JP2010236031A - Method for producing metal powder and solder paste using metal powder obtained by the method - Google Patents

Abstract

A metal powder suitable for use as a fine pitch solder powder and having a volume cumulative median diameter D ₅₀ in the range of 1 to ₅ μm can be recovered in a very high yield by a simple method.
A volume cumulative median diameter D ₅₀ is obtained by a reduction reaction by mixing a first aqueous solution containing at least one base metal cation as a main component and a second aqueous solution containing divalent chromium ions. A Y-shaped branch pipe composed of a main pipe and two branch pipes connected to the upper end of the main pipe so as to join the main pipe, and a Y-shaped branch. Using a reaction tube connected to the lower end of the main pipe of the pipe, the first aqueous solution is introduced from one branch pipe, and the second aqueous solution is introduced from the other branch pipe to the main pipe. This is characterized in that nuclei of the metal powder are generated, and the core of the metal powder generated by the reduction reaction is grown by passing the mixed solution of both aqueous solutions brought into contact from the main tube to the reaction tube.
[Selection] Figure 1

Description

The present invention is a metal having a volume cumulative median diameter (Median diameter; D ₅₀ ) in the range of 1 to ₅ μm, which is suitable for use as a fine pitch solder powder for a conductive paste used as a contact material of an electronic substrate. The present invention relates to a method for producing powder and a solder paste using metal powder obtained by the method.

  Solder used for joining electronic components has been made lead-free from the viewpoint of the environment, and at present, solder powder composed mainly of tin is used. As a method for obtaining a fine metal powder such as a solder powder, a method using an atomizing method such as a gas atomizing method or a rotating disk method, or a mechanical process such as a melt spinning method or a rotating electrode method is known. In the gas atomization method, after melting metal in an induction furnace or gas furnace, the molten metal is made to flow down from a nozzle at the bottom of a container called a tundish that stores molten metal that has melted the metal, and high pressure gas is sprayed from the surrounding area to pulverize it. Is the method. The centrifugal atomizing method, also called the rotating disk method, is a method in which a molten metal is dropped onto a rotating disk at high speed, and a shearing force is applied in a tangential direction to break and make a fine powder.

  On the other hand, the fine pitch of joining parts is progressing along with the miniaturization of electronic parts, and solder powder with a finer particle size is required. Therefore, the technology for fine pitch is being actively improved. Yes. For example, as a technique for improving the gas atomization method, a method for producing a metal fine powder is disclosed in which a molten metal in a gas state is ejected from a nozzle and a high-pressure gas is blown from the periphery of the nozzle (for example, a patent document). 1). In the method described in Patent Document 1, by introducing gas when the molten metal passes through the nozzle, the molten metal is already divided when the molten metal is discharged from the nozzle, and a smaller powder can be produced.

  Further, as a method for obtaining a fine metal powder different from the above method, it is disclosed that titanium trichloride is added to an aqueous solution containing a metal salt, and a metal powder or the like is produced using the reducing action of this titanium trichloride. (For example, see Patent Document 2). According to the method described in Patent Document 2, a high-purity fine powder having a small particle size can be produced safely and easily. When producing a fine powder, dust pollution does not occur and the cost is low. A fine powder can be produced.

  Further, a silver fine particle colloidal dispersion in which a mixed solution containing ferrous ions and citrate ions and an aqueous solution containing a silver salt are discharged from different nozzles, merged and mixed in the middle of the flow, and reacted in a natural flow. A method for producing a liquid is known (for example, see Patent Document 3). According to the method described in Patent Document 3, it is easy to control the particle size of the silver fine particles, and the productivity is excellent.

JP 2004-18956 A (Claim 1, paragraph [0014]) Japanese Patent No. 3018655 (Claim 1, paragraph [0007]) JP 2004-68072 A (Claim 1, paragraph [0009])

  However, in the method described in Patent Document 1, it is necessary to classify and collect the metal fine powder obtained by the atomizing method in order to obtain a fine powder having a fine pitch, so that the yield is very poor. There's a problem. In addition, a metal powder having a good yield of about 7 μm obtained by the atomization method has poor printability and cannot form minute bumps at a narrow pitch.

Moreover, although the fine powder can be obtained by the method using the high frequency in the method described in Patent Document 2, there is a problem that initial cost such as equipment cost is very high.
In the current economic situation, it is difficult to introduce a device with high initial cost such as a high frequency furnace. Both systems are also dangerous because they are manufactured at high temperatures.

  Furthermore, the method described in Patent Document 3 relates to the production of silver nanoparticles, but it has not been possible to obtain single micron-sized particles, and even if this method is applied to the production of solder powder, It is not possible to obtain solder powder suitable for fine pitch.

An object of the present invention is to recover a metal powder having a volume cumulative median diameter (Median diameter; D ₅₀ ) in the range of 1 to ₅ μm, which is suitable for use as a fine pitch solder powder, by a simple method with a very high yield. Another object of the present invention is to provide a method for producing metal powder and a solder paste using the metal powder obtained by the method.

According to a first aspect of the present invention, a reduction reaction is performed by mixing a first aqueous solution containing at least one base metal cation as a main component and a second aqueous solution containing divalent chromium ions. In a method for producing a metal powder having a diameter D ₅₀ of 1 to ₅ μm, a Y-shaped branch pipe composed of a main pipe and two branch pipes connected to the upper end of the main pipe so as to join the main pipe; Using a reaction tube connected to the lower end of the main pipe of the Y-shaped branch pipe, the first aqueous solution is introduced from one branch pipe of the Y-shaped branch pipe, and the second aqueous solution is introduced from the other branch pipe to the main pipe. Then, a reduction reaction is performed by bringing both aqueous solutions into contact with each other in the main pipe to generate metal powder nuclei, and a mixture of the both aqueous solutions in contact is passed from the main pipe to the reaction tube to thereby remove the metal powder nuclei generated by the reduction reaction. It is characterized by growing.

  The second aspect of the present invention is the invention based on the first aspect, wherein the base metal contained in the first aqueous solution is selected from the group consisting of Sn, Co, Bi, Ge, Ni and In. It is one type or two or more types of metals.

  A third aspect of the present invention is an invention based on the first aspect, further comprising a noble metal cation in the first aqueous solution, wherein the noble metal contained in the first aqueous solution contains Au, Ag and It is one or more metals selected from the group consisting of Cu.

  A fourth aspect of the present invention is an invention based on the first to third aspects, wherein the inner diameter of the main pipe and the branch pipe of the Y-shaped branch pipe is 5 to 30 mm, the inner diameter of the reaction tube is 5 to 80 mm, The length of the reaction tube is 0.2 to 20 m, and the total molar concentration of metal cations contained in the first aqueous solution and the molar concentration of divalent chromium ions contained in the second aqueous solution are each 0.1 to 2.0 mol / L, each flow rate of the first aqueous solution and the second aqueous solution is 0.05 to 2.0 L / min.

  A fifth aspect of the present invention is an invention based on the first to fourth aspects, wherein the first aqueous solution further includes a dispersant for suppressing aggregation of the metal powder.

A sixth aspect of the present invention is an invention based on the first to fifth aspects, and is characterized in that a volume cumulative median diameter D _{50 of the} obtained metal powder is 1 to 5 μm.

  A seventh aspect of the present invention is a solder paste obtained by mixing a metal powder obtained by a manufacturing method based on the first to sixth aspects and a solder flux into a paste.

  An eighth aspect of the present invention is an invention based on the seventh aspect, and is characterized by being used for mounting electronic components.

  The method for producing metal powder of the present invention uses a Y-shaped branch pipe composed of a main pipe and two branch pipes, and a reaction tube connected to the lower end of the main pipe of the Y-shaped branch pipe. A first aqueous solution containing at least one base metal cation as a main component from one branch pipe of the type branch pipe and a second aqueous solution containing divalent chromium ions from the other branch pipe are introduced into the main pipe, respectively. Then, a reduction reaction is performed by bringing both aqueous solutions into contact with each other in the main pipe to generate metal powder nuclei, and a mixture of the both aqueous solutions in contact is passed from the main pipe to the reaction tube to thereby remove the metal powder nuclei generated by the reduction reaction. It is characterized by growing.

Since the situation in which the reduction reaction is continuously performed in such a constant region and the reduction reaction time is controllable, the volume cumulative median diameter D ₅₀ suitable for use as a fine pitch solder powder is obtained. Metal powder in the range of 1 to 5 μm can be recovered with a high yield by a simple method.

It is the schematic of the apparatus used with the manufacturing method of this invention. It is a figure explaining the contact of the 1st aqueous solution and the 2nd aqueous solution in a Y-shaped branch pipe.

  Next, an embodiment for carrying out the present invention will be described with reference to the drawings.

The method for producing a metal powder according to the present invention includes a first aqueous solution containing at least one base metal cation as a main component and a second aqueous solution containing divalent chromium ions, thereby reducing the volume, and accumulating volume. A metal powder having a median diameter D ₅₀ of 1 to ₅ μm is produced.

  Examples of the base metal contained in the first aqueous solution include one or more metals selected from the group consisting of Sn, Co, Bi, Ge, Ni, and In. The first aqueous solution may further contain a noble metal cation. Examples of the noble metal contained in the first aqueous solution include one or more metals selected from the group consisting of Au, Ag, and Cu. The first aqueous solution preferably contains a dispersant that suppresses aggregation of the metal powder. Examples of the dispersant include polymer dispersants such as cellulose and polyvinylpyrrolidone (PVP). The first aqueous solution is prepared by adjusting a hydrochloric acid aqueous solution or sulfuric acid aqueous solution containing at least one base cation as a main component to pH 2 or less, preferably pH 0.5, and adding a dispersant.

  The divalent chromium ion contained in the second aqueous solution has a function as a reducing agent. Since the divalent chromium ions are unstable, the second aqueous solution is preferably prepared each time it is mixed with the first aqueous solution. Specifically, for example, a chromium chloride solution may be used by reducing chromium by bringing the second chromium chloride solution into contact with metallic zinc in a non-oxidizing atmosphere, preferably in a nitrogen gas atmosphere. The second chromium chloride solution is preferably adjusted to pH 0-2. This is because when the pH exceeds the upper limit value, a problem that trivalent chromium ions precipitate as hydroxides easily occurs. The divalent chromium ion in the second aqueous solution is prepared in the same capacity as the first aqueous solution by matching the molar concentration necessary for the reduction reaction with the molar concentration of the cation in the first aqueous solution.

  As shown in FIG. 1, the characteristic structure of the method for producing metal powder of the present invention includes a main pipe 11a and two branch pipes 11b and 11b connected to the upper end of the main pipe 11a so as to merge with the main pipe 11a. And a reaction tube 12 connected to the lower end of the main pipe 11 a of the Y-shaped branch pipe 11, and the first aqueous solution is supplied from one branch pipe 11 b of the Y-shaped branch pipe 11. Then, the second aqueous solution is introduced into the main pipe 11a from the other branch pipe 11b, both the aqueous solutions are brought into contact with each other in the main pipe 11a, a reduction reaction is performed, and a core of the metal powder is generated. By passing from the main pipe 11a to the reaction tube 12, the nucleus of the metal powder generated by the reduction reaction is grown.

The first aqueous solution and the second aqueous solution are continuously introduced from the branch pipe of the Y-shaped branch pipe, and both aqueous solutions are brought into contact with each other in the main pipe, thereby generating uniform metal particle nuclei, and subsequently mixing of both aqueous solutions. By filling the liquid from the main tube into the reaction tube without any gaps, the core of the metal powder is grown to a certain particle size. As a result, a metal powder having a volume cumulative median diameter D ₅₀ in the range of 1 to ₅ μm, which is suitable for use as a fine pitch solder powder, can be obtained. Further, by creating a situation where the introduced first aqueous solution and the second aqueous solution are brought into contact with each other and continuously undergo a reduction reaction in a certain region, as a result, the metal powder can be obtained in a simple method with a very high yield. It can be recovered.

  In the production method of the present invention, the reduction reaction time can be controlled by changing the inner diameter of the Y-shaped branch pipe, the inner diameter and length of the reaction tube, and the flow rate of the reaction solution. Can be changed.

  In addition, the production method of the present invention is a wet method, and both the aqueous solution preparation and the reduction reaction can be performed at a temperature of about room temperature, so that no special equipment that requires a large initial cost is required.

  Furthermore, since the reduction reaction proceeds in a limited region of the Y-shaped branch pipe 11 and the reaction tube 12 and ends, the first aqueous solution and the second aqueous solution are continuously introduced to produce metal powder. It is not necessary to change the various conditions when scaling up.

  In the metal powder manufacturing method of the present invention, a manufacturing apparatus 10 as shown in FIG. 1 is used. The manufacturing apparatus 10 includes a Y-shaped branch pipe 11, a reaction tube 12, and a recovery tank 13, one end of the reaction tube 12 is connected to the lower end of the main pipe 11 a of the Y-shaped branch pipe 11, and the other end of the reaction tube 12. Is connected to the upper part of the collection tank 13. The Y-shaped branch pipe 11 includes a main pipe 11a and two branch pipes 11b and 11b connected to the upper end of the main pipe 11a so as to join the main pipe 11a. The two branch pipes 11b and 11b of the Y-shaped branch pipe 11 are connected so as to merge with the main pipe 11a at an angle of 45 ° C., respectively, and the two branch pipes 11b and 11b are preferably the same length. . The main pipe 11a and the two branch pipes 11b and 11b have the same diameter. When the length of the reaction tube 12 is long, the reaction tube 12 may be used while being wound in a spiral shape. The collection tank 13 is preferably provided with a stirring means inside so that the metal powder contained in the slurry of the mixed solution collected after the reaction does not aggregate. Further, the inside of the manufacturing apparatus 10 is preferably in a non-oxidizing atmosphere. Specifically, the reduction reaction is preferably performed in an atmosphere into which nitrogen gas has been introduced.

  The first aqueous solution is introduced from one branch pipe 11b of the Y-shaped branch pipe 11 of the manufacturing apparatus 10 configured as described above, and the second aqueous solution is introduced from the other branch pipe 11b to the main pipe 11a. The first aqueous solution and the second aqueous solution are respectively introduced into both branch pipes 11b and 11b so as to have the same flow rate.

  As shown in FIG. 2, the first aqueous solution and the second aqueous solution introduced into the respective branch pipes 11b and 11b come into contact with each other at the joining main pipe 11a to form nuclei of metal particles. The nuclei of the metal particles formed in the mixed solution of both aqueous solutions that have come into contact grow to a certain particle size in the main tube 11a and the reaction tube 12. Returning to FIG. 1, the mixed solution of both aqueous solutions containing metal powder grown to a certain particle size in the main tube 11 a and the reaction tube 12 is sent to the recovery tank 13.

  In the production method of the present invention, the inner diameter of the main pipe 11a and the branch pipes 11b and 11b of the Y-shaped branch pipe 11 is 5 to 30 mm, the inner diameter of the reaction tube 12 is 5 to 80 mm, and the length of the reaction tube 12 is 0.2 to 0.2 mm. 20m, the total molar concentration of metal cations contained in the first aqueous solution and the molar concentration of divalent chromium ions contained in the second aqueous solution are 0.1 to 2.0 mol / L, respectively, of the first aqueous solution and the second aqueous solution. It is preferable that the metal powder is produced in accordance with the target particle size within a range of 0.05 to 2.0 L / min.

  The slurry-like mixed liquid containing the metal powder recovered in the recovery tank 13 is washed with water, substituted with alcohol, dried under reduced pressure, and further crushed using a sieve or the like, thereby obtaining a uniform particle size. A metal powder is obtained.

The metal powder obtained by the production method of the present invention has a volume cumulative median diameter D ₅₀ of 1 to ₅ μm and can be suitably used as a solder powder for fine pitch applications.

  The solder paste of the present invention is a paste obtained by mixing the metal powder obtained by the manufacturing method described above and a soldering flux. As the solder flux, a commercially available RA or RMA type flux can be used. The flux ratio is preferably 10 to 20% by mass. The mixture of the metal powder and the solder flux is crushed and kneaded by a universal kneader or the like to produce a solder paste. The obtained solder paste can be used for electronic components that are becoming finer pitches, such as packaging applications, organic ceramic substrates for ASIC (Application Specific Integrated Circuit), CPU (Central Processing Unit), GPU (Graphic Processing Unit), and chips. It can be suitably used for mounting a set organic substrate or the like.

  Next, examples of the present invention will be described in detail together with comparative examples.

<Example 1>
First, 1 L of hydrochloric acid aqueous solution adjusted to pH 0.5 each containing 113.83 g of stannous chloride (SnCl ₂ ) and 1.00 g of PVP (average molecular weight: 8000) as a dispersing agent was prepared. did. Further, a trivalent chromium aqueous solution in which 399.75 g of chromium chloride hexahydrate (CrCl ₃ .6H ₂ O) was made up to 1.0 L with ion exchange water was passed through a glass column packed with 540.00 g of zinc particles. 1 L of an aqueous solution containing divalent chromium ions obtained by liquefying was prepared and used as a second aqueous solution.

  Next, the first aqueous solution is introduced from one branch pipe of the Y-shaped branch pipe of the reactor shown in FIG. 1 and the second aqueous solution is introduced from the other branch pipe into the main pipe at a flow rate of 0.8 L / min. The two aqueous solutions are brought into contact with each other in the main pipe to produce a metal powder nucleus, and the mixture of the two aqueous solutions in contact with each other is passed from the main pipe to the reaction tube to grow the metal powder nucleus produced by the reduction reaction. By doing so, Sn powder was continuously synthesized. The Y-shaped branch pipe uses a main pipe and a branch pipe whose inner diameters are all 12 mm, the reaction tube uses a PFA tube having an inner diameter of 19 mm and a length of 10 m, the container used for the reaction, the Y-shaped branch pipe The reaction tube and the recovery tank after the reaction were all operated under an inert gas atmosphere by nitrogen gas replacement.

Next, the Sn powder in the mixed solution that flowed out from the reaction tube to the recovery tank was washed with a sufficient amount of ion-exchanged water, dried under reduced pressure, and then crushed using a sieve or the like. The amount of Sn powder finally obtained was 69.6 g. As a result of measuring the particle size distribution of this Sn powder, the volume cumulative median diameter D ₅₀ was 3.49 μm.

<Example 2>
First, pH 0 containing 113.83 g of stannous chloride (SnCl ₂ ), 1.35 g of copper chloride dihydrate (CuCl ₂ .2H ₂ O) and 1.00 g of PVP (average molecular weight: 8000) as a dispersant. 1 L of an aqueous hydrochloric acid solution adjusted to .5 was prepared and used as a first aqueous solution. Further, a trivalent chromium aqueous solution in which 399.75 g of chromium chloride hexahydrate (CrCl ₃ .6H ₂ O) was made up to 1.0 L with ion exchange water was passed through a glass column packed with 540.00 g of zinc particles. 1 L of an aqueous solution containing divalent chromium ions obtained by liquefying was prepared and used as a second aqueous solution.

  Next, the first aqueous solution was introduced from one branch pipe of the Y-shaped branch pipe of the reactor shown in FIG. 1 and the second aqueous solution was introduced from the other branch pipe into the main pipe at a flow rate of 0.4 L / min. The two aqueous solutions are brought into contact with each other in the main pipe to produce a metal powder nucleus, and the mixture of the two aqueous solutions in contact with each other is passed from the main pipe to the reaction tube to grow the metal powder nucleus produced by the reduction reaction. Thus, Sn—Cu powder was continuously synthesized. The Y-shaped branch pipe has a main pipe and a branch pipe with an inner diameter of 5 mm, and the reaction tube has a 15 mm inner diameter and a 5 m long PFA tube. The container used for the reaction, the Y-shaped branch pipe The reaction tube and the recovery tank after the reaction were all operated under an inert gas atmosphere by nitrogen gas replacement.

Next, the Sn—Cu powder in the mixed solution that flowed out from the reaction tube to the collection tank was washed with a sufficient amount of ion-exchanged water, dried under reduced pressure, and then crushed using a sieve or the like. The amount of Sn—Cu powder finally obtained was 70.5 g. The result of particle size distribution measurement for this Sn-Cu powder, the cumulative volume median diameter D ₅₀ was 1.41.

<Example 3>
First, as in Example 2, 113.83 g of stannous chloride (SnCl ₂ ), 1.35 g of copper chloride dihydrate (CuCl ₂ .2H ₂ O) and PVP (average molecular weight: 8000) as a dispersant. 1 L of hydrochloric acid aqueous solution adjusted to pH 0.5 containing 1.00 g) was prepared, and this was used as the first aqueous solution. Further, a trivalent chromium aqueous solution in which 399.75 g of chromium chloride hexahydrate (CrCl ₃ .6H ₂ O) was made up to 1.0 L with ion-exchanged water was passed through a glass column packed with 540.00 g of zinc particles. 1 L of an aqueous solution containing divalent chromium ions obtained by liquefying was prepared and used as a second aqueous solution.

  Next, the first aqueous solution is introduced from one branch pipe of the Y-shaped branch pipe of the reactor shown in FIG. 1 and the second aqueous solution is introduced from the other branch pipe into the main pipe at a flow rate of 0.8 L / min. The two aqueous solutions are brought into contact with each other in the main pipe to produce a metal powder nucleus, and the mixture of the two aqueous solutions in contact with each other is passed from the main pipe to the reaction tube to grow the metal powder nucleus produced by the reduction reaction. Thus, Sn—Cu powder was continuously synthesized. The Y-shaped branch pipe uses a main tube and a branch pipe whose inner diameter is 8 mm, and the reaction tube uses a PFA tube having an inner diameter of 19 mm and a length of 10 m. The container used for the reaction, the Y-shaped branch pipe The reaction tube and the recovery tank after the reaction were all operated under an inert gas atmosphere by nitrogen gas replacement.

Next, the Sn—Cu powder in the mixed solution that flowed out from the reaction tube to the collection tank was washed with a sufficient amount of ion-exchanged water, dried under reduced pressure, and then crushed using a sieve or the like. The amount of Sn—Cu powder finally obtained was 70.5 g. The result of particle size distribution measurement for this Sn-Cu powder, the cumulative volume median diameter D ₅₀ was 2.04Myuemu.

<Example 4>
First, pH 0 containing 1138.3 g of stannous chloride (SnCl ₂ ), 13.5 g of copper chloride dihydrate (CuCl ₂ .2H ₂ O), and 10.0 g of PVP (average molecular weight: 8000) as a dispersant. 10 L of an aqueous hydrochloric acid solution adjusted to .5 was prepared and used as a first aqueous solution. Further, a trivalent chromium aqueous solution in which 3997.5 g of chromium chloride hexahydrate (CrCl ₃ .6H ₂ O) was made up to 10.0 L with ion-exchanged water was passed through a glass column packed with 5400.0 g of zinc particles. 10 L of an aqueous solution containing divalent chromium ions obtained by liquefying was prepared and used as a second aqueous solution.

  Next, the first aqueous solution is introduced from one branch pipe of the Y-shaped branch pipe of the reactor shown in FIG. 1 and the second aqueous solution is introduced from the other branch pipe into the main pipe at a flow rate of 0.8 L / min. The two aqueous solutions are brought into contact with each other in the main pipe to produce a metal powder nucleus, and the mixture of the two aqueous solutions in contact with each other is passed from the main pipe to the reaction tube to grow the metal powder nucleus produced by the reduction reaction. Thus, Sn—Cu powder was continuously synthesized. The Y-shaped branch pipe uses a main tube and a branch pipe whose inner diameter is 8 mm, and the reaction tube uses a PFA tube having an inner diameter of 19 mm and a length of 10 m. The container used for the reaction, the Y-shaped branch pipe The reaction tube and the recovery tank after the reaction were all operated under an inert gas atmosphere by nitrogen gas replacement.

Next, the Sn—Cu powder in the mixed solution that flowed out from the reaction tube to the collection tank was washed with a sufficient amount of ion-exchanged water, dried under reduced pressure, and then crushed using a sieve or the like. The amount of Sn—Cu powder finally obtained was 669.5 g. The result of particle size distribution measurement for this Sn-Cu powder, the cumulative volume median diameter D ₅₀ was 2.18Myuemu.

<Example 5>
First, 113.83 g of stannous chloride (SnCl ₂ ), 16.55 g of chloroauric acid tetrahydrate (HAuCl ₄ .4H ₂ O), and 1.00 g of PVP (average molecular weight: 8000) as a dispersant are included. 1 L of a hydrochloric acid aqueous solution adjusted to pH 0.5 was prepared and used as a first aqueous solution. Further, a trivalent chromium aqueous solution in which 399.75 g of chromium chloride hexahydrate (CrCl ₃ .6H ₂ O) was made up to 1.0 L with ion exchange water was passed through a glass column packed with 540.00 g of zinc particles. 1 L of an aqueous solution containing divalent chromium ions obtained by liquefying was prepared and used as a second aqueous solution.

  Next, the first aqueous solution is introduced from one branch pipe of the Y-shaped branch pipe of the reactor shown in FIG. 1 and the second aqueous solution is introduced from the other branch pipe into the main pipe at a flow rate of 0.8 L / min. The two aqueous solutions are brought into contact with each other in the main pipe to produce a metal powder nucleus, and the mixture of the two aqueous solutions in contact with each other is passed from the main pipe to the reaction tube to grow the metal powder nucleus produced by the reduction reaction. Thus, Sn—Au powder was continuously synthesized. The Y-shaped branch pipe uses a main tube and a branch pipe whose inner diameter is 8 mm, and the reaction tube uses a PFA tube having an inner diameter of 19 mm and a length of 10 m. The container used for the reaction, the Y-shaped branch pipe The reaction tube and the recovery tank after the reaction were all operated under an inert gas atmosphere by nitrogen gas replacement.

Next, the Sn—Au powder in the mixed solution flowing out from the reaction tube to the recovery tank was washed with a sufficient amount of ion exchange water, dried under reduced pressure, and then crushed using a sieve or the like. The amount of Sn—Au powder finally obtained was 83.2 g. As a result of measuring the particle size distribution of the Sn—Au powder, the volume cumulative median diameter D ₅₀ was 2.63 μm.

<Example 6>
First, 113.83 g of stannous chloride (SnCl ₂ ), 31.952 g of cobalt chloride hexahydrate (CoCl ₂ .6H ₂ O), and pH 0 containing 1.00 g of PVP (average molecular weight: 8000) as a dispersant. 1 L of an aqueous hydrochloric acid solution adjusted to .5 was prepared and used as a first aqueous solution. Further, a trivalent chromium aqueous solution in which 399.75 g of chromium chloride hexahydrate (CrCl ₃ .6H ₂ O) was made up to 1.0 L with ion exchange water was passed through a glass column packed with 540.00 g of zinc particles. 1 L of an aqueous solution containing divalent chromium ions obtained by liquefying was prepared and used as a second aqueous solution.

  Next, the first aqueous solution was introduced from one branch pipe of the Y-shaped branch pipe of the reactor shown in FIG. 1 and the second aqueous solution was introduced from the other branch pipe into the main pipe at a flow rate of 0.4 L / min. The two aqueous solutions are brought into contact with each other in the main pipe to produce a metal powder nucleus, and the mixture of the two aqueous solutions in contact with each other is passed from the main pipe to the reaction tube to grow the metal powder nucleus produced by the reduction reaction. Thus, Sn—Co powder was continuously synthesized. The Y-shaped branch pipe uses a main pipe and a branch pipe whose inner diameters are all 8 mm, and the reaction tube uses a PFA tube with an inner diameter of 19 mm and a length of 15 m. The container used for the reaction, the Y-shaped branch pipe The reaction tube and the recovery tank after the reaction were all operated under an inert gas atmosphere by nitrogen gas replacement.

Next, the Sn—Co powder in the mixed solution flowing out from the reaction tube to the collection tank was washed with a sufficient amount of ion exchange water, dried under reduced pressure, and then crushed using a sieve or the like. The amount of Sn—Co powder finally obtained was 83.2 g. As a result of measuring the particle size distribution of the Sn—Co powder, the volume cumulative median diameter D ₅₀ was 3.18 μm.

<Example 7>
First, 128.86 g of stannous sulfate (SnSO ₄ ), 4.09 g of silver nitrate (AgNO ₃ ), 1.00 g of copper sulfate pentahydrate (CuSO ₄ .5H ₂ O), and PVP (average) 1 L of sulfuric acid aqueous solution adjusted to pH 0.5 containing 1.00 g of molecular weight: 8000) was prepared and used as the first aqueous solution. Further, a trivalent chromium aqueous solution in which 588.26 g of chromium sulfate (Cr ₂ (SO ₄ ) ₃ ) is made up to 1.0 L with ion exchange water is passed through a glass column filled with 540.00 g of zinc particles. 1 L of the aqueous solution containing divalent chromium ions obtained in 1 was prepared, and this was used as the second aqueous solution.

  Next, the first aqueous solution is introduced from one branch pipe of the Y-shaped branch pipe of the reactor shown in FIG. 1 and the second aqueous solution is introduced from the other branch pipe into the main pipe at a flow rate of 0.8 L / min. The two aqueous solutions are brought into contact with each other in the main pipe to produce a metal powder nucleus, and the mixture of the two aqueous solutions in contact with each other is passed from the main pipe to the reaction tube to grow the metal powder nucleus produced by the reduction reaction. By doing so, Sn-Ag-Cu powder was continuously synthesized. The Y-shaped branch pipe uses a main tube and a branch pipe whose inner diameter is 8 mm, and the reaction tube uses a PFA tube having an inner diameter of 19 mm and a length of 10 m. The container used for the reaction, the Y-shaped branch pipe The reaction tube and the recovery tank after the reaction were all operated under an inert gas atmosphere by nitrogen gas replacement.

Next, the Sn-Ag-Cu powder in the mixed solution discharged from the reaction tube to the recovery tank is washed with a sufficient amount of ion-exchanged water, dried under reduced pressure, and then crushed using a sieve or the like. It was. The amount of Sn—Ag—Cu powder finally obtained was 69.5 g. The result of particle size distribution measurement for this Sn-Ag-Cu powder, the cumulative volume median diameter D ₅₀ was 4.25 [mu] m.

<Comparative Example 1>
First, pH 0 containing 113.83 g of stannous chloride (SnCl ₂ ), 1.35 g of copper chloride dihydrate (CuCl ₂ .2H ₂ O) and 1.00 g of PVP (average molecular weight: 8000) as a dispersant. 1 L of an aqueous hydrochloric acid solution adjusted to .5 was prepared and used as a first aqueous solution. Further, a trivalent chromium aqueous solution in which 266.50 g of chromium chloride hexahydrate (CrCl ₃ .6H ₂ O) was made up to 1.0 L with ion exchange water was passed through a glass column packed with 540.00 g of zinc particles. 1 L of an aqueous solution containing divalent chromium ions obtained by liquefying was prepared and used as a second aqueous solution.

  Next, the first aqueous solution and the second aqueous solution are each poured at a flow rate of 0.5 L / min from the upper neck of a 2 L four-necked separable flask whose interior is inert with nitrogen gas, and contact mixing is performed by stirring. Then, a reduction reaction was performed to synthesize Sn—Cu powder.

After completion of the reaction, the Sn-Cu powder was washed with a sufficient amount of ion-exchanged water. However, it seems that aggregation occurred during the reaction or washing, and after drying under reduced pressure, it was crushed using a sieve. Finally, it passed through a sieve having an opening of 100 microns, and Sn-Cu powder obtained as a powder was 15.8 g. As a result of measuring the particle size distribution of the Sn—Cu powder obtained as a powder, the volume cumulative median diameter D ₅₀ was 16.76 μm.

<Comparative example 2>
First, it contains 5.69.15 g of stannous chloride (SnCl ₂ ), 6.75 g of copper chloride dihydrate (CuCl ₂ .2H ₂ O) ions, and 5.00 g of PVP (average molecular weight: 8000) as a dispersant. 5 L of hydrochloric acid aqueous solution adjusted to pH 0.5 was prepared, and this was used as the first aqueous solution. Further, a trivalent chromium aqueous solution in which 13332.50 g of chromium chloride hexahydrate (CrCl ₃ .6H ₂ O) was made up to 5.0 L with ion exchange water was passed through a glass column packed with 2700.00 g of zinc particles. 5 L of an aqueous solution containing divalent chromium ions obtained by liquefying was prepared and used as a second aqueous solution.

  Next, the first aqueous solution and the second aqueous solution are each poured at a flow rate of 0.8 L / min from the upper neck of a 10 L four-necked separable flask whose interior is inert with nitrogen gas, and contact mixing is performed by stirring. Then, a reduction reaction was performed to synthesize Sn—Cu powder.

After completion of the reaction, the Sn-Cu powder was washed with a sufficient amount of ion-exchanged water. However, it seems that aggregation occurred during the reaction or washing, and after drying under reduced pressure, it was crushed using a sieve. Finally, it passed through a sieve having an opening of 100 microns, and the Sn-Cu powder obtained as a powder was 85.9 g. As a result of measuring the particle size distribution of the Sn—Cu powder obtained as a powder, the volume cumulative median diameter D ₅₀ was 12.43 μm.

上記表１は、実施例１〜７及び比較例１，２の金属粉末の製造条件と得られた金属粉末の体積累積中位径Ｄ₅₀を示したものである。

Table 1 shows the cumulative volume median diameter D ₅₀ of the metal powder obtained with the manufacturing conditions of the metal powders of Examples 1 to 7 and Comparative Examples 1 and 2.

As is clear from Table 1, in Examples 1 to 7 using the production method of the present invention, the volume cumulative median diameter D ₅₀ was 1.41 to 4.25 μm. In contrast, in Comparative Examples 1 and 2, the volume cumulative median diameter D ₅₀ exceeds 10 μm, and by using the production method of the present invention, the volume cumulative median diameter D ₅₀ is in the range of 1 to ₅ μm. It was confirmed that the metal powder can be obtained by a simple method.

  Moreover, in Comparative Examples 1 and 2, since many agglomerates were produced, the amount obtained as a powder was small, and the yield was low, but in Examples 1 to 7, no agglomerates were produced, It was confirmed that the amount obtained as a powder was large and could be recovered with a very good yield.

In the metal powder production method of the present invention, a metal powder having a volume cumulative median diameter D ₅₀ in the range of 1 to ₅ μm, which is suitable for use as a fine pitch solder powder, can be recovered by a simple method with a very high yield. The obtained metal powder can be used as a solder powder for forming narrow pitch bumps.

DESCRIPTION OF SYMBOLS 10 Manufacturing apparatus 11 Y-shaped branch pipe 11a Main pipe 11b Branch pipe 12 Reaction tube 13 Recovery tank

Claims (8)

A volume cumulative median diameter (Median diameter; D ₅₀ ) is produced by a reduction reaction by mixing a first aqueous solution containing at least one base metal cation as a main component and a second aqueous solution containing divalent chromium ions. In a method of producing a metal powder of 1 to 5 μm,
A Y-shaped branch pipe composed of a main pipe and two branch pipes connected to the upper end of the main pipe so as to merge with the main pipe, and a reaction tube connected to the lower end of the main pipe of the Y-shaped branch pipe Use
The first aqueous solution is introduced from one branch pipe of the Y-shaped branch pipe and the second aqueous solution is introduced from the other branch pipe to the main pipe, and the two aqueous solutions are brought into contact with each other in the main pipe to perform a reduction reaction. The core of the metal powder,
A metal powder nucleus produced by the reduction reaction is grown by passing the contacted mixed solution of both aqueous solutions from the main tube to the reaction tube.   The manufacturing method according to claim 1, wherein the base metal contained in the first aqueous solution is one or more metals selected from the group consisting of Sn, Co, Bi, Ge, Ni, and In.   The first aqueous solution further contains a noble metal cation, and the noble metal contained in the first aqueous solution is one or more metals selected from the group consisting of Au, Ag and Cu. 1. The production method according to 1.   The inner diameter of the main and branch pipes of the Y-shaped branch pipe is 5 to 30 mm, the inner diameter of the reaction tube is 5 to 80 mm, the length of the reaction tube is 0.2 to 20 m, and the total of metal cations contained in the first aqueous solution The molar concentration and the molar concentration of divalent chromium ions contained in the second aqueous solution are 0.1 to 2.0 mol / L, respectively, and the respective flow rates of the first aqueous solution and the second aqueous solution are 0.05 to 2.0 L / L. The method according to any one of claims 1 to 3, wherein the production method is a minute.   The manufacturing method according to any one of claims 1 to 4, wherein the first aqueous solution further contains a dispersant for suppressing aggregation of the metal powder. The production method according to any one of claims 1 to 5, wherein a volume cumulative median diameter (Median diameter; D ₅₀ ) of the obtained metal powder is 1 to 5 µm.   A solder paste obtained by mixing the metal powder obtained by the manufacturing method according to claim 1 and a solder flux into a paste.   The solder paste according to claim 7, which is used for mounting electronic components.

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