Abstract:
A solder ball attachment system for manufacturing an integrated circuit or the like is disclosed. The solder ball attachment system includes a flux station adapted to apply flux onto a substrate and a solder ball placement station adapted to place solder balls onto the flux. A conveyor assembly is included to move the substrate between the flux station and the solder ball placement station.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to packaging and manufacturing of integrated circuits and the like, and more particularly to a solder ball attachment system.  
         BACKGROUND INFORMATION  
         [0002]    Integrated circuits in an electronic device are typically electrically connected to multiple other integrated circuits or components of the electronic device. For example, a processor chip in a computer will be connected to one or more sources of power, to memory devices or modules, input/output interfaces and the like. This can require that hundreds of electrical connections be made to the processor chip or integrated circuit (IC) chip. The IC chip will typically be mounted to a printed circuit board (PCB) and the multiple different electrical connections will need to be made between the IC chip and the PCB. One technology for making these multiple electrical connections is ball grid array (BGA) technology. In BGA technology, sometimes hundreds of extremely small solder balls, on the order of a micron in diameter, must be precisely placed according to a predetermined pattern to make electrical contact between conductive pins or pads on the IC chip and conductive pads on the substrate of the PCB. A misplacement of few microns or less can result in a defective product.  
           [0003]    The predetermined pattern in which the solder balls are placed will vary from one particular IC chip design to another. When a new IC chip is under development, the process for attaching or placing the solder balls must be confirmed or certified as being accurate and reliable before being implemented in a high volume manufacturing operation. A manual ball attachment jig is typically used in the development stage but this arrangement and process is time consuming and costly to load and place the balls and can delay the certification or acceptance of a new product and the process for manufacturing the product.  
           [0004]    Accordingly, for the reason stated above, and for other reasons that will become apparent upon reading and understanding the present specification, there is a need for a semiautomatic solder ball attachment system that is efficient to shorten the lead time of development activities and reduce costs. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is a perspective view of a solder ball attachment system in accordance with the present invention.  
         [0006]    [0006]FIG. 2 is a detailed perspective view of a flux station for the ball attachment system of FIG. 1.  
         [0007]    [0007]FIG. 3 is a detailed perspective view of a tray portion of a ball placement station for the ball attachment system of FIG. 1.  
         [0008]    [0008]FIG. 4 is a detailed side elevation view of a pivotable carriage assembly of a ball placement station in accordance with the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0009]    In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.  
         [0010]    [0010]FIG. 1 shows a perspective view of a solder ball attachment system  100  in accordance with the present invention. The solder ball attachment system  100  includes a flux station  102  to apply flux to a substrate  104  and a solder ball placement station  106  to place solder balls onto the substrate  104 . The flux station  102  and the solder ball placement station  106  are mounted on a platform  108  adjacent one another. A conveyor assembly  110  is also mounted on the platform  108  and moves the substrate  104  between the flux station  102  and the solder ball placement station  106 . The conveyor assembly  110  includes a belt or pair of conveyor belts  112 . The belts  112  is driven by a motor  114  and a hand crank  116  may be provided to operate the conveyor belts  112  manually. A substrate holder or support  118  rests on or is attachable to the conveyor belts  112  to hold the substrate  104  during processing.  
         [0011]    The solder ball attachment system  100  further includes an alignment arrangement  119  for proper alignment of the substrate  104  during processing in the flux station  102  and the solder ball placement station  106 . As part of the alignment arrangement  119 , the substrate support  118  may include a plurality guide pins  120  mounted thereon for proper alignment of the substrate  104  during processing in the flux station  102  and solder ball placement station  106 .  
         [0012]    To begin a solder ball placement process, the substrate  104  is placed onto the substrate support  118  on the conveyor belt or belts  112  and the substrate  104  is moved into proper position at the flux station  102 . Referring also to FIG. 2 which is a detailed perspective view of the flux station  102 , the flux station  102  includes a flux screen  122 . The flux screen  122  is lowered over the substrate  104 . The flux screen  122  has at least two guide holes  124  formed therein through which the guide pins  120  of the substrate support  118  are inserted for alignment of the flux screen  122  with the substrate  104 . The flux screen  122  has a plurality of openings  126  formed therein in a predetermined pattern through which flux is applied or printed onto the substrate  104  according to the predetermined pattern. The predetermined pattern of the openings  126  may vary according to the design of the particular IC chip and the required placement of the solder balls on the substrate  104  to make electrical connections between the particular IC chip and conductive pads  128  (FIG. 1) formed on the substrate  104 .  
         [0013]    The alignment arrangement  119  may also include a plurality of adjustment screws  130  selectively positioned around a perimeter or sides  132  of the flux station  102  to precisely adjust the placement of the openings  126  in the flux screen  122  relative to the conductive pads  128  formed on the substrate  104  for proper alignment between the opens  126  and the conductive pads  128 . After alignment, the flux screen  122  may then be clamped in place by clamp screws  134  to prevent the flux screen  122  from moving relative to the substrate  104  during application of the flux.  
         [0014]    The flux station  102  also includes a flux applicator assembly  136 . The flux applicator assembly  136  includes a first upright support member  138  attached to one side  140  of the flux station  102  and a second upright member  142  attached to another side  144  of the flux station  102  opposite to the one side  140 . A horizontal support member  146  is suspended between the first and second upright support members  138  and  140  at a predetermined distance above the flux screen  122 . The horizontal support member  146  is preferably hinged to the first upright member  138  by a hinge arrangement  148  and the horizontal support member  146  may be attached to the second upright support member  142  by a removable pin  150  or the like. This horizontal support member  146  can then be swung open to remove or replace the flux screen  122 . The horizontal support member  146  has a longitudinal slot  152  formed therein through which a handle  154  is attached to a squeeze blade  156 . The squeeze blade  156  may be made from a resilient material such a flexible plastic or rubber type material with one end  158  in sliding contact with the upper or exposed surface of the flux screen  122 . The handle  154  is slidable within the slot  152  to move the squeeze blade  156  back and forth across the flux screen  122  to push or force flux uniformly through the openings  126  and onto the substrate  104 . The flux will then be applied or printed evenly or uniformly on the substrate  104  in the predetermined pattern.  
         [0015]    After flux is applied to the substrate  104 , the flux screen  122  is removed from the substrate  104  and the conveyor belts  112  may be activated to move the substrate  104  to the solder ball placement station  106 . A conveyor belt operation switch  160  (FIG. 1) is mounted to the platform  108  and is electrically connected to the motor  114  to control the operation of the motor  114  to move the conveyor belts  112  in a forward direction or a reverse direction. In one position the conveyor switch  160  causes the motor  112  to move the substrate holder  118  from the flux station  102  to the ball placement station  106  and in another switch position, the conveyor operation switch  160  causes the substrate holder  118  to move in an opposite direction.  
         [0016]    Referring also to FIG. 3 which is a detailed perspective view of a tray portion  162  of the solder ball placement station  106 , the tray portion  162  includes a first section or ball placement section  164  and a second section or ball bin  166 . A ball placement mask  168  is mounted in the first section  164  and the second section or ball bin  166  is where the solder balls  169  are stored. The ball placement mask  168  is mounted to an underside of the first section  164  by an attachment mechanism  170 . The attachment mechanism  170  may be a latch-arrangement or magnetic holders. The ball placement mask  168  is properly aligned to the first section  164  by guide holes  171  formed in the ball placement mask  168  which are received on guide pins  172  formed on the underside of the first section  164 .  
         [0017]    Each section  164  and  166  has a respective ramp  173  and  174  that slopes away from a center segment  175  of the tray portion  162 . Accordingly, the solder balls  169  will be retained in the ball bin  166  when the tray portion  162  is level in a non-ball placement or non-operational position.  
         [0018]    Referring also to FIG. 4 which is a detailed view of a portion of a pivotable carriage assembly  176  of the solder ball placement station  106 . The pivotable carriage assembly  176  includes a lower portion or substrate support holder  177  and an upper portion or tray portion support  178 . As the conveyor belts  112  move the substrate support  118  into the solder ball placement station  106 , side edges  179  of the substrate support  118  will be received into recesses  180  formed in the substrate support holder  177  of the pivotable carriage assembly  176 . When the substrate support  118  is in proper position at the solder ball placement station  106 , an “UP” illuminated pushbutton  181  (FIG. 1) will turn on. The “UP” pushbutton  181  may then be pushed to operate a pair of actuators  182  to raise the substrate support holder  177  and substrate  104  to position the substrate  104  under the ball placement mask  168 . The actuators  182  are each respectively mounted proximate to opposite ends of the tray portion holder  178  of the pivotable carriage assembly  176 , as best shown in FIG. 1. Each of the actuators  182  may be an air cylinder or similar device to raise the substrate support holder  177  into position and to lower the substrate support holder  177  and substrate  104  after a ball placement operation.  
         [0019]    The tray portion  162  is mounted to the tray portion holder  178 . The tray portion holder  178  has a plurality of guide posts  183  formed on an underside  184  thereof. As the substrate support holder  177  is raised, the guide posts  183  will be received into respective guide holes  185  formed in the substrate support holder  177  to properly align the substrate support  118  and substrate  104  with the ball placement mask  168 . Additionally, a pair of stability shafts  186  are mounted to the substrate support holder  177  at each end thereof proximate to each actuator  182 , as best shown in FIG. 1. The stability shafts  186  each extend through openings  187  formed in the tray portion holder  178  and guide movement of the substrate support holder  177  into proper position with the tray portion holder  178  and the substrate  104  into proper alignment with the ball placement mask  168  for a ball placement operation.  
         [0020]    Referring also back to FIG. 1, the tray portion  162  of the solder ball placement station  106  is mounted in the tray portion holder  178  of the pivotable carriage assembly  176 . The pivotable carriage assembly  176  is pivotably mounted at two opposite ends thereof to a pair of respective stanchion members  189 . The stanchion members  189  are mounted on the platform  108  and support the pivotable carriage assembly  176  over the conveyor assembly  110  at the solder ball placement station  106 . The pivotable carriage assembly  176  is retained in a level position while the substrate support  118  is raised to a location under the tray portion  162 . After alignment of the substrate support  118  with the tray portion  162 , the pivotable carriage assembly  176  is released and may be pivoted to a position to cause the solder balls  169  (FIG. 3) to roll from the ball bin section  166  into the first section  164  of the tray portion  162  containing the ball placement mask  168  (FIG. 3). The ball placement mask  168  has a plurality of holes  190  formed therein in a selected pattern to place the solder balls  169  on the substrate  104  according to the selected pattern. The selected pattern of holes  190  may be substantially the same as or coordinate with the predetermined pattern of openings  126  (FIG. 2) formed in the flux screen  122  for applying the flux. When the solder balls  169  roll over the ball placement mask  168 , the solder balls  169  will drop by gravity into any unfilled holes  190  in the mask  168  and are placed or attached to the substrate  104  according to the selected pattern of holes  190 . The pivotable carriage assembly  176  may be tilted back and forth until all of the holes  190  have been filled with a solder ball  169 . The carriage assembly  176  is then tilted or pivoted to a position to cause all remaining or unused solder balls  169  to roll back into the ball bin  166  where the balls  169  are retained until the next substrate  104  is received for processing. The carriage assembly  176  may be tilted or pivoted by a wheel  191  attached to an axle (not shown) of the carriage assembly  176  through a hub of the stanchion  189 .  
         [0021]    After placement of the solder balls  169  on the substrate  104 , the carriage assembly  176  is returned and retained in a level or horizontal position. A “DOWN” illuminated pushbutton  192  is turned on. The “DOWN” pushbutton  192  is pushed to operate the actuators  182  to lower the substrate support  118  back onto the conveyor belts  112 . The conveyor belt operation switch  160  may then be operated in the reverse direction to move the substrate support  118  from the solder ball placement station  106 . The completed substrate  104  may be removed from the substrate support  118  and another unfinished substrate may be placed on the support  118  for solder ball placement.  
         [0022]    The solder ball attachment system  100  also preferably includes a power ON/OFF switch  194  mounted on the platform  108  to control the overall application of power to the solder ball attachment system  100 . The solder ball attachment system  100  may also include actuator covers  196  to cover the actuators  182  and protect them from damage.  
         [0023]    Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.