JP2017052982A - Metallic ball formation device and metallic ball formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal sphere formation device of discharging a molten metallic material solving the problem that the volume variation the discharged metallic material has been made high caused by the variation of the pressure in a discharge part in accordance with the consumption of the metallic material and the secular change of the metallic material, and the phenomenon has been made a cause of making the diameter of the formed metallic sphere unstable.SOLUTION: The shape of the metallic material to be discharged is acquired, and, in such a manner that the diameter of the metallic ball obtained by spheroidizing the discharged metallic material is made equal to desired dimensions, control is successively progressed to applied voltage to a piezoelectric element generating pressure, next, to the pressure in a container storing the molten metal, and to the liquid position of the metallic material in the container. In this way, the secular variation of the diameter of the metallic ball is suppressed, and the metallic ball having a fixed diameter is continuously produced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for forming a metal sphere having a uniform size by discharging a molten metal material and an apparatus for forming the metal sphere.

  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, in the field of semiconductor IC packages, the connection with the printed circuit board is mainly performed by using a solder material as a means for connecting the semiconductor IC package and the opposed electrodes of the printed circuit board from the connection by soldering the lead frame. The used sphere is used. This connection form of the semiconductor IC package is generally called a ball grid array because the electrode arrangement is in a lattice shape, and is known as a means for suppressing the expansion of the semiconductor package area in which the number of terminals increases.

  As means for producing a sphere of this solder material, an atomizing method in oil in which molten solder is discharged into a high-temperature oil shown in Patent Document 1 and spheroidized by surface tension is generally used.

  However, the molten solder is subjected to resistance by oil and its sphericity is lowered. In order to solve this, Patent Document 2 proposes discharging molten metal into the air by a piezoelectric actuator. However, in this method, the discharge of molten metal is unstable.

  In order to stabilize the discharge of molten metal, an apparatus and a method for acquiring the remaining amount of molten metal in the apparatus and controlling the amplitude of the piezoelectric actuator in inverse proportion to the remaining amount have been proposed (Patent Document 3). ).

JP-A-11-207493 JP 2002-155305 A JP 2003-203939 A

  However, in the method of acquiring the amount of molten metal in the apparatus and applying a predetermined signal corresponding to the remaining amount to the piezoelectric actuator (Patent Document 3), the rapid melting that occurs when the metal material composition is changed or the material is replenished It is not possible to immediately respond to changes in physical properties and manufacturing conditions, such as changes in metal content and changes in fluidity due to surface oxidation of molten metal, which is highly oxidizable, and stably discharges a predetermined amount of material. I can't. Therefore, there is a problem that the diameter of the formed sphere varies.

  The present invention has been made in view of such points, and provides a metal sphere forming method and a metal sphere forming apparatus capable of continuous operation for a long time while keeping the volume of the molten metal to be discharged constantly constant. The purpose is to do.

  In order to solve the above problems, a nozzle for discharging molten metal, a pressure chamber for generating pressure for discharging molten metal through the nozzle, a supply chamber for supplying molten metal to the pressure chamber, and a molten metal in the supply chamber A detection mechanism that acquires the volume of the liquid, a preparation chamber that replenishes the molten metal in the supply chamber, a piston that pressurizes the pressure chamber, a piezoelectric element that moves the piston, and an observation that acquires the shape of the discharged molten metal sphere Based on the information obtained from the mechanism and the observation mechanism, a first control unit for controlling the amount of molten metal in the supply chamber, and the second control for controlling the operation amount of the piezoelectric element based on the information obtained from the observation mechanism And a metal sphere forming apparatus including the unit.

  In a metal sphere formation method in which a molten metal material in a container is discharged from a nozzle to form a metal sphere, the shape of the discharged metal sphere is acquired and the deviation of the diameter of the previously designed metal sphere is minimized. Control the voltage applied to the piezoelectric element that applies pressure to the molten metal material, and further control the pressure in the container when exceeding the control range of the applied voltage, and further the pressure in the container When the control range is exceeded, a metal sphere forming method for controlling the liquid level of the molten metal material is used.

  As described above, according to the present invention, by keeping the discharge state constant, the volume of the molten metal to be discharged can be made constant, and the diameter of the metal sphere spheroidized by the surface tension can be kept constant. it can.

  Therefore, sphere formation with a desired metal composition can be performed with high accuracy. Therefore, it is possible to manufacture metal spheres having a uniform shape.

Sectional drawing which shows the structure of the metal sphere formation apparatus which concerns on embodiment Sectional drawing which shows the state which supplied the metal material to the preparation chamber in the metal ball | bowl formation apparatus of embodiment Sectional drawing which shows the state which melted the metal material in the preparation chamber in the metal ball | bowl formation apparatus of embodiment Sectional drawing which shows the state which introduce | transduced the molten metal material into the pressure chamber and supply chamber of the metal ball | bowl formation apparatus of embodiment Sectional drawing which shows the state which discharged the metal material with the metal ball | bowl formation apparatus of embodiment The flowchart which shows the state which controls the signal voltage, supply chamber pressure, metal material liquid level which concern on embodiment of embodiment The graph which shows the diameter variable range of the metal sphere by the signal voltage which concerns on embodiment of embodiment The graph which shows the diameter variable range of the metal ball | bowl by the supply chamber pressure which concerns on embodiment of embodiment The graph which shows the diameter variable range of the metal sphere by the metal material liquid level which concerns on embodiment of embodiment

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

<Configuration>
FIG. 1 is a cross-sectional view of a metal ball forming apparatus according to an embodiment of the present invention. The metal ball forming apparatus 100 is provided with a supply chamber 131 that stores a metal material 101 as a raw material. There is a heating mechanism 132 around the supply chamber 131. The heating mechanism 132 heats and melts the metal material 101 to or above its melting point. A preparation chamber 141 for replenishing the metal material 101 is connected to the supply chamber 131 via an electromagnetic valve 143. In the preparation chamber 141, a heating mechanism 142 is arranged to heat and melt the metal material 101 to the melting point or higher. Further, the supply chamber 131 is provided with a window portion 137 so that the surface of the metal material can be observed from the outside. Further, the liquid level sensor 133 provided outside can acquire the liquid level of the metal material 101 melted in the supply chamber 131 through the window portion 137.

  The metal ball forming apparatus 100 includes a nozzle 111. Further, there is a pressure chamber 121 communicating with the nozzle 111. In the pressure chamber 121, a pressure for discharging the molten metal material 101 is generated. The supply chamber 131 and the pressure chamber 121 are separated by a piston 112. Here, a gap 122 is provided between the pressure chamber 121 and the piston 112. As the metal material 101 is consumed, the metal material 101 is sequentially supplied from the supply chamber 131 to the pressure chamber 121. In addition, an electropneumatic regulator 135 is connected to the supply chamber 131 via an intake / exhaust pipe 134 (pressure adjusting unit). The electropneumatic regulator 135 can control the pressure in the supply chamber 131 and the pressure chamber 121 from the outside. Here, the piston 112 is connected to a piezoelectric element 113 that generates thrust. The piston 112 is responsible for transmitting the thrust of the piezoelectric element 113 to the pressure chamber 121. The piezoelectric element 113 is fixed by a bracket 114. The piezoelectric element 113 is electrically connected to the external power source 115. The piezoelectric element 113 can be driven by an external power source 115.

  The piezoelectric element 113 and the supply chamber 131 are separated by a partition wall 136.

  Further, below the nozzle 111, a discharge observation device 151 capable of observing a state in which the molten metal material 101 is discharged from the nozzle 111 is provided. With the discharge observation device 151, the volume and speed of the metal sphere 104 formed by the discharged metal material 103 can be acquired.

  Further, the metal ball forming apparatus 100 comprehensively controls the external power source 115, the liquid level sensor 133, the electropneumatic regulator 135, the electromagnetic valve 143, and the discharge observation device 151 by the control device 161.

  These metal ball forming apparatuses 100 are fixed to a table (not shown) or the like by a fixture 109.

<Supply of metal materials>
Next, a method for supplying a metal material to the metal ball forming apparatus 100 will be described. 2A to 2B are schematic views showing a cross-sectional structure of the metal sphere forming apparatus 100 as viewed from the side.

  In FIG. 2A, the metal material 102 is supplied to the preparation chamber 141 as a solid. Here, a solder material will be described as an example of the metal material. However, the same applies to materials such as copper or silicon. The introduced metal material 102 is heated and melted by the heating mechanism 142 in the preparation chamber 141.

  In general electronic circuit mounting, a solder material having a composition mainly composed of tin-silver-copper is used. However, since the melting point is 221 ° C., the supplied material can be melted by heating to a temperature higher than that. Here, the figure which supplied the metal material which has a rod-shaped ingot form beforehand is shown. However, even in the ribbon-like or granular form, the molten metal material 101 is filled in the preparation chamber 141 and the supply chamber 131 by being sequentially melted by heating above the melting point, and thus can be used without any problem.

  FIG. 2B shows a state in which the metal material 102 is heated to become a molten metal material 101 and is held in the preparation chamber 141. In this state, the electromagnetic valve 143 is opened by a command from the control device 161, and the metal material 101 is introduced into the supply chamber 131.

  FIG. 2C shows a state in which the desired metal material 101 is supplied to the supply chamber 131 and the pressure chamber 121. When the volume of the supplied metal material 101 is obtained as a liquid level by the liquid level sensor 133 and reaches a desired supply amount, the electromagnetic valve 143 is closed by the instruction of the control device 161 and the supply is stopped, and the metal ball forming device 100 is stopped. Is ready for operation. In addition, the diameter of the nozzle 111 is about 1 mm at the maximum, and it is not dripped by gravity by the effect of the high surface tension which the molten metal material 101 has.

  Here, the liquid level is obtained using a liquid level sensor to obtain the volume of the metal material 101, but the liquid level can also be obtained by a temperature sensor or the like. However, since the temperature sensor is fixed to the apparatus, the obtained liquid level cannot be easily changed during operation of the apparatus. Accordingly, it is easy to flexibly cope with high-accuracy acquisition of the liquid level and change of the designated liquid level, that is, the volume, and therefore it is preferable to employ a liquid level sensor.

  Note that the molten metal material 101 is very oxidative and the state of the exposed surface is likely to change. Therefore, in the preparation chamber 141 and the supply chamber 131, it is desirable that the space where the metal material 101 is not supplied is maintained in a state where the atmosphere is replaced with an inert gas such as nitrogen.

<Drive>
Next, the drive mechanism of the metal ball forming apparatus 100 will be described. 2D, the piezoelectric element 113 is connected to the rear end portion of the piston 112 by an adhesive or a pressurizing mechanism. As a result, the thrust of the piezoelectric element 113 is transmitted to the piston 112.

  Here, when the piezoelectric element 113 is driven by the external power source 115, the operation is transmitted to the pressure chamber 121 through the piston 112. The displacement 116 of the piston 112 causes an action of increasing the pressure in the pressure chamber 121, and the pressure leads to the discharge of the molten metal material 101 from the nozzle 111 which is an open end.

  At this time, the pressure chamber 121 and the piston 112 have a gap 122 for supplying the molten metal material 101 to the pressure chamber 121. The flow path resistance of the gap 122 is larger than the flow path resistance of the nozzle 111. Therefore, the pressure in the pressure chamber 121 works for discharging the molten metal material 101 from the nozzle 111. The discharged metal material 103 becomes spherical due to its surface tension, and is cooled in the air to form solid spheres. At this time, in order to suppress oxidation of the surface of the metal material 103, it is desirable to discharge and cool in an inert gas atmosphere such as nitrogen.

<Spherical control>
Next, a spherical manufacturing method of the metal sphere forming apparatus 100 will be described. FIG. 3 is a flowchart for explaining a discharge process of the metal sphere forming apparatus 100.

  First, at the “operation start”, a “liquid level instruction” for setting a predetermined liquid level is performed. At this time, the control device 161 reads the value of the liquid level sensor 133, opens the electromagnetic valve 143 so as to obtain a desired liquid level, and supplies the molten metal material 101.

  Next, a “pressure instruction” for setting the supply chamber 131 to a predetermined pressure is performed. At this time, the controller 161 instructs the electropneumatic regulator 135 to adjust the supply chamber 131 to a desired pressure. In the present embodiment, nitrogen, which is an inert gas that can be used at low cost, is introduced into the supply chamber 131 and set.

  Here, the reason why the pressure in the supply chamber 131 changes is as follows. In the supply chamber 131, a piston 112 is inserted into a hole provided in the partition wall 136. This is secured by an O-ring. However, the supply chamber 131 is not completely sealed so as not to prevent the piston 112 from sliding. There is some nitrogen leakage. For this reason, adjustment is performed by the electropneumatic regulator 135 which is in a state where nitrogen is constantly being supplied.

  Further, a “signal voltage instruction” for setting a signal voltage for driving the piezoelectric element 113 is performed. In order to drive the piezoelectric element 113, the control device 161 instructs the external power supply 115 to output a predetermined signal voltage.

  According to the instructions of these control devices 161, the liquid level instruction of the molten metal material 101 introduced into the supply chamber 131, the pressure instruction of the supply chamber 131, and the signal voltage instruction for driving the piezoelectric element 113 are performed, whereby the metal ball The forming apparatus 100 can start an operation. Thereby, it is possible to perform a “metal material discharge” operation of discharging a certain amount of molten metal material.

  After the discharged metal material 103 flies a predetermined distance, it is spheroidized by its own surface tension to form a metal sphere 104. The ejection observation device 151 performs “acquisition of diameter” of the metal sphere 104.

  Since the ejection observation apparatus 151 has a structure for acquiring an image from the side of the metal sphere 104, the image is two-dimensional information obtained by projecting the metal sphere 104. However, the surface tension of the molten metal material 101 is as high as 500 to 600 mN / m, which is about 7 times as high as that of pure water. For this reason, it spheroidizes spontaneously so that the surface energy of the discharged metal material 101 itself is minimized, its sphericity is high, and it can be regarded as almost a sphere. Therefore, the two-dimensional projection image acquired by the ejection observation apparatus 151 can be grasped as the central cross section of the metal sphere 104, and the diameter of the metal sphere 104 can be known by obtaining the diameter of this image.

  From the above, the obtained diameter is compared with a target diameter, for example, 0.5 mm, by the control device 161, and “diameter determination” is performed.

  When the diameter of the metal sphere 104 acquired by the ejection observation device 151 exceeds the target, the control device 161 reduces the maximum voltage of the signal applied to the piezoelectric element 113. On the other hand, when it falls below, the signal voltage to the piezoelectric element 113 is controlled so as to increase the voltage. A series of operations for adjusting the diameter to a desired dimension is continuously performed. It operates to compensate for disturbances such as temperature fluctuations in the atmosphere, and a metal sphere as designed can always be formed.

  However, in actual manufacturing, relatively large fluctuations such as a change in pressure at the position of the nozzle 111 due to slight fluctuations in the remaining amount of molten metal may occur. In response to the demand for manufacturing a metal sphere having an arbitrary size, it is necessary to appropriately select and operate parameters capable of adjusting a wider range of diameters.

<Parameter control>
In addition to the driving voltage of the piezoelectric element 113, the size of the discharged metal sphere 104 varies depending on the pressure in the supply chamber 131 and the liquid level of the metal material 101.

  4A to 4C, the metal sphere corresponding to the conditions of the signal voltage output from the external power supply 115, the pressure in the supply chamber 131, and the liquid level of the metal material 101 in order to drive the piezoelectric element 113. The variable range of the diameter is shown.

  FIG. 4A is a graph showing the relationship between the diameter of the obtained metal sphere and the signal voltage applied to the piezoelectric element 113. As shown in FIG. 4A, in the signal voltage region in which data can be acquired, that is, in the signal voltage range in which ejection can be stably performed, the variable range of the diameter of the metal sphere is about ± 5% around the median value. However, since the strict control by the signal voltage is possible, the diameter can be precisely controlled despite the relatively narrow variable range.

  On the other hand, FIG. 4B is a graph showing the relationship between the diameter of the obtained metal sphere and the pressure in the supply chamber 131. As shown in FIG. 4B, in the pressure range where data can be acquired, that is, in the pressure range where ejection can be performed stably, the variable range of the diameter of the metal sphere is approximately ± 10% centered on the median value.

  Further, FIG. 4C is a graph showing the relationship between the diameter of the obtained metal sphere and the liquid level of the metal material 101. Here, the liquid level represents the height from the nozzle 111 to the liquid surface of the metal material 101.

  As shown in FIG. 4C, in the liquid level region where data can be acquired, that is, in the pressure range where stable discharge is possible, the variable range of the diameter of the metal sphere should obtain a range of ± 30% around the median. Can do. However, when the liquid level rises and falls, the liquid level fluctuates and the temperature changes, so that the control accuracy is reduced as compared with signal voltage control and pressure control.

  Here, as an example of the metal material 101, a case of solder is considered. The specific gravity of a solder material used for manufacturing a general electronic circuit is as large as 7 to 10, and the influence is expanded 7 to 10 times as compared with an ink jet system that discharges water-based ink. That is, a change of the molten solder liquid level of only 1 mm corresponds to a change of 7 to 10 mm in the case of water. When a change of 1 mm is converted into a pressure, it corresponds to a change in pressure of 0.07 to 0.1 kPa. From this, it can be seen that the capacity of the metal material, that is, the liquid level, acts as a parameter capable of controlling the diameter of the metal particles.

<Control>
Next, as an actual operation, a control procedure for the signal voltage output from the external power source 115 to drive the piezoelectric element 113, the pressure in the supply chamber 131, and the liquid level of the metal material 101 will be described. Here, a case where the diameter of the metal sphere 104 obtained from the discharge observation apparatus 151 is different from the target diameter of the desired metal particle will be described.

  When the diameter of the metal sphere 104 is different from the target value, the control device 161 performs the first to third steps below.

  As a first step, a change in the diameter of the metal particles by increasing the signal voltage to the piezoelectric element 113 will be considered. The variable range of the diameter by increasing / decreasing the signal voltage under the condition that stable ejection is ensured is as shown in FIG. 4A. When the diameter of the metal particles can be controlled within the variable range, the control device 161 instructs the external power supply 115 to change the signal voltage and gradually approach the target value. On the other hand, when the value deviates from the variable range, the diameter is not controlled by the signal voltage, and the process proceeds to the second stage.

  In the second stage, the possibility of changing the diameter of the metal particles by changing the pressure in the supply chamber 131 is determined. The variable range of the diameter by increasing and decreasing the pressure under the conditions that ensure stable discharge is as shown in FIG. 4B. In the case where the desired diameter can be controlled within the variable range, the control device 161 instructs the electropneumatic regulator 135 to change the pressure in the supply chamber 131 and gradually approach the target value. On the other hand, when the temperature deviates from the variable range, the diameter is not controlled by the pressure, and the process proceeds to the third stage.

  In the third stage, the control device 161 instructs the opening side of the electromagnetic valve 143 so that the liquid level of the metal material 101 rises, and instructs the closing side when reaching the predetermined liquid level. As a result, the liquid level of the metal material 101 is raised to increase the diameter, and asymptotically approach the target value.

  As described above, the metal sphere forming apparatus 100 can execute the control of the diameter of the metal particles in a wide range and with high accuracy by appropriately selecting the control factor for controlling the diameter of the metal particles.

  Furthermore, the control device 161 always acquires the remaining amount of the metal material 101 in the supply chamber 131 by the liquid level sensor 133, and appropriately replenishes the metal material 101 by opening the electromagnetic valve 143 for consumption of the metal material 101. To do. Thereby, the metal sphere forming apparatus 100 can continuously perform the formation of the metal sphere without stopping. Also at this time, the signal voltage and the supply chamber pressure can be controlled. The time constant of each operation is that the signal voltage change is about 1/1000 second, the pressure change is about 1 to 10 seconds, and the liquid level change of the metal material is several tens of seconds or more. This is because they do not interfere with each other and affect the operation.

  This indicates that the control of the signal voltage, the control of the supply chamber pressure, and the control of the metal material liquid level can be performed simultaneously. This is very useful in actual metal sphere manufacturing because it is possible to avoid a situation where a single factor is greatly changed.

  As described above, in the present invention, by arbitrarily controlling the voltage applied to the piezoelectric element 113, the pressure in the supply chamber 131, and the liquid level of the metal material 101, it is possible to arbitrarily set the sphere diameter and maintain the sphere diameter. Continuous production can be realized.

<Note>
In the above description, the signal voltage control, the liquid level (liquid level) control, and the pressure control are performed. However, the signal voltage control and the liquid level (liquid level) control may be used. Comparing the graphs of FIG. 4A to FIG. 4C, the signal pressure control can be included in the liquid level control capable of a wide range control and the voltage control capable of the most precise control.

  In addition, pressure control is more difficult to control with accuracy than signal voltage control and liquid level control. Therefore, two of signal voltage control and liquid level (liquid level) control may be used.

  In addition, although there is one control device 161 in the above example, it may be divided into a plurality of control devices.

  As described above, according to the present invention, when a metal material is melted and discharged to form a metal sphere, the volume can be stably manufactured. In particular, it can be continuously manufactured with high diameter accuracy.

DESCRIPTION OF SYMBOLS 100 Metal sphere formation apparatus 101 Metal material 102 Metal material 103 Metal material 104 Metal sphere 109 Fixing tool 111 Nozzle 112 Piston 113 Piezoelectric element 114 Bracket 115 External power supply 116 Displacement 121 Pressure chamber 122 Gap 131 Supply chamber 132 Heating mechanism 133 Liquid level sensor 134 Intake / exhaust pipe 135 Electropneumatic regulator 136 Bulkhead 137 Window 141 Preparation chamber 142 Heating mechanism 143 Electromagnetic valve 151 Discharge observation device 161 Control device

Claims (6)

A nozzle for discharging molten metal;
A pressure chamber that generates pressure for discharging molten metal through the nozzle;
A supply chamber for supplying the molten metal to the pressure chamber;
A detection mechanism for obtaining a capacity of the molten metal in the supply chamber;
A preparation chamber for replenishing the molten metal in the supply chamber;
A piston for pressurizing the pressure chamber;
A piezoelectric element for moving the piston;
An observation mechanism for acquiring the shape of the discharged molten metal sphere;
A first control unit that controls the amount of the molten metal in the supply chamber based on information obtained from the observation mechanism;
A second control unit that controls an operation amount of the piezoelectric element based on information obtained from the observation mechanism;
A metal ball forming apparatus including: The metal sphere forming apparatus according to claim 1, further comprising a third control unit that controls a pressure of the pressure chamber or the supply chamber based on information obtained from the observation mechanism. The metal ball forming apparatus according to claim 1, further comprising a preparation chamber for supplying the molten metal to the supply chamber. The metal ball forming apparatus according to claim 1, further comprising a pressure adjusting unit that adjusts the pressure of the supply chamber. The metal ball forming apparatus according to claim 1, further comprising a detection unit that detects an amount of the molten metal in the supply chamber. In a metal sphere forming method of forming a metal sphere by discharging a molten metal material in a container from a nozzle,
Get the shape of the ejected metal sphere,
Controlling the applied voltage to the piezoelectric element that applies pressure to the molten metal material so as to minimize the deviation from the diameter of the pre-designed metal sphere;
Furthermore, if the control range of the applied voltage is exceeded, the pressure in the container is controlled,
Furthermore, when the control range of the pressure in the said container is exceeded, the metal ball formation method which controls the liquid level in the said container of the said molten metal material.

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