coated with solder paste, and the soldering oven was heated at 250°C for 30 seconds under a nitrogen atmosphere to mount the conductive particles onto the LANDs.

[0194] Next, using a ball mounter (CB-505, manufactured by Athlete FA Co., Ltd.), the LAND of the second connection target component was pressed against the conductive particles, applying a vertical load of 30g to one conductive particle and compressing and deforming it. After that, the pressure from the ball mounter was released, and after 1 minute, the conductive particles were compressed and deformed again using the ball mounter in the same manner to obtain the connection structure. This process constituted one cycle, and a total of 20 compression tests were performed. After 1 cycle and 20 cycles, the conductivity resistance of each electrode was measured using a resistance measuring device (RM3542A, manufactured by HIOKI E.E. CORPORATION), and the resistance value after 20 cycles (Q20) and the resistance value after 1 cycle (Q1) were measured. From the obtained results, the ratio (Q20 / Q1) of the above resistance value (Q20) to the above resistance value (Q1) was calculated for each electrode, the average was found, and it was evaluated according to the following criteria. Note that since the obtained connection structure has through electrodes formed, the resistance value can be measured even if one LAND is broken.

[0195] [Criteria for determining connection failure 2] ○○○: The average of the above ratio (Q20 / Q1) is 1.0 or more and less than 1.15, and there are no electrodes with the above ratio (Q20 / Q1) of 1.5 or more. ○○: The average of the above ratio (Q20 / Q1) is 1.15 or more and less than 1.3, and there are no electrodes with the above ratio (Q20 / Q1) of 1.5 or more. ○: The average of the above ratio (Q20 / Q1) is 1.3 or more and less than 1.5, and there are no electrodes with the above ratio (Q20 / Q1) of 1.5 or more. ×: At least one of the following conditions is met: "The average of the above ratio (Q20 / Q1) is 1.5 or higher" and "There are electrodes with the above ratio (Q20 / Q1) of 1.5 or higher."

[0196] The results are shown in Tables 1-4 below.

[0197] [Table 1]

[0198] [Table 2]

[0199] [Table 3]

[0200] [Table 4]

[0201] [Table 5] [Explanation of Symbols]

[0202] 1... Conductive particles 2...Base material particles 3...Conductive part 11... Conductive particles 11a...Protrusion 12...Conductive part 12a...Protrusion 13…core substance 21... Conductive particles 21a...Protrusion 22...Conductive part 22a...protrusion 22A...First conductive part 22Aa…Protrusion 22B...Second conductive part 22Ba...Protrusion 31…Insulating material 31a... Through hole 32... Solder paste section 33...Electrode 34... Solder ball 35…Metal terminal (metal pin) 51,101…Connection Structure 52...First connection target member 52a...First electrode 53...Second connection target member 53a...Second electrode 54,104…Connection part

Claims

1. A conductive particle comprising a base particle and a conductive portion disposed on the surface of the base particle, wherein the particle diameter of the conductive particle is 30 μm or more and 2000 μm or less. The conductive particle is used in place of a single metal terminal in a socket or connector.

2. The conductive particle according to claim 1, wherein the material of the conductive part includes a ductile metal.

3. The conductive portion has a laminated structure of two or more layers, The conductive particle according to claim 1 or 2, wherein the layer other than the outer surface of the conductive part comprises a layer containing a ductile metal.

4. The conductive particle according to claim 3, wherein the material of the outer surface of the conductive part is gold, silver, copper, tin, zinc, nickel, beryllium, cobalt, palladium, platinum, rhodium, ruthenium, iridium, or an alloy thereof.

5. The conductive particle according to claim 3 or 4, wherein the thickness of the layer containing the ductile metal is 0.6 μm or more.

6. The conductive particle according to any one of claims 1 to 4, wherein the thickness of the conductive portion is 0.3 μm or more and 20 μm or less.

7. The conductive particle according to any one of claims 1 to 6, wherein the thickness of the conductive portion is 0.6 μm or more and 20 μm or less.

8. The conductive particle according to any one of claims 1 to 7, wherein the ratio of the particle diameter of the conductive particle to the thickness of the conductive portion is 5 or more and 300 or less.

9. A conductive particle according to any one of claims 1 to 8, having a plurality of protrusions on the outer surface of the conductive portion.

10. The conductive particle according to any one of claims 1 to 9, wherein the load required to compress and deform the conductive particle by 20% is 50 N or less.

11. The conductive particle according to any one of claims 1 to 10, wherein the load required to compress and deform the conductive particle by 30% is 100 N or less.

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