JP2017190516A - Metal particle manufacturing method and metal particle manufacturing apparatus - Google Patents

Abstract

Disclosed is a metal particle manufacturing method and apparatus capable of manufacturing metal particles of high quality without dropping and chipping without causing collision of particles due to too high a falling speed and high quality. In manufacturing metal particles from molten metal, a pulse pressure is generated in a piezoelectric element, and a molten metal in which a pulse pressure is held in a holding container by a vertically moving operation of a plunger by the pulse pressure. The molten metal to which the pulse pressure has been transmitted is displaced beyond the critical displacement, and the molten metal is supplied from the nozzle 104 provided in the holding container one by one into the inert gas atmosphere in the recovery cylinder 113. The particles are discharged as monodisperse particles 130 to form a sphere, and an alternating magnetic field is generated in the collection cylinder from the outside of the collection cylinder by the electromagnet 112. The monodisperse particles discharged into the collection cylinder are caused to express a magnetic volume force upward. The spherical monodisperse particles are recovered while reducing the falling speed of the monodisperse particles. [Selection] Figure 1

Description

  The present invention relates to a metal particle manufacturing method and a metal particle manufacturing apparatus that discharges a molten metal material from a nozzle head and recovers metal particles in a recovery unit using an electromagnet to manufacture metal particles.

  Regardless of the material, uniform particles with uniform shapes are widely used in various science and technology fields including electrical products, and the demand for the particles is expanding. For example, uniform particles of silicon dioxide produced by a sol-gel method are widely used in liquid crystal panels as means for accurately ensuring the interval between glass plates that enclose liquid crystals.

  Also, solder particles are used for the electrode portions for connection to the circuit board of the semiconductor IC package. The solder particles are used in a BGA (ball grid array) package, which is a semiconductor IC package having a grid electrode arrangement. Many BGA package terminals having a pitch of 0.3 to 1.0 mm are widely used, and accordingly, BGA balls having a particle diameter of 200 to 800 μm are widely used.

  It is very important that the solder particles are free of dents and chips. For example, an apparatus for mounting solder particles on a BGA package is required to roll without stagnation in order to continuously supply solder particles. If the rolling of the solder particles is poor, the supply of the solder particles is stopped in the middle of the apparatus. Therefore, it is necessary to frequently adjust the supply portion, and the production efficiency is remarkably reduced. Also, as a method of mounting solder particles on a BGA package with high accuracy, a nozzle portion arranged with high accuracy in accordance with the BGA package is evacuated, and solder particles are adsorbed on this portion and arranged at a predetermined position. There is. At this time, if there are a lot of dents or chips on the surface of the solder particles, they cannot be adsorbed, a terminal on which no solder particles are mounted is formed, and the BGA package itself becomes defective.

  As means for producing the solder particles, pressure and vibration are applied to the molten metal in the crucible, the molten metal is pushed out from the orifice provided at the bottom of the crucible, and the molten metal dropped from the orifice is rapidly cooled and solidified, thereby A method for producing particles is called a uniform droplet spraying method and has been proposed (see, for example, Patent Document 1). FIG. 10 is a diagram showing a conventional uniform droplet spraying method described in Patent Document 1. In FIG.

  Here, the above-described uniform droplet spraying apparatus will be described more specifically with reference to FIG. A vibration is generated by the piezo element 1, and the vibration is transmitted to the molten metal 4 through the vibration rod 3. The dissolution chamber 5 is in a state where gas is supplied from the gas supply port 2 and is pressurized. Since the molten metal 4 pushed out from the orifice 6 of the melting chamber 5 by the gas pressure is given vibration, the molten metal 4 is divided at regular intervals to form droplets 8. In the electrode plate 7, a potential is applied between the electrode plate 7 and the molten metal 4, thereby charging the droplets 8 to the same charge and preventing the droplets 8 from contacting each other. These droplets 8 are spheroidized by the surface tension of the droplets 8 themselves while falling in the chamber 9, and are cooled and solidified during flight in the gas atmosphere.

  An inert gas is supplied from the gas supply port 11 into the chamber 9 to prevent the droplet 8 from being oxidized. The pressure in the chamber 9 is lower than that in the dissolution chamber 5. Eventually, the spherical solidified body 10 is recovered at the bottom of the chamber 9.

JP 2005-103645 A

  However, in the conventional configuration, the falling speed of the metal particles discharged in the inert gas collides with each other, resulting in the formation of poor quality particles (such as dents or chips), and the production yield. Has the problem of being bad.

  The present invention solves the above-mentioned conventional problems, and the drop speed is too high so that the particles do not collide with each other, and there is no dent and chipping, and high quality metal particles can be produced in a high yield. It aims at providing the manufacturing method and apparatus of a metal particle.

In order to achieve the above object, a method for producing metal particles according to one aspect of the present invention, when producing metal particles from molten metal,
Generate a pulse pressure on the piezoelectric element,
By the vertical movement operation of the plunger by this pulse pressure, the pulse pressure is transmitted to the molten metal held in a holding container,
Displacement exceeding the critical displacement occurs in the molten metal to which the pulse pressure has been transmitted, and the molten metal is monodispersed one by one in an inert gas atmosphere in a collection cylinder from a nozzle provided in the holding container. Discharged as particles and spheroidized,
An alternating magnetic field is generated in the recovery cylinder by an electromagnet from the outside of the recovery cylinder, and the monodisperse particles discharged in the recovery cylinder are caused to express a magnetic volume force upward, and the falling speed of the monodisperse particles The spheroidized monodisperse particles are recovered while reducing the above.

  As described above, according to the above aspect of the present invention, the falling speed is too high so that the particles do not collide with each other, and there are no dents and chips, so that high quality metal particles can be produced in a high yield. .

Sectional drawing of the metal particle manufacturing apparatus in embodiment of this invention The figure which shows how to take the coordinate of the electromagnet when demonstrating the electromagnet and magnetic field strength in embodiment of this invention The figure which shows the electromagnet and magnetic field intensity in embodiment of this invention The figure which shows the electromagnet and magnetic field intensity in embodiment of this invention The figure which shows the force added to the metal particle in embodiment of this invention The figure which shows the force added to the metal particle in embodiment of this invention The graph showing the relationship between the falling speed of metal particles, crushing, chipping and solidification in the embodiment of the present invention The graph showing the relationship between the fall speed and the applied magnetic field strength in the embodiment of the present invention The figure which shows the SEM image of the metal particle produced at the time of no magnetic field in the comparative example 1-1 of this invention. The figure which shows the SEM image of the metal particle produced at the time of the magnetic field strength 1.5T application in Example 1-2 of this invention. The figure which shows the SEM image of the metal particle produced at the time of the magnetic field intensity 2.5T application in the comparative example 1-3 of this invention. The figure showing the relationship between the discharge particle diameter and magnetic field intensity in embodiment of this invention The figure which shows the conventional uniform droplet spraying apparatus described in patent document 1

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a metal particle manufacturing apparatus 90 used in the method for manufacturing metal particles in the embodiment of the present invention. The metal particle manufacturing apparatus 90 includes a discharge unit 120 that discharges molten metal and a recovery unit 121 that recovers the metal particles 130 discharged from the discharge unit 120, and manufactures metal particles from the molten metal. An example of the metal particle is a metal particle having a particle diameter of 200 to 800 μm.

  First, the discharge unit 120 that discharges metal particles will be described.

(Discharge unit 120)
As an example, the ejection unit 120 includes the nozzle head 100. The nozzle head 100 includes a molten metal supply chamber 101, a pressure chamber 105, a nozzle 104, a piezoelectric element 107 and a plunger 106 as an example of a discharge force applying device.

The molten metal supply chamber 101 is formed in a holding container 91 that stores a metal material as a raw material as a molten metal. A heating mechanism 102 is provided around the supply chamber 101 of the holding container 91, and the metal material in the supply chamber 101 is heated to the melting point or higher to be melted and held as molten metal. The bottom surface 101a of the supply chamber 101 has a funnel shape, and a concave portion 101b is provided at the center of the bottom surface 101a. 103 can be supplied. An example of the molten metal material 103 is a solder material, which is an alloy containing SnAgBiInCu as a main component.
The nozzle 104 is disposed at the lower end of the pressure chamber 105 so that the pressure chamber 105 communicates with the nozzle 104, and the molten metal material 103 is sent downward from the pressure chamber 105 with a predetermined pressure and can be discharged downward from the nozzle 104.

  The plunger 106 passes through the supply chamber 101 in the vertical direction, and a lower end tip portion 111 is disposed so as to be vertically movable in the recess 101 b of the supply chamber 101 and the pressure chamber 105. A convex portion is formed so as to protrude from the entire periphery of the side surface of the lower end of the concave portion 101b to constitute a small diameter portion 101c. The distal end portion 111 of the plunger 106 is processed into a spire shape. The distal end portion 111 and the small diameter portion 101c are used to supply a supply chamber 101 above the small diameter portion 101c and a pressure chamber 105 below the small diameter portion 101c. The molten metal material 103 supplied into the pressure chamber 105 can be pressurized. Therefore, when the tip 111 of the plunger 106 moves up and down in the pressure chamber 105, the molten metal material 103 can be supplied from the recess 101 b into the pressure chamber 105 through the small diameter portion 101 c and the pressure chamber 105. A pressure for discharging from the nozzle 104 can be generated with respect to the metal material 103 supplied therein.

  The upper end of the plunger 106 is connected to a piezoelectric element 107 that generates thrust, and the plunger 106 has an action of transmitting the thrust of the piezoelectric element 107 to the pressure chamber 105. The piezoelectric element 107 is fixed to the upper part of the supply chamber 101 by a fixture 108.

  The piezoelectric element 107 is electrically connected to the external power source 109 and the function generator 110 and can be driven by the external power source 109 via the function generator 110. A rectangular wave voltage having a predetermined frequency is generated in the function generator 110, a rectangular wave voltage is applied from the function generator 110 to the piezoelectric element 107, and a vibration having a predetermined frequency and a predetermined amplitude is generated in the piezoelectric element 107. As a result, the plunger 106 which is substantially integrated with the piezoelectric element 107 is vibrated in the vertical direction with respect to the holding container 91 with a pulse having the same frequency, and the pressure chamber 105 in contact with the distal end side of the plunger 106 A pulse pressure wave is generated in the molten metal material 103.

  Thereby, when the piezoelectric element 107 is displaced downward in FIG. 1 by a predetermined displacement amount or more (displaced more than the critical displacement), the molten metal material 103 in the pressure chamber 105 is discharged from the nozzle 104 via the plunger 106. Discharge in the form of drops. This discharge is performed once per cycle of the pulse pressure wave. Here, the critical displacement of the piezoelectric element 107 is a critical displacement generated in the molten metal (molten metal material 103), and the molten metal material 103 in the pressure chamber 105 is ejected from the nozzle 104 in the form of droplets. It means the displacement to the extent. For example, when producing metal particles having a particle diameter of 200 to 800 μm, if the inner diameter of the nozzle 104 is 160 to 640 μm, the predetermined frequency is 10 to 1000 Hz and the predetermined amplitude is 0.5 to 170 μm (displacement). The inner diameter of the nozzle 104 and the frequency or amplitude of the displacement of the piezoelectric element 107 are not particularly limited, and are appropriately determined depending on the type of the metal material to be processed, the particle diameter of the metal particles, the required production speed, or the like. Just choose.

(Recovery unit 121)
Next, the collection | recovery part 121 which comprises the metal particle manufacturing apparatus 90 is demonstrated.

  A recovery unit 121 for capturing the discharged metal particles 130 is provided below the nozzle 104 constituting the discharge unit 120. The recovery unit 121 includes an electromagnet 112, a cylindrical recovery cylinder 113 to which an inert gas is supplied, a gate valve 114, and a metal particle recovery box 115 as an example of a recovery member. Therefore, the electromagnet 112 is provided outside the collection unit 121 within, for example, 30 cm from the upper end of the collection unit 121. A gate valve 114 is disposed below the electromagnet 112 and at the lower end of the collection cylinder 113 so that it can be opened and closed with respect to the metal particles 130 discharged in the collection cylinder 113 and cooled in the collection cylinder 113. Further below the gate valve 114 is connected a metal particle recovery box 115 that recovers the metal particles 130 that fall through the gate valve 114 when the gate valve 114 is opened.

  The molten metal material 103 discharged from the nozzle 104 into the recovery cylinder 113 becomes spherical due to its surface tension, and is cooled in the gas in the recovery cylinder 113 to form a sphere. At this time, in order to suppress the oxidation of the surface, an inert gas such as nitrogen is supplied from the inert gas supply device 95 into the recovery cylinder 113 at a minute flow rate from the bottom upward, and the recovery cylinder 113 is supplied with nitrogen or the like. An inert gas atmosphere is formed. With such a configuration, it is desirable that the metal material 103 be discharged and cooled into an inert gas atmosphere such as nitrogen in the recovery cylinder 113.

  In addition, a rectangular wave AC voltage is applied to the electromagnet 112 by using an external power source 117 and a function generator 116. The electromagnet 112 is a cylindrical electromagnet that is arranged on the outer periphery of the recovery cylinder 113 and generates an alternating magnetic field whose magnetic field direction changes with time. The magnetic field direction and the axial direction along the vertical direction of the recovery cylinder 113 are parallel to each other. It is installed as follows. An alternating magnetic field whose magnetic field direction changes over time means an alternating magnetic field that reverses the polarity of the magnetic field about a hundred to several hundred times within a few ms at a certain magnetic field strength, for example. The AC voltage, magnetic field strength, time, number of inversions, and the like vary depending on the type of metal or the particle size of the metal particles. It should be noted that there is a relationship between the frequency generated in the piezoelectric element 107 and the number of times the magnetic field is reversed, for example, the number of times the magnetic field is reversed is within a range of ± 10% of the frequency generated in the piezoelectric element 107. If inside, the falling speed of the metal particle 130 may be more easily controlled.

  An electromagnet is obtained by measuring (calculating) the falling speed when the discharged metal material 103 falls as the metal particles 130 using an imaging device such as a high-speed camera 119 or a strobe camera, and feeding back the measurement result to the function generator 116. The direction of the magnetic field is controlled by controlling the polarity of the magnetic field at the center of 112, an alternating magnetic field is generated for the metal particles 130, and a magnetic volume force is expressed to reduce the falling speed. This feedback can be performed as follows, for example.

  First, under predetermined initial conditions, the polarity of the magnetic field at the center of the electromagnet 112 is controlled to control the direction of the magnetic field, an alternating magnetic field is generated for the metal particles 130, and the magnetic volume force is increased. In the state of being expressed, the metal particle 130 starts to fall. As an example of the initial condition, any one of the conditions of the examples described later may be selected as appropriate.

  Next, the high-speed camera 119 images the metal particles 130 falling in the collection cylinder 113 through the transparent window 96 of the collection cylinder 113, and the particle size is calculated by the calculation unit 94 based on the volume of the metal particles 130. This is because the metal particles 130 immediately after falling are not necessarily spherical but may have a shape different from a spherical shape such as an ellipse. And the diameter in the case of a sphere is calculated from the obtained volume. The determination unit 93 determines whether the calculated diameter is a desired particle size. If the calculated diameter is not the desired particle size, control factors such as AC voltage, magnetic field strength, time, and number of inversions are changed. When the calculated diameter is a desired particle diameter, the following drop speed is measured.

  Next, the falling speed of the metal particles 130 is measured by the high speed camera 119. As an example of measurement, the calculation unit 94 calculates the falling speed of the metal particles 130 from information obtained by imaging the metal particles 130 falling by the high-speed camera 119. The determination unit 93 determines whether or not the falling speed of the metal particles 130 calculated by the high-speed camera 119 exceeds the upper limit value of the falling speed at which the falling speed is too high and the particles collide with each other. When the determination unit 93 determines that the calculated fall speed exceeds the upper limit value, the polarity of the alternating magnetic field is reversed more frequently than the voltage set to reverse the polarity of the alternating magnetic field at that time. A correction signal for applying an additional voltage is output from the determination unit 93 to the function generator 116. On the other hand, when the determination unit 93 determines that the calculated fall speed does not exceed the upper limit value, the function generator generates a signal from the determination unit 93 that keeps applying the voltage so as to maintain the AC magnetic field at that time. To 116. The upper limit is not limited to the drop speed at which the particles collide with each other because the drop speed is too fast. Good.

  Thus, the high-speed camera 119, the calculation unit 94, the determination unit 93, and the function generator 116 function as an example of the AC magnetic field control unit 92 in this way.

  In this way, an alternating magnetic field is generated for the metal particles 130 falling while being cooled in the recovery cylinder 113, and an upward magnetic volume force is expressed in the metal particles 130, thereby reducing the falling speed of the metal particles 130. Then, the metal particles are collected in the metal particle collection box 115 through the gate valve 114.

  FIG. 2A shows how to take the coordinates of the electromagnet 112 in the embodiment of the present invention. The center of the electromagnet 112 is the origin, the applied magnetic field direction is the z axis, and the axes perpendicular to the z axis are the x and y axes, which are orthogonal to the z axis. FIG. 2B shows the magnetic field distribution in the x and y directions, and FIG. 2C shows the magnetic field distribution in the z direction. In each of FIG. 2B and FIG. 2C, a vertical axis | shaft represents magnetic field strength [T] and a horizontal axis represents a coordinate [cm]. From these figures, it is understood that the origin of the electromagnet 112 has the strongest magnetic field strength because it is a solenoid type cylindrical magnet. The magnetic field gradient is negative in the first quadrant of the z axis and positive in the second quadrant. In order to suppress the disturbance in the ejection direction, the metal particles 130 preferably pass through the central part of the solenoid-type cylindrical electromagnet 112 with a small magnetic field gradient on the xy axis. In addition, when a high magnetic field is generated, the electromagnet 112 may generate heat and the magnetic field strength may be reduced. Therefore, cooling water is circulated in the electromagnet 112 by the centrifugal pump 118. In order to maximize the cooling capacity, it is preferable to use an antifreeze liquid as the cooling water and manage it at −10 to 0 ° C.

  Next, a mechanism for reducing the falling speed by applying an alternating magnetic field to the metal particles 130, which is a feature of the present embodiment, to develop a magnetic volume force will be described.

  When the metal particles 130 are discharged from the nozzle 104 into the collection cylinder 113, the metal particles 130 are spheroidized by surface tension, and then force due to gravity and air resistance is applied to the metal particles 130. By applying a magnetic field therewith using the electromagnet 112, the magnetic volume force upwards

Is expressed in the metal particles 130 and the action of gravity is reduced, so that the falling speed (falling speed) of the metal particles 130 can be reduced. Here, M is the magnetization [A / m], H is the magnetic field [A / m] generated by the electromagnet 112, V is the volume [m ³ ] of the magnetic material that is the metal particle 130, and χ is the magnetic susceptibility [ m ³ / kg] and ΔH are magnetic field gradients [A / m], bold letters represent vector quantities, and thin letters represent scalar quantities.

  From this formula, magnetic body force

It can be seen that the direction of is determined by the direction of the magnetization M of the discharged metal particles 130 and the magnetic gradient ΔH. Further, the magnetization M can be expressed by the product of the magnetic field strength H and the magnetic susceptibility χ of the metal particle 130. By changing the direction of the magnetic field up and down depending on whether the magnetic susceptibility χ of the metal particle 130 is positive or negative, the magnetization M The direction can be controlled.

  As an example, the case where the metal particle 130 is a SnAgBiInCu solder formed of tin, silver, bismuth, indium, and copper is shown. Table 1 shows the magnetic susceptibility χ of each metal forming the SnAgBiInCu solder.

  From Table 1, it can be seen that the magnetic susceptibility χ of all the formed metals is χ <0 and is a diamagnetic material.

  Also, FIG. 3A shows the force applied when SnAgBiInCu solder is ejected when a magnetic field gradient is applied negatively or downwardly at the top of the electromagnet 112, and FIG. 3B shows all the force applied when the magnetovolumetric force is expressed. The power of Here, the downward direction of gravity is negative, and the upward direction is positive. When a magnetic field is applied downward as shown in FIG. 3A, SnAgBiInCu solder is a diamagnetic material (susceptibility χ <0), and thus magnetizes upward in the direction opposite to the direction of the magnetic field, and magnetic volume force is applied upward. Therefore, as shown in FIG. 3B, in addition to the gravity and air resistance applied after ejection, the magnetic bulk force can be further expressed to reduce the falling speed of the metal particles 130.

  Further, when the metal particle 130 is a ferromagnetic material, since the magnetic susceptibility χ> 0, it is necessary to apply upward, and it is necessary to change depending on the composition of the metal particle 130.

  Examples in which metal particle diameters of 300 ± 10 μm and 500 ± 10 μm are manufactured using nozzle diameters of 300 μm and 500 μm are shown below.

Example 1
In the metal particle manufacturing apparatus shown in each figure, a multilayer piezoelectric element was used as the piezoelectric element 107. The maximum displacement amount of the piezoelectric element 107 is 14.7 μm, and the frequency characteristic is 1.7 MHz. Here, the temperature was controlled so that the temperature of the piezoelectric element 107 did not exceed 40 ° C. The members that become high temperature, for example, the plunger 106 and the nozzle 104 are made of SUS and controlled to a constant temperature. Further, one nozzle 104 was provided within the diameter (about 8 mm) of the plunger 106. The nozzle diameter was about 300 μm (0.3 mm).

  The composition of the metal particles 130 is Sn-Ag-Bi-In-Cu-based alloy (melting point: about 210 ° C) used as lead-free solder, heated to 250 ° C using the heating mechanism 102, and recovered part Into 121, nitrogen gas as an inert gas was introduced at a pressure of about 1 kPa. The molten metal material 103 discharged from the nozzle 104 was recovered in a metal particle recovery box 115 about 1 m below the nozzle 104.

  The operating frequency of the piezoelectric element 107 was set to 100 Hz, and after confirming that the temperature of the piezoelectric element 107 was constant, metal particles were manufactured for 8 hours (about 3 million pieces). Although not described in detail, a strobe camera is installed in the collection unit 121 to observe the shape of the discharged metal particles 130 in real time, and based on the observation result, the AC magnetic field control unit 92 determines the manufacturing conditions. Adjustments were made.

  Moreover, metal particle discharge manufacture was performed by the case where the magnetic field was applied in 0.5T increments from 0.5 to 4.5T by the electromagnet 112 in the collection | recovery part 121, and the case where the magnetic field was not applied. About 1000 metal particles 130 collected in the metal particle collection box 115 are randomly sampled, observed with a scanning electron microscope (SEM) for particle shape and presence of dents or chips, and sphericity ( Long side / short side) and yield (300 ± 10 μm as desired particle size) were measured.

  Table 2 shows the results of evaluating the recovered metal particles 130.

  From Table 2, when 1.0 to 2.0 T is applied, the metal particles 130 are not chipped and dented, and the average sphericity is close to 1, and the difference between the long side and the short side is about 3 It can be mounted without rolling resistance when actually mounted on a BGA package. It can also be seen that the yield is 90% or more and the productivity is good. In other ranges, the average sphericity is close to 1.3 and the difference between the long side and the short side is about 30%, indicating that the quality is poor. In the following, the factors that cause such differences depending on the magnetic field strength will be considered.

  FIG. 4 shows the relationship between the falling speed of the metal particles 130, crushing or chipping, and solidification. FIG. 4 is a biaxial graph, where the vertical axis represents the impact force [N] due to particle collision and the cooling time [s] of the metal particles, and the horizontal axis represents the drop time. The relationship between crushing or chipping and metal solidification is a trade-off relationship with respect to the drop velocity [m / s]. If the drop velocity is too high, the metal material 103 is spheroidized by surface tension before solidifying. Since it enters the metal particle recovery box 115, flat particles are generated. In addition, since the impact force caused by the collision of the particles with the particles contained in the metal particle recovery box 115 also increases, chips or cracks enter the particles. For this reason, in order to produce high quality particles, it is necessary to have a certain falling speed or less.

  FIG. 5 shows the relationship between the drop speed and the applied magnetic field strength and the results of the implementation. The vertical axis represents the falling speed [m / s] of the metal particles measured (calculated) using the high-speed camera 119, the horizontal axis represents the applied magnetic field strength, and the hatched portion is a metal particle having no chipping or dent. Represents a manufacturable range. The region where high-quality metal particles can be produced in a high yield is a range where the falling speed is 0.4 m / s ≦ v ≦ 0.8 m / s (the magnetic field strength is 1.0 T ≦ H ≦ 2.0 T). .

  In Comparative Example 1-1, Example 1-2, and Comparative Example 1-3, SEM images of the metal particles 130 recovered from the metal particle recovery box 115 are shown in FIGS. 6, 7, and 8, respectively. Show.

  From FIG. 6, it can be seen that in the case of no magnetic field, the metal particles 130 are not circular, and there are many defects in which a part of the circle is missing. This is thought to be because the particles collided with each other when the dropping speed was too fast and was collected in the metal particle collecting box 115, or deformed because they dropped before solidification. Further, it can be seen from FIG. 8 that when the magnetic field strength is 2.5T, the metal particles are deformed in the direction of the lines of magnetic force, so that there are many flat particles instead of circular particles. On the other hand, in the case of FIG. 7, it can be seen that there are many circular particles and there are almost no chipped particles or flat particles as in FIGS.

  Therefore, in order to produce a high yield without losing or applying 300 μm of metal particles, the magnetic field strength is 1.0 T ≦ H ≦ 2.0 T (the falling speed is 0.4 m / s ≦ v ≦ 0.8 m / s).

(Example 2)
In the same manner as in Example 1, metal particles were produced with a nozzle diameter of 500 μm (0.5 mm). The results are shown in Table 3. The desired metal particle diameter is 500 ± 10 μm.

  Similar to Example 1, in Examples 2-1, 2-2, 2-3, 2-4, which are in a certain applied magnetic field range, the sphericity is close to 1, and the yield is also different from other example conditions. It can be seen that a magnetic field application of 2.0T ≦ H ≦ 3.5T is necessary in order to produce high-quality particles that are 90% or more and are free from chipping and dents.

  In Example 1, the optimum applied magnetic field strength of the metal particles was 1.0T ≦ H ≦ 2.0T, but in Example 2, the optimum applied magnetic field strength of the metal particles was 2.0T ≦ H ≦ 3. It has increased to 5T. This is due to an increase in falling speed due to an increase in the mass of discharged metal particles.

(Example 3)
FIG. 9 shows the result of discharging metal particles by changing the nozzle diameter from 0.2 to 0.8 mm in the same manner as in Example 1 and Example 2. The vertical axis represents the magnetic field strength [T] applied, the horizontal axis represents the discharged metal particle diameter [μm], and the hatched portion was able to produce metal particles with no crushing or chipping in a yield of 90% or more. Represents a range. The range of the hatched portion y-axis passes through the points of maximum magnetic field strength 2.0T, 3.5T and minimum magnetic field strength 1.0T and 2.0T, respectively, which can be manufactured with a yield of 90% or more of Examples 1 and 2. The linear function approximated by the least square method was determined from y = 7.0x and y = 3.25x. Therefore, from FIG. 9, in the case of 0.2 ≦ particle diameter x [mm] ≦ 0.8, 3.25x ≦ magnetic field strength y ≦ 7.0x, a 0.2 to 0.8 mm ball is crushed and chipped. Can be manufactured without any problem.

(Characteristics of manufactured metal particles)
Next, the characteristics of the manufactured metal particles will be described. Table 4 shows the results of bringing the 2T magnetic field closer to the 300 μm metal particles produced in Example 1-2 by 3.0 cm to 0.5 cm. When a magnetic field was applied, the reaction was evaluated as ◯, and the reaction was not evaluated as ×.

  From this result, the metal particles manufactured using the manufacturing apparatus of the present embodiment are characterized by being magnetized when a magnetic field having a magnetic field strength of 2T is applied within a distance of 1 cm, and the metal particles manufactured using another method Can be determined. Further, the evaluated metal particles are manufactured with a height of the recovery part of 0.5 m to 3.0 m.

  According to the embodiment, the electromagnet 112 capable of applying a strong magnetic field is disposed in the recovery cylinder 113, and the magnetic volume force (magnetic force) is expressed upward in the metal particles 130 by manipulating the magnetic field direction and the magnetic field gradient. In addition, by reducing the falling speed, it is possible to produce particles having good quality (no dents and chips), and the yield can be improved. Therefore, the drop speed is too high so that the particles do not collide with each other, and the metal particles 130 having good quality without dents and chips can be produced in a high yield.

  In addition, it can be made to show the effect which each has by combining arbitrary embodiment or modification of the said various embodiment or modification suitably. In addition, combinations of the embodiments, combinations of the examples, or combinations of the embodiments and examples are possible, and combinations of features in different embodiments or examples are also possible.

  The metal particle manufacturing method and apparatus according to the aspect of the present invention can always discharge a stable volume of particles having different particle diameters at a certain height. Particularly when a molten metal sphere having a high magnetic susceptibility is formed, high-efficiency production with high diameter accuracy is possible.

DESCRIPTION OF SYMBOLS 1 Piezo element 2 Supply port 3 Vibrating rod 4 Molten metal 5 Melting chamber 6 Orifice 7 Electrode plate 8 Droplet 9 Collection chamber 10 Spherical solidified body 11 Gas supply port 90 Metal particle production apparatus 91 Holding container 92 AC magnetic field control part 93 Determination part 94 Arithmetic unit 95 Inert gas supply device 96 Transparent window 100 Nozzle head 101 Supply chamber 102 Heating mechanism 103 Metal material 104 Nozzle 105 Pressure chamber 106 Plunger 107 Piezoelectric element 108 Fixing tool 109 External power supply 110 Function generator 111 Tip 112 Electromagnet 113 Collection cylinder 114 Gate valve 115 Metal particle recovery box 116 Function generator 117 External power supply 118 Centrifugal pump 119 High speed camera 120 Discharge unit 121 Recovery unit 130 Metal material (metal particles) to be discharged

Claims (8)

When producing metal particles from molten metal,
Generate a pulse pressure on the piezoelectric element,
By the vertical movement operation of the plunger by this pulse pressure, the pulse pressure is transmitted to the molten metal held in a holding container,
Displacement exceeding the critical displacement occurs in the molten metal to which the pulse pressure has been transmitted, and the molten metal is monodispersed one by one in an inert gas atmosphere in a collection cylinder from a nozzle provided in the holding container. Discharged as particles and spheroidized,
An alternating magnetic field is generated in the recovery cylinder by an electromagnet from the outside of the recovery cylinder, and the monodisperse particles discharged in the recovery cylinder are caused to express a magnetic volume force upward, and the falling speed of the monodisperse particles A method for producing metal particles, wherein the spheroidized monodispersed particles are recovered while reducing the amount of the particles. The alternating magnetic field is generated in the collection cylinder by the electromagnet, and the upward magnetic volume force is expressed in the monodisperse particles discharged into the collection cylinder, thereby reducing the falling speed of the monodisperse particles. When the AC magnetic field control unit controls the AC magnetic field generated in the recovery cylinder by the electromagnet,
The manufacturing method of the metal particle of Claim 1. The particle diameter x [mm] of the monodisperse particles is 0.2 ≦ x ≦ 0.8,
3. The method for producing metal particles according to claim 1, wherein the magnetic field strength y [T] of the alternating magnetic field has a relationship of 3.25x ≦ y ≦ 7.0x.   The manufacturing method of the metal particle of any one of Claims 1-3 whose said molten metal is a solder material and is an alloy which has SnAgBiInCu as a main component. A holding container for holding molten metal;
A nozzle that is disposed in the holding container and discharges the molten metal from the holding container;
A piezoelectric element that generates a predetermined pulse pressure;
The pulse pressure generated by the piezoelectric element is transmitted to the molten metal located at the nozzle, and is displaced to the molten metal side by a critical displacement or more, so that the molten metal is dropped from the nozzle one by one with monodisperse particles. A plunger that discharges from the holding container as
A collection cylinder communicated below the nozzle to solidify and spheroidize the monodisperse particles;
An electromagnet disposed outside the recovery cylinder to generate an alternating magnetic field in the recovery cylinder;
A recovery member that recovers the monodispersed particles in a state in which the falling speed of the monodispersed particles that have been discharged, solidified, and spheroidized is reduced by the alternating magnetic field;
Metal particle manufacturing equipment. An AC magnetic field control unit that controls the alternating magnetic field generated by the electromagnet to express the magnetic volume force upward in the metal particles and controls the falling speed of the monodisperse particles;
The apparatus for producing metal particles according to claim 5. The height of the collection part that combines the collection cylinder and the collection member is 0.5 m or more and 3.0 m or less.
The apparatus for producing metal particles according to claim 5 or 6. The collection member collects metal particles that are magnetized when a magnetic field having a magnetic field strength of 2T is applied within a distance of 1 cm as the spherical monodisperse particles.
The metal particle manufacturing apparatus according to any one of claims 5 to 7.

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