WO2025225643A1 - Resin particles, metal-coated particles, and resin material - Google Patents

Abstract

Provided are resin particles capable of enhancing gap controllability of a connection structure when exposed to a high temperature environment.　The resin particles according to present invention contain a polymer of polymerizable components. The polymerizable components include divinylbenzene and a (meth)acrylate compound having four or more (meth)acryloyl groups. The resin particles have a compression elastic modulus of 1000 N mm² or more when compressed by 20% at 200°C.

Description

Resin particles, metal-coated particles, and resin materials

The present invention relates to resin particles containing a polymer of a polymerizable component. The present invention also relates to metal-coated particles and resin materials using the resin particles.

Conductive materials such as conductive pastes and conductive films are widely known. In recent years, development has been underway to use these conductive materials in the mounting of semiconductor chips and other devices. From the perspective of increasing the amount of current and reliability in thermal cycles, conductive materials sometimes contain conductive particles such as solder particles dispersed in a binder resin.

The above-mentioned conductive materials are used to obtain a variety of connection structures. Examples of connections that use the above-mentioned conductive materials include connections between flexible printed circuit boards and glass substrates (FOG (Film on Glass)), connections between semiconductor chips and flexible printed circuit boards (COF (Chip on Film)), connections between semiconductor chips and glass substrates (COG (Chip on Glass)), and connections between flexible printed circuit boards and glass epoxy substrates (FOB (Film on Board)).

In such connection structures, spacers are used as gap control materials to maintain a uniform and constant distance (gap) between the two substrates (components to be connected). It is preferable that the spacers have properties that do not damage the substrates, and that the spacers are not destroyed during mounting. Resin particles may be used as the spacers, or metal-coated particles that comprise resin particles and a metal coating layer that covers the resin particles.

As an example of the resin particles, Patent Document 1 listed below discloses resin particles having a 5% weight loss temperature of 350°C or higher, a 10% K value at 25°C of 100 N/mm2 ^{or higher} and 2500 N/ ^mm2 or lower, and a 30% K value at 25°C of 100 N/mm2 ^{or higher} and 1500 N/mm2 ^or lower.

WO2021/193911A1

When conventional resin particles are used as spacers, there is an issue that when the resin particles are exposed to a high-temperature environment (e.g., 200°C), the compressive modulus of the resin particles cannot be sufficiently increased, and the gap controllability of the resin particles cannot be improved. Furthermore, in connection structures such as electronic components, the connection portion connecting two connection target components is repeatedly heated and cooled (exposed to thermal cycling conditions). With conventional resin particles, the thermal cycling causes the resin in the resin particles to thermally decompose, resulting in the generation of outgassing. When a large amount of outgassing occurs, voids can form in the connection portion of the connection structure, or cracks or peeling can occur between the resin particles and the metal coating layer in metal-coated particles, reducing the electrical conductivity reliability of the connection structure. In other words, it is difficult for conventional resin particles to effectively control the gap between substrates when exposed to a high-temperature environment and to improve the electrical conductivity reliability of the connection structure after thermal cycling.

An object of the present invention is to provide resin particles that can improve the gap controllability of connection structures when exposed to high-temperature environments, and the use of such resin particles in solder paste. Another object of the present invention is to provide metal-coated particles and resin materials that use the resin particles.

This specification discloses the following resin particles, use of resin particles in solder paste, metal-coated particles, and resin materials.

Item 1. Resin particles containing a polymer of a polymerizable component, wherein the polymerizable component contains divinylbenzene and a (meth)acrylate compound having four or more (meth)acryloyl groups, and the resin particles have a compressive modulus of 1000 N/ ^mm2 or more when compressed 20% at 200°C.

Item 2. Resin particles according to Item 1, wherein the total content of the divinylbenzene and the (meth)acrylate compound having four or more (meth)acryloyl groups is 80% by weight or more, based on 100% by weight of the polymerizable component.

Item 3. Resin particles according to Item 1 or 2, wherein the weight ratio of the content of the divinylbenzene in the polymerizable component to the content of the (meth)acrylate compound having four or more (meth)acryloyl groups in the polymerizable component is 0.40 or more and 1.70 or less.

Item 4. Resin particles according to any one of items 1 to 3, wherein the amount of outgassing when the resin particles are heated at 250°C for 10 minutes is 1000 ppm or less.

Item 5. Resin particles according to any one of items 1 to 4, wherein the particle diameter of the resin particles is 1 μm or more and 100 μm or less.

Item 6. Resin particles according to any one of Items 1 to 5, wherein the resin particles are used to obtain metal-coated particles having a metal coating layer formed on the surface thereof, or the resin particles have a particle diameter of 5 μm or more and 100 μm or less.

Item 7. Resin particles according to Item 6, wherein the resin particles are used to obtain metal-coated particles having a metal coating layer formed on the surface thereof, or the resin particles have a particle diameter of 20 μm or more and 100 μm or less.

Item 8. The resin particles described in any one of Items 1 to 5 are used to obtain metal-coated particles having a metal coating layer formed on the surface of the resin particles.

Item 9. Resin particles according to Item 5, wherein the particle diameter of the resin particles is 5 μm or more and 100 μm or less.

Item 10. Resin particles according to Item 9, wherein the particle diameter of the resin particles is 20 μm or more and 100 μm or less.

Item 11. Metal-coated particles comprising the resin particles described in any one of Items 1 to 10 and a metal coating layer disposed on the surface of the resin particles.

Item 12. The metal-coated particles described in Item 11, wherein the thickness of the metal coating layer is 0.2 μm or more.

Item 13. A resin material comprising the resin particles described in any one of Items 1 to 10 and a binder resin, or a resin material comprising the resin particles, metal-coated particles having a metal coating layer disposed on the surface of the resin particles, and a binder resin, wherein the resin particles or the metal-coated particles are dispersed in the binder resin.

Item 14. The resin material according to Item 13, wherein the resin material is a solder paste containing solder particles.

Item 15. Use of the resin particles described in any one of items 1 to 10, or the resin particles and metal-coated particles disposed on the surfaces of the resin particles, in a solder paste containing solder particles and a binder resin.

The resin particles according to the present invention are resin particles containing a polymer of a polymerizable component. In the resin particles according to the present invention, the polymerizable component contains divinylbenzene and a (meth)acrylate compound having four or more (meth)acryloyl groups. In the resin particles according to the present invention, the compressive modulus of the resin particles when compressed 20% at 200°C is 1000 N/mm2 ^or more. Because the resin particles according to the present invention have the above configuration, the gap controllability of the connection structure when exposed to a high-temperature environment can be improved.

FIG. 1 is a cross-sectional view schematically showing a resin particle according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a metal-coated particle using a resin particle according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view showing an example of a connection structure obtained using the resin particles according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view showing an example of a connection structure obtained using metal-coated particles using resin particles according to the first embodiment of the present invention.

The details of the present invention are explained below.

(Resin particles)
The resin particles according to the present invention are resin particles containing a polymer of a polymerizable component. In the resin particles according to the present invention, the polymerizable component contains divinylbenzene and a (meth)acrylate compound having four or more (meth)acryloyl groups. In the resin particles according to the present invention, the compressive modulus of the resin particles when compressed 20% at 200°C is 1000 N/mm2 ^or more.

When conventional resin particles are used as spacers, the compressive modulus of the resin particles cannot be sufficiently increased when exposed to a high-temperature environment (e.g., 200°C), which poses the problem of not being able to improve the gap controllability of the resin particles.

The resin particles according to the present invention have the above-mentioned configuration, which allows for improved gap control of the connection structure when exposed to a high-temperature environment. In the connection structure, the resin particles allow for highly accurate control of the gap on or between the connection target components.

Furthermore, in connection structures for electronic components and the like, the connection portion connecting two components to be connected is repeatedly heated and cooled (exposed to thermal cycling conditions). With conventional resin particles, the thermal cycling causes the resin in the resin particles to thermally decompose, resulting in the generation of outgassing. When a large amount of outgassing occurs, voids can form in the connection portion of the connection structure, or cracks or peeling can occur between the resin particles and the metal coating layer in metal-coated particles, reducing the electrical conductivity reliability of the connection structure. In other words, with conventional resin particles, it is difficult to effectively control the gap between substrates when exposed to a high-temperature environment and to improve the electrical conductivity reliability of the connection structure after thermal cycling.

The resin particles according to the present invention have the above-mentioned configuration, and therefore can be used in applications where electrical conductivity reliability is required. The resin particles according to the present invention have the above-mentioned configuration, and therefore can improve the electrical conductivity reliability of connection structures after thermal cycling. However, the resin particles according to the present invention can also be used in applications where electrical conductivity reliability is not required.

The present invention will now be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing a resin particle according to a first embodiment of the present invention.

The resin particles 1 contain a polymer of a polymerizable component. In the resin particles 1, the polymerizable component contains divinylbenzene and a (meth)acrylate compound having four or more (meth)acryloyl groups. The resin particles 1 have a compressive modulus of 1000 N/ ^mm2 or more when compressed 20% at 200°C.

The compressive modulus of elasticity when the resin particles are compressed 20% at 200 ° C (20% K value of the resin particles at 200 ° C) is 1000 N / mm ² or more. The 20% K value of the resin particles at 200 ° C is preferably 1200 N / mm ² or more, more preferably 1300 N / mm ² or more, even more preferably 1500 N / mm ² or more, particularly preferably 1750 N / mm ² or more, and most preferably 2000 N / mm ² or more, and preferably 20000 N / mm ² or less, more preferably 10000 N / mm ² or less, and even more preferably 5000 N / mm ² or less. When the 20% K value of the resin particles at 200 ° C is the above lower limit or more, the gap controllability of the connection structure when exposed to a high temperature environment can be further improved. When the 20% K value of the resin particles at 200 ° C is the above upper limit or less, the breakage of the resin particles when exposed to a high temperature environment can be further prevented.

The compressive modulus of the resin particles when compressed 20% at 25 ° C (20% K value of the resin particles at 25 ° C) is preferably 1000 N/mm ² or more, more preferably 1500 N/mm ² or more, even more preferably 2000 N/mm ² or more, and preferably 20,000 N/mm ² or less, more preferably 10,000 N/mm ² or less, and even more preferably 6,000 N/mm ² or less. When the 20% K value of the resin particles at 25 ° C is the above lower limit or more, the gap controllability of the connection structure when exposed to a high temperature environment can be further improved. When the 20% K value of the resin particles at 25 ° C is the above upper limit or less, the resin particles can better follow the connection target member (substrate, etc.), and the gap controllability can be further improved.

The ratio of the compressive modulus when the resin particles are compressed 20% at 25°C to the compressive modulus when the resin particles are compressed 20% at 200°C is defined as (20% K value of resin particles at 25°C/20% K value of resin particles at 200°C). This ratio (20% K value of resin particles at 25°C/20% K value of resin particles at 200°C) is preferably 0.7 or more, more preferably 0.9 or more, even more preferably 1.0 or more, and is preferably 3.0 or less, more preferably 2.5 or less, even more preferably 2.0 or less, and particularly preferably 1.5 or less. When the ratio (20% K value of resin particles at 25°C/20% K value of resin particles at 200°C) is equal to or greater than the above lower limit and equal to or less than the above upper limit, the gap controllability of the connection structure when exposed to a high-temperature environment can be further improved.

The 20% K value of the above resin particles at 25°C and 200°C can be measured as follows.

Using a micro-compression testing machine, resin particles are compressed with the smooth end face of a cylindrical indenter (diameter 50 μm, made of diamond) at 25°C or 200°C under conditions where a maximum test load of 90 mN is applied for 30 seconds. The load value (N) and compression displacement (mm) at this time are measured. From the obtained measured values, the compressive modulus can be calculated using the following formula. Examples of micro-compression testing machines that can be used include the Fischerscope H-100 manufactured by Fischer and the ENT-5 manufactured by Elionix.

20% K value (N/mm ² ) = (3/2 ^1/2 )·F·S ^{- 3/2} ·R ^{- 1/2}
F: Load value (N) when resin particles are compressed and deformed by 20%
S: Compression displacement (mm) when resin particles are compressed and deformed by 20%
R: Radius of resin particle (mm)

Methods for adjusting the 20% K values of the resin particles at 25°C and 200°C, and the ratio (20% K value of resin particles at 25°C/20% K value of resin particles at 200°C) within preferred ranges include using a preferred polymerizable component as described below, adjusting the molecular weight of the polymerizable component, using a preferred crosslinking agent as described below, adjusting the polymerization temperature and polymerization time, applying pressure during polymerization, adjusting the porosity (specific surface area) of the resin particles, and washing away unreacted polymerizable components (monomers).

From the perspective of further improving the effects of the present invention, the compression recovery rate of the resin particles at 25°C is preferably 20% or more, more preferably 25% or more, even more preferably 30% or more, and is preferably 95% or less, more preferably 90% or less, even more preferably 85% or less. The compression recovery rate of the resin particles at 25°C may be 70% or less, 60% or less, or 55% or less.

The compression recovery rate can be measured as follows.

Resin particles are scattered on a sample stage. Using a micro-compression testing machine, a load (reversed load value) is applied to each scattered resin particle at 25°C with the end face of a smooth cylindrical indenter (100 μm diameter, made of diamond) in the direction of the center of the resin particle until the resin particle is compressed and deformed by 40%. The load is then released to the origin load value (0.40 mN). The load-compression displacement during this period is measured, and the compression recovery rate can be calculated using the formula below. The loading rate is 0.33 mN/sec. Examples of micro-compression testing machines that can be used include the Fischerscope H-100 manufactured by Fischer and the ENT-5 manufactured by Elionix.

Compression recovery rate (%) = (L2/L1) x 100
L1: Compression displacement from the load value for origin when applying a load to the reverse load value. L2: Unloading displacement from the reverse load value when releasing the load to the load value for origin.

Other details about the resin particles are explained below. In the following explanation, "(meth)acrylic" means either or both of "acrylic" and "methacrylic," and "(meth)acrylate" means either or both of "acrylate" and "methacrylate."

The above-mentioned resin particles are resin particles formed from resin.

Various organic materials are suitable for use as the resin material for the resin particles. Examples of resin materials for the resin particles include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl (meth)acrylate and polyisobornyl (meth)acrylate; polyalkylene terephthalate, polycarbonate, polyamide, phenol-formaldehyde resin, melamine-formaldehyde resin, benzoguanamine-formaldehyde resin, urea-formaldehyde resin, phenolic resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyamide-imide, polyether ether ketone, polyether sulfone, and polymers obtained by polymerizing one or more of various polymerizable monomers having ethylenically unsaturated groups. Since the hardness of the resin particles can be easily controlled within a suitable range, the resin used to form the resin particles is preferably a polymer obtained by polymerizing one or more polymerizable monomers having multiple ethylenically unsaturated groups.

The resin particles contain a polymer of a polymerizable component. The polymerizable component preferably contains a polymerizable monomer having the ethylenically unsaturated group. Examples of the polymerizable monomer having the ethylenically unsaturated group include non-crosslinkable monomers and crosslinkable monomers.

The above-mentioned non-crosslinkable monomers include styrene-based monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate. Examples of suitable monomers include alkyl (meth)acrylate compounds such as methyl (meth)acrylate; oxygen-containing (meth)acrylate compounds such as 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate; nitrile-containing monomers such as (meth)acrylonitrile; and halogen-containing monomers such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene.

The above-mentioned crosslinkable monomers include tetramethylolmethane tetra(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propane tri ... Examples include polyfunctional (meth)acrylate compounds such as propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate; and silane-containing monomers such as triallyl (iso)cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane.

The polymerizable component includes divinylbenzene and a (meth)acrylate compound having four or more (meth)acryloyl groups. The polymer of the polymerizable component may include a copolymer of divinylbenzene and a (meth)acrylate compound having four or more (meth)acryloyl groups, or may include a homopolymer of divinylbenzene and a homopolymer of a (meth)acrylate compound having four or more (meth)acryloyl groups. From the perspective of more effectively achieving the effects of the present invention, it is preferable that the polymer of the polymerizable component include a copolymer of divinylbenzene and a (meth)acrylate compound having four or more (meth)acryloyl groups.

The (meth)acrylate compound having four or more (meth)acryloyl groups may have four, five or more, or six or more (meth)acryloyl groups. The (meth)acrylate compound having four or more (meth)acryloyl groups may have 20 or fewer, 10 or fewer, 8 or fewer, or 6 or fewer (meth)acryloyl groups. The range of the number of (meth)acryloyl groups in the (meth)acrylate compound having four or more (meth)acryloyl groups can be set by appropriately selecting the above lower limit and upper limit. The above (meth)acrylate compound having four or more (meth)acryloyl groups may be used alone, or two or more types may be used in combination.

From the viewpoint of more effectively achieving the effects of the present invention, it is particularly preferable that the (meth)acrylate compound having four or more (meth)acryloyl groups has four to six (meth)acryloyl groups. From the viewpoint of more effectively achieving the effects of the present invention, it is preferable that the (meth)acrylate compound having four or more (meth)acryloyl groups is a tetrafunctional (meth)acrylate compound, a pentafunctional (meth)acrylate compound, or a hexafunctional (meth)acrylate compound. The (meth)acrylate compound having four or more (meth)acryloyl groups may include a tetrafunctional (meth)acrylate compound, a pentafunctional (meth)acrylate compound, or a hexafunctional (meth)acrylate compound.

Examples of the (meth)acrylate compounds having four (meth)acryloyl groups (tetrafunctional (meth)acrylate compounds) include pentaerythritol tetra(meth)acrylate, pentaerythritol alkoxytetra(meth)acrylate, alkoxylated pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and tetramethylolmethane tetra(meth)acrylate.

Examples of the (meth)acrylate compound having five (meth)acryloyl groups include dipentaerythritol hydroxypenta(meth)acrylate and alkoxylated dipentaerythritol hydroxypenta(meth)acrylate.

Examples of the (meth)acrylate compound having six (meth)acryloyl groups include dipentaerythritol hexa(meth)acrylate (dipentaerythritol hexaacrylate, etc.) and alkoxylated dipentaerythritol hexa(meth)acrylate (alkoxylated dipentaerythritol hexaacrylate, etc.).

From the viewpoint of more effectively achieving the effects of the present invention, the (meth)acrylate compound having four or more (meth)acryloyl groups preferably includes a (meth)acrylate compound having four (meth)acryloyl groups, and more preferably includes pentaerythritol tetra(meth)acrylate. From the viewpoint of more effectively achieving the effects of the present invention, the polymerizable component preferably includes divinylbenzene and a (meth)acrylate compound having four (meth)acryloyl groups, and more preferably includes divinylbenzene and pentaerythritol tetra(meth)acrylate. From the viewpoint of more effectively achieving the effects of the present invention, the polymer (resin particles) of the polymerizable component preferably includes a copolymer of divinylbenzene and a (meth)acrylate compound having four (meth)acryloyl groups, and more preferably includes a copolymer of divinylbenzene and pentaerythritol tetra(meth)acrylate.

The above polymerizable component may or may not contain polymerizable components other than divinylbenzene and a (meth)acrylate compound having four or more (meth)acryloyl groups (hereinafter sometimes referred to as "other polymerizable components").

The other polymerizable components include the above-mentioned polymerizable monomers having an ethylenically unsaturated group. Only one type of the other polymerizable components may be used, or two or more types may be used in combination.

When using the above-mentioned crosslinkable monomers to obtain resin particles, a crosslinking agent can be used. Examples of the crosslinking agent include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate. The above-mentioned crosslinking agents may be used alone or in combination of two or more.

From the viewpoint of more effectively achieving the effects of the present invention, it is preferable that the polymerizable component contain a crosslinking agent. From the viewpoint of more effectively achieving the effects of the present invention, it is preferable that the polymerizable component (the crosslinking agent) contain (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, or 1,4-butanediol di(meth)acrylate. From the viewpoint of more effectively achieving the effects of the present invention, it is preferable that the polymerizable component (the crosslinking agent) be (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, or 1,4-butanediol di(meth)acrylate.

The resin particles can be obtained by polymerizing the polymerizable monomer having the ethylenically unsaturated group using a known method. Examples of such methods include suspension polymerization in the presence of a radical polymerization initiator, and polymerization using non-crosslinked seed particles to swell the monomer together with a radical polymerization initiator.

The viscosity of the polymerizable component mixture (before polymerization) is preferably 50 mPa·s or more, more preferably 100 mPa·s or more, even more preferably 500 mPa·s or more, particularly preferably 1000 mPa·s or more, and most preferably 1200 mPa·s or more, and is preferably 7000 mPa·s or less, more preferably 5000 mPa·s or less, and even more preferably 4000 mPa·s or less. When the viscosity of the polymerizable component mixture (before polymerization) is above the above lower limit, the particle size of the resin particles can be easily controlled. When the viscosity of the polymerizable component mixture (before polymerization) is below the above upper limit, the molecular weight of the resulting polymer of the polymerizable component can be increased, and the 20% K value of the resin particles at 25°C and 200°C can be easily adjusted within a preferred range, further improving the gap controllability of the connection structure when exposed to a high-temperature environment. The polymerizable component mixture (before polymerization) contains the polymerizable compound used in the resin particles in the weight ratio used in the resin particles.

The viscosity of the mixture of polymerizable components (before polymerization) is measured, for example, using an E-type viscometer at 25°C and 5 rpm. Examples of E-type viscometers include the "VISCOMETER TV-22" manufactured by Toki Sangyo Co., Ltd.

The particle diameter of the resin particles is preferably 0.1 μm or more, more preferably 1 μm or more, even more preferably 1.5 μm or more, even more preferably 2 μm or more, even more preferably 5 μm or more, particularly preferably 10 μm or more, and most preferably 20 μm or more, and is preferably 300 μm or less, more preferably 100 μm or less, even more preferably 70 μm or less, particularly preferably 50 μm or less, and most preferably 30 μm or less. If the particle diameter of the resin particles is above the above lower limit, they are less likely to agglomerate when a metal coating layer is formed on the surface of the resin particles by electroless plating, making it difficult for agglomerated metal-coated particles to form. If the particle diameter of the resin particles is below the above upper limit, the gap controllability of the connection structure when exposed to a high-temperature environment can be further improved.

In particular, when a resin material containing resin particles is cured, the occurrence of cracks in the cured product can be suppressed, and when a connection structure containing the resin material is exposed to a high-temperature environment, the gap controllability of the connection structure can be significantly improved. Therefore, it is preferable that the particle diameter of the resin particles be 5 μm or more. This effect is even more effectively achieved, so the particle diameter of the resin particles is more preferably 10 μm or more, and even more preferably 20 μm or more. Furthermore, when the resin material is a solder paste, this effect is even more effectively achieved. The particle diameter of the resin particles is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 100 μm or less, and even more preferably 20 μm or more and 100 μm or less. Furthermore, from the perspective of significantly improving the conductivity reliability of the connection structure after thermal cycling, it is preferable that the particle diameter of the resin particles be 10 μm or more.

The inventors have discovered that in order to achieve the effects of the present invention more effectively, it is important to 1) use a specific polymerizable component, 2) control the compressive modulus of the resin particles within a specific range, and 3) control the particle size of the resin particles within a specific range, that is, to combine these three requirements.

The particle size of the resin particles mentioned above refers to the diameter if the resin particles are spherical, and if the resin particles are other than spherical, refers to the diameter when assumed to be a perfect sphere with a volume equivalent to that of the resin particles.

The particle diameter of the resin particles is preferably an average particle diameter, and more preferably a number-average particle diameter. Furthermore, when the lower and upper limits of the number-average particle diameter of the resin particles satisfy the preferred lower and upper limits of the particle diameter of the resin particles, the effect is even more pronounced. The particle diameter of the resin particles can be determined, for example, by observing 50 random resin particles with an electron microscope or optical microscope and calculating the average particle diameter of each resin particle, or by performing laser diffraction particle size distribution measurement. When observed with an electron microscope or optical microscope, the particle diameter of each resin particle is determined as the particle diameter in equivalent circle diameter. When observed with an electron microscope or optical microscope, the average particle diameter in equivalent circle diameter of 50 random resin particles is approximately equal to the average particle diameter in equivalent sphere diameter. When observed with a laser diffraction particle size distribution measurement, the particle diameter of each resin particle is determined as the particle diameter in equivalent sphere diameter. The particle diameter of the resin particles is preferably calculated using laser diffraction particle size distribution measurement.

From the perspective of controlling the gap on or between connection target components with even greater precision, it is preferable that the resin particles do not contain resin particles having a particle diameter of 1.5 times or more the average particle diameter, or contain 1000 ppm or less of resin particles having a particle diameter of 1.5 times or more the average particle diameter. From the perspective of controlling the gap on or between connection target components with even greater precision, the content of resin particles having a particle diameter of 1.5 times or more the average particle diameter is preferably 1000 ppm or less, more preferably 100 ppm or less, even more preferably 10 ppm or less, and particularly preferably 0.1 ppm or less. This range includes 0 ppm. From the perspective of controlling the gap on or between connection target components with even greater precision, it is most preferable that the content of resin particles having a particle diameter of 1.5 times or more the average particle diameter is 0 ppm (not contained).

The content (ppm) of resin particles having a particle size 1.5 times or more the average particle size can be measured as follows: Resin particles are filtered through a filter with a pore size 1.5 times the average particle size, the resin particles remaining on the filter are observed under an optical microscope, and the resin particles having a particle size 1.5 times or more the average particle size are counted. The number of counted resin particles is divided by the total number of resin particles filtered to calculate the content (ppm) of resin particles having a particle size 1.5 times or more the average particle size.

From the perspective of controlling the gap on or between connection target components with even greater precision, the CV value (coefficient of variation) of the particle diameter of the resin particles is preferably 10% or less, and more preferably 8.0% or less. There is no particular limitation on the lower limit of the CV value of the particle diameter of the resin particles. The CV value of the particle diameter of the resin particles may be 0% or more, or 1.0% or more. The range of the CV value of the particle diameter of the resin particles can be set by appropriately selecting the lower limit and upper limit.

The CV value (coefficient of variation) of the particle diameter of the above resin particles can be measured as follows.

CV value (%) of particle diameter of resin particles = (ρ/Dn) × 100
ρ: Standard deviation of particle diameter of resin particles Dn: Average particle diameter of resin particles

From the perspective of controlling the gap on or between connection target components with even greater precision, the aspect ratio of the resin particles is preferably 1.5 or less, more preferably 1.3 or less. There is no particular lower limit to the aspect ratio of the resin particles. The aspect ratio of the resin particles may be 1.0 or more, or may be 1.1 or more. The aspect ratio represents the major axis/minor axis ratio. The aspect ratio is preferably determined by observing 10 random resin particles with an electron microscope or optical microscope, defining the maximum and minimum diameters as the major axis and minor axis, respectively, and calculating the average major axis/minor axis ratio of each spherical resin particle. The range of the aspect ratio of the resin particles can be set by appropriately selecting the lower limit and upper limit.

The amount of outgassing when the resin particles are heated at 250°C for 10 minutes is preferably 2000 ppm or less, more preferably 1000 ppm or less, even more preferably 800 ppm or less, particularly preferably 500 ppm or less, and most preferably 300 ppm or less. This range includes 0 ppm. Most preferably, the amount of outgassing when the resin particles are heated at 250°C for 10 minutes is 0 ppm (no outgassing). If the amount of outgassing when the resin particles are heated at 250°C for 10 minutes is below the above upper limit, it is possible to prevent voids from forming at the connection portion of the connection structure due to thermal cycling, and cracks or peeling from occurring between the resin particles and the metal coating layer of metal-coated particles, thereby improving the conductivity reliability of the connection structure after thermal cycling. There is no particular lower limit on the amount of outgassing when the resin particles are heated at 250°C for 10 minutes. The amount of outgassing when the resin particles are heated at 250°C for 10 minutes may be 0 ppm or more, 5 ppm or more, or 10 ppm or more. The range of the amount of outgassing when the resin particles are heated at 250°C for 10 minutes can be set by appropriately selecting the above lower limit and upper limit.

The amount of outgassing when the above resin particles are heated at 250°C for 10 minutes can be measured, for example, as follows.

Two samples are prepared: 5 mg of the resin particles and a known weight of toluene (toluene solution of known concentration). Using a thermal desorption device, 5 mg of the resin particles are heated at 250°C for 10 minutes while passing helium gas at a flow rate of 20 mL/min, and the generated component (A) is adsorbed and collected in a glass tube filled with an adsorbent. While passing helium gas through the glass tube in which component (A) is collected, the glass tube in which component (A) is collected is heated at 350°C for 40 minutes, and the components desorbed from the adsorbent are directly introduced into a gas chromatograph mass spectrometer and analyzed. Using a thermal desorption device, while passing helium gas at a flow rate of 20 mL/min, the known weight of toluene is heated at 250°C for 10 minutes, and the generated component (B) is adsorbed and collected in a glass tube filled with an adsorbent. While helium gas is passed through the glass tube in which component (B) is collected, the glass tube in which component (B) is collected is heated at 350°C for 40 minutes, and the components desorbed from the adsorbent are directly introduced into a gas chromatograph mass spectrometer and analyzed. The peak area values of each component detected when the resin particles are used are compared with the peak area values detected when the known weight of toluene is used, and the amount of outgassing when the resin particles are heated at 250°C for 10 minutes is calculated.

The above known weight of toluene may be 5 mg of toluene.

More specifically, the amount of outgassing when the above resin particles are heated at 250°C for 10 minutes is measured as follows.

A sample (5 mg of resin particles or a known weight of toluene) is sealed in a sample tube and heated at 250°C for 10 minutes while helium gas is passed through the sample tube at a flow rate of 20 mL/min. The components volatilized by heating are adsorbed and collected in a glass tube filled with a collector (e.g., TENAX-TA). While helium gas is passed through the glass tube in which the volatilized components have been collected, the glass tube is heated at 350°C for 40 minutes. The components desorbed from the adsorbent by heating are introduced directly into a gas chromatograph mass spectrometer (hereinafter referred to as GC/MS) and analyzed (ATD-GC/MS). Examples of equipment and analytical conditions used for the above measurements are as follows:

[ATD-GC/MS]
Thermal desorption device: PerkinElmer "TurboMatrix 350"
GC: Agilent Technologies "7890A"
MS: "JMS-Q1000GCQ" manufactured by JEOL Ltd.
Column: SUPELCO "EQUITY-1 60 m x 0.25 mm ID x 0.25 μm"

<Conditions for thermal desorption equipment>
Sample tube heating temperature: 250°C
Heating time: 10 minutes Helium gas flow rate: 20 mL/min Cold trap temperature: 4°C
Desorption temperature and time from collection tube (glass tube): 350°C and 40 minutes Split: inlet; 25 mL/min, outlet; 25 mL/min

<GC/MS conditions>
Carrier gas: Helium, contact flow Column flow rate: 1.5 mL
Split ratio: 1:30
Initial oven temperature: 40°C
Hold time: 4 minutes Heating rate: 10°C/minute Final temperature: 300°C
Hold time: 10 minutes MS: EI mode, 70 eV, transfer line: 250°C, ion source: 230°C

The sum of the peak area values of each component detected when using the above resin particles is compared with the peak area value detected when using a toluene solution of known concentration (known weight of toluene, for example, "VOCs Mixed Standard Stock Solution III" manufactured by Kanto Chemical Co., Inc.). This allows the concentration of volatile components (outgassing) from the resin particles to be calculated in toluene terms. In the present invention, the amount of outgassing (ppm) when resin particles are heated at 250°C for 10 minutes is calculated using the following formula.

Outgassing amount (ppm) = [(sum of peak areas of volatile components from resin particles) / (toluene peak area) x toluene concentration in toluene solution (μg/g) x measured amount of toluene solution (g)] / resin particle weight

Methods for adjusting the amount of outgassing within a preferred range when the resin particles are heated at 250°C for 10 minutes include using the preferred polymerizable component described above, adjusting the molecular weight of the polymerizable component, using the preferred crosslinking agent described above, adjusting the polymerization temperature and polymerization time, applying pressure during polymerization, and washing away unreacted polymerizable components (monomers).

The use of the resin particles is not particularly limited. The resin particles are suitable for a variety of applications. The resin particles are preferably used as spacers. The resin particles are preferably resin particles for spacers. The resin particles may be used as spacers in resin materials. Examples of the spacers include spacers for liquid crystal display elements, gap control spacers, and stress relief spacers. The gap control spacers can be used for gap control of stacked chips to ensure standoff height and flatness, and for gap control of optical components to ensure smoothness of glass surfaces and thickness of adhesive layers. The stress relief spacers can be used for stress relief of sensor chips and the like, and for stress relief of adhesive layers bonding two adherends.

The resin particles are preferably used as spacers for liquid crystal display elements, and are preferably used in a peripheral sealant for liquid crystal display elements. In the peripheral sealant for liquid crystal display elements, the resin particles preferably function as spacers. Because the resin particles have good compressive deformation characteristics, when the resin particles are used as spacers and placed between substrates, the resin particles are efficiently placed between the substrates. Furthermore, the resin particles can prevent scratches on liquid crystal display element components, etc., so display defects are less likely to occur in liquid crystal display elements using the liquid crystal display element spacers.

Furthermore, the resin particles are also suitable for use as inorganic fillers, toner additives, shock absorbers, or vibration absorbers. For example, the resin particles can be used as a substitute for rubber or springs. The resin particles may also be used to obtain the metal-coated particles described below.

The content of the polymer of the polymerizable component in 100% by weight of the resin particles is preferably 80% by weight or more, more preferably 85% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. When the content of the polymer of the polymerizable component is equal to or greater than the above lower limit, the 20% K value of the resin particles at 25°C and 200°C can be easily adjusted within a preferred range, further improving the gap controllability of the connection structure when exposed to a high-temperature environment. There is no particular upper limit to the content of the polymer of the polymerizable component in 100% by weight of the resin particles. The content of the polymer of the polymerizable component in 100% by weight of the resin particles may be equal to or less than 100% by weight (total amount). The range of the content of the polymer of the polymerizable component in 100% by weight of the resin particles can be set by appropriately selecting the above lower limit and upper limit.

With respect to 100% by weight of the polymerizable component, the content of the divinylbenzene is preferably 20% by weight or more, more preferably 25% by weight or more, even more preferably 30% by weight or more, particularly preferably 40% by weight or more, and most preferably 45% by weight or more, and is preferably 80% by weight or less, more preferably 75% by weight or less, even more preferably 70% by weight or less, particularly preferably 65% by weight or less, and most preferably 60% by weight or less. When the content of the divinylbenzene is above the above lower limit and below the above upper limit, the effects of the present invention can be more effectively exerted, and the conductivity reliability of the connection structure after thermal cycling can be further improved. When the content of the divinylbenzene is above the above lower limit, the heat resistance of the resin particles can be improved. When the content of the divinylbenzene is below the above upper limit, the amount of remaining unreacted polymerizable component (monomer) can be reduced.

The content of the (meth)acrylate compound having four or more (meth)acryloyl groups in 100% by weight of the polymerizable component is preferably 20% by weight or more, more preferably 25% by weight or more, even more preferably 30% by weight or more, even more preferably 35% by weight or more, particularly preferably 40% by weight or more, and most preferably 45% by weight or more, and is preferably 80% by weight or less, more preferably 75% by weight or less, even more preferably 70% by weight or less, even more preferably 65% by weight or less, even more preferably 60% by weight or less, particularly preferably 55% by weight or less, and most preferably 50% by weight or less. When the content of the (meth)acrylate compound having four or more (meth)acryloyl groups is above the above lower limit and below the above upper limit, the effects of the present invention can be more effectively exerted, and the conductivity reliability of the connection structure after thermal cycling can be further improved. When the content of the (meth)acrylate compound having four or more (meth)acryloyl groups is above the above lower limit, the degree of crosslinking of the resin particles can be increased. When the content of the (meth)acrylate compound having four or more (meth)acryloyl groups is equal to or less than the above upper limit, the heat resistance of the resin particles can be improved.

With respect to 100% by weight of the polymerizable component, the total content of the divinylbenzene and the (meth)acrylate compound having four or more (meth)acryloyl groups is preferably 80% by weight or more, more preferably 85% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more. When the total content of the divinylbenzene and the (meth)acrylate compound having four or more (meth)acryloyl groups is equal to or greater than the above lower limit, the effects of the present invention can be more effectively achieved. There is no particular upper limit to the total content of the divinylbenzene and the (meth)acrylate compound having four or more (meth)acryloyl groups. With respect to 100% by weight of the polymerizable component, the total content of the divinylbenzene and the (meth)acrylate compound having four or more (meth)acryloyl groups may be 100% by weight or less (total amount), or may be less than 100% by weight. The range of the total content of the divinylbenzene and the (meth)acrylate compound having four or more (meth)acryloyl groups per 100% by weight of the polymerizable component can be set by appropriately selecting the lower limit and upper limit.

The weight ratio of the content of the divinylbenzene in the polymerizable component to the content of the (meth)acrylate compound having four or more (meth)acryloyl groups in the polymerizable component is defined as the weight ratio (content of divinylbenzene/content of (meth)acrylate compound having four or more (meth)acryloyl groups). The weight ratio (content of divinylbenzene/content of (meth)acrylate compound having four or more (meth)acryloyl groups) is preferably 0.30 or more, more preferably 0.40 or more, even more preferably 0.50 or more, even more preferably 0.60 or more, particularly preferably 0.70 or more, and most preferably 0.80 or more, and is preferably 10.00 or less, more preferably 5.00 or less, even more preferably 4.00 or less, even more preferably 3.00 or less, particularly preferably 2.00 or less, and most preferably 1.50 or less. When the weight ratio (divinylbenzene content/(meth)acrylate compound content having four or more (meth)acryloyl groups) is equal to or greater than the lower limit and equal to or less than the upper limit, the effects of the present invention can be more effectively achieved. When the weight ratio (divinylbenzene content/(meth)acrylate compound content having four or more (meth)acryloyl groups) is equal to or greater than the lower limit, the heat resistance of the resin particles can be improved. When the weight ratio (divinylbenzene content/(meth)acrylate compound content having four or more (meth)acryloyl groups) is equal to or less than the upper limit, the degree of crosslinking of the resin particles can be increased, and the amount of remaining unreacted polymerizable component (monomer) can be reduced.

(metal coated particles)
The metal-coated particles according to the present invention comprise the resin particles described above and a metal coating layer disposed on the surface of the resin particles. Because the metal-coated particles according to the present invention have the above-described configuration, when used as spacers, the metal-coated particles can improve the gap controllability of a connection structure when exposed to a high-temperature environment and can also improve the conduction reliability of the connection structure after thermal cycling.

In particular, the resin particles are preferably used to form a metal coating layer on their surfaces to obtain metal-coated particles having the metal coating layer, or the resin particles have a particle diameter of 5 μm or more and 100 μm or less. In this case, when a resin material using the resin particles or metal-coated particles is cured, the occurrence of cracks in the cured product can be suppressed. Furthermore, when a connection structure using the resin material is exposed to a high-temperature environment, the gap controllability of the connection structure can be significantly improved. Furthermore, the conductivity reliability of the connection structure after thermal cycling can be significantly improved. To achieve these effects even more effectively, the resin particles are more preferably used to form a metal coating layer on their surfaces to obtain metal-coated particles having the metal coating layer, or the resin particles have a particle diameter of 10 μm or more and 100 μm or less. To achieve these effects even more effectively, the resin particles are more preferably used to form a metal coating layer on their surfaces to obtain metal-coated particles having the metal coating layer, or the resin particles have a particle diameter of 20 μm or more and 100 μm or less.

In particular, the resin particles are preferably used to obtain metal-coated particles having the metal coating layer by forming a metal coating layer on the surface (use of the resin particles to obtain metal-coated particles having the metal coating layer by forming a metal coating layer on the surface). In this case, when the resin material using the metal-coated particles is cured, the occurrence of cracks in the cured product can be suppressed, and when a connection structure using the resin material is exposed to a high-temperature environment, the gap controllability of the connection structure can be significantly improved. Furthermore, the conductivity reliability of the connection structure after thermal cycling can be significantly improved.

Figure 2 is a cross-sectional view schematically showing metal-coated particles using resin particles according to the first embodiment of the present invention.

The metal-coated particle 11 shown in Figure 2 has a resin particle 1 and a metal coating layer 2 disposed on the surface of the resin particle 1. The metal coating layer 2 coats the surface of the resin particle 1. The metal-coated particle 11 is a coated particle in which the surface of the resin particle 1 is coated with the metal coating layer 2.

The compressive modulus of elasticity when the metal-coated particles are compressed 20% at 200°C (20% K value of the metal-coated particles at 200°C) is preferably 1000 N/mm2 or ^more , more preferably 1500 N/mm2 ^{or more} , and even more preferably 2000 N/mm2 or ^more , and is preferably 20,000 N/mm2 or ^less , more preferably 10,000 N/mm2 or ^less , and even more preferably 6,000 N/mm2 ^or less. When the 20% K value of the metal-coated particles at 200°C is the above-mentioned lower limit or more, the gap controllability of the connection structure when exposed to a high-temperature environment can be further improved. When the 20% K value of the metal-coated particles at 200°C is the above-mentioned upper limit or less, destruction of the metal-coated particles in the connection structure when exposed to a high-temperature environment can be further prevented.

The compressive modulus of the metal-coated particles when compressed 20% at 25°C (20% K value of the metal-coated particles at 25°C) is preferably 1500 N/mm2 or ^more , more preferably 2000 N/mm2 or ^more , even more preferably 2500 N/ ^mm2 or more, and preferably 20000 N/mm2 or ^less , more preferably 15000 N/mm2 or ^less , and even more preferably 8000 N/mm2 ^or less. When the 20% K value of the metal-coated particles at 25°C is the above-mentioned lower limit or more, the gap controllability of the connection structure when exposed to a high-temperature environment can be further improved. When the 20% K value of the metal-coated particles at 25°C is the above-mentioned upper limit or less, the metal-coated particles can better follow the connection target members (substrates, etc.), and the gap controllability can be further improved.

The ratio of the compressive modulus when the metal-coated particle is compressed 20% at 25°C to the compressive modulus when the metal-coated particle is compressed 20% at 200°C is defined as the ratio (20% K value of metal-coated particle at 25°C/20% K value of metal-coated particle at 200°C). This ratio (20% K value of metal-coated particle at 25°C/20% K value of metal-coated particle at 200°C) is preferably 0.7 or more, more preferably 0.9 or more, even more preferably 1.0 or more, and is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. When the ratio (20% K value of metal-coated particle at 25°C/20% K value of metal-coated particle at 200°C) is equal to or greater than the above lower limit and equal to or less than the above upper limit, the gap controllability of the connection structure when exposed to a high-temperature environment can be further improved.

The 20% K values of the above metal-coated particles at 25°C and 200°C can be measured as follows.

Using a micro-compression testing machine, the metal-coated particles are compressed with the smooth end face of a cylindrical indenter (diameter 50 μm, made of diamond) at 25°C or 100°C under conditions where a maximum test load of 90 mN is applied for 30 seconds. The load value (N) and compression displacement (mm) at this time are measured. From the obtained measured values, the compressive modulus can be calculated using the following formula. Examples of micro-compression testing machines that can be used include the Fischerscope H-100 manufactured by Fischer and the ENT-5 manufactured by Elionix.

20% K value (N/mm ² ) = (3/2 ^1/2 )·F·S ^{- 3/2} ·R ^{- 1/2}
F: Load value (N) when the metal-coated particle is compressed and deformed by 20%
S: Compression displacement (mm) when the metal-coated particle is compressed and deformed by 20%
R: radius of metal-coated particle (mm)

In order to further improve the effects of the present invention, the compression recovery rate of the metal-coated particles at 25°C is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more, and is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less.

The compression recovery rate can be measured as follows.

Metal-coated particles are scattered on a sample stage. Using a micro-compression testing machine, a load (reversed load value) is applied to each scattered metal-coated particle at 25°C with the smooth end face of a cylindrical (diameter 100 μm, made of diamond) in the direction of the center of the metal-coated particle until the metal-coated particle is compressed by 40%. The load is then released to the origin load value (0.40 mN). The load-compression displacement during this period is measured, and the compression recovery rate can be calculated using the formula below. The loading rate is 0.33 mN/sec. Examples of micro-compression testing machines that can be used include the Fischerscope H-100 manufactured by Fischer and the ENT-5 manufactured by Elionix.

Compression recovery rate (%) = (L2/L1) x 100
L1: Compression displacement from the load value for origin when applying a load to the reverse load value. L2: Unloading displacement from the reverse load value when releasing the load to the load value for origin.

The particle diameter of the metal-coated particles is preferably 0.5 μm or more, more preferably 1.0 μm or more, even more preferably 2 μm or more, even more preferably 5 μm or more, particularly preferably 10 μm or more, and most preferably 20 μm or more, and is preferably 300 μm or less, more preferably 100 μm or less, even more preferably 70 μm or less, particularly preferably 50 μm or less, and most preferably 30 μm or less. If the particle diameter of the metal-coated particles is above the above lower limit or below the above upper limit, agglomerated metal-coated particles are less likely to form when the metal coating layer is formed, the gap between the substrates (connection target components) does not become too large, and the metal coating layer is less likely to peel off from the surface of the resin particles.

The particle diameter of the metal-coated particles is preferably 5 μm or greater, since this can suppress the occurrence of cracks in the cured product, particularly when a resin material using the metal-coated particles is cured, and can significantly improve the gap controllability of the connection structure when the connection structure using the resin material is exposed to a high-temperature environment. These effects are even more effectively achieved, so the particle diameter of the metal-coated particles is more preferably 10 μm or greater, and even more preferably 20 μm or greater. Furthermore, when the resin material is a solder paste, these effects are even more effectively achieved. The particle diameter of the metal-coated particles is preferably 5 μm or greater but 100 μm or less, more preferably 10 μm or greater but 100 μm or less, and even more preferably 20 μm or greater but 100 μm or less. Furthermore, from the perspective of significantly improving the conductivity reliability of the connection structure after thermal cycling, the particle diameter of the metal-coated particles is preferably 10 μm or greater.

The inventors have discovered that, in order to achieve the effects of the present invention more effectively, it is important to 1) use a specific polymerizable component for the resin particles, 2) control the compressive modulus of the resin particles in the metal-coated particles within a specific range, and 3) control the particle size of the metal-coated particles within a specific range; in other words, it is important to combine these three requirements.

The particle size of the above-mentioned metal-coated particles refers to the diameter if the metal-coated particles are spherical, and if the metal-coated particles are in a shape other than spherical, refers to the diameter when assumed to be a perfect sphere with a volume equivalent to that of the particles.

The particle diameter of the metal-coated particles is preferably an average particle diameter, and more preferably a number-average particle diameter. Furthermore, the effect is even more pronounced when the lower and upper limits of the number-average particle diameter of the metal-coated particles satisfy the preferred lower and upper limits of the particle diameter of the metal-coated particles. The particle diameter of the metal-coated particles can be determined, for example, by observing 50 random metal-coated particles with an electron microscope or optical microscope and calculating the average particle diameter of each metal-coated particle, or by performing laser diffraction particle size distribution measurement. When observed with an electron microscope or optical microscope, the particle diameter of each metal-coated particle is determined as the particle diameter in equivalent circle diameter. When observed with an electron microscope or optical microscope, the average particle diameter in equivalent circle diameter of 50 random metal-coated particles is approximately equal to the average particle diameter in equivalent sphere diameter. When observed with a laser diffraction particle size distribution measurement, the particle diameter of each metal-coated particle is determined as the particle diameter in equivalent sphere diameter. The particle diameter of the metal-coated particles is preferably calculated using laser diffraction particle size distribution measurement.

The metal used to form the metal coating layer is not particularly limited. Examples of the metal include gold, silver, palladium, copper, platinum, zinc, iron, tin, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, thallium, germanium, cadmium, silicon, tungsten, molybdenum, and alloys thereof. Other examples of the metal include tin-doped indium oxide (ITO) and solder. From the perspective of further improving the reliability of connections between electrodes, the metal is preferably a tin-containing alloy, nickel, palladium, copper, or gold, and more preferably nickel or palladium.

Like metal-coated particle 11, the metal coating layer may be formed from a single layer. The metal coating layer may also be formed from multiple layers. That is, the metal coating layer may have a laminated structure of two or more layers. When the metal coating layer is formed from multiple layers, the outermost layer is preferably a gold layer, a nickel layer, a palladium layer, a copper layer, or an alloy layer containing tin and silver, and more preferably a gold layer. When the outermost layer is one of these preferred metal coating layers, the connection reliability between electrodes can be further improved. Furthermore, when the outermost layer is a gold layer, corrosion resistance can be further improved.

The method for forming the metal coating layer on the surface of the resin particles is not particularly limited. Examples of methods for forming the metal coating layer include electroless plating, electroplating, physical vapor deposition, and coating the surface of the resin particles with a metal powder or a paste containing a metal powder and a binder. From the perspective of forming the metal coating layer more easily, electroless plating is preferred. Examples of physical vapor deposition methods include vacuum deposition, ion plating, and ion sputtering.

The thickness of the metal coating layer is preferably 0.005 μm or more, more preferably 0.01 μm or more, even more preferably 0.05 μm or more, even more preferably 0.1 μm or more, particularly preferably 0.15 μm or more, and most preferably 0.2 μm or more, and is preferably 10 μm or less, more preferably 1 μm or less, and even more preferably 0.3 μm or less. The thickness of the metal coating layer refers to the thickness of the entire metal coating layer if the metal coating layer is multi-layered. When the thickness of the metal coating layer is above the above lower limit and below the above upper limit, the metal-coated particles do not become too hard and can sufficiently deform between substrates (connection target components). In particular, when the thickness of the metal coating layer is 0.2 μm or more, the effects of the present invention can be more effectively exerted, and the conductivity reliability of the connection structure after thermal cycling can be further improved.

When the metal coating layer is formed from multiple layers, the thickness of the outermost metal coating layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, and preferably 0.5 μm or less, more preferably 0.1 μm or less. When the thickness of the outermost metal coating layer is equal to or greater than the above-mentioned lower limit and equal to or less than the above-mentioned upper limit, the coating by the outermost metal coating layer becomes uniform, corrosion resistance becomes sufficiently high, and the connection reliability between electrodes can be further improved. Furthermore, when the outermost layer is a gold layer, the thinner the gold layer, the lower the cost.

The thickness of the metal coating layer can be measured by observing the cross section of the metal-coated particle using, for example, a transmission electron microscope (TEM). It is preferable to calculate the thickness of the metal coating layer by averaging the thickness of five arbitrary metal coating layers, and it is more preferable to calculate the average thickness of the entire metal coating layer as the thickness of the metal coating layer of one metal-coated particle. It is preferable to determine the thickness of the metal coating layer by calculating the average thickness of the metal coating layer for 50 arbitrary metal-coated particles. It is preferable that the thickness of the metal coating layer is an average thickness.

(Resin material)
The resin material according to the present invention is a resin material containing the resin particles described above and a binder resin, or a resin material containing metal-coated particles having the resin particles and a metal coating layer disposed on the surface of the resin particles, and a binder resin. In the resin material according to the present invention, the resin particles or the metal-coated particles are dispersed in the binder resin. Because the resin material according to the present invention has the above configuration, it is possible to improve the gap controllability of the connection structure when exposed to a high-temperature environment and to improve the conduction reliability of the connection structure after thermal cycling.

The resin material preferably further contains conductive particles. The resin material preferably further contains conductive particles different from the metal-coated particles. The conductive particles are different from the resin particles. The resin material is preferably a conductive material further containing conductive particles. The resin material is preferably a conductive material. When the resin material is a conductive material, the resin material is suitably used for electrical connection between electrodes. The resin material is preferably a circuit connection material. When the resin material further contains conductive particles, the resin material can be used as a conductive paste, a conductive film, etc. When the resin material according to the present invention is a conductive film, a film not containing conductive particles may be laminated on a conductive film containing conductive particles. The conductive paste is preferably an isotropic conductive paste. The conductive film is preferably an isotropic conductive film.

The resin particles are preferably used together with conductive particles, more preferably together with solder particles. The metal-coated particles are preferably used together with conductive particles, more preferably together with solder particles. The resin material preferably contains the resin particles or the metal-coated particles and the conductive particles, more preferably the resin particles or the metal-coated particles and the solder particles. The metal-coated particles are preferably different from the solder particles and preferably do not contain solder. By using the conductive particles (solder particles, etc.) in addition to the resin particles or the metal-coated particles, the effects of the present invention can be more effectively exerted and the conductivity reliability of the connection structure after thermal cycling can be further improved.

The present specification also discloses the following invention: Use of the above-mentioned resin particles, or the above-mentioned resin particles and metal-coated particles disposed on the surfaces of the above-mentioned resin particles, in a solder paste containing solder particles and a binder resin.

The content of the resin particles or metal-coated particles in 100% by weight of the resin material (solder paste) is preferably 0.1% by weight or more, more preferably 1% by weight or more, even more preferably 2% by weight or more, particularly preferably 5% by weight or more, and most preferably 10% by weight or more, and is preferably 80% by weight or less, more preferably 60% by weight or less, and even more preferably 50% by weight or less. When the content of the resin particles or metal-coated particles is above the above lower limit and below the above upper limit, the effects of the present invention can be more effectively exerted, and the conductivity reliability of the connection structure after thermal cycling can be further improved.

The conductive particles may be solder particles or metal particles. The metal particles may be metal powder. The conductive particles may include a base particle and a conductive portion disposed on the surface of the base particle. From the perspective of further improving the conductivity reliability of the connection structure after thermal cycling, the conductive particles are preferably solder particles. From the perspective of further improving the conductivity reliability of the connection structure after thermal cycling, the resin material preferably further contains solder particles. From the perspective of further improving the conductivity reliability of the connection structure after thermal cycling, the resin material is preferably a solder paste containing solder particles. The solder paste contains the above-mentioned components of the resin material.

The solder particles are formed of solder at both their center and outer surface. The solder particles are particles in which both their center and outer surface are solder.

The solder is preferably a metal (low-melting-point metal) with a melting point of 450°C or less. The solder particles are preferably metal particles (low-melting-point metal particles) with a melting point of 450°C or less. The low-melting-point metal particles are particles containing a low-melting-point metal. The low-melting-point metal refers to a metal with a melting point of 450°C or less. The melting point of the low-melting-point metal is preferably 300°C or less, more preferably 220°C or less, and even more preferably 190°C or less.

The melting point of the solder particles is preferably 100°C or higher, more preferably 105°C or higher, and preferably 250°C or lower, more preferably 245°C or lower. When the melting point of the solder particles is above the above lower limit and below the above upper limit, the cohesion of the solder during conductive connection can be more effectively improved. When the melting point of the solder particles is above the above lower limit and below the above upper limit, when electrodes are electrically connected using a resin material (conductive material), the conductivity reliability can be more effectively improved and the insulation reliability can be more effectively improved. The melting point range of the solder particles can be set by appropriately selecting the above lower limit and upper limit.

The melting point of the solder particles can be determined by differential scanning calorimetry (DSC). Examples of differential scanning calorimetry (DSC) devices include the EXSTAR DSC7020 manufactured by SII Corporation.

Furthermore, the solder particles preferably contain tin. The tin content of 100% by weight of the metal contained in the solder particles is preferably 30% by weight or more, more preferably 40% by weight or more, even more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the tin content in the solder particles is equal to or greater than the above lower limit, the connection reliability between the solder portion and the electrode can be more effectively improved. The tin content of 100% by weight of the metal contained in the solder particles may be equal to or less than 100% by weight. The range of the tin content of 100% by weight of the metal contained in the solder particles can be set by appropriately selecting the above lower limit and upper limit.

The tin content can be measured using a high-frequency inductively coupled plasma optical emission spectrometer ("ICP-AES" manufactured by Horiba, Ltd.) or an X-ray fluorescence spectrometer ("EDX-800HS" manufactured by Shimadzu Corporation).

By using the above solder particles, the solder melts and bonds to the electrodes, and the solder portion provides electrical conductivity between the electrodes. For example, the solder portion and electrode are more likely to make surface contact rather than point contact, which reduces connection resistance. Furthermore, the use of the above solder particles increases the bonding strength between the solder portion and electrode, making it even less likely for the solder portion and electrode to peel off, thereby more effectively improving electrical continuity and connection reliability.

The low-melting point metal constituting the solder particles is not particularly limited. The low-melting point metal is preferably tin or an alloy containing tin. Examples of such alloys include tin-silver alloys, tin-copper alloys, tin-silver-copper alloys, tin-bismuth alloys, tin-zinc alloys, and tin-indium alloys. Because of their excellent wettability with electrodes, the low-melting point metal is preferably tin, tin-silver alloys, tin-silver-copper alloys, tin-bismuth alloys, or tin-indium alloys. It is more preferable that the low-melting point metal be a tin-bismuth alloy or a tin-indium alloy.

The solder particles are preferably filler metal with a liquidus temperature of 450°C or less, based on JIS Z3001: Welding Terminology. Examples of the composition of the solder particles include metal compositions containing zinc, gold, silver, lead, copper, tin, bismuth, indium, etc. The solder particles preferably do not contain lead, and preferably contain tin and indium, or tin and bismuth.

In order to more effectively increase the bond strength between the solder portion and the electrode, the solder particles may contain metals such as nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, phosphorus, germanium, tellurium, cobalt, bismuth, manganese, chromium, molybdenum, and palladium. Furthermore, from the perspective of even more effectively increasing the bond strength between the solder portion and the electrode, the solder particles preferably contain nickel, copper, antimony, aluminum, or zinc. In order to even more effectively increase the bond strength between the solder portion and the electrode, the content of these metals in the solder particles to increase the bond strength is preferably 0.0001% by weight or more, and preferably 1% by weight or less, based on 100% by weight of the metals contained in the solder particles.

The average particle diameter of the solder particles is preferably 0.01 μm or more, more preferably 0.03 μm or more. If the average particle diameter of the solder particles is equal to or greater than the above-mentioned lower limit, the solder can be arranged on the electrode more efficiently. The average particle diameter of the solder particles may be 10 μm or less, 5 μm or less, or 3 μm or less. The range of the average particle diameter of the solder particles can be set by appropriately selecting the above-mentioned lower limit and upper limit.

The average particle diameter of the solder particles is the number average particle diameter. The average particle diameter of the solder particles can be determined, for example, by observing 50 random solder particles with an electron microscope or optical microscope and calculating the average particle diameter of each solder particle, or by performing laser diffraction particle size distribution measurement. When observed with an electron microscope or optical microscope, the particle diameter of each solder particle is determined as the particle diameter in equivalent circle diameter. When observed with an electron microscope or optical microscope, the average particle diameter of 50 random solder particles in equivalent circle diameter is approximately equal to the average particle diameter in equivalent sphere diameter. When using laser diffraction particle size distribution measurement, the particle diameter of each solder particle is determined as the particle diameter in equivalent sphere diameter. The average particle diameter of the solder particles is preferably calculated using laser diffraction particle size distribution measurement.

The coefficient of variation (CV value) of the particle diameter of the solder particles is preferably 40% or less, and more preferably 30% or less. When the coefficient of variation of the particle diameter of the solder particles is equal to or less than the above upper limit, the solder can be arranged on the electrode more efficiently. The coefficient of variation (CV value) of the particle diameter of the solder particles may be 0% or more, 1% or more, 5% or more, or 10% or more. However, the CV value of the particle diameter of the solder particles may be less than 5%. The range of the coefficient of variation of the particle diameter of the solder particles can be set by appropriately selecting the above lower limit and upper limit.

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

CV value (%) = (ρ/Dn) × 100
ρ: Standard deviation of solder particle diameter Dn: Average value of solder particle diameter

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

The content of the solder particles in 100% by weight of the resin material (solder paste) is preferably 1% by weight or more, more preferably 2% by weight or more, even more preferably 10% by weight or more, particularly preferably 20% by weight or more, and most preferably 30% by weight or more, and is preferably 80% by weight or less, more preferably 60% by weight or less, and even more preferably 50% by weight or less. When the content of the solder particles is above the above lower limit and below the above upper limit, solder can be more efficiently arranged on the electrodes, making it easier to arrange a large amount of solder between the electrodes, and the conductivity reliability of the connection structure after thermal cycling can be more effectively improved. From the perspective of more effectively improving conductivity reliability, a higher content of the solder particles is preferable.

The binder resin is not particularly limited. Known insulating resins can be used as the binder resin. The binder resin preferably contains a thermoplastic component (thermoplastic compound) or a curable component, and more preferably contains a curable component. Examples of the curable component include a photocurable component and a thermosetting component. The photocurable component preferably contains a photocurable compound and a photopolymerization initiator. The thermosetting component preferably contains a thermosetting compound and a thermosetting agent. Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, and elastomers. Only one type of binder resin can be used, or two or more types can be used in combination.

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

In addition to the resin particles or metal-coated particles and the binder resin, the resin material may also contain various additives such as fillers, extenders, softeners, plasticizers, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, UV absorbers, lubricants, antistatic agents, and flame retardants.

The resin particles or metal-coated particles can be dispersed in the binder resin by any conventionally known dispersion method. Examples of methods for dispersing the resin particles or metal-coated particles in the binder resin include the following: A method in which the resin particles or metal-coated particles are added to the binder resin and then kneaded and dispersed using a planetary mixer or the like; A method in which the resin particles or metal-coated particles are uniformly dispersed in water or an organic solvent using a homogenizer or the like, then added to the binder resin, and then kneaded and dispersed using a planetary mixer or the like; A method in which the binder resin is diluted with water or an organic solvent, and then the resin particles or metal-coated particles are added, and then kneaded and dispersed using a planetary mixer or the like.

The viscosity (η25) of the resin material at 25°C is preferably 30 Pa·s or more, more preferably 50 Pa·s or more, and preferably 400 Pa·s or less, more preferably 300 Pa·s or less. When the viscosity of the resin material at 25°C is above the above lower limit and below the above upper limit, the connection reliability between electrodes can be more effectively improved. The viscosity (η25) can be adjusted appropriately by changing the types and amounts of the blended components.

The viscosity (η25) is measured, for example, using an E-type viscometer at 25°C and 10 rpm. Examples of E-type viscometers include the "VISCOMETER TV-22" manufactured by Toki Sangyo Co., Ltd.

The content of the binder resin, based on 100% by weight of the resin material, is preferably 10% by weight or more, more preferably 30% by weight or more, even more preferably 50% by weight or more, and particularly preferably 70% by weight or more, and is preferably 99.99% by weight or less, even more preferably 99.9% by weight or less, even more preferably 99% by weight or less, even more preferably 98% by weight or less, even more preferably 90% by weight or less, even more preferably 80% by weight or less, particularly preferably 70% by weight or less, and most preferably 65% by weight or less. When the content of the binder resin is above the above lower limit and below the above upper limit, the effects of the present invention can be more effectively exerted, and the conductivity reliability of the connection structure after thermal cycling can be further improved. Furthermore, when the content of the binder resin is above the above lower limit and below the above upper limit, conductive particles or metal-coated particles are efficiently arranged between the electrodes, and the connection reliability of the connection target components connected by the resin material is further improved.

(Connection structure)
A connection structure can be obtained by connecting connection target members using the resin particles described above.

The connection structure using the resin particles includes a first connection target member, a second connection target member, and a connection portion connecting the first connection target member and the second connection target member. In the connection structure, the connection portion contains the resin particles or the metal-coated particles. In the connection structure, it is preferable that the connection portion is formed from the resin particles or the metal-coated particles, or from a composition containing the resin particles.

Furthermore, a connection structure can be obtained by connecting components to be connected using a conductive material containing the above-mentioned resin particles or metal-coated particles, a binder resin, and conductive particles.

The connection structure has the above configuration, which improves the gap controllability of the connection structure when exposed to a high-temperature environment and also improves the conductivity reliability after thermal cycling.

The connection structure using the resin particles or the metal-coated particles comprises a first connection target member having a first electrode on its surface, a second connection target member having a second electrode on its surface, and a connection portion connecting the first connection target member and the second connection target member. In the connection structure, the connection portion contains the resin particles. In the connection structure, the connection portion is preferably formed from a resin material (conductive material) containing the resin particles or the metal-coated particles, conductive particles, and a binder resin. The conductive particles are preferably solder particles. The resin material is preferably a solder paste containing solder particles. When the connection portion is formed from a resin material (conductive material) containing the resin particles or the metal-coated particles, conductive particles, and a binder resin, in the connection structure, it is preferable that the first electrode and the second electrode are electrically connected by the conductive particles. If the connection portion is formed from a resin material (solder paste) containing the resin particles or the metal-coated particles, solder particles, and a binder resin, it is more preferable that the first electrode and the second electrode in the connection structure are electrically connected by a solder portion.

From the viewpoint of further improving the conductivity reliability after thermal cycling and increasing the dispersibility of each component in the conductive material, it is more preferable that the connection portion of the above-mentioned connection structure be formed from a resin material (conductive material) containing the above-mentioned metal-coated particles, conductive particles, and a binder resin. From the viewpoint of further improving the conductivity reliability after thermal cycling and increasing the dispersibility of each component in the conductive material, it is even more preferable that the connection portion of the above-mentioned connection structure be formed from a resin material (solder paste) containing the above-mentioned metal-coated particles, solder particles, and a binder resin.

Figure 3 is a cross-sectional view showing an example of a connection structure obtained using resin particles according to the first embodiment of the present invention.

The connection structure 41 shown in Figure 3 comprises a first member to be connected 42, a second member to be connected 43, and a connection portion 44 connecting the first member to be connected 42 and the second member to be connected 43. The connection portion 44 is formed from a resin material (solder paste) containing resin particles 1, solder particles, and a binder resin. The resin particles 1 are used as spacers. The resin particles 1 control the distance between the first member to be connected 42 and the second member to be connected 43.

Figure 4 is a cross-sectional view showing an example of a connection structure obtained using metal-coated particles made from resin particles according to the first embodiment of the present invention.

The connection structure 51 shown in Figure 4 comprises a first member to be connected 42, a second member to be connected 43, and a connection portion 44 connecting the first member to be connected 42 and the second member to be connected 43. The connection portion 44 is formed from a resin material (solder paste) containing metal-coated particles 11, solder particles, and a binder resin. The metal-coated particles 11 are used as spacers. The metal-coated particles 11 control the distance between the first member to be connected 42 and the second member to be connected 43.

In the connection structures 41 and 51, the connection portion 44 includes a solder portion 3 formed by joining together multiple solder particles, and a resin portion 4 formed from a binder resin. If the binder resin contains a curable component, the resin portion is preferably a cured portion of the binder resin.

The first connection target member 42 has a plurality of first electrodes 42a on its surface (top surface). The second connection target member 43 has a plurality of second electrodes 43a on its surface (bottom surface). The first electrodes 42a and second electrodes 43a are electrically connected by solder portions 3. Therefore, the first connection target member 42 and the second connection target member 43 are electrically connected by solder portions 3. In the connection portion 44, no solder is present in a region (resin portion 4) other than the solder portions 3 gathered between the first electrode 42a and the second electrode 43a. In a region (resin portion 4) other than the solder portions 3, no solder is present apart from the solder portions 3. Note that a small amount of solder may be present in a region (resin portion 4) other than the solder portions 3 gathered between the first electrode 42a and the second electrode 43a.

As shown in Figures 3 and 4, in connection structures 41 and 51, multiple solder particles gather between the first electrode 42a and the second electrode 43a. After the multiple solder particles melt, the molten solder particles wet and spread over the surface of the electrodes before solidifying, forming solder portion 3. This increases the connection area between solder portion 3 and the first electrode 42a, and between solder portion 3 and the second electrode 43a. In other words, the use of solder particles increases the contact area between solder portion 3 and the first electrode 42a, and between solder portion 3 and the second electrode 43a, compared to when conductive particles whose outer surface is made of a metal such as nickel, gold, or copper are used. This increases the conductivity and connection reliability of connection structures 41 and 51 after thermal cycling.

The method for manufacturing the connection structure is not particularly limited. One example of a method for manufacturing a connection structure is to place the resin material (conductive material) between a first member to be connected and a second member to be connected, obtain a laminate, and then heat and pressurize the laminate. The pressure applied during the pressurization is preferably 40 MPa or more, more preferably 60 MPa or more, and preferably 90 MPa or less, more preferably 70 MPa or less. Note that if the conductive material is a solder paste containing solder particles, the connection structure may be manufactured without pressurizing the laminate. The temperature during the heating is preferably 80°C or more, more preferably 100°C or more, and preferably 250°C or less, more preferably 190°C or less.

The first and second connection target members are not particularly limited. Specific examples of the first and second connection target members include electronic components such as semiconductor chips, semiconductor packages, LED chips, LED packages, capacitors, and diodes, as well as electronic components such as resin films, printed circuit boards, flexible printed circuit boards, flexible flat cables, rigid-flexible boards, glass epoxy boards, and glass boards. It is preferable that the first and second connection target members are electronic components.

The resin material is preferably a conductive material for connecting electronic components. The resin material is preferably a conductive paste material, and is preferably applied in paste form onto the components to be connected.

The above-mentioned resin particles, resin material, and circuit connecting material are also suitable for use in touch panels. Therefore, the connection target member is preferably a flexible substrate, or a connection target member in which electrodes are arranged on the surface of a resin film. The connection target member is preferably a flexible substrate, and is preferably a connection target member in which electrodes are arranged on the surface of a resin film. When the flexible substrate is a flexible printed circuit board or the like, the flexible substrate generally has electrodes on its surface.

The electrodes provided on the connection target members include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, SUS electrodes, and tungsten electrodes. When the connection target members are flexible printed circuit boards, the electrodes are preferably gold electrodes, nickel electrodes, tin electrodes, silver electrodes, or copper electrodes. When the connection target members are glass substrates, the electrodes are preferably aluminum electrodes, copper electrodes, molybdenum electrodes, or tungsten electrodes. When the electrodes are aluminum electrodes, they may be formed solely from aluminum, or may be electrodes in which an aluminum layer is laminated on the surface of a metal oxide layer. Examples of materials for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal elements include Sn, Al, and Ga.

The resin particles can also be suitably used as spacers for liquid crystal display elements. When the resin particles are used as spacers for liquid crystal display elements, the gap can be effectively controlled, preventing damage to the substrate. The first connection target member may be a first liquid crystal display element member. The second connection target member may be a second liquid crystal display element member. The connection portion may be a sealing portion that seals the outer peripheries of the first liquid crystal display element member and the second liquid crystal display element member when the first liquid crystal display element member and the second liquid crystal display element member are facing each other.

The resin particles can also be used in a peripheral sealant for liquid crystal display elements. The liquid crystal display element comprises a first liquid crystal display element member and a second liquid crystal display element member. The liquid crystal display element further comprises a seal portion sealing the periphery of the first liquid crystal display element member and the second liquid crystal display element member while the first liquid crystal display element member and the second liquid crystal display element member are facing each other, and liquid crystal disposed inside the seal portion between the first liquid crystal display element member and the second liquid crystal display element member. In this liquid crystal display element, the liquid crystal dropping method is applied, and the seal portion is formed by thermally curing a sealant for the liquid crystal dropping method.

The present invention will be specifically explained below using examples and comparative examples. The present invention is not limited to the following examples.

The following materials were prepared:

(Polymerizable component)
Divinylbenzene (NS Styrene Monomer "DVB960")
Styrene (NS Styrene Monomer "Styrene Monomer")
Methyl methacrylate ("Acryester M" manufactured by Mitsubishi Chemical Corporation, one (meth)acryloyl group)
Ethylene glycol dimethacrylate ("Acryester ED" manufactured by Mitsubishi Chemical Corporation, two (meth)acryloyl groups)
Trimethylolpropane trimethacrylate (Tokyo Chemical Industry Co., Ltd., three (meth)acryloyl groups)
Pentaerythritol tetraacrylate ("A-TMMT" manufactured by Shin-Nakamura Chemical Co., Ltd., four (meth)acryloyl groups)
Dipentaerythritol polyacrylate ("A-DPH" manufactured by Shin-Nakamura Chemical Co., Ltd., 5 to 6 (meth)acryloyl groups)

(Other components (solvents))
Toluene (Fujifilm Wako Pure Chemical Industries, Ltd.)

(Polymerization initiator)
Benzoyl peroxide (Tokyo Chemical Industry Co., Ltd. "BPO")

Example 1
(1) Preparation of Resin Particles 20 parts by weight of pentaerythritol tetraacrylate (20% by weight of 100% by weight of polymerizable components) was added to 80 parts by weight of divinylbenzene (80% by weight of 100% by weight of polymerizable components) and stirred to obtain a monomer solution. Next, 1 part by weight of a polymerization initiator (benzoyl peroxide) was added to the resulting monomer solution and stirred until homogeneous, obtaining a monomer mixture. 200 parts by weight of a 1.0 wt% aqueous solution of polyvinyl alcohol with a molecular weight of approximately 2000 dissolved in pure water was placed in a reactor. The resulting monomer mixture was then added and stirred until the monomer droplets reached the desired particle size. The mixture was then heated at 90°C for 9 hours to polymerize the monomer droplets, yielding particles. The resulting particles were washed three times with hot water and acetone, and then classified to recover the resin particles.

(2) Preparation of Metal-Coated Particles 10 parts by weight of the resin particles were dispersed in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution using an ultrasonic disperser, and the solution was filtered to extract the resin particles. The resin particles were then added to 100 parts by weight of a 1% by weight solution of dimethylamine borane to activate the surfaces of the resin particles. The surface-activated resin particles were thoroughly washed with water, and then added to 500 parts by weight of distilled water and dispersed to obtain Dispersion A.

Furthermore, nickel plating solution (1) (pH 8.5) containing 0.14 mol/L of nickel sulfate, 0.46 mol/L of dimethylamine borane, and 0.2 mol/L of sodium citrate was prepared.

While stirring the above dispersion A containing 10 parts by weight of resin particles at 70°C, nickel plating solution (1) was added dropwise at a rate of 30 mL/min for 10 minutes. Next, the solution was added dropwise at a rate of 10 mL/min for 40 minutes, and then at a rate of 4 mL/min for 80 minutes, thereby controlling the amount of boron incorporated into the plating film and performing electroless nickel-boron alloy plating. The resulting dispersion was then filtered to remove the particles, which were then washed with water and dried to obtain metal-coated particles in which a metal coating layer (nickel layer) was disposed on the surface of the resin particles.

(3) Preparation of Resin Material The following materials were mixed to obtain a mixture: 20 parts by weight of resin particles; 21 parts by weight of solder particles ("Sn-Bi solder alloy" manufactured by Senju Metal Industry Co., Ltd.); 25 parts by weight of bisphenol A phenoxy resin; 4 parts by weight of fluorene epoxy resin; 30 parts by weight of phenol novolac epoxy resin; SI-60L (manufactured by Sanshin Chemical Industry Co., Ltd.). The obtained mixture was degassed and stirred for 3 minutes to obtain a resin material A (conductive paste, solder paste) containing resin particles. Furthermore, a resin material B (conductive paste, solder paste) containing metal-coated particles was obtained in the same manner as resin material A, except that the resin particles were changed to metal-coated particles.

(4) Preparation of Connection Structure An LGA substrate and a semiconductor chip with a pad size of 0.5 mm x 0.5 mm were prepared. The obtained resin materials (conductive paste, solder paste) A and B were screen-printed on the LGA substrate to form a solder paste layer. Next, the semiconductor chip was stacked on the solder paste layer with the electrodes facing each other. After that, reflow was performed at 160°C to harden the solder paste layer, obtaining connection structures A and B. Note that no pressure was applied during reflow.

(Examples 2 to 12, 14 and Comparative Examples 2 to 4)
Resin particles, metal-coated particles, resin materials A and B, and connection structures A and B were produced in the same manner as in Example 1, except that the type and content (wt%) of the polymerizable component, the average particle size and CV value of the particle size of the resin particles, and the type and thickness of the metal coating layer were set as shown in Tables 1 to 4. The average particle size and CV value of the particle size of the resin particles were adjusted by classification.

Example 13
(1) Preparation of Resin Particles Resin particles were prepared in the same manner as in Example 1, except that the type and content (wt %) of the polymerizable component were changed as shown in Table 3.

(2) Preparation of Metal-Coated Particles Formation of First Metal-Coated Layer:
Particles A were obtained in which a first metal coating layer (nickel layer, thickness 100 nm) was disposed on the surface of a resin particle.

Formation of the second metallization layer:
Ten parts by weight of the resulting particles A were dispersed in 500 parts by weight of ion-exchanged water using an ultrasonicator to obtain suspension B. A tin plating solution (1) containing 15 g/L of tin sulfate, 70 g/L of ethylenediaminetetraacetic acid, 30 g/L of sodium gluconate, and 1.5 g/L of phosphinic acid (adjusted to pH 8.5 with sodium hydroxide) was prepared. Furthermore, a reducing solution A containing 5 g/L of sodium borohydride (adjusted to pH 10.0 with sodium hydroxide) was prepared.

The tin plating solution (1) was gradually added to the resulting suspension B while stirring at 55°C, and then electroless tin plating was performed by reducing it with reducing solution A to form a second metal coating layer. Metal-coated particles were obtained in which a second metal coating layer (tin layer, 100 nm thick) was disposed on the surface of the first metal coating layer. Resin materials A and B and connection structures A and B were produced in the same manner as in Example 1, except that the resulting metal-coated particles were used.

(Comparative Example 1)
44.95 parts by weight of pentaerythritol tetraacrylate (50% by weight of 100% by weight of the polymerizable component) was added to 44.95 parts by weight of divinylbenzene (50% by weight of 100% by weight of the polymerizable component) and stirred to obtain a monomer liquid. Next, 10.1 parts by weight of a solvent (toluene) was added to the obtained monomer liquid and stirred until homogeneous, obtaining a monomer mixture. 200 parts by weight of a 1.0 wt% aqueous solution of polyvinyl alcohol with a molecular weight of approximately 2000 dissolved in pure water was placed in a reaction vessel. The obtained monomer mixture was added thereto and stirred until the monomer droplets reached the specified particle size. Next, the mixture was heated at 90°C for 9 hours to polymerize the monomer droplets, obtaining porous resin particles. Metal-coated particles, resin materials A and B, and connection structures A and B were prepared in the same manner as in Example 1, except that the obtained resin particles were used.

(evaluation)
(1) Viscosity of Polymerizable Component Mixture The viscosity of the polymerizable component mixture (before polymerization) was measured using an E-type viscometer ("VISCOMETER TV-22" manufactured by Toki Sangyo Co., Ltd.) at 25°C and 5 rpm.

(2) 20% K Values of Resin Particles at 25°C and 200°C The 20% K values of the obtained resin particles at 25°C and 200°C were measured using a microcompression tester ("ENT-5" manufactured by Elionix Co., Ltd.) by the method described above. The ratio (20% K value at 25°C/20% K value at 200°C) was also calculated.

(3) Amount of Outgassed Resin Particles When Heated at 250° C. for 10 Minutes The amount of outgassed resin particles when heated at 250° C. for 10 minutes was measured for the obtained resin particles by the method described above.

(4) Gap controllability (resin particles)
The connection structure A obtained using the resin particles was heated to 250°C in an oven and left at that temperature for 1 hour. The connection structure A was observed with a scanning electron microscope (SEM) to measure the minimum and maximum thicknesses of the connection portion (cured conductive paste layer). The gap controllability (resin particles) was evaluated according to the following criteria.

[Gap controllability (resin particles) evaluation criteria]
○○○: The maximum thickness is less than 1.1 times the minimum thickness. ○○: The maximum thickness is 1.1 times or more and less than 1.3 times the minimum thickness. ○: The maximum thickness is 1.3 times or more and less than 1.5 times the minimum thickness. ×: The maximum thickness is 1.5 times or more the minimum thickness.

(5) Gap controllability (metal-coated particles)
Connection structure B obtained using metal-coated particles was heated to 250°C in an oven and left at that temperature for 1 hour. The connection structure B was observed with a scanning electron microscope (SEM) to measure the minimum and maximum thicknesses of the connection (cured conductive paste layer). The gap controllability (metal-coated particles) was evaluated according to the following criteria.

[Gap controllability (metal-coated particles) evaluation criteria]
○○○: The maximum thickness is less than 1.1 times the minimum thickness. ○○: The maximum thickness is 1.1 times or more and less than 1.3 times the minimum thickness. ○: The maximum thickness is 1.3 times or more and less than 1.5 times the minimum thickness. ×: The maximum thickness is 1.5 times or more the minimum thickness.

(6) Conduction reliability after thermal cycling (resin particles)
A thermal cycling test was carried out on connection structure A obtained using resin particles, in which 1000 cycles were repeated, with one cycle consisting of heating from -20°C to 100°C and cooling to -20°C. For connection structure A after the thermal cycling, the connection resistance A per connection point between the upper and lower electrodes was measured using a four-terminal method. Note that, based on the relationship voltage = current × resistance, the connection resistance can be determined by measuring the voltage when a constant current is passed. The conductivity reliability (resin particles) after the thermal cycling was evaluated according to the following criteria.

[Criteria for Conduction Reliability (Resin Particles) after Thermal Cycles]
○○○: Connection resistance A is 5 mΩ or less. ○○: Connection resistance A is greater than 5 mΩ and less than 7 mΩ. ○: Connection resistance A is greater than 7 mΩ and less than 10 mΩ. ×: Connection resistance A exceeds 10 mΩ, or a connection failure has occurred.

(7) Conduction reliability after thermal cycling (metal-coated particles)
A thermal cycling test was carried out on connection structure B obtained using metal-coated particles, in which 1,000 cycles were repeated, with one cycle consisting of heating from -20°C to 100°C and cooling to -20°C. For connection structure B after the thermal cycling, the connection resistance B per connection point between the upper and lower electrodes was measured using a four-terminal method. Note that, based on the relationship voltage = current × resistance, the connection resistance can be determined by measuring the voltage when a constant current is passed. The conductivity reliability (metal-coated particles) after the thermal cycling was evaluated according to the following criteria.

[Criteria for Conduction Reliability (Metal-Coated Particles) after Thermal Cycles]
○○○: Connection resistance B is 5 mΩ or less ○○: Connection resistance B is more than 5 mΩ and less than 7 mΩ ○: Connection resistance B is more than 7 mΩ and less than 10 mΩ ×: Connection resistance B is more than 10 mΩ, or a connection failure has occurred

The composition and results of the resin particles and metal-coated particles are shown in Tables 1 to 4 below.

In addition, Table 5 below shows the results of Examples 6 (particle diameter 1 μm), 7 (particle diameter 5 μm), 8 (particle diameter 10 μm), 3 (particle diameter 30 μm), and 9 (particle diameter 50 μm), in which only the particle diameter of the resin particles was changed.

The results shown in Table 5 above show that when 1) a specific polymerizable component is used, and 2) the compressive modulus of the resin particles is within a specific range, and 3A) the particle diameter of the resin particles is 5 μm or more, the gap controllability of the connection structure when exposed to a high-temperature environment can be further improved compared to when the particle diameter of the resin particles is less than 5 μm. Furthermore, when 1) a specific polymerizable component is used, and 2) the compressive modulus of the resin particles is within a specific range, and 3B) the particle diameter of the resin particles is 20 μm or more, the gap controllability of the connection structure when exposed to a high-temperature environment can be further improved compared to when the particle diameter of the resin particles is less than 20 μm.

The gap controllability (resin particles) results for Example 7 (particle diameter 5 μm) and Example 8 (particle diameter 10 μm) were both marked "〇〇", but the maximum thickness/minimum thickness values in the gap controllability (resin particles) evaluation were smaller for Example 8 than for Example 7, meaning that Example 8 had better gap controllability (resin particles) than Example 7. The gap controllability (metal-coated particles) results for Example 7 (particle diameter 5 μm) and Example 8 (particle diameter 10 μm) were both marked "〇〇", but the maximum thickness/minimum thickness values in the gap controllability (metal-coated particles) evaluation were smaller for Example 8 than for Example 7, meaning that Example 8 had better gap controllability (metal-coated particles) than Example 7.

Furthermore, the results shown in Table 5 above show that when 1) a specific polymerizable component is used, and 2) the compressive modulus of the resin particles is within a specific range, and 3C) the particle diameter of the resin particles is 10 μm or greater, the conductivity reliability of the connection structure after thermal cycling can be significantly improved compared to when the particle diameter of the resin particles is less than 10 μm.

REFERENCE SIGNS LIST 1 resin particle 2 metal coating layer 3 solder portion 4 resin portion 11 metal coating particle 41, 51 connection structure 42 first connection target member 42a first electrode 43 second connection target member 43a second electrode 44 connection portion

Claims (15)

Resin particles containing a polymer of a polymerizable component,
the polymerizable component contains divinylbenzene and a (meth)acrylate compound having four or more (meth)acryloyl groups,
The resin particles have a compressive modulus of 1000 N/mm ² or more when compressed by 20% at 200°C. Resin particles according to claim 1, wherein the total content of the divinylbenzene and the (meth)acrylate compound having four or more (meth)acryloyl groups is 80% by weight or more, based on 100% by weight of the polymerizable component. Resin particles according to claim 1 or 2, wherein the weight ratio of the content of the divinylbenzene in the polymerizable component to the content of the (meth)acrylate compound having four or more (meth)acryloyl groups in the polymerizable component is 0.40 or more and 1.70 or less. Resin particles according to any one of claims 1 to 3, wherein the amount of outgassing when the resin particles are heated at 250°C for 10 minutes is 1000 ppm or less. Resin particles according to any one of claims 1 to 4, wherein the particle diameter of the resin particles is 1 μm or more and 100 μm or less. Resin particles according to any one of claims 1 to 5, wherein the resin particles are used to obtain metal-coated particles having a metal coating layer formed on the surface thereof, or the resin particles have a particle diameter of 5 μm or more and 100 μm or less. The resin particles described in claim 6 are used to obtain metal-coated particles having a metal coating layer formed on the surface of the resin particles, or the resin particles have a particle diameter of 20 μm or more and 100 μm or less. The resin particles described in any one of claims 1 to 5 are used to obtain metal-coated particles having a metal coating layer formed on the surface of the resin particles. The resin particles described in claim 5, wherein the particle diameter of the resin particles is 5 μm or more and 100 μm or less. Resin particles according to claim 9, wherein the particle diameter of the resin particles is 20 μm or more and 100 μm or less. Metal-coated particles comprising the resin particles described in any one of claims 1 to 10 and a metal coating layer disposed on the surface of the resin particles. The metal-coated particle described in claim 11, wherein the thickness of the metal coating layer is 0.2 μm or more. A resin material comprising the resin particles according to any one of claims 1 to 10 and a binder resin, or a resin material comprising the resin particles, metal-coated particles having a metal coating layer disposed on the surface of the resin particles, and a binder resin,
The resin material comprises the resin particles or the metal-coated particles dispersed in the binder resin. The resin material according to claim 13, wherein the resin material is a solder paste containing solder particles. The resin particles according to any one of claims 1 to 10, or the resin particles and metal-coated particles arranged on the surfaces of the resin particles,
Use in a solder paste containing solder particles and a binder resin.