JP5900535B2 - Conductive particles, insulating coated conductive particles, anisotropic conductive adhesive, and method for producing conductive particles - Google Patents

Description

  The present invention relates to conductive particles, insulating coated conductive particles, anisotropic conductive adhesives, adhesive films, connection structures, and methods for producing conductive particles.

  The method of mounting the liquid crystal driving IC on the glass panel for liquid crystal display can be roughly divided into two types, COG (Chip-on-Glass) mounting and COF (Chip-on-Flex) mounting. In COG mounting, a liquid crystal driving IC is directly bonded onto a glass panel using an anisotropic conductive adhesive containing conductive particles. On the other hand, in COF mounting, a liquid crystal driving IC is bonded to a flexible tape having metal wiring, and these are bonded to a glass panel using an anisotropic conductive adhesive containing conductive particles. Anisotropy here means conducting in the pressurizing direction and maintaining insulation in the non-pressurizing direction.

  As the conductive particles used for the anisotropic conductive adhesive, conductive particles having a gold layer formed on the surface are the mainstream. The gold layer has a low electric resistance value and has no fear of oxidation, so that a low resistance value can be maintained for a long time.

  By the way, in recent years, in the field of electronic devices such as liquid crystal displays, personal computers, and mobile phones, from the viewpoint of energy saving, it is required to further reduce the amount of current flowing through an integrated circuit in order to reduce the power consumption of the electronic device. ing. Therefore, there is a demand for conductive particles that can further reduce the conduction resistance between the electrodes, and there is also a situation in which the price of gold is soaring, and a new technology for improving the conductivity of the conductive particles is required. ing.

  Various techniques for reducing the connection resistance of conductive particles have been studied so far. For example, Patent Documents 1 and 2 listed below disclose methods for forming conductive protrusions on the surface of conductive particles. ing. Specifically, in Patent Document 1, by utilizing the self-decomposition of a nickel plating solution in an electroless nickel plating method, a nickel microprojection and a nickel coating are simultaneously formed on non-conductive particles, and the surface is electrically conductive. A method for producing conductive particles having a plurality of protrusions is described. Patent Document 2 describes a method for producing conductive particles having conductive protrusions on the surface by attaching a conductive substance serving as a core substance to the surface of the substrate fine particles, and further performing electroless nickel plating. ing.

JP 2012-113850 A Japanese Patent No. 4674096

  When a chip is mounted with an anisotropic conductive adhesive, it is necessary to lower the conduction resistance between the electrodes to be connected and to sufficiently increase the insulation resistance between the chip electrodes. However, the connection structure obtained by the anisotropic conductive adhesive blended with the conductive particles described in Patent Documents 1 and 2 shows a sufficient insulation resistance value in the initial stage of connection, but for a long time under high temperature and high humidity. The insulation resistance value may decrease after the migration test for conducting, which is problematic in terms of insulation reliability.

  An object of the present invention is to provide conductive particles capable of achieving both low conduction resistance and high insulation reliability when used as conductive particles blended in an anisotropic conductive adhesive, and a method for producing the same. To do. Another object of the present invention is to provide insulating coated conductive particles, anisotropic conductive adhesives and adhesive films using the above conductive particles, and connection structures using anisotropic conductive adhesives. .

  In order to solve the above problems, the present inventors have examined the reason why the above-described insulation resistance value is lowered. As a result, the conductive particles described in Patent Documents 1 and 2 have an abnormal size when attempting to increase the conductivity. As a result, it was found that the presence of conductive particles having such abnormal protrusions leads to a decrease in insulation reliability. That is, in the method described in Patent Document 1, it is extremely difficult to control the number, size, and shape of the protrusions. When an attempt is made to enlarge the protrusions in order to reduce the electric resistance value, the height is 500 nm as an abnormal precipitation portion. Protrusions exceeding 1 are easily formed. In the method described in Patent Document 2, it is necessary to attach a sufficient amount of the core material to the surface of the substrate fine particles in order to reduce the electric resistance value. However, if the amount of the core material is increased, the core material itself aggregates. However, protrusions having a height exceeding 500 nm are likely to be formed.

  As a result of further intensive studies based on such findings, the present inventors have provided a first nickel layer on the surface of the resin particles, and after forming particles containing palladium on the first nickel layer, the second further By providing the nickel layer, the number, size and shape of the protrusions formed by the second nickel layer can be controlled to a high degree, and the anisotropic conductive adhesive containing the obtained conductive particles is reliable in conduction. The present invention has been completed by finding that a connection structure excellent in both properties and insulation reliability can be obtained.

  That is, the present invention includes resin particles and a metal layer containing nickel provided on the surface of the resin particles, and the metal layer has a length in the thickness direction of the metal layer of 4 nm or more and contains palladium. First conductive particles containing grains and having protrusions on the outer surface are provided.

  According to the first conductive particle of the present invention, by providing the above configuration, the protrusion of the conductive particle can be sufficiently controlled, and as a result, the conductive particle is used as a conductive particle blended in the anisotropic conductive adhesive. In this case, both low conduction resistance and high insulation reliability can be achieved.

  By the way, as a pretreatment when performing electroless nickel plating on a base material, a palladium catalyst treatment for capturing palladium ions on the surface of the base material is generally known. This palladium catalyzed treatment forms palladium precipitation nuclei on the substrate surface, and the size of the precipitation nuclei is at the atomic level. On the other hand, the particles containing palladium according to the present invention have a size that enables component analysis by EDX, which will be described later. Further, the projections according to the present invention cannot be formed from the precipitation nuclei of palladium formed by a general palladium catalyst treatment.

  The metal layer contains particles containing palladium whose shortest distance to the interface between the metal layer and the resin particles is 0.1 × d or more, where d is the average thickness of the metal layer. Can do.

  The present invention also includes resin particles and a metal layer containing nickel provided on the surface of the resin particles, and the metal layer has a metal layer and a resin when the average thickness of the metal layer is d. Provided is a second conductive particle containing particles containing palladium having a shortest distance to the interface with the particle of 0.1 × d or more and having protrusions on the outer surface.

  According to the second conductive particle of the present invention, by providing the above configuration, the protrusion of the conductive particle can be sufficiently controlled, and as a result, the conductive particle is used as a conductive particle blended in the anisotropic conductive adhesive. In this case, both low conduction resistance and high insulation reliability can be achieved.

  In the first conductive particle and the second conductive particle of the present invention, the metal layer may contain particles containing palladium whose shortest distance to the interface between the metal layer and the resin particle is 10 nm or more. .

  The said metal layer can contain the particle | grains containing the said palladium dotted in the direction orthogonal to the thickness direction of this metal layer.

  The metal layer may contain particles containing the palladium passing through a straight line connecting the apex of the protrusion and the interface between the metal layer and the resin particle in the shortest distance.

  The particles containing palladium may be reduced deposits of an electroless palladium plating solution containing palladium ions and a reducing agent.

  From the viewpoint of increasing the number of protrusions and obtaining a low electric resistance value, the content of palladium in the particles containing palladium is preferably 94% by mass or more.

  The particles containing palladium may contain phosphorus. Thereby, the hardness of the particle | grains containing palladium can be raised, and the electrical resistance value when an electrically-conductive particle is compressed can be kept low.

  From the viewpoint of highly controlling the number, size, and shape of the protrusions, the metal layer contains a first layer containing nickel and a second layer containing nickel in the order closer to the resin particles. It is preferable that the content of nickel in the first layer is 83 to 98% by mass, and the content of nickel in the second layer is 93% by mass or more. As a result, it is possible to achieve both low conduction resistance and high insulation reliability at a higher level.

  From the viewpoint of obtaining a low electrical resistance value by increasing the number of protrusions, the nickel content in the first layer is preferably 85 to 93 mass%.

  From the viewpoint of obtaining a low electric resistance value, the nickel content in the second layer is preferably 96% by mass or more.

  The first layer can include phosphorus. Thereby, the hardness of the first layer can be increased, and the electric resistance value when the conductive particles are compressed can be kept low.

  The second layer can include phosphorus or boron. Thereby, the hardness of the second layer can be increased, and the electric resistance value when the conductive particles are compressed can be kept low.

  The metal layer may further contain a third layer containing palladium on the opposite side of the second layer from the first layer. Palladium has a property that it is less likely to be oxidized than nickel, and because palladium has a high effect of suppressing the diffusion of nickel and can prevent the diffusion of nickel to the palladium surface. By covering the second layer containing with the third layer containing palladium, it becomes possible to suppress the oxidation of the surface of the conductive particles, and as a result, the electric resistance value when the conductive particles are compressed is kept low. be able to.

  The metal layer may further contain a fourth layer containing gold on the opposite side of the second layer from the first layer. The metal layer contains a fourth layer containing gold outside the second layer because gold has a property that it is less likely to be oxidized than nickel and the resistance value of gold itself is lower than that of nickel. By doing so, the electrical resistance value when the conductive particles are compressed can be kept low.

  The present invention includes a step of forming a first layer containing nickel on the surface of resin particles by electroless nickel plating, and reduction of an electroless palladium plating solution containing palladium ions and a reducing agent on the first layer. Production of conductive particles comprising: a step of forming particles containing palladium by precipitation; and a step of forming a second layer containing nickel by electroless nickel plating on the first layer and the particles containing palladium. Provide a method.

  According to the method for producing conductive particles of the present invention, by having the above configuration, the number, size, and shape of the protrusions formed by the second nickel layer can be highly controlled, and the low conduction resistance and the high Conductive particles that can achieve both insulation reliability can be obtained.

  The present invention provides insulating coated conductive particles comprising the above conductive particles of the present invention and insulator particles covering at least part of the surface of the metal layer of the conductive particles.

  According to the insulating coated conductive particles of the present invention, when used as the insulating coated conductive particles blended in the anisotropic conductive adhesive, it is possible to achieve both low conduction resistance and high insulation reliability.

  The present invention provides a first anisotropic conductive adhesive containing the conductive particles of the present invention or the conductive particles obtained by the production method of the present invention and an adhesive.

  According to the first anisotropic conductive adhesive of the present invention, by containing the conductive particles according to the present invention, the connection structure excellent in both conduction reliability and insulation reliability when the circuit electrodes are connected to each other. You can get a body.

  The present invention further provides a second anisotropic conductive adhesive containing the insulating coated conductive particles of the present invention and an adhesive.

  According to the second anisotropically conductive adhesive of the present invention, by including the insulating coated conductive particles according to the present invention, both the conductive reliability and the insulating reliability are excellent when the circuit electrodes are connected to each other. A connection structure can be obtained.

  The present invention also provides an anisotropic conductive adhesive film formed by forming the anisotropic conductive adhesive according to the present invention into a film.

  The present invention further includes a first circuit member having a first circuit electrode and a second circuit member having a second circuit electrode, wherein the first circuit electrode and the second circuit electrode are opposed to each other. The anisotropic conductive adhesive according to the present invention is interposed between the first circuit member and the second circuit member, and the first circuit electrode and the second circuit are heated and pressed by heating them. Provided is a connection structure in which a circuit electrode is electrically connected.

  ADVANTAGE OF THE INVENTION According to this invention, when it uses as an electroconductive particle mix | blended with an anisotropic conductive adhesive, it can provide the electroconductive particle which can make low conduction | electrical_connection resistance and high insulation reliability compatible, and its manufacturing method. it can. In addition, according to the present invention, it is possible to provide an insulating coated conductive particle using the above conductive particles, an anisotropic conductive adhesive and an adhesive film, and a connection structure using the anisotropic conductive adhesive. .

1A is a schematic cross-sectional view showing one embodiment of the conductive particles according to the present invention, and FIG. 1B is a schematic cross-section showing one embodiment of the insulating coated conductive particles according to the present invention. FIG. It is a schematic diagram for demonstrating the electroconductive particle which concerns on this invention. It is a schematic diagram for demonstrating the electroconductive particle which concerns on this invention. 1 is a schematic cross-sectional view showing an embodiment of a connection structure in which circuit electrodes are connected by an anisotropic conductive adhesive according to the present invention. It is a schematic cross section for demonstrating an example of the manufacturing method of the connection structure shown in FIG. 2 is an SEM image obtained by observing particles obtained in step c in producing conductive particles of Example 1. FIG. 2 is an SEM image obtained by observing the surface of particles obtained in step c in the production of conductive particles of Example 1. FIG. 2 is an SEM image obtained by observing the conductive particles obtained in Example 1. FIG. It is the STEM image which observed the cross section of the electrically-conductive particle obtained in Example 1, and the mapping figure of nickel, phosphorus, and palladium by EDX. It is a figure for demonstrating the method of calculating | requiring the height of the particle | grains containing palladium from the mapping figure of palladium by EDX of FIG. It is a schematic diagram for demonstrating a trimming process. It is a schematic diagram for demonstrating the method of producing the thin film slice for TEM measurement. It is a figure for demonstrating the method to obtain | require the height of protrusion from the STEM image of FIG. It is a schematic diagram for demonstrating an abnormal precipitation part. 3 is an SEM image obtained by observing particles after a palladium catalyst treatment in the production of conductive particles of Comparative Example 1. FIG. 4 is an SEM image obtained by observing the conductive particles obtained in Comparative Example 1. It is the STEM image which observed the cross section of the electrically-conductive particle obtained in the comparative example 1, and the mapping figure of nickel, phosphorus, and palladium by EDX.

  Hereinafter, preferred embodiments of the present invention will be described in detail. 1A is a schematic cross-sectional view showing one embodiment of the conductive particles according to the present invention, and FIG. 1B is a schematic cross-section showing one embodiment of the insulating coated conductive particles according to the present invention. FIG.

<Conductive particles>
First, the conductive particles of this embodiment will be described.

  The conductive particle 2 shown in FIG. 1A includes a resin particle 203 that forms a core of the conductive particle, and a metal layer 204 containing nickel provided on the surface of the resin particle 203. The metal layer 204 includes: The metal layer has a length in the thickness direction of 4 nm or more, contains particles 201 containing palladium, and has protrusions 205 on the outer surface.

  The metal layer 204 containing nickel included in the conductive particles 2 is composed of two layers of a first layer 200 containing nickel and a second layer 202 containing nickel in the order closer to the resin particles 203. You may have the above structure.

  The material of the resin particles 203 is not particularly limited, and examples thereof include acrylic resins such as polymethyl methacrylate and polymethyl acrylate, and polyolefin resins such as polyethylene, polypropylene, polyisobutylene, and polybutadiene. Further, as the resin particles, for example, crosslinked acrylic particles, crosslinked polystyrene particles and the like can be used.

  The resin particles are preferably spherical, and the average particle size is preferably 1 to 10 μm, and more preferably 2 to 5 μm. The average particle size of the resin particles in the present embodiment is obtained by measuring the particle size of 300 arbitrary resin particles by observation using a scanning electron microscope (hereinafter, SEM) and taking the average value thereof. .

  The first layer 200 containing nickel preferably has a nickel content of 83 to 98% by mass, more preferably 85 to 93% by mass, and still more preferably 86 to 91% by mass. By setting the content within the above range, it is possible to suppress the variation in the shape of the particles containing palladium formed on the first layer, and it is easy to distribute the particles at a high density. As a result, it is possible to suppress variations in the protrusion shape on the outer surface of the metal layer and to form protrusions with high density.

  The first layer can be formed by, for example, electroless nickel plating. In this case, it is preferable to treat the resin particles with a palladium catalyst. The palladium catalyst treatment can be performed by a known method, and the method is not particularly limited. Examples thereof include a catalyst treatment method using a catalyst treatment solution called an alkali seeder or an acid seeder.

  Examples of the catalytic treatment method using an alkali seeder include the following methods. The resin particles are immersed in a palladium ion solution coordinated with 2-aminopyridine to adsorb palladium ions on the surface of the resin particles. After washing with water, the resin particles adsorbed with palladium ions are further added to sodium hypophosphite, hydrogen A reduction treatment is performed by dispersing in a solution containing a reducing agent such as sodium borohydride, dimethylamine borane, hydrazine, formalin, etc., and palladium ions adsorbed on the surface of the resin particles are reduced to metallic palladium.

  Examples of the catalytic treatment method using an acidic seeder include the following methods. Resin particles are dispersed in a stannous chloride solution and subjected to a sensitization treatment in which tin ions are adsorbed on the surface of the resin particles, and then washed with water. Next, it is dispersed in a solution containing palladium chloride, and after an activation treatment for trapping palladium ions on the surface of the resin particles, it is washed with water. Furthermore, it is dispersed in a solution containing a reducing agent such as sodium hypophosphite, sodium borohydride, dimethylamine borane, hydrazine, formalin, etc., and subjected to reduction treatment, and the palladium ions adsorbed on the surface of the resin particles are converted into metallic palladium. To reduce.

  In these palladium-catalyzed treatment methods, palladium ions are adsorbed on the surface, washed with water, and further dispersed in a solution containing a reducing agent to reduce the palladium ions adsorbed on the surface, so that the atomic level is reduced. A large palladium precipitation nucleus is formed.

  The first layer preferably contains phosphorus or boron, and more preferably contains phosphorus. Thereby, the hardness of the first layer can be increased, and the electrical resistance value when the conductive particles are compressed can be easily kept low.

  When the first layer is formed by electroless nickel plating, phosphorus can be co-deposited by using a phosphorus-containing compound such as sodium hypophosphite as a reducing agent, and a first nickel-phosphorous alloy is included. Can be formed. Further, by using a boron-containing compound such as dimethylamine borane, sodium borohydride, or potassium borohydride as a reducing agent, boron can be co-deposited, and the first layer containing a nickel-boron alloy is formed. Can be formed. Since the nickel-phosphorus alloy has a lower hardness than the nickel-boron alloy, the first layer contains the nickel-phosphorus alloy from the viewpoint of suppressing cracking of the first layer when the conductive particles are highly compressed and crimped. It is preferable.

  In addition, the content of the element in the first layer is, for example, cut out a cross section of the conductive particles by an ultramicrotome method, observed at a magnification of 250,000 times using a transmission electron microscope (hereinafter, TEM), and attached to the TEM It can be calculated by component analysis using an energy dispersive X-ray detector (hereinafter referred to as EDX).

  The thickness of the first layer is preferably 20 to 200 nm, more preferably 20 to 150 nm, and still more preferably 60 to 100 nm. When the thickness of the first layer is within the above range, cracking of the first layer is easily suppressed when the conductive particles are highly compressed and crimped.

  The particles containing palladium are preferably scattered inside the metal layer.

  2 and 3 are schematic views showing a part of a cross section when the conductive particles of the present embodiment are cut along a plane passing through the vicinity of the center of the conductive particles. In FIG. 2 and FIG. 3, in order to make it easy to explain the size and location of grains containing palladium, the cutting plane passes through the apexes of two adjacent protrusions, and the cutting plane is near the center of the grain containing palladium. A cross-section through is shown.

  In the grain 201 containing palladium, the length D1 in the thickness direction of the metal layer 204 containing nickel is preferably 4 nm or more, more preferably 6 nm or more, and still more preferably 8 nm or more. When particles containing palladium having a length in the above range are included in the metal layer, protrusions with a sufficiently high height are easily formed on the outer surface of the metal layer. Further, from the viewpoint of easily forming a sufficiently high protrusion on the outer surface of the metal layer by interspersing particles containing palladium, D1 is preferably 35 nm or less, and more preferably 25 nm or less.

  In order to obtain the length D1 of the particle containing palladium, first, a thin film slice-like sample is prepared by an ultramicrotome method, a focused ion beam processing method, a cryoultramicrotome processing method, or the like, and a cross section of a conductive particle is cut out. Subsequently, the sample on the thin film slice is observed at a magnification of 250,000 times using a TEM, and D1 is obtained from a mapping diagram of palladium obtained by EDX attached to the TEM.

  In this embodiment, when the conductive particles are cut along a plane passing through the vicinity of the center of the particles, it is preferable that the average length of the particles containing palladium, which is confirmed by the above method, is 4 to 35 nm. 6 to 25 nm is more preferable, and 12 to 20 nm is still more preferable. The average number of grains can be ten.

  In the present embodiment, the metal layer 204 is a particle containing palladium whose shortest distance to the interface between the metal layer and the resin particles is 0.1 × d or more when the average thickness of the metal layer 204 is d. It is preferable to contain. That is, the shortest distance D2 between the surface S1 on the resin particle 203 side of the particle 201 containing palladium shown in FIG. 2 and the interface S2 between the metal layer 204 and the resin particle 203 is preferably 0.1 × d or more. . 2 represents the average thickness of the metal layer 204.

  Since the metal layer containing nickel having a thickness of 0.1 × d or more exists between the particles 201 containing palladium and the resin particles 203, the length in the thickness direction of the metal layer is 4 nm or more. The particles 201 containing palladium can be easily formed. That is, when a metal layer containing nickel having a thickness of 0.1 × d or more is present, the reducing agent is adsorbed on the metal layer containing nickel, and oxidation reaction of the reducing agent, that is, reduction of palladium ions. Since the reaction proceeds continuously, it is possible to grow grains containing palladium. As a result, grains containing palladium having a length in the thickness direction of the metal layer of 4 nm or more can be grown, and the second layer containing nickel formed thereon can obtain a low conduction resistance. Can have protrusions.

  Note that it is difficult to form particles 201 containing palladium having a length of 4 nm or more on the surface of the resin particles 203. The particle 201 containing palladium having a length of 4 nm or more is formed by reducing and depositing with an electroless palladium plating solution containing palladium ions and a reducing agent. Even if it is going to form the particle | grains containing palladium, since it is hard to adsorb | suck to the surface of the resin particle 203 and the oxidation reaction of a reducing agent does not advance, it is difficult to enlarge the particle | grains containing palladium. The size of the palladium precipitation nuclei at this time is considered to be at the atomic level, and even if the second layer containing nickel is formed thereon, a smooth film is formed and a shape having protrusions cannot be formed. Can't get resistance.

  In addition, to control the size of the protrusion to a certain size on the entire surface of one conductive particle, to further reduce the variation in the shape of the protrusion between the conductive particles, and to stably obtain a low conduction resistance between the conductive particles. Further, the D2 is more preferably 0.2 × d or more, and further preferably 0.4 × d or more. In order to obtain a low conduction resistance value and high insulation reliability, the D2 is preferably 0.7 × d or less, and more preferably 0.4 × d or less.

  The average thickness d of the metal layer 204 is determined by cutting out a cross section of the particle by an ultramicrotome method so as to pass near the center of the particle, observing it at a magnification of 250,000 times using a TEM, and from the obtained image, The cross-sectional area of the layer 204 is estimated and calculated from the cross-sectional area.

  The D2 can be obtained based on, for example, a palladium mapping diagram obtained by EDX of a cross section passing through the vicinity of the center of the conductive particles. In addition, about the interface S2 of the metal layer 204 and the resin particle 203, it can confirm from the mapping figure of nickel obtained by EDX.

  If the first nickel layer is a continuous film without pinholes and the resin particles are completely covered with nickel, particles 201 containing palladium of 4 nm or more are formed on the entire conductive particles, Since the protrusions in the two nickel layers are entirely formed in one conductive particle, it is possible to obtain a lower conduction resistance value. For these reasons, the D2 is preferably 10 nm or more, more preferably 20 nm or more, and further preferably 40 nm or more.

  In this embodiment, it is preferable that the metal layer 204 contains the particle | grains containing the palladium whose diameter D3 in the direction orthogonal to the thickness direction of a metal layer is 5-100 nm. When the size of the particles containing palladium is in the above range, protrusions of a sufficiently large size are easily formed on the outer surface of the metal layer with a sufficient density. From such a viewpoint, D3 is more preferably 7 to 80 nm, and further preferably 20 to 60 nm.

  The number of particles containing palladium having a diameter of 20 to 60 nm is preferably 50% or more, more preferably 60% or more, and 70% or more with respect to the total number of particles containing palladium having a length of 4 nm or more. More preferably.

  Further, the ratio [D1 / D3] of the length D1 of the metal layer containing palladium in the thickness direction D1 to the diameter D3 in the direction perpendicular to the thickness direction of the metal layer is preferably 0.1 or more. 0.2 or more is more preferable, and 0.3 or more is still more preferable. By including grains having such a ratio in the above range in the metal layer, it is possible to easily control the shape of the protrusions formed on the outer surface of the metal layer.

  The particles containing palladium are preferably included in a range within ± 45% of the average thickness from the center of the average thickness of the metal layer. In the cross section of the conductive particle shown in FIG. 3, the broken line C1 indicates the center of the average thickness of the metal layer 204, and the average thickness of the metal layer 204 is a distance of d / 2 from the broken line C1 in the thickness direction of the metal layer. And the surface of the resin particles are located. In this case, it is preferable that the particles 201 containing palladium exist within a range of ± 0.45 × d from C1. After forming the second nickel layer, in order to suppress the variation in the shape of the protrusion and to obtain a low conduction resistance value and a high insulation reliability, the grains 201 containing palladium are present in the range of ± 0.3 × d from C1. More preferably, it is more preferably within the range of ± 0.2 × d.

  The number of particles containing palladium in the conductive particles is preferably 20 or more in a concentric circle having a diameter that is ½ of the diameter of the conductive particles on the SEM orthographic projection surface of the conductive particles, and is 60 or more. More preferably, it is more preferably 100 or more. When the number of particles containing palladium is in the above range, a sufficient number of protrusions can be formed on the outer surface of the metal layer. As a result, a lower electrical resistance value can be obtained when the conductive particles are interposed between the opposing electrodes and the electrodes are crimped together.

  In the conductive particles of the present embodiment, from the viewpoint of forming a sufficient number of protrusions on the outer surface of the metal layer and further reducing the electrical resistance value at the time of connection, the direction in which the particles containing palladium are orthogonal to the thickness direction of the metal layer It is preferable to be scattered. The grains containing palladium are preferably scattered in a direction perpendicular to the thickness direction of the metal layer without contacting each other. The number of particles containing palladium that are in contact with each other is preferably 15 or less in one conductive particle, more preferably 7 or less, and 0 particles, that is, particles containing palladium are not in contact with each other. More preferably, all are scattered.

  Further, in the conductive particles of the present embodiment, the metal layer includes particles containing palladium passing through a straight line connecting the apex of the protrusion formed on the outer surface of the metal layer and the interface between the metal layer and the resin particle at the shortest. Is preferred. In the cross section of the conductive particle shown in FIG. 3, L1 is a straight line that connects the apex T1 of the protrusion and the interface S2 between the resin particle 203 and the metal layer 204 in the shortest distance. The metal layer 204 shown in FIG. 3 includes grains 201 containing palladium through which L1 passes. Thus, it is preferable that the protrusion of the metal layer is formed at a position corresponding to the particle containing palladium.

  Note that whether or not the metal layer includes particles containing palladium through which the straight line L1 passes includes, for example, cutting the conductive particles at a cutting plane where the vicinity of the center of the conductive particles and the apex of the protrusion pass, It can be confirmed by the mapping diagram of palladium obtained by EDX.

  In the conductive particles according to the present embodiment, the ratio (coverage) of the area of the particles containing palladium covering the first layer is preferably 1 to 70%, more preferably 3 to 50%. Preferably, it is more preferable that it is 5 to 30%. When the coverage is in the above range, a good protrusion shape can be easily obtained on the outer surface of the metal layer. As a result, a lower electrical resistance value can be obtained when the conductive particles are interposed between the opposing electrodes and the electrodes are crimped together.

  The shape of the particles containing palladium is not particularly limited, but is preferably an ellipsoid, a sphere, a hemisphere, a substantially ellipsoid, a substantially sphere, a substantially hemisphere, or the like. Among these, a hemisphere or a substantially hemisphere is preferable.

  The particles containing palladium can be formed, for example, by reducing and depositing with an electroless palladium plating solution containing palladium ions and a reducing agent.

The source of palladium used in the electroless palladium plating solution is not particularly limited, and examples thereof include palladium compounds such as palladium chloride, sodium palladium chloride, ammonium ammonium chloride, palladium sulfate, palladium nitrate, palladium acetate, and palladium oxide. Specifically, acidic palladium chloride “PdCl ₂ / HCl”, tetraamminepalladium nitrate “Pd (NH ₃ ) ₄ (NO ₃ ) ₂ ”, dinitrodiammine palladium “Pd (NH ₃ ) ₂ (NO ₂ ) ₂ ”, dicyano Diammine palladium “Pd (CN) ₂ (NH ₃ ) ₂ ”, dichlorotetraammine palladium “Pd (NH ₃ ) ₄ Cl ₂ ”, palladium sulfamate “Pd (NH ₂ SO ₃ ) ₂ ”, diammine palladium sulfate “Pd (NH ₃ ) ₂ SO ₄ ”, tetraamminepalladium oxalate“ Pd (NH ₃ ) ₄ C ₂ O ₄ ”, palladium sulfate“ PdSO ₄ ”and the like can be used.

  Although there is no restriction | limiting in particular as a reducing agent used for an electroless palladium plating solution, From a viewpoint which can fully raise the content of palladium in the particle | grains containing palladium obtained, and can suppress the dispersion | variation in the shape of a particle | grain, use a formate compound Is preferred. Moreover, phosphorus-containing compounds, such as hypophosphorous acid and phosphorous acid, or a boron containing compound can be used as a reducing agent. In that case, since the obtained particles containing palladium contain a palladium-phosphorus alloy or palladium-boron alloy, the concentration of reducing agent, pH, plating so that the content of palladium in the particles containing palladium is as desired. It is preferable to adjust the temperature of the liquid.

  Moreover, although a buffering agent etc. can be added to an electroless palladium plating solution as needed, the kind is not specifically limited.

  The content of palladium in the particles containing palladium is preferably 94% by mass or more, more preferably 97% by mass or more, and further preferably 99% by mass or more. When the content of palladium in the particles containing palladium is in the above range, the size and number of protrusions formed on the outer surface of the metal layer can be made in a better range. As a result, a lower electrical resistance value can be obtained when the conductive particles are interposed between the opposing electrodes and the electrodes are crimped together.

  In addition, the content of the element in the particles containing palladium is calculated by, for example, cutting out a cross section of the conductive particle by an ultramicrotome method, observing it at a magnification of 250,000 times using a TEM, and component analysis by EDX attached to the TEM. be able to.

  Moreover, when the particle | grains containing palladium are formed by the above-mentioned reduction | restoration precipitation, so that palladium content may become the said range by the component analysis by EDX in the electroless palladium plating film obtained by the method of using the copper clad laminated board mentioned later. It is preferable to set conditions for reduction precipitation.

  In the conductive particle 2 according to the present embodiment, the protrusion 205 is formed by the second layer 202 containing nickel. Such a second layer can be formed by electroless nickel plating. In the present embodiment, by applying electroless nickel plating on the first layer 200 and palladium-containing grains 201, the second layer having protrusions 205 on the outer surface (surface opposite to the resin particle side). Can be formed.

  The second layer 202 containing nickel preferably has a nickel content of 93% by mass or more, more preferably 95 to 99% by mass, and still more preferably 96 to 98.5% by mass. . When the content of nickel is in the above range, when the second layer is formed by electroless nickel plating, aggregation of nickel particles can be easily suppressed, and formation of abnormal protrusions can be prevented. Thereby, when used as conductive particles blended in the anisotropic conductive adhesive, conductive particles that can achieve both low conduction resistance and high insulation reliability are easily obtained.

  The content of the element in the second layer is calculated by, for example, cutting out a cross section of the conductive particle by an ultramicrotome method, observing it at a magnification of 250,000 times using a TEM, and component analysis by EDX attached to the TEM. be able to.

  The average thickness of the second layer is preferably 10 to 200 nm, more preferably 20 to 160 nm, and still more preferably 40 to 130 nm. When the thickness of the second layer is within the above range, a protrusion having a good shape can be formed, and even when the conductive particles are highly compressed during the crimping connection, the metal layer is hardly cracked.

  The average thickness of the second layer is obtained by cutting the cross section of the obtained conductive particles so as to pass through the vicinity of the center of the particles by the ultramicrotome method and observing them at a magnification of 250,000 times using a TEM. From the obtained image, the cross-sectional area of the second layer can be estimated and calculated from the cross-sectional area. At this time, if it is difficult to distinguish between the first layer and the second layer, the distinction between the first layer and the second layer is made clear by component analysis by EDX, so that the second layer Only the average thickness can be calculated.

  The average height of the protrusions formed by the second layer is preferably 10 to 120 nm, more preferably 20 to 100 nm, and still more preferably 30 to 80 nm. When the average height of the protrusions is within the above range, conductive particles that can achieve both low conduction resistance and high insulation reliability when used as conductive particles blended in an anisotropic conductive adhesive are obtained. It becomes easy.

  The height of the protrusion refers to D4 shown in FIG. 3, and is the distance from the straight line connecting the valleys on both sides of the protrusion to the apex of the protrusion. Further, the average height D4 of the protrusions can be calculated as an average value of D4 in 10 conductive particles.

  In this embodiment, the protrusions formed by the second layer have a ratio of protrusions having a height of less than 30 nm of less than 80% with respect to the total number of protrusions, and a ratio of protrusions having a height of not less than 30 nm and less than 120 nm. The ratio of the number of protrusions with a height of 120 nm or more is preferably 5% or less with respect to the total number of protrusions, and the ratio of protrusions with a height of less than 30 nm is the total number of protrusions. On the other hand, the ratio of protrusions with a height of less than 60% and a height of 30 nm or more and less than 120 nm is 40 to 70% of the total number of protrusions, and the ratio of protrusions with a height of 120 nm or more is 2% or less with respect to the total number of protrusions. More preferably. Conductive particles having a projection height distribution within the above range, when used as conductive particles blended in an anisotropic conductive adhesive, achieve both low conduction resistance and high insulation reliability at a higher level. be able to.

  The protrusions formed by the second layer have a ratio of protrusions with an outer diameter of less than 100 nm less than 80% of the total number of protrusions, and a ratio of protrusions with an outer diameter of 100 nm to less than 200 nm in the total number of protrusions. The ratio of protrusions having an outer diameter of 200 nm or more is preferably 10% or less with respect to the total number of protrusions, and the ratio of protrusions having an outer diameter of less than 100 nm is less than 60% with respect to the total number of protrusions. More preferably, the ratio of protrusions having an outer diameter of 100 nm or more and less than 200 nm is 40 to 70% of the total number of protrusions, and the ratio of protrusions having an outer diameter of 200 nm or more is 5% or less of the total number of protrusions. preferable. Conductive particles having an outer diameter distribution of protrusions in the above range, when used as conductive particles blended in an anisotropic conductive adhesive, achieve both low conduction resistance and high insulation reliability at a higher level. be able to.

  The outer diameter of the protrusion refers to D5 shown in FIG. 3, and the protrusion existing in a concentric circle having a diameter that is ½ of the diameter of the conductive particle on the orthographic projection surface of the conductive particle. It means the average value of diameters calculated when the area of the contour is measured and the area is regarded as the area of a circle. Specifically, the conductive particles are observed at a magnification of 30,000 with an SEM, the outline of the protrusion is determined by image analysis based on the obtained SEM image, the area of each protrusion is calculated, and the protrusion is calculated from the average value. Can be obtained.

  Further, the number of protrusions is preferably in the range of 50 to 200 in a concentric circle having a diameter that is ½ of the diameter of the conductive particle on the orthographic projection surface of the conductive particle, and in the range of 70 to 170. More preferably, it is more preferably in the range of 90 to 150. In this case, even if the heights of all the protrusions are less than 50 nm, a sufficiently low electrical resistance value can be obtained when the electrodes are crimped together with conductive particles interposed between the opposing electrodes.

  In the conductive particles according to the present embodiment, the ratio (coverage) of the area of the protrusions formed by the second layer covering the outer surface of the conductive particles is preferably 60% or more, and 80% or more. More preferably, it is more preferably 90% or more. When the coverage is in the above range, even if the conductive particles are placed under high humidity, the electrical resistance value is unlikely to increase.

  The second layer preferably contains phosphorus or boron. Thereby, the hardness of the second layer can be increased, and the electrical resistance value when the conductive particles are compressed can be easily kept low. In addition, the second layer containing nickel may contain other metals that co-deposit together with phosphorus or boron. Examples of the other metal include metals such as cobalt, copper, zinc, iron, manganese, chromium, vanadium, molybdenum, palladium, tin, tungsten, and rhenium. By containing these metals in the second layer, the hardness of the second layer can be increased, and when the conductive particles are highly compressed and crimped and connected, the protrusions are prevented from being crushed, and the electric resistance is lower. A value can be obtained. Among other metals that co-deposit with phosphorus or boron, tungsten having high hardness is preferable. In this case, the nickel content in the second layer is preferably 85% by mass or more.

  When the second layer is formed by electroless nickel plating, for example, phosphorus can be co-deposited by using a phosphorus-containing compound such as sodium hypophosphite as a reducing agent, and a nickel-phosphorous alloy is included. A second layer can be formed. In addition, as a reducing agent, for example, boron can be co-deposited by using a boron-containing compound such as dimethylamine borane, sodium borohydride, potassium borohydride, and the like. A layer can be formed. Since the nickel-boron alloy has a higher hardness than the nickel-phosphorus alloy, when the conductive particles are highly compressed and crimped, the protrusions are suppressed from being crushed, and from the viewpoint of obtaining a lower electrical resistance value, the second The layer preferably comprises a nickel-boron alloy.

  In the present embodiment, it is preferable that the first layer includes a nickel-phosphorus alloy and the second layer includes a nickel-boron alloy. According to this combination, when the conductive particles are highly compressed and crimped, the metal layer can be prevented from cracking while suppressing the protrusions from being crushed, and a low electrical resistance value can be obtained more stably. it can.

  In the present embodiment, the first layer and the second layer are preferably formed by electroless nickel plating. The electroless nickel plating solution can contain a water-soluble nickel compound, and preferably further contains one or more compounds selected from a complexing agent, a reducing agent, a pH adjusting agent and a surfactant.

  Examples of the water-soluble nickel compound include water-soluble nickel inorganic salts such as nickel sulfate, nickel chloride and nickel hypophosphite, and water-soluble nickel organic salts such as nickel acetate and nickel malate. These water-soluble nickel compounds can be used individually by 1 type or in mixture of 2 or more types.

  The concentration of the water-soluble nickel compound is preferably 0.001 to 1 mol / L, and more preferably 0.01 to 0.3 mol / L. By making the density | concentration of a water-soluble nickel compound into the said range, it can suppress that the viscosity of a plating solution becomes high too much, obtaining the precipitation rate of a plating film, and can improve the uniformity of nickel precipitation.

  Examples of complexing agents include ethylenediaminetetraacetic acid, sodium (1-, 2-, 3- and 4-sodium) salts of ethylenediaminetetraacetic acid, ethylenediaminetriacetic acid, nitrotetraacetic acid and alkali salts thereof, glyconic acid, tartaric acid, and gluconate. , Citric acid, gluconic acid, succinic acid, pyrophosphoric acid, glycolic acid, lactic acid, malic acid, malonic acid, triethanolamine glucono (γ) -lactone may be used as long as they function as a complexing agent. However, it is not limited to these. Moreover, these complexing agents can be used individually by 1 type or in combination of 2 or more types.

  The concentration of the complexing agent varies depending on the type and is not particularly limited, but is usually preferably 0.001 to 2 mol / L, and more preferably 0.002 to 1 mol / L. By setting the concentration of the complexing agent within the above range, a sufficient deposition rate of the plating film can be obtained while suppressing precipitation of nickel hydroxide and decomposition of the plating solution in the plating solution, and the viscosity of the plating solution is high. It can suppress that it becomes too much and can improve the uniformity of nickel precipitation.

  As the reducing agent, a known reducing agent used in an electroless nickel plating solution can be used. For example, hypophosphite compounds such as sodium hypophosphite and potassium hypophosphite, sodium borohydride, hydrogen Examples thereof include borohydride compounds such as potassium borohydride and dimethylamine borane, and hydrazines.

  The concentration of the reducing agent varies depending on the type and is not particularly limited, but is usually preferably 0.001 to 1 mol / L, and more preferably 0.002 to 0.5 mol / L. By setting the concentration of the reducing agent within the above range, decomposition of the plating solution can be suppressed while sufficiently obtaining a reduction rate of nickel ions in the plating solution.

  Among pH adjusters, acidic pH adjusters include, for example, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, formic acid, cupric chloride, ferric sulfate and other iron compounds, alkali metal chlorides, ammonium persulfate Or an aqueous solution containing one or more of these, or an aqueous solution containing acidic hexavalent chromium such as chromic acid, chromic acid-sulfuric acid, chromic acid-hydrofluoric acid, dichromic acid, and dichromic acid-borofluoric acid. Moreover, as an alkaline pH adjuster, it contains amino groups such as alkali metal or alkaline earth metal hydroxides such as sodium hydroxide, potassium hydroxide and sodium carbonate, ethylenediamine, methylamine and 2-aminoethanol. Examples include a solution containing one or more compounds.

  As the surfactant, for example, a cationic surfactant, an anionic surfactant, an amphoteric surfactant, a nonionic surfactant, or a mixture thereof can be used.

  In the conductive particles of the present embodiment, the metal layer may further contain a third layer containing palladium on the opposite side of the second layer from the first layer.

  The layer containing palladium can function as an anti-oxidation layer for nickel. Therefore, the third layer is preferably provided on the second layer. Further, the thickness of the third layer is preferably 5 to 100 nm, and more preferably 10 to 30 nm. When the thickness of the third layer is within the above range, the uniformity of the layer can be improved when the third layer is formed by plating or the like, and the nickel contained in the second layer contains the third containing palladium. The layer can effectively function as a layer that prevents diffusion to the surface opposite to the second layer.

  The third layer can be formed by, for example, palladium plating, and is preferably a palladium layer formed by electroless palladium plating. For electroless palladium plating, either a substitution type that does not use a reducing agent or a reduction type that uses a reducing agent may be used. As such an electroless palladium plating solution, there are MCA (trade name, manufactured by World Metal Co., Ltd.), etc., for the replacement type, and APP (trade name, manufactured by Ishihara Pharmaceutical Co., Ltd.), etc., for the reduction type. When the substitution type and the reduction type are compared, the reduction type is preferable in that there are few voids and it is easy to ensure the covering area.

  In the conductive particles of the present embodiment, the metal layer may further contain a fourth layer containing gold on the opposite side of the second layer from the first layer.

  The layer containing gold can lower the electric resistance value on the surface of the conductive particles and further improve the properties of the conductive particles. From such a viewpoint, the fourth layer is preferably the outermost layer of the metal layer. The thickness of the fourth layer in this case is preferably 30 nm or less from the viewpoint of the balance between the effect of reducing the electrical resistance value on the surface of the conductive particles and the manufacturing cost, but even if it is 30 nm or more, the characteristics are high. no problem. In addition, when the function of nickel as an antioxidant layer is expected, the fourth layer is preferably provided on the second layer. In this case, the thickness of the fourth layer is preferably 10 nm to 100 nm.

  The fourth layer can be formed by, for example, gold plating. Examples of the gold plating solution include substitution type gold plating solutions such as HGS-100 (manufactured by Hitachi Chemical Co., Ltd., trade name), reduction type gold plating solutions such as HGS-2000 (product name of Hitachi Chemical Co., Ltd.), and the like. Can be used. When the substitution type and the reduction type are compared, the reduction type is preferable in that there are few voids and it is easy to ensure the covering area.

  The conductive particles according to the present embodiment preferably have an average particle size of 1 to 10 μm, and more preferably 2 to 5 μm. By setting the average particle diameter of the conductive particles in the above range, when a connection structure is produced using an anisotropic conductive adhesive containing conductive particles, the conductive particles are hardly affected by variations in electrode height. The average particle diameter of the conductive particles in the present embodiment can be obtained by measuring the particle diameter of 300 arbitrary conductive particles by observation using an SEM and taking the average value thereof. Since the conductive particles according to this embodiment have protrusions, the particle diameter of the conductive particles is the diameter of a circle circumscribing the conductive particles in the SEM image.

<Method for producing conductive particles>
The method for producing conductive particles of the present embodiment includes (1) a step of forming a first layer containing nickel on the surface of resin particles by electroless nickel plating, and (2) palladium on the first layer. A step of forming particles containing palladium by reduction deposition of an electroless palladium plating solution containing ions and a reducing agent; and (3) nickel is electrolessly plated on the first layer and the particles containing palladium. Forming a second layer including.

  According to the above manufacturing method, the number, size, and shape of the protrusions formed by the second nickel layer can be highly controlled, and the conductive particles can achieve both low conduction resistance and high insulation reliability. Can be obtained.

  The present inventors infer the reason why the above conductive particles can be obtained by the method according to this embodiment. When particles in which particles containing palladium are formed on the first layer are immersed in an electroless nickel plating solution for forming the second layer, the reducing agent contained in the plating solution is more than on the first layer. It is considered that electrons are preferentially oxidized on the particles containing palladium to emit electrons. As a result, nickel preferentially precipitates on the particles containing palladium over the first layer, and after nickel precipitates in a protruding shape on the particles containing palladium, the particles containing palladium on the first layer It is thought that nickel deposition occurs in the non-existing portion. As described above, the present inventors have made it possible to form a second layer having protrusions with small variation in shape by providing a time difference at which nickel deposition starts on the first layer. I guess.

  Note that the conventional palladium catalyst treatment described above cannot form protrusions on the second layer. The reason may be that the palladium catalyst nucleus is small. That is, the palladium catalyst treatment includes (1) sensitization treatment with tin ions, (2) activation treatment for trapping palladium ions in a solution containing an aqueous palladium chloride solution, and (3) palladium adsorbed on the surface by a reducing agent. Although it consists of reduction treatments for reducing and precipitating ions, these treatments are merely reducing palladium ions adsorbed on the surface, so the palladium catalyst nucleus is considered to be at the atomic level. In the method according to the present embodiment, it is possible to obtain particles containing palladium having a sufficient size by continuously depositing palladium ions in the electroless palladium plating solution with a reducing agent. It is possible to form the second layer having a protrusion with a small variation in shape.

  For the resin particles, electroless palladium plating solution, and electroless nickel plating used in the method according to the present embodiment, those listed in the description of the conductive particles of the present embodiment can be used. In the method according to the present embodiment, the resin particles are preferably subjected to a palladium catalyst treatment from the viewpoint of improving the uniformity of the first layer containing nickel. The palladium catalyst treatment at this time can use the treatments described in the description of the conductive particles of the present embodiment.

  In the method according to the present embodiment, the palladium-containing particles are preferably precipitated so that the length in the thickness direction of the first layer is 4 nm or more. The length can be adjusted by changing the nickel purity in the first nickel layer. For example, the first layer contains phosphorus, but when the content of phosphorus is increased to lower the purity of nickel, the grains containing palladium are more likely to grow in the thickness direction. Therefore, the content of nickel in the first layer is preferably 83 to 98 mass%, more preferably 85 to 93 mass%, in that the length of the particles containing palladium can be sufficiently increased, and 86 More preferably, it is -91 mass%. Further, the palladium content in the particles containing palladium is preferably 94% by mass or more in that the purity of the particles containing palladium can be increased as the purity of the palladium is increased. More preferably, it is at least 99% by mass, and even more preferably at least 99% by mass.

  In the method according to the present embodiment, it is preferable that the particles containing palladium are precipitated so as to be scattered in a direction perpendicular to the thickness direction of the first layer. The distribution of the particles containing palladium can be adjusted by changing the nickel purity in the first nickel layer. Although the first layer contains phosphorus, as in the growth in the thickness direction of the grains containing palladium, the grains containing palladium are distributed when the content of phosphorus is increased to lower the purity of nickel. It becomes easy. Therefore, the content of nickel in the first layer is preferably 83 to 98% by mass, more preferably 85 to 93% by mass, and more preferably 86 to 91% from the viewpoint of suppressing variation in the shape of the particles containing palladium. More preferably, it is mass%. Moreover, since it becomes possible to suppress variation in the shape of particles containing palladium as the purity of palladium is increased, the content of palladium in the particles containing palladium is preferably 94% by mass or more, More preferably, it is 97 mass% or more, and it is especially preferable that it is 99 mass% or more. Moreover, since the diameter of the particle | grains containing palladium can be enlarged, so that the purity of palladium is highly purified as mentioned above, if content of palladium in the particle | grains containing palladium is in the said range, for example, diameter 20nm The number of particles containing less than palladium can be reduced, and the shape variation of particles containing palladium having a diameter of 20 nm or more and less than 60 nm can be suppressed.

  According to the method for producing conductive particles of this embodiment, the conductive particles of this embodiment can be obtained. In the method for producing conductive particles of the present embodiment, it is preferable to perform the above steps so as to satisfy one or more conditions for the conductive particles of the present embodiment described above.

<Insulation coated conductive particles>
Next, the insulating coated conductive particles of this embodiment will be described. The insulating coated conductive particle 10 shown in FIG. 1B includes the conductive particle 2 of the present embodiment and the insulating child particle 1 that covers at least a part of the surface of the metal layer 204 of the conductive particle 2.

  In recent years, anisotropic conductive adhesives for COG mounting are required to have insulation reliability at a narrow pitch of 10 μm level. In order to further improve the insulation reliability, it is preferable to insulate the conductive particles. According to the insulating coated conductive particles of the present embodiment, such required characteristics can be effectively realized.

  Examples of the insulator particles covering the conductive particles include organic polymer compound fine particles and inorganic oxide fine particles. Among these, inorganic oxide fine particles are preferable from the viewpoint of insulation reliability. In the case of organic polymer compound fine particles, it is easy to lower the electrical resistance value.

  As the organic polymer compound, those having heat softening properties are preferable, for example, polyethylene, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester copolymer. , Polyester, polyamide, polyurethane, polystyrene, styrene-divinylbenzene copolymer, styrene-isobutylene copolymer, styrene-butadiene copolymer, styrene- (meth) acrylic copolymer, ethylene-propylene copolymer, (meta ) Acrylic acid ester rubber, styrene-ethylene-butylene copolymer, phenoxy resin, and solid epoxy resin are preferably used. These may be used individually by 1 type and may be used in combination of 2 or more type.

As the inorganic oxide, for example, an oxide containing at least one element selected from the group consisting of silicon, aluminum, zirconium, titanium, niobium, zinc, tin, cerium and magnesium is preferable, and these may be used alone or in combination. Two or more types can be mixed and used. Among the inorganic oxide fine particles, water-dispersed colloidal silica (SiO ₂ ) is particularly preferable because it is excellent in binding properties with conductive particles having a hydroxyl group on the surface, easily adjusts the particle diameter, and is inexpensive. Examples of such commercially available inorganic oxide fine particles include Snowtex, Snowtex UP (trade name, manufactured by Nissan Chemical Industries, Ltd.), and Quatron PL series (trade name, manufactured by Fuso Chemical Industries, Ltd.). .

  When the inorganic oxide fine particles have a hydroxyl group on the surface, the hydroxyl group can be modified to an amino group, a carboxyl group, an epoxy group, etc. with a silane coupling agent or the like. In the case of 500 nm or less, modification may be difficult. In that case, it is desirable to coat the conductive particles without modification.

  In general, by having a hydroxyl group, it can be bonded to a hydroxyl group, a carboxyl group, an alkoxyl group, an alkoxycarbonyl group, or the like. Examples of the bonding form include a covalent bond by dehydration condensation, a hydrogen bond, and a coordination bond.

  When the outermost surface of the conductive particles is made of gold or palladium, a hydroxyl group, a carboxyl group, an alkoxyl group is formed on the surface using a compound having a mercapto group, sulfide group, disulfide group, etc. in the molecule that forms a coordinate bond with them. And a functional group such as an alkoxycarbonyl group. Examples of the compound include mercaptoacetic acid, 2-mercaptoethanol, methyl mercaptoacetate, mercaptosuccinic acid, thioglycerin, and cysteine.

  Precious metals such as gold, palladium, and copper easily react with thiol, and base metals such as nickel hardly react with thiol. Therefore, when the outermost layer of the conductive particles is made of a noble metal, it reacts more easily with thiol than when the outermost layer of the conductive particles is made of a base metal.

  For example, the method for treating the above compound on the gold surface is not particularly limited, but the above compound such as mercaptoacetic acid is dispersed in an organic solvent such as methanol or ethanol in an amount of about 10 to 100 mmol / L, and the outermost layer is formed therein. Conductive particles that are gold can be dispersed.

  The average particle diameter of the insulator particles is preferably 20 to 500 nm. The average particle diameter of the insulator particles is measured by, for example, a specific surface area conversion method by the BET method or a small-angle X-ray scattering method. When the average particle size is in the above range, for example, when inorganic oxide fine particles are used as the insulator particles, the inorganic oxide fine particles adsorbed on the conductive particles are likely to act effectively as an insulating film, and the connection is increased. The conductivity in the pressure direction tends to be good.

  From the viewpoint of easily reducing the electrical resistance and suppressing the increase in electrical resistance over time, the average particle size of the insulator particles is preferably 1/10 or less of the average particle size of the conductive particles. / 15 or less is more preferable. Further, from the viewpoint of obtaining better insulation reliability, the average particle diameter of the insulator particles is preferably 1/20 or more than the average particle diameter of the conductive particles.

  The insulator particles preferably cover the surface of the conductive particles so that the coverage is 20 to 70%. From the viewpoint of obtaining the effects of insulation and conductivity more reliably, the coverage is more preferably 20 to 60%, further preferably 25 to 60%, and particularly preferably 28 to 55%. In addition, the coverage here means the ratio of the surface area of the insulator particles in the concentric circles having a diameter of ½ of the diameter of the conductive particles on the orthographic projection surface of the conductive particles, and specifically, by SEM Conductive particles are observed at a magnification of 30,000, and based on the obtained SEM image, the ratio of the insulator particles on the surface of the conductive particles is calculated by image analysis.

  Next, as a method of coating the surface of the conductive particles with inorganic oxide fine particles, for example, a method of alternately laminating polymer electrolytes and inorganic oxide fine particles is preferable. More specifically, (1) a step of dispersing conductive particles in a polymer electrolyte solution, adsorbing the polymer electrolyte on the surface of the conductive particles, and then rinsing, (2) dispersing the conductive particles with inorganic oxide fine particles The surface was coated with the insulator particles in which the polymer electrolyte and the inorganic oxide fine particles were laminated by a manufacturing method including a step of rinsing after the inorganic fine particles were adsorbed on the surface of the conductive particles after being dispersed in the solution. Insulating coated conductive particles can be produced. Such a method is called an alternating lamination method (Layer-by-Layer assembly). The alternate lamination method is described in G.H. This is a method of forming an organic thin film published in 1992 by Decher et al. (Thin Solid Films, 210/211, p831 (1992)). According to this method, a polycation adsorbed on a substrate by electrostatic attraction is alternately immersed in an aqueous solution of a polymer electrolyte having a positive charge (polycation) and a polymer electrolyte having a negative charge (polyanion). A composite film (alternate laminated film) is obtained by laminating a set of polyanions. The steps (1) and (2) may be in the order of (1) and (2), or in the order of (2) and (1).

  In the alternating layering method, the film is grown by attracting the charge of the material formed on the substrate and the material having the opposite charge in the solution by electrostatic attraction, so that the adsorption proceeds and the charge is neutralized. When this occurs, no further adsorption occurs. Therefore, when reaching a certain saturation point, the film thickness does not increase any more. Lvov et al. Reported on a method of applying an alternate lamination method to fine particles and laminating a polymer electrolyte having a charge opposite to the surface charge of the fine particles using each fine particle dispersion such as silica, titania, and ceria. (Langmuir, Vol. 13, (1997) p6195-6203). By using this method, silica fine particles having a negative surface charge and polydiallyldimethylammonium chloride (PDDA) or polyethyleneimine (PEI), which are polycations having the opposite charge, are alternately laminated to form silica. It is possible to form a fine particle laminated thin film in which fine particles and a polymer electrolyte are alternately laminated.

  As the polymer electrolyte, for example, a polymer that is ionized in an aqueous solution and has a charged functional group in the main chain or side chain can be used. Specifically, it is preferable to use a polycation. Examples of the polycation include those having a positively charged functional group such as polyamines such as polyethyleneimine (PEI), polyallylamine hydrochloride (PAH), polydiallyldimethylammonium chloride (PDDA), polyvinyl Pyridine (PVP), polylysine, polyacrylamide, or a copolymer containing one or more of these can be used. Among these, polyethyleneimine is preferable because it has a high charge density and a strong binding force.

<Anisotropic conductive adhesive>
The anisotropic conductive adhesive of this embodiment contains the above-described conductive particles of this embodiment, the conductive particles obtained by the production method of this embodiment, or the insulating coated conductive particles of this embodiment, and the adhesive. . It is preferable to use this anisotropic conductive adhesive as an anisotropic conductive adhesive film formed into a film. The thickness of the anisotropic conductive adhesive film of the present embodiment is not particularly limited, but is preferably 5 to 50 μm, more preferably 7 to 40 μm, and still more preferably 10 to 30 μm.

  As the adhesive, for example, a mixture of a heat-reactive resin and a curing agent is used. Examples of the adhesive preferably used include a mixture of an epoxy resin and a latent curing agent, and a mixture of a radical polymerizable compound and an organic peroxide.

  Also, a paste or film is used as the adhesive. In order to form a film, it is effective to add a thermoplastic resin such as a phenoxy resin, a polyester resin, a polyamide resin, a polyester resin, a polyurethane resin, an acrylic resin, or a polyester urethane resin to the adhesive.

<Connection structure>
Next, a connection structure using the anisotropic conductive adhesive of this embodiment will be described with reference to FIG. FIG. 4 is a schematic cross-sectional view showing the connection structure according to the present embodiment. The connection structure 100 shown in FIG. 4 includes a first circuit member 30 and a second circuit member 40 that face each other, and the first circuit member 30 and the second circuit member 40 are disposed between the first circuit member 30 and the second circuit member 40. A connecting portion 50a for connecting them is provided.

  The first circuit member 30 includes a circuit board (first circuit board) 31 and a circuit electrode (first circuit electrode) 32 formed on the main surface 31 a of the circuit board 31. The second circuit member 40 includes a circuit board (second circuit board) 41 and a circuit electrode (second circuit electrode) 42 formed on the main surface 41 a of the circuit board 41.

  Specific examples of the circuit member include a chip component such as an IC chip (semiconductor chip), a resistor chip, a capacitor chip, and a driver IC, and a rigid package substrate. These circuit members are provided with circuit electrodes, and generally have many circuit electrodes. Specific examples of the other circuit member to which the circuit member is connected include a flexible tape substrate having metal wiring, a flexible printed wiring board, and a wiring substrate such as a glass substrate on which indium tin oxide (ITO) is deposited. Can be mentioned. According to the film-like anisotropic conductive adhesive 50, these circuit members can be connected efficiently and with high connection reliability. The anisotropic conductive adhesive of this embodiment is suitable for COG mounting or COF mounting on a wiring board of a chip component having many fine circuit electrodes.

  The connecting portion 50a includes a cured product 20a of an adhesive and the insulating coated conductive particles 10 dispersed therein. And in the connection structure 100, the circuit electrode 32 and the circuit electrode 42 which oppose are electrically connected through the insulation coating electrically-conductive particle 10. FIG. More specifically, as shown in FIG. 4, in the insulating coated conductive particles 10, the conductive particles 2 are deformed by compression and are electrically connected to both the circuit electrodes 32 and 42. On the other hand, in the illustrated horizontal direction, insulation is maintained by the presence of the insulator particles 1 between the conductive particles 2. Therefore, if the anisotropic conductive adhesive of this embodiment is used, it is possible to improve the insulation reliability at a narrow pitch of 10 μm level. Further, depending on the application, it is also possible to use conductive particles that are not covered with insulation instead of insulating coated conductive particles.

  The connection structure 100 of this embodiment includes a first circuit member 30 having a first circuit electrode 32 and a second circuit member 40 having a second circuit electrode 42, and the first circuit electrode 32 and the second circuit member 40. The second circuit electrode 42 is disposed so as to face each other, and the anisotropic conductive adhesive of the present embodiment is interposed between the first circuit member 30 and the second circuit member 40, and heated and pressurized. Thus, the first circuit electrode 32 and the second circuit electrode 42 are electrically connected. The 1st circuit member 30 and the 2nd circuit member 40 are adhere | attached by the hardened | cured material 20a of the anisotropic conductive adhesive of this embodiment.

<Method for manufacturing connection structure>
A method for manufacturing the connection structure will be described with reference to FIG. FIG. 5 is a schematic cross-sectional view for explaining an example of the manufacturing method of the connection structure shown in FIG. In the present embodiment, the anisotropic conductive adhesive is thermoset to produce a connection structure.

  First, the first circuit member 30 described above and an anisotropic conductive adhesive 50 (anisotropic conductive adhesive film) formed into a film shape are prepared. The film-like anisotropic conductive adhesive 50 contains the insulating coated conductive particles 10 in the insulating adhesive 20 as described above.

  Next, the film-like anisotropic conductive adhesive 50 is placed on the surface of the first circuit member 30 on which the circuit electrodes 32 are formed. Then, the film-like anisotropic conductive adhesive 50 is pressurized in the directions of arrows A and B in FIG. 5A, and the film-like anisotropic conductive adhesive 50 is laminated on the first circuit member 30 ( FIG. 5B).

  Next, as shown in FIG. 5C, the second circuit member 40 is formed into a film-like anisotropic conductive adhesive so that the first circuit electrode 32 and the second circuit electrode 42 face each other. 50. Then, while the film-like anisotropic conductive adhesive 50 is heated, the whole is pressurized in the directions of arrows A and B in FIG.

  The connection portion 50a is formed by curing the film-like anisotropic conductive adhesive 50, and the connection structure 100 as shown in FIG. 4 is obtained. In the present embodiment, the anisotropic conductive adhesive 50 is a film, but may be a paste.

  Examples of the connection structure having the above connection structure include portable products such as a liquid crystal display, a personal computer, a mobile phone, a smartphone, and a tablet.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  Hereinafter, the contents of the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited to the following Example.

<Example 1>
[Preparation of conductive particles]
(Step a) Pretreatment step 2 g of crosslinked polystyrene particles having an average particle size of 3.0 μm (trade name “Soliostar” manufactured by Nippon Shokubai Co., Ltd.) and Atotech Neogant 834 (manufactured by Atotech Japan Co., Ltd., product) Was added to 100 mL of a palladium-catalyzed solution containing 8% by mass, stirred at 30 ° C. for 30 minutes, filtered through a 3 μm membrane filter (manufactured by Merck), and washed with water to obtain resin particles. Thereafter, the resin particles were added to a 0.5 mass% dimethylamine borane solution adjusted to pH 6.0 to obtain resin particles whose surface was activated. Then, the resin particle dispersion liquid was obtained by immersing the resin particle in which the surface was activated in 20 mL distilled water, and carrying out ultrasonic dispersion | distribution.

(Step b) Formation of first layer The resin particle dispersion obtained above is diluted with 1000 mL of water heated at 80 ° C., 1 mL of 1 g / L bismuth nitrate aqueous solution is added as a plating stabilizer, and resin particles are added. To a dispersion containing 2 g, 80 mL of an electroless nickel plating solution for forming a first layer having the following composition was dropped at a dropping rate of 5 mL / min. After 10 minutes had elapsed after completion of the dropping, the dispersion with the plating solution added was filtered, and the filtrate was washed with water and then dried with a vacuum dryer at 80 ° C. Thus, the 1st layer which consists of a nickel-phosphorus alloy film with a film thickness of 80 nm shown in Table 1 was formed. In addition, the particle | grains obtained by forming a 1st layer were 4g.
(Electroless nickel plating solution for first layer formation)
Nickel sulfate ... 400g / L
Sodium hypophosphite ... 150g / L
Sodium citrate ... 120g / L
Bismuth nitrate aqueous solution (1 g / L) ... 1 mL / L

(Step c) Formation of particles containing palladium Next, 4 g of the particles forming the first layer were immersed in 1 L of electroless palladium plating solution having the following composition to form particles containing palladium on the surface of the particles. . The reaction time was 10 minutes and the temperature was 60 ° C.
(Electroless palladium plating solution)
Palladium chloride: 0.07g / L
Ethylenediamine ... 0.05g / L
Sodium formate …… 0.2g / L
Tartaric acid ... 0.11 g / L
pH ... 7

(Step d) Formation of second layer 4.05 g of the particles obtained in step c were washed with water and filtered, and then dispersed in 1000 mL of water heated to 70 ° C. To this dispersion, 1 mL of a 1 g / L bismuth nitrate aqueous solution as a plating stabilizer was added, and then 50 mL of a second layer forming electroless nickel plating solution having the following composition was added dropwise at a dropping rate of 5 mL / min. After 10 minutes had elapsed after completion of the dropping, the dispersion with the plating solution added was filtered, and the filtrate was washed with water and then dried with a vacuum dryer at 80 ° C. In this way, a second layer made of a nickel-phosphorus alloy film having a thickness of 80 nm shown in Table 1 was formed. In addition, the particle | grains obtained by forming a 2nd layer were 6g.
(Electroless nickel plating solution for second layer formation)
Nickel sulfate ... 400g / L
Sodium hypophosphite ... 150g / L
Sodium tartrate dihydrate ... 120g / L
Bismuth nitrate aqueous solution (1 g / L) ... 1 mL / L

  Conductive particles were obtained by the above steps a to d.

[Evaluation of conductive particles]
(Evaluation of film thickness and components)
About the obtained electroconductive particle, a cross section is cut out by the ultra microtome method so that it may pass near the center of particle | grains, and a transmission electron microscope apparatus (henceforth, TEM apparatus, the JEOL Co., Ltd. make, brand name "JEM-2100F") is used. The cross-sectional areas of the first and second layers were estimated from the obtained images, and the film thicknesses of the first and second layers were calculated from the cross-sectional areas. Table 1 shows average values of film thicknesses calculated for 10 conductive particles. At this time, when it is difficult to distinguish between the first layer and the second layer, an energy dispersive X-ray detector (hereinafter, EDX detector, manufactured by JEOL Ltd., trade name “JED-2300”) By clarifying the distinction between the first layer and the second layer by component analysis according to the above, the cross-sectional area of each layer was estimated and the film thickness was measured. The results are shown in Table 1.

(Evaluation of grains containing palladium)
For the particles after forming the palladium-containing particles in the above step c, the number of particles containing palladium existing in a concentric circle having a diameter ½ of the diameter of the particles and the ratio of the particles having a predetermined diameter are calculated. did.

  Specifically, the number of particles containing palladium was evaluated based on an SEM image obtained by observing the particles with a scanning electron microscope (hereinafter, SEM apparatus, manufactured by Hitachi High-Technologies Corporation) at a magnification of 30,000. In FIG. 6, the SEM image which observed the surface of the particle | grains after forming the particle | grains containing the palladium obtained at the process c is shown.

  As a ratio of the grains containing palladium having a predetermined diameter, the diameter is less than 20 nm, more than 20 nm and less than 60 nm, and more than 60 nm with respect to the total number of grains containing palladium existing in a concentric circle having a diameter that is ½ of the diameter of the particles. The ratio of the number of grains containing palladium was determined. In addition, about the diameter of the particle | grains containing palladium, as shown in FIG. 7, it discriminate | determined by the SEM image observed by 150,000 times.

  The average length in the thickness direction of the metal layer of the particle | grains containing palladium was calculated | required with the following procedures. First, the cross section of the particle was cut out using the ultramicrotome method, and the sample with the largest particle diameter among the cut out samples was taken as a sample cut out with a cross section passing through the vicinity of the center of the particle. This sample was observed at an acceleration voltage of 200 kV using a TEM apparatus and utilizing a scanning transmission electron microscope mode (STEM mode) which is one of the measurement modes of the TEM apparatus. Next, the field of view was searched while observing in the STEM mode, and a mapping diagram of nickel, phosphorus, and palladium was obtained by the EDX detector attached to the TEM device (in this way, the observation was made in the STEM mode and analyzed by the EDX detector). This method is hereinafter abbreviated as “STEM / EDX analysis”). FIG. 9 shows a STEM image of the cross section of the particle and the corresponding mapping diagram of nickel, phosphorus and palladium. Then, the length in the thickness direction of the metal layer of the particle | grains containing palladium was calculated | required from the mapping figure of the obtained palladium. FIG. 10 is a diagram for explaining a method for obtaining the length in the thickness direction of the metal layer of particles containing palladium from the mapping diagram of palladium in FIG. 9. Moreover, the length in the thickness direction of a metal layer was calculated | required about ten grains containing palladium, and those average values were made into the average length of the grain containing palladium. Hereinafter, details of a method for producing a cross-sectional sample of conductive particles and a mapping method using an EDX detector will be described.

(Method for producing cross-sectional sample of conductive particles)
A cross-sectional sample having a thickness of 60 nm ± 20 nm for conducting STEM / EDX analysis of the conductive particles from the cross-sectional direction (hereinafter referred to as “thin film slice for TEM measurement”) was prepared using an ultramicrotome method. The manufacturing method is shown below.

  In order to stably process the thin film, the conductive particles were dispersed in the casting resin. Specifically, 10 g of a mixture of bisphenol A type liquid epoxy resin, butyl glycidyl ether and other epoxy resin (Refinetech Co., Ltd., trade name “Epomount Main Agent 27-771”) is mixed with diethylenetriamine (Refinetech Co., Ltd., 1.0 g of product name “Epomount Curing Agent 27-772”) was mixed, stirred with a spatula, and visually confirmed to be uniformly mixed. After adding 0.5 g of dried conductive particles to 3 g of this mixture and stirring until uniform using a spatula, this is added to a resin casting mold (DSK Dosaka EM Co., Ltd., product Name “silicone-embedded plate type II”) and allowed to stand at room temperature for 24 hours. After confirming that the casting resin was solidified, a resin casting of conductive particles was obtained.

  Using an ultramicrotome (trade name “EM-UC6” manufactured by Leica Microsystems, Inc.), a thin film slice for TEM measurement was prepared from a resin casting of conductive particles. When preparing a thin film slice for TEM measurement, first, a glass knife (manufactured by a glass knife maker manufactured by Nissin EM Co., Ltd.) fixed to the main body of the ultramicrotome is used, as shown in FIG. ), The tip of the resin casting was trimmed until a shape capable of cutting out a thin film slice for TEM measurement was obtained.

  More specifically, as shown in FIG. 11 (b), trimming was performed so that the cross-sectional shape of the tip of the resin casting was a substantially rectangular parallelepiped shape having a length of 200 to 400 μm and a width of 100 to 200 μm. The reason why the lateral length of the cross section is set to 100 to 200 μm is to reduce friction generated between the diamond knife and the sample when a thin film section for TEM measurement is cut out from the resin casting. It becomes easy to prevent wrinkling and bending of the thin film slice for TEM measurement, and it becomes easy to produce the thin film slice for TEM measurement.

  Subsequently, a diamond knife with a boat (made by DIATONE, trade name “Cryo Wet”, blade width 2.0 mm, blade angle 35 °) is fixed to a predetermined portion of the main body of the ultramicrotome device, and the boat is ion-exchanged water. The blade was wet with ion-exchanged water by adjusting the knife installation angle.

  Here, adjustment of the installation angle of the knife will be described with reference to FIG. In adjusting the installation angle of the knife, the vertical angle, the horizontal angle, and the clearance angle can be adjusted. Adjustment of the angle in the vertical direction means adjusting the vertical angle of the sample holder so that the sample surface and the direction in which the knife proceeds are parallel to each other, as shown in FIG. Further, the adjustment of the angle in the left-right direction means adjusting the angle in the left-right direction of the knife so that the blade edge of the knife and the sample surface are parallel to each other, as shown in FIG. Further, the adjustment of the clearance angle means that the minimum angle formed by the sample side surface of the knife edge and the direction in which the knife advances is adjusted as shown in FIG. The clearance angle is preferably 5 to 10 °. When the clearance angle is in the above range, friction between the blade edge of the knife and the sample surface can be reduced, and the knife can be prevented from rubbing the sample surface after the thin film slice is cut out from the sample.

  While confirming the optical microscope attached to the main body of the ultramicrotome device, the distance between the sample and the diamond knife is reduced, the blade speed is 0.3 mm / second, and the cutting thickness of the thin film is 60 nm ± 20 nm. After setting a set value and cutting out a thin film slice from the resin casting, a thin film slice for TEM measurement was floated on the surface of ion-exchanged water. From the upper surface of the thin film slice for TEM measurement floating on the water surface, a copper mesh for TEM measurement (made by Nissin EM Co., Ltd., trade name "copper mesh with microgrid") is pressed, and the thin film slice for TEM measurement is copper mesh To make a TEM sample. Note that the thin film slice for TEM measurement obtained by the microtome does not exactly match the set value of the cut-out thickness of the microtome, so that a set value for obtaining a desired thickness is obtained in advance.

(Mapping method using EDX detector)
The “thin film slice for TEM measurement” was fixed together with a copper mesh on a sample holder (trade name “Berilium sample biaxial tilt holder, EM-31640” manufactured by JEOL Ltd.) and inserted into the TEM apparatus. After starting the electron beam irradiation to the sample at an acceleration voltage of 200 kV, the electron beam irradiation system was switched to the STEM mode.

  Insert the scanning image observation device into the STEM observation position, start the STEM observation software “JEOL Simple Image Viewer (Version 1.3.5)” (manufactured by JEOL Ltd.), The thin-film slices of the film were observed, and a portion suitable for EDX measurement was searched out of the cross-section of the conductive particles observed therein. The location suitable for the measurement here means a location where the cross section of the metal layer can be observed by cutting near the center of the conductive particle, a location where the cross section is inclined, or a location shifted from the vicinity of the center of the conductive particle. The part cut | disconnected by (1) was excluded from the measuring object. At the time of photographing, the observation magnification was 250,000 times, and the number of pixels of the STEM observation image was 512 points vertically and 512 points horizontally. Observation under these conditions gives an observation image with a viewing angle of 600 nm. However, care should be taken because the viewing angle may change even at the same magnification as the apparatus changes.

  In the STEM / EDX analysis, if an electron beam is applied to the “TEM measurement thin film slice” of the conductive particles, the plastic core of the conductive particles or the casting resin contracts or expands, and the sample is removed during the measurement. It will be deformed or moved. In order to suppress sample deformation and sample movement during EDX measurement, the measurement location was irradiated with an electron beam for about 30 minutes to 1 hour in advance, and analysis was performed after confirming that the deformation and movement had subsided.

  In order to perform STEM / EDX analysis, the EDX detector was moved to the measurement position, and EDX measurement software “Analysis Station” (manufactured by JEOL Ltd.) was started. At the time of mapping by the EDX detector, it is necessary to obtain a sufficient resolution at the time of mapping. Therefore, a focusing diaphragm device for focusing an electron beam at a target location is used.

  In the STEM / EDX analysis, the spot diameter of the electron beam is in the range of 0.5 nm to 1.0 nm so that the number of detected characteristic X-rays (CPS: Counts Per Second) is 10,000 CPS or more. Adjusted. In addition, after the measurement, in the EDX spectrum obtained simultaneously with the mapping measurement, it was confirmed that the peak height derived from the Kα ray of nickel was at least 5,000 Counts or more. Further, at the time of data acquisition, the number of pixels was set to 256 points in the vertical direction and 256 points in the horizontal direction with the same viewing angle as that in the STEM observation. Moreover, the integration time for each point was set to 20 milliseconds, and the measurement was performed once.

  In order to calculate the length D1 of the grains containing palladium, a mapping image of palladium was created based on the obtained STEM / EDX analysis data. In this mapping image of palladium, as shown in FIG. 10, the obtained mapping image is binarized into black and white to determine the boundary line between the portion where palladium is present and the portion where palladium is not present, and the thickness direction of the metal layer The distance between the boundary lines at D1 was D1. However, the measurement data contains noise, and filtering was performed to improve the S / N ratio. The filtering process is a function attached to the software “Analysis Station” for EDX measurement, and at each measurement point, in addition to the data of each measurement point, the data of a plurality of points adjacent to the measurement point can be integrated and displayed. it can. Thereby, since S / N of a mapping image improves, the length D1 of the particle | grains containing palladium can be calculated from the mapping image of palladium. In this embodiment, using this filter processing, in addition to the data of each measurement point, data of 8 points (up, down, left, right, upper left, lower left, upper right, lower right) adjacent to the measurement point are integrated. And after reducing the noise of a mapping image, the length D1 of the grain containing palladium was computed.

  From the obtained EDX mapping data, EDX spectra in the first layer and the second layer were extracted as necessary, and the element abundance ratio in each layer was calculated. However, when calculating the quantitative value, the total concentration of palladium, nickel, and phosphorus was set to 100%, and the mass% concentration of each element was calculated.

  The elements other than the above were excluded when calculating the quantitative values because the ratios were likely to fluctuate for the following reasons. The ratio of carbon increases / decreases due to the influence of contamination that is adsorbed on the sample surface when irradiated with an electron beam or the carbon support film used in the mesh for TEM measurement. Oxygen may increase due to air oxidation between preparation of the TEM sample and measurement. Moreover, copper will be detected from the copper mesh used for TEM measurement.

(Palladium content in particles containing palladium)
First, an evaluation sample was prepared by a method using the following copper-clad laminate.

<Method using copper-clad laminate>
A copper-clad laminate “MCL-E-679F” (trade name, manufactured by Hitachi Chemical Co., Ltd.) was cut into a size of 1 cm × 1 cm to obtain a substrate. The substrate was immersed in a degreasing solution “Z-200” (trade name, manufactured by World Metal Co., Ltd.) at 50 ° C. for 1 minute and washed with water for 1 minute. Next, it was immersed in a 100 g / L ammonium persulfate solution for 1 minute and washed with water for 1 minute. Subsequently, it was immersed in 10% sulfuric acid for 1 minute and washed with water for 1 minute. Next, it was immersed in “SA-100” (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a plating activation treatment solution, at 25 ° C. for 5 minutes and washed with water for 1 minute. Subsequently, 11.5% by mass of phosphorus is contained on the copper foil by immersing in Top Nicolon NAC [trade name, manufactured by Okuno Pharmaceutical Co., Ltd.], which is an electroless nickel plating solution, at 85 ° C. for 4 minutes. The electroless nickel plating film thus formed was formed to a thickness of 0.7 μm. Subsequently, this was washed with water for 1 minute. Next, the electroless palladium plating having a thickness of about 0.1 μm is immersed on the electroless nickel plating film by immersing in the electroless palladium plating solution having the composition and the amount of (step c) at 60 ° C. for 10 minutes. A film was formed. Subsequently, this was washed with water for 1 minute and dried, and then a sample for evaluation was obtained.

  Next, the obtained sample for evaluation was cast resin (epoxy resin 815 (trade name, manufactured by Japan Epoxy Resin Co., Ltd.) 90% by mass and triethylenetetramine (trade name, manufactured by Wako Pure Chemical Industries, Ltd.) 10% by mass. In order to be able to observe the cross section of the electroless palladium plating film, the cross section was cut out by an ultramicrotome method and observed at a magnification of 250,000 times using a TEM apparatus. Subsequently, for the electroless palladium plated coating, the palladium content was calculated by component analysis using an EDX detector, and this was used as the palladium content in the particles containing palladium. The palladium content in the particles containing palladium thus obtained was 100%. In addition, when the particle | grains containing palladium contain components other than palladium, the content was also calculated by the component analysis by the EDX detector about the sample for evaluation similarly to palladium.

(Evaluation of protrusions formed on the surface of conductive particles)
About the obtained electroconductive particle, it observed by 30,000 times with the SEM apparatus, and the coverage by the processus | protrusion on the surface of an electroconductive particle was computed based on the SEM image. In addition, the number and ratio of protrusions in a concentric circle having a diameter that is ½ of the diameter of the conductive particles were observed with a SEM apparatus at a magnification of 30,000, and calculated based on the SEM image. FIG. 8 shows the result of observing the surface of the conductive particles with an SEM apparatus.

  In addition, the height of the protrusion was obtained based on the obtained image by cutting out a cross section of the conductive particle by an ultramicrotome method so as to pass through the vicinity of the center of the particle, observing at a magnification of 250,000 times using a TEM apparatus. . The heights of the ten protrusions were obtained, and the average value thereof was defined as the average height. FIG. 13 is a diagram for explaining a method of obtaining the height of the protrusion from the STEM image of FIG. As shown in FIG. 13, the height of the protrusion was measured as the distance from the straight line connecting the valleys on both sides of the protrusion to the apex of the protrusion in the vertical direction.

  Moreover, the presence or absence of the protrusion (abnormal precipitation part) exceeding 500 nm height was discriminate | determined by the method typically shown in FIG. Specifically, the distance from the straight line connecting the valleys on both sides of the abnormal precipitation part to the apex of the abnormal precipitation part was measured for 1,000 conductive particles observed with a SEM device at a magnification of 30,000 times. The number of conductive particles having abnormal precipitation portions exceeding 500 nm in height was counted.

  The coverage of the protrusions was observed with a SEM apparatus at a magnification of 30,000, and based on the SEM image, the protrusion forming part and the flat part were distinguished by image analysis in a concentric circle having a diameter that is 1/2 of the diameter of the conductive particles. The ratio of the protrusion forming portion in the concentric circle was calculated to obtain the protrusion coverage.

  The distribution of the protrusion height was obtained as the number ratio (%) of protrusions having a predetermined height from the measurement result of D4 shown in FIG.

  The outer diameter of the protrusion is determined by measuring the area of the contour of the valley of the protrusion for the protrusion existing in a concentric circle having a diameter of ½ of the diameter of the conductive particle on the orthographic projection surface of the conductive particle. The average value of the diameters calculated when considering the area was calculated. Specifically, the conductive particles are observed at a magnification of 30,000 with a SEM device, and the outline of the protrusion is determined by image analysis based on the obtained SEM image, and the area of each protrusion is calculated, and the average value is calculated from the average value. The outer diameter of the protrusion was determined.

[Preparation of insulating coated conductive particles]
A 30% by mass aqueous solution of polyethyleneimine having a molecular weight of 70,000 (manufactured by Wako Pure Chemical Industries, Ltd.) was diluted to 0.3% by mass with ultrapure water. 200 g of conductive particles obtained by the same method as described above was added to 300 mL of this 0.3 mass% polyethyleneimine aqueous solution, and the mixture was stirred at room temperature for 15 minutes. Conductive particles were removed by filtration using a φ3 μm membrane filter (manufactured by Merck), and the extracted conductive particles were placed in 200 g of ultrapure water and stirred at room temperature for 5 minutes. Further, the conductive particles were taken out by filtration using a φ3 μm membrane filter (manufactured by Merck), and the conductive particles on the membrane filter were washed twice with 200 g of ultrapure water to remove non-adsorbed polyethyleneimine.

  Subsequently, the colloidal silica dispersion liquid with a diameter of 130 nm was diluted with ultrapure water to obtain a 0.1 mass% silica particle dispersion liquid. 200 g of conductive particles treated with the above polyethyleneimine were put therein and stirred at room temperature for 15 minutes. Conductive particles were removed by filtration using a φ3 μm membrane filter (manufactured by Merck), and the extracted conductive particles were placed in 200 g of ultrapure water and stirred at room temperature for 5 minutes. Furthermore, the conductive particles are taken out by filtration using a φ3 μm membrane filter (Merck), and the conductive particles on the membrane filter are washed twice with 200 g of ultrapure water to remove unadsorbed silica particles. Insulating coated conductive particles having silica particles adsorbed on the surface were obtained.

  SC6000 (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a silicone oligomer having a molecular weight of 3000, was attached to the surface of the obtained insulating coated conductive particles to make the surface of the insulating coated conductive particles hydrophobic. The insulating coated conductive particles after the hydrophobization were dried by heating in the order of 30 minutes at 80 ° C. and 1 hour at 120 ° C. to obtain hydrophobic insulated coated conductive particles. The average coverage of the conductive particles by silica particles was measured by image analysis of the SEM image and found to be about 28%.

[Preparation of anisotropic conductive adhesive film and connection structure]
Copolymer of 100 g of phenoxy resin (trade name “PKHC” manufactured by Union Carbide) and acrylic rubber (40 parts by mass of butyl acrylate, 30 parts by mass of ethyl acrylate, 30 parts by mass of acrylonitrile, 3 parts by mass of glycidyl methacrylate, molecular weight: 85 10) was dissolved in 400 g of ethyl acetate to obtain a solution. To this solution, 300 g of a liquid epoxy resin (epoxy equivalent 185, manufactured by Asahi Kasei Epoxy Co., Ltd., trade name “Novacure HX-3941”) containing a microcapsule type latent curing agent was added and stirred to obtain an adhesive solution. .

  The insulating coating particles obtained above were dispersed in this adhesive solution so as to be 9% by volume based on the total amount of the adhesive solution to obtain a dispersion. The obtained dispersion is applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) using a roll coater, dried by heating at 90 ° C. for 10 minutes, and anisotropic conductive adhesive having a thickness of 25 μm. A film was made on the separator.

Next, using the produced anisotropic conductive adhesive film, a chip (1.7 × 1.7 mm, thickness: 0) with gold bumps (area: 30 × 90 μm, space: 10 μm, height: 15 μm, bump number: 362) 0.5 μm) and a glass substrate with an IZO circuit (thickness: 0.7 mm) were connected according to the following procedures i) to iii) to obtain a connection structure.
i) An anisotropic conductive adhesive film (2 × 19 mm) was attached to a glass substrate with an IZO circuit at 80 ° C. and 0.98 MPa (10 kgf / cm ² ).
ii) The separator was peeled off, and the bumps of the chip and the glass substrate with IZO circuit were aligned.
iii) The main connection was performed by heating and pressing from above the chip under the conditions of 190 ° C., 40 gf / bump, and 10 seconds.

[Evaluation of connection structure]
The conduction resistance test and the insulation resistance test of the obtained connection structure were performed as follows.

(Conduction resistance test)
Regarding the conduction resistance between the chip electrode (bump) / glass electrode (IZO), the initial value of the conduction resistance and the moisture absorption heat resistance test (left for 100, 300, 500, 1000, 2000 hours under conditions of temperature 85 ° C. and humidity 85%) The latter values were measured for 20 samples and their average value was calculated. The conduction resistance was evaluated from the average value obtained according to the following criteria. The results are shown in Table 1. In addition, it can be said that conduction resistance is favorable when the following A or B standard is satisfied after the moisture absorption heat test 500 hours.
A: Average value of conduction resistance is less than 2Ω B: Average value of conduction resistance is 2Ω or more and less than 5Ω C: Average value of conduction resistance is 5Ω or more and less than 10Ω D: Average value of conduction resistance is 10Ω or more and less than 20Ω E: Conduction resistance The average value of 20Ω or more

(Insulation resistance test)
Regarding the insulation resistance between chip electrodes, the initial value of the insulation resistance and the value after migration test (temperature 60 ° C., humidity 90%, 20 V applied for 100, 300, 500, 1000 hours) were measured for 20 samples. And the ratio of the sample from which the insulation resistance value becomes 10 ⁹ Ω or more among all 20 samples was calculated. The insulation resistance was evaluated from the obtained ratio according to the following criteria. The results are shown in Table 1. In addition, it can be said that insulation resistance is favorable when the following A or B standard is satisfied after 500 hours of the moisture absorption heat test.
A: Ratio of insulation resistance value of 10 ⁹ Ω or more is 100%
B: Ratio of insulation resistance value 10 ⁹ Ω or more is 90% or more and less than 100% C: Ratio of insulation resistance value 10 ⁹ Ω or more is 80% or more and less than 90% D: Ratio of insulation resistance value 10 ⁹ Ω or more is 50% More than 80% and less than E: Insulation resistance of 10 ⁹ Ω or more is less than 50%

<Examples 2 to 4>
In Example 1 (step d), except that the average thickness of the second layer was changed to the thickness shown in Table 1 by changing the dropping amount of the electroless nickel plating solution for forming the second layer. In the same manner as in Example 1, production of conductive particles, insulating coating particles, anisotropic conductive adhesive films and connection structures, and evaluation of the conductive particles and connection structures were performed. The results are shown in Table 1. The dropping amount of the electroless nickel plating solution for forming the second layer was adjusted by increasing or decreasing in proportion to the target thickness. The dropping rate of 5 mL / min was all the same.

<Examples 5-7>
In the same manner as in Example 1 except that the number, ratio, and average height of the particles containing palladium in Example 1 (step c) were changed to those shown in Table 1, conductive particles, insulating coating particles, anisotropic The production of the conductive adhesive film and the connection structure, and the evaluation of the conductive particles and the connection structure were performed. The results are shown in Table 1. In addition, formation of the particle | grains containing palladium was performed using the electroless palladium plating solution of the same composition as the (process c) of Example 1, and changing only the quantity of the plating solution. Specifically, 650 mL of plating solution was used in Example 5, 200 mL in Example 6, and 1250 mL of plating solution in Example 7.

<Example 8>
Example 1 (Step c) is the same as Example 1 except that 1 L of electroless palladium plating solution having the following composition was used to form particles containing palladium of 97 mass% palladium and 3 mass% phosphorus. Then, production of conductive particles, insulating coating particles, anisotropic conductive adhesive film and connection structure, and evaluation of conductive particles and connection structure were performed. The results are shown in Table 1.
(Electroless palladium plating solution)
Palladium chloride: 0.07g / L
Ethylenediamine ... 0.05g / L
Sodium hypophosphite 0.4g / L
Thiodiglycolic acid ... 10ppm
pH ... 8

<Example 9>
Example 1 (Step c) is the same as Example 1 except that 1 L of electroless palladium plating solution having the following composition was used to form particles containing palladium consisting of 94% by mass of palladium and 6% by mass of phosphorus. Then, production of conductive particles, insulating coating particles, anisotropic conductive adhesive film and connection structure, and evaluation of conductive particles and connection structure were performed. The results are shown in Table 1.
(Electroless palladium plating solution)
Palladium chloride: 0.07g / L
Ethylenediamine ... 0.05g / L
Sodium hypophosphite ... 0.8g / L
Thiodiglycolic acid ... 10ppm
pH ... 8

<Examples 10 to 12>
In Example 1 (step b), except that the electroless nickel plating solution for forming the first layer was changed, and the nickel content in the first layer was changed to the content shown in Table 2. In the same manner as in Example 1, production of conductive particles, insulating coating particles, anisotropic conductive adhesive films and connection structures, and evaluation of the conductive particles and connection structures were performed. The results are shown in Table 2. In addition, the composition of the electroless nickel plating solution for 1st layer formation used in Examples 10-12 is shown below. These were only changes in the composition, and all other conditions were the same as in (Step b) of Example 1. Moreover, in Example 11, since the composition of the electroless nickel plating solution of the first layer and the second layer is the same, and the obtained plating film has almost the same composition, component analysis by the EDX detector Then, the first layer and the second layer could not be distinguished. Therefore, the film thickness of the second layer is calculated by calculating the film thickness including the first layer and the second layer after the formation of the second layer, and calculating the film thickness of the first layer measured in advance. The value obtained by dividing was taken as the film thickness of the second layer.
(Electroless nickel plating solution for forming the first layer in Example 10)
Nickel sulfate ... 400g / L
Sodium hypophosphite ... 150g / L
Acetic acid ... 120g / L
Bismuth nitrate aqueous solution (1 g / L) ... 1 mL / L
(Electroless nickel plating solution for forming the first layer in Example 11)
Nickel sulfate ... 400g / L
Sodium hypophosphite ... 150g / L
Sodium tartrate dihydrate ... 120g / L
Bismuth nitrate aqueous solution (1 g / L) ... 1 mL / L
(Electroless nickel plating solution for forming the first layer in Example 12)
Nickel sulfate ... 400g / L
Sodium hypophosphite ... 150g / L
Sodium tartrate dihydrate ... 60g / L
Lactic acid ... 60g / L
Bismuth nitrate aqueous solution (1 g / L) ... 1 mL / L

<Examples 13 to 14>
In Example 1 (Step d), except that the electroless nickel plating solution for forming the second layer was changed to change the content of nickel in the second layer to the content shown in Table 2. In the same manner as in Example 1, production of conductive particles, insulating coating particles, anisotropic conductive adhesive films and connection structures, and evaluation of the conductive particles and connection structures were performed. The results are shown in Table 2. In addition, the composition of the electroless nickel plating solution for 2nd layer formation used in Examples 13-14 is shown below. These were only changes in the composition, and all other conditions were the same as in (Step b) of Example 1. Moreover, in Example 14, since the composition of the electroless nickel plating solution of the first layer and the second layer is the same, and the obtained plating film has almost the same composition, component analysis by the EDX detector Then, the first layer and the second layer could not be distinguished. Therefore, the film thickness of the second layer is calculated by calculating the film thickness including the first layer and the second layer after the formation of the second layer, and calculating the film thickness of the first layer measured in advance. The value obtained by dividing was taken as the film thickness of the second layer.
(Electroless nickel plating solution for forming the second layer in Example 13)
Nickel sulfate ... 400g / L
Sodium hypophosphite ... 150g / L
Acetic acid ... 120g / L
Bismuth nitrate aqueous solution (1 g / L) ... 1 mL / L
(Electroless nickel plating solution for forming the second layer in Example 14)
Nickel sulfate ... 400g / L
Sodium hypophosphite ... 150g / L
Sodium citrate ... 120g / L
Bismuth nitrate aqueous solution (1 g / L) ... 1 mL / L

<Example 15>
In the same manner as in Example 1 except that the electroless nickel plating solution for forming the second layer was changed to a plating solution having the following composition in (Step d) of Example 1, conductive particles, insulating coating particles, anisotropic The production of the conductive adhesive film and the connection structure, and the evaluation of the conductive particles and the connection structure were performed. The results are shown in Table 2.
(Electroless nickel plating solution for second layer formation)
Nickel sulfate ... 400g / L
Dimethylamine borane ... 80g / L
Sodium tartrate dihydrate ... 120g / L
Bismuth nitrate aqueous solution (1 g / L) ... 1 mL / L

<Example 16>
4 g of conductive particles produced in the same manner as in Example 1 were immersed in 1 L of electroless palladium plating solution having the following composition to form a third layer. The treatment was carried out at a reaction time of 10 minutes and at a temperature of 50 ° C. The average thickness of the third layer was 10 nm, and the palladium content in the third layer was 100%. Except for using these conductive particles, insulation coated particles, anisotropic conductive adhesive films and connection structures were produced in the same manner as in Example 1, and the conductive particles and connection structures were evaluated. The results are shown in Table 2.
(Electroless palladium plating solution)
Palladium chloride: 0.07g / L
EDTA ・ Sodium ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 1g / L
Citric acid, disodium ... 1g / L
Sodium formate …… 0.2g / L
pH ... 6

<Example 17>
4 g of the conductive particles produced in the same manner as in Example 1 were immersed in 1 L of a solution of HGS-100 (Hitachi Chemical Co., Ltd., trade name) 100 mL / L, which is a displacement gold plating solution, at 85 ° C. for 2 minutes, and further for 2 minutes. Washed with water to form a fourth layer. The average thickness of the fourth layer was 10 nm, and the gold content in the fourth layer was 99.9%. Except for using these conductive particles, insulation coated particles, anisotropic conductive adhesive films and connection structures were produced in the same manner as in Example 1, and the conductive particles and connection structures were evaluated. The results are shown in Table 2.

<Comparative Example 1>
The same (Step a) and (Step b) as in Example 1 were performed to obtain 4 g of particles in which the first layer was formed on the surface of the resin particles.

  After washing the particles with water and filtering, while stirring 200 mL of cleaner conditioner 231 aqueous solution (Rohm and Haas Electronic Materials Co., Ltd., concentration: 40 mL / L), 4 g of particles were added thereto at 60 ° C. The particles were surface-treated by stirring for 30 minutes while applying ultrasonic waves. Subsequently, the aqueous solution was filtered, and the obtained particles were washed with water. Then, 4 g of the particles were dispersed in water to make a 200 mL slurry. To this slurry, 200 mL of stannous chloride aqueous solution (concentration: 1.2 g / L) was added and stirred for 5 minutes at room temperature to perform sensitization treatment for adsorbing tin ions on the first layer.

  Next, the slurry was filtered, and the obtained particles were washed with water. Then, 4 g of the particles were dispersed in water to make a 400 mL slurry, and heated to 60 ° C. 3 mL of a 19.5 g / L palladium chloride aqueous solution was added while stirring the slurry using ultrasonic waves. An activation treatment for trapping palladium ions on the first layer was performed by stirring for 5 minutes. Thereafter, the slurry was filtered, and the obtained particles were washed with water, followed by further washing with hot water. 4 g of the obtained particles were dispersed in water to make a 200 mL slurry. The slurry was stirred while using ultrasonic waves, and 20 mL of a mixed aqueous solution of 1 g / L dimethylamine borane and 10 g / L boric acid was added thereto. The mixture was stirred for 2 minutes at room temperature and combined with ultrasonic waves to reduce palladium ions.

  Thereafter, the same (step d) as in Example 1 was performed to form a second layer, thereby obtaining conductive particles. Except for using these conductive particles, insulation coated particles, anisotropic conductive adhesive films and connection structures were produced in the same manner as in Example 1, and the conductive particles and connection structures were evaluated. The results are shown in Table 3.

  FIG. 15 shows an SEM image obtained by observing particles after reduction treatment of palladium ions (palladium catalyzed treatment), FIG. 16 shows an SEM image obtained by observing conductive particles after forming the second layer, and FIG. The observed STEM images and mapping diagrams of nickel, phosphorus and palladium by the EDX detector are shown in FIG.

  From FIG. 15, formation of particles containing palladium could not be confirmed on the surface of the particles after the reduction treatment of palladium ions. From the analysis result of the particle cross section by STEM / EDX in FIG. Formation could not be confirmed. Further, it was found that no protrusions were formed on the surface of the conductive particles after forming the second layer, and the surface was smooth.

<Comparative Example 2>
Cross-linked polystyrene particles having an average particle size of 3.0 μm (trade name “Soriostar” manufactured by Nippon Shokubai Co., Ltd. were used as resin particles. 400 mL of cleaner conditioner 231 aqueous solution (Rohm and Haas Electronic Materials Co., Ltd., concentration: 40 mL) / L), 30 g of resin particles were added thereto, followed by heating the aqueous solution to 60 ° C. and stirring for 30 minutes while applying ultrasonic waves to perform surface modification and dispersion treatment of the resin particles. It was.

  The aqueous solution was filtered, and the resulting particles were washed once with water, and then 30 g of the particles were dispersed in water to make a 200 mL slurry. To this slurry, 200 mL of stannous chloride aqueous solution (concentration: 1.5 g / L) was added and stirred for 5 minutes at room temperature to perform sensitization treatment for adsorbing tin ions on the surface of the particles. Subsequently, the aqueous solution was filtered, and the resulting particles were washed once with water. Next, 30 g of the particles were dispersed in water to make a 400 mL slurry and heated to 60 ° C. While stirring the slurry using ultrasonic waves, 2 mL of a 10 g / L palladium chloride aqueous solution was added. The mixture was stirred for 5 minutes as it was to perform an activation treatment for trapping palladium ions on the surface of the particles. Subsequently, the aqueous solution was filtered, and the resulting particles were washed once with water.

  Next, 3 liters of electroless plating solution composed of an aqueous solution in which 20 g / L sodium tartrate, 10 g / L nickel sulfate and 0.5 g / L sodium hypophosphite were dissolved was heated to 60 ° C. 10 g of the above particles were added to the plating solution. This was stirred for 5 minutes, and it was confirmed that hydrogen foaming stopped.

  Thereafter, a 200 g / L nickel sulfate aqueous solution (400 mL) and a 200 g / L sodium hypophosphite and 90 g / L sodium hydroxide mixed aqueous solution (400 mL) were each simultaneously and continuously converted into a plating solution containing particles by a metering pump. Added. The addition rate was 3 mL / min. Next, the solution was stirred for 5 minutes while maintaining the temperature at 60 ° C., then the solution was filtered, the filtrate was washed three times, and then dried in a vacuum dryer at 100 ° C. to obtain a conductive material having a nickel-phosphorus alloy film. Particles were obtained. About the obtained conductive particles, a cross-section is cut out by an ultramicrotome method so as to pass through the vicinity of the center of the particles, and observed at a magnification of 250,000 times using a TEM apparatus, and based on the obtained cross-sectional image, the average cross-sectional area is obtained. As a result of calculating the film thickness from the value, the average film thickness was 105 nm.

  Except that the above conductive particles were used, the insulation coated particles, the anisotropic conductive adhesive film and the connection structure were produced in the same manner as in Example 1, and the conductive particles and the connection structure were evaluated. The results are shown in Table 3.

<Comparative Example 3>
Cross-linked polystyrene particles having an average particle size of 3.0 μm (trade name “Soriostar” manufactured by Nippon Shokubai Co., Ltd. were used as resin particles. 400 mL of cleaner conditioner 231 aqueous solution (Rohm and Haas Electronic Materials Co., Ltd., concentration: 40 mL) / L), 7 g of resin particles were added thereto, followed by heating the aqueous solution to 60 ° C. and stirring for 30 minutes while applying ultrasonic waves to perform surface modification and dispersion treatment of the resin particles. It was.

  The aqueous solution was filtered, and the resulting particles were washed once with water. Then, 7 g of the particles were dispersed in pure water to make a 200 mL slurry. To this slurry, 200 mL of stannous chloride aqueous solution (concentration: 1.5 g / L) was added and stirred for 5 minutes at room temperature to perform sensitization treatment for adsorbing tin ions on the surface of the particles. Subsequently, the aqueous solution was filtered, and the resulting particles were washed once with water. Next, 7 g of the particles were dispersed in water to make a 400 mL slurry, and heated to 60 ° C. While stirring the slurry using ultrasonic waves, 2 mL of a 10 g / L palladium chloride aqueous solution was added. The mixture was stirred for 5 minutes as it was to perform an activation treatment for trapping palladium ions on the surface of the particles. Subsequently, the aqueous solution was filtered, and the resulting particles were washed once with water.

  After adding 7 g of the obtained resin particles to 300 mL of pure water and stirring for 3 minutes to disperse, nickel particles (trade name “2007SUS” manufactured by Mitsui Mining & Smelting Co., Ltd., average particle diameter of 50 nm) are dispersed in the dispersion. ) 2.25 g was added to obtain particles with the core material attached.

  The above dispersion was further diluted with 1200 ml of water, and 4 mL of a bismuth nitrate aqueous solution (concentration 1 g / L) was added as a plating stabilizer. Then, nickel sulfate 450 g / L, sodium hypophosphite 150 g / L, citric acid were added to the dispersion. 120 mL of a mixed solution of 116 g / L of sodium and 6 mL of a plating stabilizer [bismuth nitrate aqueous solution (concentration: 1 g / L)] was added through a metering pump at an addition rate of 81 mL / min. Then, it stirred until pH was stabilized and it confirmed that the foaming of hydrogen stopped.

  Subsequently, 650 mL of a mixed solution of 450 mL of nickel sulfate, 150 g / L of sodium hypophosphite, 116 g / L of sodium citrate, and 35 mL of a plating stabilizer [bismuth nitrate aqueous solution (concentration 1 g / L)] was added at 27 mL / min. Added at a rate through a metering pump. Then, it stirred until pH was stabilized and it confirmed that the foaming of hydrogen stopped.

  Next, the plating solution was filtered, and the filtrate was washed with water, and then dried with a vacuum dryer at 80 ° C. to obtain conductive particles having a nickel-phosphorus alloy coating. About the obtained conductive particles, a cross-section is cut out by an ultramicrotome method so as to pass through the vicinity of the center of the particles, and observed at a magnification of 250,000 times using a TEM apparatus, and based on the obtained cross-sectional image, the average cross-sectional area is obtained. As a result of calculating the film thickness from the value, the average film thickness was 101 nm.

  Except that the above conductive particles were used, the insulation coated particles, the anisotropic conductive adhesive film and the connection structure were produced in the same manner as in Example 1, and the conductive particles and the connection structure were evaluated. The results are shown in Table 3.

  In Comparative Example 1, palladium-catalyzed treatment was performed instead of forming particles containing palladium. Comparative Example 2 corresponds to Patent Document 1, and Comparative Example 3 corresponds to Patent Document 2.

  From the results of Tables 1 and 2, it was revealed that the conductive particles produced in Examples 1 to 17 can obtain excellent conduction reliability and insulation reliability even after the moisture absorption heat test. In addition, although the conductive particles produced in Examples 12 and 14 had higher conduction resistance after 1000 hours of the moisture absorption test than the other examples, the insulation resistance was excellent and sufficiently practical according to the required use. It turns out that it can be served. On the other hand, in the comparative example 1, it turned out that the particle | grains containing palladium are not formed and the surface of a metal layer becomes smooth. When this conductive particle was used, the conduction resistance value increased after the moisture absorption heat test. In addition, since the conductive particles of Comparative Examples 2 and 3 had an abnormal precipitation portion exceeding the height of 500 nm, the insulation characteristics were deteriorated after the moisture absorption heat test.

  DESCRIPTION OF SYMBOLS 1 ... Insulator particle | grains, 2 ... Conductive particle, 10 ... Insulation covering electroconductive particle, 20 ... Insulating adhesive, 20a ... Hardened | cured material of an insulating adhesive, 30 ... 1st circuit member, 31 ... Circuit board ( 1st circuit board), 31a ... main surface of the 1st circuit board, 32 ... circuit electrode (1st circuit electrode), 40 ... 2nd circuit member, 41 ... circuit board (2nd circuit board), 41a ... main surface of second circuit board, 42 ... circuit electrode (second circuit electrode), 50 ... film-like anisotropic conductive adhesive, 50a ... connection part, 100 ... connection structure, 200 ... first 201 ... particles containing palladium, 202 ... second layer, 203 ... resin particles, 204 ... metal layer, 205 ... protrusions, 300 ... conductive particles having a protrusion shape, 301 ... abnormal precipitation portion, 302 ... abnormal precipitation The height of the part.

Claims (19)

Resin particles and a metal layer containing nickel provided on the surface of the resin particles,
The metal layer contains particles containing palladium, and has a protrusion on the outer surface on the particles containing palladium,
The palladium-containing grains have a length in the thickness direction of the metal layer of 4 nm or more, and the shortest distance to the interface between the metal layer and the resin particles is 10 nm or more,
The electroconductive particle whose content of palladium in the particle | grains containing the said palladium is 94 mass% or more.   The metal layer contains particles containing palladium whose shortest distance to the interface between the metal layer and the resin particles is 0.1 × d or more, where d is the average thickness of the metal layer. The conductive particles according to claim 1. Resin particles and a metal layer containing nickel provided on the surface of the resin particles,
The metal layer contains particles containing palladium, and has a protrusion on the outer surface on the particles containing palladium,
The particles containing palladium have a length in the thickness direction of the metal layer of 4 nm or more, and when the average thickness of the metal layer is d, up to the interface between the metal layer and the resin particles The shortest distance is 0.1 × d or more,
The electroconductive particle whose content of palladium in the particle | grains containing the said palladium is 94 mass% or more.   The conductive particles according to claim 1, wherein the metal layer contains particles containing the palladium scattered in a direction orthogonal to the thickness direction of the metal layer.   The conductive layer according to any one of claims 1 to 4, wherein the metal layer includes particles containing the palladium passing through a straight line connecting the apex of the protrusion and an interface between the metal layer and the resin particle at a shortest distance. particle. The electroconductive particle as described in any one of Claims 1-5 in which the particle | grains containing the said palladium contain phosphorus. The metal layer contains a first layer containing nickel and a second layer containing nickel in the order closer to the resin particles,
The nickel content in the first layer is 83 to 98% by mass,
The electroconductive particle as described in any one of Claims 1-6 whose content of nickel in a said 2nd layer is 93 mass% or more. The electroconductive particle of Claim 7 whose content of nickel in a said 1st layer is 85-93 mass%. The conductive particles according to claim 7 or 8 , wherein a content of nickel in the second layer is 96% by mass or more. Wherein the first layer containing phosphorus, conductive particles according to any one of claims 7-9. The conductive particles according to any one of claims 7 to 10 , wherein the second layer contains phosphorus or boron. The metal layer, the opposite side to the first layer of the second layer, further comprising a third layer comprising palladium, conductive particles according to any one of claims 7-11. The conductive particle according to any one of claims 7 to 12 , wherein the metal layer further includes a fourth layer containing gold on a side opposite to the first layer of the second layer. Forming a first layer containing nickel on the surface of the resin particles by electroless nickel plating;
On the first layer, the length in the thickness direction of the first layer is 4 nm or more by reduction deposition of an electroless palladium plating solution containing palladium ions and a reducing agent, and the content of palladium is Forming a particle containing palladium that is 94% by mass or more;
The second layer having nickel on the first layer and the particle containing palladium by electroless nickel plating and having a protrusion on the surface opposite to the resin particle side on the particle containing palladium. And a step of forming a layer of the conductive particles. Insulated coated conductive particles comprising the conductive particles according to any one of claims 1 to 13 and insulator particles covering at least part of the surface of the metal layer of the conductive particles. An anisotropic conductive adhesive containing the conductive particles according to any one of claims 1 to 13 and an adhesive. An anisotropic conductive adhesive comprising the insulating coated conductive particles according to claim 15 and an adhesive. An anisotropic conductive adhesive film that is in the form of a film and comprises the anisotropic conductive adhesive according to claim 16 or 17 . A first circuit member having a first circuit electrode; a second circuit member having a second circuit electrode opposed to the first circuit electrode; and the first circuit member and the second circuit member. And a connecting portion provided between and
The connecting portion includes a cured product of the adhesive for bonding the said first circuit member and the second circuit member, wherein the conductive particle or claim 15 according to any one of claims 1 to 13 Insulating coating conductive particles, and
A connection structure in which the first circuit electrode and the second circuit electrode are electrically connected via the conductive particles or the insulating coated conductive particles.