Copper-coated resin particle and filler-containing paste

Abstract

Provided are: a copper-coated resin particle (10) comprising a resin particle (11) composed of a resin composition and a copper coating layer (12) formed on the surface of the resin particle (11), the copper-coated resin particle (10) being characterized by containing 0.05-5.0 mass% of silicon oxide and also containing Sn and Pd; and a filler-containing paste containing the copper-coated resin particle as a filler. It is preferable that the 5% compressive elastic modulus (5% K value) falls within the range of 0.2 GPa to 3.5 GPa. It is preferable that the resin composition is one or more resins selected from among acrylic resins, styrene resins, phenolic resins, urethane resins, and polyimide resins.

Description

Copper-coated resin particles and filler-containing paste 【0001】 This invention relates to copper-coated resin particles and filler-containing paste. This application claims priority under Japanese Patent Application No. 2024-211622, filed in Japan on December 4, 2024, the contents of which are incorporated herein by reference. 【0002】 For example, conductive adhesives such as conductive pastes and conductive films are known as conductive materials that replace lead solder or lead-free solder, and are made by mixing silver-coated resin particles (resin particles coated with silver) with resin. Conductive adhesives are used, for example, as forming materials for electrodes and electrical wiring that make up electronic devices such as solar panels, liquid crystal displays, and touch panels. Furthermore, the pastes and films made by mixing the aforementioned silver-coated resin particles with resin also have excellent thermal conductivity and are therefore used as TIM (Thermal Interface Material) materials. 【0003】 For example, Patent Document 1 discloses silver-coated resin particles having high stress relaxation capacity, in which resin particles are used as the mother particles and the amount of silver contained in the silver coating layer is 60 to 90 parts by mass per 100 parts by mass of silver-coated particles. However, due to the soaring price of silver, there is a demand for more inexpensive conductive particles based on copper and nickel. Among these, copper is more preferable from the viewpoint of conductivity and thermal conductivity. Patent Document 2 discloses conductive particles in which resin particles are coated with copper as a material for anisotropic conductive films. 【0004】 Japanese Unexamined Patent Publication No. 2016-130354 (A) Japanese Unexamined Patent Application No. 2014-160546 (A) 【0005】Incidentally, in recent years, power electronics semiconductor elements used for high-power control in wind power generation, electric vehicles, hybrid vehicles, etc., generate a large amount of heat during operation and have a large surface area. Therefore, when joining these elements, it is necessary to ensure high bonding reliability even under thermal cycling loads. However, because copper is harder and has lower stress relaxation properties compared to silver, there was a risk of delamination between the resin particles and the coating layer under thermal cycling loads. Therefore, in filler-containing pastes that contain the aforementioned copper-coated resin particles as a filler, copper-coated resin particles with particularly excellent adhesion between the resin particles and the copper coating layer are required to improve the thermal cycling reliability of the bonded layer. 【0006】 This invention has been made in view of the circumstances described above, and aims to provide copper-coated resin particles that have excellent adhesion between the resin particles and the copper coating layer and excellent heat cycle resistance, and a filler-containing paste that contains these copper-coated resin particles as a filler. 【0007】 In order to solve the above problems, the inventors conducted diligent research and found that by arranging silicon dioxide on the surface of resin particles, it becomes possible to successfully plate copper onto the surface of the resin particles. 【0008】 The present invention has been made based on the above-mentioned findings, and the copper-coated resin particles of embodiment 1 of the present invention are copper-coated resin particles comprising resin particles made of a resin composition and a copper coating layer formed on the surface of the resin particles, characterized in that they contain silicon oxide in an amount of 0.05% by mass or more and 5.0% by mass or less, and also contain Sn and Pd. 【0009】 According to the copper-coated resin particles of Embodiment 1 of the present invention, since silicon oxide is contained in a range of 0.05% to 5.0% by mass, the hydrophilicity of the resin particle surface is improved, and Sn and Pd adhere uniformly to the resin particle surface, thereby improving the adhesion between the resin particles and the copper coating layer. Therefore, copper-coated resin particles with excellent heat cycle resistance can be provided. 【0010】The copper-coated resin particles of Embodiment 2 of the present invention are characterized in that, in the copper-coated resin particles of Embodiment 1 of the present invention, the 5% compressive modulus (5% K value) is in the range of 0.2 GPa to 3.5 GPa. According to the copper-coated resin particles of Embodiment 2 of the present invention, the 5% compressive modulus (5% K value) is in the range of 0.2 GPa to 3.5 GPa, which maintains sufficient shape retention due to the addition of fillers, and is sufficiently soft and easily deformable. For example, it is possible to suppress the occurrence of cracks in the cured paste of a paste containing these copper-coated resin particles as a filler. 【0011】 The copper-coated resin particles of embodiment 3 of the present invention are characterized in that, in the copper-coated resin particles of embodiment 1 or embodiment 2 of the present invention, the resin composition is one or more selected from acrylic resin, styrene resin, silicone resin, phenolic resin, urethane resin, and polyimide resin. According to the copper-coated resin particles of embodiment 3 of the present invention, since the resin composition is one or more selected from acrylic resin, styrene resin, silicone resin, phenolic resin, urethane resin, and polyimide resin, the resin particles have excellent flexibility and are particularly suitable as fillers. 【0012】 The copper-coated resin particles of embodiment 4 of the present invention are characterized in that, in any one of the copper-coated resin particles of embodiments 1 to 3 of the present invention, the particle size is in the range of 2 μm to 50 μm. According to the copper-coated resin particles of embodiment 4 of the present invention, since the particle size is in the range of 2 μm to 50 μm, the amount of copper used can be reduced, further cost reduction can be achieved, and it can be used as a filler for materials that form fine patterns. 【0013】The filler-containing paste of embodiment 5 of the present invention is characterized by containing copper-coated resin particles of any one of embodiments 1 to 4 of the present invention. According to the filler-containing paste of embodiment 5 of the present invention, since it contains copper-coated resin particles of any one of embodiments 1 to 4 of the present invention as a filler, the thermal cycle reliability of the cured product of this filler-containing paste can be improved, and it can be used stably as a conductive adhesive or heat transfer material even in applications where harsh thermal cycling is applied. 【0014】 According to the present invention, it is possible to provide copper-coated resin particles that have excellent adhesion between the resin particles and the copper coating layer and excellent heat cycle resistance, and a filler-containing paste that contains these copper-coated resin particles as a filler. 【0015】 This is a cross-sectional view of copper-coated resin particles according to one embodiment of the present invention. This is a flow chart showing a method for manufacturing copper-coated resin particles according to one embodiment of the present invention. This is an explanatory diagram of a semiconductor device using a paste-cured product according to one embodiment of the present invention. This is a photograph showing the SEM observation results of copper-coated resin particles of Example 1 of the present invention in the examples. This is a photograph showing the SEM observation results of copper-coated resin particles of Example 1 of the present invention in the examples. This is a photograph showing the SEM observation results of copper-coated resin particles of Example 2 of the present invention in the examples. This is a photograph showing the SEM observation results of copper-coated resin particles of Comparative Example 1 of the examples. This is a photograph showing the SEM observation results of copper-coated resin particles of Comparative Example 2 of the examples. This is a photograph showing the SEM observation results of copper-coated resin particles of Comparative Example 2 of the examples. 【0016】 Below, embodiments of the present invention, namely copper-coated resin particles and filler-containing paste, will be described with reference to the attached drawings. The embodiments described below are provided specifically to better illustrate the spirit of the invention and do not limit the present invention unless otherwise specified. 【0017】Figure 1 shows copper-coated resin particles 10, which are one embodiment of the present invention. The copper-coated resin particles 10 of this embodiment, as shown in Figure 1, for example, comprises resin particles 11 made of a resin composition and a copper coating layer 12 formed on the surface of the resin particles 11. The copper-coated resin particles 10 contain silicon dioxide in a range of 0.05% by mass or more and 5.0% by mass or less, and also contain Sn and Pd. Preferably, the Sn content is in the range of 0.01% by mass or more and 4.5% by mass or less, and the Pd content is in the range of 0.02% by mass or more and 2.0% by mass or less. 【0018】 In this embodiment, the silicon dioxide content in the copper-coated resin particles 10 is determined by taking a sample from the copper-coated resin particles 10, performing elemental analysis, and determining the silicon dioxide content (SiO₂) from the measured Si content. ２ This was calculated by converting it as follows: 【0019】 Furthermore, in the copper-coated resin particles 10 of this embodiment, it is preferable that the 5% compressive modulus (5% K value) is in the range of 0.2 GPa or more and 3.5 GPa or less. In addition, in the copper-coated resin particles 10 of this embodiment, it is preferable that the particle size is in the range of 2 μm or more and 50 μm or less. Furthermore, in the copper-coated resin particles 10 of this embodiment, it is preferable that the resin composition constituting the resin particles 11 is one or more selected from acrylic resin, styrene resin, silicone resin, phenolic resin, urethane resin, and polyimide resin. In the copper-coated resin particles 10 of this embodiment, since the interference effect with expansion and contraction is increased by imparting flexibility, it is more preferable to use urethane resin or acrylic resin, which have particularly excellent flexibility. 【0020】 The reasons for defining the copper-coated resin particles 10 in this embodiment as described above will be explained below. 【0021】(Silicon Oxide) In the copper-coated resin particles 10 of this embodiment, the inclusion of silicon oxide makes it possible to plate copper well onto the surface of the resin particles 11, thereby improving the adhesion between the resin particles 11 and the copper coating layer 12. Furthermore, by encapsulating some silicon oxide within the resin particles, the strength of the particles is improved, making them able to withstand mechanical deformation and high shear during dispersion. However, if the silicon oxide content in the copper-coated resin particles 10 is less than 0.05% by mass, there is a risk that the adhesion between the resin particles 11 and the copper coating layer 12 cannot be sufficiently improved, and the hardness of the copper-coated resin particles may be insufficient. On the other hand, if the silicon oxide content exceeds 5.0% by mass, there is a risk that the flexibility of the copper-coated resin particles 10 will decrease. For this reason, in the copper-coated resin particles 10 of this embodiment, the silicon oxide content is set within the range of 0.05% by mass or more and 5.0% by mass or less. 【0022】 Furthermore, in order to further improve the adhesion between the resin particles 11 and the copper coating layer 12, it is preferable that the silicon dioxide content in the copper-coated resin particles 10 be 0.05% by mass or more, and more preferably 0.2% by mass or more. In addition, in order to further ensure the flexibility of the copper-coated resin particles 10, it is preferable that the silicon dioxide content in the copper-coated resin particles 10 be 5.0% by mass or less, more preferably 3.2% by mass or less, and even more preferably 1.5% by mass or less. 【0023】 (Sn content) In the copper-coated resin particles 10 of this embodiment, if a catalytic treatment using Sn is performed as a pretreatment before plating the surface of the resin particles 11, Sn will be contained in the copper-coated resin particles 10. By limiting the Sn content to 4.5% by mass or less, the peeling of the copper coating layer 12 during thermal cycling load can be further suppressed. For this reason, in the copper-coated resin particles 10 of this embodiment, it is preferable to set the Sn content within the range of 0.01% by mass or more and 4.5% by mass or less. 【0024】Furthermore, the lower limit of the Sn content in the copper-coated resin particles 10 is more preferably 0.01% by mass or more, and more preferably 0.03% by mass or more. Also, the upper limit of the Sn content in the copper-coated resin particles 10 is more preferably 4.5% by mass or less, and more preferably 2.8% by mass or less. 【0025】 (Pd content) In the copper-coated resin particles 10 of this embodiment, if a catalytic treatment using Pd is performed as a pretreatment before plating the surface of the resin particles 11, Pd will be contained in the copper-coated resin particles 10. By limiting the Pd content to 2.0% by mass or less, the peeling of the copper coating layer 12 during thermal cycling load can be further suppressed. For this reason, in the copper-coated resin particles 10 of this embodiment, it is preferable to keep the Pd content within the range of 2.0% by mass or less. 【0026】 Furthermore, the lower limit of the Pd content in the copper-coated resin particles 10 is more preferably 0.02% by mass or more, and more preferably 0.04% by mass or more. Also, the upper limit of the Pd content in the copper-coated resin particles 10 is more preferably 2.0% by mass or less, and more preferably 1.2% by mass or less. 【0027】 (5% Compression Modulus (5% K Value)) In the copper-coated resin particles 10 of this embodiment, if the 5% compression modulus (5% K value) is 3.5 GPa or less, the flexibility of the copper-coated resin particles 10 is sufficiently ensured, so the occurrence of cracks in the cured paste of a paste containing these copper-coated resin particles 10 as a filler can be suppressed. On the other hand, if the 5% compression modulus (5% K value) is 0.2 GPa or more, the elasticity of the copper-coated resin particles 10 is ensured, and the shape retention and coating strength of the paste can be maintained. 【0028】Furthermore, in order to ensure greater flexibility, it is more preferable to set the upper limit of the 5% compressive modulus (5% K value) of the copper-coated resin particles 10 to 1.8 GPa or less, and even more preferable to set it to 0.6 GPa or less. In addition, in order to reliably maintain the shape retention of the paste and the strength of the coating film, it is more preferable to set the lower limit of the 5% compressive modulus (5% K value) of the copper-coated resin particles 10 to 0.35 GPa or more. 【0029】 (Particle size) In the copper-coated resin particles 10 of this embodiment, when the particle size is 2 μm or larger, the specific surface area does not become unnecessarily large, the amount of copper used to constitute the copper coating layer 12 can be reduced, and manufacturing costs can be kept low. On the other hand, in the copper-coated resin particles 10 of this embodiment, when the particle size is 50 μm or less, a paste containing these copper-coated resin particles 10 as a filler can be applied in a fine pattern, and can be applied to semiconductor devices with high integration or high precision. 【0030】 Furthermore, in order to further reduce the amount of copper used in the copper coating layer 12, it is more preferable to set the particle size of the copper-coated resin particles 10 to 4 μm or more, and even more preferable to set it to 10 μm or more. In addition, in order to accommodate even finer patterns, it is more preferable to set the particle size of the copper-coated resin particles 10 to 32 μm or less, and even more preferable to set it to 22 μm or less. 【0031】 (Resin composition) In this embodiment, when the resin composition constituting the resin particles 11 is one or more selected from acrylic resin, styrene resin, silicone resin, phenolic resin, urethane resin, and polyimide resin, the flexibility of the resin particles 11 is excellent, and the copper coating layer 12 can be formed stably. 【0032】 Next, an example of a method for manufacturing the copper-coated resin particles 10 according to this embodiment will be explained using the flow chart in Figure 2. 【0033】(Silicon Oxide Placement Process S01) First, silicon oxide is placed on the surface of the resin particles 11. Methods for placing silicon oxide include forming a silicate film on the surface of the resin particles 11 (Manufacturing Method 1), and physically attaching silicon oxide particles to the surface of the resin particles 11 (Manufacturing Method 2). 【0034】 As a first manufacturing method, for example, resin particles 11 can be dispersed in alcohol or a mixed solvent of water and alcohol, a predetermined amount of methyl silicate can be added, and a small amount of water or the like can be added as a catalyst to form a silicate film on the surface of the resin particles 11. As a second manufacturing method, for example, resin particles 11 and silicon dioxide particles can be mixed in predetermined amounts and subjected to a planetary ball mill or the like to adhere the silicon dioxide particles to the surface of the resin particles 11. The silicon dioxide particles can range in size from a few nanometers to a few micrometers, and can be spherical, needle-shaped, or bead-shaped. To improve adhesion and uniformity to the resin particles, it is also possible to use silicon dioxide particles that are surface-coated with inorganic compounds, organic compounds, or resins. Furthermore, the silicon dioxide can be added as particles or as an inorganic / organic silicon dioxide compound during the synthesis process of the core resin particles (polymerization process of monomers), and can be encapsulated not only on the surface but also within the resin particles. By encapsulating the copper within the resin particles, the deformation resistance of the copper-coated resin particles is improved, making it possible to prevent the peeling of the copper film. 【0035】 (Catalytic treatment step S02) Next, catalyst Sn (divalent Sn ions) is adsorbed onto resin particles 11 having silicon dioxide disposed on their surface. The resin particles 11 are added to an aqueous solution of a tin compound and stirred. Here, as the tin compound, for example, stannous chloride, stannous fluoride, stannous bromide, stannous iodide, etc. are used. Furthermore, catalyst Pd (divalent Pd ions) is adsorbed onto the resin particles 11. The resin particles 11 with the adsorbed Sn are added to an aqueous solution of a Pd compound and stirred. Here, as the Pd compound, for example, Pd(II) chloride, etc. are used. 【0036】(Copper Coating Process S03) Next, a copper coating layer 12 is formed by electroless plating of copper on the surface of the resin particles 11. As a method for forming the copper coating layer 12 by electroless plating, there are: (1) a method in which the resin particles 11 are put into an aqueous solution containing a complexing agent, a reducing agent, etc. to prepare a slurry, and an aqueous copper salt solution is dropped into this slurry; (2) a method in which the resin particles 11 are put into an aqueous copper salt solution containing a complexing agent to prepare a slurry, and an aqueous reducing agent solution is dropped into this slurry; (3) a method in which the resin particles 11 are put into an aqueous copper salt solution containing a complexing agent and a reducing agent to prepare a slurry, and an aqueous caustic alkali solution is dropped into this slurry. 【0037】 As the copper salt, copper nitrate or a substance obtained by dissolving copper in nitric acid can be used. As the complexing agent, salts such as ammonia, ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetate, nitrilotriacetic acid, triethylenetetraminehexaacetic acid, sodium thiosulfate, succinate, succinimide, citrate or iodide salt can be used. As the reducing agent, formalin, glucose, imidazole, Rochelle salt (sodium potassium tartrate), hydrazine and its derivatives, hydroquinone, L - ascorbic acid or formic acid can be used. As the reducing agent, formaldehyde is preferable, a mixture of two or more reducing agents containing at least formaldehyde is more preferable, and a mixture of a reducing agent containing formaldehyde and glucose is most preferable. 【0038】Furthermore, if divalent Sn ions or Pd ions are adsorbed on the surface of the resin particles 11 by the catalytic treatment step S02, the divalent Sn or Pd ions dissolve into tetravalent ions and release divalent electrons. Then, copper ions accept the divalent electrons and precipitate as metallic copper. This allows for the efficient formation of the copper coating layer 12. In this embodiment, since silicon oxide is arranged on the surface of the resin particles 11, it is possible to plate copper well onto the surface of the resin particles 11. The reason why the adhesion of copper improves when silicon oxide is formed on the surface is not clear, but possible reasons include its excellent affinity with the copper precipitated particles and improved adsorption effect of Sn and Pd. In addition, it is thought that the hydrophilicity of the surface of the resin particles on which silicon oxide is formed improves, making it easier for Sn and Pa to adhere. 【0039】 In the present invention, copper-coated resin particles coated with various oxidation inhibitors can be used to suppress the oxidation of the coated copper, and it is more preferable that they are coated with an antioxidant. Methods of using the antioxidant include adding a surface treatment agent wet after copper coating, and adding it as an auxiliary agent when making the paste. Examples of antioxidants include one or more selected from phenolic compounds, amine compounds, phosphorus compounds, sulfur compounds, carboxylic acid compounds, hydrazine compounds, and amide compounds. In addition, fatty acids or their metal salts that do not affect the properties of the paste when used as a conductive paste composition are also included. Fatty acids are not particularly limited, but examples include octanoic acid, oleic acid, stearic acid, decanoic acid, myristic acid, adipic acid, isostearic acid, citric acid, palmitic acid, etc. Alkali metal salts are preferred. Through the above process, copper-coated resin particles 10 of this embodiment are manufactured. 【0040】The filler-containing paste according to this embodiment contains a binder resin and the above-described copper-coated resin particles 10 as a filler. The binder resin is not particularly limited, and examples thereof include a thermoplastic resin and a composition that cures by heat or light, such as a curable resin composition. Examples of the thermoplastic resin include a styrene-butadiene block copolymer, an acrylic resin, an ethylene-vinyl acetate resin, and a phenoxy resin. Examples of the thermosetting resin composition include a resin composition containing, as a main component, a resin such as a silicone resin or an epoxy resin, or a mixture thereof. A binder resin that is compatible with the copper-coated resin particles is suitable in order to match the adhesion, hardness, electrical properties, electrothermal properties, etc. 【0041】 In order to improve the affinity (compatibility) with the binder resin, it is also possible to perform a surface treatment such as an organic acid on the surface of the copper-coated resin particles. Examples of the surface treatment 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-based polymers such as polyacrylic acid, amine compounds such as dodecylamine and octadecylamine, amine-based polymers such as polyetheramine, sulfide compounds such as octadecyl disulfide, thiol compounds such as dodecanethiol, and silane coupling agents. In addition, a solvent and additives may be contained as necessary. 【0042】Furthermore, in order to obtain higher electrical and thermal conductivity, conductive fillers other than the copper-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, but copper powder, which has excellent electrical and thermal conductivity properties, is preferred. In addition, it is more preferable to use flake-shaped (flat) particles rather than just spherical ones. The ratio of addition can be set to copper-coated resin particles 10:other conductive fillers = 5 to 95 wt%:95 to 5 wt%, depending on the desired electrical and thermal conductivity. The filler-containing paste of this embodiment is manufactured by weighing a predetermined amount of binder resin (for example, epoxy resin) and the above-mentioned copper-coated resin particles 10, and kneading them using planetary stirring, a three-roll mixing system, etc. 【0043】 The filler-containing paste of this embodiment, as shown in Figure 3 for example, forms a bonding layer 4 in a semiconductor device 1 that joins the circuit layer 2 of an insulating circuit substrate with the semiconductor element 3. That is, by applying the filler-containing paste of this embodiment to the mounting surface of the circuit layer 2, stacking the semiconductor element 3, and heat-treating it, a bonding layer 4 composed of the cured product of the filler-containing paste of this embodiment is formed, and the circuit layer 2 and the semiconductor element 3 are joined together. 【0044】 In this embodiment, the filler-containing paste contains the above-mentioned copper-coated resin particles 10 as a filler, and therefore has excellent electrical and thermal conductivity, enabling electrical connection between the semiconductor element 3 and the circuit layer 2, and efficiently dissipating the heat generated by the semiconductor element 3 to the insulating circuit board side. Furthermore, because the bonding layer 4 has excellent thermal cycle reliability, it is possible to suppress delamination between the semiconductor element 3 and the circuit layer 2 even when subjected to thermal cycling. 【0045】 According to the copper-coated resin particles 10 of this embodiment, which have the above configuration, silicon dioxide is contained in a range of 0.05% to 5.0% by mass, which improves the hydrophilicity of the resin particle surface, and Sn and Pd adhere uniformly to the resin particle surface, thereby improving the adhesion between the resin particles and the copper coating layer. 【0046】 In this embodiment, when the 5% compressive modulus (5% K value) of the copper-coated resin particles 10 is within the range of 0.2 GPa to 3.5 GPa, the shape retention and mechanical strength of the copper coating film are maintained, and it is sufficiently soft and easily deformable. For example, crack formation in the cured paste of a paste containing these copper-coated resin particles 10 as a filler can be suppressed. 【0047】 In this embodiment, when the resin composition constituting the resin particles 11 is one or more selected from acrylic resin, styrene resin, silicone resin, phenolic resin, urethane resin, and polyimide resin, the resin particles 11 exhibit excellent flexibility and are particularly suitable as fillers. 【0048】 In this embodiment, when the particle size of the copper-coated resin particles 10 is within the range of 2 μm to 50 μm, the amount of copper used can be reduced, thereby lowering costs, and it can also be used as a filler for materials that form fine patterns. 【0049】 According to this embodiment of the filler-containing paste, since it contains copper-coated resin particles 10 as the filler, it has excellent thermal cycle resistance and can be stably used as a conductive adhesive or heat transfer material even in applications where harsh thermal cycles are applied. 【0050】 Although one embodiment of the present invention has been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical spirit of the invention. In this embodiment, the invention has been described as being applicable to a filler-containing paste used when forming a bonding layer that joins a circuit layer and a semiconductor element of a semiconductor device, but the invention is not limited thereto and may be used for other purposes as well. 【0051】 The verification experiments conducted to confirm the effectiveness of the present invention will be described. 【0052】 (Examples 1, 3-5, 8, Comparative Examples 4, 5) The resin particles shown in Table 1 were dispersed in an ethanol solvent to obtain a slurry with a solid content of 5% by mass. Silicon oxide (SiO₂) was added to this slurry.２ Silicon oxide coated resin particles were prepared by adding a predetermined amount of methyl silicate so that the concentration reached the values ​​shown in Table 1, adding a small amount of nitric acid as a catalyst, and then adding a very small amount of water dropwise. As raw materials for silica film formation, not only methyl silicate but also organic silicates such as ethyl silicate and propyl silicate, and inorganic silicon salts such as sodium silicate can be used. After filtration and washing, the mixture was dispersed in water, stannous chloride was added so that the tin concentration reached the values ​​shown in Table 1, the mixture was stirred at 60°C for 1 hour, and filtered again. The resulting cake was dispersed in water to obtain resin particles (catalyzed resin particles) with divalent tin ions adsorbed on the surface. Subsequently, after washing, the mixture was dispersed in water, Pd(II) chloride was added so that the Pd concentration reached the values ​​shown in Table 1, the mixture was stirred at 60°C for 1 hour, and filtered again. The resulting cake was dispersed in water to obtain resin particles (catalyzed resin particles) with divalent Pd ions adsorbed on the surface. Subsequently, a copper coating layer was formed on the surface of the resin particles by electroless plating so that the Cu concentration matched the values ​​shown in Table 1. 【0053】 (Examples 2, 6, 7, Comparative Examples 2, 3) Resin particles and silicon oxide particles with an average particle size of 10 nm shown in Table 1 were mixed so that the silicon oxide particle content was as shown in Table 1, and silicon oxide particles were attached to the surface of the resin particles by planetary ball milling. A copper coating layer was formed on the resin particles with silicon oxide particles attached to the surface by catalytic treatment and electroless plating, similar to Examples 1, 3-5, 8, and Comparative Examples 4, 5. 【0054】 (Comparative Examples 1 and 6) Acrylic particles (resin particles) were dispersed in water, stannous chloride was added to achieve a Sn concentration of 0.1% by mass, the mixture was stirred at 60°C for 1 hour, and filtered. The resulting cake was dispersed in water to obtain resin particles (catalyzed resin particles) on which divalent tin ions were adsorbed on the surface. After filtering and washing, the particles were dispersed in water, Pd(II) chloride was added to achieve a Pd concentration equal to the values ​​shown in Table 1, the mixture was stirred at 60°C for 1 hour, and filtered again. The resulting cake was dispersed in water to obtain resin particles (catalyzed resin particles) on which divalent Pd ions were adsorbed on the surface. A copper coating layer was formed on the surface of these resin particles by electroless plating. 【0055】 The copper-coated resin particles of the present invention examples 1-8 and comparative examples 1-6 obtained as described above were evaluated as follows. 【0056】 (5% Compression Modulus (5% K Value) of Copper-Coated Resin Particles) First, a compression test was performed on one copper-coated resin particle using a microcompression tester (Fischer Instruments, model number: HM500) with a flat indenter, under conditions of a load change rate of 0.3 mN / s and 20°C. The displacement and load when the copper-coated resin particle was compressed by 5% relative to its major axis were measured. At this time, the starting point (zero point) of the displacement measurement was defined not as the point when the microcompression tester recognized contact with the copper-coated resin particle, but as the point when the load applied to the copper-coated resin particle was changed by the microcompression tester. Next, the measured displacement and load were substituted into (1) below to calculate the 5% compression modulus (5% K value). The evaluation results are shown in Table 1. 【0057】 Equation (1): 5% Compression Modulus (5% K value) [GPa] = 3F / (2S3R)¹ / ² F: Load when copper-coated resin particles are compressed by 5% [N] S: Displacement when copper-coated resin particles are compressed by 5% [mm] R: Radius of copper-coated resin particles before compression [mm] 【0058】 (Presence or absence of delamination of the copper coating layer after thermal cycling) Furthermore, the copper-coated resin particles of the obtained Examples 1-8 and Comparative Examples 1-6 were subjected to a thermal cycling test between -20°C and 80°C, and their cross-sections were observed using SEM to confirm whether or not the copper coating layer had delaminated. The evaluation results are shown in Table 1. 【0059】 (Volume Resistivity of the Coating Film) Using the copper-coated resin particles described above, an epoxy resin-based filler-containing paste with a filler content of 60 vol% was prepared using a rotation-orbit 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-probe method. The evaluation results are shown in Table 1. 【0060】 【0061】The 5% compressive modulus (5% K value) of the copper-coated resin particles of Invention Example 1 was measured to be 0.9 GPa. A thermal cycling test was performed on the copper-coated resin particles of Invention Example 1 between -20°C and 80°C, and the cross-section was observed using SEM. The observation results are shown in Figures 4A and 4B. No peeling of the copper coating layer was observed even after the thermal cycling test. The volume resistivity of the coating film formed using a filler-containing paste containing the copper-coated resin particles of Invention Example 1 as a filler was 7.0 × 10⁻⁶. －３ It was Ω·cm. 【0062】 The 5% compressive modulus (5% K value) of the copper-coated resin particles of Invention Example 2 was measured to be 1.5 GPa. After performing a thermal cycling test between -20°C and 80°C on the copper-coated resin particles of Invention Example 2, the cross-section was observed using SEM. No peeling of the copper coating layer was observed even after the thermal cycling test. The volume resistivity of the coating film formed using a filler-containing paste containing the copper-coated resin particles of Invention Example 2 as a filler was 2.0 × 10⁻⁶. －３ It was Ω·cm. 【0063】 The 5% compressive modulus (5% K value) of the copper-coated resin particles of Invention Example 3 was measured to be 0.5 GPa. A thermal cycling test was performed on the copper-coated resin particles of Invention Example 3 between -20°C and 80°C, and the cross-section was observed using SEM. No peeling of the copper coating layer was observed even after the thermal cycling test. The volume resistivity of the coating film formed using a filler-containing paste containing the copper-coated resin particles of Invention Example 3 as a filler was 1.0 × 10⁻⁶. －３ It was Ω·cm. 【0064】 The 5% compressive modulus (5% K value) of the copper-coated resin particles of Invention Example 4 was measured to be 3.2 GPa. After performing a thermal cycling test between -20°C and 80°C on the copper-coated resin particles of Invention Example 4, the cross-section was observed using SEM. No peeling of the copper coating layer was observed even after the thermal cycling test. The volume resistivity of the coating film formed using a filler-containing paste containing the copper-coated resin particles of Invention Example 4 as a filler was 3.0 × 10⁻⁶. －２ It was Ω·cm. 【0065】As a result of measuring the 5% compression elastic modulus (5% K value) of the copper-coated resin particles of Example 5 of the present invention, it was 1.8 GPa. In the copper-coated resin particles of Example 5 of the present invention, after performing a thermal cycle test of -20°C ←→ 80°C, the cross-section was observed by SEM. Even after the thermal cycle test, no peeling of the copper coating layer was observed. The volume resistivity of the coating film formed using the filler-containing paste containing the copper-coated resin particles of Example 5 of the present invention as a filler was 5.0×10 －３ Ω·cm. 【0066】 As a result of measuring the 5% compression elastic modulus (5% K value) of the copper-coated resin particles of Example 6 of the present invention, it was 2.5 GPa. In the copper-coated resin particles of Example 6 of the present invention, after performing a thermal cycle test of -20°C ←→ 80°C, the cross-section was observed by SEM. The observation results are shown in FIG. 5. Even after the thermal cycle test, no peeling of the copper coating layer was observed. The volume resistivity of the coating film formed using the filler-containing paste containing the copper-coated resin particles of Example 6 of the present invention as a filler was 9.0×10 －２ Ω·cm. 【0067】 As a result of measuring the 5% compression elastic modulus (5% K value) of the copper-coated resin particles of Example 7 of the present invention, it was 2.0 GPa. In the copper-coated resin particles of Example 7 of the present invention, after performing a thermal cycle test of -20°C ←→ 80°C, the cross-section was observed by SEM. Even after the thermal cycle test, no peeling of the copper coating layer was observed. The volume resistivity of the coating film formed using the filler-containing paste containing the copper-coated resin particles of Example 7 of the present invention as a filler was 1.0×10 －３ Ω·cm. 【0068】 As a result of measuring the 5% compression elastic modulus (5% K value) of the copper-coated resin particles of Example 8 of the present invention, it was 0.2 GPa. In the copper-coated resin particles of Example 8 of the present invention, after performing a thermal cycle test of -20°C ←→ 80°C, the cross-section was observed by SEM. Even after the thermal cycle test, no peeling of the copper coating layer was observed. The volume resistivity of the coating film formed using the filler-containing paste containing the copper-coated resin particles of Example 8 of the present invention as a filler was 4.0×10 －３ Ω·cm. 【0069】The 5% compressive modulus (5% K value) of the copper-coated resin particles of Comparative Example 1 was measured to be 1.3 GPa. A thermal cycling test was performed on the copper-coated resin particles of Comparative Example 1 between -20°C and 80°C, and the cross-section was observed using SEM. The observation results are shown in Figure 6. After the thermal cycling test, peeling of the copper coating layer was confirmed. The volume resistivity of the coating film formed using a filler-containing paste containing the copper-coated resin particles of Comparative Example 1 as a filler was 9.0 × 10⁻⁶. －２ It was Ω·cm. 【0070】 The 5% compressive modulus (5% K value) of the copper-coated resin particles of Comparative Example 2 was measured to be 5.2 GPa. A thermal cycling test was performed on the copper-coated resin particles of Comparative Example 2 between -20°C and 80°C, and the cross-section was observed using SEM. The observation results are shown in Figures 7A, 7B, and 7C. After the thermal cycling test, peeling of the copper coating layer was confirmed. The volume resistivity of the coating film formed using a filler-containing paste containing the copper-coated resin particles of Comparative Example 2 as a filler was 8.0 × 10⁻⁶. －１ It was Ω·cm. 【0071】 The 5% compressive modulus (5% K value) of the copper-coated resin particles of Comparative Example 3 was measured to be 1.0 GPa. A thermal cycling test was performed on the copper-coated resin particles of Comparative Example 3 between -20°C and 80°C, and the cross-section was observed using SEM. After the thermal cycling test, peeling of the copper coating layer was confirmed. The volume resistivity of the coating film formed using a filler-containing paste containing the copper-coated resin particles of Comparative Example 3 as a filler was 1.0 × 10⁻⁶. －１ It was Ω·cm. 【0072】 The 5% compressive modulus (5% K value) of the copper-coated resin particles of Comparative Example 4 was measured to be 3.7 GPa. A thermal cycling test was performed on the copper-coated resin particles of Comparative Example 4 between -20°C and 80°C, and the cross-section was observed using SEM. After the thermal cycling test, peeling of the copper coating layer was confirmed. The volume resistivity of the coating film formed using a filler-containing paste containing the copper-coated resin particles of Comparative Example 4 as a filler was 1.0 × 10⁻⁶. －２ It was Ω·cm. 【0073】The 5% compressive modulus (5% K value) of the copper-coated resin particles of Comparative Example 5 was measured to be 2.5 GPa. A thermal cycling test was performed on the copper-coated resin particles of Comparative Example 5 between -20°C and 80°C, and the cross-section was observed using SEM. After the thermal cycling test, peeling of the copper coating layer was confirmed. The volume resistivity of the coating film formed using a filler-containing paste containing the copper-coated resin particles of Comparative Example 5 was 5.0 × 10⁻⁶. －２ It was Ω·cm. 【0074】 The 5% compressive modulus (5% K value) of the copper-coated resin particles of Comparative Example 6 was measured to be 2.0 GPa. A thermal cycling test was performed on the copper-coated resin particles of Comparative Example 6 between -20°C and 80°C, and the cross-section was observed using SEM. After the thermal cycling test, peeling of the copper coating layer was confirmed. The volume resistivity of the coating film formed using a filler-containing paste containing the copper-coated resin particles of Comparative Example 6 as a filler was 3.0 × 10⁻⁶. －１ It was Ω·cm. 【0075】 As described above, it has been confirmed that the present invention provides copper-coated resin particles with excellent adhesion between the resin particles and the copper coating layer, and excellent heat cycle resistance, as well as a filler-containing paste containing these copper-coated resin particles as a filler. 【0076】 The copper-coated resin particles and filler-containing paste of the present invention can be used as anisotropic conductive film-forming agents (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. 【0077】 10 Copper-coated resin particles 11 Resin particles 12 Copper coating layer

Claims

1. Copper-coated resin particles comprising resin particles made of a resin composition and a copper coating layer formed on the surface of the resin particles, characterized in that the copper-coated resin particles contain silicon dioxide in an amount of 0.05% by mass or more and 5.0% by mass or less, and also contain Sn and Pd.

2. Copper-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 copper-coated resin particles according to claim 1, characterized in that the resin composition is one or more selected from acrylic resin, styrene resin, silicone resin, phenolic resin, urethane resin, and polyimide resin.

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

5. A filler-containing paste characterized by containing copper-coated resin particles as described in any one of claims 1 to 4.

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