Silver-coated resin particles and paste containing fillers

Abstract

The product comprises resin particles (11) composed of a resin composition and a silver-coated resin particle (10) formed on the surface of the resin particles (11), characterized in that it contains titanium oxide in an amount ranging from 0.05% to 12.00% by mass while the Sn content is 0.20% by mass or less. Preferably, the 5% compressive modulus (5% K value) is in the range of 0.2 GPa to 3.5 GPa. Preferably, the aforementioned resin composition is selected from one or more of acrylic resin, styrene resin, phenolic resin, urethane resin, and polyimide resin.

Description

Technical Field

[0001] This invention relates to silver-coated resin particles and pastes containing fillers. This case asserts priority based on Japanese Patent Application No. 2024-061053, filed on April 4, 2024, and the contents of that application are incorporated herein by reference. Prior Technology

[0002] As a conductive material to replace, for example, lead solder or lead-free solder, conductive adhesives such as conductive pastes or conductive films are known, which are formed by mixing silver-coated resin particles with resin. The silver-coated resin particles are formed by coating resin particles with silver. The conductive adhesive is used as a forming material for electrodes or electrical wiring, which constitute electronic devices such as solar panels, liquid crystal displays, and touch screens. Furthermore, the pastes or films made by mixing silver-coated resin particles with resin, as described above, are also used as TIM (Thermal Interface Material) materials due to their excellent thermal conductivity.

[0003] As for the aforementioned silver-coated resin particles, for example, Patent Document 1 discloses a silver-coated resin particle in which Sn (tin) is used as a pretreatment to catalyze the resin particles, and silver is electrolessly plated onto the resin particles that have undergone the pretreatment, thereby improving the adhesion between the resin particles and the silver coating layer. [Previous Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2015-199970 (A) Summary of the Invention

[0005] [The problem that the invention aims to solve] However, semiconductor components used in power electronics for high-power control of wind power generation, electric vehicles, and hybrid vehicles have been used recently. Due to the large amount of heat generated during operation and the large area involved, high bonding reliability must be ensured when bonding these components, even under thermal cycling loads. Therefore, in pastes containing silver-coated resin particles as fillers, in order to improve the thermal cycling reliability of the bonding layer, silver-coated resin particles with particularly excellent adhesion to the silver coating layer are required.

[0006] This invention was made in view of the foregoing circumstances, and its purpose is to provide silver-coated resin particles with excellent adhesion to the silver coating and excellent heat cycle resistance, and a paste containing the silver-coated resin particles as a filler. [Methods used to solve problems]

[0007] To address the aforementioned issues, the inventors, through in-depth research, have arrived at the following conclusion: When Sn used as a pretreatment (catalytic treatment) for plating is present in excessive amounts, the silver coating becomes easily peeled off under thermal cycling loads; therefore, the Sn content must be reduced. Furthermore, it has been observed that by depositing titanium dioxide on the surface of the resin particles, silver can be effectively plated onto the surface of the resin particles.

[0008] The present invention is made based on the above-mentioned insights. A silver-coated resin particle of embodiment 1 of the present invention is characterized in that it comprises resin particles composed of resin composition and a silver coating layer formed on the surface of the resin particles, wherein the silver coating layer contains titanium oxide in the range of 0.05% by mass to 12.00% by mass, and the content of Sn is 0.20% by mass or less.

[0009] By means of the silver-coated resin particles of Embodiment 1 of the present invention, since titanium oxide is contained in the range of 0.05% by mass to 12.00% by mass, silver can be well plated on the surface of the resin particles, thereby reducing the amount of Sn used during catalytic treatment. Furthermore, since the Sn content is limited to 0.20% by mass or less, the peeling of the silver coating layer under thermal cycling load can be suppressed. Therefore, it is possible to provide silver-coated resin particles with excellent adhesion to the resin particles and excellent thermal cycling resistance.

[0010] The silver-coated resin particles of Embodiment 2 of the present invention, in the silver-coated resin particles of Embodiment 1 of the present invention, are 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 Embodiment 2 of the present invention, having a 5% compressive modulus (5% K value) in the range of 0.2 GPa to 3.5 GPa, can maintain sufficient shape retention while being sufficiently soft and easily deformable, as provided by the addition of fillers. Therefore, for example, a paste made by using these silver-coated resin particles as fillers can suppress the generation of cracks in the hardened paste.

[0011] The silver-coated resin particles of embodiment 3 of the present invention, in the silver-coated resin particles of embodiment 1 or embodiment 2 of the present invention, are characterized in that the aforementioned resin composition is selected from one or more of acrylic resin, styrene resin, phenolic resin, urethane resin, and polyimide resin. The silver-coated resin particles of the present invention have excellent softness, as the aforementioned resin composition is selected from one or more of acrylic resin, styrene resin, phenolic resin, urethane resin, and polyimide resin, making them particularly suitable as fillers.

[0012] The silver-coated resin particles of the present invention, in any of the silver-coated resin particles of the present invention, from the present invention to the present invention, are characterized in that the particle size is in the range of 2 μm to 50 μm. The silver-coated resin particles of the present invention (Form 4) have a particle size in the range of 2 μm to 50 μm, which can reduce the amount of expensive silver used and thus reduce costs, while also being used as fillers for forming pastes and the like that of fine patterns.

[0013] A paste containing filler according to embodiment 5 of the present invention is characterized in that it comprises an adhesive resin and silver-coated resin particles of any one of embodiments 1 to 3 of the present invention as fillers. By means of the filler-containing paste of embodiment 5 of the present invention, since it contains silver-coated resin particles as fillers in any one of embodiments 1 to 4 of the present invention, the thermal cycling reliability of the hardened paste containing fillers can be improved. Even in applications subjected to severe thermal cycling, it can be stably used as a conductive adhesive or thermally conductive material. [The effects of the invention]

[0014] The present invention provides silver-coated resin particles with excellent adhesion to the silver coating and excellent heat cycle resistance, and a paste containing the silver-coated resin particles as a filler. Simple Explanation of the Diagram

[0015] [Figure 1] Cross-sectional view of silver-coated resin particles related to one embodiment of the present invention. [Figure 2] shows a flowchart of a method for manufacturing silver-coated resin particles related to one embodiment of the present invention. [Figure 3] An explanatory diagram of a semiconductor device made using a paste curing material related to one embodiment of the present invention. [Figure 4A] shows a photograph of the SEM observation results of the silver-coated resin particles of Example 1 of the present invention in the embodiment. [Figure 4B] shows a photograph of the SEM observation results of the silver-coated resin particles of Example 1 of the present invention in the embodiment. [Figure 5] shows a photograph of the SEM observation results of the silver-coated resin particles of Example 6 of the present invention in the embodiment. [Figure 6A] shows a photograph of the SEM observation results of the silver-coated resin particles of Comparative Example 2 in the embodiments. [Figure 6B] shows a photograph of the SEM observation results of the silver-coated resin particles of Comparative Example 2 in the embodiments. [Figure 7] shows a photograph of the SEM observation results of the silver-coated resin particles of Comparative Example 4 in the embodiments. Implementation

[0016] Hereinafter, silver-coated resin particles and filler-containing pastes, which are embodiments of the present invention, will be described with reference to the accompanying drawings. It should be noted that the embodiments described below are specifically provided for a better understanding of the spirit of the invention, and unless otherwise specified, are not intended to limit the scope of the invention.

[0017] Figure 1 shows a silver-coated resin particle 10 as one embodiment of the present invention. As shown in Figure 1, the silver-coated resin particle 10 of this embodiment includes, for example, resin particles 11 composed of a resin composition and a silver coating layer 12 formed on the surface of the resin particles 11. Then, the silver-coated resin particles 10 contain titanium oxide in a range of 0.05% to 12.00% by mass, while the Sn content is 0.20% by mass or less. The silver-coated resin particles 10 may also contain silicon oxide. The silicon oxide content is preferably set to 3.00% 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 sample of the silver-coated resin particles 10 for elemental analysis and converting the obtained Ti content into titanium oxide (TiO2). Furthermore, the Sn content in the silver-coated resin particles 10 is determined by elemental analysis of a sample taken from the silver-coated resin particles 10, and the amount of Sn obtained is the Sn content.

[0019] Furthermore, 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 to 3.5 GPa. Furthermore, in the silver-coated resin particles 10 of this embodiment, the particle size is preferably in the range of 2 μm to 50 μm. Furthermore, in the silver-coated resin particles 10 of this embodiment, it is preferable that the resin composition constituting the resin particles 11 is selected from one or more of acrylic resin, styrene resin, phenolic resin, urethane resin, and polyimide resin. In the silver-coated resin particles 10 of this embodiment, by imparting softness, the interference effect on expansion and contraction is increased. Therefore, it is preferable to use a urethane resin or an acrylic resin, which has particularly excellent softness.

[0020] The reasons for the silver-coated resin particles 10 in this embodiment being as specified above will be explained below.

[0021] (Titanium oxide) In the silver-coated resin particles 10 of this embodiment, by including titanium oxide, silver can be well deposited on the surface of the resin particles 11, thereby improving the adhesion between the resin particles 11 and the silver coating layer 12. Furthermore, by encapsulating a portion of the titanium oxide within the resin particles, the particle strength can be improved, and the particles can withstand high shear during mechanical deformation or dispersion. Here, if the titanium oxide content in the silver-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 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 softness of the silver-coated resin particles 10 may be reduced. Therefore, in the silver-coated resin particles 10 of this embodiment, the content of titanium oxide is set to be in the range of 0.05% by mass or more and 12.00% by mass or less.

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

[0023] (Sn content) In the silver-coated resin particles 10 of this embodiment, if Sn is used to perform catalytic treatment as a pretreatment before plating the surface of the resin particles 11, the silver-coated resin particles 10 will contain Sn. Here, if the Sn content exceeds 0.20% by mass, the silver coating layer 12 may become easy to peel off under thermal cycling load. Therefore, in the silver-coated resin particles 10 of this embodiment, the content of Sn is limited to 0.20% by mass or less.

[0024] In order to more effectively suppress the peeling of the silver coating layer 12 under thermal cycling load, it is preferable to set the Sn content in the silver coating resin particles 10 to 0.20% by mass or less, and even more preferably to 0.10% by mass or less. Furthermore, the Sn content in the silver-coated resin particles 10 is not particularly limited. In order to effectively improve adhesion, it is preferable to set the Sn content to 0.00% by mass or more, and even more preferably to 0.05% by mass or more.

[0025] (5% compressive modulus (5% K value)) In the silver-coated resin particles 10 of this embodiment, if the 5% compressive modulus (5% K value) is 3.5 GPa or less, the softness of the silver-coated resin particles 10 can be sufficiently ensured. Therefore, the paste containing these silver-coated resin particles 10 as fillers can suppress the generation of cracks in the hardened paste. On the other hand, if the 5% compressive modulus (5% K value) is above 0.2 GPa, the elasticity of the silver-coated resin particles 10 can be ensured, and the shape retention and coating strength of the paste can be maintained.

[0026] Furthermore, to further ensure flexibility, it is preferable to set the upper limit of the 5% compressive modulus (5% K value) of the silver-coated resin particles 10 to 1.5 GPa or less, and more preferably to 0.5 GPa or less. Furthermore, in order to ensure the shape retention and coating strength of the paste, it is preferable to set the lower limit of the 5% compressive modulus (5% K value) of the silver-coated resin particles 10 to 0.3 GPa or higher.

[0027] (particle size) In the silver-coated resin particles 10 of this embodiment, if the particle size is 2 μm or more, the specific surface area will not become larger than required, and the amount of silver used to constitute the silver coating layer 12 can be suppressed, thereby reducing manufacturing costs. On the other hand, in the silver-coated resin particles 10 of this embodiment, if the particle size is 50 μm or less, the paste containing these silver-coated resin particles 10 as fillers can be coated with a fine pattern, making it suitable for high-integration or high-precision semiconductor devices, etc.

[0028] Furthermore, in order to further suppress the amount of silver used in constituting the silver coating layer 12, it is preferable to set the particle size of the silver coating resin particles 10 to 4 μm or more, and more preferably to 6 μm or more. Furthermore, in order to correspond to finer patterns, it is preferable to set the particle size of the silver-coated resin particles 10 to 15 μm or less, and more preferably to 10 μm or less.

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

[0030] Next, an example of a method for manufacturing the silver-coated resin particles 10 in this embodiment will be described using the flowchart in FIG2.

[0031] (Titanium oxide preparation step S01) First, titanium oxide is deposited on the surface of the resin particles 11. Methods for depositing titanium oxide include forming a titanate film on the surface of the resin particles 11 (method 1) and physically attaching titanium oxide particles to the surface of the resin particles 11 (method 2). Alternatively, trace amounts of silicon oxide can also be deposited together with titanium oxide.

[0032] As a preparation method 1, for example, resin particles 11 are dispersed in a mixed solvent of water and ethanol, and a specified amount of titanium isopropoxide is added, along with a trace amount of water as a catalyst, thereby forming a titanate film on the surface of the resin particles 11. As in method 2, for example, a specified amount of resin particles 11 and titanium dioxide particles are mixed and subjected to a planetary ball mill, thereby adhering the titanium dioxide particles to the surface of the resin particles 11. The titanium dioxide particles can range from fine particles of several nm to large particles of several μm, and their shapes can be spherical, needle-like, or beaded. To improve the adhesion and uniformity to the resin particles, titanium dioxide particles coated with inorganic compounds, organic compounds, resins, etc., can also be used. Furthermore, this titanium dioxide is added as a particle or an inorganic / organic titanium compound in the synthesis step (monomer polymerization step) of the core resin particles, not only on the surface but also encapsulated within the resin particles. By encapsulating it within the resin particles, the deformation resistance of the silver-coated resin particles can be improved, thus preventing the silver film from peeling off.

[0033] (Catalyzing process step S02) Next, tin (divalent tin ions) that act as a catalyst is adsorbed onto resin particles 11 on which titanium oxide is disposed. The resin particles 11 described above were added to an aqueous solution of a tin compound and stirred. Here, tin compounds such as stannous chloride, stannous fluoride, stannous bromide, and stannous iodide can be used.

[0034] (Silver coating step S03) Next, a silver coating layer 12 is formed by electroless silver plating on the surface of the resin particles 11. As a method for forming a silver coating layer 12 by electroless plating, examples include (1) adding resin particles 11 to an aqueous solution containing a chelating agent and a reducing agent to prepare a slurry, and then dripping a silver salt aqueous solution onto the slurry; (2) adding resin particles 11 to an aqueous solution containing a chelating agent to prepare a slurry, and then dripping a reducing agent aqueous solution onto the slurry; and (3) adding resin particles 11 to an aqueous solution containing a chelating agent and a reducing agent to prepare a slurry, and then dripping a caustic alkali aqueous solution onto the slurry.

[0035] Silver salts, such as silver nitrate or substances that dissolve silver in nitric acid, can be used. Salts of ammonia, ethylenediaminetetraacetic acid (EDTA), ethylenediaminetetraacetic acid tetrasodium (EDTA), nitrotriacetic acid, triethylenetetraaminehexaacetic acid (TTHAA), sodium thiosulfate, succinate, succinimide salts, citrates, or iodides can be used. Reducing agents, such as formalin, glucose, imidazole, Rochelle salt (sodium potassium tartrate), hydrazine and its derivatives, hydroquinone, L-ascorbic acid, or formic acid, can be used. Formaldehyde is preferred as a reducing agent, and more preferably a mixture of two or more reducing agents containing at least formaldehyde; most preferably a mixture of reducing agents containing formaldehyde and glucose.

[0036] In the case where divalent tin ions are adsorbed onto the surface of resin particles 11 through the catalytic treatment step S02, the divalent tin ions become tetravalent ions and dissolve, releasing divalent electrons. Then, silver ions receive divalent electrons and are deposited as metallic silver. Therefore, a silver coating layer 12 can be formed efficiently. However, if the Sn content increases through the catalytic treatment step S02, there is a risk of peeling between the resin particles 11 and the silver coating layer 12 under thermal cycling load. Therefore, the implementation of the catalytic treatment step S02 needs to be reviewed considering the Sn content. In this embodiment, since titanium oxide is disposed on the surface of the resin particles 11, even if the Sn content is reduced through the catalytic treatment step S02, silver can still be well plated on the surface of the resin particles 11. The reason why forming titanium oxide on the surface can improve the adhesion of silver is not clear, but it is believed that: the affinity with silver precipitated particles is an excellent factor, and the adsorption effect of Sn is improved.

[0037] By following the steps described above, silver-coated resin particles 10, which are the embodiment of this invention, can be manufactured.

[0038] The paste containing filler in this embodiment is configured to include an adhesive resin and silver-coated resin particles 10 as described above, which serve as fillers. The adhesive resin is not particularly limited and can be, for example, a thermoplastic resin or a curable resin composition that can be cured by heat or light. Examples of thermoplastic resins include styrene-butadiene block copolymers, acrylic resins, ethylene-vinyl acetate resins, and phenoxy resins. Examples of thermosetting resin compositions include resins such as polysiloxane resins and epoxy resins, or resin compositions containing mixtures of these as main components. For suitability in terms of adhesion, hardness, electrical properties, and electrothermal properties, a resin composition with good compatibility with the silver-coated resin particles is preferred. To improve compatibility (compatibility) with adhesive resins, the surface of silver-coated resin particles can be treated with organic acids or the like. 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 dodecyl mercaptan; and silane coupling agents. Shang, depending on the needs, may also contain solvents and additives. Furthermore, to obtain higher electrical and thermal conductivity, conductive fillers other than 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. Silver powder, which has excellent electrical and thermal conductivity, is preferred. The particle shape is not limited to spherical shapes; flake (flat) particles are also preferred. Regarding the addition ratio, depending on the desired electrical and thermal conductivity, it can be set as silver-coated resin particles 10: other conductive fillers = 5~95% by mass: 95~5% by mass. By weighing a specified amount of adhesive resin (e.g., epoxy resin) and the aforementioned silver-coated resin particles 10, and mixing them using a planetary mixer, a three-roll mill, or similar method, a paste containing fillers, as described in this embodiment, can be produced.

[0039] As shown in FIG3, the filler-containing paste of this embodiment is used to form a bonding layer 4 in the semiconductor device 1. The bonding layer 4 is used to bond the circuit layer 2 of the insulating circuit board and the semiconductor element 3. That is, the filler-containing paste of this embodiment is applied to the mounting surface of the circuit layer 2, the semiconductor element 3 is laminating, and then heat treatment is performed to form a bonding layer 4 composed of the hardened filler-containing paste of this embodiment, thereby bonding the "circuit layer 2" and the "semiconductor element 3".

[0040] Here, the paste containing filler in this embodiment contains the aforementioned silver-coated resin particles 10 as filler, thus exhibiting excellent electrical and thermal conductivity. It can electrically connect the semiconductor element 3 to the circuit layer 2 while efficiently dissipating heat generated by the semiconductor element 3 to the insulating circuit board side. Furthermore, the bonding layer 4 has excellent thermal cycling reliability, suppressing the peeling of the semiconductor element 3 from the circuit layer 2 even under thermal cycling conditions.

[0041] By using the silver-coated resin particles 10 constructed as described above as in this embodiment, which contain titanium oxide in the range of 0.05% to 12.00% by mass, silver can be well plated on the surface of the resin particles 11, and the amount of Sn used in the catalytic treatment step S02 can be reduced. Then, by limiting the Sn content to 0.20% by mass or less, the peeling of the silver coating 12 under thermal cycling load can be suppressed.

[0042] In this embodiment, if the 5% compressive modulus (5% K value) of the silver-coated resin particles 10 is in the range of 0.2 GPa to 3.5 GPa, the silver-coated film can maintain its shape retention and mechanical strength while being sufficiently soft and easily deformable. Therefore, for example, a paste containing these silver-coated resin particles 10 as fillers can suppress the generation of cracks in the hardened paste.

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

[0044] In this embodiment, if the particle size of the silver-coated resin particles 10 is in the range of 2μm to 50μm, it can reduce the amount of expensive silver used and thus reduce costs, while also being used as a filler for forming pastes and the like that of fine patterns.

[0045] The paste containing fillers in this embodiment contains silver-coated resin particles 10 as fillers, thus exhibiting excellent thermal cycling resistance. Even in applications subjected to severe thermal cycling, it can be stably used as a conductive adhesive or thermally conductive material.

[0046] The present invention has been described above with respect to one embodiment of the invention, but the invention is not limited thereto and can be appropriately modified without departing from the technical concept of the invention. In this embodiment, it is described as applicable as a paste containing fillers (which is used when forming a bonding layer that bonds the circuit layer of a semiconductor device to the semiconductor element), but the present invention is not limited thereto and can also be used for other purposes. [Example]

[0047] The verification experiments conducted to confirm the effectiveness of the present invention will be described.

[0048] (Examples 1-5 of this invention, Comparative Examples 2 and 3) The resin particles shown in Table 1 were dispersed in ethanol solvent to obtain a slurry with a solid content of 5% by mass. Titanium isopropoxide was added to the slurry with a titanium dioxide concentration as shown in Table 1, and a very small amount of water was added to produce titanium dioxide-coated carbamate particles. After filtration and washing, the mixture is dispersed in water, and stannous chloride is added in the manner specified in Table 1. The mixture is stirred at 40°C for 1 hour and then filtered again. The resulting filter cake is dispersed in water to obtain resin particles with divalent tin ions adsorbed on their surface (resin particles after catalytic treatment). Subsequently, a silver coating was formed on the surface of the resin particles by electroless plating, with the Ag concentration being the value recorded in Table 1.

[0049] (Examples 6-8 of this invention, and Comparative Examples 4-6) The resin particles shown in Table 1 were mixed with titanium oxide particles with an average particle size of 200 nm, with the titanium oxide particle content being the values ​​recorded in Table 1, and then subjected to a planetary ball mill to allow the titanium oxide particles to adhere to the surface of the resin particles. The same operation as in Examples 1-5 of the present invention and Comparative Examples 2 and 3 was performed, in which the resin particles with titanium oxide particles attached to the surface were catalyzed and electroless plated to form a silver coating.

[0050] (Comparative Example 1) Carbamate particles (resin particles) with an average particle size of 15 μm were dispersed in water, and stannous chloride was added at a Sn concentration of 0.1% by mass. The mixture was stirred at 40°C for 1 hour and then filtered. The resulting filter cake was dispersed in water to obtain resin particles with divalent tin ions adsorbed on their surface (resin particles after catalytic treatment). Subsequently, a silver coating was formed on the surface of the resin particles by electroless plating with an Ag concentration of 45% by mass.

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

[0052] (5% compressive modulus of elasticity (5% K value) of silver-coated resin particles) First, a micro compression tester (Fischer Instruments, model: HM500) was used to perform a compression test on a single silver-coated resin particle using a flat indenter at a load change rate of 0.3 mN / s and a temperature of 20°C. The displacement and load at 5% compression relative to the major diameter of the silver-coated resin particle were measured. The starting point (zero point) of the displacement measurement was set as the point where the load applied to the silver-coated resin particle by the micro compression tester changed, rather than the point of contact between the micro compression tester and the silver-coated resin particle as perceived by the micro compression tester. Next, the measured displacement and load were substituted into (1) below to calculate the 5% compressive modulus (5% K value). The evaluation results are shown in Table 1.

[0053] Equation (1): 5% compressive modulus (5% K value) [GPa] = 3F / (2S3R)1 / 2 F: Load [N] of silver-coated resin particles when compressed by 5%. S: Displacement of silver-coated resin particles when compressed by 5% [mm] R: Radius of the silver-coated resin particles before compression [mm]

[0054] (Presence or absence of silver coating peeling after thermal cycling) Furthermore, in the silver-coated resin particles of Examples 1-8 and Comparative Examples 1-6 of the present invention, after undergoing a thermal cycling test from -20°C to 80°C, SEM observation was performed to confirm whether the silver coating layer had peeled off in the cross-section. The evaluation results are shown in Table 1. Also, Example 1 of the present invention...

[0055] (Volume resistivity of the coating) For the aforementioned silver-coated resin particles, a filler-containing paste with a filler content of 60 vol% on an epoxy resin substrate was prepared using a rotary mixer. This filler-containing paste was then used to form a coating film with a thickness of 50 μm. The volume resistivity of the coating film was measured using the four-point 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 Example 1 of the present invention was determined to be 0.5 GPa. In Example 1 of this invention, after a thermal cycling test from -20°C to 80°C, the cross-section of the silver-coated resin particles was observed using SEM. The observation results are shown in Figures 4A and 4B. Even after the thermal cycling test, no peeling of the silver coating was observed. The paste containing filler, which is prepared by using silver-coated resin particles containing Example 1 of the present invention as filler, has a film with a volume resistivity of 2.0 × 10⁻⁴ Ω·cm.

[0058] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Example 2 of the present invention was determined to be 1.9 GPa. In Example 2 of this invention, after a thermal cycling test from -20°C to 80°C, the cross-section of the silver-coated resin particles was observed using SEM. Even after the thermal cycling test, no peeling of the silver coating was detected. The paste containing filler, which is prepared by using silver-coated resin particles containing the silver-coated resin particles of Example 2 of the present invention as fillers, has a film with a volume resistivity of 1.0 × 10⁻⁴ Ω·cm.

[0059] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Example 3 of the present invention was determined to be 2.0 GPa. In Example 3 of this invention, after a thermal cycling test from -20°C to 80°C, the cross-section of the silver-coated resin particles was observed by SEM. Even after the thermal cycling test, no peeling of the silver coating was detected. The paste containing filler, which is prepared by using silver-coated resin particles from Example 3 of the present invention as fillers, has a film with a volume resistivity of 9.0 × 10⁻⁵ Ω·cm.

[0060] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Example 4 of the present invention was determined to be 0.4 GPa. In Example 4 of this invention, after a thermal cycling test from -20°C to 80°C, the cross-section of the silver-coated resin particles was observed using SEM. Even after the thermal cycling test, no peeling of the silver coating was detected. The paste containing filler, which is prepared by using silver-coated resin particles from Example 4 of the present invention as fillers, has a film with a volume resistivity of 1.0 × 10⁻³ Ω·cm.

[0061] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Example 5 of the present invention was determined to be 2.5 GPa. In Example 5 of this invention, after a thermal cycling test from -20°C to 80°C, the cross-section of the silver-coated resin particles was observed by SEM. Even after the thermal cycling test, no peeling of the silver coating was detected. The paste containing filler, which is prepared by using silver-coated resin particles from Example 5 of the present invention as fillers, has a film with a volume resistivity of 5.0 × 10⁻⁴ Ω·cm.

[0062] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Example 6 of the present invention was determined to be 0.3 GPa. In Example 6 of this invention, after a thermal cycling test from -20°C to 80°C, the cross-section of the silver-coated resin particles was observed using SEM. The observation results are shown in Figure 5. Even after the thermal cycling test, no peeling of the silver coating was detected. The paste containing filler, which is prepared by using silver-coated resin particles containing the silver-coated resin particles of Example 6 of the present invention as fillers, has a film with a volume resistivity of 2.0 × 10⁻⁴ Ω·cm.

[0063] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Example 7 of the present invention was determined to be 2.5 GPa. In Example 7 of this invention, after a thermal cycling test from -20°C to 80°C, the cross-section of the silver-coated resin particles was observed by SEM. Even after the thermal cycling test, no peeling of the silver coating was detected. The paste containing filler, which is prepared by using silver-coated resin particles containing the silver-coated resin particles of Example 7 of the present invention as fillers, has a film with a volume resistivity of 3.0 × 10⁻³ Ω·cm.

[0064] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Example 8 of the present invention was determined to be 0.7 GPa. In Example 8 of this invention, after a thermal cycling test from -20°C to 80°C, the cross-section of the silver-coated resin particles was observed by SEM. Even after the thermal cycling test, no peeling of the silver coating was detected. The paste containing filler, which is prepared by using silver-coated resin particles containing Example 8 of the present invention as filler, has a film with a volume resistivity of 1.0 × 10⁻³ Ω·cm.

[0065] The 5% compressive modulus (5% K value) of the silver-coated resin particles of Example 8 of the present invention was determined to be 0.7 GPa. In Example 8 of this invention, after a thermal cycling test from -20°C to 80°C, the cross-section of the silver-coated resin particles was observed by SEM. Even after the thermal cycling test, no peeling of the silver coating was detected. The paste containing filler, which is prepared by using silver-coated resin particles containing Example 8 of the present invention as filler, has a film with a volume resistivity of 1.0 × 10⁻³ Ω·cm.

[0066] The 5% compressive modulus (5% K value) of the silver-coated resin particles in Comparative Example 1 was determined to be 0.5 GPa. In Comparative Example 1, after a thermal cycling test from -20°C to 80°C, the cross-section of the silver-coated resin particles was observed using SEM. Delamination of the silver coating was confirmed after the thermal cycling test. The paste containing filler, which uses silver-coated resin particles from Comparative Example 1 as filler, forms a film with a volume resistivity of 2.0 × 10⁻³ Ω·cm.

[0067] The 5% compressive modulus (5% K value) of the silver-coated resin particles in Comparative Example 2 was determined to be 2.6 GPa. In Comparative Example 2, the silver-coated resin particles were subjected to a thermal cycling test from -20°C to 80°C, and the resulting cross-section was observed using SEM. The observation results are shown in Figures 6A and 6B. Delamination of the silver coating was confirmed after the thermal cycling test. The paste containing filler, which uses silver-coated resin particles from Comparative Example 2 as filler, forms a film with a volume resistivity of 1.0 × 10⁻¹ Ω·cm.

[0068] The 5% compressive modulus (5% K value) of the silver-coated resin particles in Comparative Example 3 was determined to be 3.9 GPa. In Comparative Example 3, the silver-coated resin particles were subjected to a thermal cycling test from -20°C to 80°C, and the cross-section was observed by SEM. After the thermal cycling test, peeling of the silver coating was confirmed. The paste containing filler, which uses silver-coated resin particles from Comparative Example 3 as filler, forms a film with a volume resistivity of 3.0 × 10⁻² Ω·cm.

[0069] The 5% compressive modulus (5% K value) of the silver-coated resin particles in Comparative Example 4 was determined to be 2.0 GPa. In Comparative Example 4, the silver-coated resin particles were subjected to a thermal cycling test from -20°C to 80°C, and the resulting cross-section was observed using SEM. The observation results are shown in Figure 7. Delamination of the silver coating was confirmed after the thermal cycling test. The paste containing filler, which was prepared by using silver-coated resin particles from Comparative Example 4 as fillers, produced a coating with a volume resistivity of 4.0 × 10⁻³ Ω·cm.

[0070] The 5% compressive modulus (5% K value) of the silver-coated resin particles in Comparative Example 5 was determined to be 2.8 GPa. In Comparative Example 5, the silver-coated resin particles were subjected to a thermal cycling test from -20°C to 80°C, and the cross-section was observed by SEM. After the thermal cycling test, peeling of the silver coating was confirmed. The paste containing filler, which uses silver-coated resin particles from Comparative Example 5 as filler, forms a film with a volume resistivity of 1.0 × 10⁻¹ Ω·cm.

[0071] The 5% compressive modulus (5% K value) of the silver-coated resin particles in Comparative Example 6 was determined to be 5.0 GPa. In Comparative Example 6, the silver-coated resin particles were subjected to a thermal cycling test from -20°C to 80°C, and the cross-section was observed by SEM. After the thermal cycling test, peeling of the silver coating was confirmed. The paste containing filler, which uses silver-coated resin particles from Comparative Example 6 as fillers, forms a coating with a volume resistivity of 1.0 × 10⁻² Ω·cm.

[0072] As can be confirmed from the above, the present invention can provide silver-coated resin particles with excellent adhesion to the silver coating and excellent heat cycle resistance, and a paste containing the 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 forming agents (ACF, ACP) used in liquid crystal displays, touch screens, etc., conductive pastes used in touch screens, conductive pastes or films for grain bonding, and TIM materials.

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

Claims

1. A silver-coated resin particle, characterized in that it comprises resin particles composed of a resin composition and a silver coating layer formed on the surface of the resin particles, wherein the silver-coated resin particles contain titanium oxide in a range of 0.05% to 12.00% by mass and Sn in a range of 0.05% to 0.20% by mass.

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

3. The silver-coated resin particles as described in claim 1, wherein, The aforementioned resin composition is selected from one or more of acrylic resin, styrene resin, phenolic resin, carbamate resin, and polyimide resin.

4. The silver-coated resin particles as described in claim 1, wherein, The particle size is between 2μm and 50μm.

5. A paste containing filler, characterized in that it comprises an adhesive resin and silver-coated resin particles as filler, as described in any one of claims 1 to 4.

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