Abstract:
An air-suspended die sorter is disclosed, in particular an air-suspended die sorter capable of performing die sorting, die attaching and die pick-up in the semiconductor industry. The present invention provides an air-suspended die sorter capable of eliminating spring preload, and lowering mechanical friction so as to lift die sorting precision and elevate the success rate, and has a cylinder unit, a piston unit and a pressure unit. The piston type design and a precise control of pressure on top and on bottom of the piston, respectively, enables the present invention to offer an air-suspended state that has done away with stress problems associated with the use of springs. The present invention further provides a novel buffer design for reducing friction and die impact often encountered in prior art applications.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an air-suspended die sorter and in particular relates to an air-suspended die sorter capable of performing die sorting, die attach and die pick-up in the semiconductor industry.  
         BACKGROUND OF THE INVENTION  
         [0002]    After semiconductor wafers are divided into dies, die sorters are used in manufacturing operations to pick up and place dies on die trays. The same procedure that repeats a number of times in subsequent die testing, die attach and packaging is accomplished by using die sorters.  
           [0003]    Today&#39;s die sorters normally attach a sorter tip to a robot arm. Having an air passage going cross its center and being connected to a vacuum pump that provides a vacuum condition, sorter tip picks up a die via suction when it approaches and reaches the die. When the robot arm carries the sorter tip to a designated location and as a proper amount of air is allowed into air passage, the die lands on the designated location since the vacuum condition no longer exists.  
           [0004]    Since the sorter tip as described above utilizes spring type parts for providing buffer mechanism that absorbs impact energy, prior art sorter tip possesses the following deficiencies:  
           [0005]    (1) Spring preload: Before being used as a buffer mechanism, a spring has to be preloaded with an initial compression setting, which inevitably reduces spring&#39;s impact absorbing capacity. This reduction of capacity causes damages to the die if and when the sorter tip fails to provide adequate impact absorbance.  
           [0006]    (2) Mechanical friction: A spring has to overcome mechanical friction when being used to provide buffer mechanism. This further reduces spring&#39;s impact absorbing capacity.  
           [0007]    (3) Difficulties in picking up the die: When the spring type sorter tip fails to provide adequate impact absorbance, small dies (less than 0.5 cm 2 , for example) often get flipped over or get damaged by spring type sorter.  
           [0008]    (4) Imprecise control: Prior art spring type sorter tip is incapable of controlling the amount of air that is allowed in to break the vacuum condition. This lack of precision control often causes the die to land too fast such that the die flips over, stands up on its side or lands outside die tray. Sometimes, the die fails to land at all.  
         SUMMARY OF THE INVENTION  
         [0009]    Aimed at resolving the above disadvantages, the main object of the present invention is to provide an air-suspended die sorter capable of eliminating spring preload, lowering mechanical friction so as to lift die sorting precision and elevate success rate.  
           [0010]    Another object of the present invention is to provide an air-suspended die sorter capable of controlling and providing the precise amount of air by solenoid valves and pneumatic regulators to terminate the vacuum state, thus raising the success rate for landing the die.  
           [0011]    In order to attain the above goals, an air-suspended die sorter  10  in accordance with the first preferred embodiment of the present invention comprises a cylinder unit, a piston unit and a pressure unit. The cylinder unit includes at least a trunk and a lower cap. The trunk has a through hole going through it and said through hole has a first end and a second end. Located on the side of the second end of the trunk, the lower cap and the trunk form a hollow space therein between. A first fitting and a second fitting are provided on the trunk such that the first fitting is connected with the first end of the through hole and the second fitting is connected with the hollow space. The piston unit includes at least one shank holder shaft. The shank holder shaft comprises a piston portion, an air-suspended portion, an extension portion and an air passage going through the piston portion, the air-suspended portion and the extension portion. The piston portion is capable of fitting in the through hole and moving along the axis. A first air chamber is formed between the air-suspended portion, which is provided in the hollow space, and the trunk. The extension portion extends outside the lower cap through a gap provided between the lower cap and the extension portion. The pressure unit includes at least a vacuum device, a pressure source and a first pneumatic regulator. Being connected with the first fitting, the vacuum device is capable of providing a low-pressure state at the first end of the through hole and the air passage for enabling the pick-up operation. Being connected between the second fitting and the pressure source, the first pneumatic regulator is capable of controlling the pressure in the sealed first chamber and balancing the pressure on the top and on the bottom of the air-suspended portion, thereby providing the air-suspended state for the shank holder shaft.  
           [0012]    The pressure unit further includes a first solenoid valve, a second solenoid valve and a second pneumatic regulator. The first solenoid valve is connected between the vacuum device and the first fitting. One end of the second solenoid valve is connected with the first solenoid. The second pneumatic regulator is connected between the second solenoid valve and the pressure source. By properly controlling the first solenoid valve and the second solenoid valve to switch between having air flow and otherwise, the pressure source provides a certain amount of air between the first solenoid valve and the second solenoid valve. The first solenoid valve allows the first fitting to be in air contact with the vacuum device and the second solenoid valve, alternatively. When the first fitting is in air contact with the vacuum device, the air passage that goes through the pick-up tip, the pick-up head and the piston, respectively, is in a low-pressure state (or vacuum state) for allowing a die to be picked up. When the first fitting is having air contact with the second solenoid valve, said certain amount of air between the first solenoid valve and the second solenoid valve is permitted to enter the air passage and terminate the vacuum condition, thereby allowing a die to be released.  
           [0013]    Thank to a piston type design and a precise control of pressure on the top and on the bottom of the piston, respectively, the present invention offers an air-suspended state that has done away with stress problems associated with using springs. The present invention further provides a novel buffer design for reducing friction and die impact often encountered in prior art applications. Precise amount of air is sealed between the solenoid valves by serially connecting the piston type die sorter with two solenoid valves and a pneumatic regulator. Moreover, termination of vacuum state is accomplished by allowing the precise amount of air sealed between the two solenoid valves to enter the air-suspended die sorter.  
           [0014]    The following Description and Designation of Drawings are provided in order to help understand the features and content of the present invention. 
       
    
    
       [0015]    The accompanying drawings form a material part of this description, in which:  
         [0016]    [0016]FIG. 1 is a three-dimensional view of an air-suspended die sorter in accordance with the first preferred embodiment of the present invention.  
         [0017]    [0017]FIG. 2 is an explosive view of an air-suspended die sorter in accordance with the first preferred embodiment of the present invention.  
         [0018]    [0018]FIG. 3 is a cross-sectional view of an air-suspended die sorter in accordance with the first preferred embodiment of the present invention.  
         [0019]    [0019]FIG. 4 is a three-dimensional view of an air-suspended die sorter in accordance with the second preferred embodiment of the present invention.  
         [0020]    [0020]FIG. 5 is an explosive view of an air-suspended die sorter in accordance with the second preferred embodiment of the present invention.  
         [0021]    [0021]FIG. 6 is a three-dimensional view of an air-suspended die sorter in accordance with the second preferred embodiment of the present invention being connected with a pressure unit.  
         [0022]    [0022]FIG. 7 is a three-dimensional perspective of a route between two operating positions of an air-suspended die sorter in accordance with the second preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]    In the following description, the present invention is described in connection with a specific and preferred embodiment. It will be understood that the present invention is not limited to these embodiments, but rather is to be construed as the spirit and scope defined by the appended claims.  
         [0024]    In the present specification, the structure and process are described as comprising specific components and steps, respectively. It is within the contemplation of the present inventors that the structure and process can consist essentially of, or consist of, the disclosed components and steps, respectively.  
         [0025]    One of the main features of the present invention is having a piston type sorter tip and applying on it a precisely controlled air pressure for creating an air suspension condition. Taking advantages of precise air pressure, the present invention minimizes spring preload problems. Specifically, by reducing mechanical friction and increasing buffer capability, the application of air suspension has dispensed with problems encountered by spring type sorter tip, particularly when being used for picking up or releasing small dies. By opening one of the two solenoid valves, a precise amount of air being sealed in pipelines between two solenoid valves is allowed to enter the sorter tip to reverse the vacuum condition, precisely. A preferred embodiment is illustrated as follows.  
         [0026]    Please refer to FIG. 2 and FIG. 3, which are an explosive view and a cross-sectional view of an air-suspended die sorter  10  in accordance with the first preferred embodiment of the present invention, respectively. The air-suspended die sorter  10  according to this preferred embodiment comprises a cylinder unit  11 , a piston unit  13  and a pressure unit  15 .  
         [0027]    As shown in FIG. 2 and FIG. 3, the cylinder unit  11  has at least a trunk  111 , an upper cap  113 , a hollow ring  115  and a lower cap  117 . A through hole  1111  is provided on the trunk  111  and a first end  1112  and a second end  1113  are provided at both ends of the through hole  1111 , respectively. The lower cap  117  is provided on the side of the second end  1113  and the hollow ring  115  is disposed in a space (no numeral) between the lower cap  117  and the trunk  111 . On the trunk  111 , a first fitting  1114  and a second fitting  1115  are provided to connect with the first end  1112  of the through hole  1111  and the side of said space adjacent to the trunk  111 , respectively. The upper cap  113  is provided on the side of the first end  1112  of the through hole  1111 . The trunk  111  is capable of being moved by a robot  40  being attached to it.  
         [0028]    A piston unit  13  comprises a shank holder shaft  131 , a connecting rod  133 , and a pick-up tip  135 . The shank holder shaft  131  has a piston portion  1311 , an air-suspended portion  1313 , an extension portion  1315 , and a first air passage  1317  going through it. Being able to fit in the through hole  1111 , the piston portion  1311  of the shank holder shaft  131  is capable of moving along the axis of the through hole  1111 . Being larger than the through hole  1111 , the air-suspended portion  1313  is contained in a hollow space. Having an inner diameter equal to the outer diameter of the air-suspended portion  1313 , the hollow ring  115  is provided for forming a sealed first air chamber  1116  between the air-suspended portion  1313  and the trunk  111 . The extension portion  1315  extends outside of the lower cap  117 . A gap  1319  is provided between the lower cap  117  and the extension portion  1315 . One end of the connecting rod  133  is connected with the extension portion  1315 . Extending outside the lower cap  117 , the other end of the connecting rod  133  is connected with the pick-up tip  135 . Preferably, the pick-up tip  135  is made of such softer material as rubber to prevent contact damage to the die (not shown). The connecting rod  133  also provides a second air passage  1318  for connecting with the through hole  1111 . In corresponding locations of the trunk  111 , the air-suspended portion  1313  and the lower cap  117 , a pinhole is provided. By plugging a pin into the pinhole, the air-suspended portion  1313  is restricted to linear rather than rotational movements.  
         [0029]    As shown in FIG. 3, the pressure unit  15  comprises at least a vacuum device  151 , a pressure source  152 , a first pneumatic regulator  153 , a second pneumatic regulator  154 , a first solenoid valve  155 , a second solenoid valve  156 , and a control unit  157 . The control unit  157  is connected with the aforementioned valves for control purpose. The vacuum device  151  is connected with the first fitting  1114  so as to generate a low-pressure state in the first end  1112  of the through hole  1111 , the first air passage  1317  and the second air passage  1318 , respectively. By maintaining a low-pressure state in the first air passage  1317  and the second air passage  1318 , respectively, the die sorter is capable of picking up dies. Connected between the second fitting  1115  and the pressure source  152 , the first pneumatic regulator  153  is capable of regulating the pressure sealed in the first air chamber  1116 , balancing the pressures on the top and on the bottom of the air-suspended portion  1313 , and rendering the shank holder shaft  131  in an air-suspended state.  
         [0030]    The first solenoid valve  155  is provided between the vacuum device  151  and the first fitting  1114 . One end of the second solenoid valve  156  is connected with the first solenoid valve  155 . By controlling the first solenoid valve  155  and the second solenoid valve  156  to switch between having air flow and otherwise, the second pneumatic regulator  154  between the second solenoid valve  156  and the pressure source  152 , is capable of storing a certain amount of air between the first solenoid valve  155  and the second solenoid valve  156 . By regulating the first solenoid valve  155 , the first fitting  1114  is able to switch between connection with the vacuum device  151  and connection with the second solenoid valve  156 . When the first fitting  1114  is having air contact with the vacuum device  151 , the low-pressure states in the first air passage  1317  and the second air passage  131  enable the operation of die pick-up. When the first fitting  1114  connects with the second solenoid valve  156 , the air stored between the first solenoid valve  155  and the second solenoid valve  156  is allowed to enter the first air passage  1317  and the second air passage  1318 , thus terminating the vacuum state and releasing the die.  
         [0031]    An optical sensor  51  and a plurality of sensing components  52  and  53  may be provided on the trunk  111  at proper locations. Disposed on the upper cap  113 , the optical sensor  51  possesses a sensing light path (not shown), which passes the through hole  1111 , the first air passages  1317  and the second air passage  1318 . The optical sensor  51  allows the detection of a die being picked up by the pick-up tip  135 , which is situated at the end of the second air passage  1318 . The sensing components  52  and  53  are capable of sensing the location of the air-suspended die sorter, respectively.  
         [0032]    Please refer to FIG. 4 and FIG. 5, which provide a three-dimensional and an explosive view, respectively, of an air-suspended die sorter  20  in accordance with the second preferred embodiment of the present invention. The air-suspended die sorter  20  comprises at least two parts, the first part being a cylinder unit  21  and the second part a piston unit  23 . The cylinder unit  21  has a cylinder base  211 , a connecting base  212  being connected with the cylinder base  211  for forming a sealed chamber (not shown), a pneumatic fitting  213  for providing a pressure greater than one atmospheric pressure as the operating pressure of the air-suspended die sorter  20  in accordance with the second preferred embodiment of the present invention, a rotation stop block  215  being provided above and at a distance away from the connecting base  212 , a second connect screw  216  being secured to the top of the rotation stop block  215  such that its screw head and screw protrude above and below the rotation stop block  215 , respectively, a first connect screw  217  being below the second connect screw  216 , sharing the same axis with the second connect screw  216  and being secured vertically to the connecting base  212  such that its screw head protrudes above the connecting base  212  and its screw is fully recessed in the connecting base  212 , a rotation stopper  214  being secured to the top of the connecting base  212  and being in friction contact with the rotation stop block  215  for preventing the air-suspended die sorter  20  from rotating, a supporter  218  having a smaller diameter and being below the cylinder base  211  for securing the cylinder base  211 , and a support base  219  for securing the supporter  218 .  
         [0033]    Being the second part of the air-suspended die sorter  20 , the piston unit  23  comprises a pick-up tip  231  for picking up a die, a pick-up head  232  being provided above the pick-up tip  231 , a piston  233  being provided above the pick-up head  232 , going vertically in ascending order through the cylinder base  211 , the sealed chamber between the cylinder base  211  and the connecting base  212 , the connecting base  212 , the space between the connecting base  212  and the rotation stop block  215 , before protruding above the rotation stop block  215 . Having a first rim  236  and a second rim  237  that surround it at proper locations, respectively, the piston  233  is a cylinder having the above-mentioned air passage. Via the first rim  236  and the second rim  237 , the piston  233  interacts with the sealed chamber and the lower rim of the rotation stop block  215 , respectively. The piston unit  23  further comprises a first fitting  235 , an air passage (not shown) going vertically through the pick-up tip  231 , the pick-up head  232  and the piston  233 . In operation, air is introduced via the pneumatic fitting  213  and air pressure is precisely regulated for driving the piston  233 , the pick-up head  232  and the pick-up tip  231  of the air-suspended die sorter for picking up a die.  
         [0034]    Please refer to FIG. 6, which shows a three-dimensional view of an air-suspended die sorter in accordance with the second preferred embodiment of the present invention being connected with a pressure unit  25 . The pressure unit  25  includes at least a vacuum device  251 , a pressure source  252 , a first pneumatic regulator  253 , a second pneumatic regulator  254 , a first solenoid valve  255 , a second solenoid valve  256  and a control unit  257 . The control unit  257  is connected with the aforementioned valves for control purpose. The vacuum device  251  via a first fitting  235  is capable of generating a low-pressure state in the air passage (not shown) that goes through the pick-up tip  231 , the pick-up head  232  and the piston  233 , respectively, and enabling the pick-up operation of the pick-up tip  231 . Connected between the pneumatic fitting  213  and the pressure source  252 , the first pneumatic regulator  253  is capable of regulating the pressure inside the sealed chamber (not shown) between the cylinder base  211  and the connecting base  212  and rendering the piston unit  23  of in an air-suspended state.  
         [0035]    The first solenoid valve  255  is connected between the vacuum device  251  and the first fitting  235 . One end of the second solenoid valve  256  is connected with the first solenoid valve  255 . The second pneumatic regulator  254  is connected between the second solenoid valve  256  and the pressure source  252 . By properly controlling the first solenoid valve  255  and the second solenoid valve  256  to switch between having air flow and otherwise, the pressure source  252  provides a certain amount of air between the first solenoid valve  255  and the second solenoid valve  256 . The first solenoid valve  255  allows the first fitting  235  to be in air contact with the vacuum device  251  and the second solenoid valve  256 , alternatively. When the first fitting  235  is having air contact with the vacuum device  251 , the air passage (not shown) that goes through the pick-up tip  231 , the pick-up head  232  and the piston  233 , respectively, is in a low-pressure state (or vacuum state) for allowing a die to be picked up. When the first fitting  235  is in air contact with the second solenoid valve  256 , said certain amount of air between the first solenoid valve  255  and the second solenoid valve  256  is permitted to enter the air passage (not shown) and terminate the vacuum condition, thereby allowing a die to be released.  
         [0036]    In operation, air is introduced from the pressure unit  25  and air pressure is precisely regulated for driving downward the piston  233 , the pick-up head  232  and the pick-up tip  231  so as to generate an air-suspended state for the air-suspended die sorter  20 . When the piston  233  moves downward, the rotation stop block  215  and the second connect screw  216  are caused to move downward until the second connect screw  216  makes contact with the first connect screw  217 . The sealed chamber maintains an internal pressure.  
         [0037]    Please refer to FIG. 7, which shows a three-dimensional perspective of a route  33  between two operating positions (position A  31  and position B  32 ) of an air-suspended die sorter  20  in accordance with the second preferred embodiment of the present invention. First, control software directs the air-suspended die sorter  20  to a pre-determined position A  31  for die pick-up. When nearing the area above position A  31 , the air-suspended die sorter  20  descends toward position A  31 . The moment the pick-up tip  231  touches the die at position A  31 , a reactive force causes the pick-up tip  231 , the pick-up head  232  and the piston  233  to move upward and the pick-up tip  231 , the pick-up head  232  and the piston  233  in turn drive the rotation stop block  215  and the second connect screw  216  to move upward and cause the second connect screw  216  and the first connect screw  217  to separate.  
         [0038]    Meanwhile, a sensing unit detects the separation of the second connect screw  216  and the first connect screw  217 , which signals the contact between the pick-up tip  231  and the die at position A  31 , and sends two instructions accordingly. The first instruction is to stop the air-suspended die sorter  20 &#39;s downward movement and the second instruction is to activate the pressure unit  25  and cause the air passage (not shown) that goes through the pick-up tip  231 , the pick-up head  232  and the piston  233 , respectively, to be in a low-pressure state (or vacuum state) for allowing the pick-up tip  231  to pick up a die.  
         [0039]    When the pick-up tip  231  holds to a die, air-suspended die sorter  20  moves upward and the reactive upward pressure is released, the piston  233  drives the second connect screw  216  downward and causes the second connect screw  216  to be in contact with the first connect screw  217 , again. Driven by control software, the air-suspended die sorter  20 , which holds to a die, moves upward from position A  31  to a pre-determined height and moves horizontally to a location above position B  32  before descending to position B  32 .  
         [0040]    When the pick-up tip  231  descends toward position B, the second connect screw  216  maintains contact with the first connect screw  217  and the sealed chamber (not shown) between the cylinder base  211  and the connecting base  212  also maintains the calibrated pressure. The moment the pick-up tip  231  touches the tray or the platform at position B  32 , a reactive force causes the piston  233  to move upward and the piston  233  in turn drives the rotation stop block  215  and the second connect screw  216  to move along and cause the second connect screw  216  and the first connect screw  217  to separate. Meanwhile, a sensing unit detects the contact between the pick-up tip  231  and the tray or the platform at position B  32 , and sends two instructions accordingly. The first instruction is to stop the air-suspended die sorter  20 &#39;s downward movement and the second instruction is to cause the first fitting  235  to be in air contact with the second solenoid valve  256  and allow said certain amount of air stored between the first solenoid valve  255  and the second solenoid valve  256  to enter the air passage (not shown) and terminate the vacuum condition, thereby allowing a die to be released.  
         [0041]    In light of the foregoing, the air-suspended die sorter  20  in accordance with the second preferred embodiment of the present invention is capable of moving between two operating positions  31  and  32  and achieving the purpose of picking up and releasing a die. By precisely controlling the pressure above and below the piston  233 , the present invention offers an air-suspended state for doing away with stress problems associated with using springs. The present invention further provides a novel buffer design for reducing friction and die impact often encountered in prior art applications.  
         [0042]    While the invention has been described in terms of a preferred embodiment, various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives that fall within the scope of the claims.