KR102489993B1 - Conductive particle, anisotropic conductive adhesive, connecting structure and method for producing conductive particle - Google Patents

Abstract

Conductive particles capable of achieving both low conduction resistance and high insulation reliability when used as conductive particles mixed in an anisotropic conductive adhesive and maintaining a low electrical resistance value even when subjected to high compression, an anisotropic conductive adhesive using the conductive particles, and A connection structure and a method for producing conductive particles are provided.
The conductive particles include resin particles and a metal layer provided on the surface of the resin particles, and the metal layers are, in order close to the resin particles, a first layer containing copper or nickel and copper, and a second layer containing nickel. It has two layers and contains grains containing palladium having a length of 4 nm or more in the thickness direction of the metal layer, and protrusions are formed on the outer surface of the metal layer.

Description

Conductive particle, anisotropic conductive adhesive, connection structure, and manufacturing method of conductive particle

The present invention relates to conductive particles, an anisotropic conductive adhesive, a bonded structure, and a method for producing conductive particles.

Methods of mounting a liquid crystal driving IC on a glass panel for a liquid crystal display can be broadly classified into two types: COG (Chip-on-Glass) mounting and COF (Chip-on-Flex) mounting. In COG mounting, an IC for driving a liquid crystal is directly bonded onto a glass panel using an anisotropic conductive adhesive containing conductive particles. On the other hand, in COF mounting, liquid crystal drive ICs are bonded to a flexible tape having metal wiring, and they are bonded to a glass panel using an anisotropic conductive adhesive containing conductive particles. Anisotropy as used herein means conducting in the pressurized direction and maintaining insulation in the non-pressurized direction.

Conventionally, as the conductive particles, conductive particles having a gold layer formed on the surface have been used. Conductive particles having a gold layer formed on the surface are advantageous in that they have a low electrical resistance value. Further, since gold is hardly oxidized, an increase in electrical resistance value can be suppressed even when the conductive particles having a gold layer formed on the surface are stored for a long period of time.

By the way, in response to recent energy saving, for the purpose of suppressing power consumption during liquid crystal driving, reducing the amount of current flowing through the IC has been studied. For this reason, conductive particles having a lower electrical resistance value than before have been demanded. Further, since the price of noble metals has risen in recent years, it has been desired to lower the electrical resistance value of conductive particles without using noble metals.

For example, Patent Literatures 1 and 2 disclose conductive particles capable of obtaining a low electrical resistance value by using only nickel without using a noble metal. Specifically, in Patent Literature 1, nickel fine protrusions and nickel coatings are simultaneously formed on non-conductive particles by using the self-decomposition of a nickel plating solution in an electroless nickel plating method to produce conductive particles having conductive protrusions on the surface. method is described. Further, Patent Literature 2 describes a method of producing conductive particles having conductive protrusions on the surface by adhering a conductive material serving as a core material to the surface of substrate fine particles and further performing electroless nickel plating.

Japanese Patent No. 5184612 Japanese Patent No. 4674096

As a result of investigation by the present inventors, the bonded structure obtained by the anisotropic conductive adhesive containing the conductive particles described in Patent Literatures 1 and 2 shows a sufficient insulation resistance value at the initial stage of connection, but after a migration test in which conduction is conducted for a long period of time under high temperature and high humidity It has been found that there is a case where the insulation resistance value is lowered and there is a problem in terms of insulation reliability. Further, in the case of the conductive particles having an alloy plating film containing nickel and phosphorus described in Patent Literatures 1 and 2, it has been found that the electrical resistance value of the conductive particles increases when the conductive particles are highly compressed (for example, at a compression ratio of 80%). .

The present invention provides conductive particles capable of achieving both low conduction resistance and high insulation reliability when used as conductive particles mixed in an anisotropic conductive adhesive and maintaining a low electrical resistance value even when subjected to high compression, and an anisotropic method using the conductive particles. It aims to provide a conductive adhesive, a connection structure, and a manufacturing method of conductive particles.

As a result of studies to solve the above problems, the inventors of the present invention have found that in the conductive particles described in Patent Literatures 1 and 2, projections of abnormal sizes are easily formed when trying to increase conductivity, and the presence of conductive particles having such abnormal projections is insulating. It was found that this leads to a decrease in reliability. Further, the present inventors have found that the electric resistance value of the conductive particles increases due to breakage of the nickel plating film during compression.

As a result of further intensive examination by the present inventors based on this knowledge, after forming a first layer containing copper or nickel and copper on the surface of the resin particle, forming grains containing palladium, and further containing palladium By providing a second layer having protrusions formed by grains, it is possible to achieve both low electrical resistance and high insulation reliability when used as conductive particles mixed with an anisotropic conductive adhesive, and to maintain a low electrical resistance value even when subjected to high compression. It was found that conductive particles that can be obtained were obtained, and the present invention was completed.

That is, the present invention includes resin particles and a metal layer provided on a surface of the resin particle, the metal layer comprising, in order close to the resin particle, a first layer containing copper or nickel and copper, and nickel. It has a second layer containing palladium-containing grains having a length of 4 nm or more in the thickness direction of the metal layer, and protrusions are formed on the outer surface of the metal layer.

The metal layer may contain palladium-containing grains having a shortest distance to an interface between the metal layer and the resin particles of 0.1 x d or more, when d is the average thickness of the metal layer.

In addition, the present invention is provided with resin particles and a metal layer provided on the surface of the resin particles, the metal layer, in order close to the resin particles, copper or a first layer containing nickel and copper, and nickel It has a second layer containing palladium, and the 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 is d. A second conductive particle having protrusions formed on a surface thereof is provided.

Since protrusions are formed on the outer surface of the conductive particles in the first and second conductive particles, the shape and size of the protrusions can be sufficiently controlled. Therefore, when the first conductive particles and the second conductive particles are used as conductive particles mixed in an anisotropic conductive adhesive, both low electrical resistance and high insulation reliability can be achieved. Further, since the first conductive particles and the second conductive particles have a first layer containing copper having high ductility in the metal layer, breakage of the metal layer can be suppressed even when the conductive particles are highly compressed. Therefore, the first conductive particle and the second conductive particle can maintain a low electrical resistance value even when highly compressed.

By the way, as a pretreatment at the time of performing electroless copper plating or electroless nickel plating on a substrate, a palladium catalyzed treatment for trapping palladium ions on the surface of a substrate is generally known. By this palladium-catalyzed treatment, palladium precipitation nuclei are formed on the surface of the substrate, but the size of these precipitation nuclei is at the atomic level. On the other hand, the grains containing palladium according to the present invention have a size capable of component analysis by EDX described later. Further, projections according to the present invention cannot be formed from palladium precipitation nuclei formed by a general palladium-catalyzed treatment.

In the first conductive particle and the second conductive particle of the present invention, the metal layer may contain the palladium-containing grains between the first layer and the second layer or in the second layer.

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

The metal layer may contain grains containing the palladium dotted in a direction orthogonal to a thickness direction of the metal layer.

It is preferable that content of palladium in the grain containing the said palladium is 94 mass % or more from a viewpoint of obtaining a low electrical resistance value by increasing the number of protrusions.

It is preferable that the grains containing palladium further contain phosphorus. As a result, the hardness of the grains containing palladium can be increased, and the electrical resistance value when the conductive particles are compressed can be kept low.

It is preferable that the first layer has a Ni-Cu layer containing nickel and copper, and that the Ni-Cu layer has a portion where the elemental ratio of copper to nickel increases as the distance from the surface of the resin particle increases. By having such a portion in the metal layer, the conductive particles can maintain a low electrical resistance value even when compressed.

The Ni-Cu layer may have, in order closer to the resin particles, a first portion having a nickel content of 97% by mass or more, a second portion constituting the portion, and a third portion containing copper.

The total of the nickel content and the copper content in the second portion may be 97% by mass or more. Moreover, 97 mass % or more may be sufficient as content of copper in the said 3rd part. By providing such a configuration, when the conductive particles are compressed and connected by compression, breakage of the metal layer after compression can be more sufficiently suppressed.

From the viewpoint of being able to highly control the number, size, and shape of the protrusions, the second layer includes a first nickel-containing layer having a nickel content of 83 to 98% by mass, and a nickel content in order close to the first layer. It is preferable to have this 93 mass % or more 2nd nickel containing layer. This makes it possible to achieve both low electrical resistance and high insulation reliability at a higher level.

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

It is preferable that content of nickel in the said 2nd nickel containing layer is 96 mass % or more from a viewpoint of obtaining a low electrical resistance value.

The first nickel-containing layer may further include phosphorus. As a result, the hardness of the first nickel-containing layer can be increased, and the electrical resistance value when the conductive particles are compressed can be kept low.

The second nickel-containing layer may further include phosphorus or boron. As a result, the hardness of the second layer can be increased, and the electrical resistance value when the conductive particles are compressed can be kept low.

The metal layer may further include a third layer containing palladium and a fourth layer containing gold on opposite sides of the second layer from the first layer. Since palladium has a property that is less oxidized than nickel, and palladium has a high effect of suppressing the diffusion of nickel and can prevent diffusion of nickel to the surface of palladium, the second layer containing nickel is made of palladium. By covering with the third layer containing , it is possible to suppress oxidation of the surface of the conductive particles, and as a result, the electrical resistance value when the conductive particles are compressed can be kept low. Further, since gold is less oxidized than nickel, and the resistance value of gold itself is lower than that of nickel, the metal layer contains a fourth layer containing gold on the outside of the second layer, thereby providing conductive particles. The electrical resistance value when is compressed can be kept low.

Further, the present invention provides a step of forming a first layer containing copper or nickel and copper on the surface of a resin particle by electroless plating, and electroless palladium containing palladium ions and a reducing agent on the first layer. Conductive conduction comprising a step of forming grains containing palladium by reducing precipitation of a plating solution, and a step of forming a second layer containing nickel by electroless nickel plating on the first layer and on the grains containing palladium. A method for producing particles is provided.

Further, the present invention provides a step of forming a first layer containing copper or nickel and copper on the surface of a resin particle by electroless plating, and containing nickel by electroless nickel plating on the first layer. A step of forming a first nickel-containing layer; a step of forming grains containing palladium by reduction precipitation of an electroless palladium plating solution containing palladium ions and a reducing agent on the first nickel-containing layer; A method for producing conductive particles comprising a step of forming a second nickel-containing layer containing nickel by electroless nickel plating on grains containing palladium.

In the method for producing conductive particles, since protrusions are formed on the outer surface of the conductive particles, the shape, size, and the like of the protrusions can be sufficiently controlled. Therefore, the conductive particles obtained by the above manufacturing method can achieve both low electrical resistance and high insulation reliability when used as conductive particles to be blended with an anisotropic conductive adhesive. Further, in the method for producing conductive particles, since the first layer containing copper having high ductility is formed as the metal layer, breakage of the metal layer can be suppressed even when the obtained conductive particles are subjected to high compression. Therefore, the conductive particles obtained by the above production method can maintain a low electrical resistance value even when subjected to high compression.

In addition, the present invention provides an anisotropic conductive adhesive containing the conductive particles or the conductive particles obtained by the above production method, and an adhesive. According to this anisotropic conductive adhesive, a connection structure excellent in both conduction reliability and insulation reliability when circuit electrodes are connected can be obtained by containing the above-mentioned conductive particles.

Further, the present invention arranges a first circuit member having a first circuit electrode and a second circuit member having a second circuit electrode so that the first circuit electrode and the second circuit electrode face each other, and the first circuit member and A connection structure obtained by interposing the conductive particles or the anisotropic conductive adhesive between the second circuit members, heating and pressurizing them to electrically connect the first circuit electrode and the second circuit electrode.

In addition, the present invention provides a device comprising a first circuit member having a first circuit electrode, a second circuit member having a second circuit electrode, and the conductive particles, and connecting the first circuit member and the second circuit member to each other. A connection portion is provided, wherein the first circuit member and the second circuit member are disposed so that the first circuit electrode and the second circuit electrode face each other, and in the connection portion, the first circuit electrode and the second circuit electrode are deformed conductive. A connection structure that is electrically connected through particles is provided.

According to the present invention, 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 maintaining a low electrical resistance value even when subjected to high compression, and the conductive particles The used anisotropic conductive adhesive and connected structure, and the method for producing conductive particles can be provided.

1 (a) is a schematic cross-sectional view showing an embodiment of conductive particles according to the present invention, and (b) is a schematic cross-sectional view showing an embodiment of insulated-coated conductive particles according to the present invention.
2 is a schematic cross-sectional view showing another embodiment of conductive particles according to the present invention.
3(a) is a schematic cross-sectional view for explaining a Ni-Cu layer (first layer) included in conductive particles according to an embodiment of the present invention, and (b) is a Ni-Cu layer (first layer) It is a figure which shows an example of content of nickel and copper of.
4 is a schematic diagram for explaining conductive particles according to an embodiment of the present invention.
5 is a schematic diagram for explaining conductive particles according to an embodiment of the present invention.
6 is a schematic cross-sectional view showing an embodiment of a bonded structure according to the present invention.
Fig. 7 is a schematic cross-sectional view for explaining an example of a method for manufacturing the bonded structure shown in Fig. 6;
Fig. 8 is a SEM image of observed particles obtained in Step c in the production of conductive particles in Example 1.
Fig. 9 is a SEM image of the surface of the particles obtained in step c in the production of conductive particles in Example 1;
Fig. 10 is a SEM image of observed conductive particles obtained in Example 1.
FIG. 11 is a STEM image obtained by observing a cross section of conductive particles obtained in Example 1 and mapping diagrams of copper, nickel, and palladium by EDX.
FIG. 12 is a diagram for explaining a method of obtaining the height of grains containing palladium from the palladium mapping diagram by EDX of FIG. 11 .
13 is a schematic diagram for explaining the trimming process.
14 is a schematic diagram for explaining a method of manufacturing a thin film slice for TEM measurement.
FIG. 15 is a view for explaining a method of obtaining the height of a protrusion from the STEM image of FIG. 11 .

Hereinafter, preferred embodiments of the present invention will be described in detail. 1(a) and 2 are schematic cross-sectional views showing an embodiment of conductive particles according to the present invention, and FIG. 1(b) is a schematic cross-sectional view showing an embodiment of insulated-coated conductive particles according to the present invention. .

<Conducting Particles>

First, the conductive particles of the present embodiment will be described.

The conductive particles 2 shown in FIG. 1(a) include resin particles 203 constituting the core of the conductive particles, copper provided on the surface of the resin particles 203, or a first layer containing nickel and copper. 200, and a metal layer 204 comprising a second layer 202 comprising nickel. The metal layer 204 contains palladium-containing grains 201 having a length of 4 nm or more in the thickness direction of the metal layer 204 . On the outer surface of the second layer 202, protrusions 205 are formed by grains 201 containing palladium.

The conductive particles 12 shown in FIG. 2 include resin particles 203 constituting the core of the conductive particles, and copper provided on the surface of the resin particles 203, or a first layer 200 containing nickel and copper. , and a metal layer 204 including a second layer 202 containing nickel. The second layer 202 includes a first nickel-containing layer 206 and a second nickel-containing layer 207, and contains palladium-containing grains 201 having a length of 4 nm or more in the thickness direction of the metal layer. . Further, on the outer surface of the second nickel-containing layer 207, protrusions 205 are formed by grains 201 containing palladium.

The metal layer 204 is composed of two layers, a first layer 200 containing copper or nickel and copper, and a second layer 202 containing nickel, in order closer to the resin particles 203. , may have a structure of three or more layers.

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. Also, as the resin particles, for example, crosslinked acrylic particles and crosslinked polystyrene particles can be used.

The resin particles 203 are preferably spherical, and their average particle diameter is preferably 1 to 10 μm, more preferably 2 to 5 μm. The average particle diameter of the resin particles 203 in the present embodiment is obtained by measuring the particle diameter of 300 arbitrary resin particles by observation using a scanning electron microscope (hereinafter referred to as SEM) and taking the average value. lose

The first layer 200 contains copper or nickel and copper. The copper content in the first layer 200 can be, for example, 97% by mass or more. In addition, in that aggregation of conductive particles can be suppressed and generation of pinholes can be suppressed, the first layer 200 contains nickel and copper, and the amount of nickel and copper in the first layer 200 is It is preferable to make the sum total of content into 97 mass % or more.

The first layer 200 preferably has a Ni-Cu layer containing nickel and copper. In (a) of FIG. 3, in order to explain a suitable form when the first layer 200 has the Ni-Cu layer 208, the first layer 200 is formed on the surface of the resin particle 203 The conductive particles 22 in a present state are shown for convenience. In the conductive particle 22, the first layer 200 includes a Ni-Cu layer 208 containing nickel and copper.

The total amount of nickel and copper in the Ni-Cu layer 208 is preferably 97% by mass or more, more preferably 98.5% by mass or more, and even more preferably 99.5% by mass or more. The upper limit of the total amount of nickel and copper in the Ni-Cu layer 208 is 100% by mass. In addition, the elemental ratio of copper to nickel in the Ni-Cu layer 208 has a concentration gradient that increases as the distance from the surface of the resin particle 203 increases. It is preferable that this concentration gradient is continuous. In addition, the element ratios in the present invention are determined by, for example, cross-sections of conductive particles cut out with a convergent ion beam, observed with a transmission electron microscope at a magnification of 400,000, and EDX (energy dispersive X-ray spectrometer, Nihon Nihon) attached to the transmission electron microscope. Element ratios in the Ni-Cu layer 208 (for example, a first portion, a second portion, and a third portion described later) can be measured by component analysis by Denshi Datum Co., Ltd.).

The Ni-Cu layer 208 includes, in order closer to the resin particles 203, a first portion 208a containing 97% by mass or more nickel, and a second portion containing an alloy containing nickel and copper as main components ( 208b) and a third portion 208c containing copper as a main component are stacked. These portions 208a, 208b, and 208c are part of the first layer 200 in the thickness direction, and may be layers provided so as to cover almost all or all of the particles.

Fig. 3(b) is a graph showing the nickel content and copper content in the thickness direction of the Ni-Cu layer 208 (first layer 200) containing nickel and copper. In the above graph, the boundary line between the first portion 208a and the second portion 208b is drawn so as to pass through the point where the Ni content (solid line) decreases to 97% by mass. On the other hand, the boundary line between the second part 208b and the third part 208c is drawn so as to pass through the point where the Cu content (broken line) rises to 97% by mass. As shown in FIG. 3(b), the Ni-Cu layer 208 has a second portion 208b in which the elemental ratio of copper to nickel increases as the distance from the surface of the resin particle 203 increases.

The first portion 208a contains 97% by mass or more of nickel. The content of nickel in the first portion 208a is more preferably 98.5% by mass or more, and even more preferably 99.5% by mass or more. When the nickel content is 97% by mass or more, the adhesiveness between the resin particles 203 and the first layer 200 containing nickel and copper can be maintained well. In this way, when the conductive particles 2 and 12 are compressed and connected by high pressure, it is possible to suppress the separation of the compressed resin particles 203 and the first layer 200 containing nickel and copper from each other. The upper limit of the nickel content in the first portion 208a is 100% by mass.

The thickness of the first portion 208a is preferably in the range of 20 to 200 Å (2 to 20 nm), more preferably in the range of 30 to 150 Å (3 to 15 nm), and in the range of 40 to 100 Å (4 to 10 nm). more preferable When the thickness of the first portion 208a is 20 Å (2 nm) or more, aggregation during plating can be suppressed, and when the thickness is 200 Å (20 nm) or less, when the conductive particles are press-connected by high compression, the nickel portion is metal. cracking can be prevented.

The second portion 208b contains an alloy containing nickel and copper as main components. The total of the nickel content and the copper content in the second part 208b is preferably 97% by mass or more, more preferably 98.5% by mass or more, and still more preferably 99.5% by mass or more. If the total of the nickel content and the copper content is 97% by mass or more, cracking of the metal layer after compression can be further suppressed when the conductive particles 2 and 12 are compressed and bonded by high pressure. The upper limit of the total of the nickel content and the copper content is 100% by mass.

The thickness of the second part 208b is preferably in the range of 20 to 500 Å (2 to 50 nm), more preferably in the range of 20 to 400 Å (2 to 40 nm), and in the range of 20 to 200 Å (2 to 20 nm). more preferable If the thickness of the second portion 208b is less than 20 Å (2 nm), it tends to agglomerate during plating, and if it exceeds 500 Å (50 nm), in the case of press-connecting the conductive particles 2 and 12 with high compression, nickel There is a tendency for metal cracking to occur easily in the portion containing.

The third part 208c has copper as a main component. The copper content in the third portion 208c is preferably 97% by mass or more, preferably 98.5% by mass or more, and more preferably 99.5% by mass or more. When the content of copper is 97% by mass or more, in the case where the conductive particles 2 and 12 are subjected to high compression and press bonding, cracking of the metal layer after compression can be further suppressed. The upper limit of content of copper is 100 mass %.

The thickness of the third portion 208c is preferably in the range of 100 to 2000 Å (10 to 200 nm), more preferably in the range of 200 to 1500 Å (20 to 150 nm), and in the range of 300 to 1000 Å (30 to 100 nm). more preferable When the thickness of the third portion 208c is 100 Å (10 nm) or more, the conductivity can be maintained satisfactorily, and when the thickness is 2000 Å (200 nm) or less, aggregation of conductive particles during plating can be suppressed.

The first part 208a, the second part 208b, and the third part 208c are preferably all formed by electroless plating containing nickel, copper, and formaldehyde, and in one drying bath. It is more preferable that it is formed sequentially in the electroless plating solution. By sequentially forming a plurality of layers in one drying bath, it is possible to maintain good adhesion between the respective layers.

The electroless plating solution for continuously producing the first portion 208a, the second portion 208b, and the third portion 208c with the same electroless plating solution is, for example, (a) water-soluble copper such as copper sulfate. A salt, (b) a water-soluble nickel salt such as nickel sulfate, (c) a reducing agent such as formaldehyde, (d) a complexing agent such as Rochelle salt and EDTA, and (e) a pH adjuster such as alkali hydroxide are preferably added.

In order to form the first layer 200 containing nickel and copper on the surface of the resin particle 203 by electroless plating, for example, a palladium catalyst is applied to the surface of the resin particle 203, and then, It is preferable to form a plated film by performing electroless plating. As a specific method of forming the first portion 208a, the second portion 208b, and the third portion 208c by electroless plating, for example, (a) a water-soluble copper salt such as copper sulfate, (b) sulfuric acid A water-soluble nickel salt such as nickel, (c) a reducing agent such as formaldehyde, (d) a complexing agent such as Rochelle salt, EDTA, and (e) a pH adjuster such as alkali hydroxide, and a dry bath liquid, to which a palladium catalyst is applied. Resin particles is added to form the first part 208a and the second part 208b, after which (a) a water-soluble copper salt such as copper sulfate, (c) a reducing agent such as formaldehyde, (d) Rochelle salt, EDTA, etc. The third portion 208c can be formed by replenishing a replenishing liquid to which a complexing agent and (e) a pH adjuster such as an alkali hydroxide are added.

(a) water-soluble copper salts such as copper sulfate, (b) water-soluble nickel salts such as nickel sulfate, (c) reducing agents such as formaldehyde, (d) complexing agents such as Rochelle salts and EDTA, and (e) pH such as alkali hydroxides The concentration of (b) water-soluble nickel salt such as nickel sulfate in the dry bath liquid to which the conditioner is added is preferably 0.0005 to 0.05 mol/L, more preferably 0.001 to 0.03 mol/L, and 0.005 to 0.02 mol/L. more preferable (b) When the concentration of a water-soluble nickel salt such as nickel sulfate is lower than 0.0005 mol/L, the palladium catalyst on the surface of the resin particles 203 cannot be covered with a nickel plating film, and the site where copper precipitates on the palladium catalyst It becomes easy to come out partially, and it becomes easy for particles to aggregate, and a part of the surface of the resin particle 203 tends to generate a part where metal is not precipitated. (b) When the concentration of a water-soluble nickel salt such as nickel sulfate is higher than 0.05 mol/L, as the concentration of nickel increases, the activity of the liquid increases and aggregation of the particles tends to occur.

(a) water-soluble copper salts such as copper sulfate, (b) water-soluble nickel salts such as nickel sulfate, (c) reducing agents such as formaldehyde, (d) complexing agents such as Rochelle salts and EDTA, and (e) pH such as alkali hydroxides The concentration of water-soluble copper salt such as (a) copper sulfate in the dry bath liquid to which the conditioner is added is preferably 0.0005 to 0.05 mol/L, more preferably 0.001 to 0.03 mol/L, and still more preferably 0.005 to 0.02 mol/L. desirable. (a) When the concentration of a water-soluble copper salt such as copper sulfate is lower than 0.0005 mol/L, the formation of the second part 208b or the third part 208c tends to become non-uniform. (a) When the concentration of a water-soluble copper salt such as copper sulfate is higher than 0.05 mol/L, the activity of the liquid increases due to the increase in the concentration of copper, and aggregation of particles easily occurs.

By simultaneously including (a) a water-soluble copper salt such as copper sulfate and (b) a water-soluble nickel salt such as nickel sulfate in the electroless plating solution, the first portion 208a and the second portion 208b are successively formed by the same electroless plating solution. can be made with The reason is considered as follows. That is, since nickel is precipitated more preferentially than copper on the palladium catalyst on the surface of the resin by using formaldehyde as a reducing agent, the first portion 208a is formed, and then the second portion 208a is formed outside the first portion 208a. Portion 208b is formed. The concentration ratio of copper to nickel in the second portion 208b tends to increase with the growth of the thickness of the second portion 208b. Nickel is preferentially deposited on the palladium catalyst, and when the palladium catalyst is coated with nickel, copper is also deposited immediately. Therefore, a layer (second portion 208b) containing nickel and an alloy containing copper as a main component is formed. I think it's starting to become. Then, as the thickness of the plated film (third portion 208c) increases, the influence of the palladium catalyst diminishes, so copper precipitation becomes more dominant than nickel precipitation, and as a result, the resin particle 203 side From this, it is considered that the proportion of copper increases in the thickness direction in the plated film.

When the first portion 208a is formed on the surface of the resin particle 203, aggregation of the resin particles 203 can be suppressed compared to the case where the copper plating layer is directly formed on the surface of the resin particle 203. there is. The reason is considered as follows. The process of precipitation of copper from copper ions in electroless copper plating is a reaction in which the valence of copper changes from Cu (2 valence) → Cu (1 valence) → Cu (0 valence), and unstable monovalent copper ions as reaction intermediates. is created When this monovalent copper ion causes a disproportionation reaction, Cu (zero valence) is generated in a plating solution, for example, and it is thought that stability of a liquid becomes very low. On the other hand, the precipitation process from nickel ion to nickel in electroless nickel plating is a reaction in which the valence of nickel changes from Ni (divalent) to Ni (zero valence), and does not go through the process of unstable monovalent nickel ion as a reaction intermediate. don't Therefore, when comparing electroless copper plating and electroless nickel plating on the surface of a palladium catalyst, since the electroless copper plating solution lacks stability and the reaction is violent, agglomeration of particles tends to occur simultaneously with the start of the reaction. On the other hand, as described above, electroless nickel plating is highly stable, and it is considered that it is possible to form a plated film by suppressing aggregation of particles.

In the case where the first layer 200 in the conductive particle 2 is a layer containing nickel and copper in which the total content of nickel and copper is 97 mass% or more, a layer containing 97 mass% or more of copper is used. Pinholes tend to be less likely to occur in the case of using a layer. The present inventors speculate that the reason for this is that, when a layer containing 97% by mass or more of copper is used, the particles aggregate during plating film formation. That is, in the case where the particles aggregate in the initial stage of plating and then separate the particles from each other, the agglomerated portion is not plated in the initial stage, so even if the plated film is grown thereafter, it is not plated, and pinholes are formed. throw away

Then, the reaction of the electroless copper plating on the surface of the resin particle 203 on the surface of the palladium catalyst, the reaction of the second part 208b on the first part 208a, and the second part 208b on the second part 208b. 4 cases of the reaction of the third part 208c and the growth of the third part 208c are compared and considered.

In the reaction of electroless copper plating on the surface of the resin particle 203 on the surface of the palladium catalyst, oxidation of a reducing agent such as formaldehyde tends to proceed on the surface of the palladium catalyst, so the reaction of electroless copper plating tends to proceed and destabilizes. This makes it easier for the particles to agglomerate with each other. On the other hand, in the reaction of the second portion 208b on the first portion 208a, the first portion 208a becomes the surface of the autocatalyst, and the reducing agent is oxidized. Further, in the reaction of the third portion 208c on the surface of the second portion 208b, the second portion 208b becomes the surface of the autocatalyst, and the reducing agent is oxidized. Further, in the growth of the third portion 208c, copper itself serves as the surface of the autocatalyst, and copper growth occurs. Comparing the oxidation reaction of a reducing agent such as formaldehyde on the surface of the first portion 208a, the second portion 208b, and the third portion 208c with the oxidation reaction of a reducing agent such as formaldehyde on the surface of the palladium catalyst , the oxidation reaction of a reducing agent such as formaldehyde on the surface of the first portion 208a, the second portion 208b, and the third portion 208c is more difficult to proceed compared to the surface of the palladium catalyst. Therefore, in the case of electroless copper plating on the surface of a palladium catalyst, aggregation of particles tends to occur, but aggregation of particles is difficult to occur even when an alloy of nickel and copper or a copper film grows.

As the reducing agent for the electroless plating solution used in the present embodiment, a reducing agent such as sodium hypophosphite, sodium borohydride, dimethylamine borane, or hydrazine may be used, but formaldehyde is most preferably used alone. When sodium hypophosphite, sodium borohydride, dimethylamine borane, etc. are added, phosphorus or boron tends to coexist, so that the nickel content in the first part 208a is 97% by mass or more, the concentration is adjusted It is desirable to do By using formaldehyde as a reducing agent, it is easy to form a plated film having a nickel content of 99% by mass or more in the first portion 208a. In this case, when the conductive particles 2 and 12 are compressed and connected by high pressure, it is possible to suppress metal cracking after compression. On the other hand, when the content of nickel in the first portion 208a is lower than 97% by mass, cracking of the metal after compression tends to occur. Moreover, when using reducing agents, such as sodium hypophosphite, sodium borohydride, dimethylamine borane, and hydrazine, it is preferable to use at least 1 sort(s) of these together with formaldehyde.

As the complexing agent of the electroless plating solution used in the present embodiment, for example, amino acids such as glycine, amines such as ethylenediamine and alkylamine, copper complexing agents such as EDTA and pyrophosphoric acid, citric acid, tartaric acid, hydroxyacetic acid, and malic acid , lactic acid, gluconic acid, etc. may be used.

It is preferable to efficiently perform water washing after completion of the electroless copper plating in a short time. Since an oxide film is less likely to form on the copper surface as the water washing time is shorter, subsequent plating tends to be advantageous.

The second layer 202 preferably has a first nickel-containing layer 206 containing nickel and a second nickel-containing layer 207 containing nickel, in order closer to the first layer 200 .

The first nickel-containing layer 206 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 making the content within the above range, when forming the palladium-containing grains on the first nickel-containing layer 206, the shape fluctuation of the palladium-containing grains can be suppressed, and furthermore, the palladium-containing grains are distributed at high density. it becomes easier to do This makes it possible to suppress fluctuations in the shape of the protrusions on the outer surface of the metal layer 204 and to form the protrusions at high density.

The first nickel-containing layer 206 can be formed by electroless nickel plating, for example. In this case, it is preferable to treat the surface of the first layer 200 with palladium catalysis. The palladium catalyzed treatment can be performed by a known method, and the method is not particularly limited. For example, there is a catalytic treatment method using a catalytic treatment liquid called alkali cider or acid cider. In addition, there is also a catalytic treatment method called substitutional palladium plating, and a catalysis treatment method in which copper on the surface of the first layer 200 is dissolved and palladium is deposited by substitution is exemplified.

As a catalytic treatment method using an alkali seeder, there is, for example, the following method. Palladium ions are adsorbed on the surface of the resin particles by immersing the resin particles in a solution of palladium ions coordinated with 2-aminopyridine, and after washing with water, the resin particles to which the palladium ions are further adsorbed are mixed with sodium hypophosphite, sodium borohydride, or dimethylamine borane. , hydrazine, formalin, or the like is dispersed in a reducing agent to perform reduction treatment, and palladium ions adsorbed on the surface of the first layer 200 containing copper or nickel and copper are reduced to metal palladium.

In addition, as a catalytic treatment method using acidic cider, there are, for example, the following methods. The resin particles are dispersed in a stannous chloride solution, 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, activated to capture palladium ions on the surface of the resin particles, and then washed with water. In addition, reducing treatment is performed by dispersing in a solution containing a reducing agent such as sodium hypophosphite, sodium borohydride, dimethylamine borane, hydrazine, formalin, etc., and adsorbed on the surface of the first layer 200 containing copper or nickel and copper. reduced palladium ions to metallic palladium.

In these palladium-catalyzed treatment methods, after adsorbing palladium ions to the surface, washing with water and further dispersing in a solution containing a reducing agent, the palladium ions adsorbed on the surface are reduced to form palladium precipitation nuclei of atomic level size. do.

The first nickel-containing layer 206 preferably contains phosphorus or boron, and more preferably contains phosphorus. As a result, the hardness of the first nickel-containing layer 206 can be increased, and it is easy to keep the electrical resistance value when the conductive particles are compressed low.

When the first nickel-containing layer 206 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 the first nickel-containing layer containing a nickel-phosphorus alloy ( 206) can be formed. In addition, 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 nickel-containing layer 206 containing a nickel-boron alloy can be formed. . Since the nickel-phosphorus alloy has a lower hardness than the nickel-boron alloy, from the viewpoint of suppressing cracking of the first nickel-containing layer 206 when conductive particles are press-connected by high compression, the first nickel-containing layer 206 is a nickel-phosphorus alloy. It is preferable to include a phosphorus alloy.

In addition, the content of the element in the first nickel-containing layer 206 is determined by, for example, cutting out a cross-section of conductive particles by an ultra microtome method and observing it at a magnification of 250,000 times using a transmission electron microscope (hereinafter referred to as TEM). It can be calculated by component analysis using an energy dispersive X-ray detector (hereinafter referred to as EDX) attached to the TEM.

The thickness of the first nickel-containing layer 206 is preferably 2 to 100 nm, more preferably 3 to 50 nm, and still more preferably 5 to 30 nm. By setting the thickness of the first nickel-containing layer 206 to 100 nm or less, destruction (breakage) of the plating film starting from the first nickel-containing layer 206 can be suppressed when the conductive particles are highly compressed. On the other hand, by setting the thickness to 2 nm or more, the surface of the first layer 200 is sufficiently covered with the first nickel-containing layer 206, and the grains 201 containing palladium can be formed uniformly. For this reason, when the thickness of the first nickel-containing layer 206 is within the above range, the shape of the protrusions on the second nickel-containing layer 207 is uniformly formed, and a low connection resistance value is easily obtained, and the conductive particles are highly compressed. Even in the case of crimp connection, it is thought that since cracking of the first nickel-containing layer 206 can be easily suppressed, low conduction resistance can be maintained.

The metal layer 204 contains grains 201 containing palladium. The metal layer 204 preferably contains palladium-containing grains 201 between the first layer 200 and the second layer 202 or within the second layer 202 . In addition, the fact that the metal layer 204 contains the palladium-containing grains 201 between the first layer 200 and the second layer 202 means that the resin particle 203 side of the palladium-containing grains 201 This means that the first layer 200 is present on and the second layer 202 is present on the opposite side of the resin particles 203 of the grains 201 containing palladium (provided that the grains containing palladium ( 201) is contained in the second layer 202). At this time, the first layer 200 and the second layer 202 and the grains 201 containing palladium may or may not be in contact with each other, respectively.

The grains 201 containing palladium are preferably dotted inside the metal layer.

4 and 5 are schematic views showing a part of a cross section when the conductive particle of the present embodiment is cut along a plane passing through the center of the conductive particle. 4 and 5, in order to easily explain the size and position of palladium-containing grains, the cut plane passes through the apex of two adjacent projections, and the cut plane extends around the center of the palladium-containing grains. A cross-section of the case is shown.

The length D1 of the grain 201 containing palladium in the thickness direction of the metal layer 204 is preferably 4 nm or more, more preferably 6 nm or more, still more preferably 8 nm or more. When grains containing palladium having a length within the above range are included in the metal layer, it is easy to form protrusions having a sufficient height on the outer surface of the metal layer. Further, from the viewpoint that grains containing palladium are interspersed and protrusions of sufficient height are easily formed on the outer surface of the metal layer, D1 is preferably 35 nm or less, and more preferably 25 nm or less.

In order to obtain the length (D1) of the palladium-containing grains, first, a sample in the shape of a thin film section is prepared by an ultra microtome method, a convergent ion beam processing method, a cryo-ultramicrotome processing method, etc. 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 palladium mapping diagram obtained by EDX attached to the TEM.

In the present embodiment, when the conductive particles are cut with a plane passing through the center of the particles, the average length of the palladium-containing particles identified by the above method is preferably 4 to 35 nm, and preferably 6 to 25 nm. It is more preferable, and it is still more preferable that it is 12 to 20 nm. The number of particles to be averaged can be set to 10.

In this embodiment, it is preferable that the metal layer 204 contains palladium-containing grains having a shortest distance to the interface between the metal layer and the resin particles of 0.1 x d or more when the average thickness of the metal layer 204 is d. Do. That is, the shortest distance D2 between the surface S1 of the resin particle 203 side of the grain 201 containing palladium shown in FIG. 4 and the interface S2 between the metal layer 204 and the resin particle 203 It is preferable that is 0.1 × d or more. Also, a broken line H1 in FIG. 4 represents the average thickness of the metal layer 204 .

Between the grains 201 containing palladium and the resin particles 203, there is a first layer 200 of 0.1×d or more, or a metal layer including the first layer 200 and the first nickel-containing layer 206. By doing so, it becomes possible to easily form grains 201 containing palladium having a length of 4 nm or more in the thickness direction of the metal layer. That is, by the existence of a metal layer of 0.1×d or more, the reducing agent is adsorbed on the metal layer including the first layer 200 or the first nickel-containing layer 206, and the oxidation reaction of the reducing agent, that is, the reduction reaction of palladium ions Since this proceeds continuously, it is possible to grow grains containing palladium. As a result, palladium-containing grains 201 having a length of 4 nm or more in the thickness direction of the metal layer can be grown, and protrusions 205 are formed on the outer surface of the second nickel-containing layer 207 provided thereon. Thus, conductive particles capable of obtaining low conduction resistance are obtained.

In addition, it is difficult to form grains 201 containing palladium with a length of 4 nm or more on the surface of the resin particle 203 . The grains 201 containing palladium with a length of 4 nm or more are formed by reducing and depositing them with an electroless palladium plating solution containing palladium ions and a reducing agent. Even if it is attempted to form the grains containing palladium described above, the reducing agent is difficult to adsorb on the surface of the resin particle 203, and the oxidation reaction of the reducing agent does not proceed, so it is difficult to make the grains containing palladium larger. The size of the palladium precipitation nucleus at this time is considered to be at the atomic level, and even if the second nickel-containing layer 207 is formed thereon, for example, it becomes a smooth film, and since a shape having projections cannot be formed, low conduction resistance can be achieved. can't get

In contrast, in the present embodiment, it is possible to form grains 201 containing palladium with a length of 4 nm or more on the first layer 200 or on the metal layer including the first nickel-containing layer 206 . Compared to the surface of the resin particles 203, since copper, or the first layer 200 containing nickel and copper, and the first nickel-containing layer 206 are metal surfaces, the reducing agent is easily adsorbed on the surface, and the reducing agent is oxidized. It is thought that since the reaction proceeds, it becomes possible to make grains containing palladium large.

Comparing the formation of the palladium-containing grains 201 on the first layer 200 and the palladium-containing grains 201 on the metal layer including the first nickel-containing layer 206, From the viewpoint of the uniformity of the precipitation properties of the palladium precipitation nuclei, the metal layer phase including the first nickel-containing layer 206 has higher uniformity, and the uniformity of the protrusion shape after forming the second nickel-containing layer 207 is higher. Therefore, since it is easy to obtain a stably low conduction resistance, it is preferable to form the grain 201 containing palladium on the metal layer containing the 1st nickel containing layer 206.

In addition, in order to control the size of the projections on the entire surface of one conductive particle to a certain extent, further reduce the variation in the shape of the projections among the conductive particles, and obtain a stable low conduction resistance even between the conductive particles, It is more preferable that the said D2 is 0.2xd or more, and it is still more preferable that it is 0.4xd or more. Further, in order to obtain a low conduction resistance value and high insulation reliability, the D2 is preferably 0.7 x d or less, and more preferably 0.4 x d or less.

In addition, the average thickness (d) of the metal layer 204 is determined by cutting a cross-section of the particle with an ultra microtome method so as to pass through the center of the particle, observing it at a magnification of 250,000 times using TEM, and from an image obtained, the metal layer ( 204) is estimated and calculated from its cross-sectional area.

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

In addition, the metal layer including the first layer 200 including copper or nickel and copper, or the first layer 200 including copper or nickel and copper and the first nickel-containing layer 206 may be formed in a pin hole or the like. When the continuous film is formed and the resin particles are completely covered by the metal film, grains 201 containing palladium of 4 nm or more are formed on the entire conductive particle, and protrusions in the second nickel-containing layer containing nickel are formed. Since it is entirely formed from one conductive particle, it becomes possible to obtain a lower conduction resistance value. For this reason, the D2 is preferably 10 nm or more, more preferably 20 nm or more, and still more preferably 40 nm or more.

In this embodiment, it is preferable that the metal layer 204 contains palladium-containing grains having a diameter D3 of 5 to 100 nm in a direction orthogonal to the thickness direction of the metal layer. When the size of the palladium-containing grains is within the above range, projections of a sufficient size and sufficient density are easily formed on the outer surface of the metal layer. From this point of view, D3 is more preferably 7 to 80 nm, and even more preferably 20 to 60 nm.

The number of palladium-containing grains with a diameter of 20 to 60 nm is preferably 50% or more, more preferably 60% or more, and still more preferably 70% or more, relative to the total number of palladium-containing grains with a length of 4 nm or more. Do.

Further, the ratio [D1/D3] of the length (D1) of the grains containing palladium in the thickness direction of the metal layer and the diameter (D3) in the direction orthogonal to the thickness direction of the metal layer is preferably 0.1 or more, and 0.2 or more. It is more preferable, and it is still more preferable that it is 0.3 or more. By incorporating particles within the above range into the metal layer, it is possible to easily control the shape of the projections formed on the outer surface of the metal layer.

The grains containing palladium are preferably included within ±45% of the average thickness relative to the center of the average thickness of the metal layer. In the cross section of the conductive particle shown in FIG. 5 , the broken line C1 indicates the center of the average thickness of the metal layer 204, and the metal layer 204 is formed at a distance of d/2 from the broken line C1 in the thickness direction of the metal layer. A plane of average thickness and a surface of resin particles are located. In this case, it is preferable that the grains 201 containing palladium exist within a range of ±0.45×d from C1. After formation of the second nickel-containing layer containing nickel, in order to suppress the shape variation of the protrusions and obtain a low conduction resistance value and high insulation reliability, the grains 201 containing palladium are placed within a range of ±0.3×d from C1. It is more preferable that it exists, and it is more preferable that it exists within the range of ±0.2×d.

The number of palladium-containing grains of the conductive particles is preferably 20 or more, more preferably 60 or more, within a concentric circle having a diameter of 1/2 of the diameter of the conductive particles on the SEM orthographic projection plane of the conductive particles. and more preferably 100 or more. When the number of grains containing palladium is within the above range, a sufficient number of protrusions may be formed on the outer surface of the metal layer. This makes it possible to obtain a lower electrical resistance value when the electrodes are bonded to each other by means of electrically conductive particles passing between the opposing electrodes.

In the conductive particle of the present embodiment, from the viewpoint of forming a sufficient number of projections on the outer surface of the metal layer and further lowering the electrical resistance value upon connection, palladium-containing grains are dotted in a direction orthogonal to the thickness direction of the metal layer. It is desirable to do It is preferable that the grains containing palladium are dotted in a direction orthogonal to the thickness direction of the metal layer without contacting each other. The number of palladium-containing grains in contact with each other is preferably 15 or less in one conductive particle, more preferably 7 or less, and 0, that is, all of the palladium-containing grains are dotted without contacting each other. it is more preferable

Further, in the conductive particle of the present embodiment, the metal layer preferably contains palladium-containing grains through which a straight line connecting the apex of the projection formed on the outer surface of the metal layer and the interface between the metal layer and the resin particle in the shortest way passes. Do. In the cross section of the conductive particle shown in FIG. 5 , L1 is a straight line connecting the apex T1 of the projection and the interface S2 of the resin particle 203 and the metal layer 204 as the shortest. The metal layer 204 shown in FIG. 5 contains grains 201 containing palladium through which L1 is connected. In this way, it is preferable that the projections of the metal layer are formed at positions corresponding to the grains containing palladium, but projections may be formed at positions where L1 does not pass through the grains containing palladium, or they may be mixed. .

In addition, as to whether or not the metal layer contains palladium-containing grains through which the above-mentioned straight line L1 passes, for example, the conductive particle is cut at a cut surface where the vicinity of the center of the conductive particle and the apex of the projection pass through, and the cross section thereof It can be confirmed in the mapping diagram of palladium obtained by EDX of

In the conductive particles according to the present embodiment, the ratio of the area of the palladium-containing grains covering the first layer 200 containing copper or nickel and copper, or the first nickel-containing layer 206 ( coverage) is preferably 1 to 70%, more preferably 3 to 50%, still more preferably 5 to 30%. When the coverage is within the above range, it is easy to obtain a good projection shape on the outer surface of the metal layer. This makes it possible to obtain a lower electrical resistance value when the electrodes are bonded to each other by means of electrically conductive particles passing between the opposing electrodes.

The shape of the palladium-containing grains is not particularly limited, but is preferably ellipsoidal, spherical, hemispherical, approximately ellipsoidal, approximately spherical, approximately hemispherical or the like. Among these, hemispheres or substantially hemispherical ones are preferable.

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

The source of palladium used in the electroless palladium plating solution is not particularly limited, but includes palladium compounds such as palladium chloride, sodium palladium chloride, palladium ammonium chloride, palladium sulfate, palladium nitrate, palladium acetate, and palladium oxide. Specifically, acid palladium chloride “PdCl ₂ /HCl”, tetraamine palladium nitrate “Pd(NH ₃ ) ₄ (NO ₃ ) ₂ ”, dinitrodiamine palladium “Pd(NH ₃ ) ₂ (NO ₂ ) ₂ ”, DC Anodiamine palladium "Pd(CN) ₂ (NH ₃ ) ₂ ", dichlorotetraamine palladium "Pd(NH ₃ ) ₄ Cl ₂ ", palladium sulfamic acid "Pd(NH ₂ SO ₃ ) ₂ ", diamine palladium sulfate "Pd (NH ₃ ) ₂ SO ₄ ”, tetraamine oxalate palladium “Pd(NH ₃ ) ₄ C ₂ O ₄ ”, palladium sulfate “PdSO ₄ ”, etc. can be used.

The reducing agent used in the electroless palladium plating solution is not particularly limited, but it is preferable to use a formic acid compound from the viewpoint of sufficiently increasing the palladium content in the obtained palladium-containing grains and suppressing the shape variation of the grains. . Moreover, as a reducing agent, phosphorus-containing compounds or boron-containing compounds, such as hypophosphorous acid and phosphorous acid, can be used. In that case, since the resulting palladium-containing grains contain a palladium-phosphorus alloy or a palladium-boron alloy, the concentration of the reducing agent, pH, temperature of the plating solution, etc., so that the palladium content in the palladium-containing grains is desired. It is desirable to adjust

Further, a buffer or the like can be added to the electroless palladium plating solution as needed, but the type is not particularly limited.

The content of palladium in grains containing palladium is preferably 94% by mass or more, more preferably 97% by mass or more, and even more preferably 99% by mass or more. When the content of palladium in the palladium-containing grains is within the above range, the size and number of protrusions formed on the outer surface of the metal layer can be set to a more favorable range. This makes it possible to obtain a lower electrical resistance value when the electrodes are bonded to each other by means of electrically conductive particles passing between the opposing electrodes.

In addition, the content of the elements in the grains containing palladium is determined by, for example, cutting out the cross section of the conductive particle by the ultra microtome method, observing it at a magnification of 250,000 times using a TEM, and analyzing the element by EDX attached to the TEM. can be calculated by

Further, when the grains containing palladium are formed by the above-mentioned reduction precipitation, in the component analysis by EDX of the electroless palladium plating film obtained by the method using a copper-clad laminate described later, the palladium content is within the above range, It is preferable to set conditions for reduction precipitation.

In the conductive particles 12 according to the present embodiment, protrusions 205 are formed on the outer surface of the second nickel-containing layer 207 (surface opposite to the resin particle side). This second nickel-containing layer 207 can be formed by electroless nickel plating. In this embodiment, by performing electroless nickel plating on the first layer 200 and the grains 201 containing palladium, or on the first nickel-containing layer 206 and the grains 201 containing palladium, A second nickel-containing layer 207 having protrusions 205 on an outer surface may be formed.

The second nickel-containing layer 207 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 within the above range, when the second nickel-containing layer 207 is formed by electroless nickel plating, aggregation of nickel particles can be easily suppressed, and formation of abnormal protrusions can be prevented. This makes it easier to obtain conductive particles capable of achieving both low conduction resistance and high insulation reliability when used as conductive particles incorporated in an anisotropic conductive adhesive.

In addition, the content of elements in the second nickel-containing layer 207 can be determined by, for example, cross-sections of conductive particles cut out by an ultramicrotome method, observed at a magnification of 250,000 times using a TEM, and EDX attached to the TEM. It can be calculated by component analysis.

The average thickness of the second nickel-containing layer 207 is preferably 10 to 200 nm, more preferably 20 to 160 nm, and even more preferably 40 to 130 nm. When the thickness of the second nickel-containing layer 207 is within the above range, it is possible to form protrusions of good shape, and cracking of the metal layer is less likely to occur even when the conductive particles are highly compressed during compression connection.

The sum of the average thicknesses of the first nickel-containing layer 206 and the second nickel-containing layer 207 is preferably 2 times or less, more preferably 1.6 times or less, and 1.2 times or less of the average thickness of the first layer 200. it is more preferable When the sum of the average thicknesses of the first nickel-containing layer 206 and the second nickel-containing layer 207 is less than twice the average thickness of the first layer 200, and the conductive particles are highly compressed, the ductility due to copper effect can be maintained.

The average thickness of the second nickel-containing layer 207 is an image obtained by cutting a cross-section of the obtained conductive particle by an ultra microtome method so as to pass near the center of the particle, and observing it at a magnification of 250,000 times using a TEM. From this, the cross-sectional area of the second nickel-containing layer 207 can be estimated and calculated from the cross-sectional area. If it is difficult to distinguish the first layer 200, the palladium-containing grains 201, the first nickel-containing layer 206, and the second nickel-containing layer 207, component analysis by EDX determines the By clarifying the distinction, the average thickness of only the second nickel-containing layer 207 can be calculated.

The average height of the protrusions formed by the second nickel-containing layer 207 is preferably 20 to 130 nm, more preferably 30 to 120 nm, still more preferably 40 to 110 nm. When the average height of the protrusions is within the above range, it is easy to obtain conductive particles capable of achieving both low conduction resistance and high insulation reliability when used as conductive particles incorporated in an anisotropic conductive adhesive.

In addition, the height of a projection refers to D4 shown in FIG. 5 and is the distance from a straight line connecting the valleys on both sides of the projection to the apex of the projection. The average height D4 of the protrusions can be calculated as an average value of D4 among 10 conductive particles.

In the present embodiment, in the projections 205, the proportion of projections having a height of less than 30 nm is less than 80% of the total number of projections, and the proportion of projections having a height of 30 nm or more and less than 120 nm is 20 to 80% of the total number of projections. , It is preferable that the ratio of the number of projections having a height of 120 nm or more is 5% or less with respect to the total number of projections, the ratio of projections having a height of less than 30 nm is less than 60% with respect to the total number of projections, and the ratio of projections having a height of 30 nm or more and less than 120 nm is It is 40 to 70% with respect to the total number of projections, and it is more preferable that the proportion of projections having a height of 120 nm or more is 2% or less with respect to the total number of projections. Conductive particles having a distribution of protrusion heights within the above range can achieve both low conduction resistance and high insulation reliability at a higher level when used as conductive particles incorporated in an anisotropic conductive adhesive.

In the projections 205, the proportion of projections having an outer diameter of less than 100 nm is less than 80% of the total number of projections, the proportion of projections having an outer diameter of 100 nm or more and less than 200 nm is 20 to 80% of the total number of projections, and the outer diameter is 200 nm. It is preferable that the ratio of projections with an ideal diameter is 10% or less with respect to the total number of projections, the proportion of projections with an outer diameter of less than 100 nm is less than 60% with respect to the total number of projections, and the proportion of projections with an outer diameter of 100 nm or more and less than 200 nm is relative to the total number of projections It is 40 to 70%, and it is more preferable that the ratio of protrusions with an outer diameter of 200 nm or more is 5% or less with respect to the total number of protrusions. Conductive particles having a distribution of outer diameters of the protrusions within the above range can achieve both low conduction resistance and high insulation reliability at a higher level when used as conductive particles mixed with an anisotropic conductive adhesive.

In addition, the outer diameter of a projection refers to D5 shown in FIG. 5, and for a projection existing in a concentric circle having a diameter of 1/2 of the diameter of the conductive particle on the orthographic projection surface of the conductive particle, the area of the valley outline of the projection is defined as It means the average value of diameters calculated when measured and the area is regarded as the area of a circle. Specifically, conductive particles are observed at a magnification of 30,000 by SEM, and based on the obtained SEM image, the outline of the projection is calculated by image analysis, the area of each projection is calculated, and the outer diameter of the projection is calculated from the average value. can be saved

Further, the number of protrusions is preferably in the range of 50 to 200, more preferably in the range of 70 to 170, within a concentric circle having a diameter of 1/2 of the diameter of the conductive particles on the orthographic projection surface of the conductive particles, and 90 to 150 are more preferred. In this case, even if the height of all the protrusions is less than 50 nm, a sufficiently low electrical resistance value can be obtained when the electrodes are pressure-connected with conductive particles through the opposing electrodes.

In the conductive particles according to the present embodiment, the ratio (coverage) of the area of the protrusions covering the outer surface of the conductive particles is preferably 60% or more, more preferably 80% or more, and even more preferably 90% or more. . If the coverage is within the above range, the electrical resistance value is unlikely to increase even when the conductive particles are exposed to high humidity.

The second nickel-containing layer 207 preferably contains phosphorus or boron. As a result, the hardness of the second nickel-containing layer 207 can be increased, and it is easy to keep the electrical resistance value when the conductive particles are compressed low. In addition, the second nickel-containing layer may contain a metal other than a co-existing metal together with phosphorus or boron. Examples of other metals include metals such as cobalt, copper, zinc, iron, manganese, chromium, vanadium, molybdenum, palladium, tin, tungsten, rhenium, ruthenium, and rhodium. By incorporating these metals into the second nickel-containing layer, the hardness of the second nickel-containing layer can be increased, and when the conductive particles are press-connected by high compression, crushing of the protrusions can be suppressed and a lower electrical resistance value can be obtained. do. Along with phosphorus or boron, among other metals that coexist, tungsten itself is preferred because of its high hardness. In this case, the content of nickel in the second nickel-containing layer is preferably 85% by mass or more.

When the second nickel-containing layer is formed by electroless nickel plating, for example, by using a phosphorus-containing compound such as sodium hypophosphite as a reducing agent, phosphorus can be co-deposited and the second nickel-containing layer containing a nickel-phosphorus alloy. can form Further, as a reducing agent, for example, by using a boron-containing compound such as dimethylamine borane, sodium borohydride, or potassium borohydride, boron can be co-deposited, and a second nickel-containing layer containing a nickel-boron alloy can be formed. . Since the nickel-boron alloy has a higher hardness than the nickel-phosphorus alloy, from the viewpoint of suppressing collapse of projections and obtaining a lower electrical resistance value when conductive particles are press-connected by high compression, the second nickel-containing layer is It is preferable to include a boron alloy.

In this embodiment, it is preferable that the 1st nickel containing layer 206 contains a nickel-phosphorus alloy, and the 2nd nickel containing layer 207 contains a nickel-boron alloy. According to this combination, cracking of the metal layer can be suppressed while suppressing collapse of the protrusions, and a low electrical resistance value can be more stably obtained when the conductive particles are compressed and connected by high compression.

In this embodiment, the first nickel-containing layer 206 and the second nickel-containing layer 207 are preferably formed by electroless nickel plating. The electroless nickel plating solution may contain a water-soluble nickel compound, and preferably further contains at least one compound selected from a complexing agent, a reducing agent, a pH adjuster, and a surfactant.

As a water-soluble nickel compound, 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, can be used, for example. 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, more preferably 0.01 to 0.3 mol/L. By setting the concentration of the water-soluble nickel compound within the above range, it is possible to increase the uniformity of nickel deposition by suppressing the viscosity of the plating solution from becoming too high while sufficiently obtaining the deposition rate of the plating film.

Examples of the complexing agent include ethylenediaminetetraacetic acid, sodium (1-, 2-, 3- and 4-sodium) salts of ethylenediaminetetraacetic acid, ethylenediaminetriacetic acid, nitrotetraacetic acid and alkali salts thereof, and glycolic acid. , tartaric acid, gluconate, citric acid, gluconic acid, succinic acid, pyrophosphoric acid, glycolic acid, lactic acid, malic acid, malonic acid, and triethanolamine gluconate (γ)-lactone. Not limited. In addition, 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 its type and is not particularly limited, but is usually preferably 0.001 to 2 mol/L, more preferably 0.002 to 1 mol/L. By setting the concentration of the complexing agent within the above range, a sufficient rate of deposition of the plated film can be obtained while suppressing precipitation of nickel hydroxide in the plating solution and decomposition of the plating solution, and furthermore, suppressing the viscosity of the plating solution from becoming too high, improving the uniformity of nickel deposition. can be raised

As the reducing agent, known reducing agents used in electroless nickel plating solutions can be used, and examples thereof include hypophosphorous acid compounds such as sodium hypophosphite and potassium hypophosphite, boron hydride compounds such as sodium borohydride, potassium borohydride, and dimethylamine borane. , hydrazines.

The concentration of the reducing agent varies depending on its type and is not particularly limited, but is usually preferably 0.001 to 1 mol/L, 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 rate of reduction of nickel ions in the plating solution.

Among the pH adjusting agents, examples of acidic pH adjusting agents include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, formic acid, iron compounds such as cupric chloride and ferric sulfate, alkali metal chlorides, ammonium persulfate, or these Aqueous solutions containing one or more of them, or aqueous solutions containing acidic hexavalent chromium, such as chromic acid, chromic acid-sulfuric acid, chromic acid-hydrofluoric acid, dichromic acid, and dichromic acid-boric acid, are exemplified. Examples of the alkaline pH adjusting agent include solutions containing at least one compound containing an amino group, such as hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, and sodium carbonate, ethylenediamine, methylamine, and 2-aminoethanol. can

As the surfactant, it is possible to use, for example, cationic surfactants, anionic surfactants, amphoteric surfactants, nonionic surfactants, or mixtures thereof.

In the conductive particle of the present embodiment, the metal layer is made of a noble metal such as palladium, rhodium, iridium, ruthenium, osmium, white gold, silver, gold, etc. on the side opposite to the first layer 200 of the second layer 202 You may further contain the 3rd layer containing it. Among these, palladium, rhodium, ruthenium, platinum, and gold are preferred because they are easily electroless-plated, and palladium and gold are particularly preferred because of their high plating solution stability and ease of plating.

The layer containing palladium can function as an oxidation prevention layer of nickel. Therefore, it is preferable to provide the third layer on the second layer. Moreover, it is preferable that it is 5-100 nm, and, as for the thickness of a 3rd layer, it is more preferable that it is 10-30 nm. When the thickness of the third layer is within the above range, the uniformity of the layer can be increased when the third layer is formed by plating or the like, and the nickel included in the second layer is equal to the second layer of the third layer containing palladium. can effectively function as a layer preventing diffusion to the surface on the opposite side.

The third layer can be formed by palladium plating, for example, and is preferably a palladium layer formed by electroless palladium plating. Electroless palladium plating may use either a substitution type without using a reducing agent or a reduced type using a reducing agent. Examples of such an electroless palladium plating solution include MCA (manufactured by World Metal Co., Ltd., trade name) as a substitution type, and APP (manufactured by Ishihara Chemical Kogyo Co., Ltd., trade name) and the like as a reduced type. When the substitution type and the reduced type are compared, the reduced type is preferable because there are few voids and it is easy to secure a covered area.

In the conductive particle of this embodiment, the metal layer may further contain a fourth layer containing gold on the opposite side of the second layer to the first layer. Further, the fourth layer containing gold may be formed on the layer containing palladium formed as the third layer.

The layer containing gold can lower the electrical resistance value on the surface of the conductive particle and further improve the characteristics of the conductive particle. From this point of view, it is preferable that the fourth layer is the outermost layer of the metal layer. In this case, the thickness of the fourth layer 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, there is no problem in terms of characteristics. In addition, when a function as an antioxidant layer of nickel is expected, it is preferable to provide the 4th layer on the 2nd layer. It is preferable that the thickness of the 4th layer in this case is 10 nm - 100 nm.

The fourth layer can be formed by gold plating, for example. As the gold plating solution, for example, a substitution type gold plating solution such as HGS-100 (manufactured by Hitachi Chemical Co., Ltd., trade name), a reduced type gold plating solution such as HGS-2000 (manufactured by Hitachi Chemical Co., Ltd., trade name), etc. can be used. there is. When the substitution type and the reduced type are compared, the reduced type is preferable because there are few voids and it is easy to secure a covered area.

The conductive particles according to the present embodiment preferably have an average particle diameter of 1 to 10 μm, more preferably 2 to 5 μm. By setting the average particle diameter of the conductive particles within the above range, when a bonded structure is produced using an anisotropic conductive adhesive containing conductive particles, it becomes less susceptible to the influence of height variation of the electrode. The average particle diameter of the conductive particles in the present embodiment is obtained by measuring the particle diameter of 300 random conductive particles by observation using an SEM and taking the average value thereof. In addition, since the conductive particles according to the present embodiment have projections, 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 copper or nickel and copper on the surface of a resin particle by electroless plating; (2) on the first layer; A step of forming grains containing palladium by reducing precipitation of an electroless palladium plating solution containing palladium ions and a reducing agent, and (3) electroless nickel plating on the first layer and the grains containing palladium to form nickel. It is provided with the process of forming the 2nd layer containing.

Further, the method for producing conductive particles of the present embodiment includes (1) a step of forming a first layer containing copper or nickel and copper on the surface of the resin particle by electroless plating; (2) a first layer; By electroless nickel plating on the layer, a step of forming a first nickel-containing layer containing nickel, and (2) reduction precipitation of an electroless palladium plating solution containing palladium ions and a reducing agent on the first nickel-containing layer, Manufacturing comprising a step of forming grains containing palladium, and (3) a step of forming a second nickel-containing layer containing nickel on the first nickel-containing layer and on the grains containing palladium by electroless nickel plating. It may be a method.

The present inventors speculate as follows as to why conductive particles capable of maintaining a low electrical resistance value even when subjected to high compression are obtained by the method according to the present embodiment. By forming the first layer containing copper with high ductility or nickel and copper, it is possible to suppress breakage (breakage) in the plated film even when subjected to high compression, and furthermore, the second layer having projections on the outermost layer. It is considered that by forming and electrically connecting this portion to the electrode, it is possible to maintain a low electrical resistance value even when high compression is applied. Further, even if breakage (rupture) occurs partially in the second layer containing nickel (or the first nickel-containing layer and the second nickel-containing layer), copper having high ductility or nickel and copper is applied to the side close to the resin particles. It is thought that destruction (breakage) does not occur because there is a first layer containing the first layer. As a result, when the electrode and the second layer containing nickel are connected, electricity can flow inside the copper or inside the first layer containing nickel and copper, even in the case of high compression (compression rate: 80%). I think it is possible to keep the low electrical resistance value.

In addition, according to the above manufacturing method, the number, size and shape of the protrusions formed on the second layer containing nickel, particularly the second nickel-containing layer, can be highly controlled, and low conduction resistance and high insulation reliability are compatible. conductive particles can be obtained.

In addition, the present inventors estimate as follows as to the reason why conductive particles capable of achieving both low electrical resistance and high insulation reliability are obtained by the method according to the present embodiment. When granulated particles containing palladium on the first layer 200 or the first nickel-containing layer 206 are immersed in an electroless nickel plating solution for forming the second nickel-containing layer, the reducing agent contained in the plating solution first It is thought that the palladium-containing grains are preferentially oxidized to release electrons rather than the layer 200 or the first nickel-containing layer 206. As a result, nickel is preferentially deposited on the palladium-containing grains rather than the first layer 200 or the first nickel-containing layer 206, and after nickel is deposited in a projection shape on the palladium-containing grains, the first Precipitation of nickel is thought to occur in a portion of the layer 200 or the first nickel-containing layer 206 where no grains containing palladium exist. In this way, the time difference between the start of precipitation of nickel on the first layer 200 or the first nickel-containing layer 206 can be provided, thereby making it possible to form a second nickel-containing layer having protrusions with small shape variations, the present inventors said. they estimate

Further, in the conventional palladium-catalyzed treatment described above, projections cannot be formed on the first layer 200 or the first nickel-containing layer 206. As the reason, it is considered that the palladium catalyst nucleus is small. That is, the palladium-catalyzed treatment is (1) sensitization treatment by tin ions, (2) activation treatment for trapping palladium ions in a solution containing an aqueous solution of palladium chloride, (3) reducing palladium ions adsorbed on the surface by a reducing agent. Although reduction treatment is included to precipitate, since these treatments merely reduce palladium ions adsorbed on the surface, it is considered that the palladium catalyst nucleus is of atomic level size. In the method according to the present embodiment, it is possible to obtain palladium-containing grains having a sufficient size by continuously depositing palladium ions in an electroless palladium plating solution with a reducing agent, thereby forming protrusions with small shape variation by the above-described action. It becomes possible to form a second nickel-containing layer having

Regarding the resin particles, the electroless copper plating solution, the electroless nickel/copper plating solution, the electroless palladium plating solution, and the electroless nickel plating used in the method according to the present embodiment, the examples given in the description of the conductive particles of the present embodiment can be used. can In the method according to the present embodiment, the resin particles are preferably subjected to palladium catalyzed treatment from the viewpoint of enhancing the uniformity of the first layer containing copper or nickel and copper. For the palladium-catalyzed treatment at this time, the treatment given in the description of the conductive particle of the present embodiment can be used.

In the method according to the present embodiment, the grains containing palladium are preferably precipitated so that the length in the thickness direction of the first layer 200 or the first nickel-containing layer 206 is 4 nm or more. This length can be adjusted by changing the purity of the nickel in the first nickel-containing layer 206. For example, although the first nickel-containing layer 206 contains phosphorus, the phosphorus content is increased to lower the purity of nickel, and grains containing palladium tend to grow in the thickness direction. Therefore, the nickel content in the first nickel-containing layer 206 is preferably 83 to 98% by mass, and more preferably 85 to 93% by mass, from the viewpoint of being able to sufficiently increase the length of the grains containing palladium. And it is more preferable that it is 86-91 mass %. Further, since the length of the grains containing palladium can be increased as the purity of palladium is increased, the content of palladium in the grains containing palladium is preferably 94% by mass or more, and 97% by mass or more. It is more preferable if it is, and it is more preferable if it is 99 mass % or more.

In the method according to the present embodiment, the grains containing palladium are preferably precipitated so as to be dotted in a direction orthogonal to the thickness direction of the first layer 200 or the first nickel-containing layer 206 . The distribution of grains containing palladium can be adjusted by changing the purity of nickel in the first nickel-containing layer 206 in particular. The first nickel-containing layer 206 contains phosphorus, but similarly to the growth of palladium-containing grains in the thickness direction, the phosphorus content is increased to lower the nickel purity, and on the one hand, the palladium-containing grains are easier to distribute. . Therefore, from the viewpoint of suppressing the shape variation of grains containing palladium, the nickel content in the first nickel-containing layer 206 is preferably 83 to 98% by mass, more preferably 85 to 93% by mass, It is more preferable that it is 86-91 mass %. Further, as the purity of palladium is increased, the variation in shape of the palladium-containing grains can be suppressed, so the content of palladium in the palladium-containing grains is preferably 94% by mass or more, and 97% by mass. It is more preferable in it being more than, and it is especially preferable in being 99 mass % or more. In addition, as described above, as the purity of palladium is increased, the diameter of the grains containing palladium can be increased. The number of palladium-containing grains can be reduced, and it becomes possible to suppress the shape variation of palladium-containing grains having a diameter of 20 nm or more and less than 60 nm.

According to the method for producing conductive particles of the present embodiment, the conductive particles of the present embodiment can be obtained. In the manufacturing method of the conductive particle of this embodiment, it is preferable to perform the said process so that at least one of the above-mentioned conditions for the conductive particle of this embodiment is satisfied.

Next, the insulated-coated conductive particle of the present embodiment will be described. The insulation-coated conductive particles 10 shown in FIG. 1(b) include the conductive particles 2 of the present embodiment and the insulating child particles 1 covering at least a part of the surface of the metal layer 204 of the conductive particles 2. ) is provided.

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

Examples of insulating child particles covering the conductive particles include organic polymer compound fine particles and inorganic oxide fine particles. Among them, inorganic oxide fine particles are preferable from the viewpoint of insulation reliability. In addition, in the case of organic polymer compound fine particles, the electrical resistance value tends to be lowered.

The organic polymer compound is preferably one having heat softening properties, and examples thereof include 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, (meth)acrylic acid ester rubber, Styrene-ethylene-butylene copolymers, phenoxy resins, and solid epoxy resins are suitably used. These may be used individually by 1 type, and may be used in combination of 2 or more types.

As the inorganic oxide, an oxide containing at least one element selected from the group consisting of, for example, silicon, aluminum, zirconium, titanium, niobium, zinc, tin, cerium, and magnesium is preferable, and these are used singly or alone. Two or more types may be mixed and used. Among the inorganic oxide fine particles, water-dispersed colloidal silica (SiO ₂ ) is particularly suitable because it has a hydroxyl group on the surface, so it has excellent bonding properties with conductive particles, it is easy to align the particle diameter, and it is inexpensive. Commercially available products of such inorganic oxide fine particles include, for example, Snowtex, Snowtex UP (manufactured by Nissan Chemical Industries, Ltd., trade name), and Cuotron PL series (manufactured by Fuso Chemical Industry Co., Ltd., trade name). .

When the inorganic oxide fine particles have a hydroxyl group on the surface, it is possible to modify the hydroxyl group into an amino group, a carboxyl group, an epoxy group, etc. with a silane coupling agent or the like, but when the average particle diameter of the inorganic oxide fine particles is 500 nm or less, modification may be difficult. In that case, it is preferable to coat the conductive particles without performing denaturation.

Generally, by having a hydroxyl group, it is possible to bond with a hydroxyl group, a carboxyl group, an alkoxyl group, an alkoxycarbonyl group or the like. As a bonding form, a covalent bond by dehydration condensation, a hydrogen bond, a coordination bond, etc. are mentioned, for example.

When the outermost surface of the conductive particle contains gold or palladium, a compound having a mercapto group, sulfide group, disulfide group, etc. forming a coordination bond with them is used in the molecule to form a hydroxyl group, a carboxyl group, an alkoxyl group, A functional group such as an alkoxycarbonyl group can be formed. Examples of the compound include mercaptoacetic acid, 2-mercaptoethanol, methyl mercaptoacetate, mercaptosuccinic acid, thioglycerin, and cysteine.

Noble metals such as gold, palladium, and copper easily react with thiols, and non-metals such as nickel hardly react with thiols. Therefore, when the outermost layer of the conductive particles contains a noble metal, it reacts more easily with thiol than when the outermost layer of the conductive particles contains a non-metal.

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

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

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

The insulating child particle preferably covers the surface of the conductive particle 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%. Incidentally, the coverage here means the ratio of the surface area of insulating child particles in a concentric circle having a diameter of 1/2 of the diameter of the conductive particles on the normal projection surface of the conductive particles. , Observe the conductive particles at a magnification of 30,000, and calculate the ratio occupied by the insulating child particles on the surface of the conductive particles by image analysis based on the obtained SEM image.

Subsequently, as a method of coating the surface of the conductive particles with inorganic oxide fine particles, a method of alternately stacking a polymer electrolyte and inorganic oxide fine particles is preferable, for example. More specifically, (1) dispersing conductive particles in a polymer electrolyte solution, adsorbing the polymer electrolyte on the surface of the conductive particles, followed by rinsing; (2) dispersing conductive particles in a dispersion solution of inorganic oxide fine particles, conducting Insulated-coated conductive particles whose surfaces are covered with insulating child particles in which a polymer electrolyte and inorganic oxide fine particles are laminated can be produced by a production method including a step of rinsing after adsorbing inorganic fine particles on the surface of the particles. This method is called layer-by-layer assembly. The alternating layering method is a method of forming organic thin films published by G. Decher et al. in 1992 (Thin Solid Films, 210/211, p831 (1992)). According to this method, a base material is alternately immersed in an aqueous solution of a polymer electrolyte (polycation) having a positive charge and a polymer electrolyte (polyanion) having a negative charge, and polycations and polyanions adsorbed on the substrate are separated by electrostatic attraction. By stacking the groups, a composite film (alternatively laminated film) is obtained. Steps (1) and (2) may be performed in the order of (1) and (2), or may be in the order of (2) and (1), and it is preferable to alternately laminate a plurality of layers.

In the alternating layering method, the charge of the material formed on the substrate and the material having the opposite charge in the solution are attracted to each other by electrostatic attraction to grow the film, so if adsorption proceeds and charge neutralization occurs, further adsorption does not occur. . Therefore, when a certain saturation point is reached, the film thickness does not increase any more. Lvovs apply the alternating layering method to microparticles and report a method of stacking polymer electrolytes having an opposite charge to the surface charge of the microparticles by using the dispersion liquid of each microparticle, such as silica, titania, and ceria, by the alternating layering method (Langmuir , Vol. 13, (1997) p6195-6203). In this method, silica fine particles and polymers are alternately layered with silica fine particles having a negative surface charge and polydiallyldimethylammonium chloride (PDDA) or polyethyleneimine (PEI), which are polycations having a negative surface charge, and the like. It is possible to form a fine particle laminated thin film in which electrolytes are alternately laminated.

As the polymer electrolyte, for example, a polymer that ionizes 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. As the polycation, those having a functional group that can be positively charged, such as polyamines, for example, polyethyleneimine (PEI), polyarylamine hydrochloride (PAH), polydiallyldimethylammonium chloride (PDDA), polyvinylpyridine (PVP ), polylysine, polyacrylamide, or a copolymer containing one or more of them. Among them, polyethyleneimine is preferable because of its high charge density and strong binding force.

<Anisotropic conductive adhesive>

The anisotropic conductive adhesive of the present embodiment contains the conductive particles of the present embodiment described above, the conductive particles obtained by the manufacturing method of the present embodiment, or the insulated-coated conductive particles of the present embodiment, and the adhesive. It is preferable to use this anisotropic conductive adhesive as an anisotropic conductive adhesive film formed in the form of 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, 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. As the adhesive used preferably, a mixture of an epoxy resin and a latent curing agent and a mixture of a radically polymerizable compound and an organic peroxide are exemplified.

In addition, as an adhesive agent, a paste-like or film-like thing is used. In order to form a film, it is effective to blend a thermoplastic resin such as phenoxy resin, polyester resin, polyamide resin, polyester resin, polyurethane resin, acrylic resin, or polyester urethane resin into the adhesive.

<connection structure>

Next, a bonded structure using the anisotropic conductive adhesive of the present embodiment will be described with reference to FIG. 6 . Fig. 6 is a schematic cross-sectional view showing a connection structure according to the present embodiment. The connection structure 100 shown in FIG. 6 is provided with a 1st circuit member 30 and a 2nd circuit member 40 which oppose each other, and the 1st circuit member 30 and the 2nd circuit member 40 Between them, the connection part 50a which connects 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 a main surface 31a 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 41a of the circuit board 41 .

Specific examples of circuit members include IC chips (semiconductor chips), resistor chips, capacitor chips, chip components such as driver ICs, and rigid package substrates. These circuit members are provided with circuit electrodes, and it is common to have a large number of circuit electrodes. Specific examples of the other circuit member to which the circuit member is connected include a flexible tape board having metal wiring, a flexible printed wiring board, and a wiring board such as a glass substrate on which indium tin oxide (ITO) is deposited. According to the film-form 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 of a chip component having many fine circuit electrodes onto a wiring board.

The connecting portion 50a includes a cured adhesive 20a and insulated-coated conductive particles 10 (or conductive particles 2, the same applies hereinafter) dispersed therein. And in the connection structure 100, the facing circuit electrode 32 and circuit electrode 42 are electrically connected via the insulated-coated conductive particle 10. More specifically, as shown in FIG. 6 , in the case of the insulated-coated conductive particles 10, the conductive particles 2 are deformed (flattened) by compression and electrically connected to both circuit electrodes 32 and 42. there is. On the other hand, in the illustrated horizontal direction, insulation is maintained by interposing the insulating child particles 1 between the conductive particles 2. Therefore, if the anisotropic conductive adhesive of the present embodiment is used, it becomes possible to improve insulation reliability at a narrow pitch of the 10 μm level. In addition, it is also possible to use non-insulated conductive particles instead of the insulated-coated conductive particles depending on the application.

The connection structure 100 of this embodiment comprises the first circuit member 30 having the first circuit electrode 32 and the second circuit member 40 having the second circuit electrode 42, the first circuit electrode 32 and the second circuit electrode 42 are disposed to face each other, the anisotropic conductive adhesive of the present embodiment is interposed between the first circuit member 30 and the second circuit member 40, heated and pressurized, It is obtained by electrically connecting the 1st circuit electrode 32 and the 2nd circuit electrode 42. The first circuit member 30 and the second circuit member 40 are bonded by the cured product 20a of the anisotropic conductive adhesive of the present embodiment.

<Method for manufacturing connection structure>

The manufacturing method of the said connection structure is demonstrated, referring FIG. Fig. 7 is a schematic cross-sectional view for explaining an example of a method for manufacturing the bonded structure shown in Fig. 6 . In this embodiment, an anisotropic conductive adhesive is thermally cured to manufacture a bonded structure.

First, the above-described first circuit member 30 and the anisotropic conductive adhesive 50 (anisotropic conductive adhesive film) molded into a film are prepared. The film-like anisotropic conductive adhesive 50 is formed by containing the insulating coated conductive particles 10 (or the conductive particles 2, as described below) in the insulating adhesive 20 as described above.

Subsequently, the anisotropic conductive adhesive 50 in the form of a film is placed on the surface of the first circuit member 30 on which the circuit electrode 32 is formed. Then, the film-like anisotropic conductive adhesive 50 is pressed in the directions of arrows A and B in (a) of FIG. 7 to laminate the film-like anisotropic conductive adhesive 50 on the first circuit member 30 (FIG. 7 of (b)).

Subsequently, as shown in (c) of FIG. 7 , the second circuit member 40 is bonded to the film-like anisotropic conductive adhesive 50 so that the first circuit electrode 32 and the second circuit electrode 42 are opposed to each other. ) is placed on top. Then, while heating the film-like anisotropic conductive adhesive 50, the whole is pressed in the directions of arrows A and B in Fig. 7(c).

The connection part 50a is formed by hardening of the film-shaped anisotropic conductive adhesive 50, and the connection structure 100 as shown in FIG. 6 is obtained. In addition, in this embodiment, although the anisotropic conductive adhesive 50 was in the form of a film, it may be in the form of a paste.

As a connection structure which has said connection structure, mobile products, such as a liquid crystal display, a personal computer, a mobile phone, a smart phone, and a tablet, are mentioned, for example.

As mentioned above, although preferred embodiment of this invention was described, this invention is not limited in any way to the said embodiment.

[Examples] Hereinafter, the contents of the present invention will be described in more detail by way of Examples and Comparative Examples. In addition, the present invention is not limited to the following examples.

<Example 1> [Production of conductive particles]

(Step a) Pretreatment step 2 g of crosslinked polystyrene particles (manufactured by Nippon Shokubai Co., Ltd., trade name "Sorio Star") with an average particle diameter of 3.0 μm were mixed with palladium catalyst Atotech Neogant 834 (manufactured by Atotech Japan Co., Ltd., trade name) ) was added to 100 mL of a palladium-catalyzed liquid containing 8% by mass, stirred at 30 ° C. for 30 minutes, filtered with a φ 3 μm membrane filter (manufactured by Merck Millipore Co., Ltd.), and washed with water to remove resin particles. got it Thereafter, the resin particles were added to a 0.5% by mass dimethylamine borane solution adjusted to pH 6.0 to obtain resin particles having an activated surface. Thereafter, a resin particle dispersion was obtained by immersing the surface-activated resin particles in 20 mL of distilled water and ultrasonically dispersing the particles.

(Step b) Formation of the first layer (first part, second part, and third part) The resulting resin particles were added to 1 L of a dry bath liquid having the following composition heated to 40 ° C., containing 97 mass% or more of nickel and a second part containing an alloy composed mainly of nickel and copper. Further, 930 mL of replenishment liquid A and replenishment liquid B each containing no nickel of the following composition were prepared by the addition method, and were continuously dropped at a rate of 20 mL/min to form a third portion containing copper as a main component. The thicknesses in the first layer (layers of the first part, the second part and the third part) are shown in Table 1. In addition, the particle|grains obtained by forming the 1st layer were 4g.

(dry bath liquid)

Copper sulfate pentahydrate 7.5g/L

Nickel sulfate hexahydrate 1.3g/L

Formaldehyde 6g/L

Sodium cyanide 5 ppm

Ethylenediaminetetraacetic acid, tetrasodium salt...76 g/L

Sodium hydroxide 12 g/L

pH 12.7

(Supplement A)

Copper sulfate pentahydrate 200g/L

Formaldehyde 30 g/L

Sodium cyanide 50 ppm

(Supplement B)

Ethylenediaminetetraacetic acid, tetrasodium salt ... 380 g/L

Sodium hydroxide 40 g/L

(Step c) Formation of grains containing palladium Next, the entire amount of the particles (4 g) having the first layer formed thereon is immersed in 1 L of an electroless palladium plating solution having the following composition to form grains containing palladium on the surface of the particles. formed. In addition, the reaction time was 10 minutes and the temperature was treated at 60°C. In addition, the particle|grains obtained by forming the grains containing palladium were 4.05 g.

(electroless palladium plating solution)

Palladium chloride・・・・・・・・・・・・・・・・0.07g/L

Ethylenediamine・・・・・・・・・・・・・・0.05g/L

Sodium formate・・・・・・・・・・・・・・・0.2g/L

Tartaric acid・・・・・・・・・・・・・・・・0.11g/L

pH··························7

(Step d) Formation of the second layer (second nickel-containing layer) The entire amount of particles (4.05 g) obtained in step c was 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 was added as a plating stabilizer, and then 50 mL of an electroless nickel plating solution for forming a second layer (second nickel-containing layer) having the following composition was added at a dropping rate of 5 mL/min. Dropped. After completion of the dropwise addition, after 10 minutes had elapsed, the dispersion to which the plating solution was added was filtered, and the filtrate was washed with water and then dried in a vacuum dryer at 80°C. In this way, a second layer (second nickel-containing layer) containing a nickel-phosphorus alloy film having a film thickness of 80 nm shown in Table 1 was formed. In addition, the particle|grains obtained by forming the 2nd layer (2nd nickel containing layer) were 6g.

(Electroless nickel plating solution for forming the second layer (second nickel-containing layer))

Nickel sulfate・・・・・・・・・・・・・・400g/L

Sodium hypophosphite・・・・・・・・・・・・・150g/L

Sodium tartrate・dihydrate・・・・・・・120g/L

Aqueous bismuth nitrate solution (1 g/L)... 1 mL/L

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

[Evaluation of conductive particles] (Evaluation of particles containing palladium)

Regarding the particles after forming the palladium-containing grains in step c, the ratio of the number of palladium-containing grains present in concentric circles having a diameter of 1/2 of the diameter of the particles to the particles having a predetermined diameter Calculated.

Specifically, the number of grains containing palladium was evaluated based on a SEM image obtained by observing the grains at a magnification of 30,000 with a scanning electron microscope (hereinafter referred to as SEM device, manufactured by Hitachi High-Technologies, Inc.). Fig. 8 shows a SEM image obtained by observing the surface of the palladium-containing grains obtained in step c after forming them.

The proportion of palladium-containing grains having a given diameter, relative to the total number of palladium-containing grains present in concentric circles having a diameter of 1/2 of the diameter of the particles, less than 20 nm, greater than or equal to 20 nm, less than 60 nm and 60 nm The ratio of the number of grains containing palladium above was determined. In addition, about the diameter of the grain containing palladium, as shown in FIG. 9, it was discriminated by the SEM image observed at 150,000 times.

The average length in the thickness direction of the metal layer of grains containing palladium was determined in the following procedure. First, cross-sections of particles were cut out using the ultra-microtome method, and among the cut-out samples, samples having the largest particle diameter were cut into cross-sections near the center of the particles. This sample was observed at an accelerating voltage of 200 kV using a scanning transmission electron microscope mode (STEM mode), which is one of the measurement modes of the TEM device, using a TEM device. Next, while observing in the STEM mode, the measurement field was found, and a mapping diagram of nickel, phosphorus, and palladium was obtained by the EDX detector attached to the TEM device (the method of observing in the STEM mode and analyzing with the EDX detector in this way is described below. Abbreviated as "STEM/EDX Analysis"). 11 shows a STEM image of a cross-section of a particle and a mapping diagram of copper, nickel, and palladium corresponding thereto. Then, the length in the thickness direction of the metal layer of the grain containing palladium was calculated|required from the obtained mapping drawing of palladium. FIG. 12 is a diagram for explaining a method for obtaining the length in the thickness direction of the metal layer of grains containing palladium from the palladium mapping diagram of FIG. 11 . Moreover, the length in the thickness direction of the metal layer was calculated|required about 10 grains containing palladium, and those average values were made into the average length of grains containing palladium. Hereinafter, details of a method of preparing a cross-section sample of conductive particles and a method of mapping by an EDX detector will be described.

(Method of producing cross-section samples of conductive particles)

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

In order to stably thin the film, conductive particles were dispersed in the casting resin. Specifically, diethylenetriamine (Refinetech Co., Ltd. product name "Epomount curing agent 27-772") 1.0g was mixed, and it stirred using a spatula, and visually confirmed that it mixed uniformly. After adding 0.5 g of dried conductive particles to 3 g of this mixture and stirring until uniform using a spatula, this was formed into a resin casting mold (manufactured by D.S.K. Tosaka EM Co., Ltd., trade name "Silicon Embedding Board II mold”), and left still at room temperature for 24 hours, confirming that the casting resin had hardened, and obtained a resin casting of conductive particles.

Using an ultra microtome (manufactured by Leica Microsystems, trade name "EM-UC6"), a thin film slice for TEM measurement was produced from a resin cast of conductive particles. When producing a thin film section for TEM measurement, first, a glass knife (manufactured by a glass knife maker manufactured by Nissin EM Co., Ltd.) fixed to the device body of the ultra microtome was used, as shown in FIG. 13(a). , The tip of the resin casting was trimmed until it became a shape in which thin film slices for TEM measurement could be cut out.

More specifically, as shown in FIG. 13(b), trimming was performed so that the cross-sectional shape of the tip of the resin cast was approximately rectangular parallelepiped with a length of 200 to 400 μm and a width of 100 to 200 μm. The reason why the horizontal length of the cross section is 100 to 200 μm is to reduce the friction generated between the diamond knife and the sample when cutting the thin film slice for TEM measurement from the resin cast, thereby reducing the thin film slice for TEM measurement. It becomes easy to prevent wrinkles and bends, and it becomes easy to manufacture thin film slices for TEM measurement.

Next, a diamond knife with a boat attached (manufactured by DIATONE, trade name "Cryo Wet", blade width 2.0 mm, blade angle 35°) was fixed to a predetermined location on the main body of the ultramicrotome device, and the boat was immersed in ion-exchanged water. After filling, the blade tip was wetted with ion-exchanged water by adjusting the installation angle of the knife.

Here, adjustment of the installation angle of a knife is demonstrated using FIG. In adjusting the installation angle of the knife, the angle in the vertical direction, the angle in the left and right directions, and the clearance angle can be adjusted. Adjusting the angle in the vertical direction means adjusting the angle in the vertical direction of the sample holder so that the sample surface and the direction in which the knife moves are parallel, as shown in FIG. 14 . In addition, adjusting the angle in the left-right direction means adjusting the angle in the left-right direction of the knife so that the edge of the knife and the surface of the sample become parallel, as shown in FIG. 14 . As shown in Fig. 14, the adjustment of the clearance angle means adjusting the minimum angle formed between the surface of the blade tip of the knife on the sample side and the direction in which the knife moves. The clearance angle is preferably 5 to 10°. When the clearance angle is within the above range, friction between the blade tip of the knife and the sample surface can be reduced, and the knife can be prevented from stabbing the sample surface after cutting out the thin film slice from the sample.

While checking the optical microscope attached to the ultra microtome device body, set the setting value of the microtome device so that the distance between the sample and the diamond knife is close, the blade speed is 0.3 mm / sec, and the thickness of the thin film is 60 nm ± 20 nm, After cutting out a thin film slice from the resin cast, the thin film slice for TEM measurement was floated on the surface of the ion-exchanged water. A copper mesh for TEM measurement (manufactured by Nissin EM Co., Ltd., trade name “Copper Mesh with Microgrid”) is pressed from the upper surface of the thin film slice for TEM measurement that has floated on the surface of the water, and the thin film slice for TEM measurement is attached to the copper mesh. It was adsorbed and used as a TEM sample. In addition, since thin film slices for TEM measurement obtained with a microtome do not exactly match the set value of the thickness cut out of the microtome, a set value at which a desired thickness is obtained is obtained in advance.

(Method of mapping by EDX detector)

"Thin film slices for TEM measurement" were fixed to a sample holder (manufactured by Nippon Electronics Co., Ltd., trade name "Beryllium Sample Biaxial Inclined Holder, EM-31640") for each copper mesh, and inserted into the TEM apparatus. After starting electron beam irradiation to the sample at an accelerating voltage of 200 kV, the electron beam irradiation system was switched to the STEM mode.

After inserting the scanning image observation device into the position at the time of STEM observation and starting the STEM observation software "JEOL Simple Image Viewer (Version 1.3.5)" (manufactured by Nippon Electronics Co., Ltd.), "Thin film for TEM measurement Slice” was observed, and among the cross-sections of the observed conductive particles, a location suitable for EDX measurement was found and photographed. The location suitable for measurement as used herein means a location where the cross section of the metal layer can be observed by being cut near the center of the conductive particle, where the cross section is inclined, and where the cross section is displaced from the vicinity of the center of the conductive particle. The location was excluded from the measurement target. In addition, at the time of photographing, the observation magnification was 250,000 times, and the number of pixels in the STEM observation image was set to 512 points vertically and 512 points horizontally. When observed under these conditions, an observation image with a viewing angle of 600 nm is obtained. However, care must be taken because the viewing angle may change even at the same magnification when the apparatus is changed.

During STEM/EDX analysis, when an electron beam is applied to the "thin film slice for TEM measurement" of the conductive particle, contraction or thermal expansion of the plastic core of the conductive particle and casting resin occurs, and the sample deforms or moves during measurement. In order to suppress sample deformation and sample movement during EDX measurement, an electron beam was irradiated to the measurement site for about 30 minutes to 1 hour in advance, and it was analyzed after confirming that the deformation and movement were accepted.

In order to perform STEM/EDX analysis, the EDX detector was moved to the measurement position, and software "Analysis Station" (manufactured by Nippon Electronics Co., Ltd.) for EDX measurement was started. In mapping by the EDX detector, since it is necessary to obtain sufficient resolution at the time of mapping, a focusing throttling valve device for concentrating the electron beam to a target location was used.

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

In order to calculate the length (D1) of the grains containing palladium, a mapping image of palladium was produced based on the obtained STEM/EDX analysis data. In this mapping image of palladium, as shown in FIG. 12, by binarizing the obtained mapping image into black and white, the boundary line between the part where palladium exists and the part where it does not exist is determined, and the boundary between the boundary line in the thickness direction of the metal layer is determined. The distance was set to D1. However, noise was included in the measurement data, and filter processing was performed to improve the S/N ratio. The filter processing is a function attached to the software "Analysis Station" for EDX measurement, and at each measurement point, data of a plurality of points adjacent to the measurement point can be integrated and displayed in addition to the data of each measurement point. Since the S/N of the mapping image is thereby improved, the length D1 of grains containing palladium can be calculated from the mapping image of palladium. In this embodiment, by using this filter process, in addition to the data of each measurement point, the data of 8 points (upper, lower, left, right, upper left, lower left, upper right, lower right) adjacent to the measurement point are integrated, After reducing the noise on the mapping, the length (D1) of the grain containing palladium was calculated.

From the obtained EDX mapping data, EDX spectra in the first part, the second part, the third part, the first nickel-containing layer, and the second nickel-containing layer were extracted as needed, and the element abundance ratio in each layer was calculated. However, when calculating the quantitative value, the mass% concentration of each element was calculated by taking the total ratio of copper, palladium, nickel, and phosphorus as 100%.

In addition, elements other than the above were excluded when calculating the quantitative values because the ratio is liable to fluctuate for the following reasons. The ratio of carbon increases or decreases due to the influence of the carbon support film used for the mesh for TEM measurement or contaminants adsorbed on the sample surface during electron beam irradiation. Oxygen may increase due to air oxidation between the preparation of the TEM sample and the measurement. In addition, copper is detected from the copper mesh used for TEM measurement.

(Content of palladium in grains containing palladium)

First, samples for evaluation were produced by a method using the following copper-clad laminate.

<How to use copper clad laminate>

A copper clad laminated board "MCL-E-679F" (manufactured by Hitachi Chemical Co., Ltd., trade name) was cut into a size of 1 cm x 1 cm to obtain a substrate. This board|substrate was immersed in degreasing liquid "Z-200" (product name made by World Metal Co., Ltd.) at 50 degreeC for 1 minute, and it washed with water for 1 minute. Then, 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. Subsequently, it was immersed at 25°C for 5 minutes in "SA-100" (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a plating activating treatment liquid, and washed with water for 1 minute. Then, electroless nickel plating containing 11.5% by mass of phosphorus was carried out on the copper foil by immersing the electroless nickel plating solution, Nacron NAC (trade name, manufactured by Okuno Seiyaku Kogyo Co., Ltd.) at 85°C for 4 minutes. Then, a film having a thickness of 0.7 μm was formed, washed with water for 1 minute, and then immersed in the electroless palladium plating solution having the composition and liquid amount of (Step c) at 60° C. for 10 minutes to form an electroless nickel plating film. An electroless palladium plating film with a thickness of about 0.1 μm was formed on the surface, which was then washed with water for 1 minute and dried to obtain a sample for evaluation.

Next, the obtained sample for evaluation was mixed with 90% by mass of a casting resin (epoxy resin 815 (product name, manufactured by Japan Epoxy Resin Co., Ltd.) and 10% by mass of triethylenetetramine (product name, manufactured by Wako Pure Chemical Industries, Ltd.) ), and the cross section of the electroless palladium plating film was cut out with an ultra microtome method so that the cross section could be observed, and observed at a magnification of 250,000 times using a TEM device. Subsequently, for the electroless palladium plating film, the palladium content was calculated by component analysis using an EDX detector, and this content was used as the palladium content in grains containing palladium. The content of palladium in the grains containing palladium thus obtained was 100%. In addition, when the grains containing palladium contain components other than palladium, their content was also calculated by component analysis by an EDX detector for the evaluation sample in the same way as for palladium.

(Evaluation of film thickness and components)

For the obtained conductive particle, a cross section was cut out by an ultra microtome method so as to pass near the center of the particle, and a transmission electron microscope (hereinafter referred to as TEM device, manufactured by Nippon Electronics Co., Ltd., trade name “JEM-2100F”) was used. The cross-sectional areas of the first portion, the second portion, the third portion, the first nickel-containing layer, and the second nickel-containing layer at a width of 300 nm were estimated from the image obtained by observing at a magnification of 250,000 times, and at a width of 300 nm The cross-sectional area was approximated to a rectangle with one side of 300 nm, and the length of one side was calculated as the film thickness of the first part, the second part, the third part, the first nickel-containing layer, and the second nickel-containing layer. Table 1 also shows average values of film thicknesses calculated for 10 conductive particles. In addition, at this time, when it is difficult to distinguish the first part, the second part, the third part, the first nickel-containing layer, and the second nickel-containing layer, an energy dispersive X-ray detector (hereinafter referred to as an EDX detector, Nippon Electronics Co., Ltd. By component analysis by manufacture, trade name "JED-2300"), the distinction between the first layer and the second layer was clarified, the cross-sectional area of each layer was estimated, and the film thickness was measured. The results are shown in Table 1.

(Evaluation of projections formed on the surface of conductive particles)

The obtained conductive particles were observed at a magnification of 30,000 using an SEM device, and the coverage due to projections on the surface of the conductive particles was calculated based on the SEM image. In addition, the number and ratio of protrusions in concentric circles having a diameter of 1/2 of the diameter of the conductive particles were observed with a SEM device at a magnification of 30,000, and calculated based on the SEM images. 10 shows the results of observing the surface of the conductive particles with an SEM device.

In addition, the height of the protrusion was determined based on an image obtained by cutting a cross section of the conductive particle through the vicinity of the center of the particle by an ultramicrotome method and observing it at a magnification of 250,000 times using a TEM device. The height of 10 protrusions was calculated|required, and the average value of them was made into the average height. FIG. 15 is a diagram for explaining a method for obtaining the height of a protrusion from the STEM image of FIG. 11 . As shown in Fig. 15, the height of the projection was measured as a distance from a straight line connecting the valleys on both sides of the projection to the apex of the projection in the vertical direction.

The coverage of the protrusions was observed at a magnification of 30,000 with an SEM device, and based on the SEM image, protrusion formation parts and flat areas were distinguished by image analysis within concentric circles having a diameter of 1/2 of the diameter of the conductive particles, By calculating the ratio of the protrusion formation part within the concentric circle, it was set as the coverage of protrusion.

The distribution of protrusion heights was obtained as a percentage (%) of the number of protrusions of a predetermined height from the measurement results of D4 shown in FIG. 5 for 10 conductive particles.

As for the outer diameter of the projection, the area of the outline of the trough of the projection is measured for the projection existing in a concentric circle having a diameter of 1/2 of the diameter of the conductive particle on the orthographic projection surface of the conductive particle, and the area is the area of the circle. The average value of the diameter calculated when considered as was calculated. Specifically, conductive particles are observed at a magnification of 30,000 with an SEM device, and based on the obtained SEM image, the outline of the projection is calculated by image analysis, the area of each projection is calculated, and the average value of the projection is calculated. external appearance was sought.

(Method of measuring the resistance value of conductive particles)

When conductive particles are compressed using a micro compression tester MCTW-200 (manufactured by Shimadzu Seisakusho Co., Ltd., trade name) under the condition of a load speed of 0.5 mN/sec, and compressed until the particle diameter becomes 70% of the original size (compression rate 30%), when compressed to 50% of the original particle size (compression rate 50%), when compressed until 40% of the original particle size (compression rate 60%), 30% of the original particle size (compression rate: 70%), compression to 20% of the original particle size (compression rate: 80%), and compression to 10% of the original particle size (compression rate: 90%) The electrical resistance value (Ω) of was measured. The same measurement was performed on 10 conductive particles, and the average value was obtained. The results are shown in Table 1.

[Production of Insulated Coated Conductive Particles]

A 30% by mass aqueous solution of polyethyleneimine having a molecular weight of 70000 (manufactured by Wako Pure Chemical Industries, Ltd.) was diluted to 0.3% by mass with ultrapure water. To 300 mL of this 0.3% by mass polyethyleneimine aqueous solution, 200 g of conductive particles obtained in the same manner as above were added, and stirred at room temperature for 15 minutes. Conductive particles were taken out by filtration using a φ3 μm membrane filter (manufactured by Melk Corporation), and the taken out conductive particles were placed in 200 g of ultrapure water and stirred at room temperature for 5 minutes. Further, conductive particles were taken out by filtration using a φ3 μm membrane filter (manufactured by Melk Corporation), and the conductive particles on the membrane filter were washed twice with 200 g of ultrapure water to remove non-adsorbed polyethyleneimine.

Then, the colloidal silica dispersion of phi 130 nm was diluted with ultrapure water to obtain a 0.1% by mass silica particle dispersion. Thereto, 200 g of conductive particles treated with the above polyethyleneimine were put and stirred at room temperature for 15 minutes. Conductive particles were taken out by filtration using a φ3 μm membrane filter (manufactured by Melk Corporation), and the taken out 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 Melk Corporation), and the conductive particles on the membrane filter were washed twice with 200 g of ultrapure water to remove the silica particles that were not adsorbed, and the silica particles Insulation-coated conductive particles adsorbed on the surface were obtained.

SC6000 (trade name manufactured by Hitachi Chemical Co., Ltd.), a silicone oligomer having a molecular weight of 3000, was attached to the surface of the obtained insulated-coated conductive particles to hydrophobize the surfaces of the insulated-coated conductive particles. The hydrophobized insulated-coated conductive particles were dried by heating at 80°C for 30 minutes and at 120°C for 1 hour in that order to obtain hydrophobic insulated-coated conductive particles. The average coverage of the conductive particles with the silica particles was measured by image analysis of the SEM image, and it was about 28%.

[Production of Anisotropic Conductive Adhesive Film and Connected Structure]

100 g of phenoxy resin (manufactured by Union Carbide, trade name "PKHC"), 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 Copolymer, molecular weight: 850,000) 75 g 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.

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

Next, a chip (1.7×1.7 mm, thickness: 0.5 μm) with gold bumps (area: 30 × 90 μm, space 10 μm, height: 15 μm, number of bumps: 362) was attached using the prepared anisotropic conductive adhesive film. And connection with the glass substrate (thickness: 0.7 mm) with an IZO circuit was performed according to the order of i)-iii) shown below, and the bonded structure was obtained.

i) An anisotropically 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 bump of the chip and the glass substrate with IZO circuit were aligned.

iii) Heating and pressurization were performed from above the chip under the conditions of 190°C, 40 gf/bump, and 10 seconds to make this connection.

[Evaluation of Connection Structure]

The conduction resistance test and the insulation resistance test of the obtained bonded structure were performed as follows.

(continuity resistance test)

Regarding the conduction resistance between the chip electrode (bump) and the glass electrode (IZO), the initial value of the conduction resistance and the moisture absorption heat resistance test (100, 300, 500, 1000, 2000 hours left at a temperature of 85 ° C and a humidity of 85%) The following values were measured for 20 samples, and their average value was calculated. Conduction resistance was evaluated according to the following criteria from the obtained average value. The results are shown in Table 1. Further, when the criteria of A or B below are satisfied after 500 hours of the moisture absorption heat resistance test, the conduction resistance can be said to be good.

A: The average value of conduction resistance is less than 2Ω

B: The average value of the conduction resistance is 2 Ω or more and less than 5 Ω

C: The average value of conduction resistance is 5 Ω or more and less than 10 Ω

(insulation resistance test)

Regarding the insulation resistance between the chip electrodes, the initial value of the insulation resistance and the value after the migration test (leaving for 100, 300, 500, and 1000 hours under the conditions of a temperature of 60 ° C, humidity of 90%, and 20 V applied) were measured for 20 samples, , among all 20 samples, the ratio of samples having an insulation resistance value of 10 ⁹ Ω or more was calculated. Insulation resistance was evaluated according to the following criteria from the obtained ratio. The results are shown in Table 1. In addition, when the criteria of A or B below are satisfied after 500 hours of the moisture absorption heat resistance test, the insulation resistance can be said to be good.

A: 100% of the ratio of insulation resistance value of 10 ⁹ Ω or more

B: The ratio of insulation resistance value 10 ⁹ Ω or more is 90% or more and less than 100%

C: The ratio of insulation resistance value 10 ⁹ Ω or more is 80% or more and less than 90%

D: The ratio of insulation resistance value 10 ⁹ Ω or more is 50% or more and less than 80%

<Example 2>

In Example 1 (Step b), the resin particles treated in the same way as in Example 1 (Step a) were added to 1 L of pure water heated to 40 ° C., and the same as in Example 1 (Step b), dropping method Replenishment solution A and replenishment solution B were added dropwise thereto to directly form a first layer (third part) containing copper on the surface of the resin particle. Other than that, in the same manner as in Example 1, conductive particles, insulated coated particles, an anisotropic conductive adhesive film, and a bonded structure were prepared, and the conductive particles and the bonded structure were evaluated. The results are shown in Table 1.

<Example 3>

(Steps a to b) of Example 1 are performed similarly, and 4 g of first layer formed particles are substituted palladium containing 10% by mass of SA-100 (trade name, manufactured by Hitachi Chemical Industry Co., Ltd.) as a substituted palladium plating solution It was added to 100 mL of the plating solution, stirred at 30 ° C. for 5 minutes, filtered with a φ 3 μm membrane filter (manufactured by Merck Millipore Co., Ltd.), and washed with water to deposit palladium of atomic level on the first layer. It was deposited by substitution on copper. In addition, at this time, since copper in the outermost layer was dissolved and palladium was deposited by substitution instead, there was no change in the weight of the particles. 4 g of particles obtained by substitution deposition of palladium were diluted with 1000 mL of water heated at 80 ° C. and dispersed, 1 mL of 1 g/L bismuth nitrate aqueous solution was added as a plating stabilizer, and electroless nickel for forming a first nickel-containing layer having the following composition 10 mL of plating liquid was dripped at the dripping rate of 5 mL/min. After completion of the dropwise addition, after 10 minutes had elapsed, the dispersion to which the plating solution was added was filtered, and the filtrate was washed with water and then dried in a vacuum dryer at 80°C. In this way, the layer of the 1st nickel containing layer containing the 10-nm-thick nickel-phosphorus alloy film shown in Table 1 was formed. In addition, the particle size obtained by forming the first nickel-containing layer was 4.25 g.

(Electroless nickel plating solution for forming the first nickel-containing layer)

Nickel sulfate・・・・・・・・・・・・・・400g/L

Sodium hypophosphite・・・・・・・・・・・・・150g/L

Sodium citrate・・・・・・・・・・・・120g/L

Aqueous bismuth nitrate solution (1 g/L)... 1 mL/L

Thereafter, in the same manner as in Example 1 (Step c) and beyond, conductive particles, insulated coated particles, an anisotropic conductive adhesive film, and a bonded structure were prepared, and the conductive particles and the bonded structure were evaluated. The results are shown in Table 1.

<Examples 4 to 7>

In Example 1 (Step b), the thickness of the third part containing copper was changed to the thickness shown in Table 1, and between (Step b) and (Step c) of Example 1, similarly to <Example 3>. , Fabrication of conductive particles, insulated coated particles, anisotropically conductive adhesive film, and connection structure in the same manner as in Example 1, except that a layer of the first nickel-containing layer containing a nickel-phosphorus alloy film having a film thickness of 10 nm was formed. , and conductive particles and bonded structures were evaluated. The results are shown in Table 1. In addition, formation of the 3rd part containing copper was performed using replenishment liquid A and replenishment liquid B of the same composition as Example 1 (process b), and changing only the amount of plating liquid. Specifically, in Example 4, 233 mL, in Example 5, 465 mL, in Example 6, 698 mL, and in Example 7, 1395 mL of replenishment liquid A and replenishment liquid B were used.

<Examples 8 to 13>

Between (step b) and (step c) of Example 1, as in <Example 3>, a layer of a first nickel-containing layer containing a nickel-phosphorus alloy film having a film thickness of 10 nm is formed, Except for changing the thickness of the second nickel-containing layer to the thickness shown in Table 2 in (step d), in the same manner as in Example 1, conductive particles, insulation coated particles, anisotropically conductive adhesive film, and production of bonded structures, and conduction Particles and bonded structures were evaluated. The results are shown in Table 2. In addition, formation of the 2nd nickel containing layer was performed using the electroless nickel plating solution of the same composition as Example 1 (process d), and changing only the amount of plating solution. Specifically, a plating solution of 12.5 mL in Example 8, 25 mL in Example 9, 37.5 mL in Example 10, 62.5 mL in Example 11, 75 mL in Example 12, and 100 mL in Example 13 was used in Example 8.

<Examples 14 to 15>

In Example 1 (Step b), the thickness of the third part containing copper was changed to the thickness shown in Table 3, and between (Step b) and (Step c) of Example 1, similarly to <Example 3>. , forming a layer of the first nickel-containing layer containing a nickel-phosphorus alloy film with a film thickness of 10 nm, and changing the second nickel-containing layer to the thickness shown in Table 3 in (step d) of Example 1 In the same manner as in Example 1, conductive particles, insulated coated particles, an anisotropic conductive adhesive film, and a bonded structure were prepared, and the conductive particles and the bonded structure were evaluated. The results are shown in Table 3. In addition, formation of the 3rd part containing copper was performed using replenishment liquid A and replenishment liquid B of the same composition as Example 1 (process b), and changing only the amount of plating liquid. Specifically, in Example 14, 465 mL, and in Example 15, 698 mL of replenishment solution A and replenishment solution B were used. In addition, formation of the 2nd nickel containing layer was performed using the electroless nickel plating solution of the same composition as Example 1 (process d), and changing only the amount of plating solution. Specifically, 25 mL in Example 14 and 37.5 mL of plating solution in Example 15 were used.

<Examples 16 to 18>

Conductive particles, insulated coated particles, anisotropic Production of the conductive adhesive film and the bonded structure, and evaluation of the conductive particles and the bonded structure were performed. The results are shown in Table 3. In addition, the formation of the first nickel-containing layer including the nickel-phosphorus alloy film was performed using a plating solution having the same composition as the electroless nickel plating solution for forming the first nickel-containing layer in Example 3, only changing the amount of the plating solution. . Specifically, in Example 16, 20 mL, in Example 17, 50 mL, and in Example 18, a plating solution of 80 mL was used.

<Comparative Example 1>

Crosslinked polystyrene particles with an average particle diameter of 3.0 μm (manufactured by Nippon Shokubai Co., Ltd., trade name “Sorio Star” were used as resin particles. 400 mL of an aqueous solution of Cleaner Conditioner 231 (manufactured by Rohm and Hass Denshi Yyo Co., Ltd., Concentration 40 mL/L), 30 g of resin particles were added thereto while stirring. Subsequently, the aqueous solution was heated at 60° C. and stirred for 30 minutes while applying ultrasonic waves to perform surface modification and dispersion treatment of the resin particles.

After filtering the aqueous solution and washing the obtained particles with water once, 30 g of particles were dispersed in water to obtain a slurry of 200 mL. To this slurry, 200 mL of an aqueous solution of stannous chloride (concentration: 1.5 g/L) was added, followed by stirring at room temperature for 5 minutes to perform a sensitization treatment of adsorbing stannous ions to the surface of the particles. Subsequently, the aqueous solution was filtered, and the obtained particles were washed with water once. Subsequently, 30 g of particles were dispersed in water to obtain a slurry of 400 mL, which was heated to 60°C. 2 mL of 10 g/L palladium chloride aqueous solution was added while stirring the slurry in combination with ultrasonic waves. By stirring for 5 minutes as it is, an activation treatment for trapping palladium ions on the surface of the particles was performed. Subsequently, the aqueous solution was filtered, and the obtained particles were washed with water once.

Subsequently, 3 liters of an electroless plating solution containing 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 particles were added. This was stirred for 5 minutes, and it was confirmed that hydrogen foaming stopped.

Thereafter, 600 mL of a 200 g/L aqueous solution of nickel sulfate and 600 mL of a mixed aqueous solution of 200 g/L sodium hypophosphite and 90 g/L sodium hydroxide were simultaneously and continuously added to the plating solution containing the particles using a metering pump. All addition rates were 3 mL/min. Subsequently, this solution was stirred for 5 minutes while maintaining 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 conductive particles having a nickel-phosphorus alloy coating. got it For the obtained conductive particle, a cross section was cut with an ultra microtome method so as to pass through the center of the particle, observed at a magnification of 250,000 using a TEM device, and based on the image of the obtained cross section, the film thickness was determined from the average value of the cross section area As a result of calculation, the average film thickness was 156 nm.

Insulated coated particles, an anisotropic conductive adhesive film, and a bonded structure were prepared, and the conductive particles and the bonded structure were evaluated in the same manner as in Example 1 except for using the conductive particles described above. The results are shown in Table 4.

<Comparative Example 2>

Crosslinked polystyrene particles with an average particle diameter of 3.0 μm (manufactured by Nippon Shokubai Co., Ltd., trade name “Sorio Star”) were used as resin particles. Concentration 40 mL/L), 7 g of resin particles were added thereto while stirring. Subsequently, the aqueous solution was heated at 60° C. and stirred for 30 minutes while applying ultrasonic waves to perform surface modification and dispersion treatment of the resin particles.

After filtering the aqueous solution and washing the obtained particles with water once, 7 g of the particles were dispersed in pure water to obtain a slurry of 200 mL. To this slurry, 200 mL of an aqueous solution of stannous chloride (concentration: 1.5 g/L) was added, followed by stirring at room temperature for 5 minutes to perform a sensitization treatment of adsorbing stannous ions to the surface of the particles. Subsequently, the aqueous solution was filtered, and the obtained particles were washed with water once. Subsequently, 7 g of the particles were dispersed in water to obtain a slurry of 400 mL, which was heated to 60°C. 2 mL of 10 g/L palladium chloride aqueous solution was added while stirring the slurry in combination with ultrasonic waves. By stirring for 5 minutes as it is, an activation treatment for trapping palladium ions on the surface of the particles was performed. Subsequently, the aqueous solution was filtered, and the obtained particles were washed with water once.

After stirring and dispersing 7 g of the obtained resin particles in addition to 300 mL of pure water for 3 minutes, 2.25 g of nickel particles (manufactured by Mitsui Kinzoku Co., Ltd., trade name "2007SUS", average particle diameter 50 nm) as a center material were added to the dispersion, and the center material was Adhering particles were obtained.

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

Subsequently, 1000 mL of a mixed solution of 450 g/L of nickel sulfate, 150 g/L of sodium hypophosphite, 116 g/L of sodium citrate, and 35 mL of a plating stabilizer [aqueous bismuth nitrate solution (concentration: 1 g/L)] was added at an addition rate of 27 mL/min. It was added via a metering pump. Thereafter, stirring was performed until the pH stabilized, and it was confirmed that hydrogen effervescence stopped.

Subsequently, the plating solution was filtered, and the filtrate was washed with water and then dried in a vacuum dryer at 80°C to obtain conductive particles having a nickel-phosphorus alloy coating. For the obtained conductive particle, a cross section was cut with an ultra microtome method so as to pass through the center of the particle, observed at a magnification of 250,000 times using a TEM device, and based on the image of the obtained cross section, the film thickness was calculated from the average value of the cross section area. As a result, the average film thickness was 151 nm.

Insulated coated particles, an anisotropic conductive adhesive film, and a bonded structure were prepared, and the conductive particles and the bonded structure were evaluated in the same manner as in Example 1 except for using the conductive particles described above. The results are shown in Table 4.

Comparative example 1 corresponds to patent document 1, and comparative example 2 corresponds to patent document 2.

From the results of Tables 1 to 3, it was found that the conductive particles produced in Examples 1 to 18 could maintain a resistance value of 5 Ω or less when compressed to 20% of the original particle size (compression ratio 80%). It became clear. Moreover, it became clear that excellent conduction reliability and insulation reliability were obtained even after the moisture absorption heat resistance test even when it was set as a bonded structure. On the other hand, it was found that the electrical resistance value of the conductive particles produced in Comparative Examples 1 and 2 increased by compression, exceeding 10 Ω when the compression rate was 80%. Moreover, when it was set as a bonded structure, the characteristics of conduction reliability and insulation reliability fell after the moisture absorption heat resistance test.

DESCRIPTION OF SYMBOLS 1: Insulating particle 2: Conductive particle
10: insulating coated conductive particles 20: insulating adhesive
20a: insulating adhesive cured material 30: first circuit member
31: circuit board (first circuit board) 31a: main surface of the first circuit board
32: circuit electrode (first circuit electrode) 40: second circuit member
41: circuit board (second circuit board) 41a: main surface of the second circuit board
42: circuit electrode (second circuit electrode)
50: Anisotropic conductive adhesive on film
50a: connection part, 100: connection structure
200: first layer 201: grains containing palladium
202 second layer 203 resin particles
204: metal layer 205: protrusion
206: first nickel-containing layer 207: second nickel-containing layer
208: Ni-Cu layer 208a: first part
208b: second part 208c: third part

Claims (23)

A resin particle and a metal layer provided on the surface of the resin particle,
The metal layer has, in order close to the resin particle, a first layer containing copper or nickel and copper, and a second layer containing nickel, and the length of the metal layer in the thickness direction is 4 nm or more and 35 nm or less. contains,
The grains contain palladium,
The second layer has a second nickel-containing layer having a nickel content of 93% by mass or more, and the second nickel-containing layer further contains phosphorus;
The second layer is the outermost layer,
Protrusions are formed on the outer surface of the metal layer,
Wherein the average thickness of the metal layer is denoted by d, the shortest distance from the grain to the interface between the metal layer and the resin particle is 0.1 x d or more. The conductive particle according to claim 1, wherein the metal layer contains particles containing palladium between the first layer and the second layer or in the second layer. The conductive particle according to claim 1, wherein the metal layer contains grains containing the palladium having a shortest distance to an interface between the metal layer and the resin particle of 10 nm or more. The conductive particle according to claim 1, wherein the metal layer contains grains containing the palladium dotted in a direction orthogonal to a thickness direction of the metal layer. The conductive particle according to claim 1, wherein the palladium content in the palladium-containing grains is 94% by mass or more. The conductive particle according to claim 1, wherein the grains containing palladium further contain phosphorus. The method of claim 1, wherein the first layer has a Ni-Cu layer containing nickel and copper, and the Ni-Cu layer has a portion where the elemental ratio of copper to nickel increases as the distance from the surface of the resin particle increases. having, a conductive particle. The Ni-Cu layer according to claim 7, wherein the Ni-Cu layer includes, in order closer to the resin particles, a first portion having a nickel content of 97% by mass or more, a second portion constituting the portion, and a third portion containing copper. With, conductive particles. The conductive particle according to claim 8, wherein the total of the nickel content and the copper content in the second portion is 97% by mass or more. The conductive particle according to claim 8, wherein the copper content in the third portion is 97% by mass or more. The conductive particle according to claim 1, wherein the second layer includes a first nickel-containing layer having a nickel content of 83 to 98% by mass and a second nickel-containing layer, in order closer to the first layer. The conductive particle according to claim 11, wherein the nickel content in the first nickel-containing layer is 85 to 93% by mass. The conductive particle according to claim 11, wherein the nickel content in the second nickel-containing layer is 96% by mass or more. The conductive particle according to claim 11, wherein the first nickel-containing layer further contains phosphorus. The conductive particle according to claim 1, wherein the metal layer further has a third layer containing palladium and a fourth layer containing gold on the side opposite to the first layer of the second layer. A step of forming a first layer containing copper or nickel and copper on the surface of the resin particle by electroless plating;
A step of forming grains containing palladium on the first layer by reducing precipitation of an electroless palladium plating solution containing palladium ions and a reducing agent, and on the first layer and the grains containing palladium, A method for producing conductive particles comprising a step of forming a second layer containing nickel by electroless nickel plating. A step of forming a first layer containing copper or nickel and copper on the surface of the resin particle by electroless plating;
forming a first nickel-containing layer containing nickel on the first layer by electroless nickel plating;
forming grains containing palladium on the first nickel-containing layer by reduction precipitation of an electroless palladium plating solution containing palladium ions and a reducing agent;
The method for producing conductive particles comprising a step of forming a second nickel-containing layer containing nickel by electroless nickel plating on the first nickel-containing layer and on the grains containing palladium. An anisotropic conductive adhesive comprising the conductive particles according to claim 1 and an adhesive. A first circuit member having a first circuit electrode and a second circuit member having a second circuit electrode are arranged so that the first circuit electrode and the second circuit electrode face each other, and the first circuit member and the second circuit member are disposed. A connection structure obtained by interposing the anisotropic conductive adhesive according to claim 18 between circuit members, heating and pressurizing them to electrically connect the first circuit electrode and the second circuit electrode. a first circuit member having a first circuit electrode;
a second circuit member having a second circuit electrode;
a connection portion comprising the conductive particle according to claim 1 and connecting the first circuit member and the second circuit member to each other;
The first circuit member and the second circuit member are disposed such that the first circuit electrode and the second circuit electrode face each other;
In the connection portion, the first circuit electrode and the second circuit electrode are electrically connected via the deformed conductive particles. delete delete delete

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