WO2023149294A1

WO2023149294A1 - Conductive particles, method for manufacturing conductive particles, conductive material, and connection structure

Info

Publication number: WO2023149294A1
Application number: PCT/JP2023/002209
Authority: WO
Inventors: 厚喜久保; 良栗浦; みのり鈴木
Original assignee: 積水化学工業株式会社
Priority date: 2022-02-03
Filing date: 2023-01-25
Publication date: 2023-08-10

Abstract

Provided are conductive particles with which is it possible to make a crack in a conductive layer less likely to occur, and enhance the conduction reliability of an obtainable connection structure even when mounted at low pressure.　Conductive particle according to the present invention each have a base material particle, and a conductive layer having a crystal structure including grain boundaries, and having protrusions on the outer surface thereof. The conductive layer is disposed on the outer surface of the base material particle, and the grain boundaries in the conductive layer are oriented in the thickness direction of the conductive layer.

Description

Conductive particles, method for producing conductive particles, conductive material and connection structure

The present invention relates to conductive particles and methods for producing conductive particles. The present invention also relates to a conductive material and a connection structure using the conductive particles.

Anisotropic conductive materials such as anisotropic conductive paste and anisotropic conductive film are widely known. In the anisotropic conductive material, conductive particles are dispersed in a binder resin.

The anisotropic conductive material is used to electrically connect electrodes of various members to be connected, such as flexible printed circuit boards (FPC), glass substrates, glass epoxy substrates, and semiconductor chips, to obtain connection structures. ing. In recent years, as connection objects become more flexible, there is a demand for mounting at a lower pressure when manufacturing a connection structure in order to prevent damage to the connection objects.

With conventional conductive particles, the contact area between the conductive particles and the electrode is increased by deforming the particles themselves in order to increase the reliability of conduction. However, particularly in mounting at low pressure, it is difficult to sufficiently form a recess (indentation) on the surface of the electrode, the contact area between the conductive particles and the electrode becomes small, and the connection resistance of the resulting connection structure increases. There is

Also, in general, an oxide film is often formed on the surface of the electrodes connected by the conductive particles. If an oxide film is formed, the electrode and the conductive particles (conductive layer) cannot sufficiently contact each other, and the oxide film causes an increase in the connection resistance between the electrodes.

In order to lower the connection resistance of the resulting connection structure and improve the connection reliability, projections are sometimes formed on the outer surface of the conductive particles.

In Patent Document 1 below, conductive particles (conductive particles) comprising resin particles, composite particles having non-conductive inorganic particles arranged on the surface of the resin particles, and a metal layer covering the composite particles (conductive particles) are disclosed. disclosed. In the conductive particles, the metal layer has protrusions on the outer surface of the metal layer with the non-conductive inorganic particles serving as nuclei.

Further, in Patent Document 2 below, conductive electroless plated powder (conductive particles) in which relatively high projections are formed on the surface of spherical core particles (base particles) by self-decomposition of a plating solution is disclosed. In the conductive electroless plated powder, fine projections of 0.05 μm to 4 μm are formed on the surface of the nickel or nickel alloy film (conductive layer).

WO2017/138485A1 JP-A-2000-243132

However, in conductive particles having protrusions formed using a core substance (non-conductive inorganic particles) as described in Patent Document 1, grain boundaries are easily oriented along the boundary between the core substance and the conductive layer. Therefore, when the electrodes are electrically connected, the conductive layer is likely to crack. As a result, recesses (indentations) are not sufficiently formed on the surface of the electrode, and the connection reliability of the resulting connection structure may be lowered.

In addition, in the conductive particles having protrusions formed by decomposing the plating solution as described in Patent Document 2, voids are generated inside the protrusions due to a violent chemical reaction when the plating solution is decomposed. However, there is a problem that it tends to be brittle. As a result, the connection reliability of the resulting connection structure may be low.

An object of the present invention is to provide conductive particles that can make the conductive layer less likely to crack and that can improve the connection reliability of the resulting connection structure even when mounted at a low pressure, and the conductive particles. It is to provide a manufacturing method. Another object of the present invention is to provide a conductive material and a connection structure using the conductive particles.

According to a broad aspect of the present invention, a substrate particle and a conductive layer having a crystal structure including grain boundaries and having projections on the outer surface thereof are provided, and the conductive layer is formed on the outer surface of the substrate particle. Conductive particles are provided disposed thereon, wherein the grain boundaries in the conductive layer are oriented in the thickness direction of the conductive layer.

In a specific aspect of the conductive particles according to the present invention, the conductive particles do not have a core substance inside the protrusions.

In a specific aspect of the conductive particles according to the present invention, the grain boundaries existing in the portion of the conductive layer where the protrusions are located are one end located on the outer surface side of the conductive layer and one end located on the inner surface side of the conductive layer. and the other end of the grain boundary is located at the intersection of the straight line connecting the one end of the grain boundary and the center of the conductive grain and the inner surface of the conductive layer. The grain boundaries are oriented at an angle to the straight line so as to be located inside the protrusions.

In a specific aspect of the conductive particles according to the present invention, the outer surface area of the portion having the protrusions is 3% or more of 100% of the outer surface area of the conductive layer.

In a specific aspect of the conductive particles according to the present invention, the conductive particles have a compressive elastic modulus of 1000 N/mm ² or more and 30000 N/mm ² or less when compressed by 20% at 25°C.

In a specific aspect of the conductive particles according to the present invention, the conductive layer contains tin, nickel, copper, palladium, or gold.

In a specific aspect of the conductive particles according to the present invention, the conductive particles comprise an insulating material arranged on the outer surface of the conductive layer.

According to a broad aspect of the present invention, there is provided a method for producing the conductive particles described above, comprising the step of forming the conductive layer on the outer surface of the base particle, comprising: A method for producing conductive particles is provided, in which the protrusions are formed without arranging a core substance.

In a specific aspect of the method for producing conductive particles according to the present invention, the protrusions are formed without causing decomposition of the plating solution.

A broad aspect of the present invention provides a conductive material containing the above-described conductive particles and a binder resin.

According to a broad aspect of the present invention, a first member to be connected having a first electrode on its surface, a second member to be connected having a second electrode on its surface, the first member to be connected, a connecting portion connecting the second member to be connected, wherein the material of the connecting portion contains the above-described conductive particles, and the first electrode and the second electrode are connected to the conductive A connection structure is provided that is electrically connected by the physical particles.

A conductive particle according to the present invention comprises a base particle and a conductive layer having a crystal structure including grain boundaries and having projections on the outer surface. In the conductive particle according to the present invention, the conductive layer is arranged on the outer surface of the substrate particle. In the conductive particles according to the present invention, the grain boundaries in the conductive layer are oriented in the thickness direction of the conductive layer. Since the conductive particles according to the present invention have the above configuration, the conductive layer can be made difficult to crack, and the connection reliability of the connection structure obtained even when mounted at low pressure can increase

FIG. 1 is a cross-sectional view showing conductive particles according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing conductive particles according to a second embodiment of the present invention. FIG. 3 is a cross-sectional view showing conductive particles according to a third embodiment of the present invention. FIG. 4 is a schematic diagram for explaining the tilt angle θ of the grain boundary in the conductive layer. FIG. 5 is a cross-sectional view schematically showing a connected structure using conductive particles according to the first embodiment of the present invention. 6 is a transmission electron micrograph of a cross section of the conductive particles obtained in Example 1. FIG. 7 is a transmission electron micrograph of a cross section of the conductive particles obtained in Comparative Example 2. FIG. 8 is a transmission electron micrograph of a cross section of the conductive particles obtained in Comparative Example 3. FIG.

The details of the present invention will be described below.

(Conductive particles)
A conductive particle according to the present invention comprises a base particle and a conductive layer having a crystal structure including grain boundaries and having projections on the outer surface. In the conductive particle according to the present invention, the conductive layer is arranged on the outer surface of the substrate particle. In the conductive particles according to the present invention, the grain boundaries in the conductive layer are oriented in the thickness direction of the conductive layer.

As a result of extensive studies, the present inventors have found that by controlling the orientation of the grain boundaries in the conductive layer, it is possible to make the conductive layer less likely to crack, and the connection structure can be obtained even when mounted at a low pressure. It was found that the connection reliability of the body can be enhanced. In the conductive particle according to the present invention, the conductive layer has a crystal structure including grain boundaries, and the grain boundaries in the conductive layer are oriented in the thickness direction of the conductive layer, so cracks in the conductive layer are prevented. It can be made difficult to occur, and the connection reliability of the resulting connection structure can be improved even when mounted at a low pressure. In addition, in the conductive particles according to the present invention, the conductive layer has projections on the outer surface, so even when mounted at a low pressure, the projections can favorably form recesses (indentations) on the surface of the electrode, Oxide films can be effectively eliminated. As a result, the connection reliability of the resulting connection structure can be further enhanced.

The present inventors have found that the combination of the grain boundaries of the conductive layer having a specific orientation and the protrusions formed on the outer surface of the conductive layer can make cracks in the conductive layer significantly less likely to occur, and can be mounted at low pressure. It has been found that the connection reliability of the resulting connection structure can be remarkably improved even when the Furthermore, since the conductive particles according to the present invention have the above configuration, the gap controllability can be enhanced.

In addition, the present inventors have found that a combination of grain boundaries of a conductive layer having a specific orientation, protrusions formed on the outer surface of the conductive layer, and a configuration in which the conductive particles do not have a core substance inside the protrusions Furthermore, the inventors have found that cracking of the conductive layer can be made more difficult to occur, and the connection reliability of the resulting connection structure can be significantly improved even when mounted at a low pressure.

Specific embodiments of the present invention will be described below with reference to the drawings. In addition, in FIG. 1 and the figures described later, for convenience of illustration, the size and thickness of each component may differ from the actual size and thickness.

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

A conductive particle 1 shown in FIG. 1 includes a base particle 2 and a conductive layer 3 having a crystal structure including grain boundaries and having projections 3a on the outer surface. In the conductive particles 1, the conductive layer 3 has a crystal structure including grain boundaries. In the conductive particles 1, the conductive layer 3 has projections 3a on the outer surface. The conductive particles 1 have protrusions on their outer surfaces. In the conductive particle 1 , the conductive layer 3 is arranged on the outer surface of the substrate particle 2 and is in contact with the substrate particle 2 .

The conductive layer 3 covers the outer surface of the substrate particles 2 . The conductive particles 1 are coated particles in which the outer surface of the substrate particles 2 is coated with the conductive layer 3 . A conductive particle 1 has a conductive layer 3 on its surface.

The conductive particles 1 do not have a core substance inside the protrusions 3a. In the conductive particles 1, no core substance is arranged inside the protrusions 3a. In the conductive particles 1 , no core substance is arranged on the outer surface of the substrate particles 2 .

In the conductive particles, the conductive layer may cover the entire outer surface of the base particle, or the conductive layer may cover a part of the outer surface of the base particle.

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

A conductive particle 11 shown in FIG. 2 includes a base particle 2 and a conductive layer 13 having projections 13a on the outer surface. In conductive particles 11 , conductive layer 13 is arranged on the outer surface of substrate particles 2 . In the conductive particles 11, the conductive layer 13 is a two-layered conductive layer. In the conductive particle 11, the conductive layer 13 comprises a first conductive layer 13A and a second conductive layer 13B. In the conductive layer 13, the first conductive layer 13A is arranged outside the substrate particles 2, and the second conductive layer 13B is arranged outside the first conductive layer 13A. In the conductive layer 13, the first conductive layer 13A is laminated on the outer surface of the substrate particle 2, and the second conductive layer 13B is laminated on the outer surface of the first conductive layer 13A. .

In the conductive particles 11, the conductive layer 13 includes the first conductive layer 13A having a crystal structure including grain boundaries and protrusions 13Aa on the outer surface, and the first conductive layer 13A having no crystal structure including grain boundaries, and , and a second conductive layer 13B having protrusions 13Ba on its outer surface. In conductive particles 11, first conductive layer 13A has a crystal structure including grain boundaries. In conductive particles 11, second conductive layer 13B does not have a crystal structure including grain boundaries. In the conductive particles 11, the conductive layer 13 has projections 13a on the outer surface. The first conductive layer 13A has protrusions 13Aa on its outer surface. The second conductive layer 13B has protrusions 13Ba on its outer surface. When the first conductive layer has a crystal structure including grain boundaries and has protrusions on the outer surface, the second conductive layer may have a crystal structure including grain boundaries. Well, you don't have to. Further, when the second conductive layer has a crystal structure including grain boundaries and has projections on the outer surface, the first conductive layer does not have a crystal structure including grain boundaries. Alternatively, the outer surface may not have protrusions.

The conductive particles 11 do not have a core substance inside the projections 13a. The conductive particles 11 do not have a core material inside the projections 13Aa. The conductive particles 11 do not have a core substance inside the projections 13Ba. In the conductive particles 11, no core substance is arranged inside the projections 13a. In the conductive particles 11, no core substance is arranged inside the projections 13Aa. In the conductive particles 11, no core substance is arranged inside the projections 13Ba. In the conductive particles 11 , no core substance is arranged on the outer surface of the substrate particles 2 .

FIG. 3 is a cross-sectional view showing conductive particles according to a third embodiment of the present invention.

A conductive particle 21 shown in FIG. 3 includes a base particle 2 and a conductive layer 23 having a crystal structure including grain boundaries and having projections 23a on the outer surface. In the conductive particles 21, the conductive layer 23 has a crystal structure including grain boundaries. In the conductive particles 21, the conductive layer 23 has projections 23a on the outer surface. The conductive particles 21 have protrusions on their outer surfaces. In the conductive particles 21 , the conductive layer 23 is arranged on the outer surface of the substrate particles 2 and is in contact with the substrate particles 2 .

The conductive particles 21 comprise an insulating substance 24 arranged on the outer surface of the conductive layer 23 . At least part of the outer surface of the conductive layer 23 is covered with an insulating material 24 . The insulating substance 24 is made of an insulating material and is an insulating particle. Thus, the conductive particles may have an insulating material disposed on the outer surface of the conductive layer.

The conductive particles 21 do not have a core material inside the protrusions 23a. In the conductive particles 21, no core substance is arranged inside the protrusions 23a. In the conductive particles 21 , no core substance is arranged on the outer surface of the substrate particles 2 .

Other details of the conductive particles will be described below.

In this specification, "(meth)acrylate" indicates acrylate and methacrylate. "(Meth)acryl" indicates acryl and methacryl. "(Meth)acryloyl" indicates acryloyl and methacryloyl.

The particle diameter of the conductive particles is preferably 1.0 μm or more, more preferably 2.0 μm or more, and preferably 50 μm or less, more preferably 25 μm or less. When the particle diameter of the conductive particles is the lower limit or more and the upper limit or less, when the electrodes are connected using the conductive particles, the contact area between the conductive particles and the electrodes is sufficiently large, In addition, it becomes difficult to form agglomerated conductive particles when forming the conductive layer. Also, the distance between the electrodes connected via the conductive particle main body does not become too large, and the conductive layer is less likely to peel off from the surface of the base particle.

The particle size of the conductive particles is preferably the average particle size, and the average particle size indicates the number average particle size. The particle size of the conductive particles can be obtained, for example, by observing 50 arbitrary conductive particles with an electron microscope or an optical microscope and calculating the average particle size of each conductive particle, or by laser diffraction particle size distribution. Obtained by performing measurements.

From the viewpoint of enhancing reliability of conduction between electrodes, the coefficient of variation (CV value) of the particle size of the conductive particles is preferably 10% or less, more preferably 5% or less.

The coefficient of variation (CV value) can be measured as follows.

CV value (%) = (ρ/Dn) × 100
ρ: standard deviation of the particle size of the conductive particles Dn: average value of the particle size of the conductive particles

The shape of the conductive particles is not particularly limited. The shape of the conductive particles may be spherical, may be other than spherical, or may be flat.

The compression elastic modulus (20% K value) when the conductive particles are compressed by 20% at 25° C. is preferably 1000 N/mm ² or more, more preferably 3000 N/mm ² or more, and still more preferably 5000 N/mm ^{2 or} more. , preferably 30000 N/mm ² or less, more preferably 20000 N/mm ² or less. When the 20% K value of the conductive particles is equal to or more than the lower limit and equal to or less than the upper limit, damage to the member to be connected can be suppressed, and even when mounted at low pressure, the connection resistance is further effectively reduced. can do. Furthermore, when the conductive layer is formed on the surface, aggregation can be effectively suppressed, and cracking of the conductive layer can be made difficult to occur.

The compression elastic modulus (20% K value) of the conductive particles can be measured as follows.

Using a microcompression tester, a single conductive particle is compressed at 25°C, a compression rate of 0.3 mN/sec, and a maximum test load of 20 mN with a cylindrical (50 μm diameter, diamond) smooth indenter end face. do. The load value (N) and compression displacement (mm) at this time are measured. From the measured values obtained, the compression elastic modulus (20% K value) of the conductive particles can be obtained by the following formula. As the microcompression tester, for example, "Fischer Scope H-100" manufactured by Fisher Co., Ltd. is used. The compression modulus (20% K value) of the conductive particles is calculated by arithmetically averaging the compression modulus (20% K value) of 50 arbitrarily selected conductive particles. preferable.

20% K value (N/mm ² ) = (3/2 ^1/2 ) F S ^-3/2 R ^-1/2
F: load value (N) when the conductive particles are compressed and deformed by 20%
S: Compressive displacement (mm) when the conductive particles are compressed and deformed by 20%
R: radius of conductive particles (mm)

The compressive modulus described above universally and quantitatively represents the hardness of the conductive particles. By using the compressive modulus, the hardness of the conductive particles can be expressed quantitatively and uniquely.

<Base material particles>
Examples of the substrate particles include resin particles, inorganic particles other than metal particles, organic-inorganic hybrid particles, and metal particles. The substrate particles are preferably substrate particles other than metal particles, and more preferably resin particles, inorganic particles other than metal particles, or organic-inorganic hybrid particles. The substrate particles may be core-shell particles comprising a core and a shell arranged on the surface of the core. The core may be an organic core and the shell may be an inorganic shell.

Materials for the resin particles 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, and phenol formaldehyde. Resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, phenolic resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polyethylene terephthalate, polysulfone, polyphenylene oxide, polyacetal, polyimide, Examples include polyamideimide, polyetheretherketone, polyethersulfone, and divinylbenzene polymer. The divinylbenzene polymer may be a divinylbenzene copolymer. Examples of the divinylbenzene copolymer include a divinylbenzene-styrene copolymer and a divinylbenzene-(meth)acrylate copolymer. Since the hardness of the resin particles can be easily controlled within a suitable range, the material of the resin particles is a polymer obtained by polymerizing one or more polymerizable monomers having an ethylenically unsaturated group. is preferred.

When the resin particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, the polymerizable monomer having an ethylenically unsaturated group may be a non-crosslinking monomer. and crosslinkable monomers.

Examples of the non-crosslinkable monomers include styrene and styrene-based monomers such as α-methylstyrene; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; 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, cyclohexyl ( Alkyl (meth)acrylate compounds such as meth)acrylate and isobornyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate, etc. Oxygen atom-containing (meth)acrylate compounds; nitrile-containing monomers such as (meth)acrylonitrile; vinyl ether compounds such as methyl vinyl ether, ethyl vinyl ether, and propyl vinyl ether; vinyl acetate, vinyl butyrate, vinyl laurate, and vinyl stearate, etc. acid vinyl ester compounds of; unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene; halogens such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene A contained monomer etc. are mentioned.

Examples of the crosslinkable monomer include tetramethylolmethane tetra(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa (meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol poly(meth)acrylate, pentaerythritol tetra(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, (poly)ethylene glycol Polyfunctional (meth)acrylate compounds such as di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate ; triallyl (iso) cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, and γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, vinyltrimethoxysilane, etc. and silane-containing monomers. From the viewpoint of maintaining the shape of the flux-containing particles even at the glass transition temperature of the resin particles, the crosslinkable monomers include (poly)ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, penta Erythritol tetra(meth)acrylate or dipentaerythritol poly(meth)acrylate is preferred.

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

When the substrate particles are inorganic particles excluding metals or organic-inorganic hybrid particles, examples of inorganic substances for forming the substrate particles include silica, alumina, barium titanate, zirconia, and carbon black. Preferably, the inorganic substance is not a metal. The particles formed of silica can be obtained, for example, by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, followed by firing as necessary. particles that can be used. Examples of the organic-inorganic hybrid particles include organic-inorganic hybrid particles formed from a crosslinked alkoxysilyl polymer and an acrylic resin.

The organic-inorganic hybrid particles are preferably core-shell type organic-inorganic hybrid particles having a core and a shell disposed on the surface of the core. It is preferred that the core is an organic core. Preferably, the shell is an inorganic shell. From the viewpoint of effectively reducing the connection resistance between electrodes, the substrate particles are preferably organic-inorganic hybrid particles having an organic core and an inorganic shell disposed on the surface of the organic core.

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

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

When the substrate particles are metal particles, examples of metals that are materials of the metal particles include silver, copper, nickel, silicon, gold, and titanium.

The particle diameter of the substrate particles is preferably 0.5 μm or more, more preferably 1.5 μm or more, and preferably 49.95 μm or less, more preferably 39.95 μm or less. When the particle size of the substrate particles is equal to or more than the lower limit and equal to or less than the upper limit, small conductive particles can be obtained even when the distance between the electrodes is small and the thickness of the conductive layer is increased. Furthermore, when the conductive layer is formed on the outer surface of the substrate particles, it becomes difficult to aggregate, and the formation of aggregated conductive particles becomes difficult.

The shape of the substrate particles is not particularly limited. The shape of the substrate particles may be spherical, may be other than spherical, or may be flat.

The particle size of the substrate particles is preferably the average particle size, and the average particle size is preferably the number average particle size. The particle size of the substrate particles is determined using a particle size distribution analyzer or the like. The particle diameter of the substrate particles is preferably determined by observing 50 arbitrary substrate particles with an electron microscope or an optical microscope and calculating the average value. When measuring the particle size of the substrate particles of the conductive particles, it can be measured, for example, as follows.

"Technovit 4000" manufactured by Kulzer is added so that the content of the conductive particles is 30% by weight, and dispersed to prepare an embedded resin body for inspection containing the conductive particles. Using an ion milling device (“IM4000” manufactured by Hitachi High-Technologies Corporation), a cross section of the conductive particles is cut out so as to pass through the vicinity of the center of the base particles dispersed in the embedding resin body for inspection. Then, using a field emission scanning electron microscope (FE-SEM), set the image magnification to 25000 times, randomly select 50 conductive particles, and observe the base particles of each conductive particle. do. The particle diameter of the base material particles in each conductive particle is measured, and the arithmetic mean is taken as the particle size of the base material particles.

<Conductive layer>
The conductive particles have a crystal structure including grain boundaries and have a conductive layer (hereinafter sometimes referred to as “conductive layer X”) having projections on the outer surface. The conductive layer X is arranged on the outer surface of the substrate particles. In this specification, the term "grain boundary" indicates a boundary between crystal grains.

The grain boundaries and crystal structure of the conductive layer X can be observed by drawing a cross section of the conductive particles using, for example, a transmission electron microscope (TEM).

From the viewpoint of making it more difficult for the conductive layer to crack, the number of grain boundaries per 1 μm ² of the cross-sectional area in the thickness direction of the conductive layer X is preferably 2 or more, more preferably 8 or more, and even more preferably. is 20 or more, preferably 400 or less, more preferably 300 or less, still more preferably 200 or less.

In the conductive particles, the grain boundaries in the conductive layer X are oriented in the thickness direction of the conductive layer X. The grain boundary preferably includes both a grain boundary existing in a portion of the conductive layer X without the protrusion and a grain boundary existing in a portion of the conductive layer X having the protrusion.

The grain boundary existing in the portion of the conductive layer X where there is no protrusion has one end located on the outer surface side of the conductive layer X and the other end located on the inner surface side of the conductive layer X. From the viewpoint of making the cracking of the conductive layer more difficult to occur, the grain boundary existing in the portion of the conductive layer X without the protrusion is a line tangent to the outer surface of the conductive layer X at the one end of the grain boundary and the above It is preferred that the grain boundaries are orthogonal at the one end. From the viewpoint of making cracking of the conductive layer more difficult to occur, the grain boundary existing in the portion of the conductive layer X where there is no projection is tangent to the inner surface of the conductive layer X at the other end of the grain boundary, It is preferable that the grain boundaries are perpendicular to each other at the other end of the grain boundary. From the viewpoint of making the cracking of the conductive layer more difficult to occur, the grain boundary existing in the portion of the conductive layer X without the protrusion is a line tangent to the outer surface of the conductive layer X at the one end of the grain boundary and the above It is preferable that the one end of the grain boundary is orthogonal to the tangent to the inner surface of the conductive layer X at the other end of the grain boundary, and the other end of the grain boundary is orthogonal to the tangent to the inner surface of the conductive layer X. From the viewpoint of making cracks in the conductive layer more difficult to occur, it is preferable that the grain boundaries existing in the portion of the conductive layer X where the protrusions are absent are orthogonal to the outer surface and the inner surface of the conductive layer X. From the viewpoint of making the cracking of the conductive layer more difficult to occur, the grain boundary existing in the portion of the conductive layer X without the protrusion is the other end of the grain boundary and the center of the conductive particle (base material particle). It is preferable that it exists on an extension line of a straight line connecting . In addition, the grain boundary present in the portion of the conductive layer X where there is no projection is part of a straight line connecting the one end of the grain boundary and the center of the conductive particle (substrate particle). preferable.

From the viewpoint of making cracking of the conductive layer more difficult to occur, out of 100% of the number of grain boundaries existing in the portion of the conductive layer X without the protrusion, the grain boundaries perpendicular to the outer surface and the inner surface of the conductive layer X is preferably 30% or more, more preferably 50% or more, still more preferably 80% or more, and most preferably 100% (total amount). The upper limit of the number of grain boundaries perpendicular to the outer surface and the inner surface of the conductive layer X, out of 100% of the number of grain boundaries existing in the portion of the conductive layer X having no protrusion, is not particularly limited. Among 100% of the number of grain boundaries existing in the portion of the conductive layer X without the protrusion, the number of grain boundaries perpendicular to the outer surface and the inner surface of the conductive layer X may be 90% or less, or 80 % or less, or 50% or less.

In addition, the grain boundary existing in the portion of the conductive layer X where the protrusion is present has one end located on the outer surface side of the conductive layer X and the other end located on the inner surface side of the conductive layer X. From the viewpoint of making cracking of the conductive layer more difficult to occur, the grain boundary existing in the portion of the conductive layer X where the projection is located is perpendicular to the tangent line of the outer surface of the conductive layer X at the one end of the grain boundary. and not perpendicular to the tangent line of the inner surface of the conductive layer X at the other end of the grain boundary. From the viewpoint of making the cracking of the conductive layer more difficult to occur, the grain boundary existing in the portion of the conductive layer X where the projection is located is aligned with the straight line connecting the one end of the grain boundary and the center of the conductive particle. It is preferably oriented obliquely. From the viewpoint of making cracking of the conductive layer more difficult to occur, the other end of the grain boundary is a straight line connecting the one end of the grain boundary and the center of the conductive particle, and the inner surface of the conductive layer X. It is preferable that the grain boundary is oriented with an inclination with respect to the straight line so as to be located inside the protrusion from the intersection of the .

The boundary between the portion of the conductive layer X with the protrusion and the portion without the protrusion on the outer surface of the conductive layer X is the base of the protrusion. The base of the protrusion is the starting point of the bulge of the conductive layer X. As shown in FIG. The portion of the conductive layer X without the protrusion is the portion of the conductive layer X located outside the protrusion from the straight line connecting the base of the protrusion and the center of the conductive particle. The portion of the conductive layer X having the projections is the portion of the conductive layer X located inside the projections relative to the straight line connecting the base of the projections and the center of the conductive particles. The grain boundary existing in the portion of the conductive layer X with the protrusion includes a grain boundary having the boundary between the portion of the conductive layer X with the protrusion and the portion without the protrusion as the one end of the grain boundary. It is preferable that the one end of the grain boundary existing in the portion of the conductive layer X where the protrusion is present is located at the base of the protrusion. That is, the grain boundary existing in the portion of the conductive layer X where the protrusion is present includes a grain boundary having the base of the protrusion as one end of the grain boundary. From the viewpoint of making cracking of the conductive layer more difficult to occur, the grain boundary in the conductive layer X is the protrusion of the conductive layer X as a grain boundary existing in a portion of the conductive layer X having the protrusion. It is preferable to include a grain boundary having a boundary between the portion and the portion without the projection (the base of the projection) as the one end of the grain boundary. From the viewpoint of making cracking of the conductive layer more difficult to occur, the grain boundary existing in the portion of the conductive layer X having the protrusion is the boundary between the portion of the conductive layer X having the protrusion and the portion having no protrusion. It is preferable that the grain boundary is such that (the base of the protrusion) is the one end of the grain boundary.

FIG. 4 is a schematic diagram for explaining the inclination angle θ of grain boundaries in the conductive layer X. FIG. FIG. 4 shows part of the conductive particles 1 shown in FIG. In FIG. 4 , grain boundaries K and grain boundaries L in the conductive layer 3 (conductive layer X) are oriented in the thickness direction of the conductive layer 3 . The grain boundary K is a grain boundary existing in a portion of the conductive layer 3 where the protrusion 3a is not present. Grain boundaries K are perpendicular to the outer and inner surfaces of the conductive layer 3 . The grain boundary L is a grain boundary that exists in a portion of the conductive layer 3 where the protrusions 3a are present. The grain boundary L is a grain boundary whose one end is a boundary between a portion of the conductive layer 3 having the protrusion 3a and a portion having no protrusion 3a (the base of the protrusion). The grain boundaries L are oriented so as to be inclined with respect to a straight line (illustrated by a dotted line) connecting one end of the grain boundaries L and the center of the conductive grain. The other end of the grain boundary L is located inside the protrusion 3a from the intersection of the straight line (illustrated by the dotted line) connecting one end of the grain boundary L and the center of the conductive particle and the inner surface of the conductive layer 3. , the grain boundary L is oriented obliquely with respect to the straight line. In addition, in FIG. 4, the grain boundary is shown with a straight line for convenience of illustration.

When there is a grain boundary (grain boundary L) whose one end of the grain boundary is a boundary between a portion of the conductive layer with the protrusion and a portion without the protrusion (the base of the protrusion), the grain boundary and The angle formed by the one end of the grain boundary and the straight line connecting the center of the conductive particle (substrate particle) (shown by a dotted line in FIG. 4) is the inclination angle θ of the grain boundary in the conductive layer X. do.

From the viewpoint of making it more difficult for the conductive layer to crack, the inclination angle θ of the grain boundary (grain boundary L) with the base of the protrusion as the one end of the grain boundary is preferably 0° or more, more preferably 3. ° or more, more preferably 5° or more, preferably 90° or less, more preferably 60° or less, still more preferably 40° or less.

The inclination angle θ of the grain boundary (grain boundary L) with the base of the protrusion as the one end of the grain boundary is measured by observing the cross section of the conductive particles using, for example, a transmission electron microscope (TEM). can be done.

The conductive layer X preferably contains a metal. The metal forming the conductive layer X is not particularly limited. The above metals include tin, gold, silver, copper, tin, platinum, palladium, zinc, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, ruthenium, germanium, cadmium, and alloys thereof. is mentioned. Alternatively, tin-doped indium oxide (ITO) may be used as the metal. Only one of the above metals may be used, or two or more thereof may be used in combination.

From the viewpoint of enhancing conduction reliability, the conductive layer X preferably contains tin, nickel, copper, palladium, or gold, more preferably gold or nickel, and even more preferably nickel.

Within 100% of the outer surface area of the substrate particles, the area covered by the conductive layer X (coverage by the conductive layer X) is preferably 80% or more, more preferably 90% or more. The upper limit of the coverage by the conductive layer X is not particularly limited. The coverage of the conductive layer X may be 100%. When the coverage of the conductive layer X is equal to or higher than the lower limit, reliability of conduction can be effectively improved when the electrodes are electrically connected.

The thickness of the conductive layer X is preferably 50 nm or more, more preferably 100 nm or more, preferably 300 nm or less, more preferably 250 nm or less, still more preferably 200 nm or less. When the thickness of the conductive layer X is equal to or more than the lower limit and equal to or less than the upper limit, the conduction reliability is improved, and the conductive particles are not too hard, and the conductive particles are sufficiently attached when connecting the electrodes. It can be transformed.

The thickness of the conductive layer X can be measured, for example, by observing the cross section of the conductive particles using a transmission electron microscope (TEM).

The conductive layer may be a single conductive layer or multiple conductive layers. The conductive layer may include a plurality of conductive layers X, or may include the conductive layer X and a conductive layer other than the conductive layer X. The conductive particles may have a conductive layer other than the conductive layer X described above. The conductive particles (conductive layer) may have a conductive layer that does not have a crystal structure containing grain boundaries, may have a conductive layer that does not have protrusions on the outer surface, and contains grain boundaries. A conductive layer having no crystal structure and no projections on the outer surface may be provided. When the conductive particles (conductive layer) include a conductive layer other than the conductive layer X, the conductive layer other than the conductive layer X may be arranged on the inner surface side of the conductive layer X. It may be arranged on the outer surface side of the layer X. When a conductive layer other than the conductive layer X is arranged on the inner surface side of the conductive layer X, the coating rate of the conductive layer can be increased, and the connection reliability of the resulting connection structure can be further improved. can be significantly increased. When a conductive layer other than the conductive layer X is arranged on the outer surface side of the conductive layer X, the connection reliability of the resulting connection structure can be further enhanced. From the viewpoint of further improving the connection reliability of the resulting connection structure, when the conductive particles (conductive layer) include a conductive layer other than the conductive layer X, the conductive layer other than the conductive layer X It is preferably arranged on the outer surface of the conductive layer X.

From the viewpoint of further increasing the connection reliability of the resulting connection structure, the conductive layers other than the conductive layer X preferably contain palladium, nickel, gold, silver, copper, tin or ruthenium. More preferably, it contains gold, more preferably gold, and particularly preferably gold. Further, when the metal constituting the outer surface of the conductive layers other than the conductive layer X is gold, the corrosion resistance is further enhanced.

The thickness of the conductive layers other than the conductive layer X is preferably 1.0 nm or more, more preferably 5.0 nm or more, and preferably 100 nm or less, more preferably 80 nm or less, still more preferably 50 nm or less. When the thickness of the conductive layer other than the conductive layer X is the lower limit or more and the upper limit or less, the coating rate of the conductive layer can be increased, and when the electrodes are electrically connected, the conduction reliability is improved. can be significantly increased.

The conductive layer X has protrusions on its outer surface. It is preferable that the protrusion is plural. In general, an oxide film is often formed on the surface of the electrode that comes into contact with the conductive particles. Since the conductive layer X has projections on the outer surface, the oxide film can be effectively removed by the projections at the time of conductive connection. In addition, the protrusions can favorably form concave portions (indentations) on the surface of the electrode. Therefore, the electrode and the conductive layer are reliably brought into contact with each other, the contact area between the conductive particles and the electrode can be sufficiently increased, and the connection resistance can be effectively reduced. Furthermore, when the conductive particles are provided with an insulating substance on the surface, or when the conductive particles are dispersed in a binder and used as a conductive material, the protrusions of the conductive particles cause the gap between the conductive particles and the electrode. Insulating materials or binders can be effectively eliminated. Therefore, the contact area between the conductive particles and the electrode can be sufficiently increased, and the connection resistance can be effectively reduced.

From the viewpoint of exhibiting the effects of the present invention more effectively, it is preferable that the conductive particles do not have a core substance inside the protrusions. It is preferable that the conductive particles do not have a core substance outside the substrate particles. It is preferable that the conductive particles do not have a core substance on the outer surface of the substrate particles.

The average height of the plurality of projections is preferably 10 nm or more, more preferably 30 nm or more, preferably 900 nm or less, more preferably 200 nm or less, and even more preferably 100 nm or less. When the average height of the projections is equal to or higher than the lower limit and equal to or lower than the upper limit, the connection resistance between the electrodes can be effectively reduced. The average height of the protrusions can be calculated by the following method. Fifty conductive particles of the present invention are observed with an electron microscope or an optical microscope, and the heights of all protrusions on the peripheral edge of the observed conductive particles are measured. It is obtained by measuring the height of the protrusions with a surface on which no protrusions are formed as a reference surface, and calculating the average value.

From the viewpoint of further improving the connection reliability, the outer surface area of the portion where the protrusions are present (protrusion formation rate) in 100% of the surface area of the conductive layer X is preferably 3% or more, more preferably 10% or more, It is preferably 70% or less, more preferably 40% or less.

The external surface area (protrusion formation rate) of the portion having the projections in 100% of the external surface area of the conductive layer X is measured by the following method, regardless of whether the conductive particles are spherical or non-spherical. be able to. For 50 conductive particles, when viewed from the top using an electron microscope, the area of 100% of a circle with a diameter of 70% of the particle diameter of the conductive particles, the portion with protrusions inside the circle Measure the ratio (%) of the area and calculate the average value.

(insulating substance)
The conductive particles may comprise an insulating material disposed on the outer surface of the conductive layer. In this case, if the conductive particles are used to connect the electrodes, short-circuiting between adjacent electrodes can be prevented. Specifically, when a plurality of conductive particles are brought into contact with each other, an insulating material exists between the plurality of electrodes, so short-circuiting between laterally adjacent electrodes can be prevented instead of between the electrodes above and below. When the electrodes are connected, the insulating material between the conductive layer of the conductive particles and the electrodes can be easily eliminated by pressing the conductive particles with two electrodes. When the conductive particles have protrusions on the surface of the conductive layer, the insulating material between the conductive layer of the conductive particles and the electrode can be removed more easily. The insulating substance is preferably an insulating resin layer or insulating particles, more preferably insulating particles. The insulating particles are preferably insulating resin particles.

(Method for producing conductive particles)
The method for producing conductive particles according to the present invention is a method for producing the conductive particles described above. The method for producing conductive particles according to the present invention comprises the step of forming the conductive layer on the outer surface of the substrate particles. In the method for producing conductive particles according to the present invention, the protrusions are formed without arranging the core substance inside the protrusions. In the method for producing conductive particles according to the present invention, it is preferable to form the projections in a state where no core substance exists inside the projections.

In the method for producing conductive particles according to the present invention, since the above configuration is provided, it is possible to make it difficult for the conductive layer to crack, and even when mounting at a low pressure, the obtained connection structure Connection reliability can be improved.

In the conventional method for producing conductive particles, in order to improve the connection reliability of the resulting bonded structure, a core substance is attached to the outer surface of the base particle, and the conductive particles having the core substance inside the protrusions. may be produced. However, in such conductive particles, the grain boundaries tend to be oriented along the boundary between the core substance and the conductive layer, so cracks in the conductive layer tend to occur when the electrodes are electrically connected. As a result, the connection reliability of the resulting connection structure may be low.

In addition, in the manufacturing method of forming protrusions on the outer surface of the conductive layer by decomposing the plating solution, the strong chemical reaction when the plating solution decomposes creates voids inside the protrusions, which makes the protrusions prone to fragility. I have a problem. As a result, the connection reliability of the resulting connection structure may be low. Furthermore, when the protrusions are formed by decomposing the plating solution, the protrusions are likely to be laminated or connected, so it may be difficult to control the gap between the electrodes of the resulting connection structure. Therefore, in the method for producing conductive particles according to the present invention, it is preferable to form the protrusions without causing decomposition of the plating solution.

The method for forming the conductive layer X on the outer surface of the substrate particles includes a method by electroless plating, a method by electroplating, a method by physical collision, a method by mechanochemical reaction, physical vapor deposition or physical Examples include a method by adsorption, a method of coating the surface of the substrate particles with a metal powder or a paste containing a metal powder and a binder, and the like. The method of forming the conductive layer X is preferably electroless plating, electroplating or physical collision. Methods such as vacuum deposition, ion plating, and ion sputtering can be used as the method by physical vapor deposition. In addition, in the method using physical collision, for example, a sheeter composer (manufactured by Tokuju Kosakusho) or the like is used.

Examples of methods for forming projections on the outer surface of the conductive layer X include a method using electroless plating, a method using electroplating, and a method using physical vapor deposition or physical adsorption. From the viewpoint of exhibiting the effects of the present invention more effectively, it is preferable to form protrusions on the outer surface of the conductive layer X by a method using electroless plating.

Examples of methods for forming the conductive layer X such that the grain boundaries in the conductive layer X are oriented in the thickness direction of the conductive layer X include electroless plating and electroplating.

As a method for forming the conductive layer X (protrusions) so that the grain boundaries present in the portions of the conductive layer X where the protrusions are present satisfy the above-mentioned preferred aspects, the following methods may be mentioned. A method for adjusting the pH of an electroless plating solution. A method of adding an arbitrary chemical solution to the electroless plating solution. A method of adjusting the pH of an electroless plating solution and adding an arbitrary chemical solution to the electroless plating solution.

The electroless plating solution used for forming the conductive layer X and the protrusions preferably contains a metal salt. Examples of the metal salt include nickel sulfate, nickel chloride, nickel hydroxide, and nickel carbonate. From the viewpoint of improving the coverage with the conductive layer, the metal ion concentration of the electroless plating solution is preferably 0.1 mol/L or more, more preferably 0.3 mol/L or more, and still more preferably 0.5 mol/L. L or more, preferably 10.0 mol/L or less, more preferably 5.0 mol/L or less, still more preferably 2.0 mol/L or less.

The pH of the electroless plating solution is preferably 8.0 or higher, more preferably 9.0 or higher, and preferably 12.0 or lower, more preferably 11.0 or lower. When the pH of the electroless plating solution is equal to or higher than the lower limit, the conductive layer X (projection) is effectively controlled so that the grain boundary present in the portion of the conductive layer X where the projection is present satisfies the above-described preferred embodiment. can be formed When the pH of the electroless plating solution is equal to or lower than the upper limit, the productivity of the conductive particles can be enhanced.

The electroless plating solution may contain a complexing agent, a reducing agent, a dispersing agent, or the like.

The complexing agent is not particularly limited. Examples of the complexing agent include ammonia, trimethylamine, succinic acid, sodium citrate, boric acid, glycine, and the like. From the viewpoint of exhibiting the effects of the present invention more effectively, the complexing agent preferably contains sodium citrate, boric acid, or glycine.

The reducing agent is not particularly limited. Examples of the reducing agent include sodium borohydride, hydrazine, sodium hypophosphite, and dimethylamine borane. From the viewpoint of favorably forming the conductive layer and the protrusions, the reducing agent preferably contains sodium hypophosphite or dimethylamine borane.

The dispersant is not particularly limited. From the viewpoint of exhibiting the effects of the present invention more effectively, the dispersant is preferably a nonionic dispersant, more preferably polyethylene glycol. The weight average molecular weight of the dispersant is preferably 200 or more, more preferably 1,000 or more, and preferably 200,000 or less, more preferably 10,000 or less. The concentration of the dispersant in the electroless plating solution is preferably 0.01 g/L or more, more preferably 0.1 g/L or more, still more preferably 1.0 g/L or more, and preferably 100 g/L. Below, more preferably 50 g/L or less, still more preferably 10 g/L or less. When the molecular weight and concentration of the dispersing agent are at least the above lower limits, the productivity of the conductive particles can be enhanced. When the molecular weight and concentration of the dispersant are equal to or less than the above upper limits, the conductive layer X (protrusions) is effective so that the grain boundaries present in the portions of the conductive layer X where the protrusions are present satisfy the above-described preferred embodiments. can be formed The above weight average molecular weight indicates the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

(Conductive material)
The conductive material according to the present invention contains the conductive particles described above and a binder resin. The conductive particles are preferably used by being dispersed in a binder resin, and are preferably used to obtain a conductive material by being dispersed in the binder resin. The conductive material is preferably an anisotropic conductive material. The conductive material is preferably used for electrical connection between electrodes. The conductive material is preferably a circuit connecting material.

The binder resin is not particularly limited. Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers and elastomers. Only one type of the binder resin may be used, or two or more types may be used in combination.

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

In addition to the conductive particles and the binder resin, the conductive material includes, for example, a filler, an extender, a softener, a plasticizer, a polymerization catalyst, a curing catalyst, a coloring agent, an antioxidant, a heat stabilizer, and a light stabilizer. It may contain various additives such as agents, UV absorbers, lubricants, antistatic agents and flame retardants.

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

The content of the binder resin in 100% by weight of the conductive material is preferably 10% by weight or more, more preferably 30% by weight or more, still more preferably 50% by weight or more, particularly preferably 70% by weight or more, and preferably 99% by weight. .99% by weight or less, more preferably 99.9% by weight or less. When the content of the binder resin is the lower limit or more and the upper limit or less, the conductive particles are efficiently arranged between the electrodes, and the connection reliability of the connection target members connected by the conductive material can be further improved. can.

The content of the conductive particles in 100% by weight of the conductive material is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, preferably 40% by weight or less, and more preferably 20% by weight or less. , more preferably 10% by weight or less. When the content of the conductive particles is equal to or more than the lower limit and equal to or less than the upper limit, reliability of conduction between electrodes can be enhanced.

(connection structure)
A connection structure according to the present invention includes a first connection object member having a first electrode on the surface, a second connection object member having a second electrode on the surface, the first connection object member, and a connecting portion connecting the second connection target member. In the bonded structure according to the present invention, the material of the connecting portion contains the above-described conductive particles. In the connection structure according to the present invention, the first electrode and the second electrode are electrically connected by the conductive particles.

FIG. 5 is a cross-sectional view schematically showing a connection structure using conductive particles according to the first embodiment of the present invention.

A connection structure 51 shown in FIG. 5 includes a first connection target member 52, a second connection target member 53, and a connection portion that connects the first connection target member 52 and the second connection target member 53. 54. The connecting portion 54 is made of a conductive material containing the conductive particles 1 . The connecting portion 54 is preferably formed by curing a conductive material containing a plurality of conductive particles 1 . In addition, in FIG. 5, the conductive particles 1 are schematically shown for convenience of illustration. Instead of the conductive particles 1, conductive particles 11 or conductive particles 21 may be used.

The first connection object 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). A first electrode 52 a and a second electrode 53 a are electrically connected by one or more conductive particles 1 . Therefore, the first connection target member 52 and the second connection target member 53 are electrically connected by the conductive particles 1 .

The manufacturing method of the connection structure is not particularly limited. As an example of a method for manufacturing a connected structure, the conductive material is arranged between a first member to be connected and a second member to be connected to obtain a laminate, and then the laminate is heated and pressurized. methods (methods of crimping (thermocompression bonding)) and the like. The pressure of the compression bonding (thermocompression bonding) is preferably 5 MPa or more, more preferably 10 MPa or more, and preferably 90 MPa or less, more preferably 70 MPa or less. The heating temperature for the compression bonding (thermocompression bonding) is preferably 80° C. or higher, more preferably 100° C. or higher, and preferably 140° C. or lower, more preferably 120° C. or lower. When the pressure and heating temperature of the compression bonding (thermocompression bonding) are equal to or higher than the lower limit and equal to or lower than the upper limit, the connection reliability can be further enhanced. Moreover, by using the conductive particles according to the present invention, connection reliability can be sufficiently improved even when the pressure of the compression bonding is equal to or less than the upper limit. It is preferable that the conductive particles are used by pressing at a pressure equal to or lower than the upper limit, and preferably at a pressure equal to or higher than the lower limit and equal to or lower than the upper limit.

The first member to be connected and the second member to be connected are not particularly limited. Specifically, the first connection target member and the second connection target member include electronic components such as semiconductor chips, semiconductor packages, LED chips, LED packages, capacitors and diodes, as well as resin films, printed circuit boards, flexible Examples include electronic components such as circuit boards such as printed boards, flexible flat cables, rigid flexible boards, glass epoxy boards and glass boards. The first member to be connected and the second member to be connected are preferably electronic components. As connection target members become more flexible, there is a demand for mounting at a lower pressure when manufacturing a connection structure in order to prevent damage to the connection target members. Since the use of the conductive particles according to the present invention enables mounting at a lower pressure, the conductive particles are preferably used for conductive connection of a flexible printed circuit board. At least one of the first member to be connected and the second member to be connected is preferably a flexible printed circuit board.

Examples of the electrodes provided on the connection target 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. When the member to be connected is a flexible printed circuit board, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, a silver electrode or a copper electrode. When the member to be connected is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, a silver electrode, or a tungsten electrode. When the electrode is an aluminum electrode, it may be an electrode made of only aluminum, or an electrode 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 the trivalent metal elements include Sn, Al and Ga.

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

"I prepared the following materials."

Substrate particles:
Base particles A (divinylbenzene copolymer resin particles, manufactured by Sekisui Chemical Co., Ltd. "Micropearl SP-20375, particle size 3.75 μm)
Base particles B (divinylbenzene copolymer resin particles, manufactured by Sekisui Chemical Co., Ltd. "Micropearl EX-0015, particle size 1.5 μm)
Base material particles C (divinylbenzene copolymer resin particles, manufactured by Sekisui Chemical Co., Ltd. "Micropearl SP-230, particle size 30 μm)
Base particles D (organic-inorganic hybrid particles, particle diameter 3.75 μm)

(Example 1)
(1) Preparation of conductive particles After dispersing 10 parts by weight of base particles A in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution with an ultrasonic disperser, the solution is filtered to obtain base particles. I took out A. Next, the substrate particles A were added to 100 parts by weight of a 1% by weight solution of dimethylamine borane to activate the surfaces of the substrate particles A. After sufficiently washing the surface-activated substrate particles A with water, they were added to 500 parts by weight of distilled water and dispersed to obtain a suspension (1A).

In addition, nickel plating solution (2A) (pH 10 ) was prepared.

While stirring the suspension (1A) at 60°C, the nickel plating solution (2A) was gradually added dropwise to perform electroless pure nickel plating. After that, the mixture was stirred until the pH was stabilized, and after confirming that the bubbling of hydrogen stopped, a suspension (3A) after electroless nickel plating was obtained.

After that, by filtering the suspension (3A), the particles were taken out, washed with water, and dried to obtain conductive particles having a conductive layer (thickness of 150 nm) having projections on the outer surface. This conductive particle is a conductive particle that does not have a core substance inside the protrusions.

(2) Preparation of conductive material (anisotropic conductive paste) 7 parts by weight of the obtained conductive particles, 25 parts by weight of bisphenol A type phenoxy resin, 4 parts by weight of fluorene type epoxy resin, and 30 parts by weight of phenol novolac type epoxy resin A conductive material (anisotropic conductive paste) was obtained by blending parts by weight and SI-60L (manufactured by Sanshin Chemical Industry Co., Ltd.), followed by defoaming and stirring for 3 minutes.

(3) Fabrication of Connection Structure A printed circuit board was prepared on which an Au electrode pattern (first electrode, electrode: Ni/Au thin film on Cu) with L/S of 200 μm/200 μm was formed on the upper surface. Also, a flexible printed circuit board was prepared on the bottom surface of which an Au electrode pattern (second electrode, electrode: Ni/Au thin film on Cu) with L/S of 200 μm/200 μm was formed.

The obtained anisotropic conductive paste was applied onto the printed circuit board so as to have a thickness of 30 μm to form an anisotropic conductive paste layer. Next, the flexible printed circuit board was laminated on the anisotropic conductive paste layer so that the electrodes faced each other. After that, while adjusting the temperature of the head so that the temperature of the anisotropic conductive paste layer becomes 100 ° C., a pressure heating head is placed on the upper surface of the flexible printed circuit board, and a pressure of 40 MPa is applied to the anisotropic conductive paste. The layer was cured at 100° C. to obtain a connected structure.

(Example 2)
The outer surface of the conductive particles of Example 1 was plated with gold to form a second conductive layer (thickness: 30 nm) on the outer surface of the conductive layer (first conductive layer). A conductive material and a connection structure were obtained in the same manner as in Example 1, except that the obtained conductive particles were used.

(Example 3)
The outer surface of the conductive particles of Example 1 was plated with palladium to form a second conductive layer (thickness: 30 nm) on the outer surface of the conductive layer (first conductive layer). A conductive material and a connection structure were obtained in the same manner as in Example 1, except that the obtained conductive particles were used.

(Example 4)
Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that substrate particles A were changed to substrate particles B.

(Example 5)
Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that substrate particles A were changed to substrate particles C.

(Example 6)
Nickel plating solution (2A) containing nickel sulfate 150 g/L, sodium citrate 70 g/L, boric acid 30 g/L and dimethylamine borane 10 g/L, and polyethylene glycol (weight average molecular weight 1000) 0.1 g/L Conductive particles, a conductive material and a connection structure were obtained in the same manner as in Example 1, except that the nickel plating solution (pH 10) was used.

(Example 7)
Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that substrate particles A were changed to substrate particles D.

(Example 8)
Nickel plating solution (2A) containing nickel sulfate 150 g/L, sodium citrate 70 g/L, boric acid 30 g/L, sodium hypophosphite 30 g/L, and polyethylene glycol (weight average molecular weight 1000) 10 g/L Conductive particles, a conductive material and a connection structure were obtained in the same manner as in Example 1, except that the nickel plating solution (pH 10) was used.

(Example 9)
A first conductive layer-forming nickel plating solution (1B) containing 150 g/L of nickel sulfate, 70 g/L of sodium citrate, 30 g/L of boric acid, and 30 g/L of sodium hypophosphite was prepared. Furthermore, nickel for forming a second conductive layer containing 150 g/L of nickel sulfate, 70 g/L of sodium citrate, 30 g/L of boric acid, 10 g/L of dimethylamine borane, and 1 g/L of polyethylene glycol (weight average molecular weight: 1000) A plating solution (pH 10) (2B) was prepared. While stirring the suspension (1A) of Example 1 at 60° C., the first conductive layer-forming nickel plating solution (1B) was gradually added dropwise to perform electroless nickel plating. After that, the mixture was stirred until the pH was stabilized at 7.0, and after confirming that hydrogen bubbling had stopped, a first crystal structure containing no grain boundaries and no projections on the outer surface was obtained. A conductive particle having a conductive layer (thickness of 50 nm) and a suspension (3B) after electroless nickel plating containing the conductive particle were obtained. While stirring the suspension (3B) at 60° C., the nickel plating solution (2B) for forming the second conductive layer was gradually added dropwise to carry out electroless nickel plating to the outer surface of the first conductive layer. A conductive particle was obtained on which a second conductive layer (thickness: 150 nm) having a crystal structure including grain boundaries and projections on the outer surface was formed. A conductive material and a connection structure were obtained in the same manner as in Example 1, except that the obtained conductive particles were used.

(Example 10)
(1) Preparation of insulating particles After putting the following monomer composition into a 1000 mL separable flask equipped with a 4-neck separable cover, a stirring blade, a three-way cock, a cooling tube and a temperature probe, the following monomer composition Distilled water was added so that the solid content of 10% by weight, and the mixture was stirred at 200 rpm and polymerized at 60° C. for 24 hours under a nitrogen atmosphere. The above monomer composition contains 360 mmol of methyl methacrylate, 45 mmol of glycidyl methacrylate, 20 mmol of p-styryldiethylphosphine, 13 mmol of ethylene glycol dimethacrylate, 0.5 mmol of polyvinylpyrrolidone, and 2,2′-azobis{2-[N-(2 -Carboxyethyl)amidino]propane} 1 mmol. After completion of the reaction, the product was lyophilized to obtain insulating particles (particle diameter: 360 nm) having phosphorus atoms derived from p-styryldiethylphosphine on their surfaces.

(2) Production of conductive particles with insulating particles The insulating particles obtained in (1) above were dispersed in distilled water under ultrasonic irradiation to obtain a 10% by weight aqueous dispersion of insulating particles. 10 g of the conductive particles obtained in Example 8 were dispersed in 500 mL of distilled water, 1 g of a 10% by weight aqueous dispersion of insulating particles was added, and the mixture was stirred at room temperature for 8 hours. After filtration through a 3 μm mesh filter, the particles were further washed with methanol and dried to obtain conductive particles with insulating particles. A conductive material and a connection structure were obtained in the same manner as in Example 1, except that the obtained conductive particles with insulating particles were used.

(Comparative example 1)
Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that projections were not formed on the outer surface of the conductive layer.

(Comparative example 2)
To the suspension (1A) of Example 1, 1 part by weight of a metal nickel slurry (average particle size: 150 nm) was added over 3 minutes to obtain a particle mixed suspension ( 1C) was obtained. A nickel plating solution (pH 7.0) containing 150 g/L of nickel sulfate, 70 g/L of sodium citrate, 30 g/L of boric acid and 10 g/L of dimethylamine borane was prepared.

While stirring the suspension (1C) at 60°C, the nickel plating solution was gradually added dropwise to perform electroless pure nickel plating. After that, the mixture was stirred until the pH was stabilized at 7.0, and it was confirmed that the bubbling of hydrogen stopped to obtain a suspension (2C) after electroless pure nickel plating.

After that, by filtering the suspension (2C), the particles were taken out, washed with water, and dried to obtain conductive particles having a conductive layer (thickness of 150 nm) having projections on the outer surface. This conductive particle is a conductive particle having a core substance inside the protrusions.

(Comparative Example 3)
A nickel plating solution (1D) for forming a conductive layer containing 150 g/L of nickel sulfate, 30 g/L of sodium tartrate and 10 g/L of sodium hypophosphite, 150 g/L of nickel sulfate, 150 g/L of sodium hypophosphite and water A protrusion-forming plating solution (2D) containing 80 g/L of sodium oxide was prepared. While stirring the suspension (1A) of Example 1 at 60 ° C., the nickel plating solution for forming a conductive layer (1D) is gradually added dropwise to perform electroless nickel plating, and on the outer surface of the substrate particles A conductive layer (thickness: 150 nm) was formed on the substrate, and at the same time, self-decomposition of the nickel plating solution (1D) for forming a conductive layer was generated. Thereafter, the protrusion-forming plating solution (2D) was gradually dropped to form protrusions on the outer surface of the conductive layer. The mixture was stirred until the pH was stabilized, and after confirming that hydrogen bubbling had stopped, a suspension (3D) after electroless nickel plating was obtained. After that, by filtering the suspension (3D), the particles are taken out, washed with water, and dried to form a conductive layer (thickness 150 nm) having protrusions formed by decomposition of the plating solution on the outer surface. We obtained the chromogenic particles. A conductive material and a connection structure were obtained in the same manner as in Example 1, except that the obtained conductive particles were used.

(evaluation)
(1) Particle diameter of conductive particles, thickness of first conductive layer and second conductive layer, height of protrusion The thickness of the conductive layer of No. 2 and the height of the protrusions were measured by the method described above, and the average was calculated.

(2) Presence or absence of the conductive layer X and the inclination angle θ of the grain boundary with the base of the protrusion as one end of the grain boundary
The obtained conductive particles were observed with a transmission electron microscope (TEM) for the presence or absence of a conductive layer (conductive layer X) having a crystal structure containing grain boundaries and having protrusions on the outer surface. In addition, the tilt angles θ of three grain boundaries, one end of which is the base of the protrusion of the conductive layer X, were measured by the method described above, and the average was calculated. In Examples 2 and 3, the first conductive layer was a conductive layer (conductive layer X) having a crystal structure including grain boundaries and having projections on the outer surface. In Example 9, the second conductive layer was a conductive layer (conductive layer X) having a crystal structure including grain boundaries and having projections on the outer surface.

(3) Formation rate of projections The obtained conductive particles were subjected to the above-described method, and out of 100% of the external surface area of the conductive layer X (the first conductive layer for Comparative Examples 2 and 3), The surface area (protrusion formation rate) was determined.

(4) 20% K value The 20% K value of the conductive particles was measured at 25°C by the method described above using a microcompression tester (Fischer Scope H-100).

(5) Cracking of conductive layer In the obtained connection structure, using a transmission electron microscope (TEM), whether there is a crack in the conductive layer (first conductive layer and second conductive layer) of the conductive particles. evaluated whether or not Cracking of the conductive layer was determined according to the following criteria.

[Criteria for Cracking of Conductive Layer]
○○: The percentage of the number of conductive particles with cracks in the conductive layer is less than 30%. ○: The percentage of the number of conductive particles with cracks in the conductive layer is 30% or more and less than 60%. ×: Conductive layer The percentage of the number of conductive particles with cracks is 60% or more

(6) Connection Reliability The connection resistance between the upper and lower electrodes of the obtained 20 connection structures was measured by the 4-probe method. An average value of connection resistance was calculated. From the relationship of voltage=current×resistance, the connection resistance can be obtained by measuring the voltage when a constant current flows. Connection reliability was judged according to the following criteria.

[Connection Reliability Judgment Criteria]
○○: Average connection resistance is 2.0 Ω or less ○: Average connection resistance is over 2.0 Ω and 5.0 Ω or less △: Average connection resistance is over 5.0 Ω and 10.0 Ω or less ×: Connection The average value of resistance exceeds 10.0Ω

The results are shown in Tables 1 to 3 below.

Note that FIG. 6 is a transmission electron micrograph of the cross section of the conductive particles of Example 1. 7 is a transmission electron micrograph of a cross section of the conductive particles of Comparative Example 2. FIG. 8 is a transmission electron micrograph of a cross section of the conductive particles of Comparative Example 3. FIG. As shown in FIG. 6, in the conductive particles of Examples 1 to 10, the grain boundary in the conductive layer is oriented in the thickness direction of the conductive layer, and the other end of the grain boundary is electrically conductive with one end of the grain boundary. A grain boundary existing in a portion of the conductive layer where the projection is located is inclined with respect to the straight line so as to be located inside the projection from the intersection of the straight line connecting the center of the grain and the inner surface of the conductive layer. was oriented. As shown in FIG. 7, in the conductive particles of Comparative Example 2, the grain boundaries in the conductive layer were oriented along the boundary between the core substance and the conductive layer. As shown in FIG. 8, in the conductive particles of Comparative Example 3, the directions of the grain boundaries in the conductive layer were not uniform, and voids were generated inside the conductive layer and the protrusions.

DESCRIPTION OF SYMBOLS 1... Conductive particle 2... Base material particle 3... Conductive layer 3a... Protrusion 11... Conductive particle 13... Conductive layer 13A... First conductive layer 13B... Second conductive layer 13a, 13Aa, 13Ba... Protrusion 21... Conductivity Particle 23 Conductive layer 23a Projection 24 Insulating substance 51 Connection structure 52 First connection target member 52a First electrode 53 Second connection target member 53a Second electrode 54 Connection Department

Claims

substrate particles;
A conductive layer having a crystal structure including grain boundaries and having protrusions on the outer surface,
The conductive layer is disposed on the outer surface of the substrate particles,
The conductive particles, wherein the grain boundaries in the conductive layer are oriented in the thickness direction of the conductive layer.
The conductive particles according to claim 1, which do not have a core substance inside the protrusions.
a grain boundary existing in a portion of the conductive layer where the protrusion is located has one end located on the outer surface side of the conductive layer and the other end located on the inner surface side of the conductive layer;
The other end of the grain boundary is located inside the protrusion from the intersection of the straight line connecting the one end of the grain boundary and the center of the conductive particle and the inner surface of the conductive layer. 3. Conductive particles according to claim 1 or 2, wherein grain boundaries are oriented obliquely with respect to said straight line.
The conductive particles according to any one of claims 1 to 3, wherein the outer surface area of the portion having the protrusions is 3% or more in 100% of the outer surface area of the conductive layer.
The conductive particles according to any one of claims 1 to 4, which have a compression modulus of 1000 N/mm 2 or more and 30000 N/mm 2 or less when compressed by 20% at 25°C.
The conductive particles according to any one of claims 1 to 5, wherein the conductive layer contains tin, nickel, copper, palladium, or gold.
The conductive particles according to any one of claims 1 to 6, comprising an insulating substance arranged on the outer surface of the conductive layer.
A method for producing conductive particles according to any one of claims 1 to 7,
A step of forming the conductive layer on the outer surface of the base particle,
A method for producing conductive particles, wherein the protrusions are formed without arranging the core substance on the outer surface of the substrate particles.
The method for producing conductive particles according to claim 8, wherein the protrusions are formed without causing decomposition of the plating solution.
A conductive material comprising the conductive particles according to any one of claims 1 to 7 and a binder resin.
a first connection target member having a first electrode on its surface;
a second connection target member having a second electrode on its surface;
A connecting portion that connects the first connection target member and the second connection target member,
The material of the connection portion contains the conductive particles according to any one of claims 1 to 7,
A connection structure, wherein the first electrode and the second electrode are electrically connected by the conductive particles.