Abstract:
A tray-positioning device comprises a driving unit and a positioning unit, wherein the positioning unit provides a plurality of sidewalls that correspond to a plurality of upper sidewalls of a tray. By allowing the driving unit to move the positioning unit toward the tray or vice versa that said individual upper sidewalls are in close contact with the corresponding sidewalls, the tray-positioning device is capable of providing precise positioning for the tray.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a tray-positioning device and in particular relates to a tray-positioning device that utilizes the upper sidewalls of a tray for positioning. Having no mold lines or deformations commonly found on the lower sidewalls of a tray, the upper sidewalls possess smoother surfaces. Hence the tray-positioning device in the present invention is capable of providing higher degree of precision for tray positioning. 
     BACKGROUND OF THE INVENTION 
     Having undergone hundreds of processing steps, a semiconductor wafer is divided into a plurality of dies before being tested and packaged for delivery. To facilitate handling and management, dies are contained and carried around in a designated tray. 
     FIG. 1 shows a perspective view of a tray  1  for containing dies  2 . Being square-slab shaped, said tray  1  possesses a total of four stair-contoured sides, each having a lower sidewall  12  and an upper sidewall  14  such that the upper sidewall  14  is situated on the inner side and above the lower sidewall  12 . Said tray  1  provides a number of slots  16 , each capable of containing a die  2 . The step for transferring die  2  to slot  16  is loading. 
     In order to raise loading speeding and avoid human contact, most semiconductor plant uses robot arm for loading. If tray positioning is not accurate, the robot arm could not place individual dies on individual slots precisely as programmed. 
     To point out the importance of tray positioning, the loading process in die sorter is illustrated in the following. FIG. 2 shows a perspective view of a prior art die sorter  3 , which comprises a die tray  32 , a conveyor  34 , a push unit  36  and a robot arm  38 . Said die tray  32  is designated to hold a number of dies  2 , being divided from semiconductor wafers, for loading. Said conveyor  34  provides an input terminal  341 , an output terminal  342  and a sorter position  343 . By placing an empty tray  1  on conveyor  34  at terminal  341  and having it carried to the sorter position  343  for loading, followed by sending out an full stray  1  at output terminal  342  after said empty tray  1  is filled with dies. Said conveyor  34  can deliver one or a plurality of trays  1 , depending on the programmed loading operation. Prior art die sorter  3  as disclosed in FIG. 2 is useful for delivering a first tray  1  and a second tray  1   a.    
     Being L-shaped, said push unit  36  includes a pivot  361  and a push rod  362 , wherein said pivot  361  is located on one side of the conveyor  34  and said push rod  362  is situated above the conveyor  34  and at an angle with respect to the horizontal position. Knowing that the conveyor  34  can only deliver the first tray  1  and the second tray  1   a  to the ballpark sorter position  343 , pivot  361  will cause the push rod  362  to turn to a horizontal position and drive push rod  362  so as to push the second tray  1   a,  located behind the first tray  1 , and the first tray  1  to the ballpark sorter position  343 , simultaneously. 
     Said robot arm  38  is capable of loading dies by picking up die  2  from die tray  32  and placing it onto slot  16  until all slots of the first tray  1  and the second tray  1   a  are filled with dies  2 . 
     Being a plastic material, the first tray  1 &#39;s lower sidewall  12  often includes mold lines with rough surface. Being the outer rim of tray  1 , the lower sidewall  12  is prone to deformation caused by collision or heat. Using the lower sidewall  12 , which lacks the smooth surface, for positioning, the prior art tray  1  is incapable of being positioned accurately at the exact sorter position  343 , hence preventing the robot arm from loading individual dies precisely and causing production losses. 
     SUMMARY OF THE INVENTION 
     Aimed at resolving the above disadvantage, the main object of the present invention is to provide a tray-positioning device capable of utilizing the smoother upper sidewall, which has no mold lines or deformations commonly found on the lower sidewalls of a tray, for precision positioning. 
     The following Description and Designation of Drawings are provided in order to help understand the features and content of the present invention. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The accompanying drawings form a material part of this description, in which: 
     FIG. 1 is a perspective view of a tray  1 . 
     FIG. 2 is a top view of a die sorter  3 . 
     FIGS. 3A and 3B are perspective views of a tray-positioning device  4  in accordance with the first preferred embodiment of the present invention. 
     FIGS. 4A,  4 B and  4 C are views showing a tray-positioning device  5  in accordance with the second preferred embodiment of the present invention. 
     FIG. 5 is an exploded view of a tray-positioning device  6  in accordance with the third preferred embodiment of the present invention. 
     FIG. 6 is an operational view of a tray-positioning device  6  in accordance with the third preferred embodiment of the present invention. 
     FIG. 7 is a prospective view of a positioned tray-positioning device  6  in accordance with the third preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     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. 
     Please refer to FIGS. 3A and 3B, which illustrate a tray-positioning device  4  in accordance with the first preferred embodiment of the present invention. Said tray-positioning device  4  comprises a positioning unit  42  and a driving unit  44 . Said positioning unit  42  has four sidewalls  421 , which provide four guiding corners  423  on the inner side. Said guiding corner  423  and the upper sidewalls  14  are capable of fitting closely with each other. Said sidewall  421  has a pivot  425  and said driving unit  44  is connected to the pivot  425 . 
     Prior to the positioning process, the positioning unit  42  is set at a proper angle above the horizontal position with tray  1  located in the general area below it. When the driving unit  44  drives the positioning unit  42  and causes it to rotate around the pivot  425  towards the tray  1 . When the positioning unit  42  nears the horizontal position, the position of tray  1  is so adjusted that its upper sidewalls  14  are confined by the sidewalls  421  within the guiding corners  423 , thus accomplishing the positioning of tray  1  as shown in FIG.  3 B. 
     Please refer to FIGS. 4A,  4 B and  4 C, which illustrate a tray-positioning device  5  in accordance with the second preferred embodiment of the present invention. Capable of simultaneous positioning a first tray  1  and a second tray  1   a,  said tray-positioning device  5  comprises a first positioning unit  52 , a second positioning unit  54  and a driving unit  56 . The first positioning unit  52  has four first sidewalls  521 , which provide four guiding corners  523  on the inner side. The guiding corner  523  and the upper sidewalls  14  are capable of fitting closely with each other. The second positioning unit  54  has four second sidewalls  541 , one of which being connected to one of the four first sidewalls  521 . The second sidewalls  541  provide four guiding corners  543  on the inner side. Said guiding corner  543  and the upper sidewalls  14   a  are capable of fitting closely with each other. Provided by the first positioning unit  52  and the second positioning unit  54 , a pivot  527  allows the first positioning unit  52  and the second positioning unit  54  to rotate around it. 
     The tray-positioning device  5  in accordance with the second preferred embodiment of the present invention is positioned in a ballpark sorter position  343  on a conveyor  34 . Prior to the positioning process, the positioning unit  52  is set at a proper angle above the horizontal position. In one delivery, the die sorter  3  is capable of transferring a first tray  1  and a second tray  1   a.  After being adjusted by the push unit  36 , the first tray  1  and the second tray  1  a are located in the general area below the first positioning unit  52  and the second positioning unit  54 , respectively. When the first positioning unit  52  and the second positioning unit  54 , driven by the driving unit  56 , rotate to the horizontal position, the position of first tray  1  and second tray  1   a  are so adjusted that the upper sidewalls  14  and the upper sidewalls  14   a  are confined by the first sidewalls  521  and the second sidewalls  541  within the first guiding corners  523  and the second guiding corners  543 , respectively, thus accomplishing the positioning of the first tray  1  and the second tray  1   a  as shown in FIG.  4 C. 
     Please refer to FIGS. 5,  6  and  7 , which illustrate an exploded view, an operational view and a perspective view of a tray-positioning device  6 , respectively, in accordance with the third preferred embodiment of the present invention. Said tray-positioning device  6  comprises a first driving unit  62  and a positioning unit  64 . The first driving unit  62  includes a cylinder  621  and a tray push-pull rod  623 , being secured to the cylinder  621 . The positioning unit  64  has a positioning base  641 , a positioning block  642 , a first positioning spring  643  and a second positioning spring  644  wherein said positioning block  642  further comprises an extruded edge stopper  645 . The extruded edge stopper  645  and the second positioning spring  644  are provided in proper locations on the positioning base  641 . The first positioning spring  643  is secured to the tray push-pull rod  623 . A third sidewall  646  and a fourth sidewall  647  are provided on the right hand side of the second positioning spring  644  where it is turns and it is about to turn straight, respectively. A first sidewall  648  is provided on the positioning block  642  where it faces a tray  71 . A second sidewall  649  is provided on the inner side of the extruded edge stopper  645 . The first sidewall  648  and the second sidewall  649  are perpendicular to each other. 
     Please refer to FIGS. 6 and 7, which illustrate an operational view and a perspective view of a tray-positioning device  6 , respectively, in accordance with the third preferred embodiment of the present invention. A tray  71  provides a first upper sidewall  711 , a second upper sidewall  712 , a third upper sidewall  713 , and a first lower sidewall  714  wherein the first upper sidewall  711  and the second upper sidewall  712  are in parallel with the third upper sidewall  713  and the first lower sidewall  714 , respectively, and the first upper sidewall  711  is in perpendicular to the second upper sidewall  712 . Driven by a second driving unit  73 , the tray  71  located at  72 -input output location is moved to the general area on the positioning base  64  as shown in FIG.  7 . The first positioning spring  643  is situated behind the tray  71  and the tray  71  is located between the positioning block  642  and the first positioning spring  643 . Meanwhile, the first upper sidewall  711  is situated between the third sidewall  646  of second positioning spring  644  and the second sidewall  649  of the extruded edge stopper  645 . Responding to a positioning instruction, the cylinder  621  drives the tray push-pull rod  623  to pull the first positioning spring  643  such that the first positioning spring  643  hooks on the tray  71  and cause it to move toward the positioning block  642 . As it nears the first sidewall  648  of the positioning block  642 , the first upper sidewall  711  of the tray  71  has just passed entrance between the third sidewall  646  of the second positioning spring  644  and the second sidewall  649  of the extruded edge stopper  645  and is about to enter an area bonded by the fourth sidewall  647  of second positioning spring  644  and the second sidewall  649  of the extruded edge stopper  645  for containing the tray  71 . When the tray  71  further approaches, the pulling force by the first positioning spring  643  causes the first upper sidewall  711  of the tray  71  to be in close contact with the first sidewall  648  of the positioning block  642 . By bringing the first upper sidewall  711  and the second upper sidewall  712  of the tray  71  to be in close contact with the first sidewall  648  and the second sidewall  649 , respectively, the present invention establishes the first upper sidewall  711  and a second upper sidewall  712  as the bases for precision positioning of the tray  71  in FIG.  8 . 
     It is apparent that, by utilizing tray positioning devices  4 ,  5  or  6 , the tray  3  is capable of achieving elevated precision for positioning, improving the successful loading rate by the robot arm  38  and lowering the production cost. 
     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.