A method for preparing ultrafine spherical metal powder based on jet flow injection

Abstract

The application relates to a method for preparing superfine spherical metal powder based on a jet injection method, and belongs to the technical field of metal spherical powder preparation. When an organic medium is high-speed sprayed out through a nozzle of a jet pump, a vacuum or negative pressure is formed at a suction pipe communication position of the jet pump; molten liquid metal is sucked into a suction chamber of the jet pump through the suction pipe; the molten liquid metal and the organic medium are mixed in a throat pipe section of a jet pipe; the molten liquid metal is broken into small metal liquid drops at the nozzle and forms spherical metal liquid drops through the surface tension of the organic medium; meanwhile, momentum exchange is carried out to increase the kinetic energy of the small metal liquid drops to be transported; the kinetic energy is converted into pressure energy through a diffusion pipe of the jet pipe to enter the organic medium in a gradient temperature field in a collector; the spherical metal liquid drops slowly descend and condense into spherical metal micro powder in the organic medium in the gradient temperature field; solid-liquid separation is carried out; the solid is washed and dried to obtain superfine spherical metal powder with a preset particle size.

Description

Technical Field

[0001] The invention relates to a method for preparing ultrafine spherical metal powder based on a jet injection method, and belongs to the technical field of metal spherical powder preparation. Background Art

[0002] The rise of lead-free solder, and particularly the rapid development of electronic packaging and semiconductor integrated circuits, has driven the development of metal powders, resulting in increasingly stringent requirements for metal powder quality (sphericity, powder particle size, particle size distribution range, and oxygen content). In particular, in ball grid array packaging, solder paste, and integrated circuits, the density of electronic components on circuit boards is increasing, while their size is shrinking. Chips are also moving towards miniaturization and diversification. High-quality spherical metal powders are a key research direction in this field. However, the current domestic production of fine spherical metal powders faces challenges such as high cost, difficulty, and low product performance. Therefore, to address the issue of reliance on imported high-quality spherical powders, research on methods for preparing and manufacturing high-quality fine spherical metal powders is of great significance.

[0003] Currently, the three main preparation methods used are atomization, chemical reduction, and mechanical alloying. Atomization is the most common method, including water atomization, gas atomization, centrifugal atomization, and solid atomization. Although atomization is highly efficient, the powder size is large and the distribution range is wide. Mechanical alloying is cost-effective, but the resulting powder has the poorest sphericity. Chemical reduction can produce nano-scale spherical metal powders, but the reagents involved in the preparation process are relatively complex, and this method has mainly remained in the experimental stage and has not yet been industrialized. Summary of the Invention

[0004] To address the existing problems in preparing ultrafine spherical metal powders, the present invention proposes a method for preparing ultrafine spherical metal powders based on a jet injection method. Specifically, a jet pump is used to drive a high-speed flowing organic medium to create a vacuum or negative pressure at the inlet of the jet pump's suction chamber. This causes molten metal to be drawn into the high-temperature organic medium by the negative pressure. The molten metal is then broken into tiny metal droplets at the nozzle. The surface tension of the organic medium forms spherical droplets, which then condense and form within a collector at the end of the injection process. The metal powder produced by this method exhibits excellent dispersibility, uniform particle size distribution, and low oxygen content after solidification, significantly improving the product yield compared to the aerosol method.

[0005] A method for preparing ultrafine spherical metal powder based on a jet injection method, wherein the preparation is performed using a jet injection device, the jet injection device comprising a first container, a second container, a jet pump, and a collector. The first container is filled with an organic medium, the second container is filled with a metal melt, and the collector is filled with an organic medium with a gradient temperature field, wherein the gradient temperature field is a temperature field that changes uniformly from high temperature to low temperature in a vertical direction. The bottom outlet of the first container is connected to the liquid inlet end of the nozzle of the jet pump through a liquid supply pipe, the metal melt outlet of the second container is connected to the suction chamber of the jet pump through a suction pipe, and the nozzle of the jet pump is connected to the top inlet of the collector through the injection pipe.

[0006] The specific steps are as follows:

[0007] (1) The organic medium is filled into a first container and a collector respectively, and the metal is added into a second container and heated and smelted to form a uniform melt;

[0008] (2) Selecting a nozzle size of 0.01 mm to 0.1 mm for the jet pump, setting the jet velocity of the organic medium of the jet pump to 10 to 30 m / s, and setting the gradient temperature field height of the organic medium to 50 to 100 cm, wherein the gradient temperature field is a temperature field that changes uniformly from high temperature to low temperature in the vertical direction;

[0009] (3) The organic medium in the first container is heated to a preset temperature, and the organic medium in the collector is heated to form a preset gradient temperature field. When the organic medium in the first container is ejected at a high speed through the nozzle of the jet pump, a vacuum or negative pressure is formed at the connection point of the suction pipe of the jet pump because the gas is swept away by the jet. The molten liquid metal is sucked into the suction chamber of the jet pump through the suction pipe. The molten liquid metal and the organic medium are mixed in the throat section of the injection pipe, and the molten liquid metal is broken into tiny metal droplets at the nozzle and formed into spherical micro-metal droplets through the surface tension of the organic medium. At the same time, momentum exchange is performed to increase the kinetic energy of the transported tiny metal droplets. The kinetic energy is then converted into pressure energy through the diffusion tube of the injection pipe and enters the organic medium with a gradient temperature field in the collector. The spherical micro-metal droplets slowly descend in the organic medium with a gradient temperature field and condense into spherical metal micro-powders. The solid and liquid are separated, and the solid is washed and dried to obtain ultrafine spherical metal powder with a preset particle size.

[0010] The metal in step (1) is a single metal, a binary alloy, a ternary alloy, a quaternary alloy or a high entropy alloy, and the melting point of the metal is 50-300°C.

[0011] Preferably, the metal element is indium or tin, the binary alloy is indium tin, tin bismuth, tin-lead, tin-silver or tin-copper alloy, the ternary alloy is tin-silver-copper, gallium-indium-tin, tin-silver-bismuth or tin-bismuth-copper alloy, the quaternary alloy is GaInSnBi, and the high entropy alloy is gallium-indium-tin-bismuth-zinc and gallium-indium-tin-bismuth-zinc-lead, etc.

[0012] The boiling point of the organic medium is 30-100°C higher than the melting point of the metal. The preset temperature of the organic medium in the first container is 20-50°C higher than the melting point of the metal. The starting end temperature of the gradient temperature field is 10-20°C higher than the melting point of the metal, and the end temperature is 10-30°C lower than the melting point.

[0013] The organic medium is ethers, alcohols or lipids; preferably, the organic medium is mineral oil N500 or polyalphaolefin.

[0014] The beneficial effects of the present invention are:

[0015] (1) The present invention utilizes a jet pump to drive a high-speed flowing organic medium to generate a vacuum or negative pressure at the inlet of the suction chamber of the jet pump. The molten liquid metal is sucked into the suction chamber of the jet pump through the suction pipe and mixed with the high-temperature organic medium. Under the action of the nozzle spray, the molten liquid metal is broken into tiny metal droplets at the nozzle and forms spherical micro-metal droplets through the surface tension of the organic medium. The spherical micro-metal droplets slowly descend and condense into spherical metal micro-powders in the organic medium with a gradient temperature field; the dispersed tiny liquid metal droplets are formed under the protection of the organic medium. During the process, due to the non-uniform dispersion path, the descending forming paths do not overlap, and it is not easy to form a tail-end, thereby ensuring the monodisperse performance of the metal spherical particles;

[0016] (2) Under the action of the surface tension of the organic medium, the liquid metal is dispersed, compressed, and coated by the surface tension after being sprayed into the liquid metal, thereby reducing the oxygen content on the surface of the metal spheres and ensuring the sphericity of the spheres after being formed. The metal spherical powder has a small particle size (<50 microns), is evenly dispersed, has a high sphericity (C>0.995), and has a low oxygen content (<500 ppm).

[0017] (3) The present invention can effectively control the negative pressure generated by the jet pump to absorb the molten liquid metal and disperse it into the organic medium by controlling the flow rate of the organic medium. The method is simple and reduces the difficulty of preparing metal spherical micropowders. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the jet injection device structure; in the figure, 1-collecting valve, 2-organic medium II, 3-heating device I, 4-collector, 5-heating device II, 6-metal melt, 7-second container, 8-jet pump, 9-liquid supply pipe, 10-heating device III, 11-organic medium I, 12-organic medium inlet, 13-first container;

[0019] Figure 2 This is the SEM image of the metal spherical micropowder of Example 1;

[0020] Figure 3 This is the SEM image of the metal spherical micropowder of Example 2;

[0021] Figure 4 This is the SEM image of the metal spherical powder of Example 3. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0023] Example 1: A method for preparing ultrafine spherical metal powder based on a jet injection method, wherein the preparation is performed using a jet injection device, wherein the jet injection device (see Figure 1 ) comprises a first container, a second container, a jet pump, and a collector, wherein the first container is filled with an organic medium, the second container is filled with a molten metal, and the collector is filled with an organic medium with a gradient temperature field, wherein the gradient temperature field is a temperature field that changes uniformly from high temperature to low temperature in the vertical direction; the bottom outlet of the first container is connected to the liquid inlet end of the nozzle of the jet pump through a liquid supply pipe, the molten metal outlet of the second container is connected to the suction chamber of the jet pump through a suction pipe, and the nozzle of the jet pump is connected to the top inlet of the collector through an injection pipe;

[0024] The specific steps are as follows:

[0025] (1) Filling the first container and the collector with organic medium (N500) respectively, adding 3000 g of metal (tin-silver-copper alloy) into the second container and heating and melting to form a uniform melt;

[0026] (2) The nozzle size of the jet pump was selected to be 0.05 mm, the injection rate of the organic medium of the jet pump was set to 10 m / s, and the gradient temperature field height of the organic medium (N500) was set to 100 cm, where the gradient temperature field is a temperature field that changes uniformly from high temperature to low temperature in the vertical direction. The starting temperature of the gradient temperature field of the organic medium is 230 ° C (10 ° C overheating of the metal melting point) and the ending temperature is 200 ° C;

[0027] (3) The organic medium in the first container is heated to a preset temperature (230°C), and the organic medium in the collector is heated to form a preset gradient temperature field. When the organic medium in the first container is ejected at a high speed through the nozzle of the jet pump, a vacuum or negative pressure is formed at the connection point of the suction pipe of the jet pump because the gas is swept away by the jet. The molten liquid metal is sucked into the suction chamber of the jet pump through the suction pipe. The molten liquid metal and the organic medium are mixed in the throat section of the injection pipe, and the molten liquid metal is broken into tiny metal droplets at the nozzle and formed into spherical micro-metal droplets through the surface tension of the organic medium. At the same time, momentum exchange is performed to increase the kinetic energy of the transported tiny metal droplets. The kinetic energy is then converted into pressure energy through the diffusion tube of the injection pipe and enters the organic medium with a gradient temperature field in the collector. The spherical micro-metal droplets slowly descend in the organic medium with a gradient temperature field and condense into spherical metal micro-powders. The solid and liquid are separated, and the solid is washed and dried to obtain ultrafine spherical metal powder with a preset particle size.

[0028] Dispersed tiny liquid metal droplets are formed under the protection of an organic medium. During the process, due to the non-uniform dispersion path, it is not easy to form a tail-end collision. The liquid alloy droplets are compressed in volume under the action of the surface tension of the organic medium to form particles with low oxygen content and high sphericity.

[0029] The SEM image of the metal spherical powder of this embodiment is shown in FIG. Figure 2 ,from Figure 2 It can be seen that the prepared metal powder has no satellite ball phenomenon, small particle size and high sphericity.

[0030] The ultrafine spherical metal powder of this embodiment is 2583 g, the metal alloy utilization rate is more than 86%, the particle size is 5-30 μm, and the oxygen content is less than 300 ppm.

[0031] Example 2: A method for preparing ultrafine spherical metal powder based on a jet injection method, wherein the preparation is performed using a jet injection device, wherein the jet injection device (see Figure 1 ) comprises a first container, a second container, a jet pump, and a collector, wherein the first container is filled with an organic medium, the second container is filled with a molten metal, and the collector is filled with an organic medium with a gradient temperature field, wherein the gradient temperature field is a temperature field that changes uniformly from high temperature to low temperature in the vertical direction; the bottom outlet of the first container is connected to the liquid inlet end of the nozzle of the jet pump through a liquid supply pipe, the molten metal outlet of the second container is connected to the suction chamber of the jet pump through a suction pipe, and the nozzle of the jet pump is connected to the top inlet of the collector through an injection pipe;

[0032] The specific steps are as follows:

[0033] (1) Fill the first container and the collector with organic medium (N500), add 3000 g of metal (indium tin) into the second container and heat and smelt to form a uniform melt;

[0034] (2) The nozzle size of the jet pump was selected to be 0.02 mm, the injection rate of the organic medium of the jet pump was set to 10 m / s, and the gradient temperature field height of the organic medium (N500) was set to 95 cm, where the gradient temperature field is a temperature field that changes uniformly from high temperature to low temperature in the vertical direction. The starting temperature of the gradient temperature field of the organic medium is 130 ° C (the metal melting point is 10 ° C overheated) and the ending temperature is 80 ° C;

[0035] (3) The organic medium in the first container is heated to a preset temperature (130°C), and the organic medium in the collector is heated to form a preset gradient temperature field. When the organic medium in the first container is ejected at a high speed through the nozzle of the jet pump, a vacuum or negative pressure is formed at the connection point of the suction pipe of the jet pump because the gas is swept away by the jet. The molten liquid metal is sucked into the suction chamber of the jet pump through the suction pipe. The molten liquid metal and the organic medium are mixed in the throat section of the injection pipe, and the molten liquid metal is broken into tiny metal droplets at the nozzle and formed into spherical micro-metal droplets through the surface tension of the organic medium. At the same time, momentum exchange is performed to increase the kinetic energy of the transported tiny metal droplets. The kinetic energy is then converted into pressure energy through the diffusion tube of the injection pipe and enters the organic medium with a gradient temperature field in the collector. The spherical micro-metal droplets slowly descend in the organic medium with a gradient temperature field and condense into spherical metal micro-powders. The solid and liquid are separated, and the solid is washed and dried to obtain ultrafine spherical metal powder with a preset particle size.

[0036] Dispersed tiny liquid metal droplets are formed under the protection of an organic medium. During the process, due to the non-uniform dispersion path, it is not easy to form a tail-end collision. The liquid alloy droplets are compressed in volume under the action of the surface tension of the organic medium to form particles with low oxygen content and high sphericity.

[0037] The SEM image of the metal spherical powder of this embodiment is shown in FIG. Figure 3 ,from Figure 3 It can be seen that after increasing the power of the jet pump and reducing the size of the nozzle, the metal-containing organic medium ejected becomes finer, thereby increasing the space for the metal to disperse in the organic medium, and the size of the obtained metal particles is narrower and the particle size is relatively smaller;

[0038] The ultrafine spherical metal powder of this embodiment is 2970 g, the metal alloy utilization rate is more than 99%, the particle size is 5-20 μm, and the oxygen content is less than 400 ppm.

[0039] Example 3: A method for preparing ultrafine spherical metal powder based on a jet injection method, wherein the preparation is performed using a jet injection device, wherein the jet injection device (see Figure 1 ) comprises a first container, a second container, a jet pump, and a collector, wherein the first container is filled with an organic medium, the second container is filled with a molten metal, and the collector is filled with an organic medium with a gradient temperature field, wherein the gradient temperature field is a temperature field that changes uniformly from high temperature to low temperature in the vertical direction; the bottom outlet of the first container is connected to the liquid inlet end of the nozzle of the jet pump through a liquid supply pipe, the molten metal outlet of the second container is connected to the suction chamber of the jet pump through a suction pipe, and the nozzle of the jet pump is connected to the top inlet of the collector through an injection pipe;

[0040] The specific steps are as follows:

[0041] (1) The organic medium (polyalphaolefin) is filled in a first container and a collector respectively, and 3000 g of metal (tin-lead) is added to a second container and heated and smelted to form a uniform melt;

[0042] (2) Selecting a jet pump nozzle size of 0.05 mm, setting the jet pump organic medium injection rate to 10 m / s, and the gradient temperature field height of the organic medium (polyalphaolefin) to 95 cm, wherein the gradient temperature field is a temperature field that changes uniformly from high temperature to low temperature in the vertical direction, and the starting temperature of the gradient temperature field of the organic medium is 210 ° C (the metal melting point is 30 ° C overheated) and the ending temperature is 160 ° C; according to the particle size of the ultrafine spherical metal powder to be prepared and the viscosity of the organic medium, calculate the jet pump organic medium injection rate, the jet pump nozzle size, and the gradient temperature field height of the organic medium;

[0043] (3) The organic medium in the first container is heated to a preset temperature (210°C), and the organic medium in the collector is heated to form a preset gradient temperature field. When the organic medium in the first container is ejected at a high speed through the nozzle of the jet pump, a vacuum or negative pressure is formed at the connection point of the suction pipe of the jet pump because the gas is swept away by the jet. The molten liquid metal is sucked into the suction chamber of the jet pump through the suction pipe. The molten liquid metal and the organic medium are mixed in the throat section of the injection pipe, and the molten liquid metal is broken into tiny metal droplets at the nozzle and formed into spherical micro-metal droplets through the surface tension of the organic medium. At the same time, momentum exchange is performed to increase the kinetic energy of the transported tiny metal droplets. The kinetic energy is then converted into pressure energy through the diffusion tube of the injection pipe and enters the organic medium with a gradient temperature field in the collector. The spherical micro-metal droplets slowly descend in the organic medium with a gradient temperature field and condense into spherical metal micro-powders. The solid and liquid are separated, and the solid is washed and dried to obtain ultrafine spherical metal powder with a preset particle size.

[0044] Dispersed tiny liquid metal droplets are formed under the protection of an organic medium. During the process, due to the non-uniform dispersion path, it is not easy to form a tail-end collision. The liquid alloy droplets are compressed in volume under the action of the surface tension of the organic medium to form particles with low oxygen content and high sphericity.

[0045] The SEM image of the metal spherical powder of this embodiment is shown in FIG. Figure 4 ,from Figure 4 It can be seen that by changing the organic medium, particles with smooth surfaces can also be obtained. As can be seen from the figure, there are no satellite balls, but the particle size distribution range is relatively large. Under the same conditions, polyalphaolefin can obtain better metal powder.

[0046] The ultrafine spherical metal powder of this embodiment is 2973 g, the metal alloy utilization rate is more than 99%, the particle size is 5-30 μm, and the oxygen content is less than 300 ppm.

[0047] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A method for preparing ultrafine spherical metal powder based on a jet injection method, characterized in that: The preparation is carried out using a jet injection device, which includes a first container, a second container, a jet pump, and a collector. The first container is filled with an organic medium, the second container is filled with a metal melt, and the collector is filled with an organic medium with a gradient temperature field, where the gradient temperature field is a temperature field that changes uniformly from high temperature to low temperature in the vertical direction. The bottom outlet of the first container is connected to the liquid inlet end of the nozzle of the jet pump through a liquid supply pipe, the metal melt outlet of the second container is connected to the suction chamber of the jet pump through a suction pipe, and the nozzle of the jet pump is connected to the top inlet of the collector through the injection pipe. The specific steps are as follows: (1) The organic medium is filled into a first container and a collector respectively, and the metal is added into a second container and heated and smelted to form a uniform melt; (2) Selecting a nozzle size of 0.01 mm to 0.1 mm for the jet pump, setting the jet velocity of the organic medium of the jet pump to 10 to 30 m / s, and setting the gradient temperature field height of the organic medium to 80 to 100 cm, wherein the gradient temperature field is a temperature field that changes uniformly from high temperature to low temperature in the vertical direction; (3) The organic medium in the first container is heated to a preset temperature, and the organic medium in the collector is heated to form a preset gradient temperature field. When the organic medium in the first container is ejected at a high speed through the nozzle of the jet pump, a vacuum or negative pressure is formed at the connection point of the suction pipe of the jet pump because the gas is swept away by the jet. The molten liquid metal is sucked into the suction chamber of the jet pump through the suction pipe. The molten liquid metal and the organic medium are mixed in the throat section of the injection pipe, and the molten liquid metal is broken into tiny metal droplets at the nozzle and formed into spherical micro-metal droplets through the surface tension of the organic medium. At the same time, momentum exchange is performed to increase the kinetic energy of the transported tiny metal droplets. The kinetic energy is then converted into pressure energy through the diffusion tube of the injection pipe and enters the organic medium with a gradient temperature field in the collector. The spherical micro-metal droplets slowly descend in the organic medium with a gradient temperature field and condense into spherical metal micro-powders. The solid and liquid are separated, and the solid is washed and dried to obtain ultrafine spherical metal powder with a preset particle size.

2. The method for preparing ultrafine spherical metal powder based on the jet injection method according to claim 1, characterized in that: In step (1), the metal is a single metal, a binary alloy, a ternary alloy, a quaternary alloy or a high entropy alloy, and the melting point of the metal is 50-300°C.

3. The method for preparing ultrafine spherical metal powder based on the jet injection method according to claim 1 or 2, characterized in that: The boiling point of the organic medium is 30-100°C higher than the melting point of the metal. The preset temperature of the organic medium in the first container is 20-50°C higher than the melting point of the metal. The starting end temperature of the gradient temperature field is 10-20°C higher than the melting point of the metal, and the end temperature is 30-50°C lower than the melting point of the metal.

4. The method for preparing ultrafine spherical metal powder based on the jet injection method according to claim 3, characterized in that: The organic medium is ether, alcohol or lipid.

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