Abstract:
A solder ball dispenser ( 100 ) has feeder unit and head unit chambers ( 200, 300 ) and a pneumatic singulator ( 370 ). Solder balls ( 101 ) are put into motion in the chambers by moving air. The pneumatic singulator and a channel for solder balls are formed, machined or molded in a head plate ( 142 ) of a dispenser and enclosed by a front plate ( 141 ) and a back plate ( 143 ) secured adjacent to the head plate. The solder ball dispenser receives a continuous supply of unorganized solder balls and arranges them in a single stack ( 340 ). The pneumatic singulator ejects the balls one at a time to a target device such as a Ball Grid Array (BGA). The dispenser has a plurality of conduits ( 331 - 338 ) for applying one of air pressure and vacuum to various points of the chambers and the channel. Solder balls are transported through the dispenser and ejected from the dispenser by the programmed application of air pressure and vacuum. The trajectory of each solder ball is stopped before moving to a next position in the pneumatic singulator. No solid object causes solder balls to move within the dispenser or to be ejected from the dispenser.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to the field of metal fusion bonding, and more particularly, to preplacing a quantity of unfused solid filler onto a target device, such as a Ball Grid Array (BGA), prior to applying fusing heat and prior to juxtaposing parts to be joined. The unfused solid filler has a particular size and shape, more specifically, that of a solder ball.  
           [0003]    2. Description of the Related Art  
           [0004]    Devices that dispense solder balls through mechanical means are well known. Solder balls are used for attaching BGAs to printed circuits. For BGAs, a typical solder ball has a diameter of 30 mils. Solder balls are also used for attaching flip chips to integrated circuit packages. For flip chips, a typical solder ball has a diameter of 10-20 mils. As microelectronics become smaller, the size of solder balls for such microelectronics also becomes smaller.  
           [0005]    Disadvantageously, all known prior art solder ball dispensing devices use, at least in part, mechanical parts such as levers, to transport solder balls through the prior art devices and/or to eject them out of the prior art devices. Known dispensing devices have a problem of solder balls sticking to mechanical parts that move the solder balls through such dispensing devices, thereby jamming the dispensing device. A solder ball sticks to a mechanical part as a result of a cold weld bond to a metallic component or as a result of static electricity. As solder balls become smaller, the probability of a cold weld bond of a solder ball to a metallic component occurring becomes greater. As solder balls become smaller, the effect of static electricity on the solder balls becomes more pronounced.  
           [0006]    As solder balls become smaller, the levers that move the solder balls have to be machined to higher tolerances, thereby making them more expensive. When a dispensing device has a plurality of small mechanical parts that work together, their tolerances are cumulative, thereby disadvantageously requiring even higher tolerances. Also, as levers become smaller, the lack of strength of the levers becomes a problem. Furthermore, proportionately scaled down versions of devices, such as solenoids, which actuate levers, are not always available.  
           [0007]    Most known prior art solder ball dispensing devices utilize solely mechanical parts; however, a few known dispensing devices utilize, in part, gas pressure and vacuum to move solder balls through the device. Examples such of known devices are:  
           [0008]    U.S. Pat. No. 5,279,045, issued Jan. 18, 1994, to Odashima et al., entitled Minute Particle Loading Method and Apparatus uses a fluid to stir up minute particles in an enclosed space. However, Odashima, et al., has no provision for dispensing solder balls one at a time.  
           [0009]    U.S. Pat. No. 5,431,332, issued Jul. 11, 1995, to Kirby et al., entitled Method and Apparatus for Solder Sphere Placement Using an Air Knife directs a column of air across a surface of a stencil to remove excess solder balls. However, Kirby, et al., has no provision for dispensing solder balls one at a time.  
           [0010]    U.S. Pat. No. 5,626,277, issued May 6, 1997, to Kawada entitled Mounting Apparatus of Solder Balls has a ball suction jig that uses vacuum for collecting solder balls and a blow gas for agitating solder balls in a ball feed jig. However, Kawada has no provision for dispensing solder balls one at a time.  
           [0011]    U.S. Pat. No. 5,878,911, issued Mar. 9, 1999, to Lin et al., entitled Solder-Ball Supplying Apparatus discloses vacuum means used to suck out a preset amount of solder balls from a storage tank. However Lin et al., uses a valve to control the flow of solder balls through the apparatus.  
           [0012]    U.S. Pat. No. 6,003,753, issued Dec. 21, 1999, to Hwang et al., entitled Air-Blow Solder Ball Loading System for Micro Ball Grid Arrays applies fluid pressure to solder balls within a tub to force the solder balls to float on gas pressure toward a vacuum head that includes vacuum apertures for picking up solder balls from the tub. However, Hwang et al., has no provision for dispensing solder balls one at a time.  
           [0013]    U.S. Pat. No. 6,182,356, issued Feb. 6, 2001, to Bolde entitled Apparatus for Solder Ball Mold Loading has an air supply line connected to a reservoir and blowing air onto solder balls in the reservoir to break up accumulation of solder balls at the bottom of the reservoir, and a vacuum for facilitating reception of the solder balls into cavities of a mold. However, Bolde accomplishes dispensing of individual solder balls by mechanical movement of a feeder exit port across the mold.  
           [0014]    U.S. Pat. No. 6,227,437, issued May 8, 2001, to Razon et al., entitled Solder Ball Delivery and Reflow Apparatus and Method of Using the Same uses a pressurized fluid that is introduced into a reservoir to urge a continuous flow of solder material through a feed tube from the reservoir to a capillary. The capillary deposits one solder ball at a time onto a substrate. However, the capillary uses a mechanical indexing slide mechanism to select one solder ball at a time.  
           [0015]    U.S. Pat. No. 6,244,788, issued Jun. 12, 2001, to Hernandez entitled Apparatus for Supplying Solder Balls uses a fluid to actuate a continuous flow of solder balls from a reservoir to a receptacle. However, Hernandez does not disclose dispensing solder balls one at a time.  
           [0016]    U.S. Pat. No. 6,325,272, issued Dec. 4, 2001, to May et al., entitled Apparatus and Method for Filling a Ball Grid Array uses air to force solder balls into and out of holes of a BGA template. However, May et al., does not disclose any method or apparatus for transferring solder balls to the BGA template.  
           [0017]    U.S. patent application Publication No. 2002/0088843 A1, by Saso, published Jul. 11, 2002, entitled Solder Ball Pitcher is a device for supplying a series of individual solder balls in which solder balls are moved by solid mechanical components which also move. However, Saso does not disclose movement of solder balls as a result of application of vacuum or air pressure.  
           [0018]    U.S. patent application Publication No. 2002/0135064 A1, by Hazeyama et al., published Sep. 26, 2002, entitled Transfer Apparatus for Arraying Small Conductive Bumps on Substrate and/or Chip has a vacuum source, and a pallet for holding solder balls in a same pattern as a pattern of conductive pads on a semiconductor chip, and uses air to push the array of conductive balls sidewards and to make the array of conductive balls float from the pallet to the semiconductor chip. However, Hazeyama et al., does not disclose any method or apparatus for transferring solder balls to the array.  
           [0019]    Thus, what is needed is a solder ball dispenser for dispensing solder balls to BGAs, which overcomes the disadvantages of the prior art by using only air pressure and vacuum to move solder balls through the solder ball dispenser. What is also needed is a solder ball dispenser for dispensing solder balls to BGAs that can be easily scaled down to dispense smaller solder balls to flip chips.  
         SUMMARY OF THE INVENTION  
         [0020]    Briefly described, and in accordance with a preferred embodiment thereof, the present invention relates to an apparatus for dispensing a series of single solder balls, which includes a curved chamber for containing a multiplicity of solder balls set in motion by gas flowing within the curved chamber, an elongate chamber having a first end and a second end, and an ejector connected to the second end of the elongate chamber. The first end of the elongate chamber connected to the curved chamber for receiving solder balls from the curved chamber. The elongate chamber is sized to accept a single line of solder balls. The ejector receives the single line of solder balls and, in response to application of gas pressure and vacuum on the solder balls, dispenses a series of single solder balls. All movement of solder balls within the apparatus is caused only by application of gas pressure and vacuum.  
           [0021]    The present invention also relates to an apparatus for dispensing a series of single solder balls, which includes a substantially circular chamber having a depth of approximately the diameter of the solder balls. The chamber has an opening for delivering blowing gas into the chamber for setting the solder balls within the chamber in motion, and a buffer chute for allowing one solder ball at a time to escape, against gravity, from the chamber as a result of the motion of the one ball, and for temporarily storing a single line of solder balls from which the balls are dispensed.  
           [0022]    The present invention further relates to an apparatus for dispensing a series of single solder balls. The apparatus includes an elongate chamber holding a single line of solder balls, and a pneumatic singulator connected to the elongate chamber. The pneumatic singulator receives the single line of solder balls. The pneumatic singulator has a channel for the balls. The channel has a plurality of openings for application of cycles of alternate gas pressure and vacuum to the channel. Each half cycle causes at least one solder ball from the single line of solder balls to move from one of the plurality of openings to another of the plurality of openings.  
           [0023]    The present invention further relates to an apparatus for ejecting a series of single solder balls, which includes an elongate chamber holding a single line of solder balls and also includes a pneumatic singulator connected to the elongate chamber. The pneumatic singulator receives the single line of solder balls. The pneumatic singulator has a channel for the balls. The channel has a plurality of bends. The channel has a plurality of openings at which one of gas pressure and vacuum is applied to move solder balls through the channel. The balls pause at each bend of the channel prior to being ejected one at a time from the apparatus.  
           [0024]    The present invention further relates to a method of organizing solder balls into a single line, which includes the steps of swirling a multiplicity of solder balls in a first curved chamber that has a size substantially larger than a solder ball diameter in all three dimensions; transferring at least some of the multiplicity of solder balls into a second chamber that has a size substantially larger than a solder ball diameter in only two dimensions and a size approximately of a solder ball diameter in the third dimension; swirling the at least some of the multiplicity of solder balls in the second curved chamber; and transferring a plurality of the at least some of the multiplicity of solder balls into an elongate chamber that has a size substantially larger than a solder ball diameter in only one dimension and a size approximately of a solder ball diameter in two dimensions.  
           [0025]    The present invention further relates to a method of dispensing solder balls that comprises the steps of (a) receiving a single line of solder balls; (b) transferring each solder ball from the single line of solder balls into a pneumatic singulator; (c) moving each solder ball through the pneumatic singulator using only vacuum and gas pressure; (d) causing each solder ball to pause at least two times while moving through the pneumatic singulator; (e) causing each solder ball to change trajectory by at least 45° after each pause; and (f) ejecting, one at a time, each solder ball out of the pneumatic singulator.  
           [0026]    The present invention further relates to a method of dispensing solder balls that comprises the steps of (a) swirling a multiplicity of solder balls in a first curved chamber, in which the first curved chamber has a size substantially larger than a solder ball diameter in all three dimensions; (b) transferring at least some of the multiplicity of solder balls into a second chamber, in which the second chamber has a size substantially larger than a solder ball diameter in only two dimensions and having a size approximately of a solder ball diameter in the third dimension; (c) swirling the at least some of the multiplicity of solder balls in the second curved chamber; (d) transferring a plurality of the at least some of the multiplicity of solder balls into an elongate chamber, in which the elongate chamber has a size substantially larger than a solder ball diameter in only one dimension and has a size approximately of a solder ball diameter in two dimensions; (e) transferring the plurality of the at least some of the multiplicity of solder balls into a pneumatic singulator; and (f) ejecting, one at a time, each solder ball of the plurality of the at least some of the multiplicity of solder balls out of the pneumatic singulator. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]    The present invention will be described with greater specificity and clarity with reference to the following drawings, in which:  
         [0028]    [0028]FIG. 1 is a perspective view of a solder ball dispenser in accordance with the invention;  
         [0029]    [0029]FIG. 2 is a perspective view of a feeder unit and a head unit of the solder ball dispenser of FIG. 1;  
         [0030]    [0030]FIG. 3 is a more detailed perspective view of the feeder unit;  
         [0031]    [0031]FIG. 4 is a front view of the feeder unit;  
         [0032]    [0032]FIG. 5 is a side view of the feeder unit;  
         [0033]    [0033]FIG. 6 is a cross-sectional view through cut-line BB of FIG. 4 showing solder balls;  
         [0034]    [0034]FIG. 7 is a cross-sectional view through cut-line AA of FIG. 5 showing the solder balls;  
         [0035]    [0035]FIG. 8 is another cross-sectional view through cut-line AA of FIG. 5 showing the solder balls in motion;  
         [0036]    [0036]FIG. 9 is a front view of a head plate of the head unit;  
         [0037]    [0037]FIG. 10 is a top view of the head plate;  
         [0038]    [0038]FIG. 11 is a side view of the head plate;  
         [0039]    [0039]FIG. 12 shows the feeder unit and the head unit and a multiplicity of solder balls moving from the feeder unit to the head unit;  
         [0040]    [0040]FIG. 13 shows the feeder unit and the head unit and a multiplicity of solder balls in a head unit chamber of the head unit;  
         [0041]    [0041]FIG. 14 shows the feeder unit and the head unit and a multiplicity of solder balls swirling in the head unit chamber;  
         [0042]    FIGS.  15 - 25  are enlarged views of an ejection area of FIG. 12 showing a pneumatic singulator at various stages of dispensing;  
         [0043]    [0043]FIG. 26 is an enlarged view of the ejection area showing a path through the pneumatic singulator;  
         [0044]    [0044]FIG. 27 is an exploded view of the head unit;  
         [0045]    [0045]FIG. 28 is a perspective view of a manifold assembly of the solder ball dispenser; and  
         [0046]    [0046]FIG. 29 is a functional electrical block diagram for controlling the manifold assembly. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0047]    [0047]FIG. 1 is a perspective view of a solder ball dispenser  100  that receives a disorganized supply of solder balls, or balls,  101  and dispenses them one at a time, solely through application of air pressure and vacuum. The solder ball dispenser, or dispenser,  100  comprises a feeder unit  104  and a head unit  108 , mounted on a frame  103 . The frame  103  is mounted to a base  105 . A reservoir (not shown) of balls is under the frame  103 . An x-y table  110  is mounted to the base  105 . A platform  112  is attached to the x-y table  110  and moves with the x-y table. Three BGAs  120  are shown on the platform  112 . The x-y table  110  is in a position such that one of the BGAs  120  is under the head unit  108  and is only partially visible. When the dispenser  100  is operating, the x-y table  110  moves the BGA  120  that is a current target device to a plurality of positions under the head unit  108  while balls  101  are ejected from the head unit.  
         [0048]    [0048]FIG. 2 is a perspective view of the feeder unit  104  attached to the head unit  108 . The feeder unit  104  is assembled from a plurality of flat plates, preferably six flat plates  131 - 136 , secured together by means such as bolts through a set of holes  137 . The head unit  108  is assembled from a plurality of flat plates, preferably seven flat plates  141 - 147 , secured together by means such as bolts through a set of holes  138 . The seven flat plates of the head unit  108  comprise a front plate  141 , a head plate  142 , a back plate  143 , an interface housing  144 , a Universal Serial Bus (USB) housing  145 , a USB controller board assembly  146  and a head mount  147 . The material of the plates  131 - 136  and  141 - 147  is preferably metal, for durability; however, the plates have been made from plastic which has the advantage of being transparent and allowing the balls  101  within the dispenser  100  to be readily seen. On a top side of the head unit  108  are a test button  150 , two controller status Light-Emitting Diodes (LEDs)  151 - 152 , a controller reset button  153 , a USB connector  154  and solenoid power connector  155 . Eight solenoid LEDs  161 - 168  are mounted on a right side of the head unit  108 . Advantageously, the dispenser  100  is easily cleaned by separating the plates  131 - 136  and  141 - 147 , thereby allowing any balls to easily come out of the dispenser.  
         [0049]    [0049]FIG. 3 is a more detailed perspective view of a feeder unit  104  of the dispenser  100 . Shown in dotted lines in FIG. 2 is a feeder unit chamber  200  that is hollowed out within the feeder unit  104 . The feeder unit chamber  200  is formed by the removal of material from at least flat plates  133  and  134 . The feeder unit chamber  200  has the general shape of two adjacent cones with truncated tips. The feeder unit  104  has an opening  206  for acceptance of balls into the feeder unit chamber  200 .  
         [0050]    [0050]FIG. 4 is a front view of the feeder unit  104 . The opening  206  is on a front side  205  of the feeder unit  104 . A tubular pathway  207  extends from the opening  206  to a portion of the feeder unit chamber  200  that is nearest the front side  205 . The feeder unit chamber  200  has a maximum diameter  204 . Referring back to FIG. 1, connecting portion  122  extends from the opening  206  to the reservoir of balls located under the feeder unit  104 . Within the connecting portion  122  is a second pathway (not shown) that transports balls from the reservoir to the feeder unit  104 . Referring again to FIG. 4, the feeder unit  104  has an opening  208  for expulsion of balls from the feeder unit. An inclined pathway  209  extends from the feeder unit chamber  200  to the opening  208 . The inclined pathway  209  is aligned with the intersection of the two cones-shaped sections of the feeder unit chamber  200 ; that is, the inclined pathway is aligned with the widest portion of the feeder unit chamber. The inclined pathway  209  forms an exit slot  210  that extends from point A  211  to point B  213  at the intersection of the two cones-shaped sections of the feeder unit chamber  200  for balls  101  leaving the feeder unit chamber  200 . The inclined pathway  209  has a width  212  which is greater than a plurality of solder ball diameters. The inclined pathway  209  and has a depth (not shown) of approximately 30% greater than a solder ball diameter. The dispenser  100  in accordance with the invention is designed for balls having a nominal diameter of 30 mils (30 thousandths of an inch). Because balls having a nominal diameter of 30 mils are commercially available in tolerances of ±30%, thereby yielding balls having diameters of 21-39 mils, the depth of the inclined pathway  209  is preferably 40 thousandths of an inch. Therefore, the depth of the inclined pathway  209  is large enough for the largest expected ball  101 , but too small for two of even the smallest expected balls. However, a plurality of balls  101  can travel through the inclined pathway  209  adjacent to each other in a line defining the width  212  of the inclined pathway. The inclined pathway  209  is in a same plane as the intersection of the two cone-like portions of the feeder unit chamber  200 . The feeder unit chamber  200  has a bottom  220  at which there is a narrow opening (not shown) to a first void  225 . The narrow opening has a length extending from point C  221  to point D  222 . The narrow opening is shaped somewhat like a slit at the bottom portion of the intersection of the two cone-like portions of the feeder unit chamber  200 . The first area  225  has a port  230  from which air, preferably ionized air, enters under pressure for selected periods. Alternatively, another gas is used.  
         [0051]    [0051]FIG. 5 is a side view of the feeder unit  104 . The narrow opening at the bottom  220  of the feeder unit chamber  200  has a width of less than the diameter of one ball. The width is less than the diameter of one ball in order to prevent a ball from falling into the first area  225 . A conduit  232  extends from port  230  through the feeder unit  104  to an outside port  234  on a back wall  235  of the feeder unit. The conduit  232  is connected, via the outside port  234 , to a switchable source of air pressure (not shown). The switchable source of air pressure is selectively switched on producing air pressure, or switched off to a neutral state producing neither air pressure nor vacuum. For purposes of explanation, unless otherwise stated, it is assumed that the switchable source of air pressure is off.  
         [0052]    A second void  240  extends from an opening  241  on the back wall  235  of the feeder unit  108  to a side of the feeder unit chamber  200  nearest the back wall. The feeder unit chamber  200  has a depth  251 . A screen, or mesh,  242  is mounted among the second void  240  and the feeder unit chamber  200 . Opening  241  is for connection to a selective switchable source of vacuum. Neither the switchable source of vacuum, nor a connection from opening  241  to the switchable source of vacuum, is shown. The mesh  242  allows the vacuum at opening  241  to reach the feeder unit chamber  108 ; however, the mesh has openings smaller than the diameter of a ball. Therefore, balls in the feeder unit chamber  104  will not be sucked into the void  240  when the switchable source of vacuum is turned on. The switchable source of vacuum connected to opening  241  is selectively switched on producing vacuum, or switched off to a neutral state producing neither air pressure nor vacuum. For purposes of explanation, unless otherwise stated, it is assumed that the switchable source of vacuum is off.  
         [0053]    [0053]FIG. 6 is a cross-sectional view through cut-line BB of FIG. 4, which shows a multiplicity of balls  101  at the bottom of the feeder unit chamber  200 . This multiplicity of balls was sucked into feeder unit chamber  200  by application of vacuum at opening  241  as a result of the switchable source of vacuum being turned on. The application of vacuum caused balls in the reservoir to travel through the second tubular pathway of connecting portion  122 , through opening  206  and through tubular pathway  207  prior to entering the feeder unit chamber  200 . Mesh  242  stopped the balls from entering void  240 . The balls  101  are stored in the reservoir in a disorganized manner, and the balls randomly enter the feeder unit chamber  200 . FIG. 6 shows the balls at rest after the switchable source of vacuum connected to opening  241  is turned off The balls  101  in the feeder unit  104  are ready to load the head unit  108 .  
         [0054]    [0054]FIG. 7 is a cross-sectional view through cut-line AA of FIG. 5 showing the same multiplicity of balls  101  at rest as is shown in FIG. 6. The balls  101  in the feeder unit  104  are ready to load the head unit  108 . Except for being contained within the feeder unit chamber  200 , the balls  101  remain disorganized in FIGS. 6 and 7.  
         [0055]    [0055]FIG. 8 is another cross-sectional view through cut-line AA of FIG. 5, which shows a plurality of balls  101  in a general counterclockwise movement within the feeder unit chamber  200 , as indicated by arrow  270 . This movement is caused by the switchable source of air pressure being turned on, thereby producing air pressure which is conveyed via conduit  232  into first void  225 , through port  230 . The air pressure in conduit  232  is indicated by crosshatching at port  230 . The air pressure is conveyed from first void  225  to the feeder unit chamber  200  via the narrow opening, or slit, between the two somewhat conical portions of the feeder unit chamber  200 . Air pressure emanating from port  230  causes the balls  101  to move in a counter clockwise rotation. The balls  101  that have a trajectory coincident with the exit slot  210  will travel up the inclined pathway  209 ; the balls that do not travel up the inclined pathway, recirculate for another try. Advantageously, pileups of balls  101  at the exit slot  210  are avoided by recirculating of the balls and by gravity.  
         [0056]    [0056]FIG. 9 is a front view of a head plate  142  of the head unit  108 , The head plate  142  includes a head unit chamber  300  for holding balls  101 . The head unit chamber  300  is formed by a void within the head plate  142 . The front view of the head unit chamber  300  has a general shape of an annular ring. The head plate  142  has an entrance  304  for balls  101 . A declined ramp  306  for balls  101  extends from the entrance  304  to the head unit chamber  300 . When the balls  101  are in movement, they swirl within the head unit chamber  300 . The head unit chamber  300  is formed by removal of the material of the head plate  142  on the surface of the head plate facing the front plate  141 . A front plate  141  and a back plate  143  form the front and back boundaries, respectively, of the head unit chamber  300 . The head unit chamber  300  has an exit  312  for the balls  101  near the top of the head unit chamber  300 . A buffer chute  320  has an entrance  313 , and extends from the exit  312  of the head unit chamber  300  to an ejection area  271  of the head plate  142 . The buffer chute  320  is a long narrow, or elongate, chamber formed by removal of the material of the head plate  142  on the surface of the head plate facing the front plate  141 . The buffer chute  320  has the general shape of a curved tube or pipeline. However, the buffer chute  320  is not limited to being an elongate cylinder; it is alternatively an elongate parallelpiped. The buffer chute has a width  321  of approximately 130% of a ball diameter. The front plate  141  functions as a cover for the head unit chamber  300  and for the buffer chute  320 . The head unit chamber  300  has an outer diameter  308  that is greater than one hundred times that of a diameter of a ball  101 . The head unit  108  has a set of eight conduits, C 1 -C 8 ,  331 - 338  for conducting air pressure and vacuum from a manifold  180  (see FIG. 27) to locations at the head plate  142 . The conduits extend through the back plate  143 . Preferably, conduits C 1 -C 8 ,  331 - 338  have either air pressure or vacuum in them; that is, they are never switched to a neutral state. For purposes of explanation, it is assumed all conduits C 1 -C 8 ,  331 - 338  have vacuum in them unless stated otherwise. Conduit C 8   338  terminates at a location  360  near the top of the declined ramp  306 . Advantageously, the declined ramp  360 , buffer chute  320 , head unit chamber  300  and other paths that the balls take are integrated into a single plate, such as the head plate  342 , to minimize fabrication and assembly tolerances of the dispenser  100 , which is critical when dispenser dimensions are for smaller balls  101 . The lack of mechanical parts, such as levers, to move balls  101 , allows the design of the dispenser  100  to be easily scalable for different size balls. To change the scale of the dispenser  100  in accordance with the invention, only the size of the path through which the balls  101  travel need be changed.  
         [0057]    [0057]FIG. 10 is a top view of the head unit  108 , and FIG. 11 is a side view of the head unit. The head unit chamber  300  has a depth  310  of about 30% greater than a ball diameter. Therefore, the depth  310  of the head unit chamber  300  is larger enough for the largest expected ball  101 , but too small for more than one of the smallest expected balls. However, a plurality of balls  101  can fit into the head unit chamber  300  adjacent to each other radially or circumferentially.  
         [0058]    FIGS.  12 - 14  show the connection between the feeder unit  104  and the head unit  108 , and demonstrates a sequence of steps for loading the head unit  108  with balls  101  from the feeder unit  104 . The feeder unit  104  is attached to the head unit  108  such that the opening  208  of the feeder unit  104  connects with the entrance  304  at the head plate  142  of the head unit. It should be noted that both the maximum diameter  204  of the conical-like portions of the feeder unit chamber  200  and the depth  251  of the feeder unit chamber have a size of greater than one hundred ball diameters. As a result, the feeder unit chamber  200  is substantially larger in size than a ball diameter, by a factor of at least one hundred, in all three dimensions. Therefore, balls  101  in the feeder unit chamber  200  can move in all three directions.  
         [0059]    It is important to note that while the outer diameter  308  of the head unit chamber  300  has a size of greater than one hundred. ball diameters, the depth  310  of the head unit chamber has a size of only 130% of a ball diameter. Therefore, the head unit chamber  300  is substantially larger than a ball diameter, by a factor of at least one hundred, in only two of the three dimensions. Consequently, balls  101  in the head unit chamber  300  can only move in two directions in any substantial amount. As a result, balls  101  that have traveled from the feeder unit chamber  200  to the head unit chamber  300  have advantageously had their freedom of movement reduced from three dimensions to virtually two dimensions. Accordingly, at least some of the multiplicity of balls  101  within the dispenser  100  have become more organized.  
         [0060]    [0060]FIG. 12 shows the head unit chamber  300  receiving balls  101 . A multiplicity of balls  101  that were originally at rest at the bottom of the feeder unit chamber  200  are indicated by balls drawn in dotted lines. Thereafter, air is emitted from port  230  of the feeder unit  104 , as indicated by the crosshatching of port  230 , thereby producing an air jet  226  emanating from area  225 , through the narrow opening, and into the bottom  220  of the feeder unit chamber  200 . A vacuum is present in conduit C 8   338 . FIG. 12 shows the feeder unit  104  and the head unit  108  and a single layer of balls  101  moving from the feeder unit  104  to the head unit  108  through the inclined pathway  209  of the feeder unit  104  and the, declined ramp  306  of the head unit  108 . The vacuum in conduit C 8   338  and the air pressure in conduit  232  cooperate to cause the balls  101  to travel from the feeder unit chamber  200  to the head unit chamber  300 . The balls in the inclined pathway  209  of the feeder unit  104  and the declined ramp  306  of the head unit  108  are in a single layer because the depths of the inclined pathway and declined ramp are less than the diameters of two balls.  
         [0061]    [0061]FIG. 13 shows the feeder unit  104  and the head unit  108  and a plurality of balls  101  at the bottom  301  of the head unit chamber  300 . Air is no longer being emitted from port  230  of the feeder unit  104  because the air pressure in conduit  232  has been switched off. The vacuum in conduit C 8   338  remains. Balls at the bottom  220  of the feeder unit chamber  200  are shown in dotted lines to indicate whence the balls came. FIG. 13 shows an idealized operation by which all the balls that had been in the feeder unit chamber  200  are transferred to the head unit chamber  300 . However, it is not necessary for the proper operation of the dispenser  100  that all the balls in the feeder unit chamber  200  be transferred to the head unit chamber  300 —only some of the balls need be transferred. The balls  101  in the head unit  108  are at rest and are ready to load the buffer chute  320 . FIG. 13 shows a ready state of the dispenser  100 . The dispenser  100  is at the beginning of an ejection cycle.  
         [0062]    [0062]FIG. 14 shows the feeder unit  104  and the head unit  108  and a plurality of balls  101  swirling in the head unit chamber  300 . In FIGS.  14 - 25 , air pressure in one or more of the conduits C 1 -C 8 ,  331 - 338  is indicated by crosshatching; conduits having vacuum do not have crosshatching. FIG. 14 shows the buffer chute  320  being filled with balls  101 . Port C 7   337  is pressurized, thereby creating an air jet  365  that moves the balls  101  in the head unit chamber  300  in a counter clockwise rotation as indicated by arrow  350 . Balls that have a trajectory coincident with the entrance  313  of the buffer chute  320  will enter the buffer chute as indicated by arrow  355 . Balls that do not enter the buffer chute  320 , recirculate within the head unit chamber  300  and may enter the buffer chute later. Pileups at the entrance  313  of the buffer chute  320  are avoided by recirculating of the balls  101  and by gravity. Port C 8   338  is pressurized to clear the entrance  304  to the head unit  108  and to prevent the circulating balls  101  in the head unit chamber  300  from back-flowing into the feeder unit chamber  200 . A single vertical column, or stack,  340  of balls is shown at the bottom of the buffer chute  320 , having traveled there from the head unit chamber  300 . The bottom of the buffer chute  320  connects with a pneumatic singulator  370  in the ejection area  271 .  
         [0063]    It is important to note that while the length of the buffer chute  320  has a size of greater than one hundred ball diameters, the width  321  of the buffer chute has a size of only 130% of a ball diameter. Therefore, the buffer chute  320  is substantially larger than a ball diameter, by a factor of at least one hundred, in only one of the three dimensions. Consequently, balls  101  in the buffer chute  320  can only move in one direction in any substantial amount. As a result, balls  101  that have traveled from the head unit chamber  300  to the buffer chute  320  have advantageously had their freedom of movement reduced from two dimensions to virtually one dimension. Accordingly, a plurality of the at least some of the multiplicity of balls  101  within the dispenser  100  have become still more organized.  
         [0064]    FIGS.  15 - 25  are enlarged views of the ejection area  271  of the head unit  108  showing the pneumatic singulator  370  of the dispenser  100  at various stages of dispensing balls  101 . Referring now specially to FIG. 15, the pneumatic singulator  370  comprises a pathway for balls with a plurality of mechanical stops, or stops. Preferably, there are four stops  341 - 344 . Advantageously, the pathway of the pneumatic singulator  370  bends at least 45° at each stop  341 - 344 . At each stop  341 - 344  is an orifice  351 - 354  of one of the conduits C 1 -C 4 ,  331 - 334 . The pathway, which is part of the operating channel, or channel for ball travel, of the dispenser  100 , is sized to accept only one ball  101  at a time. Within the pneumatic singulator  370 , the balls  101  pass any one point on the pathway serially. A ball  101  traversing the pneumatic singulator  370  advantageously pauses at each stop  341 - 344 , partly as a result of encountering a wall of the pathway within the pneumatic singulator  370  and partly as a result of selective application of air pressure and vacuum within each of the conduits  331 - 334 , in accordance with the invention.  
         [0065]    FIGS.  15 - 25  shows a sequence of steps for loading the pneumatic singulator  370  and for dispensing one ball  101  at a time, using, as an example, only nine balls in the buffer chute  320 . In actual operation, the buffer chute  320  has many more than nine balls in it. For explanatory purposes, the balls are labeled A-I. FIG. 15 shows balls A-I at the bottom of the buffer chute  320  that are ready to be loaded into the pneumatic dispenser  370 . Conduit C 5 ,  335  (see FIG. 14) is pressurized to help in moving balls  101  to the bottom of the buffer chute  320 . By pressurizing conduit C 5 ,  335 , there is a downward force (in addition to gravity) on the balls at the bottom of the buffer chute  320 . Ball A is held in position by vacuum on conduit C 4 ,  334  and by a first stop  341 .  
         [0066]    In FIG. 16, conduit C 3 ,  333  has become vacuum and conduit C 4 ,  334  has become pressurized. The air emanating conduit C 4 ,  334 , in cooperation with the vacuum condition of conduit C 3 ,  333 , causes ball A to move from the first stop  341  to the second stop  342 , and, as a result, ball A has changed course by about 90°. Ball A is held in position by vacuum on conduit C 3 ,  333  and by the second stop  342 .  
         [0067]    In FIG. 17, conduit C 4 ,  334  is returned to the vacuum condition, the stack  340  of balls B-I moves down one position, as indicated by arrow  374 , as a result of the vacuum on conduit C 4 , with help from gravity and from the pressure from conduit C 5 ,  335 . Ball B is held in position by the vacuum on conduit C 4 ,  334  and by the first stop  341 .  
         [0068]    In FIG. 18, conduit C 3 ,  333  becoming pressurized, in cooperation with the vacuum at conduit C 2 ,  332  causes ball A to move from the second stop  342  to a third stop  343 , as indicated by arrow  375 . As a result of moving from the second stop  342  to the third stop  343 , ball A has changed course by about 135°. Ball A is held in position by the vacuum on C 3  and by the third stop  343 .  
         [0069]    In FIG. 19, conduit C 3 ,  333  is returned to the vacuum condition, and conduit C 4 ,  334  is pressurized, which combine to move ball B from the first stop  341  to the second stop  342 , as indicated by arrow  376 . Ball B is held in position by the vacuum at conduit C 3 ,  333  and by the second stop  342 .  
         [0070]    In FIG. 20, conduit C 4 ,  334  is returned to the vacuum condition, which, in conjunction with gravity, causes balls C-I to move down one position, as indicated by arrow  377 . Ball C is held in position by the vacuum on conduit C 4 ,  334  and by the first stop  341 .  
         [0071]    In FIG. 21, conduit C 2 ,  332  is pressurized and conduit C 1 ,  331  is changed to vacuum condition, which, together, cause ball A to move from the third stop  343  to a fourth stop  344 , as indicated by arrow  378 . As a result of moving from the third stop  343  to the fourth stop  344 , ball A has changed course by about 135°. Ball A is held in position by the vacuum condition on conduit C 1 ,  331  and by the fourth stop  344 .  
         [0072]    In FIG. 22, conduit C 2 ,  332  is returned to the vacuum condition. Conduit C 3 ,  333  is pressurized. Ball B moves from the second stop  342  to the third stop  343 , as indicated by arrow  379 . Ball B is held in position by the vacuum condition on conduit C 2 ,  332  and by the third stop  343 .  
         [0073]    In FIG. 23, conduit C 3 ,  333  is returned to the vacuum condition. Conduit C 4 ,  334  is pressurized. Ball C moves from the first stop  341  to the second stop  342 , as indicated by arrow  380 . Ball C is held in position by the vacuum condition on conduit C 3 ,  333  and by the second stop  342 .  
         [0074]    In FIG. 24, conduit C 4 ,  334  is returned to the vacuum condition, which, in conjunction with gravity, causes the stack  340  of balls D-I to move down one position, as indicated by arrow  381 . Ball D is held in position by the vacuum on conduit C 4 ,  334  and by the first stop  341 .  
         [0075]    In FIG. 25, conduit C 1 ,  331  is pressurized to move ball A from the fourth stop  344 , thereby causing the ball  101  to be ejected (as indicated by arrow  382 ) from the dispenser  100  to the target device such as the BGA  120  shown in FIG. 1. As a result of moving from the fourth stop  344  to being ejected, ball A has changed course by about 135°. The fourth stop  344  is alternatively a moving dispenser tube, which moves vertically in a sewing machine fashion, and which ejects a ball  101  from the fourth stop when the fourth stop in a lowest position, thereby being closest to the target device.  
         [0076]    Although FIGS.  15 - 25  describe steps of the initial loading of the pneumatic singulator  370  until the first ejection of a ball  101 , it is important to realize that during continuous operation the pneumatic singulator is both being loaded and ejecting balls at the same time.  
         [0077]    Table 1 shows the state of each conduit C 1 -C 8 ,  331 - 338 , during each step of continuous operation of the dispenser  100 .  
                                                                                                           TABLE 1                                       CONDUIT            STEP       1   2   3   4   5   6   7   8                    1       V   V   V   V   P   V   V   V       2       V   P   V   V   P   V   V   V       3       V   V   P   V   P   V   V   V       4       V   V   V   P   P   V   V   V       5       V   V   V   V   P   V   V   V       6       P   V   V   V   P   V   V   V       7       V   P   V   V   P   V   V   V       8       V   V   P   V   P   V   V   V       9       V   V   V   P   P   V   V   V       10       V   V   V   V   P   V   V   V       11       P   V   V   V   P   V   V   V       12       V   P   V   V   P   V   V   V       13       V   V   P   V   P   V   V   V       14       V   V   V   P   P   V   V   V       15       V   V   V   V   P   V   V   V       16       P   V   V   V   P   V   V   V                  
 
         [0078]    The dispenser  100  starts in step  1 , which has “VVVVPVVV” as the state of the eight conduits C 1 -C 8 ,  331 - 338 . The letter “V” indicates vacuum and the letter “P” indicates air pressure in the conduit. After step  1 , the dispenser  100  performs steps  2 - 16 . In Table 1, steps  2 - 6  are shown in one group, steps  7 - 11  are shown a second group and steps  12 - 16  are shown in a third group, because each group of five steps have the same five sets of states for the eight conduits C 1 -C 8 ,  331 - 338 . After the initial occurrence of step  1 , the dispenser  100  performs steps  2 - 6 , then repeats (at steps  7 - 10 ) the same five sets of states as was performed for steps  2 - 6 , and then repeats again (at steps  11 - 16 ) the same five sets of states as had been performed for steps  2 - 6 . In particular, the dispenser  100  indefinitely repeats the same five sets of states after step  16 , also. The dispenser  100  does not re-enter the set of states of step  1 , unless the operation is paused. Except for step  1 , which has an indefinite dwell time, each step has a dwell time of about 20 msec. The dispenser  100  in accordance with the invention ejects balls  101  at a rate of about ten balls per second.  
         [0079]    It should be noted that FIGS.  15 - 25  are intended to show initial loading, rather than continuous operation. The dispenser  100  is programmed to perform all the steps of Table 1 during both initial loading and continuous operation; however, five of the steps do not produce any ball movement during initial loading. There is no Drawing Figure associated with the five steps that produce no ball movement during initial loading. During initial loading, steps  2 ,  3 ,  6 ,  7  and  11  do not produce any ball movement because balls have not yet reached the second stop  342 , the third stop  343  and the fourth stop  344  of the pneumatic singulator  370 , at which steps  2 ,  3 ,  6 ,  7  and  11  would cause ball movement. Alternatively, the dispenser  100  is programmed to perform all the steps of Table 1 during continuous operation only, and is programmed to perform only the steps associated with FIGS.  15 - 25  during initial loading. During continuous operation, each step of Table 1 produces ball movement.  
         [0080]    [0080]FIG. 26 is an enlarged view of the ejection area  271  showing a path through the pneumatic singulator  370 . After pausing at each stop  341 - 344 , each of the balls  101  traveling through the pneumatic singulator  370  changes course, or trajectory, by at least 45°. It should be appreciated that the movement of the balls  101  through an operating channel of the dispenser  100 , which extends from opening  206  to the fourth stop  344 , is accomplished solely by selective application of air pressure and vacuum at various points of the operating channel, and not by any solid object contacting a ball. The shape of the path that the balls  101  take through the dispenser  100  and the existence of the stops  341 - 344 , advantageously allow less precise application of vacuum and pressure. In particular, the stops  341 - 344  permit less uncertainty as to the position of the balls  101  at any instance. The pneumatic singulator  370  comprises two vents  371 ,  372  for allowing the escape of air. The diameter of the vents  371 ,  372  are less than half the diameter of a ball  101 .  
         [0081]    [0081]FIG. 27 is an exploded view of the head unit  108  showing the assembly of the head unit. Within the interface housing  144  is an interface board assembly  170 , eight solenoids  171 - 178 , a solenoid cable assembly  179  connected to the eight solenoids, and a manifold  180  connected to the eight solenoids  171 - 178  and to the eight conduits C 1 -C 8 ,  331 - 338 . A sensor board assembly  189  is attached to the interface board assembly  170 . Within the manifold assembly  180  are eight valves operated by the eight solenoids  171 - 178  for switching one of air pressure and vacuum to the eight conduits C 1 -C 8 ,  331 - 338 . Preferably, the vacuum is about −5.9″ Hg, or −2.9 psi, and the air pressure is about twenty (20) psi.  
         [0082]    [0082]FIG. 28 is a perspective view of a manifold assembly  180  of the dispenser  100 . The manifold assembly  180  has port  190  for connection to a constant source of vacuum (not shown) and port  191  for connection to a continuous source of air pressure (not shown).  
         [0083]    [0083]FIG. 29 is a functional electrical block diagram  390  for controlling the manifold assembly  180 . Within the head unit  108  are a controller board  391  electrically coupled to a solenoid driver board  392 . The controller board  391  is coupled to the host computer  393  via a USB link  394 . The host computer  393  is programmed to operate the dispenser  100 , including performing the steps set forth in Table 1.  
         [0084]    While the present invention has been described with respect to preferred embodiments thereof, such description is for illustrative purposes only, and is not to be construed as limiting the scope of the invention. Various modifications and changes may be made to the described embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims. For example, although the dispenser  100  in uses an x-y table to move the target device while the head unit  108  remains stationary, it is envisaged that the target device remains stationary and the head unit moves in the x and y directions. Although for simplicity, conduits C 1 -C 8 ,  331 - 338  have either air pressure or vacuum in them; alternatively, one or more conduits C 1 -C 8  are switched, at selected times, to a neutral state in order to enhance operation. Although, preferably, there are four stops  341 - 344 , it is foreseeable that the dispenser  100  would function with a greater or smaller number of stops. It is also foreseeable that means for sensing the position of the balls  101  within the dispenser  100  can increase the ejection rate and otherwise enhance operation. Although the dispenser  100  is easily cleaned, the dispenser can be made self-cleaning by addition of actuators, to secure and to occasionally separate the plates  131 - 136  and  141 - 147 , instead of bolts through the holes  137 - 138 . It is also foreseeable to laminate more than one dispenser  100  together in order to perform multiple dispensings of balls  101  simultaneously.  
       LIST OF REFERENCE NUMERALS  
       [0085]    [0085] 100  Solder Ball Dispenser (Dispenser)  
         [0086]    [0086] 101  Solder Balls (Balls)  
         [0087]    [0087] 103  Frame  
         [0088]    [0088] 104  Feeder Unit  
         [0089]    [0089] 105  Base  
         [0090]    [0090] 108  Head Unit  
         [0091]    [0091] 110  X-Y Table  
         [0092]    [0092] 112  Platform  
         [0093]    [0093] 120  Ball Grid Array (BGA)  
         [0094]    [0094] 122  Connecting Portion  
         [0095]    [0095] 131 - 136  Flat Plates of Feeder Unit  
         [0096]    [0096] 137 - 138  Holes  
         [0097]    [0097] 141  Front Plate  
         [0098]    [0098] 142  Head Plate  
         [0099]    [0099] 143  Back Plate  
         [0100]    [0100] 144  Interface Housing  
         [0101]    [0101] 145  USB Housing  
         [0102]    [0102] 146  USB Controller Board Assembly  
         [0103]    [0103] 147  Head Mount  
         [0104]    [0104] 150  Test Button  
         [0105]    [0105] 151 - 152  Controller Status LEDs  
         [0106]    [0106] 153  Reset Button  
         [0107]    [0107] 154  USB Controller  
         [0108]    [0108] 155  Solenoid Power Connector  
         [0109]    [0109] 161 - 168  Solenoids LEDs  
         [0110]    [0110] 170  Interface Board Assembly  
         [0111]    [0111] 171 - 178  Solenoids  
         [0112]    [0112] 179  Solenoid Cable Assembly  
         [0113]    [0113] 180  Manifold  
         [0114]    [0114] 181 - 188  Valves  
         [0115]    [0115] 189  Sensor Board Assembly  
         [0116]    [0116] 190 - 191  Ports  
         [0117]    [0117] 200  Feeder Unit Chamber  
         [0118]    [0118] 204  Maximum Diameter of Feeder Unit Chamber  
         [0119]    [0119] 205  Front Side of Feeder Unit  
         [0120]    [0120] 206  Opening  
         [0121]    [0121] 207  Tubular Pathway  
         [0122]    [0122] 208  Opening  
         [0123]    [0123] 209  Inclined Pathway  
         [0124]    [0124] 210  Exit Slot  
         [0125]    [0125] 211  Point A  
         [0126]    [0126] 213  Point B  
         [0127]    [0127] 220  Bottom of Feeder Unit Chamber  
         [0128]    [0128] 221  Point C  
         [0129]    [0129] 222  Point D  
         [0130]    [0130] 225  First Void  
         [0131]    [0131] 226  Air Jet  
         [0132]    [0132] 230  Port  
         [0133]    [0133] 232  Conduit  
         [0134]    [0134] 234  Outside Port  
         [0135]    [0135] 235  Back Wall  
         [0136]    [0136] 240  Second Void  
         [0137]    [0137] 241  Opening  
         [0138]    [0138] 242  Mesh  
         [0139]    [0139] 251  Depth  
         [0140]    [0140] 270  Arrow  
         [0141]    [0141] 271  Ejection Area  
         [0142]    [0142] 300  Head Unit Chamber  
         [0143]    [0143] 304  Entrance  
         [0144]    [0144] 306  Declined Ramp  
         [0145]    [0145] 308  Outer Diameter  
         [0146]    [0146] 310  Depth of Head Unit  
         [0147]    [0147] 312  Exit  
         [0148]    [0148] 313  Entrance of Buffer Chute  
         [0149]    [0149] 320  Buffer Chute  
         [0150]    [0150] 321  Width of Buffer Chute  
         [0151]    [0151] 331 - 338  Conduits C 1 -C 8   
         [0152]    [0152] 340  Stack  
         [0153]    [0153] 341 - 344  Mechanical Stops (Stops)  
         [0154]    [0154] 350  Arrow  
         [0155]    [0155] 351 - 354  Orifice  
         [0156]    [0156] 355  Arrow  
         [0157]    [0157] 360  Location  
         [0158]    [0158] 365  Air Jet  
         [0159]    [0159] 370  Pneumatic Singulator  
         [0160]    [0160] 371 - 372  Vents  
         [0161]    [0161] 372 - 383  Arrows  
         [0162]    [0162] 390  Functional Electrical Block Diagram  
         [0163]    [0163] 391  Controller Board  
         [0164]    [0164] 392  Solenoid Driver Board  
         [0165]    [0165] 393  Host Computer  
         [0166]    [0166] 394  USB Link