Silver-coated resin particle mixed powder, method for producing silver-coated resin particle mixed powder, and filler-containing paste

Abstract

To provide a silver-coated resin particle mixed powder that allows formation of a filler-containing paste having superior conductivity and thermal conductivity while ensuring contact points among fillers.SOLUTION: A silver-coated resin particle mixed powder 1 comprises silver-coated resin particles 10 each having a silver coating layer 12 formed on the surface of a resin particle 11, and silver particles 15, wherein the CV value of the particle diameter of the silver particles 15 is 20% or less, and the ratio D2 / D1 of the average particle diameter D2 of the silver-coated resin particles 10 to the average particle diameter D1 of the silver particles 15 is in the range of 4 or more and 40 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mixed powder of silver-coated resin particles, a method for producing the mixed powder of silver-coated resin particles, and a filler-containing paste. [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] In the above-mentioned filler-containing paste, in order to further improve the electrical conductivity and heat conductivity of the cured paste, it is necessary to increase the number of contact points between the fillers, and therefore to pack the fillers at a high density. However, when the filler is packed at a high density, flexibility is reduced, and there is a risk of cracks occurring in the cured paste. In addition, because the silver-coated resin particles described above have a nearly spherical shape, there is a risk that the number of contact points will not increase efficiently even if the filler is packed at a high density.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a silver-coated resin particle mixed powder that can ensure contact points between fillers and can form a filler-containing paste with excellent electrical conductivity and heat conductivity, a method for producing the silver-coated resin particle mixed powder, and a filler-containing paste that includes this silver-coated resin particle mixed powder as a filler. [Means for solving the problem]

[0007] In order to solve the above problems, the present inventors conducted extensive research and discovered that by precipitating minute silver particles when forming a silver coating layer on the surface of resin particles, it is possible to disperse the minute silver particles between the silver-coated resin particles, thereby ensuring contact points between the silver-coated resin particles and the silver particles.

[0008] The present invention has been made based on the above-mentioned findings, and the silver-coated resin particle mixed powder of aspect 1 of the present invention is a silver-coated resin particle mixed powder having silver particles and silver-coated resin particles in which a silver coating layer is formed on the surface of the resin particles, characterized in that the CV value of the particle diameter of the silver particles is 20% or less, and the ratio D2 / D1 of the average particle diameter D2 of the silver-coated resin particles to the average particle diameter D1 of the silver particles is in the range of 4 or more and 40 or less.

[0009] According to the silver-coated resin particle mixed powder of the first aspect of the present invention, the CV value of the particle diameter of the silver particles is 20% or less, and therefore the silver particles have a uniform particle diameter. Furthermore, since the ratio D2 / D1 of the average particle diameter D2 of the silver-coated resin particles to the average particle diameter D1 of the silver particles is within the range of 4 or more and 40 or less, the silver particles can be dispersed among the silver-coated resin particles, making it possible to ensure contact points between the silver-coated resin particles and the silver particles.

[0010] The silver-coated resin particle mixed powder of aspect 2 of the present invention is characterized in that, in the silver-coated resin particle mixed powder of aspect 1 of the present invention, the ratio V2 / V1 of the volume V2 of the silver-coated resin particles to the volume V1 of the silver particles is in the range of 1 or more and 9 or less. According to the silver-coated resin particle mixed powder of Aspect 2 of the present invention, the ratio V2 / V1 of the volume V2 of the silver-coated resin particles to the volume V1 of the silver particles is within the range of 1 to 9, so that the silver particles can be sufficiently dispersed among the silver-coated resin particles, and contact points between the silver-coated resin particles and the silver particles can be secured. Note that the volume ratio here refers to the distribution ratio of silver-coated particles and silver particles among all particles, and does not refer to the volume ratio of individual silver-coated resin particles and silver particles.

[0011] The silver-coated resin particle mixed powder of aspect 3 of the present invention is characterized in that, in the silver-coated resin particle mixed powder of aspect 1 or aspect 2 of the present invention, the particle diameter of the resin particles is in the range of 0.8 μm or more and 30 μm or less. According to the silver-coated resin particle mixed powder of aspect 3 of the present invention, the particle diameter of the resin particles is within the range of 0.8 μm or more and 30 μm or less, thereby ensuring the flexibility of the silver-coated resin particles and preventing the silver-coated resin particles from becoming larger than necessary, allowing the silver-coated resin particles and silver particles to be sufficiently dispersed, and ensuring contact points between the silver-coated resin particles and silver particles.

[0012] The method for producing a silver-coated resin particle mixed powder of aspect 4 of the present invention is a method for producing a silver-coated resin particle mixed powder of any one of aspects 1 to 3 of the present invention, and is characterized by comprising: a slurry generation step of obtaining a slurry in which the resin particles are dispersed in water at a concentration of 5% by mass or more and 10% by mass or less; a first reduction step of adjusting the temperature of the slurry to a range of 10°C or more and 30°C or less, and simultaneously adding a silver salt, a complexing agent, a pH adjuster, and a first reducing agent dropwise over a period of 10 to 40 minutes; a first stirring step of stirring and maintaining the mixture for 5 to 15 minutes after the first reduction step; a second reduction step of adding a second reducing agent having a stronger reducing power for silver than the first reducing agent after the first stirring step; and a second stirring step of stirring and maintaining the mixture for 10 to 30 minutes after the second reduction step.

[0013] The method for producing a silver-coated resin particle mixed powder according to the fourth aspect of the present invention includes a first reduction step S in which a silver salt, a complexing agent, a pH adjuster, and a first reducing agent are simultaneously added dropwise, a first stirring step S in which the mixture is stirred and maintained for 5 to 15 minutes after the first reduction step, a second reduction step S in which a second reducing agent having a stronger reducing power for silver than the first reducing agent is added, and a second stirring step S in which the mixture is stirred and maintained for 10 to 30 minutes after the second reduction step. This allows the precipitation of silver particles with small and uniform particle sizes when a silver coating layer is formed on the surface of the resin particles. This allows the production of a silver-coated resin particle mixed powder according to any one of the first to third aspects of the present invention.

[0014] A filler-containing paste according to a fifth aspect of the present invention is characterized by containing a binder resin and the silver-coated resin particle mixed powder according to 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 the silver-coated resin particle mixed powder of any one of aspects 1 to 3 of the present invention, so that the number of contact points between the fillers can be sufficiently ensured, and the paste has particularly excellent electrical conductivity and heat conductivity. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a silver-coated resin particle mixed powder that can ensure contact points between fillers and can form a filler-containing paste that has excellent electrical conductivity and heat conductivity, a method for producing the silver-coated resin particle mixed powder, and a filler-containing paste that contains this silver-coated resin particle mixed powder as a filler. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic explanatory diagram of a mixed powder of silver-coated resin particles according to one embodiment of the present invention. [Figure 2] FIG. 1 is a flow diagram showing a method for producing a mixed powder of 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 filler-containing paste according to one embodiment of the present invention. [Figure 4] 1 is a photograph showing the results of SEM observation of the mixed powder of silver-coated resin particles of Example 1 in the Examples. [Figure 5] 1 is a photograph showing the results of SEM observation of the mixed powder of silver-coated resin particles of Comparative Example 1 in the Examples. [Figure 6] 1 is a photograph showing the results of SEM observation of the mixed powder of silver-coated resin particles of Comparative Example 2 in the Examples. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, a silver-coated resin particle mixed powder, a filler-containing paste, and a method for producing a silver-coated resin particle mixed powder according to embodiments of the present invention will be described 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 do not limit the present invention unless otherwise specified.

[0018] 1 shows a silver-coated resin particle mixed powder 1 according to one embodiment of the present invention. The silver-coated resin particle mixed powder 1 according to this embodiment includes silver-coated resin particles 10 and silver particles 15. The ratio D2 / D1 of the average particle diameter D2 of the silver-coated resin particles 10 to the average particle diameter D1 of the silver particles 15 is set to a range of 4 or more and 40 or less.

[0019] Furthermore, the CV value of the particle diameter of the silver particles 15 is set to 20% or less. The CV value is calculated from the average particle diameter D1 of the silver particles 15 and the standard deviation σ1 by the formula CV value = σ1 / D1 × 100(%). The average particle diameter D1 of the silver particles 15 is preferably within the range of 0.2 μm to 1.5 μm.

[0020] In the silver-coated resin particle mixed powder 1 of this embodiment, the ratio V2 / V1 of the volume V2 of the silver-coated resin particles 10 to the volume V1 of the silver particles 15 is preferably in the range of 1 or more and 9 or less.

[0021] The silver-coated resin particle 10 in this embodiment includes a resin particle 11 made of a resin composition and a silver coating layer 12 formed on the surface of the resin particle 11, as shown in FIG. In this embodiment, the particle diameter d of the resin particles 11 is preferably within the range of 0.8 μm to 30 μm.

[0022] In the silver-coated resin particles 10 of this embodiment, the resin composition constituting the resin particles 11 is preferably one or more selected from acrylic resin, styrene resin, phenolic resin, urethane resin, and polyimide resin. In the silver-coated resin particles 10 of this embodiment, the flexibility imparted thereto increases the interference effect against expansion and contraction, so it is more preferable to use urethane resin or acrylic resin, which are particularly excellent in flexibility.

[0023] The reasons for the above-mentioned definitions for the silver-coated resin particle mixed powder 1 of this embodiment will be explained below.

[0024] (Ratio D2 / D1 of average particle diameter D1 of silver particles 15 to average particle diameter D2 of silver-coated resin particles 10) The silver-coated resin particle mixed powder 1 of this embodiment is a mixture of silver-coated resin particles 10 and silver particles 15 with a small particle size. Here, if the ratio D2 / D1 of the average particle diameter D1 of the silver particles 15 to the average particle diameter D2 of the silver-coated resin particles 10 is less than 4, the difference between the average particle diameter D2 of the silver-coated resin particles 10 and the particle diameter D1 of the silver particles 15 is small, and the silver particles 15 cannot be dispersed between the silver-coated resin particles 10, and it may be impossible to ensure the number of contact points between the silver-coated resin particles 10 and the silver particles 15. On the other hand, if the ratio D2 / D1 of the average particle diameter D1 of the silver particles 15 to the average particle diameter D2 of the silver-coated resin particles 10 is greater than 9, even if the silver particles 15 are dispersed between the silver-coated resin particles 10, the silver particles 10 and the silver particles 15 will not be in sufficient contact with each other, and it may be impossible to ensure the number of contact points between the silver-coated resin particles 10 and the silver particles 15. For the above reasons, in the silver-coated resin particle mixed powder 1 of this embodiment, the ratio D2 / D1 of the average particle diameter D2 of the silver-coated resin particles 10 to the average particle diameter D1 of the silver particles 15 is set to be in the range of 4 or more and 9 or less.

[0025] The lower limit of the ratio D2 / D1 of the average particle diameter D2 of the silver-coated resin particles 10 to the average particle diameter D1 of the silver particles 15 is preferably 4 or more, and more preferably 15 or more. On the other hand, the upper limit of the ratio D2 / D1 of the average particle diameter D2 of the silver-coated resin particles 10 to the average particle diameter D1 of the silver particles 15 is preferably 40 or less, and more preferably 25 or less.

[0026] (CV value of particle size of silver particle 15) In the silver-coated resin particle mixed powder 1 of this embodiment, if the CV value of the particle diameter of the silver particles 15 exceeds 20%, the particle diameter variation of the silver particles 15 will become large, and the silver particles 15 will not be able to be dispersed between the silver-coated resin particles 10, and there is a risk that the number of contact points between the silver-coated resin particles 10 and the silver particles 15 will not be sufficient. For these reasons, in the silver-coated resin particle mixed powder 1 of this embodiment, the CV value of the particle diameter of the silver particles 15 is set to 20% or less. The CV value of the particle diameter of the silver particles 15 is preferably 15% or less, and more preferably 10% or less.

[0027] (Ratio V2 / V1 of the volume V1 of the silver particles 15 to the volume V2 of the silver-coated resin particles 10) In the silver-coated resin particle mixed powder 1 of this embodiment, when the ratio V2 / V1 of the volume V2 of the silver-coated resin particles 10 to the volume V1 of the silver particles 15 is within the range of 1 or more and 9 or less, the silver particles 15 can be reliably dispersed between the silver-coated resin particles 10, and the number of contact points between the silver-coated resin particles 10 and the silver particles 15 can be further ensured. The lower limit of the ratio V2 / V1 of the volume V2 of the silver-coated resin particles 10 to the volume V1 of the silver particles 15 is more preferably 3 or more, and even more preferably 5.5 or more. On the other hand, the upper limit of the ratio V2 / V1 of the volume V2 of the silver-coated resin particles 10 to the volume V1 of the silver particles 15 is more preferably 10 or less, and even more preferably 8 or less.

[0028] The ratio V2 / V1 of the volume V2 of the silver-coated resin particles 10 to the volume V1 of the silver particles 15 is calculated by the following method. (1) From the scanning electron microscope image, the total area of ​​all silver-coated particles and the total area of ​​all silver particles that appear in the image are added together. (2) The average particle size of the silver-coated resin particles, the average particle size of the silver particles, and the area ratios calculated in (1) are used to convert to a volume ratio, and the volume ratio is defined as V2 / V1.

[0029] Next, an example of a method for producing the silver-coated resin particle mixed powder 1 according to this embodiment will be described with reference to the flow chart of FIG.

[0030] (Slurry generation process S01) First, the resin particles 11 are dispersed in water (ion-exchanged water) to produce a slurry, in which the concentration of the resin particles 11 in the slurry is set to a range of 5% by mass to 10% by mass.

[0031] (First reduction step S02) Next, the temperature of the obtained slurry is adjusted to a range of 10° C. to 30° C., and a silver salt, a complexing agent, a pH adjuster, and a first reducing agent are simultaneously added dropwise over a period of 10 to 40 minutes. Here, the silver salt that can be used is silver nitrate or silver dissolved in nitric acid. As the complexing agent, salts such as ammonia, ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetate, nitrotriacetic acid, triethylenetetraamminehexaacetic acid, sodium thiosulfate, succinate, succinimide, citrate, or iodide salt can be used.

[0032] (First stirring step S03) In the first reduction step S02, the slurry to which the silver salt, complexing agent, pH adjuster, and first reducing agent have been simultaneously added dropwise is stirred and maintained for 5 to 15 minutes. The lower limit of the stirring time in the first stirring step S03 is preferably 7 minutes or more, and the upper limit is preferably 12 minutes or less.

[0033] (Second reduction step S04) After the first stirring step S03, a second reducing agent having a stronger reducing power for silver than the first reducing agent dropped in the first reducing step S02 is added. The first and second reducing agents may include formalin, glucose, imidazole, Rochelle salt (potassium sodium tartrate), hydrazine and its derivatives, hydroquinone, L-ascorbic acid, formic acid, etc. It is preferable to select the first and second reducing agents appropriately from among these, taking into consideration their reducing power for silver.

[0034] (Second stirring step S05) Then, in the second reduction step S04, the slurry to which the second reducing agent has been simultaneously added dropwise is stirred and maintained for 10 to 30 minutes. The lower limit of the stirring time in the second stirring step S05 is preferably 15 minutes or more, and the upper limit is preferably 25 minutes or less.

[0035] Through the above steps, silver is deposited on the surfaces of the resin particles 11 to form silver coating layers 12, and silver particles 15 with small particle diameter variations are also deposited. In this way, the silver-coated resin particle mixed powder 1 of this embodiment is produced.

[0036] The filler-containing paste of this embodiment contains a binder resin and, as a filler, the above-described silver-coated resin particle mixed powder 1. Note that the paste may contain a solvent and / or additives as needed. Furthermore, in order to obtain higher electrical and thermal conductivity, conductive fillers other than the silver-coated resin particle mixed powder 1 (hereinafter referred to as other conductive fillers) may be added. Examples of other conductive fillers include metal particles such as other silver powder, copper powder, and nickel powder, organic particles such as carbon, and conductive ceramic particles. Furthermore, it is more preferable to use not only spherical particles but also flake (flat) particles. The ratio of the added fillers can be set to silver-coated resin particle mixed powder 1:other conductive fillers = 5-95% by mass:95-5% by mass 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 particle mixed powder 1, and kneading them using a planetary mixer, a three-roll mill, or the like.

[0037] 3, the filler-containing paste of this embodiment forms a bonding layer 104 that bonds a circuit layer 102 of an insulating circuit board and a semiconductor element 103 in a semiconductor device 101. That is, the filler-containing paste of this embodiment is applied to the mounting surface of the circuit layer 102, and the semiconductor element 103 is laminated thereon and heated, thereby forming a bonding layer 104 made of a cured product of the filler-containing paste of this embodiment, and the circuit layer 102 and the semiconductor element 103 are bonded together.

[0038] Here, since the filler-containing paste of this embodiment contains the above-mentioned silver-coated resin particle mixed powder 1 as a filler, it has excellent electrical conductivity and thermal conductivity, and can electrically connect the semiconductor element 103 and the circuit layer 102, as well as efficiently dissipate heat generated by the semiconductor element 103 to the insulating circuit board side.

[0039] The silver-coated resin particle mixed powder 1 of this embodiment, configured as described above, contains silver-coated resin particles 10 and silver particles 15, and the CV value of the particle diameter of the silver particles 15 is 20% or less, so that the silver particles 15 have a uniform particle diameter. Furthermore, since the ratio D2 / D1 of the average particle diameter D2 of the silver-coated resin particles 10 to the average particle diameter D1 of the silver particles 15 is within the range of 4 or more and 40 or less, silver particles 15 with small particle diameter variations can be dispersed among the silver-coated resin particles 10, making it possible to ensure contact points between the silver-coated resin particles 10 and the silver particles 15.

[0040] In the silver-coated resin particle mixed powder 1 of this embodiment, when the ratio V2 / V1 of the volume V2 of the silver-coated resin particles 10 to the volume V1 of the silver particles 15 is within the range of 1 or more and 9 or less, the volume ratio of the silver particles 15 is appropriate, the silver particles 15 can be sufficiently dispersed between the silver-coated resin particles 10, and the contact points between the silver-coated resin particles 10 and the silver particles 15 can be sufficiently secured.

[0041] In the silver-coated resin particle mixed powder 1 of this embodiment, when the particle diameter of the resin particles 11 constituting the silver-coated resin particles 10 is within the range of 0.8 μm or more and 30 μm or less, the flexibility of the silver-coated resin particles 10 is ensured, the silver-coated resin particles 10 do not become larger than necessary, the silver-coated resin particles 10 and the silver particles 15 can be sufficiently dispersed, and the contact points between the silver-coated resin particles 10 and the silver particles 15 can be sufficiently secured.

[0042] The method for producing a silver-coated resin particle mixed powder according to this embodiment includes a first reduction step S02 in which a silver salt, a complexing agent, a pH adjuster, and a first reducing agent are simultaneously added dropwise, a first stirring step S03 in which the mixture is stirred and maintained for 5 to 15 minutes after the first reduction step S02, a second reduction step S04 in which a second reducing agent having a stronger reducing power for silver than the first reducing agent is added, and a second stirring step S05 in which the mixture is stirred and maintained for 10 to 30 minutes after the second reduction step S04. Therefore, when forming a silver coating layer 12 on the surface of resin particles 11, it is possible to precipitate silver particles 15 having small and uniform particle sizes. This allows the production of a silver-coated resin particle mixed powder according to aspect 1 or aspect 2 of the present invention.

[0043] According to the filler-containing paste of this embodiment, since the silver-coated resin particle mixed powder 1 of this embodiment is contained as the filler, a sufficient number of contact points between the fillers can be ensured, and the paste has particularly excellent electrical conductivity and heat conductivity.

[0044] 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]

[0045] A confirmation experiment conducted to confirm the effectiveness of the present invention will be described.

[0046] (Invention Examples 1-4, Comparative Examples 2-4) Resin particles having the materials and average particle diameters shown in Table 1 were dispersed in ion-exchanged water to obtain a slurry with a resin particle concentration of 5 mass %. While 300 mL of this slurry was maintained at 20° C., a silver solution consisting of 24 mL of silver salt (silver nitrate aqueous solution) and 24 mL of complexing agent (ammonia aqueous solution), 40 mL of pH adjuster (sodium hydroxide aqueous solution), and 10 mL of a first reducing agent shown in Table 1 were simultaneously added dropwise over a period of 20 minutes. Thereafter, the mixture was stirred for the stirring time shown in Table 1. Next, 6 mL of the second reducing agent shown in Table 1 was added to the slurry, which was then kept stirred for 10 minutes. In this manner, silver-coated resin particle mixed powders were produced for Invention Examples 1 to 4 and Comparative Examples 2 to 4. For the Invention Examples, the various reagents shown in Table 1 were mixed in amounts that matched the respective silver concentrations.

[0047] (Comparative Example 1) Resin particles having the materials and average particle diameters shown in Table 1 were dispersed in ion-exchanged water to obtain a slurry with a resin particle concentration of 5 mass %. 300 mL of this slurry was kept at 15° C., and 40 mL of a pH adjuster (aqueous sodium hydroxide solution) and 20 mL of a first reducing agent shown in Table 1 were added thereto, followed by stirring for 10 minutes. Next, a silver solution consisting of 15 mL of silver salt (silver nitrate aqueous solution) and 15 mL of complexing agent (ammonia aqueous solution) was simultaneously added dropwise over 20 minutes. In this manner, a mixed powder of silver-coated resin particles of Comparative Example 1 was produced.

[0048] The silver-coated resin particle mixed powders of Examples 1-4 and Comparative Examples 1-4 obtained as described above were subjected to SEM observation, and the average particle size D2 of the silver-coated resin particles, the average particle size D1 of the silver particles, the CV value of the silver particles, the ratio D2 / D1 of the average particle size D2 of the silver-coated resin particles to the average particle size D1 of the silver particles, and the ratio V2 / V1 of the volume V2 of the silver-coated resin particles to the volume V1 of the silver particles were evaluated. The evaluation results are shown in Table 2. The SEM observation results of Inventive Example 1 are shown in FIG. 4, Comparative Example 1 in FIG. 5, and Comparative Example 2 in FIG.

[0049] In addition, an epoxy resin-based filler-containing paste with a filler ratio of 50 vol% was prepared using the silver-coated resin particle mixed powders of Invention Examples 1-4 and Comparative Examples 1-4 in a rotation-revolution 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 2.

[0050] [Table 1]

[0051] [Table 2]

[0052] In Comparative Example 1, silver particles with small particle diameters were not sufficiently precipitated, as shown in Figure 5. In addition, the volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particle mixed powder of Comparative Example 1 was 1.0 x 10 -1 The resistance was Ω·cm.

[0053] In Comparative Example 2, as shown in Figure 6, silver particles adhered to the surfaces of silver-coated resin particles, and the CV value of the particle diameter of the silver particles was large at 30%. In addition, the volume resistivity of the coating film formed using the filler-containing paste containing the mixed powder of silver-coated resin particles of Comparative Example 2 was 1.0 × 10 -2 The resistance was Ω·cm.

[0054] In Comparative Example 3, the ratio D2 / D1 of the average particle diameter D2 of the silver-coated resin particles to the average particle diameter D1 of the silver particles was 3.00. The volume resistivity of the coating film formed using the filler-containing paste containing the mixed powder of silver-coated resin particles of Comparative Example 3 was 1.2 × 10 -3 The resistance was Ω·cm.

[0055] In Comparative Example 4, the ratio D2 / D1 of the average particle diameter D2 of the silver-coated resin particles to the average particle diameter D1 of the silver particles was 42.00. The volume resistivity of the coating film formed using the filler-containing paste containing the mixed powder of silver-coated resin particles of Comparative Example 4 was 2.0 × 10 -2 The resistance was Ω·cm.

[0056] In contrast, in Examples 1-4 of the present invention, the CV value of the particle diameter of the silver particles was 20% or less, and the ratio D2 / D1 of the average particle diameter D2 of the silver-coated resin particles to the average particle diameter D1 of the silver particles was within the range of 4 or more and 40 or less. Furthermore, the volume resistivity of the coating film formed using the filler-containing paste containing the silver-coated resin particle mixed powder of Inventive Example 1-4 was sufficiently low, confirming that it was possible to form a coating film with excellent conductivity.

[0057] As described above, it has been confirmed that the present invention can provide a silver-coated resin particle mixed powder that can ensure contact points between fillers and can form a filler-containing paste with excellent electrical conductivity and heat conductivity, a method for manufacturing a silver-coated resin particle mixed powder, and a filler-containing paste that contains this silver-coated resin particle mixed powder as a filler. [Industrial Applicability]

[0058] The silver-coated resin particle mixed powder, the method for producing the silver-coated resin particle mixed powder, and the filler-containing paste of the present invention can be used as an anisotropic conductive film former (ACF, ACP) used in liquid crystal displays, touch panels, etc., a conductive paste used in touch panels, etc., a conductive paste or film for die bonding, and a TIM material. [Explanation of symbols]

[0059] 1. Silver-coated resin particle mixed powder 10. Silver-coated resin particles 11 Resin particles 12 Silver coating layer 15 silver particles

Claims

1. A silver-coated resin particle mixed powder having silver particles and silver-coated resin particles in which a silver coating layer is formed on the surface of the resin particles, A silver-coated resin particle mixed powder characterized in that the CV value of the particle diameter of the silver particles is 20% or less, and the ratio D2 / D1 of the average particle diameter D2 of the silver-coated resin particles to the average particle diameter D1 of the silver particles is in the range of 4 or more and 40 or less.

2. 2. The silver-coated resin particle mixed powder according to claim 1, wherein the ratio V2 / V1 of the volume V2 of the silver-coated resin particles to the volume V1 of the silver particles is in the range of 1 or more and 9 or less.

3. 3. The silver-coated resin particle mixed powder according to claim 1, wherein the particle diameter of the resin particles is in the range of 0.8 μm to 30 μm.

4. A method for producing the silver-coated resin particle mixed powder according to claim 1 or 2, comprising the steps of: a slurry generation step of dispersing the resin particles in water at a concentration of 5% by mass or more and 10% by mass or less to obtain a slurry; a first reduction step in which the temperature of the slurry is adjusted to a range of 10°C to 30°C, and a silver salt, a complexing agent, a pH adjuster, and a first reducing agent are simultaneously added dropwise over a period of 10 to 40 minutes; a first stirring step of stirring and maintaining the mixture for 5 to 15 minutes after the first reduction step; a second reducing step of adding, after the first stirring step, a second reducing agent having a stronger reducing power for silver than the first reducing agent; a second stirring step of stirring and maintaining the mixture for 10 to 30 minutes after the second reduction step; 1. A method for producing a mixed powder of silver-coated resin particles, comprising:

5. A filler-containing paste comprising a binder resin and the silver-coated resin particle mixed powder according to claim 1 or 2 as a filler.

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