Patent Publication Number: US-2015064293-A1

Title: Metal ball fabricating apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2013-0104511, filed on Aug. 30, 2013, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     FIELD OF THE INVENTION 
     One or more embodiments relate to metal ball fabricating apparatuses, and more particularly, to a metal ball fabricating apparatus for fabricating a metal ball by melting a material. 
     BACKGROUND 
     An orifice having an inner diameter of about 50 μm or less is used to fabricate a micro metal ball having size of about 100 μm, but an oxide of molten solder may block the orifice due to a small inner diameter of the orifice. 
     In many cases, a purifying operation for purifying a raw material in an alloying process is performed to solve the problem of orifice blockage. 
     However, since an oxide layer exists on a lumpy surface of a lump of a raw material generated in the alloying process, oxides may be again mixed in the molten solder, at the time of being input into fabrication equipment. 
     Therefore, there is a need to solve the problem of orifice blockage by incorporating a raw material purifying system, which is used in an alloying process, into a metal ball fabricating apparatus. 
     SUMMARY 
     One or more embodiments include metal ball fabricating apparatuses for fabricating metal balls by melting materials. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     According to one or more embodiments, a metal ball fabricating apparatus for fabricating a metal ball by melting a material includes: a fabricating unit configured to fabricate a metal ball; and a collecting unit configured to collect the metal ball, wherein the fabricating unit includes: a chamber configured to receive and store a material; a heating unit configured to apply heat to melt the material in the chamber; an orifice disposed at a lower portion of the chamber to which a metal ball droplet drops; a piston disposed over the orifice to generate a metal ball droplet; and a purifying system configured to remove a foreign substance from the material. 
     The purifying system may include a discharge pump configured to discharge a vaporized foreign substance in a heating atmosphere. 
     The purifying system may include a vacuum pump configured to adjust a vacuum level of the chamber to below about 10 −1  torr. 
     The purifying system may include a temperature control unit configured to adjust a heating atmosphere temperature of the chamber in a range of about 500° C. to about 800° C. 
     The piston and the orifice may be disposed to have a gap of about 0 mm to about 0.5 mm therebetween. 
     The fabricating unit may include a gap control unit configured to control the gap between the piston and the orifice. 
     The orifice may include a graphite material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  illustrates an overall structure of a metal ball fabricating apparatus according to an embodiment; 
         FIG. 2  illustrates a fabricating unit of a metal ball fabricating apparatus according to an embodiment; 
         FIG. 3  illustrates a graph comparing wettability test results before and after purification is performed by using a purifying system of a metal ball fabricating apparatus according to an embodiment; 
         FIG. 4  presents a table comparing wettability test results before and after purification is performed by using a purifying system of a metal ball fabricating apparatus according to an embodiment; 
         FIG. 5  illustrates a state of the material for fabricating a metal ball when the purification temperature is about 300° C. according to an embodiment; 
         FIG. 6  illustrates a state of the material for fabricating a metal ball when the purification temperature is about 800° C. according to an embodiment; 
         FIG. 7  illustrates a state of the material when the vacuum level is about 10 −1  torr according to an embodiment; 
         FIG. 8  illustrates a state of the material when the vacuum level is about 10 −3  torr according to an embodiment; 
         FIG. 9  illustrates a comparison of the test dimension and result for each material of the orifice provided in a fabricating unit of a metal ball; 
         FIG. 10A  illustrates a droplet when a metal orifice is used; 
         FIG. 10B  illustrates a droplet when a ceramic orifice is used; 
         FIG. 10C  illustrates a droplet when a graphite orifice is used; 
         FIG. 11A  illustrates a comparison between results when a metal nozzle is used; 
         FIG. 11B  illustrates comparison between results when a ceramic nozzle is used; 
         FIG. 11C  illustrates a comparison between results when a graphite nozzle is used; 
         FIG. 12  is a table illustrating an overall comparison between results when each of the vacuum level, the purification temperature, and the fabrication temperature is changed; and 
         FIG. 13  illustrates a graph comparing uniformities of metal ball sizes depending on gaps between a piston and the orifice provided in a fabricating unit of a metal ball fabricating apparatus according to an embodiment. 
         FIG. 14  presents a table comparing uniformities of metal ball sizes depending on gaps between a piston and the orifice provided in a fabricating unit of a metal ball fabricating apparatus according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Exemplary embodiments will now be described in detail with reference to the accompanying drawings. However, these embodiments are not limited thereto. 
     The effects and features of the embodiments and the accomplishing method thereof will become apparent from the following description of the embodiments, taken in conjunction with the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided such that this disclosure will be thorough and complete, and will fully convey the concept of the invention to one of ordinary skill in the art. 
     Spatially relative terms, such as “above,” “upper,” “beneath,” “below,” “lower,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation illustrated in the drawings. For example, if the device in the drawings is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “above” may encompass both an orientation of above and below. The device may be otherwise oriented (rotated about 90 degrees or at other orientations) and the spatially relative descriptors used herein may be interpreted accordingly. 
     The terminology used herein is for the purpose of describing the embodiments only and is not intended to be limiting of the embodiments. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise” and “comprising” used herein specify the presence of stated elements, steps, operations, and/or devices, but do not preclude the presence or addition of one or more other elements, steps, operations, and/or devices. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
       FIG. 1  illustrates an overall structure of a metal ball fabricating apparatus  1  according to an embodiment.  FIG. 2  illustrates a fabricating unit  10  of the metal ball fabricating apparatus  1  according to an embodiment.  FIGS. 3 and 4  illustrate a comparison between wettability test results before and after purification is performed by using a purifying system  30  of the metal ball fabricating apparatus  1  according to an embodiment.  FIGS. 5 and 6  illustrate a comparison between results when purification is performed under different purification temperatures by using the purifying system  30  of the metal ball fabricating apparatus  1  according to an embodiment.  FIGS. 7 and 8  illustrate a comparison between results when purification is performed under different vacuum levels by using the purifying system  30  of the metal ball fabricating apparatus  1  according to an embodiment.  FIGS. 9 to 11  illustrate a comparison between results when an orifice  150  provided in the fabricating unit  10  of the metal ball fabricating apparatus  1  according to an embodiment is formed of different materials.  FIG. 12  is a table illustrating an overall comparison between results when each of the vacuum level, the purification temperature, and the fabrication temperature is changed.  FIGS. 13 and 14  illustrate a comparison between uniformities of metal ball (S) sizes depending on gaps between a piston  130  and the orifice  150  provided in the fabricating unit  10  of the metal ball fabricating apparatus  1  according to an embodiment. 
     The metal ball fabricating apparatus  1  according to an embodiment is a metal ball fabricating apparatus  1  for fabricating a metal ball S by melting a material. The metal ball fabricating apparatus  1  includes: a fabricating unit  10  configured to fabricate a metal ball S; and a collecting unit  20  configured to collect the metal ball S. The fabricating unit  10  includes: a chamber  110  configured to receive and store a material; a heating unit  120  configured to apply heat to melt the material in the chamber  110 ; an orifice  150  disposed at a lower portion of the chamber  110  to which a metal ball (S) droplet drops; a piston  130  disposed over the orifice  150  to generate a metal ball (S) droplet; and a purifying system  30  configured to remove a foreign substance from the material. 
     The metal ball fabricating apparatus  1  is configured to include the fabricating unit  10  and the collecting unit  20 . 
     The fabricating unit  10  includes various devices configured to receive a material, which is a raw material of the metal ball S, and fabricate the metal ball S, and substantially constitutes a body of the metal ball fabricating apparatus  1 . The metal ball S may be a metal ball S used in a wire bonding package and may be spherical; however, embodiments are not limited thereto. 
     The material used to fabricate the metal ball may be, for example, an alloy including various metals such as copper (Cu), nickel (Ni), aluminum (Al), and cobalt (Co), and a chemical additive may be added thereto; however, embodiments are not limited thereto. 
     The material is stored in the chamber  110 . In one embodiment, the chamber  110  is configured to have a predetermined strength to endure a high temperature and a high pressure difference, and has an appropriate capacity. 
     The heating unit  120  is provided to heat the material in the chamber  110 . The heating unit  120  may heat the chamber  110  by, for example, an electrical resistance to melt the material in the chamber  110 , but its configuration and shape are not limited thereto. 
     The orifice  150  is provided at a lower portion of the chamber  110  so that the material in the chamber  110  may be heated and melted and the melted material may drop in the shape of droplets. The orifice  150  has the shape of a minute pipe and has an appropriate shape and configuration for forming a metal ball (S) droplet of a desired size and controlling the metal ball (S) droplet. Since the orifice  150  may be damaged when the melted metal ball (S) droplet drops, the orifice  150  may be attached/detached to/from the chamber  110  so that the orifice  150  may be replaced when necessary; however, embodiments are not limited thereto. The orifice  150  may be configured to include a graphite material. 
     The piston  130  is disposed over the orifice  150 . The piston  130  is spaced apart from the orifice  150  by a predetermined gap and is configured to perform a piston movement so that the melted material forms the metal ball (S) droplet. Accordingly, the piston  130  may be configured to perform a vertical piston movement, and the gap between the piston  130  and the orifice  150  and the movement period of the piston  130  may be adjusted appropriately. A power applying unit  140  may be provided so that the piston  130  may perform a piston movement. 
     The purifying system  30  is provided to remove a foreign substance from the material stored in the chamber  110 . The purifying system  30  may include a device constituting a portion of the fabricating unit  10  of the metal ball fabricating apparatus  1 . The purifying system  30  may be any member or device that may serve to remove a foreign substance from the material. It may also be understood that, when the purifying system  30  constitutes a portion of the fabricating unit  10 , the purifying system  30  may be incorporated into the fabricating unit  10  to remove a foreign substance from the material in a fabrication process. The purifying system  30  will be described later. 
     In addition to the above-described units or members, an inert gas injecting unit  160 , various pipe structures, and valve units  162  and  172  may be provided to supply an inert gas to maintain an atmosphere suitable for fabricating the metal ball S; however, embodiments are not limited thereto. 
     The collecting unit  20  is provided to collect the metal ball S fabricated by the fabricating unit  10 . The collecting unit  20  may include a collecting valve  24 , a collecting chamber  26 , and a cooling chamber  22  configured such that the metal ball (S) droplet dropping through the orifice  150  may be cooled and solidified in a dropping process. 
     The cooling chamber  22  may be extended with a vertical height such that the metal ball (S) droplet may be cooled in the dropping process. 
     The collecting chamber  24  is a member for collecting the dropped metal ball (S). A sieve may be provided in the collecting chamber  24  to load the metal ball S. The sieve may be extracted by a transport unit to discharge the metal ball S to outside. 
     The collecting unit  20  may include various transport devices for collecting the metal ball S and a valve serving to collect the metal ball S, and the configuration of the collecting unit  20  is not limited thereto. 
     Hereinafter, the purifying system  30  will be described in detail. 
     The purifying system  30  may include any device that is used to remove a foreign substance from the material and may also include any device that may serve to remove a foreign substance from the material. 
     For example, when the material is heated to a predetermined temperature to remove the foreign substance, the heating unit  120  heating the material may serve to remove the foreign substance, but the heating unit  120  may also be used to melt the material that is used to fabricate the metal ball S. As another example, a gas injecting unit and a pump serving to discharge a vaporized foreign substance may serve to remove the foreign substance and constitute a portion of the purifying system  30 . However, since the gas injecting unit and the pump may also serve to adjust an atmosphere in the chamber  110 , melt the material, and fabricate the metal ball S, they may also be included in a component other than the purifying system  30 . 
     Thus, according to some embodiments, the purifying system  30  should not be regarded as a separate device that is independent of other members or devices in the fabricating unit  10 , and may be regarded as a portion constituting the fabricating unit  10 . 
     The purifying system  30  includes a discharge pump  170  configured to discharge the foreign substance in a heating atmosphere. 
     When the chamber  110  is heated in a predetermined atmosphere to a temperature that is equal to or higher than a melting temperature, the material in the chamber  110  is melted into liquid. In this case, oxygen and a foreign substance, such as various oxides, which are contained in the liquid material, may be floated on a surface thereof, and the foreign substance may be removed by the operation of the discharge pump  170 . 
     In this case, the atmosphere in the chamber  110  may be a near-vacuum atmosphere, and the discharge pump  170  may include a vacuum pump. By the operation of the discharge pump  170 , air in the chamber  110  may flow toward the vacuum pump to be discharged to outside, and a relatively light foreign substance such as the oxide may be discharged according to the air flow. In this case, the vacuum level of the chamber  110  may be low and may be adjusted to about 2.0×10 −2  torr or less. 
     The purifying system  30  may include a temperature control unit (not illustrated) configured to adjust a heating atmosphere temperature of the chamber  110  in a range of about 500° C. to about 900° C. 
     The temperature control unit may control the operation of the heating unit  120  and adjust the temperature of the chamber  110  so that the foreign substance may be easily separated while the material is easily melted. In this case, the temperature control unit may control the temperature of the chamber  110  from about 500° C. to about 900° C., for example, or to about 800° C. Accordingly, the temperature control unit may include a temperature sensor and a control unit controlling the operation of the heating unit  120 . 
     As described above, according to the one or more of the above embodiments, since the purifying system  30  is included in the fabricating unit  10 , the metal ball fabricating apparatus  1  may fabricate the metal ball S by a pure material alone by removing a foreign substance from the material used to fabricate the metal ball S. Also, since a material purifying operation is performed in a melting process for fabrication, a separate independent purifying unit may not be necessary and the purified material may be prevented from being contaminated again by being exposed to outside when supplied into the chamber  110 . 
     Thus, the higher-quality metal ball S may be fabricated, and the efficiency of the fabrication process may be improved and the fabrication cost may be reduced, since the blockage of the orifice  150 , to which the metal ball (S) droplet drops, is prevented. 
     In one embodiment, the piston  130  and the orifice  150  are disposed to have a gap of about 0 mm to about 0.5 mm therebetween. 
     The piston  130  is spaced apart from the orifice  150  by a predetermined gap and performs a piston movement so that the melted material may drop in the form of droplets through the orifice  150 . In this case, in order to form a metal ball (S) droplet of a desired size, the piston  130  and the orifice  150  may have a gap therebetween and the gap between the piston  130  and the orifice  150  may be adjusted to about 0 mm to about 0.5 mm. Herein, the gap between the piston  130  and the orifice  150  represents a gap at which the piston  130  is advanced to maximum and is most adjacent to the orifice  150 . 
     A gap control unit  142  may be provided to adjust the gap between the piston  130  and the orifice  150 . 
     The gap control unit  142  may be provided to adjust the gap between the piston  130  and the orifice  150 , and may be, for example, a device that changes the initial position of the piston  130 . By the gap control unit  142 , the gap between the piston  130  and the orifice  150  may be changed and the size of the metal ball (S) droplet may also be changed appropriately. Thus, the metal balls S of various sizes may be fabricated according to purposes, and the general purpose of the metal ball fabricating apparatus  1  may be improved. 
     Hereinafter, the effects of the metal ball fabricating apparatus  1  according to an embodiment will be described with reference to the drawings. 
       FIGS. 3 and 4  illustrate a comparison between wettability test results before and after purification is performed by using the purifying system  30  of the metal ball fabricating apparatus  1  according to an embodiment. 
     It may be seen from  FIGS. 3 and 4  that a wetting force is increased and a zero-cross time is reduced after the purification is performed. 
     That is, the zero-cross time is the time taken to balance the water level of solder, and the zero-cross time may be short as much as possible. In one embodiment, in order to reduce the zero-cross time, the surface tension should be low. In general, as the amount of interposer in a melted metal increases, the surface tension increases and thus the zero-cross time increases. 
     According to some embodiments, the zero-cross time is reduced after the purification, and this may be regarded as the improvement of a fluid flow. Thus, it may be seen that the fluidity of the melted material passing through the hole of the orifice is improved by the purification of the material. 
     Also, as the surface tension decreases, the wetting force increases. As seen from  FIG. 4 , the increase of the wetting force after purification represents the decrease of the surface tension, and this represents the improvement of the fluidity of the material. 
       FIGS. 5 and 6  illustrate a comparison between results when purification is performed under different purification temperatures by using the purifying system  30  of the metal ball fabricating apparatus  1  according to an embodiment.  FIGS. 7 and 8  illustrate a comparison between results when purification is performed under different vacuum levels by using the purifying system  30  of the metal ball fabricating apparatus  1  according to an embodiment. 
       FIG. 5  illustrates a state of the material when the purification temperature is about 300° C., and  FIG. 6  illustrates a state of the material when the purification temperature is about 800° C. It may be seen that the oxide layer formed on the surface of the material may be further reduced in the case where the purification temperature is about 800° C., in comparison with the case where the purification temperature is about 300° C. 
       FIG. 7  illustrates a state of the material when the vacuum level is about 10 −1  torr, and  FIG. 8  illustrates a state of the material when the vacuum level is about 10 −3  torr. It may be seen that the oxide layer formed on the surface of the material may be further reduced in the case where the vacuum level is about 10 −3  torr, in comparison with the case where the vacuum level is about 10 −1  torr. 
     As described above, it may be seen that the purification of the material is further improved by the removal of the oxide when the material is melted while the high temperature and the low vacuum level are maintained. 
       FIGS. 9 to 11  illustrate a comparison between results when the orifice  150  provided in the fabricating unit  10  of the metal ball fabricating apparatus  1  according to an embodiment is formed of different materials. 
       FIG. 9  illustrates the test dimension and result for each material of the orifice  150 ,  FIG. 10  illustrates each orifice  150 , and  FIG. 11  illustrates the uniformity of droplets generated through each orifice  150 . 
       FIG. 10A  illustrates a droplet when a metal orifice  150  is used,  FIG. 10B  illustrates a droplet when a ceramic orifice  150  is used, and  FIG. 10C  illustrates a droplet when a graphite orifice  150  is used. 
     It may be seen from  FIGS. 9 to 11  that, when the orifice  150  is formed of graphite having excellent slippage characteristics, most stable and uniform droplets are formed even when a small orifice  150  is used. 
       FIG. 12  is a table illustrating an overall comparison between results when the vacuum level, the purification temperature, and the fabrication temperature are changed. It may be seen from  FIG. 12  that the fabrication result is varied when each of the vacuum level, the purification temperature, and the fabrication temperature is changed. 
       FIGS. 13 and 14  illustrate a comparison between uniformities of metal ball (S) sizes depending on gaps between the piston  130  and the orifice  150  provided in the fabricating unit  10  of the metal ball fabricating apparatus  1  according to an embodiment. 
     As illustrated in  FIGS. 13 and 14 , it may be seen that the size of the fabricated metal ball S and the deviation of the size increase as the gap between the piston  130  and the orifice  150  increases in the piston movement having the same frequency. 
     As described above, since the gap control unit  142  is provided to adjust the gap between the piston  130  and the orifice  150 , the gap between the piston  130  and the orifice  150  may be adjusted, and the piston  130  and the orifice  150  may be adjusted to have an optimum gap therebetween in the fabrication process. Therefore, the metal balls S may be fabricated to have a uniform size. 
     As described above, according to the one or more of the above embodiments, since the purifying system  30  is included the fabricating unit  10 , the metal ball fabricating apparatus  1  may fabricate the metal ball S by a pure material alone by removing a foreign substance from the material used to fabricate the metal ball S. Also, since a material purifying operation is performed in a melting process for fabrication, a separate independent purifying unit may not be necessary and the purified material may be prevented from being contaminated again by being exposed to outside when supplied into the chamber  110 . 
     Thus, the higher-quality metal ball S may be fabricated, and the efficiency of the fabrication process may be improved and the fabrication cost may be reduced, since the blockage of the orifice  150 , to which the metal ball (S) droplet drops, is prevented. 
     Also, since the gap control unit is provided to adjust the gap between the piston  130  and the orifice  150 , the gap between the piston  130  and the orifice  150  may be changed and the size of the metal ball (S) droplet may also be changed appropriately. Thus, the metal balls S of various sizes may be fabricated according to purposes, and the general purpose of the metal ball fabricating apparatus  1  may be improved. 
     Also, even when a small orifice including a graphite material is used, stable and uniform metal ball droplets may be formed. 
     It should be understood that the exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. 
     While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.