Abstract:
The present invention aims to provide a lightened reaction absorber or to provide a semiconductor assembling system with further shorter processing time and high productivity or high quality using the lightened reaction absorber. The present invention is based upon a reaction absorber provided with a counter mechanism equipped with a load unit moved in a predetermined direction by a first ball screw, a second ball screw that generates reactive force in a reverse direction to the predetermined direction and a driving unit having a driving motor that drives the first ball screw and the second ball screw, and has a characteristic of including a reaction absorbing unit with one end side equipped with a nut connected to the second ball screw and the other end side fixed to a unit base movable relatively to the counter mechanism.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a semiconductor assembling system and a reaction absorber, and particularly relates to a semiconductor assembling system to which a lightened reaction absorber can be provided and having high productivity. 
       BACKGROUND OF THE INVENTION 
       [0002]    As one semiconductor manufacturing system, there is a die bonder that bonds a semiconductor chip (a die) onto a board such as a lead frame. In the die bonder, a bonding head vacuum-suctions a die, raises it at high speed, horizontally moves it, lowers it and mounts it on the board. 
         [0003]    Generally, when a system is sped up, vibration by an object moving at high speed grows larger and precision at which the device aims cannot be acquired due to this vibration. For an example of the related art, JP-A-2004-263825 discloses a reaction absorber for reducing this vibration. In JP-A-2004-263825, as shown in  FIG. 7 , a method of adding a counterweight cw, driving two types of ball screws n 1 , n 2  different in a lead by a motor m, moving a load f of a processing head (for example, a bonding head device) and the counterweight cw in reverse directions as shown by arrows and preventing vibration is adopted. 
         [0004]    Generally, the mass of the counterweight and driving force have the relation of inverse proportion and in the related art, reverse momentum to driving is required to acquire the effect of damping. For example, when a load and the counterweight are equal in mass, as much energy for driving the counterweight as energy for driving the load is required and twice as much output of the driving motor is required. To reduce the energy for driving the counterweight, counter mass has only to be increased (when the counter mass is increased twice, the driving energy is reduced to a half); however, the weight of the reaction absorber is increased. In addition, the whole weight including the weight of the driving system that supplies the driving energy and the weight of the counter is also increased. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention is made in view of the above-mentioned problem and a first object of the present invention is to provide a lightened reaction absorber. 
         [0006]    Further, a second object of the present invention is to provide a semiconductor assembling system with further shorter processing time and high productivity or high quality using the lightened reaction absorber. 
         [0007]    To achieve the first object of the present invention, a reaction absorber according to the present invention has a first characteristic that the reaction absorber is provided with a base, a support fixed to the base, a power source, a load unit that is moved by the power source, a counter mechanism that includes the power source and the load unit and relatively moves in relation to the load unit by the power source and a supporting member that is provided to the support and movably supports the counter mechanism. 
         [0008]    The reaction absorber according to the present invention has a second characteristic that the load unit is moved via a first ball screw by the operation of the power source and the counter mechanism is movably supported via a second ball screw by the support. 
         [0009]    The reaction absorber according to the present invention has a third characteristic that the reaction absorber is provided with a base, a support fixed to the base, a counter mechanism equipped with a first ball screw, a load unit moved in a predetermined direction by the first ball screw, a second ball screw that generates reactive force in a reverse direction to the predetermined direction and a driving unit equipped with a power source that drives the first ball screw and the second ball screw, a supporting member that is provided to the support and supports the counter mechanism movably by the second ball screw and a reaction absorbing unit that rotatably supports one end of the first ball screw and one end of the second ball screw and is fixed to the unit base which is movable relatively to the counter mechanism. 
         [0010]    To achieve the object, the first ball screw and the second ball screw are aligned and are provided with a lead screw a thread of which is cut in the same direction. 
         [0011]    Further, the unit base is fixed to prevent movement and the counter mechanism is moved along the unit base. 
         [0012]    The power source directly or indirectly drives one end of one of the first ball screw and the second ball screw or respective one ends of the first ball screw and the second ball screw. In this case, “indirectly” means that the ball screw is connected to the power source via a gear mechanism or a belt mechanism. “Directly” means that the ball screw is directly connected to the power source without a gear mechanism or a belt mechanism. 
         [0013]    The first ball screw and the second ball screw are arranged in parallel. 
         [0014]    A lead of the first ball screw is larger than a lead of the second ball screw. 
         [0015]    Further, to achieve the second object of the present invention, the semiconductor assembling system has a characteristic that the semiconductor assembling system is a die bonder and the reaction absorber is applied to at least one direct acting unit out of a bonding head, a preforming head and a wafer ring holder respectively with which the die bonder is provided in addition to the above-mentioned characteristics. 
         [0016]    According to the present invention, the lightened reaction absorber can be provided. 
         [0017]    Further, according to the present invention, the semiconductor assembling system with further shorter processing time and high productivity or high quality can be provided using the lightened reaction absorber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  shows the basic configuration of an X-direction reaction absorber equivalent to a first embodiment of the present invention; 
           [0019]      FIG. 2  shows an example of the operation of the X-direction reaction absorber shown in  FIG. 1 ; 
           [0020]      FIG. 3  is a schematic top view showing a die bonder equivalent to one embodiment of the present invention and a bonding head device; 
           [0021]      FIG. 4  shows the basic configuration of a Z-direction reaction absorber equivalent to a second embodiment of the present invention; 
           [0022]      FIG. 5  shows the basic configuration of a reaction absorber equivalent to a third embodiment of the present invention; 
           [0023]      FIG. 6  shows the basic configuration of a reaction absorber equivalent to a fourth embodiment of the present invention; and 
           [0024]      FIG. 7  shows a reaction absorber in the related art. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    Referring to the drawings, an embodiment of the present invention will be described using a die bonder as a semiconductor assembling system for an example below. 
         [0026]      FIG. 3  is a schematic top view showing the die bonder  10  equivalents to one embodiment of the present invention and also shows the details of a bonding head device  32 . The die bonder is roughly provided with a wafer supply unit  1 , a workpiece supplying/feeding unit  2  and a die bonding unit  3 . 
         [0027]    The wafer supply unit  1  is provided with a wafer cassette lifter  11  and a wafer ring holder  12 . The wafer cassette lifter  11  is provided with a wafer cassette (not shown) filled with wafer rings and supplies a wafer ring to the wafer ring holder  12 . The wafer ring holder  12  stretches a wafer tape that is held by the wafer ring downward to widen an interval between dies, helping the down side of a die be thrust up a die from the downside of the die by a thrusting unit, thus enhances the pickup performance of the die in a bonding process described later. Further, the wafer ring holder  12  is arranged on an X-Y direct acting table, directly moves to the next die position after pickup, to be ready for the next pickup. 
         [0028]    The workpiece supplying/feeding unit  2  is provided with a stack loader  21 , a frame feeder  22  and an unloader  23 . A workpiece (a lead frame) supplied to the frame feeder  22  by the stack loader  21  is fed to the unloader  23  via two processing positions on the frame feeder  22 . 
         [0029]    The die bonding unit  3  is provided with a preformer  31  and the bonding head device  32 . The preformer  31  applies a die adhesive to the workpiece fed by the frame feeder  22 . The bonding head device  32  picks up the die from the wafer ring holder  12 , raises it, moves it in horizontally, and moves it to the bonding point on the frame feeder  22 . The bonding head device  32  lowers the die and bonds it onto the workpiece to which the die adhesive is applied. 
         [0030]    The bonding head device  32  is provided with an X-direction reaction absorber  6  that moves a bonding head (see  32   a  in  FIG. 4 ) between a pickup position in the wafer ring holder  12  and the bonding point, that is, in an X direction and a Z-direction reaction absorber  7  that is fixed to the X-direction reaction absorber  6  (that functions as a load) and moves the bonding head  32   a  vertically (in a Z direction). 
         [0031]    Referring to the drawings, embodiments of a reaction absorber that characterizes the present invention will be described below.  FIG. 1  shows the basic configuration of the X-direction reaction absorber  6  equivalent to the first embodiment.  FIG. 2  shows a state in which a load unit  62  that fixes the Z-direction reaction absorber  7  is moved rightward. 
         [0032]    The X-direction reaction absorber  6  is roughly provided with the load unit  62  which is an object of movement and which is shown inside a broken line, a driving unit  61  that laterally moves the load unit as shown by arrows in  FIG. 1 , a reaction absorbing unit  63  that functions as a counter for reducing vibration by the load unit and a unit base  64  that supports or fixes these. 
         [0033]    The driving unit  61  is provided with a ball screw  61   a  on the load side that moves the load unit  62 , a ball screw  61   b  on the reaction absorption side coupled to the ball screw  61   a  on the load side via a coupler  61   f  for moving the reaction absorbing unit  63 , a driving motor  61   c  that rotates both ball screws, a U-shaped driving fixed plate  61   d  that supports the driving motor and both ball screws and a base guide  61   e  that enables the driving fixed plate to move on the unit base  64 . 
         [0034]    The load unit  62  is provided with a load fixing base  62   a  that fixes or supports the reaction absorber  7  which is equipped with the bonding head  32   a  (see  FIG. 4 ) at an end and which functions as a load, a load nut  62   b  fixed to the load fixing base and moved on the ball screw on the load side and a load guide  62   c  that makes the load unit  62  smoothly moved over the driving fixed plate  61   d  by the load nut. According to this configuration, the load unit  62  is laterally moved by the rotation of the ball screw  61   a  on the load side as shown by the arrows in  FIG. 1 . 
         [0035]    Both threads of the ball screw  61   b  on the reaction absorption side and the ball screw  61   a  on the load side are cut in a forward (the same) direction. Further, the ratio M of a lead Rh of the ball screw  61   b  on the reaction absorption side to a lead Rd of the ball screw  61   a  on the load side has relation shown in an expression (1). 
         [0000]      R=Rd/Rh:R&gt;1   (1)
 
         [0036]    The reaction absorbing unit  63  is provided with a reaction absorption nut  63   a  moved on the ball screw  61   b  on the reaction absorption side on the side of one end and reaction absorbent  63   b  fixed to the unit base  64  on the side of the other end. 
         [0037]    The unit base  64  is fixed to the bonding head device  32  and fixes the reaction absorbing unit  63  as described above. Further, the unit base supports a counter mechanism  8  provided with the driving unit  61  and the load unit  62  respectively shown inside a thick line movably in directions shown by the arrows by the base guide  61   e.    
         [0038]      FIG. 2  shows an example of the operation of the reaction absorber  6  provided with the above-mentioned configuration.  FIG. 2  shows the example that the load unit  62  is moved rightward as shown by an arrow A by sequentially rotating the ball screw  61   a  on the load side and the ball screw  61   b  on the reaction absorption side in the same direction. When the load unit is moved leftward, reverse operation is executed as shown in parentheses. 
         [0039]    In a case shown in  FIG. 2 , the load unit  62  is moved rightward (leftward) by the rotation of the ball screw  61   a  on the load side and the ball screw  61   b  on the reaction absorption side and the reaction absorbing unit  63  also tries to move rightward (leftward). However, since the reaction absorbing unit  63  is fixed to the unit base  64 , reactive force is conversely applied to the ball screw  61   b  on the reaction absorption side and the ball screw on the reaction absorption side is moved leftward as shown by an arrow C for the unit base  64 . As a result, the counter mechanism  8  shown inside the thick line is moved over the unit base  64  by the base guide  61   e  leftward (rightward) as shown by an arrow B. 
         [0040]    In this case, the load unit  62  also tries to move leftward (rightward) according to the movement of the driving unit  61 . However, since the lead (the travel) of the ball screw  61   a  on the load side is larger as clear from the relation shown in the expression (1), the load unit  62  is moved rightward (leftward) as shown by the arrow A. A sufficient operational range can be acquired by setting the ratio R of the leads shown in the expression (1) to an appropriate value. 
         [0041]    In this embodiment, as described above, the counter mechanism  8  shown inside the thick line in  FIG. 2  and provided with the driving unit  61  and the load unit  62  functions as a counter load moved in a reverse direction to the load unit  62 . That is, the mass Km of the counter mechanism  8  which accounts for the substantial whole of the reaction absorber functions as the counter load that absorbs the vibration. This is a characteristic of the first embodiment. When the ratio of the mass Km and the mass Fm of the load unit  62  shown inside the broken line is M (=Km/Fm), the vibration is better offset as the ratio M:R of M to the lead ratio R shown in the expression (1) comes closer to 1. Particularly, to acquire effectively high offset degree, it is desirable that the ratio of M:R is in a range of 0.95 to 1.05. In the description of the first embodiment, the ball screw  61   a  on the load side and the ball screw  61   b  on the reaction absorption side are rotated in the same direction. However, they may also be rotated in reverse directions. 
         [0042]    According to the first embodiment of the present invention, reverse vibration against vibration caused by the load unit is generated by the reaction absorbing unit and the vibration in operation can be reduced or offset. 
         [0043]    According to the first embodiment of the present invention, mass as a counter is not required to be added and the reaction absorber can be made light and compact. As a result, the driving of the reaction absorber can be sped up. 
         [0044]    Further, since the reaction absorber can be made light and compact, time until the vibration is reduced or offset can be reduced and cycle time can be sped up. Since the time until the vibration is reduced or offset is short, the bonding head can execute the next process after the vibration is offset without sacrificing the cycle time and therefore, the quality can be enhanced. 
         [0045]      FIG. 4  shows the basic configuration of a Z-direction reaction absorber  7  equivalent to a second embodiment of the present invention. The Z-direction reaction absorber  7  is provided with a function for suctioning a die with a bonding head  32   a  and for raising/lowering the die for bonding. The basic configuration of the Z-direction reaction absorber  7  is basically the same as that in the first embodiment shown in  FIG. 1 . However, the Z-direction reaction absorber has some different points. The second embodiment will be described based upon the different points below. In  FIG. 4 , the same reference numeral is allocated to a part having the same function as the part in the first embodiment. 
         [0046]    First, while the load in the first embodiment is the Z-direction reaction absorber  7  that raises/lowers the bonding head  32   a  shown in  FIG. 4 , a load in the second embodiment is the bonding head that raises/lowers an end of the Z-direction reaction absorber. 
         [0047]    Accordingly, secondly, in the Z-direction reaction absorber  7 , a load unit  62  provided with the bonding head is provided on the side of a pointed end and a reaction absorbing unit  63  is provided in the vicinity of a driving motor  61   c  at the base so as to facilitate raising/lowering the bonding head  32   a,  suctioning a die and bonding the die. 
         [0048]    Thirdly, a unit base  65  of the Z-direction reaction absorber  7  is equivalent to the load fixing base  62   a  of the X-direction reaction absorber  6  or is fixed to the load fixing base  62   a.    
         [0049]    The rest of the configuration and the rest of operation are similar to those in the first embodiment. In  FIG. 4 , as in  FIG. 2 , the inside of a thick black line shows a counter mechanism  8  which functions as a counter load and which is provided with the driving unit  61  and the load unit  62 , and the inside of a broken line shows the load unit  62 . 
         [0050]    In the second embodiment of the present invention, vibration in a reverse direction against vibration caused by the load unit is generated by the reaction absorbing unit and the vibration in operation can also be reduced or offset. 
         [0051]    Since the counter mechanism  8  which functions as the counter load is also raised/lowered in the second embodiment, the load carrying capacity of the driving motor appears to be increased at a glance. In the related art, however, since a counter having the same mass is also required to be raised/lowered, the load carrying capacity of the motor is unchanged. 
         [0052]    Further, also in the second embodiment of the present invention, mass as a counter is not required to be added and the reaction absorber can be made light and compact. As a result, the driving of the reaction absorber can be sped up. 
         [0053]    Further, since the Z-direction reaction absorber can be made light and compact, the X-direction reaction absorber  6  described in the first embodiment can be made lighter and more compact and the whole bonding head device  32  can be made light and compact. 
         [0054]    Furthermore, the throughput is enhanced because waiting time and low-speed driving time respectively in die bonding can be reduced by applying the direct acting bonding head device having degrees of freedom in two directions of the X direction and the Z direction described in the embodiments of the present invention to the die bonder  10  shown in  FIG. 3 . Further, since the vibration in die bonding can be reduced, the quality of a product, particularly die bonding precision, is enhanced. 
         [0055]    Generally, in the die bonder, in addition to the bonding head device, a preforming head device directly acts with degrees of freedom in the two directions of the X direction and the Z direction and a wafer ring holder directly acts with degrees of freedom in two directions of the X direction and a Y direction. X, Y and Z are reference signs allocated to facilitate the understanding of the description and the reference numerals themselves have no meaning. 
         [0056]    Accordingly, the throughput is enhanced because waiting time and low-speed driving time respectively in die bonding can be further reduced when the above-mentioned reaction absorber according to the present invention is also applied to the preforming head and the wafer ring holder. Further, since vibration in die bonding can be reduced, the quality of a product, particularly die bonding precision is further enhanced. 
         [0057]      FIG. 5  shows a reaction absorber  9  equivalent to a third embodiment which can be applied to the X-direction reaction absorber  6  and the Z-direction reaction absorber  7 . The basic operation and the basic configuration in the third embodiment are the same as those of the first and second embodiments. 
         [0058]    The third embodiment will be described in relation to points different from those in the first and second embodiments below. 
         [0059]    In the third embodiment, a ball screw  61   a  on the load side and a ball screw  61   b  on the reaction absorption side are not aligned and are arranged in parallel. To drive both ball screws in parallel, the driving force of a driving motor  61   c  is transmitted to the ball screw  61   b  on the reaction absorption side via gears  61   f   1 ,  61   f   2 . Since the driving force is transmitted via the gears, threads of the ball screw  61   a  on the load side and the ball screw  61   b  on the reaction absorption side are cut in reverse directions. As a result, a reaction absorbing unit  63  tries to move in the same direction as a load unit  62 . However, since the reaction absorbing unit  63  is fixed to a unit base  64 , the reaction absorbing unit is moved in a reverse direction to the load unit  62  based upon the unit base  64 . As a result, a counter mechanism  8  shown inside a thick line is also moved in the reverse direction to the load unit  62  over the unit base  64  by a base guide  61   e.    
         [0060]    In  FIG. 5 , the driving force is transmitted via the gears. When the driving force is transmitted via a timing belt, the similar operation to the operation shown in  FIG. 5  is acquired by cutting the threads in the same direction. 
         [0061]    Accordingly, in the third embodiment, vibration in a reverse direction against vibration caused by the load unit  62  is also generated by the reaction absorbing unit  63  by making the counter mechanism  8  function as a counter load and the vibration in the operation can be reduced or offset. 
         [0062]    Further, also in the third embodiment, since a new counter is not required to be provided, a reaction absorber can be made light and compact. As a result, the driving of the reaction absorber can be sped up. 
         [0063]    Further, in the third embodiment, the load unit  62  and the reaction absorbing unit  63  are arranged vertically in the drawing based upon the unit base  64 . As a result, the length of the movement of the reaction absorbing unit can be reduced. The arrangement is not limited to that shown in  FIG. 5  and for example, the load unit  62  and the reaction absorbing unit  63  may also be arranged in a direction of the depth of the drawing over the unit base  64 . 
         [0064]    The die bonder has been described as an example of the semiconductor assembling system. However, the present invention can also be applied to another semiconductor assembling system in which a processing head is operated at high speed. 
         [0065]      FIG. 6  shows a reaction absorber  5  equivalent to a fourth embodiment. In the fourth embodiment, a ball screw  61   b  on the reaction absorption side is arranged on the left side of a driving motor  61   c  and a ball screw  61   a  on the load side is arranged on the right side of the driving motor  61   c.  At this time, the driving motor  61   c,  the ball screw  61   a  on the load side and the ball screw  61   b  on the reaction absorption side are aligned to make each rotational center of the motor  61   c,  the ball screw  61   a  on the load side and the ball screw  61   b  on the reaction absorption side matched. Each one end of the ball screw  61   a  on the load side and the ball screw  61   b  on the reaction absorption side is rotatably supported by a driving fixed plate  61   d.    
         [0066]    In the fourth embodiment, the basic operation is the same as that in the first and second embodiments. 
         [0067]    The embodiments of the present invention have been described. The present invention includes various alternative examples, modification or transformation in a range not deviating from its object.