Patent Publication Number: US-2023152368-A1

Title: Picker device

Description:
TECHNICAL FIELD 
     The present invention relates to a picker device, and more particularly, to a picker device used to transfer a transfer target object such as a semiconductor element. 
     BACKGROUND ART 
     In general, after semiconductor elements are manufactured through a semiconductor process, the semiconductor elements are tested before shipment. That is, when there are an internal defect of a semiconductor element wrapped with a package as well as an external defect thereof, the performance thereof is fatally affected. Accordingly, various tests including external defect inspections as well as electrical operation tests are performed on semiconductor elements. 
     A picker device may be configured to apply vacuum pressure to pickers arranged in at least one line to adsorb semiconductor elements and release the vacuum pressure from the pickers to detach the semiconductor elements. Sizes of semiconductor elements may vary for each type, and accordingly, a tray may be configured to accommodate semiconductor elements having various sizes according to a Joint Electron Device Engineering Council (JEDEC) standard. 
     In the tray, since an interval between tray pockets for accommodating semiconductor elements is changed according to the sizes of the semiconductor elements, a picker device may also be formed in a variable type in which an interval between pickers is adjusted according to the interval between the tray pockets. 
     Meanwhile, with the advancement of technology, semiconductor elements tend to have been miniaturized so as to be variously applied to next-generation electronic devices and the like. Accordingly, in a tray, an interval between tray pockets may be narrow to accommodate miniaturized semiconductor elements. In this case, the number of tray pockets in an arrangement direction of the pickers may be greater than the number of the pickers, and thus efficiency of transferring the semiconductor elements may decrease. 
     In order to solve such a problem, the number of pickers can be increased according to the number of tray pockets according to an arrangement direction of the pickers, but the size of the picker should be decreased according to an interval between the tray pockets. However, as the size of the picker decreases, the adsorptive power to a semiconductor element decreases, which makes it difficult to stably adsorb a relatively large semiconductor element. 
     DISCLOSURE 
     Technical Problem 
     The present invention is directed to providing a picker device capable of flexibly coping with a situation in which a transfer target object is accommodated in a tray. 
     Technical Solution 
     According to an embodiment of the present invention, a picker device includes a picker support, pickers, and a sub-nozzle docking module. The pickers are arranged in a line on the picker support and each include a main nozzle to which vacuum pressure is applied to or released from a lower end thereof and a lift actuator supported on the picker support to elevate the main nozzle. The sub-nozzle docking module is docked to or undocked from the main nozzles and includes one or more sub-nozzles configured to adsorb or desorb transfer target objects when vacuum pressure is applied to or released from lower ends thereof, a docking mount configured to support the sub-nozzles at a lower end portion thereof to receive the vacuum pressure from the main nozzles in a state of being docked to the main nozzles and transmit the vacuum pressure to the sub-nozzles through a vacuum passage, and an attachment/detachment mechanism configured to attach and detach the docking mount to and from the picker support. 
     Advantageous Effects 
     According to the present invention, even when small transfer target objects are accommodated in a tray at an interval less than an interval between main nozzles or large transfer target objects are accommodated in the tray at an interval greater than the interval between the main nozzles, only a sub-nozzle docking module suitable for each situation can be replaced to stably pick up and transfer the corresponding transfer target objects, thereby flexibly coping with a situation in which the transfer target objects are accommodated in the tray. 
     According to the present invention, even when there is some height deviation between main nozzles due to various factors such as an assembly error of each of pickers with respect to a picker support or an assembly error of the picker itself, minimum heights of the main nozzles can be set to be the same due to an interaction between locking protrusions and a stopper. As a result, when a vision inspection is performed in a state in which transfer target objects are picked up by the main nozzles, an accurate inspection can be performed on the transfer target objects. 
     In addition, according to the present embodiment, when only a height of each of locking protrusions and a stopper is managed, minimum heights of main nozzles can be set to be the same, thereby easily managing the heights of the main nozzles. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view of a picker device according to one embodiment of the present invention. 
         FIG.  2    is an exploded perspective view of  FIG.  1   . 
         FIG.  3    is a cross-sectional view of a picker shown in  FIG.  1   . 
         FIG.  4    is a front cross-sectional view of  FIG.  1   . 
         FIG.  5    is a front cross-sectional view illustrating another example of a sub-nozzle docking module. 
         FIG.  6    is a rear view of the picker device shown in  FIG.  1   . 
         FIG.  7    is a perspective view of a picker device according to another embodiment of the present invention. 
         FIG.  8    is a perspective view illustrating the rear of the picker device shown in  FIG.  7   . 
         FIG.  9    is a perspective view illustrating pickers and a stopper of  FIG.  7   . 
         FIG.  10    is a cross-sectional view of the picker. 
         FIG.  11    is a rear view of  FIG.  7   . 
         FIG.  12    is a view for describing operations of locking protrusions and the stopper of  FIG.  11   . 
         FIG.  13    shows views for describing a process in which transfer target objects are inspected using a vision inspector in a state of being picked up by pickers. 
     
    
    
     MODES OF THE INVENTION 
     The present invention will be described in detail with reference to the accompanying drawings as follows. The same elements are assigned the same reference numerals. Repeated descriptions and descriptions of known functions and configurations which have been deemed to make the gist of the present invention unnecessarily obscure will be omitted below. The embodiments of the present invention are intended to fully describe the present invention to a person having ordinary knowledge in the art to which the present invention pertains. Accordingly, the shapes, sizes, and the like of elements in the drawings may be exaggerated to make the description clear. 
       FIG.  1    is a perspective view of a picker device according to one embodiment of the present invention.  FIG.  2    is an exploded perspective view of  FIG.  1   .  FIG.  3    is a cross-sectional view of a picker shown in  FIG.  1   .  FIG.  4    is a front cross-sectional view of  FIG.  1   . 
     Referring to  FIGS.  1  to  4   , a picker device  100  according to one embodiment of the present invention includes a picker support  110 , pickers  120 , and a sub-nozzle docking module  130 . 
     The picker support  110  supports the pickers  120 . The pickers  120  are arranged in a line on the picker support  110 . The pickers  120  are all arranged in a line in the same posture and supported on the picker support  110 . Each picker  120  includes a main nozzle  121  and a lift actuator  126 . 
     Vacuum pressure is applied to or released from a lower end of the main nozzle  121 . Vacuum pressure is applied to the lower end of the main nozzle  121  by a vacuum pressure generator, and the vacuum pressure applied to the lower end by the vacuum pressure generator may be released. The main nozzle  121  may adsorb or desorb a transfer target object  1  at the lower end in a state of being undocked from the sub-nozzle docking module  130 . Here, the transfer target object  1  may correspond to a semiconductor element or the like that is tested while accommodated in a tray  2 . 
     A nozzle lift body  122  may be mounted on an upper end of the main nozzle  121 . The nozzle lift body  122  may be elevated by the lift actuator  126  to elevate the main nozzle  121 . The nozzle lift body  122  may be connected to the vacuum pressure generator to receive vacuum pressure and transmit the vacuum pressure to the main nozzle  121  through an internal passage. 
     The main nozzle  121  may be attached to or detached from the nozzle lift body  122 . Accordingly, the main nozzle  121  may be easily replaced according to a change in type of the transfer target object  1 , damage thereto, or the like. For example, the main nozzle  121  may be attached to or detached from the nozzle lift body  122  in a one-touch method, thereby increasing convenience. 
     An upper portion of the main nozzle  121  may be formed such that a lower portion of the nozzle lift body  122  is inserted therein. Fixing protrusions  121   a  may be formed on any one of the upper portion of the main nozzle  121  and the lower portion of the nozzle lift body  122 , and fixing grooves  122   a  for fixing the fixing protrusions  121   a  may be formed in the other thereof. The lower portion of the nozzle lift body  122  may be inserted into the upper portion of the main nozzle  121  through a sealing material  123  to prevent a leakage of vacuum pressure. 
     The lift actuator  126  elevates the main nozzle  121  in a state of being supported on the picker support  110 . Accordingly, the main nozzle  121  may be lowered by the lift actuator  126  and docked to a docking mount  132  of the sub-nozzle docking module  130  and may be lifted by the lift actuator  126  and undocked from the docking mount  132 . In addition, when the main nozzle  121  directly picks up or puts down the transfer target object  1  in a state of being undocked from the docking mount  132 , the main nozzle  121  may be elevated by the lift actuator  126 . 
     The lift actuators  126  may independently elevate the corresponding main nozzles  121 . Accordingly, the main nozzles  121  may independently pick up and transfer the transfer target object  1  in a state of being undocked from the docking mount  132 . The lift actuator  126  may include a pneumatic cylinder  127 . 
     The pneumatic cylinder  127  may be a double-acting pneumatic cylinder. The double-acting pneumatic cylinder is formed such that a cylinder rod  127   b  is expanded or contracted with respect to a cylinder body  127   a  by compressed air selectively supplied by supply ports in both inner spaces of the cylinder body  127   a.    
     The cylinder body  127   a  may be supported on the picker support  110  in a posture in which the cylinder rod  127   b  expands or contracts at a lower side thereof. The cylinder rod  127   b  is connected to the nozzle lift body  122  through a connection bracket  128  and is expanded or contracted to elevate the nozzle lift body  122 , thereby elevating the main nozzle  121 . 
     The main nozzle  121  may be supported by the lift actuator  126  through a buffer member  129  to be buffered when docked to the docking mount  132 . The buffer member  129  may be mounted between the connection bracket  128  and the cylinder rod  127   b  to support the connection bracket  128  and the cylinder rod  127   b  with an elastic force. 
     The sub-nozzle docking module  130  is docked to or undocked from the main nozzles  121 . The sub-nozzle docking module  130  includes one or more sub-nozzles  131 , the docking mount  132 , and an attachment/detachment mechanism  136 . 
     As vacuum pressure is applied to or released from a lower end of the sub-nozzle  131 , the sub-nozzle  131  adsorbs or desorbs the transfer target object  1 . As an example, the number of the sub-nozzles  131  may be greater than the number of main nozzles  121  such that an interval between the sub-nozzles  131  is less than an interval between the main nozzles  121  in an arrangement direction of the pickers  120 . 
     The tray  2  is formed such that the number of tray pockets  2   a  in the arrangement direction of the pickers  120  is greater than the number of pickers  120  and an interval between the tray pockets  2   a  is less than a minimum interval between the main nozzles  121 , thereby accommodating a plurality of small transfer target objects  1  such as small semiconductor elements. In this case, the sub-nozzles  131  may be provided in the same number as the number of tray pockets  2   a  in an arrangement direction of the main nozzles  121  and may be arranged at the same interval as the interval between the tray pockets  2   a . The sub-nozzles  131  may be arranged in one or more lines. 
     For convenience of description, when a direction parallel to the arrangement direction of the pickers  120  is defined as an X-axis direction, and a direction perpendicular to the arrangement direction of the pickers  120  is defined as a Y-axis direction, an interval between the sub-nozzles  131  in the X-axis direction may be set to be the same as an interval between the tray pockets  2   a  in the X-axis direction. When the sub-nozzles  131  are provided in two or more lines, an interval between the sub-nozzles  131  in the Y-axis direction may be set to be the same as an interval between the tray pockets  2   a  in the Y-axis direction. 
     Accordingly, the sub-nozzles  131  are in one-to-one correspondence with the small transfer target objects  1  accommodated in the tray  2  at an interval that is less than the minimum interval between the main nozzles  121 , thereby stably transferring the small transfer target objects  1  by picking up at least one line of the small transfer target objects  1  at a time. The sub-nozzle  131  may be supported to be elevated in a state in which a tip  131   b  is inserted into a lower end portion of a body  131   a , and the tip  131   b  may be formed to receive an elastic force downward from a spring  131   c . Accordingly, the sub-nozzle  131  may serve as a buffer when the transfer target object  1  is adsorbed. 
     In a state in which the docking mount  132  supports the sub-nozzles  131  at a lower end portion thereof and is docked to the main nozzles  121 , the docking mount  132  receives vacuum pressure from the main nozzles  121  to transmit the vacuum pressure to the sub-nozzles  131  through a vacuum passage  134 . The docking mount  132  may fix the sub-nozzles  131  in a state in which upper portions of the sub-nozzles  131  are inserted into outlet ports provided at the lower end portion thereof. Here, in the docking mount  132 , portions into which the sub-nozzles  131  are inserted are sealed by a sealing material or the like to prevent a leakage of vacuum pressure. 
     Lower portions of the main nozzles  121  may be inserted into or separated from inlet ports of an upper end portion of the docking mount  132 . Here, the main nozzles  121  stand by upon being lifted to a higher level than a mounting height of the docking mount  132  by the lift actuators  126 . In this state, when the docking mount  132  is mounted on the picker support  110  by the attachment/detachment mechanism  136 , the main nozzles  121  may each be lowered from a standby position and inserted into the inlet ports of the docking mount  132 . 
     The lower portion of the main nozzle  121  may have an outer diameter that is less than that of an upper portion thereof and may be inserted into the inlet port of the docking mount  132 . The docking mount  132  may include a packing material  133   a  for sealing the lower portion of the main nozzle  121  in a state of being inserted into the inlet port. The packing material  133   c  may also perform a buffering function when the main nozzle  121  is lowered and inserted into the inlet port of the docking mount  132 . 
     The vacuum passage  134  of the docking mount  132  may be formed to equally transmit vacuum pressure provided from the main nozzles  121  to the sub-nozzles  131 . The vacuum passage  134  may include inlet passages  134   a  extending from the inlet ports, outlet passages  134   b  extending from the outlet ports, and a connection passage  134   c  for connecting the inlet passages  134   a  to all communicate with the outlet passages  134   b.    
     Accordingly, the docking mount  132  may equally divide vacuum pressure, which is provided from the main nozzles  121  through the inlet passages  134   a , to the outlet passages  134   b  through the connection passage  134   c  to transmit the vacuum pressure to the sub-nozzles  131 . Accordingly, all of the sub-nozzles  131  can pick up the transfer target objects  1  with the same vacuum pressure. As another example, although not shown, the outlet passages  134   b  may be divided into groups as many as the number of inlet passages  134   a , and the connection passage  134   c  may be formed to connect the outlet passages  134   b  of each group to each inlet passage  134   a  assigned to each group. 
     The docking mount  132  may include a mount body  132   a  and a pair of mount blocks  132   b . The mount body  132   a  supports the sub-nozzles  131  at a lower end portion thereof. The mount blocks  132   b  are attached to or detached from the picker support  110  by the attachment/detachment mechanism  136  in a state of being coupled to both sides of the mount body  132   a . The mount blocks  132   b  may be detachably coupled to the mount body  132   a  through bolting or the like. Therefore, the sub-nozzle docking module  130  can be used by replacing only the mount body  132   a  when the sub-nozzle  131  is replaced. 
     The picker support  110  may include support blocks  111  supporting both portions of the docking mount  132 , that is, outer surfaces of the mount blocks  132   b  through surface contact therewith. Accordingly, the docking mount  132  may be guided between the support blocks  111  and may be stably supported through surface contact between the support blocks  111  and the mount blocks  132   b.    
     The attachment/detachment mechanism  136  attaches or detaches the docking mount  132  to or from the picker support  110 . The attachment/detachment mechanism  136  may include reference pins  137  and coupling knobs  138 . The reference pins  137  may each protrude from the docking mount  132  and may be inserted into reference grooves  112  of the picker support  110 , thereby aligning the docking mount  132  at a reference position relative to the picker support  110 . 
     Accordingly, the docking mount  132  may always be assembled to the picker support  110  at the same position. A cross-sectional area of each of the reference pin  137  and the reference groove  112  may be formed in various shapes such as a circular shape or a polygonal shape. The reference pins  137  are formed in pairs, and thus the reference grooves  112  may also be formed in pairs. As another example, the reference pins  137  may be formed in the picker support  110 , and the reference grooves  112  may be formed in the docking mount  132 . 
     The coupling knobs  138  attach or detach the docking mount  132  to or from the picker support  110  when each screw coupling portion  138   a  passes through the docking mount  132  and is screwed to or unscrewed from the picker support  110 . The coupling knob  138  may include a circular head  138   b  fixed coaxially to the screw coupling portion  138   a . An anti-slip portion  138   c  may be formed on an outer peripheral portion of the circular head  138   b.    
     An operator can rotate the circular head  138   b  without slipping due to the anti-slip portion  138   c  while the outer peripheral portion of the circular head  138   b  is held in the operator&#39;s hand. The anti-slip portion  138   c  may have a concave-convex structure. A wrench groove  138   d  may be formed in a central portion of the circular head  138   b . The wrench groove  138   d  may be formed as a hexagonal groove or the like. 
     Therefore, when an operator mounts the docking mount  132  on the picker support  110 , while holding the anti-slip portion  138   c  of the circular head  138   b  in his or her hand, the operator can rotate the circular head  138   b  to temporarily couple the screw coupling portion  138   a  to the picker support  110  and then can insert a wrench rod into the wrench groove  138   d  to rotate the wrench rod and completely tighten the screw coupling portion  138   a  to the picker support  110 . 
     When an operator separates the docking mount  132  from the picker support  110 , the operator can insert a wrench rod into the wrench groove  138   d  to rotate the wrench rod and temporarily loosen the screw coupling portion  138   a  from the picker support  110  and then can rotate the circular head  138   b  to completely loosen the screw coupling portion  138   a  from the picker support  110  while holding the anti-slip portion  138   c  of the circular head  138   b  in his or her hand. 
     As another example, as shown in  FIG.  5   , in a sub-nozzle docking module  230 , the number of sub-nozzles  231  may be less than the number of main nozzles  121  in an arrangement direction of pickers  120 . A tray  2  is formed such that the number of tray pockets  2   a  in the arrangement direction of the pickers  120  is less than the number of pickers  120  and an interval between tray pockets  2   a  is greater than a maximum interval between the main nozzles  121 , thereby accommodating a plurality of large transfer target objects  1  such as large semiconductor elements. 
     In this case, the sub-nozzles  231  may be provided in the same number as the number of tray pockets  2   a  in an arrangement direction of the main nozzles  121  and may be arranged at the same interval as an interval between the tray pockets  2   a . The sub-nozzles  231  may be arranged in one or more lines. Accordingly, the sub-nozzles  231  are in one-to-one correspondence with the large transfer target objects  1  which are accommodated in the tray  2  at an interval greater than the maximum interval between the main nozzles  121 , thereby stably transferring the large transfer target objects  1  by picking up at least one line of the large transfer target objects  1  at a time. 
     A vacuum passage  234  of a docking mount  232  may be formed to equally transmit vacuum pressure provided from the main nozzles  121  to the sub-nozzles  231 . The vacuum passage  234  may include inlet passages  234   a  extending from inlet ports of the docking mount  232 , outlet passages  234   b  extending from outlet ports of the docking mount  232 , and a connection passage  234   c  for connecting the inlet passages  234   a  to all communicate with the outlet passages  234   b.    
     Accordingly, the docking mount  232  may equally divide vacuum pressure, which is provided from the main nozzles  121  through the inlet passages  234   a , to the outlet passages  234   b  through the connection passage  234   c  to transmit the vacuum pressure to the sub-nozzles  231 . Accordingly, all of the sub-nozzles  231  can pick up the transfer target objects  1  with the same vacuum pressure. As another example, although not shown, the inlet passages  234   a  may be divided into groups as many as the number of outlet passages  234   b , and the connection passage  234   c  may be formed to connect the inlet passages  234   a  of each group to each outlet passage  234   b  assigned to each group. 
     As described above, according to the picker device  100  of the present embodiment, when the small transfer target objects  1  are accommodated in the tray  2  at an interval less than the interval between the main nozzles  121  or the large transfer target objects  1  are accommodated in the tray  2  at an interval greater than the interval between the main nozzles  121 , only the sub-nozzle docking module  130  or  230  suitable for each situation is replaced without any change in configuration of the main nozzles  121 , thereby stably picking up and transferring the corresponding transfer target objects  1 . Accordingly, the picker device  100  of the present embodiment can flexibly cope with a situation in which the transfer target object  1  is accommodated in the tray  2 . 
     Meanwhile, referring to  FIG.  6    together with  FIGS.  1  and  2   , the picker device  100  may include a pitch variation mechanism  150  which varies a pitch between the pickers  120  in a state in which the sub-nozzle docking module  130  is undocked from the pickers  120 . The pitch variation mechanism  150  varies a pitch between the main nozzles  121  according to a pitch between the transfer target objects  1 , for example, a pitch between semiconductor elements accommodated in the tray  2 . The pitch variation mechanism  150  includes variable moving bodies  151 , a foldable link  152 , and a link actuator  153 . 
     The variable moving bodies  151  are fixed to the pickers  120  in a state of being spaced from each other. The variable moving bodies  151  may be fixed to the lift actuators  126 . The variable moving bodies  151  are slidably supported on the picker support  110  by a linear guide  151   a  in a horizontal direction parallel to the arrangement direction of the pickers  120 . 
     The foldable link  152  may include first link members  152   a  hinge-coupled in a zigzag shape and second link members  152   b  which are hinge-coupled in a zigzag shape and of which central portions are hinge-coupled to and symmetrically intersect central portions of the first link members  152   a . The hinge-coupled central portions of the first link members  152   a  and the second link members  152   b  may be fixed to the variable moving bodies  151 . 
     In the foldable link  152 , when hinge-coupled portions of the first link members  152   a  are folded, and concurrently, hinge-coupled portions of the second link members  152   b  are folded, the hinge-coupled central portions of the first link members  152   a  and the second link members  152   b  move toward or away from each other, and thus the pitch between the pickers  120  can decrease or increase. As a result, the pitch between the main nozzles  121  can be varied. 
     The link actuator  153  folds the foldable link  152 . The link actuator  153  may include a pair of horizontal moving bodies  154 , a horizontal screw  155 , and a rotation motor  156 . 
     The horizontal moving bodies  154  are fixed to the variable moving bodies  151  at both outermost sides. The horizontal screw  155  is elongated and horizontally disposed in the arrangement direction of the pickers  120  to be rotatably supported on the picker support  110 . The horizontal screw  155  is screw-coupled to each of the horizontal moving bodies  154 . The horizontal screw  155  may move the horizontal moving bodies  154  toward or away from each other in a rotational direction to fold the foldable link  152 . 
     The rotation motor  156  provides a forward or reverse rotational force to the horizontal screw  155 . The forward or reverse rotational force of the rotation motor  156  may be transmitted to the horizontal screw  155  by a power transmitter  157 . The power transmitter  157  may include a driving pulley coaxially fixed to a driving shaft of the rotation motor  156 , a driven pulley coaxially fixed to the horizontal screw  155 , and a belt disposed over the driving pulley and the driven pulley to transmit the rotation of the driving pulley to the driven pulley. The pitch variation mechanism  150  may have various known configurations. 
     Although not shown, the picker device  100  may adjust a height of the pickers  120  by elevating the pickers  120  together through a picker lift mechanism. The picker lift mechanism may elevate the main nozzles  121  together by elevating the picker support  110 . The picker lift mechanism may include a typical linear actuator. 
     The picker device  100  may allow the pickers  120  to horizontally reciprocate together in the arrangement direction of the pickers  120  through a picker horizontal movement mechanism. The picker horizontal movement mechanism may allow the main nozzles  121  to horizontally reciprocate together by allowing the picker lift mechanism to horizontally reciprocate. The picker horizontal movement mechanism may include a typical linear actuator. 
       FIG.  7    is a perspective view of a picker device according to another embodiment of the present invention.  FIG.  8    is a perspective view illustrating the rear of the picker device shown in  FIG.  7   .  FIG.  9    is a perspective view illustrating pickers and a stopper of  FIG.  7   .  FIG.  10    is a cross-sectional view of the picker.  FIG.  11    is a rear view of  FIG.  7   .  FIG.  12    is a view for describing operations of locking protrusions and the stopper of  FIG.  11   . 
     Referring to  FIGS.  7  to  12   , a picker device  300  according to one embodiment of the present invention includes a picker support  310 , pickers  320 , locking protrusions  330 , and a stopper  340 . 
     The picker support  310  supports the pickers  320 . The pickers  320  are all arranged in a line in the same posture and supported on the picker support  310 . Each picker  320  includes a main nozzle  321  and a lift actuator  326 . 
     The main nozzle  321  adsorbs or desorbs a transfer target object  1  through a lower end thereof. The main nozzle  321  may receive negative pressure from a pneumatic supply to adsorb the transfer target object  1  and may receive positive pressure from the pneumatic supply to desorb the transfer target object  1 . 
     A nozzle lift body  322  may be mounted on an upper end of the main nozzle  321 . The nozzle lift body  322  may be elevated and supported by the lift actuator  326  to guide the main nozzle  321  to be elevated. The nozzle lift body  322  may be connected to the pneumatic supply to receive negative or positive pressure from the pneumatic supply and transfer the negative or positive pressure to the main nozzle  321  through an internal flow path. 
     The lift actuator  326  elevates the main nozzle  321  in a state of being supported on the picker support  310 . In addition, when the main nozzle  321  picks up or puts down the transfer target object  1 , the main nozzle  321  may be elevated by the lift actuator  326 . In addition, the main nozzle  321  may be lowered by the lift actuator  326  in a state in which the transfer target object  1  is picked up, thereby allowing a test to be performed on the transfer target object  1  in a state in which a minimum height of the main nozzle  321  is limited by the locking protrusion  330  and the stopper  340 . 
     The lift actuators  326  may independently elevate the corresponding main nozzles  321 . Accordingly, the main nozzles  321  may independently pick up and transport the transfer target object  1 . The lift actuator  326  may include a pneumatic cylinder  327 . 
     The pneumatic cylinder  327  may be a double-acting pneumatic cylinder. The double-acting pneumatic cylinder is formed such that a cylinder rod  327   b  is expanded or contracted with respect to a cylinder body  327   a  by compressed air selectively supplied by supply ports in both inner spaces of the cylinder body  327   a.    
     The cylinder body  327   a  may be supported on the picker support  310  in a posture in which the cylinder rod  327   b  expands or contracts at a lower side thereof. A nozzle lift body  322  may vertically pass through one side of the cylinder body  327   a  and thus may be supported to be elevated. The cylinder rod  327   b  is connected to the nozzle lift body  322  through a connection bracket  328  and is expanded or contracted to elevate the nozzle lift body  322 , thereby elevating the main nozzle  321 . 
     The main nozzle  321  may be supported by the lift actuator  326  through a buffer member  329  to be buffered when the corresponding locking protrusion  330  is caught by the stopper  340 . When the connection bracket  328  is fixed to the nozzle lift body  322  and the cylinder rod  327   b  is supported to be elevatable, the buffer member  329  may be mounted between the connection bracket  328  and the cylinder rod  327   b  to support the connection bracket  328  and the cylinder rod  327   b  with an elastic force. 
     As another example, when the connection bracket  328  is fixed to the cylinder rod  327   b  and supports the nozzle lift body  322  to be elevatable, the buffer member  329  may be mounted between the connection bracket  328  and the nozzle lift body  322  to support the connection bracket  328  and the nozzle lift body  322  with an elastic force. The buffer member  329  may be formed as a coil spring or the like. 
     The locking protrusions  330  are formed at the same level in the main nozzles  321 . The locking protrusions  330  are formed to protrude from side portions of the main nozzles  321  in the same direction. The locking protrusion  330  is caught by the stopper  340  when the main nozzle  321  is lowered, thereby limiting a minimum height of the main nozzle  321  together with the stopper  340 . 
     A lower surface of the locking protrusion  330  may be formed in a flat shape parallel to a horizontal surface to be in stable contact with an upper surface of the stopper  340 . The locking protrusion  330  may be more firmly connected to the main nozzle  321  because a portion thereof connected to the main nozzle  321  has a relatively wide width. The locking protrusion  330  may be integrally formed with the main nozzle  321  but may be separately manufactured and assembled to the main nozzle  321 . 
     The stopper  340  is mounted on the picker support  310  to catch the locking protrusions  330  thereunder to equally limit the minimum heights of the main nozzles  321  when the main nozzles  321  are lowered by the lift actuators  326 . The stopper  340  may have a shape horizontally elongated in an arrangement direction of the main nozzles  321 , and both end portions thereof are fixed by the picker support  310 , thereby allowing the locking protrusions  330  of the main nozzles  321  to be commonly caught. 
     The upper surface of the stopper  340  may be formed in a flat shape parallel to a horizontal plane, thereby allowing all of the locking protrusions  330  to be caught at the same level. Accordingly, the upper surface of the stopper  340  serves as a reference for limiting the minimum height of each of the main nozzles  321 . 
     The stopper  340  may be made of a material, such as a metal, which is strong against deformation when pressed by the locking protrusions  330 . The stopper  340  is illustrated in a shape in which a central portion has a constant cross-sectional area in a longitudinal direction but may be formed in a shape that is strong against deformation, such as a shape in which a lower portion is expanded from both edges toward a center. The stopper  340  has both ends bolted to the picker support  310  and thus can be easily replaced. 
     As described above, according to the present embodiment, even when there is some height deviation between the main nozzles  321  due to various factors such as an assembly error of each of the pickers  320  with respect to the picker support  310  or an assembly error of the picker  320  itself, minimum height of the main nozzles  321  may be set to be have the same due to an interaction between the locking protrusions  330  and the stopper  340 . In addition, according to the present embodiment, when only a height of each of the locking protrusions  330  and the stopper  340  is managed, the minimum heights of the main nozzles  321  can be set to be the same, thereby easily managing the heights of the main nozzles  321 . 
     In a further aspect, the picker device  300  may include a pitch variation mechanism  350  for varying a pitch between the pickers  320  as in the above-described embodiment. The pitch variation mechanism  350  includes variable moving bodies  351 , a foldable link  352 , and a link actuator  353 . The variable moving bodies  351  may be fixed to the lift actuators  326  through picker brackets  320   a.    
     The foldable link  352  may include first link members  352   a  hinge-coupled in a zigzag shape and second link members  352   b  which are hinge-coupled in a zigzag shape and of which central portions are hinge-coupled to and symmetrically intersect central portions of the first link members  352   a.    
     The link actuator  353  may include a pair of horizontal moving bodies  354 , a horizontal screw  355 , and a rotation motor  356 . A forward or reverse rotational force of the rotation motor  356  may be transmitted to the horizontal screw  355  by a power transmitter  357 . 
     Although not shown, the picker device  300  may adjust a height of the pickers  320  by elevating the pickers  320  together through a picker lift mechanism. The picker lift mechanism may elevate the main nozzles  321  together by elevating the picker support  310 . 
     The picker device  300  may allow the pickers  320  to horizontally reciprocate together in an arrangement direction of the pickers  320  through a picker horizontal movement mechanism. The picker horizontal movement mechanism may allow the main nozzles  321  to horizontally reciprocate together by allowing the picker lift mechanism to horizontally reciprocate. 
     An operation example of the above-described picker device  300  will be described with reference to  FIG.  13    as follows. 
     As shown in  FIG.  13   , the pickers  320  are lowered by the picker lift mechanism and the lift actuators  326  above a tray  2  to pick up the transfer target objects  1  accommodated in the tray  2 , such as semiconductor elements, through the main nozzles  321 . In such a process, the locking protrusions  330  of the main nozzles  321  are each caught by the stopper  340  so that minimum heights of the main nozzles  321  are equally limited. 
     In this state, after the pickers  320  are transferred to a vision inspector  3  by the picker horizontal movement mechanism, the semiconductor elements may be inspected using the vision inspector  3  in a state of being picked up by the main nozzles  321  of which minimum heights are set to be the same. In this case, since the semiconductor elements are all positioned at the same level with respect to a camera photographing portion of the vision inspector  3 , all of the semiconductor elements can be focused on a camera to be photographed clearly. As a result, the inspection of the semiconductor elements can be accurately performed. 
     Although the present invention has been described with reference to embodiments shown in the accompanying drawings, the embodiments are merely examples, and those skilled in the art will appreciate that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined only by the appended claims.