Silver-coated resin particles and filler-containing paste

Abstract

Silver-coated resin particles (10) each comprise a resin particle (11) formed of a resin composition and a silver coating layer (12) formed on the surface of the resin particle (11), the silver-coated resin particles being characterized by containing titanium oxide in the range of 0.05 mass% to 12.00 mass% inclusive, and having an Sn content of 0.20 mass% or less. It is preferable that the 5% compressive elastic modulus (5% K value) is in the range of 0.2 GPa to 3.5 GPa inclusive. It is preferable that the resin composition is composed of one or more resins that are selected from among acrylic resins, styrene resins, phenolic resins, urethane resins, and polyimide resins.

Description

Silver-coated resin particles and filler-containing paste

[0001] This invention relates to silver-coated resin particles and a filler-containing paste. This application claims priority to Japanese Patent Application No. 2024-061053, filed on April 4, 2024, the contents of which are incorporated herein by reference.

[0002] For example, conductive adhesives such as conductive pastes and conductive films made by mixing silver-coated resin particles, which are resin particles coated with silver, with resin are known as conductive materials that can replace lead solder or lead-free solder. Conductive adhesives are used, for example, as materials for forming electrodes and electrical wiring that constitute electronic devices such as solar cell panels, liquid crystal displays, and touch panels. Furthermore, pastes and films made by mixing the above-mentioned silver-coated resin particles with resin are also used as TIM (Thermal Interface Material) materials because of their excellent thermal conductivity.

[0003] As the above-mentioned silver-coated resin particles, for example, Patent Document 1 discloses silver-coated resin particles in which resin particles are subjected to a pretreatment in which they are catalyzed with Sn (tin), and then the pretreated resin particles are subjected to electroless plating with silver, thereby improving adhesion between the resin particles and the silver coating layer.

[0004] Japanese Patent Application Publication No. 2015-199970 (A)

[0005] Recently, power electronics semiconductor elements for controlling large amounts of power, such as those used to control wind power generation, electric vehicles, and hybrid vehicles, generate a large amount of heat during operation and have a large area. Therefore, when bonding these elements, it is necessary to ensure high bonding reliability even under thermal cycle loads. Therefore, in filler-containing pastes containing the above-mentioned silver-coated resin particles as a filler, silver-coated resin particles that have particularly excellent adhesion between the resin particles and the silver-coating layer are required to improve the thermal cycle reliability of the bonding layer.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide silver-coated resin particles that have excellent adhesion between the resin particles and the silver coating layer and excellent heat cycle resistance, and a filler-containing paste that includes these silver-coated resin particles as a filler.

[0007] In order to solve the above problems, the present inventors conducted extensive research and found that if a large amount of Sn is used as a pretreatment (catalysis treatment) for plating, the silver coating layer is likely to peel off during thermal cycle loading, and therefore it is necessary to reduce the Sn content. Furthermore, they found that by disposing titanium oxide on the surfaces of resin particles, it is possible to effectively plate the surfaces of resin particles with silver.

[0008] The present invention has been made based on the above-mentioned findings, and the silver-coated resin particles of aspect 1 of the present invention are silver-coated resin particles comprising resin particles made of a resin composition and a silver coating layer formed on the surface of the resin particles, and are characterized in that they contain titanium oxide in a range of 0.05 mass% to 12.00 mass%, and the Sn content is 0.20 mass% or less.

[0009] According to the silver-coated resin particles of the first aspect of the present invention, the titanium oxide content is in the range of 0.05% by mass to 12.00% by mass, which allows for good silver plating on the surface of the resin particles and reduces the amount of Sn used in the catalysis treatment. Furthermore, the Sn content is limited to 0.20% by mass or less, which prevents the silver coating layer from peeling off during thermal cycling. Therefore, silver-coated resin particles with excellent adhesion between the resin particles and the silver coating layer and excellent thermal cycle resistance can be provided.

[0010] The silver-coated resin particles of Aspect 2 of the present invention are the silver-coated resin particles of Aspect 1 of the present invention, characterized in that the 5% compressive modulus (5% K value) is in the range of 0.2 GPa to 3.5 GPa. The silver-coated resin particles of Aspect 2 of the present invention have a 5% compressive modulus (5% K value) in the range of 0.2 GPa to 3.5 GPa, which maintains sufficient shape retention due to the addition of a filler and is sufficiently soft and easily deformable, thereby making it possible to suppress the occurrence of cracks in a cured paste containing the silver-coated resin particles as a filler, for example.

[0011] The silver-coated resin particles of Aspect 3 of the present invention are the silver-coated resin particles of Aspect 1 or Aspect 2 of the present invention, characterized in that the resin composition is one or more resins selected from acrylic resins, styrene resins, phenolic resins, urethane resins, and polyimide resins. According to the silver-coated resin particles of Aspect 3 of the present invention, the resin composition is one or more resins selected from acrylic resins, styrene resins, phenolic resins, urethane resins, and polyimide resins, so that the resin particles have excellent flexibility and are particularly suitable as fillers.

[0012] The silver-coated resin particles of Aspect 4 of the present invention are the silver-coated resin particles of any one of Aspects 1 to 3 of the present invention, characterized in that the particle diameter is in the range of 2 μm to 50 μm. Since the silver-coated resin particles of Aspect 4 of the present invention have a particle diameter in the range of 2 μm to 50 μm, the amount of expensive silver used can be reduced, thereby achieving cost reduction, and the particles can be used as a filler in pastes and the like for forming fine patterns.

[0013] A filler-containing paste according to Aspect 5 of the present invention is characterized by containing a binder resin and, as a filler, the silver-coated resin particles according to any one of Aspects 1 to 3 of the present invention. The filler-containing paste according to Aspect 5 of the present invention contains, as a filler, the silver-coated resin particles according to any one of Aspects 1 to 4 of the present invention, and therefore the thermal cycle reliability of a cured product of this filler-containing paste can be improved, and the paste can be stably used as a conductive adhesive or heat transfer material even in applications where it is subjected to severe thermal cycles.

[0014] According to the present invention, it is possible to provide silver-coated resin particles that have excellent adhesion between the resin particles and the silver coating layer and excellent heat cycle resistance, and a filler-containing paste that contains these silver-coated resin particles as a filler.

[0015] FIG. 1 is a cross-sectional view of a silver-coated resin particle according to one embodiment of the present invention. FIG. 2 is a flow diagram showing a method for producing a silver-coated resin particle according to one embodiment of the present invention. FIG. 3 is an explanatory diagram of a semiconductor device using a cured paste according to one embodiment of the present invention. FIG. 4 is a photograph showing the results of SEM observation of silver-coated resin particles of Inventive Example 1 in the Examples. FIG. 5 is a photograph showing the results of SEM observation of silver-coated resin particles of Inventive Example 1 in the Examples. FIG. 6 is a photograph showing the results of SEM observation of silver-coated resin particles of Inventive Example 6 in the Examples. FIG. 7 is a photograph showing the results of SEM observation of silver-coated resin particles of Comparative Example 2 in the Examples. FIG. 8 is a photograph showing the results of SEM observation of silver-coated resin particles of Comparative Example 2 in the Examples. FIG. 9 is a photograph showing the results of SEM observation of silver-coated resin particles of Comparative Example 4 in the Examples.

[0016] Silver-coated resin particles and filler-containing pastes according to embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the following embodiments are specifically described to provide a better understanding of the gist of the invention, and unless otherwise specified, do not limit the present invention.

[0017] FIG. 1 shows a silver-coated resin particle 10 according to one embodiment of the present invention. As shown in FIG. 1, the silver-coated resin particle 10 according to this embodiment includes a resin particle 11 made of a resin composition and a silver coating layer 12 formed on the surface of the resin particle 11. The silver-coated resin particle 10 contains titanium oxide in a range of 0.05% by mass to 12.00% by mass, and has an Sn content of 0.20% by mass or less. The silver-coated resin particle 10 may also contain silicon oxide. The silicon oxide content is preferably 3.00% by mass or less.

[0018] In this embodiment, the content of titanium oxide in the silver-coated resin particles 10 is determined by collecting a measurement sample from the silver-coated resin particles 10, performing elemental analysis, and calculating the titanium oxide (TiO ２ The Sn content in the silver-coated resin particles 10 is the amount of Sn measured by taking a measurement sample from the silver-coated resin particles 10 and performing elemental analysis.

[0019] In addition, in the silver-coated resin particles 10 of this embodiment, the 5% compressive modulus (5% K value) is preferably in the range of 0.2 GPa or more and 3.5 GPa or less. Furthermore, in the silver-coated resin particles 10 of this embodiment, the particle diameter is preferably in the range of 2 μm or more and 50 μm or less. In the silver-coated resin particles 10 of this embodiment, the resin composition constituting the resin particles 11 is preferably one or more selected from acrylic resin, styrene resin, phenolic resin, urethane resin, and polyimide resin. In the silver-coated resin particles 10 of this embodiment, the flexibility imparted thereto increases the interference effect against expansion and contraction, so it is more preferable to use urethane resin or acrylic resin, which are particularly excellent in flexibility.

[0020] The reasons for the above-described definition of the silver-coated resin particles 10 of this embodiment will be explained below.

[0021] (Titanium Oxide) In the silver-coated resin particles 10 of this embodiment, the inclusion of titanium oxide enables the surfaces of the resin particles 11 to be well plated with silver, improving the adhesion between the resin particles 11 and the silver coating layer 12. Furthermore, the inclusion of a portion of titanium oxide within the resin particles improves the strength of the particles, enabling them to withstand mechanical deformation and high shear during dispersion. Here, if the titanium oxide content in the silver-coated resin particles 10 is less than 0.05% by mass, the adhesion between the resin particles 11 and the silver coating layer 12 may not be sufficiently improved, and the hardness of the silver-coated resin particles may be insufficient. On the other hand, if the titanium oxide content exceeds 12.00% by mass, the flexibility of the silver-coated resin particles 10 may be reduced. For this reason, the titanium oxide content in the silver-coated resin particles 10 of this embodiment is set to a range of 0.05% by mass or more and 12.00% by mass or less.

[0022] In order to further improve the adhesion between the resin particles 11 and the silver coating layer 12, the titanium oxide content in the silver-coated resin particles 10 is preferably 1.50% by mass or more, and more preferably 3.00% by mass or more. In order to further ensure the flexibility of the silver-coated resin particles 10, the titanium oxide content in the silver-coated resin particles 10 is preferably 10.00% by mass or less, more preferably 7.50% by mass or less, and even more preferably 5.00% by mass or less.

[0023] (Sn Content) In the silver-coated resin particles 10 of this embodiment, when a catalysis treatment using Sn is performed as a pretreatment for plating the surfaces of the resin particles 11, Sn will be contained in the silver-coated resin particles 10. Here, if the Sn content exceeds 0.20 mass%, the silver-coating layer 12 may be prone to peeling during thermal cycle loading. For this reason, the Sn content in the silver-coated resin particles 10 of this embodiment is limited to 0.20 mass% or less.

[0024] In order to more reliably prevent the silver coating layer 12 from peeling off during thermal cycling, the Sn content in the silver-coated resin particles 10 is preferably 0.20% by mass or less, and more preferably 0.10% by mass or less. There are no particular restrictions on the Sn content in the silver-coated resin particles 10, but in order to reliably improve adhesion, the Sn content is preferably 0.00% by mass or more, and more preferably 0.05% by mass or more.

[0025] (5% Compressive Elastic Modulus (5% K Value)) In the silver-coated resin particles 10 of this embodiment, when the 5% compressive elastic modulus (5% K value) is 3.5 GPa or less, the flexibility of the silver-coated resin particles 10 is sufficiently ensured, and therefore, the occurrence of cracks in a cured paste containing these silver-coated resin particles 10 as a filler can be suppressed. On the other hand, when the 5% compressive elastic modulus (5% K value) is 0.2 GPa or more, the elasticity of the silver-coated resin particles 10 is ensured, and the shape retention of the paste and the coating strength can be maintained.

[0026] To further ensure flexibility, the upper limit of the 5% compressive elastic modulus (5% K value) of the silver-coated resin particles 10 is preferably 1.5 GPa or less, and even more preferably 0.5 GPa or less. To reliably maintain the shape retention and coating strength of the paste, the lower limit of the 5% compressive elastic modulus (5% K value) of the silver-coated resin particles 10 is preferably 0.3 GPa or more.

[0027] (Particle diameter) In the silver-coated resin particles 10 of this embodiment, when the particle diameter is 2 μm or more, the specific surface area does not become larger than necessary, and the amount of silver used to constitute the silver-coating layer 12 can be reduced, making it possible to keep production costs low. On the other hand, in the silver-coated resin particles 10 of this embodiment, when the particle diameter is 50 μm or less, a paste containing these silver-coated resin particles 10 as a filler can be applied in a fine pattern, making it possible to apply the silver-coated resin particles 10 to highly integrated or highly precise semiconductor devices, etc.

[0028] In order to further reduce the amount of silver used in the silver coating layer 12, the particle diameter of the silver-coated resin particles 10 is preferably 4 μm or more, and more preferably 6 μm or more. In order to accommodate even finer patterns, the particle diameter of the silver-coated resin particles 10 is preferably 15 μm or less, and even more preferably 10 μm or less.

[0029] (Resin composition) In this embodiment, when the resin composition constituting the resin particles 11 is one or more selected from acrylic resin, styrene resin, phenolic resin, urethane resin, and polyimide resin, the resin particles 11 have excellent flexibility and can stably form the silver coating layer 12.

[0030] Next, an example of a method for producing the silver-coated resin particles 10 according to this embodiment will be described with reference to the flow chart of FIG.

[0031] (Titanium oxide disposing step S01) First, titanium oxide is disposed on the surface of the resin particles 11. Methods for disposing titanium oxide include a method of forming a titanate film on the surface of the resin particles 11 (manufacturing method 1) and a method of physically attaching titanium oxide particles to the surface of the resin particles 11 (manufacturing method 2). A small amount of silicon oxide may also be disposed together with titanium oxide.

[0032] In Manufacturing Method 1, for example, resin particles 11 are dispersed in a mixed solvent of water and ethanol, and a predetermined amount of isopropoxy titanium is added, along with a trace amount of water or the like as a catalyst, to form a titanate film on the surface of the resin particles 11. In Manufacturing Method 2, for example, resin particles 11 and titanium oxide particles are mixed in predetermined amounts and then milled in a planetary ball mill or the like to adhere the titanium oxide particles to the surface of the resin particles 11. Titanium oxide particles ranging in size from a few nanometers to a few micrometers can be used, and spherical, needle-like, or bead-like shapes can be used. To improve adhesion and uniformity to resin particles, titanium oxide particles surface-coated with inorganic compounds, organic compounds, resins, etc. can also be used. Furthermore, the titanium oxide can be added as particles or an inorganic / organic titanium compound during the core resin particle synthesis process (monomer polymerization process) and incorporated into the resin particles, not just on the surface. Incorporation into the resin particles improves the deformability of the silver-coated resin particles and prevents peeling of the silver film.

[0033] (Catalyzing Treatment Step S02) Next, tin (divalent tin ions) serving as a catalyst are adsorbed onto the resin particles 11 having titanium oxide disposed on their surfaces. The resin particles 11 are added to an aqueous solution of a tin compound and stirred. Here, examples of the tin compound that can be used include stannous chloride, stannous fluoride, stannous bromide, and stannous iodide.

[0034] (Silver Coating Step S03) Next, silver is electrolessly plated on the surfaces of the resin particles 11 to form a silver coating layer 12. Methods for forming the silver coating layer 12 by electroless plating include: (1) a method in which the resin particles 11 are introduced into an aqueous solution containing a complexing agent, a reducing agent, etc. to prepare a slurry, and a silver salt aqueous solution is added dropwise to the slurry; (2) a method in which the resin particles 11 are introduced into an aqueous silver salt solution containing a complexing agent to prepare a slurry, and a reducing agent aqueous solution is added dropwise to the slurry; and (3) a method in which the resin particles 11 are introduced into an aqueous silver salt solution containing a complexing agent and a reducing agent to prepare a slurry, and a caustic alkali aqueous solution is added dropwise to the slurry.

[0035] Examples of silver salts that can be used include silver nitrate and silver dissolved in nitric acid. Examples of complexing agents that can be used include ammonia, ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetate, nitrotriacetic acid, triethylenetetraamminehexaacetic acid, sodium thiosulfate, succinate, succinimide, citrate, and iodide salts. Examples of reducing agents that can be used include formalin, glucose, imidazole, Rochelle salt (potassium sodium tartrate), hydrazine and its derivatives, hydroquinone, L-ascorbic acid, and formic acid. Examples of reducing agents that can be used include formaldehyde, a mixture of two or more reducing agents containing at least formaldehyde is more preferred, and a mixture of reducing agents containing formaldehyde and glucose is most preferred.

[0036] If divalent tin ions are adsorbed on the surface of the resin particles 11 by the catalysis treatment step S02, the divalent tin ions dissolve as tetravalent ions, releasing divalent electrons. Then, silver ions receive the divalent electrons and precipitate as metallic silver. This results in efficient formation of the silver coating layer 12. However, if the Sn content increases as a result of the catalysis treatment step S02, there is a risk of peeling between the resin particles 11 and the silver coating layer 12 during thermal cycling. Therefore, it is necessary to consider the Sn content when implementing the catalysis treatment step S02. In this embodiment, titanium oxide is disposed on the surface of the resin particles 11, so that silver can be effectively plated on the surface of the resin particles 11 even if the Sn content is reduced by the catalysis treatment step S02. While the reason why the formation of titanium oxide on the surface improves the adhesion of silver is unclear, it is thought that this is due to its excellent affinity with the silver precipitate particles and its improved Sn adsorption effect.

[0037] Through the steps described above, the silver-coated resin particles 10 of this embodiment are produced.

[0038] The filler-containing paste of this embodiment contains a binder resin and the above-described silver-coated resin particles 10 as a filler. The binder resin is not particularly limited, and examples thereof include thermoplastic resins and compositions that cure under heat or light, such as curable resin compositions. Examples of thermoplastic resins include styrene-butadiene block copolymers, acrylic resins, ethylene-vinyl acetate resins, and phenoxy resins. Examples of thermosetting resin compositions include resin compositions containing silicone resins, epoxy resins, or mixtures thereof as the main component. To achieve compatibility in adhesion, hardness, electrical properties, electrothermal properties, and the like, a resin that is compatible with the silver-coated resin particles is suitable. To improve affinity (compatibility) with the binder resin, the surfaces of the silver-coated resin particles can also be subjected to a surface treatment, such as with an organic acid. Examples of surface treatments include fatty acids such as stearic acid, isostearic acid, palmitic acid, and oleic acid, dicarboxylic acids such as maleic acid and succinic acid, carboxylic acid polymers such as polyacrylic acid, amine compounds such as dodecylamine and octadecylamine, amine polymers such as polyetheramine, sulfide compounds such as octadecyl disulfide, thiol compounds such as dodecanethiol, and silane coupling agents. Solvents and additives may be added as needed. Furthermore, to achieve higher electrical conductivity and thermal conductivity, conductive fillers other than the silver-coated resin particles 10 (hereinafter referred to as "other conductive fillers") may be added. Examples of other conductive fillers include metal particles such as silver powder, copper powder, and nickel powder, organic particles such as carbon, and conductive ceramic particles. However, silver powder, which has excellent electrical conductivity and thermal conductivity, is preferred. Furthermore, the particle shape is not limited to spherical, but flake (flat) particles are preferred. The ratio of the silver-coated resin particles 10 to the other conductive filler may be set to 5 to 95% by mass: 95 to 5% by mass depending on the desired electrical conductivity and thermal conductivity. The filler-containing paste of this embodiment is produced by weighing out predetermined amounts of a binder resin (e.g., an epoxy resin) and the silver-coated resin particles 10, and kneading them using a planetary mixer, a three-roll mill, or the like.

[0039] 3, the filler-containing paste of this embodiment forms a bonding layer 4 that bonds a circuit layer 2 of an insulating circuit board to a semiconductor element 3 in a semiconductor device 1. That is, by applying the filler-containing paste of this embodiment to the mounting surface of the circuit layer 2, laminating the semiconductor element 3, and performing a heat treatment, a bonding layer 4 made of a cured product of the filler-containing paste of this embodiment is formed, and the circuit layer 2 and the semiconductor element 3 are bonded together.

[0040] Here, the filler-containing paste of this embodiment contains the above-mentioned silver-coated resin particles 10 as a filler, and therefore has excellent electrical conductivity and thermal conductivity, and can electrically connect the semiconductor element 3 and the circuit layer 2, and can efficiently dissipate heat generated in the semiconductor element 3 to the insulating circuit board side. Furthermore, since the bonding layer 4 has excellent thermal cycle reliability, it is possible to suppress peeling between the semiconductor element 3 and the circuit layer 2 even when a thermal cycle is applied.

[0041] The silver-coated resin particles 10 of this embodiment, configured as described above, contain titanium oxide in a range of 0.05% by mass to 12.00% by mass, which enables silver to be well plated on the surfaces of the resin particles 11 and reduces the amount of Sn used in the catalysis treatment step S02. Furthermore, because the Sn content is limited to 0.20% by mass or less, peeling of the silver-coating layer 12 during thermal cycling can be suppressed.

[0042] In this embodiment, when the 5% compressive modulus (5% K value) of the silver-coated resin particles 10 is within the range of 0.2 GPa or more and 3.5 GPa or less, the shape retention and mechanical strength of the silver-coated film are maintained, and the silver-coated film is sufficiently soft and easily deformed, so that, for example, cracks can be suppressed in the cured paste of a filler-containing paste that contains the silver-coated resin particles 10 as a filler.

[0043] In this embodiment, when the resin composition constituting the resin particles 11 is one or more selected from acrylic resin, styrene resin, phenolic resin, urethane resin, and polyimide resin, the resin particles 11 have excellent flexibility and are particularly suitable as a filler.

[0044] In this embodiment, when the particle diameter of the silver-coated resin particles 10 is within the range of 2 μm or more and 50 μm or less, the amount of expensive silver used can be reduced, thereby reducing costs, and the particles can be used as a filler in pastes, etc., for forming fine patterns.

[0045] The filler-containing paste of this embodiment contains the silver-coated resin particles 10 of this embodiment as a filler, and therefore has excellent heat cycle resistance, and can be used stably as a conductive adhesive or heat transfer material even in applications where severe heat cycles are applied.

[0046] Although one embodiment of the present invention has been described above, the present invention is not limited thereto and can be modified as appropriate within the scope of the technical concept of the invention. In this embodiment, the present invention has been described as being applied to a filler-containing paste used in forming a bonding layer that bonds a circuit layer and a semiconductor element of a semiconductor device, but the present invention is not limited thereto and may be used for other purposes.

[0047] A confirmation experiment conducted to confirm the effectiveness of the present invention will be described.

[0048] (Invention Examples 1-5, Comparative Examples 2 and 3) The resin particles shown in Table 1 were dispersed in an ethanol solvent to obtain a slurry with a solids concentration of 5% by mass. Titanium isopropoxide was added to this slurry so that the titanium oxide concentration was the value shown in Table 1, and a small amount of water was added dropwise to produce titania-coated urethane particles. After filtration and washing, the particles were dispersed in water, and stannous chloride was added so that the tin concentration was the value shown in Table 1. The mixture was stirred at 40°C for 1 hour and filtered again. The resulting cake was dispersed in water to obtain resin particles with divalent tin ions adsorbed on the surface (catalyzed resin particles). Thereafter, a silver coating layer was formed on the surface of the resin particles by electroless plating so that the Ag concentration was the value shown in Table 1.

[0049] (Invention Examples 6-8, Comparative Examples 4-6) Resin particles shown in Table 1 were mixed with titanium oxide particles having an average particle size of 200 nm so that the titanium oxide particle content was the numerical value shown in Table 1, and the mixture was subjected to a planetary ball mill to adhere the titanium oxide particles to the surfaces of the resin particles. The resin particles with the titanium oxide particles adhered to their surfaces were subjected to a catalyzation treatment and electroless plating in the same manner as in Invention Examples 1-5 and Comparative Examples 2 and 3, to form a silver coating layer.

[0050] Comparative Example 1: Urethane particles (resin particles) with an average particle size of 15 μm were dispersed in water, and stannous chloride was added so that the Sn concentration was 0.1% by mass. The mixture was stirred at 40° C. for 1 hour and filtered. The resulting cake was dispersed in water to obtain resin particles (catalyzed resin particles) with divalent tin ions adsorbed on their surfaces. A silver coating layer was formed on the surface of these resin particles by electroless plating so that the Ag concentration was 45% by mass.

[0051] The silver-coated resin particles of Examples 1-8 of the present invention and Comparative Examples 1-6 obtained as described above were evaluated as follows.

[0052] (5% Compressive Elastic Modulus (5% K Value) of Silver-Coated Resin Particles) First, using a microcompression tester (Fisher Instruments, model number: HM500), a compression test was performed on one silver-coated resin particle with a flat indenter at a load change rate of 0.3 mN / s and 20°C, and the displacement and load were measured when the silver-coated resin particle was compressed by 5% relative to its major axis. In this case, the starting point for displacement measurement (zero point) was not the point at which the microcompression tester recognized contact with the silver-coated resin particle, but the point at which the microcompression tester changed the load applied to the silver-coated resin particle. Next, the measured displacement and load were substituted into the following (1) to calculate the 5% compressive elastic modulus (5% K value). The evaluation results are shown in Table 1.

[0053] Equation (1): 5% compressive elastic modulus (5% K value) [GPa] = 3F / (2S ３ R) １ / ２ F: Load [N] when silver-coated resin particle is compressed by 5% S: Displacement [mm] when silver-coated resin particle is compressed by 5% R: Radius [mm] of silver-coated resin particle before compression

[0054] (Whether or not the silver coating layer peeled off after thermal cycling) After the obtained silver-coated resin particles of Inventive Example 1-8 and Comparative Example 1-6 were subjected to a thermal cycling test of -20°C and 80°C, their cross sections were observed with an SEM to check whether or not the silver coating layer peeled off. The evaluation results are shown in Table 1.

[0055] (Volume Resistivity of Coating Film) Using the above-described silver-coated resin particles, an epoxy resin-based filler-containing paste with a filler ratio of 60 vol% was prepared using a rotation-revolution mixer. This filler-containing paste was used to form a coating film with a thickness of 50 μm. The volume resistivity of this coating film was measured using the four-probe method (JIS-K-7194). The evaluation results are shown in Table 1.

[0056]

[0057] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Inventive Example 1 was measured and found to be 0.5 GPa. The silver-coated resin particles of Inventive Example 1 were subjected to a thermal cycle test of -20°C and then 80°C, and their cross sections were observed using an SEM. The observation results are shown in Figures 4A and 4B. Peeling of the silver coating layer was not observed even after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Inventive Example 1 as a filler was 2.0 x 10 －４ The value was Ω·cm.

[0058] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Inventive Example 2 was measured and found to be 1.9 GPa. The silver-coated resin particles of Inventive Example 2 were subjected to a thermal cycle test of -20°C and then 80°C, and their cross sections were observed under an SEM. Peeling of the silver coating layer was not observed even after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Inventive Example 2 as a filler was 1.0 × 10 －４ The value was Ω·cm.

[0059] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Inventive Example 3 was measured and found to be 2.0 GPa. The silver-coated resin particles of Inventive Example 3 were subjected to a thermal cycle test of -20°C and then 80°C, and their cross sections were observed under an SEM. Peeling of the silver coating layer was not observed even after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Inventive Example 3 as a filler was 9.0 × 10 －５ The value was Ω·cm.

[0060] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Inventive Example 4 was measured and found to be 0.4 GPa. The silver-coated resin particles of Inventive Example 4 were subjected to a thermal cycle test of -20°C and then 80°C, and their cross sections were observed under an SEM. Peeling of the silver coating layer was not observed even after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Inventive Example 4 as a filler was 1.0 × 10 －３ The value was Ω·cm.

[0061] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Inventive Example 5 was measured and found to be 2.5 GPa. The silver-coated resin particles of Inventive Example 5 were subjected to a thermal cycle test of -20°C and then 80°C, and their cross sections were observed under an SEM. Peeling of the silver coating layer was not observed even after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Inventive Example 5 as a filler was 5.0 × 10 －４ The value was Ω·cm.

[0062] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Inventive Example 6 was measured and found to be 0.3 GPa. The silver-coated resin particles of Inventive Example 6 were subjected to a thermal cycle test of -20°C and then 80°C, and their cross sections were observed using an SEM. The observation results are shown in Figure 5. Peeling of the silver coating layer was not observed even after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Inventive Example 6 as a filler was 2.0 x 10 －４ The value was Ω·cm.

[0063] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Inventive Example 7 was measured and found to be 2.5 GPa. The silver-coated resin particles of Inventive Example 7 were subjected to a thermal cycle test of -20°C and then 80°C, and their cross sections were observed under an SEM. Peeling of the silver coating layer was not observed even after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Inventive Example 7 as a filler was 3.0 × 10 －３ The value was Ω·cm.

[0064] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Inventive Example 8 was measured and found to be 0.7 GPa. The silver-coated resin particles of Inventive Example 8 were subjected to a thermal cycle test of -20°C and then 80°C, and their cross sections were observed under an SEM. Peeling of the silver coating layer was not observed even after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Inventive Example 8 as a filler was 1.0 × 10 －３ The value was Ω·cm.

[0065] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Inventive Example 8 was measured and found to be 0.7 GPa. The silver-coated resin particles of Inventive Example 8 were subjected to a thermal cycle test of -20°C and then 80°C, and their cross sections were observed under an SEM. Peeling of the silver coating layer was not observed even after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Inventive Example 8 as a filler was 1.0 × 10 －３ The value was Ω·cm.

[0066] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Comparative Example 1 was measured and found to be 0.5 GPa. The silver-coated resin particles of Comparative Example 1 were subjected to a thermal cycle test of -20°C and then 80°C, and the cross section was observed under an SEM. Peeling of the silver coating layer was confirmed after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Comparative Example 1 as a filler was 2.0 × 10 －３ The value was Ω·cm.

[0067] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Comparative Example 2 was measured and found to be 2.6 GPa. The silver-coated resin particles of Comparative Example 2 were subjected to a thermal cycle test of -20°C and then 80°C, and their cross sections were observed using an SEM. The observation results are shown in Figures 6A and 6B. Peeling of the silver coating layer was confirmed after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Comparative Example 2 as a filler was 1.0 x 10 －１ The value was Ω·cm.

[0068] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Comparative Example 3 was measured and found to be 3.9 GPa. The silver-coated resin particles of Comparative Example 3 were subjected to a thermal cycle test of -20°C and then 80°C, and the cross section was observed under an SEM. Peeling of the silver coating layer was confirmed after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Comparative Example 3 as a filler was 3.0 × 10 －２ The value was Ω·cm.

[0069] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Comparative Example 4 was measured and found to be 2.0 GPa. The silver-coated resin particles of Comparative Example 4 were subjected to a thermal cycle test of -20°C and then 80°C, and their cross sections were observed using an SEM. The observation results are shown in Figure 7. Peeling of the silver coating layer was confirmed after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Comparative Example 4 as a filler was 4.0 x 10 －３ The value was Ω·cm.

[0070] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Comparative Example 5 was measured and found to be 2.8 GPa. The silver-coated resin particles of Comparative Example 5 were subjected to a thermal cycle test of -20°C and then 80°C, and their cross sections were observed under an SEM. Peeling of the silver coating layer was confirmed after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Comparative Example 5 as a filler was 1.0 × 10 －１ The value was Ω·cm.

[0071] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Comparative Example 6 was measured and found to be 5.0 GPa. The silver-coated resin particles of Comparative Example 6 were subjected to a thermal cycle test of -20°C and 80°C, and then their cross sections were observed under an SEM. Peeling of the silver coating layer was confirmed after the thermal cycle test. The volume resistivity of a coating film formed using a filler-containing paste containing the silver-coated resin particles of Comparative Example 6 as a filler was 1.0 × 10 －２ The value was Ω·cm.

[0072] As described above, it has been confirmed that the present invention can provide silver-coated resin particles that have excellent adhesion between the resin particles and the silver coating layer and excellent heat cycle resistance, as well as a filler-containing paste that includes these silver-coated resin particles as a filler.

[0073] The silver-coated resin particles and filler-containing paste of the present invention can be used as anisotropic conductive film formers (ACF, ACP) used in liquid crystal displays, touch panels, etc., conductive pastes used in touch panels, etc., conductive pastes and films for die bonding, and TIM materials.

[0074] 10 Silver-coated resin particle 11 Resin particle 12 Silver-coated layer

Claims

1. Silver-coated resin particles comprising resin particles made of a resin composition and a silver coating layer formed on the surface of the resin particles, characterized in that the silver-coated resin particles contain titanium oxide in the range of 0.05% by mass to 12.00% by mass, and the Sn content is 0.20% by mass or less.

2. Silver-coated resin particles according to claim 1, characterized in that the 5% compressive modulus (5% K value) is in the range of 0.2 GPa or more and 3.5 GPa or less.

3. The silver-coated resin particles according to claim 1, wherein the resin composition is one or more resins selected from the group consisting of acrylic resin, styrene resin, phenolic resin, urethane resin, and polyimide resin.

4. Silver-coated resin particles according to claim 1, characterized in that the particle diameter is in the range of 2 μm to 50 μm.

5. A filler-containing paste comprising a binder resin and the silver-coated resin particles according to any one of claims 1 to 4 as a filler.

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