Silver-coated resin particles and filler-containing paste

Abstract

To provide a silver-coated resin particle having excellent adhesion between a resin particle and a silver coating layer and excellent heat cycle resistance, and a filler-containing paste including the silver-coated resin particles as a filler.SOLUTION: A silver-coated resin particle 10 comprises 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 particle containing 0.05 mass% or more and 12.0 mass% or less of titanium oxide, and having a Sn content of 0.2 mass% or less. The 5% compressive elastic modulus (5% K value) is preferably in the range of 0.2 GPa to 3.5 GPa. The resin composition is preferably composed of one or more resins selected from acrylic resins, styrene resins, phenolic resins, urethane resins, and polyimide resins.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to silver-coated resin particles and a paste containing a filler. [Background technology]

[0002] For example, conductive adhesives such as conductive pastes and conductive films, which are made by mixing silver-coated resin particles, in which resin particles are 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, films, etc. made by mixing the above-mentioned silver-coated resin particles with resin have excellent thermal conductivity, and are therefore also used as TIM (Thermal Interface Material) materials.

[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 to be catalyzed with Sn, 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-199970 Summary of the Invention [Problem to be solved by the invention]

[0005] Recently, power electronics semiconductor elements for controlling large amounts of electric power, which are used to control wind power generation, electric vehicles, hybrid vehicles, etc., 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 when subjected to thermal cycle loads. Therefore, in a filler-containing paste 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-coated layer are required in order 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. [Means for solving the problem]

[0007] In order to solve the above problems, the 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, so the Sn content needs to be reduced.Furthermore, they found that by disposing titanium oxide on the surface of resin particles, it is possible to effectively plate the surface 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 the range of 0.05 mass% to 12.0 mass% and have an Sn content of 0.2 mass% or less.

[0009] The silver-coated resin particles of the first aspect of the present invention contain titanium oxide in the range of 0.05% by mass to 12.0% 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 0.2% by mass or less, which prevents the silver coating layer from peeling off during thermal cycling. Therefore, 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.

[0010] The silver-coated resin particles of embodiment 2 of the present invention are the silver-coated resin particles of embodiment 1 of the present invention, 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. 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, and therefore maintain sufficient shape retention due to the addition of filler, while also being sufficiently soft and easily deformable. Therefore, for example, the occurrence of cracks in a cured paste containing these silver-coated resin particles as a filler can be suppressed.

[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 resin, styrene resin, phenolic resin, urethane resin, and polyimide resin, and therefore the resin particles have excellent flexibility and are particularly suitable as a filler.

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

[0013] The filler-containing paste of the fifth aspect of the present invention is characterized by containing a binder resin and the silver-coated resin particles of any one of the first to third aspects of the present invention as a filler. According to the filler-containing paste of aspect 5 of the present invention, the filler contains silver-coated resin particles of any one of aspects 1 to 4 of the present invention, thereby improving the thermal cycle reliability of the cured product of this filler-containing paste, and the paste can be used stably as a conductive adhesive or heat transfer material even in applications where it is subjected to severe thermal cycles. [Effects of the Invention]

[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 includes these silver-coated resin particles as a filler. [Brief explanation of the drawings]

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

[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] Figure 1 shows a silver-coated resin particle 10 according to one embodiment of the present invention. The silver-coated resin particle 10 according to this embodiment includes, for example, a resin particle 11 made of a resin composition and a silver coating layer 12 formed on the surface of the resin particle 11, as shown in Figure 1. The silver-coated resin particles 10 contain titanium oxide in the range of 0.05% by mass to 12.0% by mass, and the Sn content is 0.2% by mass or less. The silver-coated resin particles 10 may contain silicon oxide, and the content of silicon oxide is preferably 3% by mass or less.

[0018] In this embodiment, the content of titanium oxide in the silver-coated resin particles 10 is calculated by taking a measurement sample from the silver-coated resin particles 10, performing elemental analysis, and converting the measured Ti content into titanium oxide (TiO2). The Sn content in the silver-coated resin particles 10 is determined by taking a measurement sample from the silver-coated resin particles 10 and performing elemental analysis on the sample.

[0019] In addition, the silver-coated resin particles 10 of this embodiment preferably have a 5% compressive elastic modulus (5% K value) in the range of 0.2 GPa or more and 3.5 GPa or less. Furthermore, the silver-coated resin particles 10 of this embodiment preferably have a particle diameter in the range of 2 μm to 50 μm. In addition, in the silver-coated resin particles 10 of this embodiment, it is preferable that the resin composition constituting the resin particles 11 is one or more types 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-mentioned 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 makes it possible to satisfactorily plate the surfaces of the resin particles 11 with silver, thereby 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, making them able to withstand mechanical deformation and high shear during dispersion. 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 12.0% by mass, the flexibility of the silver-coated resin particles 10 may be reduced. For this reason, in the silver-coated resin particles 10 of this embodiment, the content of titanium oxide is set within the range of 0.05% by mass to 12.0% by mass.

[0022] In order to further improve the adhesion between the resin particles 11 and the silver coating layer 12, the content of titanium oxide in the silver-coated resin particles 10 is preferably 1.5% by mass or more, and more preferably 3.0% by mass or more. Furthermore, 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 10.0 mass% or less, more preferably 7.5 mass% or less, and even more preferably 5.0 mass% or less.

[0023] (Sn content) In the silver-coated resin particles 10 of this embodiment, when a catalytic treatment using Sn is performed as a pretreatment for plating the surfaces of the resin particles 11, Sn is contained in the silver-coated resin particles 10. Here, if the Sn content exceeds 0.2 mass %, the silver-coating layer 12 may be prone to peeling when subjected to thermal cycle loading. For this reason, in the silver-coated resin particles 10 of this embodiment, the Sn content is limited to 0.2 mass % or less.

[0024] In order to more reliably prevent the silver coating layer 12 from peeling off when subjected to thermal cycle loading, the Sn content in the silver-coated resin particles 10 is preferably 0.2 mass% or less, and more preferably 0.1 mass% or less. Furthermore, there is no particular restriction on the Sn content in the silver-coated resin particles 10, but in order to reliably improve adhesion, the Sn content is preferably 0 mass% or more, and more preferably 0.05 mass% or more.

[0025] (5% compression modulus (5% K value)) In the silver-coated resin particles 10 of this embodiment, when the 5% compressive 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 the cured paste of a 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 strength of the coating film 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 more preferably 1.5 GPa or less, and even more preferably 0.5 GPa or less. In order to reliably maintain the shape retention of the paste and the strength of the coating film, it is more preferable that the lower limit of the 5% compressive elastic modulus (5% K value) of the silver-coated resin particles 10 is 0.3 GPa or more.

[0027] (particle size) 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 in the silver-coating layer 12 can be reduced, thereby 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 the 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 to form the silver coating layer 12, the particle size of the silver-coated resin particles 10 is more preferably 4 μm or more, and even more preferably 6 μm or more. Furthermore, in order to accommodate even finer patterns, the particle size of the silver-coated resin particles 10 is more 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 resin particles 11. Examples of methods for disposing titanium oxide include a method of forming a titanate film on the surface of resin particles 11 (manufacturing method 1) and a method of physically attaching titanium oxide particles to the surface of 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 isopropoxytitanium is added, along with a small 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, a predetermined amount of resin particles 11 and titanium oxide particles are mixed and then processed in a planetary ball mill or the like, thereby adhering the titanium oxide particles to the surfaces of the resin particles 11. Titanium oxide particles ranging in size from a few nanometers to a few micrometers can be used, and they can be spherical, needle-like, or bead-like in shape. In order to improve adhesion and uniformity to the resin particles, it is also possible to use titanium oxide particles whose surfaces are coated with inorganic compounds, organic compounds, resins, or the like. Furthermore, the titanium oxide can be added as particles or inorganic / organic titanium compounds during the core resin particle synthesis process (monomer polymerization process) and can be incorporated into the resin particles, not just onto the surface. By incorporating titanium oxide into the resin particles, the deformation resistance of the silver-coated resin particles can be improved, and peeling of the silver film can be prevented.

[0033] (Catalyzation treatment step S02) Next, tin (divalent tin ions) serving as a catalyst is adsorbed onto the resin particles 11 having titanium oxide disposed on the surface thereof. The resin particles 11 are added to an aqueous solution of a tin compound and stirred. Examples of the tin compound that can be used here include stannous chloride, stannous fluoride, stannous bromide, and stannous iodide.

[0034] (Silver coating process S03) Next, the surfaces of the resin particles 11 are electrolessly plated with silver to form silver coating layers 12 . Methods for forming the silver coating layer 12 by electroless plating include: (1) a method in which resin particles 11 are introduced into an aqueous solution containing a complexing agent, a reducing agent, etc. to prepare a slurry, and then a silver salt aqueous solution is added dropwise to the slurry; (2) a method in which resin particles 11 are introduced into an aqueous silver salt solution containing a complexing agent to prepare a slurry, and then a reducing agent aqueous solution is added dropwise to the slurry; and (3) a method in which resin particles 11 are introduced into an aqueous silver salt solution containing a complexing agent and a reducing agent to prepare a slurry, and then 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, triethylenetetraaminehexaacetic 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 allows the silver coating layer 12 to be efficiently formed. However, if the Sn content increases as a result of the catalyzation treatment step S02, there is a risk that the resin particles 11 and the silver coating layer 12 may peel off when subjected to a thermal cycle load. Therefore, it is necessary to consider the implementation status of the catalyzation treatment step S02 in consideration of the Sn content. In this embodiment, since titanium oxide is disposed on the surfaces of the resin particles 11, it is possible to satisfactorily plate silver on the surfaces of the resin particles 11 even if the Sn content is reduced in the catalyzation treatment step S02. The reason why the formation of titanium oxide on the surface improves the adhesion of silver is not clear, but it is thought that this is due to its excellent affinity with silver precipitate particles and the 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 silver-coated resin particles 10 described above as a filler. The binder resin is not particularly limited, and examples thereof include thermoplastic resins and compositions that harden 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. Resins that are compatible with the silver-coated resin particles are suitable for compatibility in terms of adhesion, hardness, electrical properties, electrothermal properties, and the like. To improve affinity (compatibility) with the binder resin, the surfaces of the silver-coated resin particles can be treated with an organic acid, etc. 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. If necessary, the composition may contain a solvent or an additive. Furthermore, to obtain higher electrical 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, with silver powder being preferred due to its excellent electrical and thermal conductivity. Furthermore, it is more preferable to use not only spherical particles but also flake (flat) particles. The ratio of the silver-coated resin particles 10 to other conductive fillers can be set to 5 to 95 wt %:95 to 5 wt %, depending on the desired electrical and thermal conductivity. The filler-containing paste of this embodiment is produced by weighing out predetermined amounts of a binder resin (for example, an epoxy resin) and the silver-coated resin particles 10 described above, and kneading them using a planetary mixer, a three-roll mixer, 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 subjected to thermal cycles.

[0041] The silver-coated resin particles 10 of this embodiment, configured as described above, contain titanium oxide in a range of 0.05 mass % or more and 12.0 mass % or less, making it possible to effectively plate silver on the surface of the resin particles 11 and reducing the amount of Sn used in the catalysis treatment step S02. Furthermore, since the Sn content is limited to 0.2 mass % or less, peeling of the silver coating layer 12 during thermal cycle loading 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 hardened 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 to this and can be modified as appropriate within the scope of the technical idea of ​​the invention. In this embodiment, the present invention has been described as being applied to a filler-containing paste used when forming a bonding layer that bonds a circuit layer and a semiconductor element of a semiconductor device, but the present invention is not limited to this and may be used for other purposes. [Example]

[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 solid content of 5 mass %. Titanium isopropoxide was added to this slurry so that the titanium oxide concentration reached the value shown in Table 1, and a very small amount of water was added dropwise to produce titania-coated urethane particles. After filtering and washing, the product was dispersed in water, and stannous chloride was added so that the tin concentration reached 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 their surfaces (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) The resin particles shown in Table 1 and titanium oxide particles with an average particle size of 200 nm were mixed so that the titanium oxide particle content was the value shown in Table 1, and the mixture was put through a planetary ball mill to adhere the titanium oxide particles to the surface of the resin particles. The resin particles having titanium oxide particles attached to the surface thereof were subjected to a catalytic 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, followed by stirring at 40°C for 1 hour and filtration. The resulting cake was dispersed in water to obtain resin particles with divalent tin ions adsorbed on their surfaces (catalyzed resin particles). A silver coating layer was formed on the surface of the resin particles by electroless plating so that the Ag concentration was 45 mass %.

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

[0052] (5% compression modulus of silver-coated resin particles (5% K value)) First, a compression test was performed on one silver-coated resin particle using a flat indenter (Fisher Instruments, model number: HM500) at a load change rate of 0.3 mN / s and 20°C. The displacement and load were measured when the silver-coated resin particle was compressed 5% relative to its major axis. The starting point (zero point) for displacement measurement 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. The measured displacement and load were then substituted into the following equation (1) to calculate the 5% compression modulus (5% K value). The evaluation results are shown in Table 1.

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

[0054] (Whether or not the silver coating layer peels off after thermal cycling) Furthermore, the obtained silver-coated resin particles of Inventive Example 1-8 and Comparative Example 1-6 were subjected to a heat cycle test of -20°C and 80°C, and then the cross section was observed with an SEM to check for peeling of the silver coating layer. The evaluation results are shown in Table 1.

[0055] (volume resistivity of coating film) Using the silver-coated resin particles described above, an epoxy resin-based filler-containing paste with a filler content of 60 vol% was prepared using a planetary mixer. A coating film with a thickness of 50 μm was formed using this filler-containing paste. The volume resistivity of this coating film was measured using the four-point probe method. The evaluation results are shown in Table 1.

[0056] [Table 1]

[0057] The 5% compressive elastic 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 Example 1 were subjected to a thermal cycle test between -20°C and 80°C, and then their cross sections were observed using an SEM. The observation results are shown in Figure 4. No peeling of the silver coating layer was observed even after the thermal cycle test. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Example 1 of the present invention as a filler was 2.0 × 10 -4 The resistance was Ω·cm.

[0058] The 5% compressive elastic 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 the cross section was observed with an SEM. Even after the thermal cycle test, no peeling of the silver coating layer was observed. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Example 2 of the present invention as a filler was 1.0 × 10 -4 The resistance was Ω·cm.

[0059] The 5% compressive elastic 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 the cross section was observed with an SEM. Even after the thermal cycle test, no peeling of the silver coating layer was observed. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Example 3 of the present invention as a filler was 9.0 × 10 -5 The resistance was Ω·cm.

[0060] The 5% compressive elastic 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 the cross section was observed with an SEM. Even after the thermal cycle test, no peeling of the silver coating layer was observed. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Example 4 of the present invention as a filler was 1.0 × 10 -3 The resistance was Ω·cm.

[0061] The 5% compressive elastic 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 the cross section was observed with an SEM. Even after the thermal cycle test, no peeling of the silver coating layer was observed. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Example 5 of the present invention as a filler was 5.0 × 10 -4 The resistance was Ω·cm.

[0062] The 5% compressive elastic 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 Example 6 were subjected to a thermal cycle test between -20°C and 80°C, and then their cross sections were observed using an SEM. The observation results are shown in Figure 5. No peeling of the silver coating layer was observed even after the thermal cycle test. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Example 6 of the present invention as a filler was 2.0 × 10 -4 The resistance was Ω·cm.

[0063] The 5% compressive elastic 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 the cross section was observed with an SEM. Even after the thermal cycle test, no peeling of the silver coating layer was observed. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Example 7 of the present invention as a filler was 3.0 × 10 -3 The resistance was Ω·cm.

[0064] The 5% compressive elastic 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 <-> 80°C, and then their cross sections were observed with an SEM. Even after the thermal cycle test, no peeling of the silver coating layer was observed. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Example 8 of the present invention as a filler was 1.0 × 10 -3 The resistance was Ω·cm.

[0065] The 5% compressive elastic 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 <-> 80°C, and then their cross sections were observed with an SEM. Even after the thermal cycle test, no peeling of the silver coating layer was observed. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Example 8 of the present invention as a filler was 1.0 × 10 -3 The resistance was Ω·cm.

[0066] The 5% compressive elastic 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 with an SEM. Peeling of the silver coating layer was confirmed after the thermal cycle test. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Comparative Example 1 as a filler was 2.0 × 10 -3 The resistance was Ω·cm.

[0067] The 5% compressive elastic 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 the cross section was observed using an SEM. The observation results are shown in Figure 6. Peeling of the silver coating layer was confirmed after the thermal cycle test. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Comparative Example 2 as a filler was 1.0 × 10 -1 The resistance was Ω·cm.

[0068] The 5% compressive elastic 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 with an SEM. Peeling of the silver coating layer was confirmed after the thermal cycle test. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Comparative Example 3 as a filler was 3.0 × 10 -2 The resistance was Ω·cm.

[0069] The 5% compressive elastic 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 between -20°C and 80°C, and then 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 the coating film formed using the filler-containing paste containing the silver-coated resin particles of Comparative Example 4 as a filler was 4.0 × 10-3 The resistance was Ω·cm.

[0070] The 5% compressive elastic 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 the cross section was observed with an SEM. Peeling of the silver coating layer was confirmed after the thermal cycle test. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Comparative Example 5 as a filler was 1.0 × 10 -1 The resistance was Ω·cm.

[0071] The 5% compressive elastic 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 then 80°C, and the cross section was observed with an SEM. Peeling of the silver coating layer was confirmed after the thermal cycle test. The volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particles of Comparative Example 6 as a filler was 1.0 × 10 -2 The resistance 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. [Industrial Applicability]

[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. [Explanation of symbols]

[0074] 10. Silver-coated resin particles 11 Resin particles 12 Silver coating

Claims

1. A silver-coated resin particle comprising a resin particle made of a resin composition and a silver coating layer formed on the surface of the resin particle, Silver-coated resin particles, characterized by containing titanium oxide in the range of 0.05 mass % to 12.0 mass % and having an Sn content of 0.2 mass % or less.

2. 2. The silver-coated resin particles according to claim 1, wherein the 5% compressive modulus (5% K value) is in the range of 0.2 GPa to 3.5 GPa.

3. 2. 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. 2. The silver-coated resin particles according to claim 1, wherein 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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