WO2024043047A1

WO2024043047A1 - Conductive particles, production method therefor, and conductive member

Info

Publication number: WO2024043047A1
Application number: PCT/JP2023/028688
Authority: WO
Inventors: 圭代大畑; 昭紘久持; 裕之稲葉
Original assignee: 日本化学工業株式会社
Priority date: 2022-08-25
Filing date: 2023-08-07
Publication date: 2024-02-29
Also published as: TW202411468A; JP2024030952A

Abstract

The present invention provides conductive particles which have a small connection resistance value and have excellent insulation performance, and with which short circuit is inhibited, and thus exhibit excellent connection reliability. The conductive particles each have a core material particle, and a conductive layer having a plurality of projection parts on the surface of the core material particle. The height variation of the projection parts is 0.01-0.25.

Description

Conductive particles, their manufacturing method and conductive materials

The present invention relates to conductive particles, a method for producing the same, and a conductive material containing the conductive particles.

Conductive particles used as conductive materials for anisotropic conductive materials such as anisotropic conductive films and anisotropic conductive pastes are generally conductive particles in which a conductive layer made of metal is formed on the surface of a core particle. It is being BACKGROUND OF THE INVENTION In connection with the miniaturization and refinement of electronic devices in recent years, electrical connections between electrodes and wiring are made using conductive layers of conductive particles to connect electrode terminals at minute pitches.

As the conductive layer of these conductive particles, a film created on the surface of the core particle by electroless plating with metal such as nickel is often used, and various techniques are used to achieve the desired characteristics. being done. As an example, Patent Document 1 describes that when the conductive particles are used for electrical connection between electrodes by forming a plurality of polygonal columnar protrusions on the conductive layer of the conductive particles, the conductive particles are It is stated that it can be efficiently placed on the electrode and that damage to the electrode caused by conductive particles can be suppressed. Furthermore, in Patent Document 2, by forming a plurality of protrusions in the shape of a polyhedron rather than a polygonal column in a conductive layer of conductive particles, even if the electrodes are connected at low voltage, the connection resistance can be efficiently lowered after connection. We have proposed conductive particles that can Further, Patent Document 3 discloses that when a conductive layer of conductive particles has a plurality of protrusions, and at least some of the plurality of protrusions are plate-shaped, the electrodes are connected. Conductive particles are described that do not flow excessively and can improve continuity reliability and insulation reliability.

Patent Documents 1 to 3 all attempt to solve the problem by designing the shape of the protrusion formed on the conductive layer in accordance with the desired effect. In this way, studies are being conducted to create conductive particles that have desired characteristics by varying the shape of the protrusions.

Japanese Patent Application Publication No. 2015-149277 Japanese Patent Application Publication No. 2016-119302 JP 2017-212033 Publication

By using conductive particles in which a conductive layer having protrusions is formed on the surface of the core particle, the contact efficiency between the conductive particles can be increased, and the amount of conductive particles can be reduced. Further, when an oxide film exists on the electrode surface, the oxide film is broken by the protrusions, thereby enabling conduction and suppressing electrical resistance.
It is said that by providing protrusions on the conductive layer in this manner, it is possible to lower the connection resistance and increase the reliability of conduction when connecting the electrodes.

However, with the demand for further miniaturization and refinement of electronic devices, there is a need to further reduce the connection resistance of the conventional conductive particles having protrusions, as well as to prevent short circuits at insulated parts.

Therefore, an object of the present invention is to provide conductive particles that have a small connection resistance value, excellent insulation properties, suppressed short circuits, and excellent connection reliability. Another object of the present invention is to provide a method for producing conductive particles that have a small connection resistance value, excellent insulation properties, suppressed short circuits, and excellent connection reliability.

In order to solve the above-mentioned problems, the present inventors conducted intensive studies on the protrusions of conductive particles, and found that the connection resistance of conductive particles in which the variation in the height of the protrusions was controlled within a certain range was small, and short circuits were suppressed. The present invention was completed based on this discovery.

That is, the present invention provides conductive particles having a core particle and a conductive layer having a plurality of protrusions on the surface of the core particle, and in which the variation in height of the protrusions is 0.01 or more and 0.25 or less. It provides:

Moreover, the present invention
a step of forming a conductive layer on the surface of the core material particles;
forming protrusions protruding from the surface of the conductive layer, and
The present invention provides a method for producing conductive particles, which includes a step of leveling the height of the protrusions.

According to the present invention, conductive particles are provided that have a small connection resistance value and excellent insulation properties, and therefore have excellent connection reliability with suppressed short circuits. Further, according to the present invention, there is provided a method for producing conductive particles that have a small connection resistance value and excellent insulation properties, and therefore have excellent connection reliability in which short circuits are suppressed.

FIG. 2 is a conceptual diagram of conductive particles having protrusions. 1 is a SEM photograph of conductive particles obtained in Example 1. 3 is a SEM photograph of conductive particles obtained in Example 3. 3 is a SEM photograph of conductive particles obtained in Example 4. 3 is a SEM photograph of conductive particles obtained in Comparative Example 2.

Hereinafter, the present invention will be explained based on its preferred embodiments. The conductive particle of the present invention (hereinafter also referred to as "the present conductive particle") has a core particle and a conductive layer having a plurality of protrusions on the surface of the core particle, and the conductive layer has a plurality of protrusions. The height variation is 0.01 or more and 0.25 or less.
If the height variation of the protrusions of the conductive particles is large, it is thought that the contact between the conductive particles and the electrode becomes uneven, and the connection resistance increases. Furthermore, if the height of the protrusion varies greatly, a short circuit may occur due to unexpected conduction.
In the present conductive particles, the variation in the height of the protrusions is controlled within a certain range, and as a result, it is thought that the connection resistance is small, short circuits are suppressed, and the connection reliability is improved.

The core material particles (hereinafter also referred to as "core material particles") included in the present conductive particles may be particulate, and the material may be inorganic or organic. Inorganic substances include metal particles such as gold, silver, copper, nickel, palladium, and solder, alloys of these metals, glass, ceramics, silica, metal or nonmetal oxides or their hydrates, and metal silicates such as aluminosilicates. Examples include salts, metal carbides, metal nitrides, metal carbonates, metal sulfates, metal phosphates, metal sulfides, metal acid salts, metal halides, and carbon.
On the other hand, examples of organic substances include natural fibers, natural resins, thermoplastic resins such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylic esters, polyacrylonitrile, polyacetals, ionomers, polyesters, and alkyd resins. , phenol resin, urea resin, benzoguanamine resin, melamine resin, xylene resin, silicone resin, epoxy resin, diallyl phthalate resin, and other thermosetting resins. These may be used alone or in combination of two or more.

The material of the present core material particles may be either one of the above-mentioned inorganic substances and organic substances, or may be both inorganic substances and organic substances. When the core material particle is composed of a material consisting of both an inorganic substance and an organic substance, the presence of the inorganic substance and the organic substance in the core material particle includes, for example, a core made of an inorganic substance and an organic substance covering the surface of the core. Examples include a core-shell type structure, such as an embodiment including a shell, or an embodiment including a core made of an organic substance and a shell made of an inorganic substance covering the surface of the core. In addition to these, examples include a structure in which inorganic substances and organic substances are mixed in one core particle, or a blend type structure in which they are randomly fused.

The present core material particles are preferably made of a material containing an organic substance, and more preferably made of a material containing both an inorganic substance and an organic substance. When the material is composed of both an inorganic substance and an organic substance, the inorganic substance is glass, ceramic, silica, metal or nonmetal oxide or its hydrate, metal silicate such as aluminosilicate, metal carbide, metal. Preference is given to nitrides, metal carbonates, metal sulfates, metal phosphates, metal sulfides, metal acid salts, metal halides and carbon. Further, the organic substance is preferably a natural fiber, a natural resin, a thermoplastic resin such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutene, polyamide, polyacrylic acid ester, polyacrylonitrile, polyacetal, ionomer, or polyester. By using a core material made of such a material, it is possible to improve the dispersion stability between particles, and also to develop appropriate elasticity and improve conduction when electrically connecting electronic circuits. .

When the core particles are made of a material containing an organic substance, the organic substance does not have a glass transition temperature or the organic substance has a glass transition temperature of over 100°C, so that the shape of the core particle is easily maintained. This is preferable because it is easy to maintain the shape of the core material particles in the process of forming the metal film. The glass transition temperature can be determined, for example, as the intersection of the original baseline and the tangent of the inflection point in the baseline-shifted portion of the DSC curve obtained by differential scanning calorimetry (hereinafter also referred to as "DSC").

When the organic substance is a highly crosslinked resin, almost no baseline shift may be observed even if the glass transition temperature is measured up to 200° C. using the above method. In this specification, such an organic substance is also referred to as an organic substance that does not have a glass transition temperature. For the present core material particles, an organic substance that does not have such a glass transition temperature may be used as the material of the core material particles. The organic substance that does not have a glass transition temperature can be copolymerized with a crosslinkable monomer and a monomer constituting the thermoplastic resin or thermosetting resin exemplified above. Examples of crosslinkable monomers include tetramethylene di(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, ethylene oxide di(meth)acrylate, and tetraethylene oxide. (meth)acrylate, 1,6-hexane di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, trimetherolpropane tri(meth)acrylate, tetramethylolmethane di( meth)acrylate, tetramethylolmethanetri(meth)acrylate, tetramethylolmethanetetra(meth)acrylate, tetramethylolpropanetetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol di(meth)acrylate, glycerol tridi( Polyfunctional (meth)acrylates such as meth)acrylates, polyfunctional vinyl monomers such as divinylbenzene and divinyltoluene, vinyltrimethoxysilane, trimethoxysilylstyrene, γ-(meth)acryloxypropyltrimethoxysilane, etc. Examples include silane-containing monomers, triallyl isocyanurate, diallyl phthalate, diallylacrylamide, diallyl ether, and other monomers. Particularly in the field of COG (Chip on Glass), such highly crosslinked resins are preferably used as materials for core particles because they are hard.

The shape of the core material particles may be amorphous, spherical, fibrous, hollow, plate-like, or acicular, but is usually spherical. The present core material particle may have a large number of protrusions on its surface. The shape of the core material particles is preferably spherical from the viewpoint of excellent filling properties and ease of coating metal.

The present conductive particles have a conductive layer on the surface of the present core particle, and the conductive layer has a plurality of protrusions.
The conductive layer of the present conductive particles is made of a conductive metal. Examples of metals constituting the conductive layer include gold, platinum, silver, copper, iron, zinc, nickel, tin, lead, antimony, bismuth, cobalt, indium, titanium, germanium, aluminum, chromium, palladium, tungsten, and molybdenum. , calcium, magnesium, rhodium, sodium, iridium, beryllium, ruthenium, potassium, cadmium, osmium, lithium, rubidium, gallium, thallium, tantalum, cesium, thorium, strontium, polonium, zirconium, barium, manganese, etc., or metals such as these. In addition to alloys, examples include metal compounds such as ITO and solder. Among them, gold, silver, copper, nickel, palladium, rhodium, and solder are preferred because they have low electrical resistance, and nickel, gold, palladium, nickel alloys, gold alloys, and palladium alloys are particularly preferred. One type of metal may be used, or a combination of two or more types may be used.

The conductive layer of the present conductive particles may have a single layer structure or a laminated structure consisting of multiple layers. In the case of a laminated structure consisting of multiple layers, the outermost layer preferably contains at least one member selected from the group consisting of nickel, gold, silver, copper, and palladium. Palladium and alloys thereof are preferred. In the case of alloys, nickel, gold, silver, copper, or alloys of palladium and phosphorus such as nickel alloys, gold alloys, silver alloys, copper alloys, and palladium alloys are preferred, and nickel-phosphorus alloys and palladium-phosphorus alloys are more preferred. The outermost layer of the conductive layer is more preferably an electroless nickel-phosphorus plating layer formed by an electroless method in the manufacturing method described below.

Furthermore, the conductive layer of the present conductive particles may cover the entire surface of the present core particle, or may cover only a portion thereof. When only a part of the surface of the present core particle is coated, the coated portion may be continuous, or may be discontinuously coated, for example, in the form of islands.

The thickness of the conductive layer of the present conductive particles is preferably 0.1 nm or more and 2,000 nm or less, and more preferably 1 nm or more and 1,500 nm or less, from the viewpoint of the electrical properties of the obtained conductive particles. Note that the height of the protrusions of the conductive layer is not included in the thickness of the conductive layer herein. The thickness of the conductive layer can be measured by cutting the particle to be measured into two and observing the cross section of the cut using a scanning electron microscope (SEM), and the thickness of the conductive layer is within the above range. It is preferable that it be within.

The protrusions (hereinafter also referred to as "main protrusions") possessed by the conductive layer of the present conductive particles have a variation in height of 0.01 or more and 0.25 or less. Note that the height variation is a value obtained by dividing the standard deviation of the heights of the protrusions by the average value of the heights of the protrusions, and is expressed by the following formula (1). The standard deviation of the height can be determined by the following formula (2), and the average height value is the arithmetic mean value of the heights of the projections determined by the following formula (3). When the value of this variation is within the above range, the contact between the conductive particles and the electrode becomes more uniform, leading to improved connection stability.

The variation in height of the main protrusion is more preferably 0.05 or more and 0.20 or less.
When the cross section of the conductive particle is observed with SEM, the height of the protrusion is determined from the highest point of the top of the protrusion to the point that hits the base of the protrusion toward the center of the conductive particle if the conductive particle is spherical. The shortest distance between By measuring all the heights of the protrusions of each conductive particle for 20 different conductive particles observed by SEM observation and substituting it into each of the above formulas, the variation in the height of the protrusions can be determined. . In addition, when a protrusion has a plurality of vertices, the highest apex is the height of the protrusion.

The average height of the projections of the conductive particles is preferably 20 nm or more and 1,000 nm or less, more preferably 50 nm or more and 800 nm or less. The number of projections per conductive particle is preferably 1 or more and 20,000 or less, more preferably 5 or more and 5,000 or less, although it depends on the particle size of the conductive particle.
Further, the length of the base of the protrusion is preferably 5 nm or more and 1,000 nm or less, more preferably 10 nm or more and 800 nm or less.

The average height of the protrusions is determined by calculating the heights of the protrusions in the same manner as described above, and using equation (3) above.
The average length of the base of the protrusion refers to the length along the surface 6 of the lower conductive layer at the portion where the protrusion is formed in FIGS. 1A and 1B. The length of the base of the protrusion is the arithmetic mean value of the lengths of all the bases of the protrusion of each conductive particle for 20 different conductive particles observed by SEM observation.

The shape of the top portion of the protrusion is preferably substantially planar from the viewpoint of more uniform contact between the conductive particles and the electrode. Here, the term "substantially planar" includes a complete plane and a surface having a curved surface having a radius of curvature, which will be described later. For example, in contrast to the completely flat part 5 shown in FIG. 1(a), the flat part 5 shown in FIG. included in the concept of

When the crown portion of the main protrusion is substantially planar, the length of the crown portion is preferably 10 nm or more and 500 nm or less, more preferably 20 nm or more and 400 nm or less. The length of the substantially planar top portion is the shortest distance connecting both ends of the substantially planar top portion in the cross section of the protrusion, as determined by SEM observation of the cross section of the conductive particle. For example, in FIGS. 1(a) and 1(b), the length of the straight line connecting the

ends

5a and 5b of the flat portion 5, in which the top of the head is substantially flat, is the length of the top of the head. The length of the top portion of the substantially planar main projection is determined by calculating the length of the top portion of the cross section of all the projections of each conductive particle for the cross sections of 20 different conductive particles observed by SEM observation. The arithmetic mean value of the measured values.

The number of protrusions depends on the particle size of the conductive particles, but from the viewpoint of the conductivity of the conductive particles, the number of protrusions per conductive particle is preferably 2 or more and 20,000 or less on average, More preferably, the number is 5 or more and 5,000 or less. Note that the number of protrusions is an arithmetic mean value of values measured for 20 different conductive particles observed by SEM observation.

When the top of the main protrusion is approximately planar, the radius of curvature of the top of the head is Ra, and the radius of curvature of the surface 6 of the lower layer of the conductive layer at the portion where the main protrusion is formed is Rb. It is preferable that the ratio of Ra (Ra/Rb) is 0.15 or more and 1.20 or less, particularly 0.20 or more and 1.00 or less. When the top portion of the protrusion has a radius of curvature that satisfies the above range, the contact between the conductive particles and the electrode becomes more uniform, leading to improved connection stability. Note that Ra can be the radius of a circumscribed circle that circumscribes the top portion of the cross section of each protrusion in a cross section of a conductive particle observed by SEM observation, for example. Rb can be, for example, the radius of a circumscribed circle circumscribing the surface of the lower layer of the conductive layer, that is, substantially the radius of the core material particle, for a cross section of the conductive particle observed by SEM observation.

If the height of the protrusion is within the above range, the contact between the conductive particles and the electrode is uniform, and the top of the protrusion is approximately flat, the presence of the conductive particles in the vicinity of the conductive particles. It is thought that contact with other conductive particles is suppressed, leading to prevention of short circuits. From this point of view, it is preferable that the total area of the substantially planar portions of the tops of the protrusions per conductive particle is large. That is, the ratio S2/S1 of the total area of the top portion of the projection, S2, to the projected area of one conductive particle, S1, is preferably 0.50 or more, particularly 0.55 or more. Note that S2/S1 is less than 1, preferably 0.95 or less, more preferably 0.90 or less, from the viewpoint of confirming that substantially planar protrusions are formed. The projected area of the conductive particles, S1, and the sum of the areas of the tops of the protrusions, S2, are measured by importing the SEM photographic image into an automatic image analysis device (Luzex (registered trademark) AP, manufactured by Nireco Co., Ltd.) be able to.

Further, the shape of at least one of the main protrusions is preferably an irregular shape from the viewpoint of preventing short circuits. The amorphous shape of the protrusion means that when the parietal portion of the protrusion is viewed from the side opposite to the base, the parietal portion is surrounded by a plurality of curved lines having different curvatures. When the top of the head of the projection is viewed from the side opposite to the base, the top of the head preferably has a shape other than circular or polygonal.
The number of irregularly shaped protrusions per one present conductive particle is more preferably 10 or more, and even more preferably 20 or more. Alternatively, the number of irregularly shaped protrusions is more preferably 90% or more, and even more preferably 95% or more, assuming that the total number of protrusions included in one conductive particle is 100%.

It is preferable that the protrusion is in a continuous body with the conductive layer formed on the surface of the core material particle. That is, it is preferable that the main protrusion is made of metal or an alloy like the conductive layer. A continuum here means that the conductive layer and the main protrusion are made of the same material, and there are no parts such as seams that impair the sense of unity between the conductive layer and the main protrusion. . Since the conductive layer and the main protrusion form a continuous body, the strength of the main protrusion is ensured, so that even if pressure is applied during use of the present conductive particles, the base of the main protrusion is less likely to be damaged.
More preferably, the protrusion is made of the same metal or alloy as the metal or alloy that constitutes the conductive layer formed on the surface of the core particle.

The average particle diameter of the conductive particles is preferably 0.1 μm or more and 50 μm or less, more preferably 1 μm or more and 30 μm or less. When the average particle diameter of the conductive particles is within the above range, conduction between the opposing electrodes can be more easily ensured without causing a short circuit in a direction different from that between the opposing electrodes. In the present invention, the average particle diameter of the conductive particles is an arithmetic mean value obtained by arbitrarily extracting 200 particles through SEM observation and measuring the particle diameter at a magnification of 10,000 times. When the conductive particles are spherical, the diameter of the conductive particles is the diameter of a circle obtained by projecting the conductive particles onto a plane, and does not include the height of the protrusion. When the conductive particles are not spherical, the particle diameter is the longest length of the line segments that intersect the image of the conductive particles projected onto a plane.

The shape of the present conductive particles is appropriately selected depending on the shape of the present core material particles. The shape of the present conductive particles may be the same as or different from the shape of the present core material particles, but from the viewpoint of manufacturing efficiency, it is preferable that both have the same shape. Examples of the shape of the conductive particles include spherical, fibrous, hollow, plate-like, acicular, and amorphous shapes. The shape of the conductive particles is preferably spherical from the viewpoint of excellent filling properties and connectivity.

The present conductive particles can be manufactured, for example, by a manufacturing method including the following steps (hereinafter also referred to as "this manufacturing method").
A step of forming a conductive layer on the surface of the core material particle A step of forming a protrusion protruding from the surface on the conductive layer A step of leveling the height of the protrusion

In the step of forming a conductive layer on the surface of the core material particles (hereinafter also referred to as "conductive layer forming step"), a dry method such as a vapor deposition method, a sputtering method, a mechanochemical method, a hybridization method, etc. is applied to the surface of the core material particles. A conductive layer is formed on the surface of the core particle by either a wet method using an electrolytic plating method, an electroless plating method, or the like. Further, a conductive layer may be formed on the surface of the core material particles by combining these methods.
The core material particles to be used may be the core material particles described above, and preferred materials and shapes are as described above.

In the conductive layer forming step, it is preferable to form a conductive layer on the surface of the core particle by an electroless plating method from the viewpoint that it is easy to obtain conductive particles having desired particle characteristics. However, it is more preferable from the viewpoints that it is easy to obtain conductive particles having desired particle characteristics and it is also easy to form protrusions described below. In particular, the conductive layer is preferably an electroless nickel alloy plating layer formed by an electroless method, and more preferably an electroless nickel-phosphorus plating layer.

The conductive layer forming process of forming a nickel-phosphorous alloy plating layer as a conductive layer will be described below.
When electroless plating is used in the conductive layer forming step, the surface of the core material particles preferably has the ability to trap noble metal ions, or is surface-modified so as to have the ability to trap noble metal ions. Preferably, the noble metal ion is a palladium or silver ion. Having the ability to capture noble metal ions means being able to capture noble metal ions in the form of a chelate or salt. For example, when an amino group, an imino group, an amide group, an imido group, a cyano group, a hydroxyl group, a nitrile group, a carboxyl group, etc. are present on the surface of the core material particle, the surface of the core material particle has the ability to trap noble metal ions. has. When the surface is modified to have the ability to trap noble metal ions, the method described in JP-A-61-64882, for example, can be used.

Core material particles having the ability to capture noble metal ions or whose surfaces have been modified so as to have the ability to capture noble metal ions are used as the core material particles, and the noble metal is supported on the surface of the core material particles. Specifically, the present core material particles are dispersed in a dilute acidic aqueous solution of a noble metal salt such as palladium chloride or silver nitrate. This causes the noble metal ions to be captured on the surface of the core material particles. The concentration of the noble metal salt is typically in the range of 1×10 ⁻⁷ to 1×10 ⁻² moles per m ² of surface area of the core particles. The core material particles in which precious metal ions have been captured are separated from the aqueous solution and washed with water. Subsequently, the core material particles are suspended in water, and a reducing agent is added thereto to perform a reduction treatment of noble metal ions. This causes the noble metal to be supported on the surface of the core material particles. As the reducing agent, for example, sodium hypophosphite, sodium borohydroxide, potassium borohydride, dimethylamine borane, hydrazine, formalin, etc. are used, and the reducing agent is selected from these based on the constituent material of the intended conductive layer. It is preferable that

Before capturing noble metal ions on the surface of the core particles, tin ions may be adsorbed on the surface of the particles and sensitization treatment may be performed for the purpose of increasing adhesion with the noble metal. In order to adsorb tin ions on the surface of the particles, for example, the surface-modified core particles as described above may be placed in an aqueous solution of stannous chloride and stirred for a predetermined period of time.

By subjecting the core particles pretreated in this manner to a conductive layer forming step, a conductive layer is formed on the surface of the core particles. After the conductive layer forming step, a step of forming protrusions protruding from the upper surface of the conductive layer (hereinafter also referred to as "protrusion forming step") is performed.

The protrusion forming step is preferably performed subsequent to the conductive layer forming step described below.
The conductive layer forming step is preferably an electroless nickel plating method in which an aqueous slurry of the core particles is mixed with an electroless nickel plating bath containing a dispersant, a nickel salt, a reducing agent, a complexing agent, and the like. In the conductive layer forming step using the electroless nickel plating method, self-decomposition of the plating solution occurs simultaneously with the formation of the conductive layer on the core particles. This self-decomposition occurs in the vicinity of the core material particles, so when the conductive layer is formed, the self-decomposed products are captured on the surface of the core material particles, producing nuclei of microprotrusions, and at the same time, the conductive layer is formed. Using the generated microprotrusion nucleus as a starting point, a protrusion grows in a protrusion forming step described below.

In the conductive layer forming step using the electroless nickel plating method, the core material particles are sufficiently dispersed in water preferably in a range of 0.1 to 500 g/L, more preferably 1 to 300 g/L to prepare an aqueous slurry. is preferable. The dispersion operation can be carried out using conventional stirring, high-speed stirring, or a shearing dispersion device such as a colloid mill or homogenizer. Further, ultrasonic waves may be used in combination with the dispersion operation. If necessary, a dispersant such as a surfactant may be added during the dispersion operation. Next, the aqueous slurry of the core material particles subjected to the dispersion operation is added to an electroless nickel plating solution containing a nickel salt, a reducing agent, a complexing agent, various additives, etc., and electroless plating is performed.

Examples of the above-mentioned dispersants include nonionic surfactants, zwitterionic surfactants, and/or water-soluble polymers.
As the nonionic surfactant, polyoxyalkylene ether surfactants such as polyethylene glycol, polyoxyethylene alkyl ether, and polyoxyethylene alkylphenyl ether can be used.
As the zwitterionic surfactant, betaine-based surfactants such as alkyldimethylacetic acid betaine, alkyldimethylcarboxymethylacetic acid betaine, and alkyldimethylaminoacetic acid betaine can be used.
As the water-soluble polymer, polyvinyl alcohol, polyvinylpyrrolidinone, hydroxyethylcellulose, etc. can be used.
These dispersants can be used alone or in combination of two or more. The amount of the dispersant to be used depends on its type, but is generally 0.5 to 30 g/L based on the volume of the electroless nickel plating solution. In particular, it is preferable that the amount of the dispersant used is in the range of 1 to 10 g/L based on the volume of the electroless nickel plating solution, from the viewpoint of further improving the adhesion of the conductive layer.

As the nickel salt, for example, nickel chloride, nickel sulfate, or nickel acetate is used, and the concentration thereof is preferably in the range of 0.1 to 50 g/L.
The reducing agent is used to reduce noble metal ions, and is selected based on the constituent material of the intended conductive layer. Examples of reducing agents include phosphorus compounds and boron compounds. When using, for example, sodium hypophosphite as the phosphorus compound, its concentration is preferably in the range of 0.1 to 50 g/L.

Examples of complexing agents include carboxylic acids or carboxylic acid salts such as citric acid, hydroxyacetic acid, tartaric acid, malic acid, lactic acid, gluconic acid or their alkali metal salts or ammonium salts, amino acids such as glycine, ethylene diamine, alkyl amines, etc. Compounds having a complexing effect on nickel ions are used, such as amino acid, other ammonium, EDTA or pyrophosphoric acid (salt). These can be used alone or in combination of two or more. Its concentration preferably ranges from 1 to 100 g/L, more preferably from 5 to 50 g/L.
The preferred pH of the electroless nickel plating solution at this stage is in the range of 3 to 14. The electroless nickel plating reaction begins immediately upon addition of the aqueous slurry of core particles and is accompanied by the generation of hydrogen gas. The conductive layer forming step ends when the generation of hydrogen gas is completely no longer observed.
The thickness of the conductive layer can be controlled by adjusting the concentration, pH, etc. of the nickel salt, dispersant, complexing agent, etc. if necessary, in the conductive layer forming step, and the preferred thickness range of the conductive layer is It can be done.

Next, after the conductive layer forming step, a protrusion forming step is performed. In the protrusion forming step, the protrusions are preferably formed by adding a nickel salt, a reducing agent, and an alkali to the electroless nickel plating solution used in the conductive layer forming step using the electroless nickel plating method.
The method of adding nickel salt, reducing agent and alkali is, for example,
(i) using a first aqueous solution containing one of a nickel salt, a reducing agent, and an alkali and a second aqueous solution containing the remaining two, or
(ii) using a first aqueous solution containing a nickel salt, a second aqueous solution containing a reducing agent, and a third aqueous solution containing an alkali;
is preferable.
Each aqueous solution (i) or (ii) is added to the electroless nickel plating solution at the same time, and the addition is continued to perform electroless nickel plating successively. When the addition of each aqueous solution is interrupted, the plating reaction stops, and when each solution is added, the plating reaction starts again. By adjusting the amount of each aqueous solution added, it is possible to control the thickness of the conductive layer formed to a desired thickness, and furthermore, it is possible to control the thickness of the conductive layer to be formed to a desired thickness. part is formed.
After the addition of the aqueous solution to the electroless nickel plating solution is completed and the generation of hydrogen gas is completely no longer observed, stirring is continued while maintaining the solution temperature for a while to complete the reaction.

In the case of (i) above, it is preferable to use a first aqueous solution containing a nickel salt and a second aqueous solution containing a reducing agent and an alkali, but the combination is not limited to this. In this case, the first aqueous solution does not contain a reducing agent or alkali, and the second aqueous solution does not contain a nickel salt. As the nickel salt and reducing agent, those mentioned above can be used. As the alkali, for example, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide can be used.

In the case of (ii) above, the first to third aqueous solutions each contain a nickel salt, a reducing agent, and an alkali, and each aqueous solution does not contain the other two components. The alkali used is the same as in the case (i) above.

In either case (i) or (ii) above, the concentration of nickel salt in the aqueous solution is preferably from 10 to 1,000 g/L, more preferably from 50 to 500 g/L.
When a phosphorus compound is used as the reducing agent, the concentration of the reducing agent is preferably 100 to 1,000 g/L, more preferably 100 to 800 g/L. When using a boron compound as a reducing agent, it is preferably from 5 to 200 g/L, more preferably from 10 to 100 g/L. When using hydrazine or a derivative thereof as a reducing agent, the amount is preferably from 5 to 200 g/L, more preferably from 10 to 100 g/L.
The concentration of alkali is preferably from 5 to 500 g/L, more preferably from 10 to 200 g/L.

The protrusion forming step may be performed continuously after the conductive layer forming step, or after the conductive layer forming step is completed, the core particles on which the conductive layer is formed are separated from the electroless nickel plating solution, and then the protrusions are formed. A forming step may also be performed. When separating the core material particles on which the conductive layer is formed from the electroless nickel plating solution, the core material particles on which the conductive layer is formed and the plating solution are separated by a method such as filtration after the conductive layer forming step is completed. Bye. After separation, the core material particles on which the conductive layer has been formed are newly dispersed in water to prepare an aqueous slurry, and a complexing agent is added thereto at a concentration of preferably 1 to 100 g/L, more preferably 5 to 50 g/L. An aqueous slurry is prepared by adding an aqueous solution in which the dispersant is preferably dissolved in a range of 0.5 to 30 g/L, more preferably 1 to 10 g/L. The aqueous solution described in (i) or (ii) above may be added to the prepared aqueous slurry to perform the protrusion forming step. In this way, a conductive layer having protrusions can be formed.

The conductive particles having protrusions formed in the protrusion forming step have their protrusions leveled in height in a step of leveling the protrusions (hereinafter also referred to as "leveling step"). The present conductive particles can be obtained by adjusting the height variation of the protrusions within the above range through the leveling step.
In the leveling process, the height of the protrusion formed in the protrusion forming process is reduced by polishing the top portion of the protrusion obtained in the protrusion forming process, thereby reducing the variation in the height of the protrusion. can be within a predetermined range.

Examples of methods for polishing the top portions of the protrusions include mixing media used in a ball mill, bead mill, etc. and conductive particles obtained in the protrusion forming process, and mixing an abrasive with conductive particles obtained in the protrusion forming process. A method of mixing the conductive particles obtained in the protrusion forming step, a method of mixing the conductive particles obtained in the protrusion forming step, a method of rotating the conductive particles obtained in the protrusion forming step on a flat surface such as a belt. etc.

When mixed media and conductive particles are mixed, the material of the mixed media is preferably a material that has a hardness comparable to or higher than that of the material of the protrusions of the conductive particles. Examples of the mixing method include a method using a stirrer with stirring blades, a method of mixing in a container that rotates or revolves or both, a method of mixing in a container that vibrates, and the like.
Examples of the material of the mixed media include zirconia, zircon, agate, alumina, iron, stainless steel, and glass.

When the abrasive and the conductive particles obtained in the protrusion forming step are mixed, examples of the abrasive include diamond, boron nitride, silicon carbide, aluminum oxide, and the like. The method for mixing with the abrasive may be the same as the method for mixing the mixed media and conductive particles.
The method for mixing the conductive particles may be the same as the method for mixing the mixed media and the conductive particles.

When the conductive particles obtained in the protrusion forming step are rotated on a flat surface such as a belt, the material of the flat surface is preferably a material having a hardness comparable to or higher than that of the material of the protrusions of the conductive particles. The conductive particles obtained in the protrusion forming step may be rotated and moved on the plane so that the conductive particles obtained in the protrusion forming step fall on the inclined plane. Alternatively, the conductive particles obtained in the protrusion forming step may be moved in the opposite direction on a plane that moves in a fixed direction.

For each of the polishing methods described above, the relationship between the polishing conditions and the height of the protrusions is measured in advance, and the polishing conditions are adjusted in advance so that the variation in the height of the protrusions is within the range of the present conductive particles. may be determined. Alternatively, while polishing, variations in the height of the protrusions may be measured over time, and based on the results, the polishing may be terminated when the variations in the height of the protrusions fall within the range of the present conductive particles. Similarly, the height of the protrusion can be set within the preferable range.

In the process of reducing the height of the protrusion in the leveling process, the protrusion can be made substantially planar by polishing the protrusion so that the protrusion has a flat top. In addition, by reducing the height of the protrusion in accordance with the curvature of the surface of the core material particle, the radius of curvature of the top portion of the protrusion, Ra, and the radius of curvature, Rb, of the outer surface of the conductive layer can be adjusted to the preferable value. It can be a relationship.

After the leveling step, this manufacturing method is further carried out under a vacuum of 1,000 Pa or less, preferably 0.01 Pa to 900 Pa, particularly preferably 0.1 Pa to 500 Pa, and 200°C to 600°C, preferably 250°C to 500°C. , particularly preferably at a temperature of 300°C to 450°C.
By heating the conductive particles while maintaining such a vacuum state, the metal in the conductive layer is unlikely to undergo side reactions even at high temperatures, and crystallization progresses, resulting in lower electrical resistance and improved electrical conductivity. Becomes excellent. Note that the degree of vacuum in the present invention is an absolute pressure, that is, a value when absolute vacuum is set to zero.

The heat treatment time in the heat treatment step is preferably 0.1 to 10 hours, more preferably 0.5 to 5 hours. By employing this processing time, it is possible to suppress an increase in manufacturing costs, and also to suppress deterioration of the core material particles and conductive layer due to thermal history, thereby reducing the influence on quality. Note that the heat treatment time is the time from when the target treatment temperature is reached until the heat treatment is completed.

The heat treatment step may be performed while the conductive particles are left standing, or may be performed while stirring. When heat treatment is performed with the conductive particles left still, it is preferable to leave the conductive particles still with a thickness of 0.1 mm to 100 mm. By allowing the conductive layer to stand still at this thickness, the conductive layer can be successfully heated, and manufacturing costs can be suppressed.

The heat treatment step is performed while the container containing the conductive particles is reduced to a vacuum, and then left standing or while being stirred. At this time, the gas phase of the container containing the conductive particles may be replaced with an inert gas such as nitrogen, and then the pressure may be reduced to vacuum, or the pressure may be reduced to vacuum as is. Further, the heat treatment may be performed multiple times if necessary.

The heat treatment step is performed for 5 to 60 minutes, more preferably for 10 to 50 minutes, after reaching a degree of vacuum of 1,000 Pa or less, preferably 0.01 to 900 Pa, particularly preferably 0.1 to 500 Pa, at room temperature. It is preferable to hold the temperature for 1 minute and then raise the temperature to the processing temperature. By this operation, it is possible to prevent the conductive layer from being oxidized by the heating atmosphere, oxygen, moisture, etc. in the conductive particles, and therefore the connection resistance can be made low.

After the heat treatment step, it is preferable to lower the temperature to 50° C. or lower, further to 40° C. or lower, while maintaining the degree of vacuum, and then release the vacuum. The reason for this is that if the vacuum is opened at a temperature immediately after the heat treatment, oxidation of the conductive layer will be promoted if oxygen or moisture is present in the atmosphere, which may increase the connection resistance. In addition, the vacuum may be opened in the normal atmosphere from the viewpoint of manufacturing cost, but from the viewpoint of preventing oxidation of the conductive layer, inert gas such as nitrogen, argon, helium, etc., or non-oxidizing gas such as hydrogen-nitrogen mixed gas may be used. It is more preferable to purge the toxic gas.

The present conductive particles can be suitably used as a conductive material such as a conductive filler in a conductive adhesive, as described below. The surface of the conductive material containing the present conductive particles and insulating resin (hereinafter also referred to as "the present conductive material") may be further coated with an insulating resin to prevent short circuits between the conductive particles. is preferred. The insulating resin coating is designed to prevent the surface of the conductive particles from being exposed as much as possible when no pressure is applied, and to prevent the coating from being destroyed by the heat and pressure applied when bonding two electrodes using a conductive adhesive. , the conductive particles are formed so that at least the protrusions on the surface thereof are exposed. The thickness of the insulating resin can be approximately 0.1 to 0.5 μm. The insulating resin may cover the entire surface of the conductive particles, or may cover only a part of the surface of the conductive particles.

Examples of the insulating resin include phenol resin, urea resin, melamine resin, allyl resin, furan resin, polyester resin, epoxy resin, silicone resin, polyamide-imide resin, polyimide resin, polyurethane resin, fluororesin, polyethylene, polypropylene, and polybutylene. Polyolefin resins such as polyalkyl (meth)acrylate resins, poly(meth)acrylic acid resins, polystyrene resins, acrylonitrile-styrene-butadiene resins, vinyl resins, polyamide resins, polycarbonate resins, polyacetal resins, ionomer resins, polyethersulfone resins , polyphenyl oxide resin, polysulfone resin, polyvinylidene fluoride resin, ethyl cellulose resin, and cellulose acetate resin.

Methods for coating the surface of conductive particles with an insulating resin to form an insulating coating layer include chemical methods such as coacervation method, interfacial polymerization method, in situ polymerization method, and liquid curing coating method, and spray drying method. , physico-mechanical methods such as air suspension coating method, vacuum evaporation coating method, dry blend method, hybridization method, electrostatic coalescence method, melt dispersion cooling method and inorganic encapsulation method, physical chemistry such as interfacial precipitation method. There are various methods.

The organic polymer constituting the insulating resin may contain a monomer component containing an ionic group in the polymer structure from the viewpoint of improving adhesion with conductive particles, provided that it is non-conductive. . The monomer component containing an ionic group may be either a crosslinkable monomer component or a non-crosslinkable monomer component. It is preferable that the organic polymer is formed using a monomer component in which at least one of the crosslinkable monomer component and the non-crosslinkable monomer component has an ionic group. Note that the term "monomer component" refers to a structure derived from a monomer in an organic polymer, and is a component derived from the monomer. By subjecting a monomer containing an ionic group to polymerization, an organic polymer containing the monomer component containing an ionic group as a constitutional unit is formed.

It is preferable that the ionic group exists in the organic polymer constituting the insulating resin. Further, it is preferable that the ionic group is chemically bonded to a monomer component constituting the organic polymer. The presence or absence of ionic groups at the interface of organic polymers can be determined by scanning electron microscopy when an insulating resin containing an organic polymer with ionic groups is formed on the surface of conductive particles. This can be determined by whether or not it is attached to the surface of the particle.

Examples of the ionic group include onium-based functional groups such as a phosphonium group, an ammonium group, and a sulfonium group. Among these, ammonium groups or phosphonium groups are preferable from the viewpoint of improving the adhesion between the conductive particles and the insulating resin and forming conductive particles that have both insulation properties and continuity reliability at a high level. More preferably, it is a phosphonium group.

Preferable examples of the onium-based functional group include those represented by the following general formula (1).

In the general formula (1), X is a phosphorus atom, a nitrogen atom, or a sulfur atom, and R may be the same or different, and R is a hydrogen atom, a linear, branched, or cyclic alkyl or aryl group. n is 1 when X is a nitrogen atom or a phosphorus atom, and is 0 when X is a sulfur atom. * is a bond.

Examples of counter ions for ionic groups include halide ions. Examples of halide ions include Cl ⁻ , F ⁻ , Br ⁻ , I ⁻ .

In the general formula (1), the linear alkyl group represented by R includes, for example, a linear alkyl group having 1 to 20 carbon atoms, and specifically, a methyl group, an ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, Examples include n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-icosyl group, and the like.

In the general formula (1), the branched alkyl group represented by R includes, for example, a branched alkyl group having 3 to 8 carbon atoms, and specifically, isopropyl group, isobutyl group, Examples include s-butyl group, t-butyl group, isopentyl group, s-pentyl group, t-pentyl group, isohexyl group, s-hexyl group, t-hexyl group, and ethylhexyl group.

In the general formula (1), the cyclic alkyl group represented by R includes cycloalkyl groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, and cyclooctadecyl group. Can be mentioned.

In the general formula (1), examples of the aryl group represented by R include a phenyl group, a benzyl group, a tolyl group, an o-xylyl group, and the like.

In the general formula (1), R is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, and an alkyl group having 1 to 8 carbon atoms. More preferably, it is a group. Further, in general formula (1), it is also more preferable that R is a linear alkyl group. By having such a structure of the onium-based functional group, it is possible to improve the adhesion between the insulating resin and the conductive particles to ensure insulation, and to further improve the reliability of conduction during thermocompression bonding.

In order to facilitate the acquisition of monomers and synthesis of polymers, as well as to increase the production efficiency of insulating resins, the organic polymers having ionic groups constituting the insulating resins are expressed by the following general formula (2) or general formula (3). It is preferable to have the structural unit shown below.

In general formula (2), X, R and n have the same meanings as in general formula (1) above. m is an integer from 0 to 5. An ⁻ represents a monovalent anion. When m is 0, it indicates that X is directly bonded to the benzene ring.

In general formula (3), X, R and n have the same meanings as in general formula (1) above. An ⁻ represents a monovalent anion. m ¹ is an integer of 1 or more and 5 or less. R ₅ is a hydrogen atom or a methyl group.

As an example of R in the general formula (2) and the general formula (3), the above description of the functional group of R in the general formula (1) can be applied as appropriate. The ionic group may be bonded to the CH group of the benzene ring of general formula (2) at any of the para, ortho, and meta positions, and is preferably bonded to the para position. In the general formulas (2) and (3), the monovalent An 2 ⁻ is preferably a halide ion. Examples of halide ions include Cl ⁻ , F ⁻ , Br ⁻ , I ⁻ .

In general formula (2), m is preferably an integer of 0 or more and 2 or less, more preferably 0 or 1, and particularly preferably 1. In general formula (3), m ¹ is preferably 1 or more and 3 or less, more preferably 1 or 2, and most preferably 2.

The organic polymer having an ionic group is preferably constituted by containing a monomer component having, for example, an onium-based functional group and an ethylenically unsaturated bond. From the viewpoint of facilitating monomer acquisition and polymer synthesis and increasing the manufacturing efficiency of the insulating resin, it is also preferable that the organic polymer having an ionic group contains a non-crosslinkable monomer component.

Examples of non-crosslinking monomers having an onium-based functional group and an ethylenically unsaturated bond include N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropylacrylamide, and N,N,N-trimethyl -N-2-Methacryloyloxyethylammonium chloride and other ammonium group-containing monomers; methacrylic acid phenyldimethylsulfonium methyl sulfate and other sulfonium group-containing monomers; 4-(vinylbenzyl)triethylphosphonium chloride, 4-(vinylbenzyl)trimethyl Phosphonium chloride, 4-(vinylbenzyl)tributylphosphonium chloride, 4-(vinylbenzyl)trioctylphosphonium chloride, 4-(vinylbenzyl)triphenylphosphonium chloride, 2-(methacroyloxyethyl)trimethylphosphonium chloride, 2-( Phosphonium groups such as methacroyloxyethyl)triethylphosphonium chloride, 2-(methacloyloxyethyl)tributylphosphonium chloride, 2-(methacloyloxyethyl)trioctylphosphonium chloride, 2-(methacloyloxyethyl)triphenylphosphonium chloride, etc. Examples include monomers having the following. The organic polymer having an ionic group may contain two or more types of non-crosslinkable monomer components.

The organic polymer constituting the insulating resin may have an ionic group bonded to all of the monomer components, or may have an ionic group bonded to a part of all the constituent units of the organic polymer. . When an ionic group is bonded to a part of the total structural units of the organic polymer, the proportion of the monomer component to which the ionic group is bonded is preferably 0.01 mol% or more and 99 mol% or less, and 0.01 mol% or more and 99 mol% or less. More preferably, it is .02 mol% or more and 95 mol% or less. Here, for the number of monomer components in the organic polymer, when the organic polymer has an ethylenically unsaturated bond, a structure derived from one ethylenically unsaturated bond is counted as a constituent unit of one monomer. When the ionic group is contained in both the crosslinkable monomer and the non-crosslinkable monomer, the proportion of the monomer components is the total amount thereof.

Examples of the form of the coating with the insulating resin include a form in which a plurality of insulating fine particles made of the insulating resin are arranged in a layered form, or a form in which the insulating resin forms a continuous film.

When the insulating resin is made of insulating fine particles, the conductive particles coated with the insulating fine particles are thermocompressed between the electrodes, and the insulating fine particles melt, deform, peel, or move on the surface of the conductive particles, causing heat to be generated. The metal surface of the conductive particles in the crimped portion is exposed, thereby enabling conduction between the electrodes and providing connectivity. On the other hand, in the surface portion of the conductive particles facing in a direction other than the thermocompression bonding direction, conduction in the direction other than the thermocompression bonding direction is prevented because the surface of the conductive particles is generally covered with the insulating fine particles.

Since the insulating fine particles contain the ionic group on their surface, they easily adhere to the conductive particles, and this allows a sufficient proportion of the surface of the conductive particles to be covered with the insulating fine particles. Peeling of the insulating fine particles from the particles is effectively prevented. Therefore, the short-circuit prevention effect of the insulating fine particles in a direction different from that between the opposing electrodes is likely to be exhibited, and an improvement in insulation in this direction can be expected.

The shape of the insulating fine particles is not particularly limited, and may be spherical or may have a shape other than spherical. Examples of shapes other than spherical include fibrous, hollow, plate-like, and needle-like. Further, the insulating fine particles may have many protrusions on their surfaces or may have an irregular shape. Spherical insulating fine particles are preferred from the viewpoint of adhesion to conductive particles and ease of synthesis.

The average particle diameter of the insulating fine particles is preferably 10 nm or more and 3,000 nm or less, more preferably 15 nm or more and 2,000 nm or less. When the average particle diameter of the insulating fine particles is within the above range, the resulting coated particles can easily ensure conduction between the opposing electrodes without causing a short circuit in a direction different from that between the opposing electrodes. The average particle diameter of the insulating fine particles is a value measured by observation using a scanning electron microscope, and specifically, it is measured by the method described in the Examples described below.

The particle size distribution of the insulating fine particles measured by the above method usually has a range. Generally, the width of the particle size distribution of powder is expressed by the coefficient of variation (hereinafter also referred to as "C.V.") shown by the following formula (4).
C. V. (%) = (standard deviation/average particle diameter) x 100...(4)
This C. V. The larger C. is, the wider the particle size distribution is. V. The smaller the particle size distribution, the sharper the particle size distribution. C. of the insulating fine particles used in this conductive material. V. is preferably 0.1% or more and 20% or less, more preferably 0.5% or more and 15% or less, particularly preferably 1% or more and 10% or less. C. V. By having the amount within this range, there is an advantage that the thickness of the coating layer made of the insulating fine particles can be made uniform.

Further, instead of the above-mentioned form in which the insulating fine particles are arranged in a layered manner, the insulating resin may be in a continuous film form. When the continuous film is an insulating resin having an ionic group, the surface of the conductive particles is exposed when the continuous film is melted, deformed, or peeled off by thermocompression bonding the conductive particles between the electrodes. It enables conduction between electrodes and provides connectivity. In particular, when the present conductive particles are bonded by thermocompression between electrodes, the continuous film is torn, and a large number of the present conductive particles have their surfaces exposed.
On the other hand, in the surface portion of the conductive particles facing in a direction different from the thermocompression bonding direction, the state of coverage of the conductive particles with the continuous film is generally maintained, so conduction in a direction other than the thermocompression bonding direction is prevented. When the insulating resin is a continuous film, a continuous film having ionic groups on the surface is preferable.

The thickness of the continuous film is preferably 10 nm or more in terms of improving insulation in a direction different from that between opposing electrodes, and 3,000 nm or less is preferable in terms of ease of conduction between opposing electrodes. It is preferable. From this point of view, the thickness of the continuous film is preferably 10 nm or more and 3,000 nm or less, more preferably 15 nm or more and 2,000 nm or less.

Similar to the insulating fine particles, it is preferable that the ionic group in the continuous film forms part of the chemical structure of the insulating resin as part of the insulating resin that constitutes the continuous film. In the continuous film, the ionic group is preferably contained in the structure of at least one constituent unit of the insulating resin constituting the continuous film. The ionic group is preferably chemically bonded to the insulating resin constituting the continuous film, and more preferably to a side chain of the insulating resin.

When the present conductive material has a continuous film of an insulating resin, the continuous film obtained by coating the present conductive particles with insulating fine particles having an ionic group on the surface and then heating the insulating fine particles, Alternatively, it is preferably a continuous film obtained by dissolving the insulating fine particles in an organic solvent. As mentioned above, the insulating fine particles having ionic groups tend to adhere closely to the present conductive particles, and as a result, the surface of the present conductive particles is covered with a sufficient proportion of the insulating fine particles, and the present conductive particles This makes it easier to prevent the insulating fine particles from peeling off from the conductive particles. Therefore, the continuous film obtained by heating or melting the insulating fine particles covering the present conductive particles can have a uniform thickness and a high coverage ratio on the surface of the conductive particles.

The present conductive particles may be treated with a surface treatment agent from the viewpoint of increasing affinity with the insulating resin and improving adhesion.
Examples of the surface treatment agent include benzotriazole compounds, titanium compounds, higher fatty acids or derivatives thereof, phosphoric esters, and phosphorous esters. These may be used alone or in combination as necessary.

The surface treatment agent may or may not be chemically bonded to the surface of the present conductive particles. The surface treatment agent only needs to be present on the surface of the present conductive particles, and in that case, it may be present on the entire surface of the present conductive particles or only on a part of the surface.

Examples of the triazole compounds include compounds having a nitrogen-containing heterocyclic structure having three nitrogen atoms in a five-membered ring.

Examples of triazole-based compounds include compounds having a triazole monocyclic structure that is not fused with other rings, as well as compounds having a ring structure in which a triazole ring and another ring are fused. Examples of other rings include a benzene ring and a naphthalene ring.

Among these, compounds having a ring structure in which a triazole ring and another ring are condensed are preferable because they have excellent adhesion with the insulating resin, and in particular, benzotriazole compounds, which are compounds having a structure in which a triazole ring and a benzene ring are condensed. is preferred.
Examples of benzotriazole compounds include those represented by the following general formula (4).

In the general formula (4), R ¹¹ is a negative charge, a hydrogen atom, an alkali metal, an optionally substituted alkyl group, an amino group, a formyl group, a hydroxyl group, an alkoxy group, a sulfonic acid group, or a silyl group. , R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ are each independently a hydrogen atom, a halogen atom, an optionally substituted alkyl group, a carboxyl group, a hydroxyl group or a nitro group.

Examples of the alkali metal represented by R ¹¹ in the general paper formula (4) include lithium, sodium, potassium, and the like. The alkali metal represented by R ¹¹ is an alkali metal cation, and when R ¹¹ in general formula (4) is an alkali metal, the bond between R ¹¹ and the nitrogen atom may be an ionic bond.
The alkyl group represented by R ¹¹ , R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ in general formula (4) includes those having 1 to 20 carbon atoms, and those having 1 to 12 carbon atoms are particularly preferable. The alkyl group may be substituted, and examples of the substituent include an amino group, an alkoxy group, a carboxyl group, a hydroxyl group, an aldehyde group, a nitro group, a sulfonic acid group, a quaternary ammonium group, a sulfonium group, a sulfonyl group, Examples include phosphonium groups, cyano groups, fluoroalkyl groups, mercapto groups, and halogen atoms.
The alkoxy group represented by R ¹¹ preferably has 1 to 12 carbon atoms.
Moreover, it is preferable that the carbon number of the alkoxy group as a substituent of the alkyl group represented by R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ is 1 to 12. Examples of the halogen atom represented by R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ in general formula (4) include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like.

Specific triazole compounds include 1,2,3-triazole, 1,2,4-triazole, 3-amino-1H-1,2,4-triazole, and 5-triazole compounds having a triazole monocyclic structure. -mercapto-1H-1,2,3-triazole sodium, 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, 3-amino-5-mercapto-1,2,4-triazole, In addition, benzotriazole, 1-methyl-1H-benzotriazole, 4-methyl-1H-benzotriazole, 5-methyl-1H-benzotriazole, 4-methyl-1H-benzotriazole, which has a ring structure in which a triazole ring and another ring are fused -Carboxy-1H-benzotriazole, 5-carboxy-1H-benzotriazole, 5-ethyl-1H-benzotriazole, 5-propyl-1H-benzotriazole, 5,6-dimethyl-1H-benzotriazole, 1-aminobenzo Triazole, 5-nitrobenzotriazole, 5-chlorobenzotriazole, 4,5,6,7-tetrabromobenzotriazole, 1-hydroxybenzotriazole, 1-(methoxymethyl)-1H-benzotriazole, 1H-benzotriazole- 1-methanol, 1H-benzotriazole-1-carboxaldehyde, 1-(chloromethyl)-1H-benzotriazole, 1-hydroxy-6-(trifluoromethyl)benzotriazole, benzotriazole butyl ester, 4-carboxyl-1H -benzotriazole butyl ester, 4-carboxyl-1H-benzotriazole octyl ester, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzo triazol-1-yl)methyl]imino]bisethanol, tetrabutylphosphonium benzotriazolate, 1H-benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate, 1H-benzotriazol-1-yloxy Tripyrrolidinophosphonium hexafluorophosphate, 1-(formamidomethyl)-1H-benzotriazole, 1-[bis(dimethylamino)methylene]-1H-benzotriazolium 3-oxide hexafluorophosphate, 1-[bis (dimethylamino)methylene]-1H-benzotriazolium 3-oxide tetrafluoroborate, (6-chloro-1H-benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate, O-(benzotriazole- 1-yl)-N,N,N',N'-bis(tetramethylene)uronium hexafluorophosphate, O-(6-chlorobenzotriazol-1-yl)-N,N,N',N' -Tetramethyluronium tetrafluoroborate, O-(6-chlorobenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate, O-(benzotriazole-1 -yl)-N,N,N',N'-bis(pentamethylene)uronium hexafluorophosphate, 1-(trimethylsilyl)-1H-benzotriazole, 1-[2-(trimethylsilyl)ethoxycarbonyloxy]benzo Triazole, 1-(trifluoromethanesulfonyl)-1H-benzotriazole, (trifluoroacetyl)benzotriazole, tris(1H-benzotriazol-1-yl)methane, 9-(1H-benzotriazol-1-ylmethyl)-9H -Carbazole, [(1H-benzotriazol-1-yl)methyl]triphenylphosphonium chloride, 1-(isocyanomethyl)-1H-benzotriazole, 1-[(9H-fluoren-9-ylmethoxy)carbonyloxy]benzo Examples include triazole, 1,2,3-benzotriazole sodium salt, naphthotriazole, and the like.

As the titanium-based compound, for example, a compound having a structure represented by the following general formula (5) can easily obtain affinity between the insulating resin and the conductive particles when it is present on the surface of the conductive particles. It is particularly preferred because it is easily dispersed in a solvent and the surface of the conductive particles can be uniformly treated.

In the general formula (5), R ²¹ is a divalent or trivalent group, and R ²² is an aliphatic hydrocarbon group having 2 to 30 carbon atoms, an aryl group having 6 to 22 carbon atoms, or a carbon It is an arylalkyl group having 7 or more atoms and 23 or less atoms, p and r are each an integer of 1 or more and 3 or less, satisfies p+r=4, q is an integer of 1 or 2, and R ²¹ is a divalent When R 21 is a group, q is 1; when R ²¹ is a trivalent group, q is 2. When q is 2, multiple R ^22s may be the same or different. * represents a bond.

Examples of the aliphatic hydrocarbon group having 4 to 28 carbon atoms represented by ^R22 include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group. , decyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, henicosyl group, docosyl group, and the like. Examples of unsaturated aliphatic hydrocarbon groups include alkenyl groups such as dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, nonadecenyl group, icosenyl group, eicosenyl group, henicosenyl group, and docosenyl group. It will be done.
Examples of the aryl group having 6 to 22 carbon atoms include phenyl group, tolyl group, naphthyl group, anthryl group, and the like.
Examples of the arylalkyl group having 7 or more and 23 or less carbon atoms include a benzyl group, a phenethyl group, a naphthylmethyl group, and the like.
As the hydrophobic group, a linear or branched aliphatic hydrocarbon group is particularly preferable, and a linear aliphatic hydrocarbon group is especially preferable.
From the viewpoint of increasing the affinity between the insulating resin and the conductive particles, the aliphatic hydrocarbon group as the hydrophobic group is particularly preferably one having 4 or more and 28 or less carbon atoms, and most preferably one having 6 or more and 24 or less carbon atoms. preferable.

Examples of the divalent group represented by R ²¹ include -O-, -COO-, -OCO-, -OSO ₂ -, and the like. Examples of the trivalent group represented by R ²¹ include -P(OH)(O-) ₂ and -OPO(OH)-OPO(O-) ₂ .

In the general formula (5), * is a bond, and the bond may be bonded to the metal film of the conductive particle or to another group or the like. Examples of other groups in this case include hydrocarbon groups, and specifically, alkyl groups having 1 to 12 carbon atoms.

As titanium-based compounds having the structure represented by the general formula (5), compounds having a structure in which R ²¹ in the general formula (5) is a divalent group are easy to obtain and have good conductive properties of conductive particles. It is preferable because it can be processed without damaging it. A structure in which R ²¹ is a divalent group in the general formula (5) is represented by the following general formula (6).

In the general formula (6), R ²¹ is a group selected from -O-, -COO-, -OCO-, -OSO ₂ -, and p, r and R ²² have the same meanings as in general formula (II). be.

In general formulas (5) and (6), r is preferably 2 or 3 from the viewpoint of improving the adhesion between the insulating resin and the conductive layer, and most preferably r is 3.

Specific examples of the titanate compounds used in the surface treatment include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, tetraisopropyl (dioctyl phosphite) titanate, and tetraisopropyl bis( dioctyl phosphite) titanate, tetraoctyl bis(ditridecyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl) bis(ditridecyl) phosphite titanate, bis(dioctyl pyrophosphate) oxyacetate titanate, bis (dioctyl pyrophosphate) ethylene titanate, etc., and these can be used alone or in combination of two or more.
Note that these titanate compounds are commercially available from Ajinomoto Fine Techno Co., Ltd., for example.

The higher fatty acids are preferably saturated or unsaturated straight-chain or branched mono- or polycarboxylic acids, more preferably saturated or unsaturated straight-chain or branched monocarboxylic acids, and saturated or unsaturated straight-chain or branched monocarboxylic acids. More preferred are chain monocarboxylic acids. The fatty acid preferably has 7 or more carbon atoms. Further, the term "derivative" refers to a salt or amide of the fatty acid.

The higher fatty acid or its derivative used for the surface treatment preferably has 7 to 23 carbon atoms, more preferably 10 to 20 carbon atoms. Such higher fatty acids or their derivatives include, for example, saturated fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, and stearic acid; unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid, and arachidonic acid; Examples include metal salts or amides of. Metal salts of higher fatty acids include alkali metals, alkaline earth metals, transition metals such as Zr, Cr, Mn, Fe, Co, Ni, Cu, Ag, and other metals other than transition metals such as Al and Zn. Examples include salts, preferably polyvalent metal salts such as Al, Zn, W, and V. Higher fatty acid metal salts may be mono-, di-, tri-, tetra-, etc. depending on the valence of the metal. The higher fatty acid metal salt may be any combination thereof.

As the phosphoric acid ester and the phosphorous acid ester, those having an alkyl group having 6 to 22 carbon atoms are preferably used.
Examples of phosphoric esters include hexyl phosphate, heptyl phosphate, monooctyl phosphate, monononyl ester, monodecyl phosphate, monoundecyl phosphate, monododecyl phosphate, and phosphoric acid. Examples include acid monotridecyl ester, phosphoric acid monotradecyl ester, phosphoric acid monopentadecyl ester, and the like.
Examples of the phosphite include phosphite hexyl ester, phosphite heptyl ester, phosphite monooctyl ester, phosphite monononyl ester, phosphite monodecyl ester, phosphite monoundecyl ester, Examples include phosphorous acid monododecyl ester, phosphorous acid monotridecyl ester, phosphorous acid monotradecyl ester, phosphorous acid monopentadecyl ester, and the like.

The surface treatment agent used in the surface treatment is preferably a triazole compound or a titanium compound, especially benzotriazole or 4-carboxylic compound, from the viewpoint of having excellent affinity with the insulating resin and increasing the coverage of the insulating resin. Particularly preferred are benzotriazole, isopropyl triisostearoyl titanate, and tetraisopropyl (dioctyl phosphite) titanate.

The method of treating the present conductive particles with a surface treatment agent is obtained by dispersing the present conductive particles in a solution of the surface treatment agent and then filtering the solution. Before being treated with a surface treatment agent, the conductive particles may be treated with another treatment agent or may be untreated.
The concentration of the surface treatment agent in the solution of the surface treatment agent in which the present conductive particles are dispersed is, for example, 0.01% by mass or more and 10.0% by mass or less. The solvent for the solution of the surface treatment agent is water, alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, isopentyl alcohol, cyclohexanol, acetone, methyl Ketones such as isobutyl ketone, methyl ethyl ketone, methyl-n-butyl ketone, esters such as methyl acetate, ethyl acetate, ethers such as diethyl ether, ethylene glycol monoethyl ether, normal hexane, cyclohexanone, toluene, 1,4 -dioxane, N,N-dimethylformamide, tetrahydrofuran and the like. It is preferable that the surface-treated conductive particles that have been dispersed and filtered are dispersed again in a solvent to remove excess surface treatment agent.

The surface treatment of the present conductive particles with a surface treatment agent can be carried out by mixing the present conductive particles, the surface treatment agent, and a solvent at room temperature. Alternatively, the conductive particles and the surface treatment agent may be mixed in a solvent and then heated to promote the reaction. The heating temperature is, for example, 30°C or higher and 50°C or lower.

These conductive particles have low connection resistance and excellent connection reliability, so they can be used, for example, in anisotropic conductive films (ACF), heat seal connectors (HSC), and LSI chip circuits for driving electrodes of liquid crystal display panels. It is preferably used as a conductive material for connection to a substrate. As the conductive material, the present conductive particles may be used as they are, or the present conductive particles may be dispersed in a binder resin to form a conductive material. Further, as the conductive material, the present conductive material may be used as it is, or the present conductive material may be used after being dispersed in a binder resin. Other forms of the conductive material are not particularly limited, and in addition to those described above, examples include forms such as an anisotropic conductive paste, a conductive adhesive, and an anisotropic conductive ink.

Examples of the binder resin include thermoplastic resins and thermosetting resins. Examples of thermoplastic resins include acrylic resins, styrene resins, ethylene-vinyl acetate resins, styrene-butadiene block copolymers, etc., and examples of thermosetting resins include epoxy resins, phenol resins, urea resins, Examples include polyester resin, urethane resin, polyimide resin, and the like.

In addition to the conductive particles and binder resin of the present invention, the conductive material may optionally contain a tackifier, a reactive aid, an epoxy resin curing agent, a metal oxide, a photoinitiator, a sensitizer, and a curing agent. Agents, vulcanizing agents, deterioration inhibitors, heat-resistant additives, thermal conductivity improvers, softeners, coloring agents, various coupling agents, metal deactivators, and the like can be blended.

In the conductive material, the amount of conductive particles to be used may be appropriately determined depending on the application, but from the viewpoint of making it easier to obtain electrical continuity without the conductive particles coming into contact with each other, for example, 100 mass of the conductive material is used. It is preferably 0.01 parts by mass or more and 50 parts by mass or less, particularly 0.03 parts by mass or more and 40 parts by mass or less.

Among the forms of the above-mentioned conductive materials, the conductive particles of the present invention are particularly suitable for use as a conductive filler in conductive adhesives.

The conductive adhesive described above is preferably used as an anisotropic conductive adhesive that is placed between two substrates on which a conductive base material is formed, and that adheres and conducts the conductive base materials by applying heat and pressure. . This anisotropically conductive adhesive contains the conductive particles of the present invention and an adhesive resin. The adhesive resin can be used without any particular limitation as long as it is insulating and is used as an adhesive resin. It may be either a thermoplastic resin or a thermosetting resin, and preferably one that exhibits adhesive performance when heated. Such adhesive resins include, for example, thermoplastic types, thermosetting types, ultraviolet curing types, and the like. Additionally, there are so-called semi-thermosetting types, which exhibit intermediate properties between thermoplastic types and thermosetting types, and composite types of thermosetting types and ultraviolet curing types. These adhesive resins can be selected as appropriate depending on the surface characteristics of the circuit board or the like to which they are adhered and the manner in which they are used. In particular, an adhesive resin containing a thermosetting resin is preferable because it has excellent material strength after bonding.

Specific examples of the adhesive resin include ethylene-vinyl acetate copolymer, carboxyl-modified ethylene-vinyl acetate copolymer, ethylene-isobutyl acrylate copolymer, polyamide, polyimide, polyester, polyvinyl ether, polyvinyl butyral, and polyurethane. , SBS block copolymer, carboxyl-modified SBS copolymer, SIS copolymer, SEBS copolymer, maleic acid-modified SEBS copolymer, polybutadiene rubber, chloroprene rubber, carboxyl-modified chloroprene rubber, styrene-butadiene rubber, isobutylene- One or two types selected from isoprene copolymer, acrylonitrile-butadiene rubber (hereinafter referred to as NBR), carboxyl-modified NBR, amine-modified NBR, epoxy resin, epoxy ester resin, acrylic resin, phenol resin, silicone resin, etc. Examples include those prepared using the above-mentioned combinations as main ingredients. Among these, styrene-butadiene rubber, SEBS, and the like are preferred as thermoplastic resins because they have excellent reworkability. Epoxy resin is preferred as the thermosetting resin. Among these, epoxy resins are most preferred because they have high adhesive strength, excellent heat resistance, and electrical insulation, and have low melt viscosity, allowing connection at low pressure.

As the epoxy resin, any commonly used epoxy resin can be used as long as it is a polyvalent epoxy resin having two or more epoxy groups in one molecule. Specific examples include novolac resins such as phenol novolac and cresol novolac, polyhydric phenols such as bisphenol A, bisphenol F, bisphenol AD, resorcinol, and bishydroxydiphenyl ether, ethylene glycol, neopentyl glycol, glycerin, and trimethylolpropane. , obtained by reacting epichlorohydrin or 2-methylepichlorohydrin with polyhydric alcohols such as polypropylene glycol, polyamino compounds such as ethylenediamine, triethylenetetramine, and aniline, and polyhydric carboxy compounds such as adipic acid, phthalic acid, and isophthalic acid. An example is a glycidyl type epoxy resin. Other examples include aliphatic and alicyclic epoxy resins such as dicyclopentadiene epoxide and butadiene dimer diepoxide. These can be used alone or in a mixture of two or more.

In addition, from the viewpoint of preventing ion migration, it is preferable to use high-purity products with reduced impurity ions such as Na ⁺ and Cl ^- and hydrolyzable chlorine as the various adhesive resins.

The amount of conductive particles used in the anisotropic conductive adhesive is usually 0.1 to 30 parts by mass, preferably 0.5 to 25 parts by mass, and more preferably 1 to 20 parts by mass per 100 parts by mass of the adhesive resin component. Department. When the amount of conductive particles used is within this range, increase in connection resistance and melt viscosity can be suppressed, connection reliability can be improved, and connection anisotropy can be sufficiently ensured.

In addition to the conductive particles and adhesive resin described above, the anisotropically conductive adhesive may contain additives known in the art. The blending amount can also be within the range known in the technical field. Other additives include, for example, tackifiers, reactive aids, epoxy resin hardeners, metal oxides, photoinitiators, sensitizers, hardeners, vulcanizing agents, deterioration inhibitors, heat-resistant additives, and heat-resistant additives. Examples include conduction improvers, softeners, colorants, various coupling agents, and metal deactivators.

Examples of the tackifier include rosin, rosin derivatives, terpene resins, terpene phenol resins, petroleum resins, coumaron-indene resins, styrene resins, isoprene resins, alkylphenol resins, xylene resins, and the like. Examples of the reactive auxiliary agent or crosslinking agent include polyols, isocyanates, melamine resins, urea resins, utropins, amines, acid anhydrides, and peroxides. As the epoxy resin curing agent, any one having two or more active hydrogen atoms per minute can be used without particular limitation. Specific examples include polyamino compounds such as diethylenetriamine, triethylenetetramine, metaphenylenediamine, dicyandiamide, and polyamidoamine; organic acid anhydrides such as phthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and pyromellitic anhydride; Examples include novolac resins such as phenol novolac and cresol novolac. These can be used alone or in combination of two or more. Furthermore, a latent curing agent may be used if necessary. Examples of the latent curing agent that can be used include imidazole type, hydrazide type, boron trifluoride-amine complex, sulfonium salt, amine imide, polyamine salt, dicyandiamide, etc., and modified products thereof. These can be used alone or as a mixture of two or more.

The above-mentioned anisotropic conductive adhesive is manufactured using manufacturing equipment commonly used in the technical field. For example, conductive particles and adhesive resin, as well as curing agents and various additives as necessary, are mixed together in an organic solvent if the adhesive resin is a thermosetting resin, or by mixing in an organic solvent if the adhesive resin is a thermoplastic resin. It is produced by melt-kneading at a temperature higher than the softening point of the agent resin, specifically preferably about 50 to 130°C, more preferably about 60 to 110°C. The anisotropically conductive adhesive thus obtained may be applied by coating or in the form of a film.

The connected structure according to the present invention is obtained by connecting two circuit boards using the conductive particles according to the present invention or the conductive material according to the present invention. Examples of the form of the connection structure include a connection structure between a flexible printed circuit board and a glass substrate, a connection structure between a semiconductor chip and a flexible printed circuit board, a connection structure between a semiconductor chip and a glass substrate, and the like.

Hereinafter, the present invention will be further explained with reference to Examples. However, the scope of the present invention is not limited to these examples.

The properties in the examples were measured by the following methods.
(1) Average particle diameter 200 particles are arbitrarily extracted from a scanning electron microscope (SEM) photograph of the measurement target, the particle diameter is measured at a magnification of 10,000 times, and the arithmetic mean value is calculated as the average particle size. The diameter was taken as the diameter.
(2) Thickness of conductive layer Conductive particles were cut into two, and the cross section of the cut end was observed and measured using a scanning electron microscope (SEM).
(3) Variation in the height of the protrusions The height of the protrusions was measured with respect to the cross section of the conductive particles observed by SEM observation, and was determined by the following formula (1).

(4) Radius of curvature Regarding the cross section of the conductive particle observed by SEM observation, let Ra be the radius of the circumscribed circle circumscribing the top part of the cross section of each protrusion, and the radius of the circumscribed circle circumscribing the surface of the lower layer of the conductive layer. was measured as Rb.
(5) Projected area of conductive particles and area of top of protrusion It was measured by importing a SEM photographic image of the conductive particles into an automatic image analysis device (Luzex (registered trademark) AP, manufactured by Nireco Co., Ltd.).

[Example 1]
(1) Pretreatment of core material particles Spherical styrene-acrylate-silica composite resin particles having an average particle diameter of 2.0 μm were used as core material particles. 9 g of the solution was added to 200 mL of an aqueous conditioner solution ("Cleaner Conditioner 231" manufactured by Rohm & Haas Electronic Materials) with stirring. The concentration of the conditioner aqueous solution was 40 mL/L. Subsequently, the solution was stirred for 30 minutes while applying ultrasonic waves at a liquid temperature of 60° C. to perform surface modification and dispersion treatment of the core material particles. This aqueous solution was filtered, and the core material particles, which had been repulped and washed once, were made into a 200 mL slurry. 0.1 g of stannous chloride was added to this slurry. The mixture was stirred at room temperature for 5 minutes to perform a sensitization treatment in which tin ions were adsorbed onto the surface of the core particles. Subsequently, this aqueous solution was filtered, and the core particles, which had been repulped and washed once with water, were made into a 200 mL slurry and maintained at 60°C. 1.5 mL of a 0.11 mol/L palladium chloride aqueous solution was added to this slurry. The mixture was stirred at 60° C. for 5 minutes to perform an activation treatment in which palladium ions were captured on the surface of the core particles. Subsequently, this aqueous solution was filtered, the core material particles that had been repulped and washed once were made into a 100 mL slurry, 10 mL of a 0.5 g/L dimethylamine borane aqueous solution was added, and the mixture was stirred for 2 minutes while applying ultrasonic waves to obtain the pretreated core material. A slurry of particles was obtained.

(2) Preparation of plating solution 5g/L sodium tartrate, 2g/L nickel sulfate hexahydrate, 10g/L trisodium citrate, 0.1g/L sodium hypophosphite, and 2g/L 3L of electroless nickel-phosphorus plating solution was prepared from an aqueous solution containing polyethylene glycol, and the temperature was raised to 70°C.

(3) Electroless plating treatment The slurry of the pretreated core material particles was poured into this electroless plating bath, stirred for 5 minutes, and it was confirmed that hydrogen bubbling had stopped. To this slurry, 420 mL of a 224 g/L nickel sulfate aqueous solution, 420 mL of a mixed aqueous solution containing 210 g/L sodium hypophosphite, and 80 g/L sodium hydroxide were quantitatively added at an addition rate of 2.5 mL/min. Electroless plating was started by continuous fractional addition using a pump. After adding the entire amounts of the nickel sulfate aqueous solution and the mixed aqueous solution of sodium hypophosphite and sodium hydroxide, stirring was continued for 5 minutes while maintaining the temperature at 70°C. Next, the liquid was filtered, and the filtered material was washed three times and then dried in a vacuum dryer at 110° C. to obtain conductive particles having protrusions.

(4) Protrusion treatment Put 20g of the obtained conductive particles together with alumina balls into a ball mill container, add ethanol and crush at 80 rpm for 6 hours, separate the balls and slurry, and dry in a vacuum dryer at 110°C. After drying, conductive particles with low protrusion height were obtained. The height of the protrusions of the obtained conductive particles was 100.8 nm.

(5) Vacuum heat treatment The obtained conductive particles were placed in a rectangular container so as to have a thickness of 5 mm. This was placed in a vacuum heating furnace (manufactured by Denken High Dental Co., Ltd., KDF-75), and the degree of vacuum was set to 10 Pa and maintained for 10 minutes. Thereafter, the temperature was increased and heat treatment was performed at 390° C. for 2 hours. After the heat treatment, the mixture was allowed to cool to room temperature (25° C.), and then the vacuum was released by purging nitrogen gas to obtain heat-treated conductive particles. A SEM photograph of the obtained conductive particles is shown in FIG. The average particle diameter of the obtained conductive particles was 2.2 μm, the thickness of the conductive layer was 110 nm, and the height of the protrusions was 100.8 nm. Table 1 shows the physical property values of the obtained conductive particles.

[Example 2]
(1) Pretreatment of core material particles The same operation as in Example 1 was performed except that resin particles with an average particle diameter of 2.0 μm (manufactured by Nissan Chemical Co., Ltd., Optobeads) were used as core material particles, and pretreatment was completed. A slurry of core material particles was obtained.
(2) Preparation of plating solution An electroless plating solution was prepared in the same manner as in Example 1 (2).
(3) Electroless plating treatment The same operation as in Example 1 (3) was performed to obtain conductive particles having protrusions.
(4) Protrusion treatment The same operation as in Example 1 (4) was performed to obtain conductive particles with a protrusion height of 101 nm.
(5) Vacuum heat treatment The same operation as in Example 1 was performed to obtain heat-treated conductive particles. The average particle diameter of the obtained conductive particles was 2.2 μm, the thickness of the conductive layer was 94.8 nm, and the height of the protrusions was 101 nm. Table 1 shows the physical property values of the obtained conductive particles.

[Example 3]
The same operations as in Example 1 were performed up to (3) electroless plating treatment in Example 1 to obtain conductive particles having protrusions.
(4) Protrusion treatment The same operation as in Example 1 was performed except that the obtained conductive particles were crushed for 3 hours to obtain conductive particles having a protrusion height of 145.3 nm.
(5) Vacuum heat treatment The same operation as in Example 1 was performed to obtain heat-treated conductive particles. A SEM photograph of the obtained conductive particles is shown in FIG. The average particle diameter of the obtained conductive particles was 2.2 μm, the thickness of the conductive layer was 97.8 nm, and the height of the protrusions was 145.3 nm. Table 1 shows the physical property values of the obtained conductive particles.

[Example 4]
The same operations as in Example 1 were performed up to (3) electroless plating treatment in Example 1 to obtain conductive particles having protrusions.
(4) Protrusion treatment The same operation as in Example 1 was performed except that the obtained conductive particles were crushed at 80 rpm for 4 hours using a zirconia ball, and the conductive particles with a protrusion height of 115.6 nm were obtained. Particles were obtained.
(5) Vacuum heat treatment The same operation as in Example 1 was performed to obtain heat-treated conductive particles. A SEM photograph of the obtained conductive particles is shown in FIG. The average particle diameter of the obtained conductive particles was 2.2 μm, the thickness of the conductive layer was 95.8 nm, and the height of the protrusions was 115.6 nm. Table 1 shows the physical property values of the obtained conductive particles.

[Comparative example 1]
In Example 1, conductive particles were obtained by performing the same operations as in Example 1 except that (4) the planar protrusion treatment was not performed. Table 1 shows the physical property values of the obtained conductive particles.

[Comparative example 2]
The same operations as in Example 1 were performed up to (3) electroless plating treatment in Example 1 to obtain conductive particles having protrusions.
(4) Protrusion treatment The same operation as in Example 1 was performed except that the obtained conductive particles were crushed for 1 hour to obtain conductive particles with a protrusion height of 174.9 nm.
(5) Vacuum heat treatment The same operation as in Example 1 was performed to obtain heat-treated conductive particles. A SEM photograph of the obtained conductive particles is shown in FIG. The average particle diameter of the obtained conductive particles was 2.2 μm, the thickness of the conductive layer was 99.9 nm, and the height of the protrusions was 174.9 nm. Table 1 shows the physical property values of the obtained conductive particles.

[Evaluation of connection resistance and insulation]
Using the conductive particles of Examples and Comparative Examples, connection resistance and insulation were evaluated by the following method.
An insulating adhesive prepared by mixing 100 parts by mass of an epoxy resin, 150 parts by mass of a curing agent, and 70 parts by mass of toluene, and 15 parts by mass of conductive particles obtained in Examples or Comparative Examples are mixed, An insulating paste was obtained. This paste was applied onto a siliconized polyester film using a bar coater, and then the paste was dried to form a thin film on the film. The obtained thin film-forming film was placed between a glass substrate on which aluminum electrodes were vapor-deposited and a polyimide film substrate on which copper electrode patterns were formed at a pitch of 50 μm, and then pressure-bonded to prepare a sample for measuring continuity resistance. Created. An electrical connection was made to the obtained sample for measuring conduction resistance, and the connection resistance value of this sample was measured at room temperature (25° C., 50% RH) to evaluate the connection resistance. The connection resistance was evaluated using a multimeter R6552 (manufactured by Advantest Co., Ltd.) according to the following criteria. The results are shown in Table 2.
○: Resistance value is less than 2Ω △: Resistance value is 2Ω or more and less than 5Ω ×: Resistance value is 5Ω or more

Furthermore, in the 100 samples for measuring conduction resistance, insulation properties were evaluated based on the percentage of short circuits that occurred. Insulation properties were evaluated using the following method. The results are shown in Table 2.
○: Short circuit occurrence rate is less than 5% △: Short circuit occurrence rate is 5% or more and less than 30% ×: Short circuit occurrence rate is 30% or more

From these results, it can be seen that the conductive particles obtained in the examples have a lower connection resistance value and superior insulation properties than the conductive particles obtained in the comparative examples.

DESCRIPTION OF SYMBOLS 1... Conductive particle 2... Core material particle 3... Conductive layer 4... Protrusion part 5... Protrusion

flat part

5a and 5b... End of flat part 6... Conductive layer surface of the lower layer of

Claims

A conductive particle having a core particle and a conductive layer having a plurality of protrusions on the surface of the core particle, and a variation in the height of the protrusions is 0.01 or more and 0.25 or less.
The conductive particle according to claim 1, wherein the top portion of the protrusion has a substantially planar shape.
When the radius of curvature of the top portion of the protrusion is Ra, and the radius of curvature of the surface of the lower layer of the conductive layer at the portion where the protrusion is formed is Rb, the ratio of Ra to Rb (Ra/Rb) is 0. The conductive particles according to claim 1, which have a particle size of 15 or more and 1.20 or less.
The conductive particles according to claim 1, wherein the ratio of the total area of the top portions of the projections to the projected area of the conductive particles is 0.50 or more.
The conductive particles according to claim 1, wherein the conductive layer contains at least one selected from the group consisting of nickel, gold, and palladium.
The conductive particles according to claim 1, having an average particle diameter of 0.1 μm or more and 50 μm or less.
The conductive particles according to claim 1, wherein the conductive layer has a thickness of 0.1 nm or more and 2,000 nm or less.
The conductive particle according to claim 1, wherein the height of the protrusion is 20 nm or more and 1,000 nm or less.
The conductive particle according to claim 1, wherein the shape of at least one of the protrusions is amorphous.
A conductive material comprising the conductive particles according to any one of claims 1 to 9 and an insulating resin.
a step of forming a conductive layer on the surface of the core material particles;
forming protrusions protruding from the surface of the conductive layer, and
A method for producing conductive particles, comprising the step of leveling the height of the protrusions.
12. The method for producing conductive particles according to claim 11, wherein the step of forming the protrusions forms the protrusions on the conductive layer using autolyzed products of an electroless nickel plating bath as nuclei.
13. The step of leveling the height of the projection includes polishing the top portion of the projection obtained in the step of forming the projection to level the height of the projection. A method for producing conductive particles.