Conductive metal particle production method

Abstract

A method for preparing a third aqueous solution having a pH greater than 7 by mixing a first aqueous solution containing Ni and NaOH and a second aqueous solution containing P, and forming conductive metal particles having Ni as the group by generating a reduction precipitation reaction in the third aqueous solution, wherein the median diameter d50 of the conductive metal particles is prepared according to the concentration of NaOH in the third aqueous solution.

Description

Technology Field

[0001] This invention relates to a method for manufacturing conductive metal particles and conductive metal particles, and more specifically, to a method for manufacturing a reduction-precipitation type conductive metal particle based on Ni and to conductive metal particles. Background Technology

[0002] Conventionally, a reduction-precipitation type conductive metal particle having Ni as the base and a method for manufacturing the same are known. For example, Patent Document 1 discloses a reduction-precipitation type conductive metal particle having Ni as the base, comprising 1 to 15 mass% of P (phosphorus) and 0.01 to 18 mass% of Cu, and a method for manufacturing the same. Additionally, Patent Document 2 discloses a reduction-precipitation type conductive metal particle having Ni as the base, comprising 1 to 15 mass% of P, 0.01 to 18 mass% of Cu, and 0.05 to 10 mass% of Sn (tin), and a method for manufacturing the same.

[0003] The conductive metal particles of the reduction precipitation type having Ni as the group (hereinafter referred to as NiP particles) disclosed in Patent Documents 1 and 2 have the advantage of having good conductivity due to low volume resistivity. In addition, for the NiP particles produced by the reduction precipitation reaction, a nucleus for growth into a NiP particle (hereinafter referred to as a NiP nucleus) is generated in the initial stage of the reaction, and in the subsequent reaction, the NiP nucleus grows to a predetermined particle size and becomes a NiP particle having a predetermined median diameter. Therefore, if the growth of the NiP nucleus is appropriately controlled, it is possible to manufacture NiP particles with good sphericity, for example, 10 μm or less.

[0004] Here, regarding the reduction of NiP particles, Patent Document 1 describes that in an aqueous solution for the reduction and precipitation of NiP particles composed of a Ni salt containing Cu ions, increasing the molar ratio (Ni / Cu) of Ni ions to Cu ions tends to reduce the size of the NiP particles being reduced and precipitated, and the non-uniformity of the NiP particles' size tends to decrease. Additionally, Patent Document 2 describes that in an aqueous solution for the reduction and precipitation of NiP particles composed of a Ni salt containing Cu ions and Sn ions, decreasing the molar ratio (Ni / Sn) of Ni ions to Sn ions tends to reduce the size of the NiP particles being reduced and the non-uniformity of the NiP particles' size tends to decrease. Furthermore, the size of the NiP particles is interpreted as the median diameter (d50) in the particle size distribution curve. In addition, the non-uniformity of NiP particle size is interpreted as the dispersion ((d90-d10) / d50) in the particle size distribution curve, and the smaller the dispersion, the sharper the particle size distribution can be.

[0005] For conductive metal particles such as these NiP particles, there is a demand for further miniaturization and stabilization of supply in a wide range of applications, such as paste-like materials called anisotropic conductive films (ACF), anisotropic conductive pastes (ACP), or anisotropic conductive adhesives (ACAs), and connection methods such as flex-on-board (FOB) or flex-on-flex (FOF), accompanied by the recent demand for further miniaturization and high precision of electronic communication devices. Prior art literature

[0006] Japanese Patent Publication No. 5622127 Japanese Patent Publication No. 5327582 The problem to be solved

[0007] However, in the conductive particle adjustment method according to Patent Document 1 and Patent Document 2, in order to reduce the dispersion of NiP particles, a classification treatment process must be included, which is laborious, and in order to reduce the median diameter, expensive reagents must be used, which leads to excessively high manufacturing costs, and there was room for improvement.

[0008] The object of this invention is to provide a simple and inexpensive method for preparing the median diameter of conductive metal particles (NiP particles). means of solving the problem

[0009] The inventors of the present invention, in the method for manufacturing NiP particles disclosed in Patent Documents 1 and 2, comprehensively examined the composition of various aqueous solutions used for the reduction precipitation of NiP particles and the reduction precipitation conditions, and discovered the existence of a relatively strong correlation between the median diameter of NiP particles and the concentration of NaOH in the aqueous solution where the reduction precipitation reaction occurs, which had not been previously recognized. Furthermore, by confirming that the median diameter of NiP particles can be adjusted by the concentration of NaOH in the aqueous solution where the reduction precipitation reaction occurs, thereby solving the above problem, they were able to make the present invention.

[0010] The invention according to the method for manufacturing conductive metal particles comprises a method of preparing a third aqueous solution having a pH greater than 7 by mixing a first aqueous solution containing Ni (Ni ions) and NaOH with a second aqueous solution containing P (hypophosphorus ions), and forming a conductive metal particle having Ni as a group (Ni-based conductive metal particle) by causing a reduction precipitation reaction in the third aqueous solution, wherein the median diameter of the conductive metal particle is determined by the concentration of NaOH in the third aqueous solution.

[0011] In the manufacture of the conductive metal particles described above, preferably, the concentration of NaOH in the third aqueous solution is prepared so that the median diameter of the conductive metal particles is 10 μm or less.

[0012] In the manufacture of the conductive metal particles described above, preferably, the concentration of NaOH in the third aqueous solution is adjusted so that the dispersion of the conductive metal particles is 1.0 or less.

[0013] In the case of promoting the micronization of conductive metal particles by the invention according to the manufacturing method containing Ni(Ni ions) in the first aqueous solution described above, preferably, the concentration of NaOH in the third aqueous solution is 0.190 mol / L or higher and 0.230 mol / L or lower.

[0014] In the invention according to a manufacturing method comprising Ni (Ni ions) in the first aqueous solution described above, preferably, the first aqueous solution comprises Cu (Cu ions).

[0015] In the invention according to a manufacturing method comprising Ni(Ni ions) in the first aqueous solution described above, preferably, the first aqueous solution comprises Sn(Sn ions).

[0016] In the invention according to a manufacturing method comprising Ni (Ni ions), Cu (Cu ions), and Sn (Sn ions) in a first aqueous solution, preferably, the Sn / Cu (molar ratio) in the third aqueous solution is prepared to be less than 5.5. Effects of the invention

[0017] The present invention includes a simple method for preparing a median diameter of conductive metal particles (NiP particles), and includes a simple method for preparing conductive particles (NiP particles) having a median diameter selected from, for example, a range of 1.0 μm or more and 10 μm or less, and having a dispersion of, for example, 1.0 or less. Accordingly, it becomes possible to supply conductive metal particles having a median diameter selected from, for example, a range of 1.0 μm or more and 10 μm or less at a low cost and in a stable manner. Brief explanation of the drawing

[0018] Figure 1 is a diagram (graph) showing the relationship between the concentration of NaOH in the third aqueous solution and the d50 of the obtained NiP particles (NiP particle group) as experimental results. Figure 2 is a graph showing the concentration of NaOH in the third aqueous solution and the dispersion of the obtained NiP particles (NiP particle group) as experimental results. Figure 3 is an example of an observation (photograph) of NiP particles (NiP particle group) containing P and Ni as the base. Figure 4 is an example of an observation (photograph) of No. 5 NiP particles (NiP particle group) containing Ni, P, and Cu. Figure 5 is an example of an observation (photograph) of No. 3 NiP particles (NiP particle group), which are representative NiP particles (NiP particle group) containing Ni, P, Cu, and Sn. Specific details for implementing the invention

[0019] (Form for carrying out the invention)

[0020] Hereinafter, the method for manufacturing conductive metal particles and the conductive metal particles according to the present invention will be described in detail. Furthermore, the composition of the method for manufacturing conductive metal particles according to the present invention and the composition of the conductive metal particles are defined by the claims, and it is reasonable to interpret that all modifications within the meaning and scope equivalent to the claims are included. In addition, in the following description (including drawings), whether a single particle (one particle) or a collection of particles (particle group) is intended, the term "particle" is used. However, only when there is a need for special limitation, notations such as "single particle" or "particle group" may be used. Furthermore, for the sake of convenience, "Ni (Ni ion)," "P (hypophosphorus ion)," "Cu (Cu ion)," and "Sn (Sn ion)" according to the aqueous solution may be written as "Ni," "P," "Cu," and "Sn," respectively.

[0021] In addition, the median diameter according to the present invention is intended to be the median diameter obtainable based on a cumulative volume distribution curve and is denoted as "d50". In addition, the dispersion according to the present invention is intended to be the value of (d90 - d10) / d50 using d50, d10, and d90 obtainable based on the cumulative volume distribution curve. A particle group with a small dispersion exhibits a sharp particle size distribution. In addition, d10, d50 (median diameter), and d90 are the particle diameters when the cumulative volume in the cumulative volume distribution curve of the particle group is 10%, 50%, and 90%, respectively. In addition, unless otherwise noted, the above cumulative volume distribution curve is intended to be obtained using a measuring device employing the laser diffraction scattering method.

[0022] Method for manufacturing conductive metal particles

[0023] The method for manufacturing conductive metal particles according to the present invention involves mixing a first aqueous solution containing Ni (Ni ions) and NaOH with a second aqueous solution containing P (hypophosphorus ions) to prepare a third aqueous solution having a pH greater than 7, and inducing a reduction precipitation reaction in the third aqueous solution to form conductive metal particles having Ni as the group. Additionally, the median diameter of the conductive metal particles is determined by the concentration of NaOH in the third aqueous solution. By this manufacturing method, conductive metal particles (NiP particles) having Ni as the group and containing P can be manufactured. For example, by adjusting the concentration of NaOH in the third aqueous solution containing Ni and P, NiP particles having Ni as the group and containing P can be manufactured. An example of the NiP particles in this case is shown in FIG. 3. Since the surface of the obtained NiP particles tends to become hard when the third aqueous solution contains an appropriate amount of P, an improvement in the mechanical strength of the NiP particles can be expected.

[0024] In the manufacturing method according to the present invention, the first aqueous solution preferably contains Cu (Cu ions). Accordingly, NiP particles can be produced having a d50 corresponding to the concentration of NaOH in the third aqueous solution containing Ni, P, and Cu, with Ni as the group and containing P and Cu. An example of the NiP particles in this case is shown in FIG. 4. Since the conductivity of the obtained NiP particles tends to increase when the third aqueous solution contains an appropriate amount of Cu, an improvement effect in the conductivity of the NiP particles can be expected. In addition, when the third aqueous solution contains an appropriate amount of Cu, the dispersion of the obtained NiP particles tends to be suppressed to a small degree.

[0025] In the manufacturing method according to the present invention, the first aqueous solution preferably contains Sn (Sn ions). Accordingly, NiP particles containing Ni as a group and containing P and Sn can be produced, having a d50 corresponding to the concentration of NaOH in the third aqueous solution containing Ni, P, and Sn. Since the d50 of the obtained NiP particles tends to decrease when the third aqueous solution contains an appropriate amount of Sn, the effect of further miniaturizing the NiP particles can be expected. In addition, when the third aqueous solution contains an appropriate amount of Sn, the dispersion of the obtained NiP particles tends to be suppressed to a small degree.

[0026] In the manufacturing method according to the present invention, the first aqueous solution more preferably comprises Cu (Cu ions) and Sn (Sn ions). Accordingly, NiP particles can be manufactured having a d50 corresponding to the concentration of NaOH in the third aqueous solution comprising Ni, P, Cu, and Sn, with Ni as the group and comprising P, Cu, and Sn. An example of the NiP particles in this case is shown in FIG. 5. Since the d50 and dispersion of the obtained NiP particles tend to be more stable when the third aqueous solution contains an appropriate amount of Cu and Sn, the effect of further stabilizing the micronization of the NiP particles can be expected.

[0027] In this invention, the process of forming conductive metal particles having Ni as the group by generating a reduction precipitation reaction in a third aqueous solution is a process using an electroless reduction method. Hereinafter, this process is referred to as the "granulation process." Furthermore, for a detailed description of the reduction precipitation reaction (electroless reduction method) occurring in the third aqueous solution, please refer to Patent Documents 1 and 2.

[0028] However, based on the knowledge of Patent Documents 1 and 2, the inventors of the present invention investigated a simple method for preparing the median diameter of NiP particles with the aim of realizing technically more stable micronization of NiP particles and stabilizing the supply of NiP particles, and preferably, explored a simple method for preparing NiP particles having a predetermined median diameter and exhibiting a sharp particle size distribution.

[0029] As the first experiment, an experiment was conducted to increase the Ni / Cu (molar ratio) in the aqueous solution at the onset of reduction precipitation. The prepared aqueous solution was a nickel sulfate hexahydrate aqueous solution at 7 dm 3 (Hereinafter referred to as Solution A), an aqueous solution of copper sulfate pentahydrate at 0.5 dm 3 (Hereinafter referred to as Solution B), an aqueous solution of sodium tartrate trihydrate at a volume of 3 dm 3 (hereinafter referred to as Solution C), pH-prepared aqueous solution at 15 dm 3 , pH buffer aqueous solution at 3.5 dm 3 and, 16 dm of aqueous reducing agent solution 3Solution A is an aqueous solution containing Ni (Ni ions) with a concentration of 1.03 mol / L of nickel sulfate hexahydrate, with a pH of 5.3. Solution B is an aqueous solution containing Cu (Cu ions) with a concentration of 0.43 mol / L of copper sulfate pentahydrate, with a pH of 3.6. Solution C is an aqueous solution containing Sn (Sn ions) with a concentration of 0.55 mol / L of sodium tartrate trihydrate, with a pH of 12.0. The pH adjustment solution is an aqueous solution containing NaOH with a pH of 13 and a concentration of 0.685 mol / L of NaOH. This pH-prepared aqueous solution is added in accordance with the disclosure of Patent Documents 1 and 2, which prepares the aqueous solution at the start of reduction precipitation to be alkaline with a pH greater than 7. The pH buffer aqueous solution uses sodium acetate and is an aqueous solution with a pH of 9.0 and a sodium acetate concentration of 4.29 mol / L. The reducing agent aqueous solution uses sodium hypophosphite monohydrate and is an aqueous solution containing P (hypophosphite ion) with a pH of 6.2 and a sodium hypophosphite monohydrate concentration of 1.8 mol / L.

[0030] Next, solutions A, B, and C, the pH adjustment aqueous solution, and the pH buffer aqueous solution are mixed to obtain a mixed aqueous solution containing Ni (Ni ions), Cu (Cu ions), and Sn (Sn ions), exhibiting alkalinity with a pH of 9.3, at a rate of 29 dm 3 Manufactured. And, 29dm maintained at a water temperature of approximately 60℃ while performing bubbling stirring with nitrogen gas in the reaction vessel 3 For the mixed aqueous solution, 16dm maintained at a water temperature of approximately 60℃ under similar conditions 3An aqueous solution of a reducing agent was mixed to initiate reduction precipitation. At the start of this reduction precipitation, the aqueous solution in the stirred layer exhibited alkalinity with a pH of 9.3. As a result of this first experiment, the median diameter of the NiP particles decreased, but unlike the description in Patent Document 1, the dispersion of the NiP particles increased. In order to obtain NiP particles with a sharp particle size distribution by further reducing the dispersion of these NiP particles, the classification process must be repeated many times. However, as the number of steps in the classification process of NiP particles increases, the yield of NiP particles decreases significantly, leading to problems such as excessively high manufacturing costs.

[0031] In addition, as a second experiment, an experiment was conducted to reduce the Ni / Sn (molar ratio) in the aqueous solution at the onset of reduction precipitation. The prepared aqueous solution was 7 dm of Solution A, which was the same as in the first experiment. 3 , Solution B (concentration 0.58 mol / L, pH 3.7), prepared at a higher concentration than in the first experiment, at 0.5 dm 3 , Solution C (concentration 0.50 mol / L, pH 12.0) prepared at a lower concentration than in the first experiment was 3 dm 3 , 15 dm of the same pH-prepared aqueous solution as in the first experiment 3 , 3.5 dm of the same pH buffer aqueous solution as in the first experiment 3 and, 16 dm of the same reducing agent aqueous solution as in the first experiment 3 am.

[0032] Next, solutions A, B, and C, the pH adjustment aqueous solution, and the pH buffer aqueous solution are mixed to obtain a mixed aqueous solution containing Ni (Ni ions), Cu (Cu ions), and Sn (Sn ions), exhibiting alkalinity with a pH of 9.3, at a rate of 29 dm 3 Manufactured. And, 29dm maintained at a water temperature of approximately 60℃ while performing bubbling stirring with nitrogen gas in the reaction vessel 3 For the mixed aqueous solution, 16dm maintained at a water temperature of approximately 60℃ under similar conditions 3An aqueous solution of a reducing agent was mixed to initiate reduction precipitation. At the start of this reduction precipitation, the aqueous solution in the stirred layer exhibited alkalinity with a pH of 9.3. As a result of this second experiment, it was successful to reduce the median diameter of the NiP particles. However, reagents such as copper sulfate pentahydrate and sodium tartrate trihydrate are relatively expensive. Consequently, problems arose, such as excessively high manufacturing costs, in preparation methods using expensive reagents.

[0033] Unlike Patent Document 1 or Patent Document 2, in this invention, in the assembly process, the concentration of NaOH in the third aqueous solution is important, rather than the concentration of NaOH in the first aqueous solution. Conventionally, the operation of preparing various components constituting each aqueous solution in the first and second aqueous solutions within a predetermined range, and the operation of controlling the liquid temperature of the third aqueous solution that causes the reduction precipitation reaction, were easy and simple operations. Therefore, as disclosed in Patent Documents 1 and 2, the preparation of the d50 and dispersion of NiP particles was mainly carried out by preparing the concentration of Ni contained in the first aqueous solution and controlling the liquid temperature of the third aqueous solution within a narrow range (e.g., 70±1℃, see Patent Documents 1 and 2). In addition, when the first aqueous solution contained either Cu or Sn, or contained both Cu and Sn, the concentration of Cu relative to Ni (Ni / Cu (molar ratio)) and / or the concentration of Sn (Ni / Sn (molar ratio)) was prepared in addition to the concentration of Ni and the liquid temperature.

[0034] In such conventional preparation methods, the concentration of NaOH in the first aqueous solution was prepared for the purpose of making the third aqueous solution, which causes the reduction precipitation reaction, alkaline (pH > 7), as disclosed in Patent Documents 1 and 2. For example, Patent Documents 1 and 2 specify that the solution should be prepared to be alkaline, with a pH greater than 7 at the start of reduction precipitation (see claims), and then, in their examples, specifically disclose the pH of the mixed aqueous solution (corresponding to the first aqueous solution in this invention), but do not disclose the pH of the aqueous solution at the start of reduction precipitation (corresponding to the third aqueous solution in this invention). Furthermore, regarding the preparation of the pH of the aqueous solution at the start of reduction precipitation (corresponding to the third aqueous solution in this invention), Patent Documents 1 and 2 do not describe or suggest any purpose other than making the aqueous solution at the start of reduction precipitation alkaline (pH > 7). Therefore, preparing the pH at the start of reduction precipitation as alkaline and greater than 7 as disclosed in Patent Documents 1 and 2 is equivalent to preparing the pH of the first aqueous solution as greater than 7 in this invention. Furthermore, preparing the pH at the start of reduction precipitation as alkaline and greater than 7 as disclosed in Patent Documents 1 and 2 is not equivalent to adjusting the pH of the third aqueous solution in this invention.

[0035] In other words, in conventional adjustment methods, it was sufficient for the aqueous solution at the start of reduction precipitation to be at least alkaline (pH > 7), and it was common practice to adjust the concentration of NaOH that makes the first aqueous solution alkaline to a relatively high concentration.

[0036] The inventors of the present invention have discovered a relatively strong correlation between the d50 of NiP particles and the concentration of NaOH in the third aqueous solution, and thus have been able to devise a method of the present invention that adjusts the d50 of NiP particles by the "concentration of NaOH in the third aqueous solution," which was not previously considered important.

[0037] In this invention, the d50 of the NiP particles can be made smaller by having a higher concentration of NaOH in the third aqueous solution. When a reduction precipitation reaction is carried out in the third aqueous solution, the amount (number) of NiP nuclei generated in the initial stage of the reduction precipitation reaction can be increased by having a higher concentration of NaOH. The concentration of Ni (Ni ions) in the third aqueous solution decreases as the NiP nuclei generated in the initial stage of the reduction precipitation reaction grow. This decrease in the concentration of Ni (Ni ions) proceeds faster as the amount (number) of NiP nuclei generated increases. Therefore, as the number of NiP nuclei increases, the absolute amount of Ni (Ni ions) contributing to the growth of one NiP nucleus, that is, the formation of one NiP particle, is reduced, and the size (d50) of the finally obtained NiP particle is suppressed to be small.

[0038] Based on an approximate analytical recognition (second-order approximation) from experiments, for example, the d50 of NiP particles can be efficiently reduced to 10 μm or less by having a concentration of NaOH in the third aqueous solution of 0.19 mol / L or more (0.23 mol / L or less). Similarly, for example, the d50 of NiP particles can be efficiently reduced to 7 μm or less by having a concentration of NaOH in the third aqueous solution of 0.20 mol / L or more (0.23 mol / L or less). Similarly, for example, the d50 of NiP particles can be efficiently reduced to 4 μm or less by having a concentration of NaOH in the third aqueous solution of 0.21 mol / L or more (0.23 mol / L or less).

[0039] The inventors of the present invention were able to determine, through experimental approximation (second-order approximation), that the sensitivity of the d50 of NiP particles to the concentration of NaOH in the third aqueous solution is sufficiently high. For example, it was determined that as the concentration of NaOH in the third aqueous solution gradually increases, such as to 0.19 mol / L, 0.20 mol / L, and 0.21 mol / L, the d50 of the NiP particles decreases, such as to 10 μm, 7 μm, and 4 μm in correspondence. In other words, it was found that there is a relatively strong negative correlation between the concentration of NaOH in the third aqueous solution and the d50 of the NiP particles. Given that the sensitivity of the d50 of the NiP particles to the concentration of NaOH in the third aqueous solution is sufficiently high, it is considered desirable to adjust the concentration of NaOH (mol / L) in the third aqueous solution with high precision to at least the second decimal place and round the third decimal place to the nearest whole number. By utilizing the high-sensitivity negative correlation between the concentration of NaOH in the third aqueous solution and the d50 of the NiP particles, the minimum value of the NaOH concentration in the third aqueous solution required to achieve the desired d50 of the NiP particles can be estimated, thereby suppressing the use of excessive NaOH and allowing the small hardening of the NiP particles to be performed simply and efficiently.

[0040] In the above view, in the invention according to this manufacturing method, when preparing the d50 of NiP particles to be, for example, 10 μm or less, it is preferable that the concentration of NaOH in the third aqueous solution be 0.190 mol / L or higher and 0.230 mol / L or lower. If the concentration of NaOH in the third aqueous solution is 0.190 mol / L or higher, the d50 of the obtained NiP particles becomes smaller, and NiP particles with a d50 of 10 μm or less can be formed efficiently. Furthermore, if the concentration of NaOH in the third aqueous solution is less than 0.190 mol / L, the tendency for the d50 of the NiP particles to exceed 10 μm and grow larger becomes stronger. Additionally, if the concentration of NaOH in the third aqueous solution is 0.230 mol / L or lower, the effect of reducing the dispersion of the obtained NiP particles, for example, to 1.0 or less, can be expected. In addition, if the concentration of NaOH in the third aqueous solution exceeds 0.230 mol / L, the tendency for the d50 of the obtained NiP particles to become smaller is weakened.

[0041] In the manufacturing method according to the present invention, when the third aqueous solution contains both Cu (Cu ions) and Sn (Sn ions), it is preferable to prepare the Sn / Cu (molar ratio) in the third aqueous solution to be less than 5.5. If the Sn / Cu (molar ratio) in the third aqueous solution is prepared to be less than 5.5 (e.g., 1.60 or more and 5.25 or less), the dispersion of the obtained NiP particles tends to decrease. Therefore, the effect of efficiently promoting the formation of NiP particles with a dispersion of 1.0 or less can be expected. Furthermore, if the Sn / Cu (molar ratio) in the third aqueous solution is excessively large and prepared to be 5.5 or more, the influence on the reduction precipitation reaction becomes strong, so there is a risk that the d50 or dispersion of the NiP particles will become unstable. For example, if the Sn / Cu (molar ratio) in the third aqueous solution is prepared to be 7.5, the reduction precipitation reaction becomes unstable, and there is a concern that high-quality NiP particles may not be obtained. From this perspective, it is desirable to prepare the Sn / Cu (molar ratio) in the third aqueous solution to be reasonably smaller than 7.7 and to be less than 5.5.

[0042] In the above assembly process, the reduction precipitation reaction is carried out in a third aqueous solution mixed with the first aqueous solution and the second aqueous solution. Therefore, the pH of the third aqueous solution is prepared to be greater than 7 (e.g., 8 or more and 10 or less). If the pH of the third aqueous solution is alkaline and greater than 7, the reduction precipitation reaction proceeds rapidly, so NiP particles can be formed efficiently.

[0043] In the above assembly process, the liquid temperature of the third aqueous solution may affect the rate of progress of the reduction precipitation reaction, the d50 of the NiP particles, etc. For example, if one intends to form NiP particles with a d50 of 10 μm or less while rapidly proceeding with the reduction precipitation reaction, it is preferable to control the liquid temperature of the third aqueous solution in the range of 50°C or higher and 80°C or lower (preferably 50°C or higher and 75°C or lower, more preferably 50°C or higher and 70°C or lower). In addition, since the reduction precipitation reaction proceeds faster as the liquid temperature of the third aqueous solution increases, if one intends to further reduce the hardness of the NiP particles (e.g., d50 of 7 μm or less), it is preferable to control the liquid temperature of the third aqueous solution in a relatively low temperature range of 55°C or higher and 65°C or lower. In addition, if further microhardening (e.g., d50 of 5 μm or less) is desired, it is preferable to control the liquid temperature of the third aqueous solution in a lower temperature range of 55°C or higher and 60°C or lower. In this way, if the liquid temperature of the third aqueous solution is controlled in a lower temperature range (e.g., 55°C or higher and 65°C or lower), the dispersion of the obtained NiP particles can also be expected to be more stabilized.

[0044] In this invention, the first aqueous solution comprises Ni (Ni ions) and NaOH. The first aqueous solution comprising Ni and NaOH can be prepared by mixing an aqueous solution containing Ni with an aqueous solution of NaOH. The concentrations of Ni and NaOH in the first aqueous solution are prepared with sufficient consideration that the concentration of NaOH in the third aqueous solution, which is obtained by mixing with the second aqueous solution and has a pH greater than 7, is within a predetermined range. For example, when selecting the d50 of NiP particles in the range of 1 μm or more and 10 μm or less, it is preferable to prepare the concentrations of Ni and NaOH in the first aqueous solution with consideration that the concentration of NaOH in the third aqueous solution is in the range of 0.19 mol / L or more (0.23 mol / L or less).

[0045] The aqueous solution containing Ni (Ni ions) for constituting the first aqueous solution may be, for example, an aqueous solution of a Ni salt, and specifically, may be an aqueous solution of nickel (II) sulfate hexahydrate. Examples of Ni salts include nickel chloride (NiCl2), nickel sulfide (NiS), nickel sulfate (NiSO4), nickel nitrate (Ni(NO3)2) and nickel carbonate (NiCO3).

[0046] In this invention, the first aqueous solution preferably contains Cu (Cu ions) in addition to Ni (Ni ions) and NaOH. The first aqueous solution containing Ni, Cu, and NaOH can be prepared by mixing an aqueous solution containing Ni, an aqueous solution containing Cu, and an aqueous solution of NaOH. The concentrations of Ni, Cu, and NaOH in the first aqueous solution are prepared with sufficient consideration that the concentration of NaOH in the third aqueous solution, which is obtained by mixing with the second aqueous solution and has a pH greater than 7, is within a predetermined range. For example, when selecting the d50 of NiP particles in the range of 1 μm or more and 10 μm or less, it is preferable to prepare the concentrations of Ni, Cu, and NaOH in the first aqueous solution with consideration that the concentration of NaOH in the third aqueous solution is in the range of 0.19 mol / L or more (0.23 mol / L or less).

[0047] The aqueous solution containing Cu (Cu ions) for constituting the first aqueous solution is preferably, for example, an aqueous solution of a Cu salt, and specifically, an aqueous solution of copper(II) sulfate pentahydrate, etc.

[0048] In this invention, the first aqueous solution preferably contains Cu (Cu ions) and more preferably Sn (Sn ions) in addition to Ni (Ni ions) and NaOH. The first aqueous solution containing Ni, Cu, Sn, and NaOH can be prepared by mixing an aqueous solution containing Ni, an aqueous solution containing Cu, an aqueous solution containing Sn, and an aqueous solution of NaOH. The concentrations of Ni, Cu, Sn, and NaOH in the first aqueous solution are prepared with sufficient consideration that the concentration of NaOH in the third aqueous solution, which is obtained by mixing with the second aqueous solution and has a pH greater than 7, is within a predetermined range. For example, when selecting the d50 of NiP particles in the range of 1 μm or more and 10 μm or less, it is preferable to prepare the concentrations of Ni, Cu, Sn, and NaOH in the first aqueous solution with consideration that the concentration of NaOH in the third aqueous solution is in the range of 0.19 mol / L or more (0.23 mol / L or less).

[0049] Here, the concentration of NaOH in the first aqueous solution may be prepared by calculating the ratio (mol / L) of the NaOH solution in the third aqueous solution after mixing the first aqueous solution and the second aqueous solution, and based on the calculated value. Additionally, if the first aqueous solution contains Cu, the concentration of Cu in the first aqueous solution may be prepared by calculating the ratio (mol / L) of the solution containing Cu in the third aqueous solution or the Ni / Cu (molar ratio), and based on the calculated value. Additionally, if the first aqueous solution contains Cu and Sn, the concentrations of Cu and Sn in the first aqueous solution may be prepared by calculating the ratio (mol / L) of the solution containing Cu in the third aqueous solution or the Ni / Cu (molar ratio), and the ratio (mol / L) of the solution containing Sn in the third aqueous solution or the Ni / Sn (molar ratio), and based on the calculated values. In addition, Ni / Cu (molar ratio) and Ni / Sn (molar ratio) can be obtained from the calculated values ​​by determining the ratio of the aqueous solution containing Ni (mol / L), the ratio of the aqueous solution containing Cu (mol / L), and the ratio of the aqueous solution containing Sn (mol / L) in the third aqueous solution. Additionally, Sn / Cu (molar ratio) can be obtained by dividing Sn / Ni by Cu / Ni.

[0050] The aqueous solution containing Sn (Sn ions) for constituting the first aqueous solution is preferably, for example, an aqueous solution of a tin salt, and specifically, an aqueous solution of sodium tartrate trihydrate, etc.

[0051] In this invention, the first aqueous solution may be mixed with a pH buffer, for example, sodium acetate, disodium maleate, etc. By mixing the pH buffer into the first aqueous solution containing the strong base NaOH, an action that counteracts changes in pH occurs, so it is effective in maintaining the pH of the first aqueous solution at approximately constant levels.

[0052] In this invention, the second aqueous solution contains P (hypophosphorus ion). The second aqueous solution containing P is preferably an aqueous solution of a reducing agent such as phosphinic acid (H3PO2) containing P, and specifically, is preferably an aqueous solution such as sodium phosphinate. The concentration of P in the second aqueous solution is prepared by sufficiently considering that the concentration of NaOH in the third aqueous solution, which is obtained by mixing with the first aqueous solution and has a pH greater than 7, is within a predetermined range. For example, when selecting the d50 of NiP particles in the range of 1 μm or more and 10 μm or less, the concentration of P in the second aqueous solution may be prepared by considering that it is preferable for the concentration of NaOH in the third aqueous solution to be in the range of 0.19 mol / L or more (0.23 mol / L or less).

[0053] NiP particles (conductive metal particles) manufactured by applying this invention contain at least Ni and P. Furthermore, if the third aqueous solution causing the reduction precipitation reaction contains unavoidable impurities not intended to be contained, the NiP particles contain the unavoidable impurities not intended to be contained. For example, the NiP particles contain 1 mass% or more and 15 mass% or less of P, with the remainder consisting of Ni and unavoidable impurities. In particular, in the case of NiP particles having a d50 in the range of 1 μm or more and 10 μm or less, preferably, the dispersion is 1.0 or less, and the particles contain 5 mass% or more and 15 mass% or less of P, with the remainder consisting of Ni and unavoidable impurities. The reduction precipitation type NiP particles having Ni as the base material have excellent conductivity, and low cost and stable mass production become possible. In addition, NiP particles containing an appropriate amount of P have superior mechanical strength, such as hardness, compared to Ni particles not containing P.

[0054] In addition, when the first aqueous solution contains Cu (Cu ions), the NiP particles contain at least Ni, Cu, and P. In addition, when the third aqueous solution that causes the reduction precipitation reaction contains unavoidable impurities not intended to be contained, the NiP particles contain unavoidable impurities not intended to be contained. For example, the NiP particles contain 0.01 mass% or more and 18 mass% or less of Cu and 1 mass% or more and 15 mass% or less of P, with the remainder consisting of Ni and unavoidable impurities. In particular, for NiP particles having a d50 in the range of 1 μm or more and 10 μm or less, the dispersion is preferably 1.0 or less, and contains 3.20 mass% or more and 5.40 mass% or less of Cu and 5 mass% or more and 15 mass% or less of P, with the remainder consisting of Ni and unavoidable impurities. The conductivity of NiP particles containing Cu is improved compared to NiP particles not containing Cu.

[0055] In addition, if the first aqueous solution contains Sn (Sn ions), the NiP particles contain at least Ni, Sn, and P. In addition, if the third aqueous solution causing the reduction precipitation reaction contains unavoidable impurities not intended to be contained, the NiP particles contain unavoidable impurities not intended to be contained. For example, the NiP particles contain Sn exceeding 0 mass% and 10 mass% or less and P exceeding 1 mass% and 15 mass% or less, with the remainder consisting of Ni and unavoidable impurities. In particular, for NiP particles having a d50 in the range of 1 μm or more and 10 μm or less, preferably, the dispersion is 1.0 or less, and contains Sn exceeding 0 mass% and 1.30 mass% or less and P exceeding 5 mass% and 15 mass% or less, with the remainder consisting of Ni and unavoidable impurities.

[0056] In addition, when the first aqueous solution contains Cu (Cu ions) and Sn (Sn ions), the NiP particles contain at least Ni, Cu, Sn, and P. In addition, when the third aqueous solution that causes the reduction precipitation reaction contains unavoidable impurities not intended to be contained, the NiP particles contain unavoidable impurities not intended to be contained. For example, the NiP particles contain 0.01 mass% or more and 18 mass% or less of Cu, more than 0 mass% and 10 mass% or less of Sn, and 1 mass% or more and 15 mass% or less of P, with the remainder consisting of Ni and unavoidable impurities. In particular, for NiP particles having a d50 in the range of 1 μm or more and 10 μm or less, preferably, the dispersion is 1.0 or less and contains 3.20 mass% or more and 5.40 mass% or less of Cu, exceeding 0 mass% and containing 1.30 mass% or less of Sn and 5 mass% or more and 15 mass% or less of P, and the remainder consists of Ni and unavoidable impurities.

[0057] NiP particles (conductive metal particles) manufactured by applying this invention may have one or more conductive metal plating layers formed on their surface, such as an Au plating layer, a Cu plating layer, a Ni plating layer, or a Pd (palladium) plating layer. Since the conductive metal plating layer made of the above materials has a higher conductivity than the NiP particles, it is advantageous for improving conductivity and stabilizing current flow when the NiP particles come into contact with each other. In particular, since the Au plating layer is softer than the surface of the NiP particles, it is advantageous for stabilizing the contact state and stabilizing current flow when the NiP particles come into contact with each other.

[0058] Here, the applications of conductive metal particles and the required size and dispersion are supplemented. The size (e.g., d50) of conductive metal particles (e.g., NiP particles) is required arbitrarily depending on their application. Depending on the application, the d50 of NiP particles is required to be, for example, 10 μm or less, 7 μm or less, or 4 μm or less. NiP particles with a d50 of 10 μm or less are widely used for applications such as general flexible printed circuit boards (FPC). NiP particles with a d50 of 7 μm or less are used for applications such as FPCs that have a higher-precision conductive portion, such as those called fine pitch. While the d50 of NiP particles used for fine pitch applications is mainly in the range of 3 μm to 5 μm, a d50 in the range of 1 μm to 4 μm is required for the future. For this reason, NiP particles with a d50 of 4㎛ or less are expected to contribute further to fine pitch.

[0059] In addition, when manufacturing NiP particles having a d50 range of 1 μm or more and 10 μm or less, a d50 range of 1 μm or more and 7 μm or less, or a d50 range of 1 μm or more and 4 μm or less, applying this invention makes it possible to reduce the dispersion of the NiP particles to 1.0 or less. As the dispersion of the NiP particles decreases, the probability of forming a stable bonded structure through mutual contact of the NiP particles increases, thereby increasing the reliability of the electrical connection. On the other hand, as the dispersion of the NiP particles increases, it becomes possible to reduce the control precision of the reduction precipitation reaction, reduce the number of classification repetitions, and improve the yield, thereby reducing manufacturing costs, which makes it easier to realize a stable supply of NiP particles at a low price. Accordingly, the dispersion of NiP particles is preferably 0.7 or more and 1.0 or less, more preferably 0.8 or more and 1.0 or less, and even more preferably 0.9 or more and 1.0 or less, from the perspective of increasing the reliability of electrical connections while also realizing a low-cost and stable supply.

[0060] According to the invention based on the above-described manufacturing method, it is easy to prepare the d50 of the integrated volume distribution curve of the obtained NiP particles to be 10 μm or less, and it is easy to prepare the dispersion (d90 - d10) / d50 to be 1.0 or less. If the NiP particles obtained in this way are stably supplied to the market, the requirements for various applications such as ACF, ACP, ACAs, FOB, and FOF can be satisfied.

[0061] Hereinafter, experiments and results for verifying the effects of the method for manufacturing conductive metal particles (NiP particles) according to the present invention will be described with appropriate reference to the drawings.

[0062] <Preparation of the reaction tank>

[0063] A vessel (reactor) capable of withstanding a reduction precipitation reaction is prepared, equipped with a stirring device having rotating blades, a nitrogen gas supply device, and a liquid temperature measuring device. The inside of this reaction vessel is filled with nitrogen gas, and by continuously supplying nitrogen gas, the intrusion of the atmosphere into the reaction vessel is suppressed, and the discharge of the product gas generated by the reduction precipitation reaction is promoted. This supply of nitrogen gas is continued until the production of NiP particles is completed, while controlling the amount of nitrogen gas (flow rate) in a timely manner.

[0064] <Preparation of the First Aqueous Solution>

[0065] Pure water is added to the reaction vessel, and sodium hydroxide (NaOH) is added while stirring with a rotating blade. This stirring is continued while controlling the rotation speed of the rotating blade until the production of NiP particles is finished. Next, nickel sulfate (II) hexahydrate, which serves as a source of Ni (Ni ions), is added. Here, if necessary, copper sulfate (II) pentahydrate, which serves as a source of Cu (Cu ions), sodium acetate, which serves as a pH buffer, and sodium tartrate trihydrate, which serves as a source of Sn (Sn ions), may be added. Furthermore, the concentration of NaOH in the first aqueous solution is prepared by accurately calculating the mixing ratio of the individual substances constituting the first and second aqueous solutions so that when a third aqueous solution is obtained by mixing the first and second aqueous solutions, the concentration of NaOH in the third aqueous solution becomes a specific concentration value corresponding to the desired d50. Accordingly, the first aqueous solution is obtained.

[0066] <Preparation of the Second Solution>

[0067] A container different from the reaction vessel is prepared, and pure water is added. Sodium monohydrate phosphinate, which serves as a source of P (hypophosphorus ion), is added to this container. Additionally, the second aqueous solution is prepared by accurately calculating the mixing ratio of the individual substances constituting the second aqueous solution, taking into full consideration the mixing ratio of the individual substances constituting the first aqueous solution, so that when the third aqueous solution is obtained by mixing the first aqueous solution and the second aqueous solution, the concentration of NaOH in the third aqueous solution becomes a specific concentration value corresponding to the desired d50. Accordingly, the second aqueous solution is obtained.

[0068] <Third Solution>

[0069] A first aqueous solution containing Ni (Ni ions) and NaOH is heated using an external heater. The liquid temperature of the first aqueous solution is controlled to a temperature (reaction temperature) that causes a reduction precipitation reaction. Additionally, the first aqueous solution may contain Cu (Cu ions) as needed, and may also contain Sn (Sn ions) as needed. Furthermore, a second aqueous solution containing P (hypophosphorus ions) is heated using an external heater. The liquid temperature of the second aqueous solution is likewise controlled to a temperature (reaction temperature) that causes a reduction precipitation reaction. Subsequently, the second aqueous solution is added to a reaction vessel containing the first aqueous solution and stirred to form a mixed aqueous solution. Accordingly, a mixed aqueous solution of the first aqueous solution and the second aqueous solution, i.e., a third aqueous solution, is obtained. This third aqueous solution has a pH greater than 7 due to the NaOH contained in the first aqueous solution, and its concentration of NaOH becomes a specific concentration value due to the NaOH in the first aqueous solution being prepared to a specific concentration value. The liquid temperature of this third aqueous solution is continuously controlled at the reaction temperature using an external heater until the production of NiP particles is finished.

[0070] <NiP 입자의 형성>

[0071] In the third aqueous solution obtained in the above sequence and controlled at a reaction temperature, sodium monohydrate phosphinate contained in the second aqueous solution acts as a reducing agent, and a reduction precipitation reaction occurs. Through the reduction precipitation reaction generated in this third aqueous solution, a number of metal nuclei having Ni as a group are formed and eventually grow into a number of NiP particles. At this time, corresponding to the concentration value of NaOH in the third aqueous solution, NiP particles having a specific d50 can be formed smoothly and stably.

[0072] Based on the above sequence, the third aqueous solution was prepared under the conditions shown in Table 1, and each experiment was conducted. At this time, the third aqueous solution immediately after mixing the first aqueous solution and the second aqueous solution (at the start of reduction precipitation) exhibited alkalinity, and its pH was, for example, 7.6 in No. 2, 8.9 in No. 3, 9.1 in No. 4, 8.9 in No. 8, 9.3 in No. 9, and 8.1 in No. 12. As a result of each experiment, NiP particles shown in Table 2 were obtained. Figure 5 shown above is a representative observation (photograph) of the obtained NiP particles, specifically the NiP particle of No. 3 (d50 is 1.13 μm, dispersion is 0.91, P is 10.05 mass%, Cu is 4.04 mass%, Sn is 0.97 mass%, and the remainder is less than 0.01 mass%). In addition, the d50 and scatter plot of the NiP particles shown in Table 2 were obtained from an integrated volume distribution curve obtained from a measuring device employing the laser diffraction scattering method. The chemical composition (mass%) of the NiP particles shown in Table 2 was obtained by performing ICP analysis (Inductively Coupled Plasma analysis) using a solution in which a certain amount (0.1 g) of NiP particles were dissolved in aqua regia.

[0073]

[0074]

[0075] <NaOH의 농도와 d50과의 관계>

[0076] The graph shown in FIG. 1 illustrates the relationship between the concentration of NaOH (mol / L) of the third aqueous solution shown in Table 1 and the d50 of the NiP particles shown in Table 2. Furthermore, curve A shown in the figure is a second-order approximation curve (Y = 4655X) obtained from the total data shown in the figure, that is, from the multiple experimental results shown in Table 2 corresponding to the multiple experimental conditions shown in Table 1. 2 -2162X + 252.6, where X is the concentration of NaOH and Y is d50. Curve A, based on these multiple experiments, shows a strong negative correlation, indicating that the higher the concentration of NaOH in the third aqueous solution causing the reduction precipitation reaction, the smaller the d50 of the obtained NiP particles. Using this curve A, the d50 of the obtained NiP particles can be accurately predicted and adjusted based on the concentration of NaOH in the third aqueous solution. The d50 of the obtained NiP particles can be accurately adjusted based on the concentration of NaOH in the third aqueous solution taking into account this prediction result. That is, the concentration of NaOH in the third aqueous solution is adjusted so that the median diameter of the conductive metal particles is 10 μm or less.

[0077] Specifically, when the concentration of NaOH in the third aqueous solution was, for example, 0.190 mol / L, it can be predicted by the above curve A that the d50 of the obtained NiP particles is about 9.9 μm. Similarly, when the concentration of NaOH was 0.200 mol / L, 0.210 mol / L, 0.220 mol / L, and 0.230 mol / L, it can be predicted that the d50 of the obtained NiP particles is about 6.4 μm, about 3.9 μm, about 2.3 μm, and about 1.6 μm, respectively. In addition, by referring to curve A, it is easy to predict that when the concentration of NaOH in the third aqueous solution is 0.180 mol / L, the d50 of the resulting NiP particles will be approximately 14.3 μm. Therefore, when the concentration of NaOH is reduced, the risk of the d50 rapidly increasing to over 10 μm can be anticipated in advance. Furthermore, based on curve A, it can be predicted that when the concentration of NaOH in the third aqueous solution is 0.230 mol / L, the d50 of the resulting NiP particles will be 1.59, and when the concentration of NaOH is 0.240 mol / L, the d50 of the resulting NiP particles will be approximately 1.8 μm. In other words, it can be anticipated in advance that even if the concentration of NaOH is further increased, the effect of reducing the d50 will be weakened.

[0078] <Sn 함유와 d50과의 관계>

[0079] Here, from the graph shown in FIG. 1, for No. 1, No. 2, and No. 5, which do not contain Sn (Sn ions) in the third aqueous solution, it can be seen that as the concentration of NaOH in the third aqueous solution increases, it is clearly located on the upper side (+ side) of curve A. Accordingly, it can be inferred in advance that the d50 of the obtained NiP particles tends to increase. In addition, it can be seen that for No. 2 and No. 5, although the d50 is smaller than that of No. 1, it deviates significantly upward (+ side) from curve A. Accordingly, it can be inferred in advance that if one wishes to make the d50 of the NiP particles smaller, it is desirable to include an appropriate amount of Sn (Sn ions) in the third aqueous solution that causes the reduction precipitation reaction.

[0080] <NaOH의 농도와 산포도와의 관계>

[0081] The graph shown in FIG. 2 illustrates the relationship between the concentration of NaOH (mol / L) of the third aqueous solution shown in Table 1 and the dispersion of NiP particles shown in Table 2. Furthermore, curve B shown in the figure is a second-order approximation curve (Y = 354X) obtained from the total data shown in the figure, that is, from the multiple experimental results shown in Table 2 corresponding to the multiple experimental conditions shown in Table 1. 2-142.1X + 14.86, where X is the concentration of NaOH and Y is the dispersion. Curve B, based on these multiple experiments, shows a relatively strong positive correlation, indicating that the higher the concentration of NaOH in the third aqueous solution that causes the reduction precipitation reaction, the greater the dispersion of the obtained NiP particles. Using this curve B, the dispersion of the obtained NiP particles can be accurately predicted based on the concentration of NaOH in the third aqueous solution. The dispersion of the obtained NiP particles can be accurately adjusted based on the concentration of NaOH in the third aqueous solution taking into account this prediction result. That is, the concentration of NaOH in the third aqueous solution is adjusted so that the dispersion of the conductive metal particles becomes 1.0 or less.

[0082] Specifically, when the concentration of NaOH in the third aqueous solution was, for example, 0.190 mol / L, the dispersion of the obtained NiP particles can be predicted to be about 0.64 by the above curve B. Similarly, when the concentration of NaOH was 0.200 mol / L, 0.210 mol / L, 0.220 mol / L, and 0.230 mol / L, the dispersion of the obtained NiP particles can be predicted to be about 0.60, about 0.63, about 0.73, and about 0.90, respectively. In addition, when the concentration of NaOH in the third aqueous solution was 0.180 mol / L, the dispersion of the obtained NiP particles can be predicted to be about 0.75. In other words, by referring to curve B, it can be inferred in advance that increasing the concentration of NaOH from 0.180 mol / L suppresses dispersion, but increasing the concentration of NaOH further beyond a certain level weakens the effect of suppressing dispersion. Additionally, when the concentration of NaOH in the third aqueous solution was 0.240 mol / L, it can be predicted that the dispersion of the resulting NiP particles would be approximately 1.15, thus allowing for the inferred risk of the dispersion rapidly increasing beyond 1.0.

[0083] <Sn / Cu(몰비)와 산포도와의 관계>

[0084] Here, from the graph shown in FIG. 2, it can be seen that in the case of No. 4 and No. 9, where the Sn / Cu (molar ratio) of the third aqueous solution is large, it is clearly located on the upper side (+ side) of curve B. Accordingly, it is possible to obtain in advance the tendency for the dispersion of the obtained NiP particles to increase. In addition, it can be seen that although the dispersion of No. 9 is larger than that of No. 4, it is located on the upper side (+ side) of curve B more significantly than that of No. 4. Accordingly, it is possible to obtain in advance that it is desirable to appropriately prepare the Sn / Cu (molar ratio) of the third aqueous solution that causes the reduction precipitation reaction in order to reduce the dispersion of the NiP particles.

[0085] (Industrial Applicability)

[0086] This invention can be applied as a method for manufacturing conductive metal particles (NiP particles) for applications where a small diameter (e.g., d50 is 1 μm or more and 10 μm or less) is required, for example, as a method for manufacturing conductive metal particles (NiP particles) for forming an anisotropic conductive film, anisotropic conductive sheet, anisotropic conductive adhesive or anisotropic conductive paste, etc.

[0087] This application is based on Japanese Patent Application No. 2021-056511 filed on March 30, 2021, the contents of which are incorporated herein by reference. Explanation of the symbols

[0088] A : Curve (Quadratic Approximation Curve) B: Curve (Quadratic Approximation Curve)

Claims

Claim 1 A method for manufacturing conductive metal particles having Ni as the base by mixing a first aqueous solution containing Ni, NaOH, and Cu with a second aqueous solution containing P to prepare a third aqueous solution having a pH greater than 7, and generating a reduction precipitation reaction in the third aqueous solution to form conductive metal particles having Ni as the base, wherein the median diameter of the conductive metal particles is prepared by the concentration of NaOH in the third aqueous solution, the concentration of NaOH in the third aqueous solution is set to 0.190 mol / L or more and 0.230 mol / L or less, and the concentration of NaOH in the third aqueous solution is prepared such that the median diameter of the conductive metal particles is 1 μm or more and 10 μm or less. Claim 2 A method for manufacturing conductive metal particles according to claim 1, wherein the concentration of NaOH in the third aqueous solution is adjusted so that the dispersion of the conductive metal particles is 1.0 or less. Claim 3 A method for manufacturing conductive metal particles according to claim 1 or 2, wherein the first aqueous solution comprises Sn. Claim 4 A method for manufacturing conductive metal particles according to claim 3, wherein the Sn / Cu (molar ratio) in the third aqueous solution is prepared to be less than 5.

5. Claim 5 delete Claim 6 delete Claim 7 delete

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