Abstract:
In an embodiment, an apparatus is configured to cut a tape, such as a spacing adhesive tape. The apparatus is easy to maintain and blade life is extended, and the quality of the cuts are superior. In an embodiment the method includes preparing a spacing adhesive tape used in a semiconductor manufacturing process, fixing the spacing adhesive tape to a worktable, and cutting the spacing adhesive tape using a pair of wheel-shaped blades.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This application claims the priority of Korean Patent Application No. 10-2005-0002461, filed on Jan. 11, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
         [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an apparatus for, and a method of, cutting a tape used in a semiconductor package, and more particularly, to an apparatus for and a method of, cutting a spacing adhesive tape used in a quarter die package.  
         [0004]     2. Description of the Related Art  
         [0005]     A die attaching process involves assembling a semiconductor package, and attaching individual semiconductor chips that have been separated from a wafer to a leadframe or a substrate in a printed circuit board (PCB) form. Generally, the die attaching process varies according to the type of semiconductor package. For example, in the case of a multi-chip package, adhesive tape functioning as a spacer is mounted on a semiconductor chip attached to a leadframe to attach another semiconductor chip directly on the semiconductor chip. This process is called a spacing adhesive tape mounting process.  
         [0006]     Referring to  FIG. 1 , in a quarter die package (QDP), a pair of semiconductor chips  38 A and  38 B are on a top surface of a chip pad  32  of a leadframe  36 , using spacing adhesive tape  42 A. In addition, another pair of semiconductor chips  38 C and  38 D are on a bottom surface of the chip pad  32 , using the spacing adhesive tape,  42 B. The semiconductor chips  38 A through  38 D are connected to a lead  34  of the leadframe  36  by a gold wire  40 . An epoxy mold compound  44  seals a portion of the gold wire  40 , the semiconductor chips, and the leadframe  38 , protecting them from external impacts.  
         [0007]     The semiconductor chips  38 A and  38 C are adhered to the chip pad  32  by film-type adhesive tape  46  respectively attached to bottom surfaces of the semiconductor chips  38 A and  38 C. In addition, the semiconductor chips  38 B and  38 D are respectively adhered to the semiconductor chips  38 A and  38 C by the film-type adhesive tape  46  respectively attached to bottom surfaces of the semiconductor chips  38 B and  38 D.  
         [0008]     The spacing adhesive tape  42 A and  42 B is interposed between the semiconductor chips  38 A and  38 B, and between the semiconductor chips  38 C and  38 D, respectively. Hence, the spacing adhesive tape  42 A,  42 B protects circuit areas of the semiconductor chips  38 A and  38 C and provides wire-bonding space for the semiconductor chips  38 A and  38 C.  
         [0009]     Referring to  FIGS. 2 and 3 , generally, the spacing adhesive tape  42  is wound around a reel  26 . The spacing adhesive tape  42  includes a polyimide film  22  as a basic material, or substrate, and adhesive layers  24  respectively formed on top and bottom surfaces of the polyimide film  22 . When the spacing adhesive tape  42  is exposed to a smooth surface at room temperature for more than 10-15 minutes, the spacing adhesive tape  42  is adhered to the smooth surface by the adhesive layers  24 . Since the spacing adhesive tape  42  is formed of polyimide, it is flexible. However, since the spacing adhesive tape  42  has a strong tensile force and rupture strength, when the spacing adhesive tape  42  is cut more than, say, 2000 times using an ultra-hard blade, even the ultra-hard blade becomes dulled and abraded.  
         [0010]      FIGS. 4A and 4B  are perspective views of a blade  20 A and  20 B, respectively, used to cut the spacing adhesive tape  42 . Specifically,  FIG. 4A  shows the blade  20 A before being used, and  FIG. 4B  shows the blade  20 B after being used. The blade  20 A is fixed to an apparatus for cutting spacing adhesive tape. The blade  20 A or  20 B cuts the spacing adhesive tape  42  by horizontally sliding within the apparatus, so a specific portion  21  of the blade  20 B may be unevenly abraded. Consequently, the blade  20 B lasts only for about 2000 cuts of the spacing adhesive tape  42 .  
         [0011]     In addition, if dust on the adhesive layers  23  of the spacing adhesive tape  42  is adhered to the blade  20 B and solidified, the spacing adhesive tape  42  is not cut uniformly. The spacing adhesive tape  42  may not be cut straight or may be cut diagonally. Therefore, in the spacing adhesive tape mounting process, blades must be frequently replaced, thus requiring a lot of time for maintenance and undermining the operating rate of the cutting apparatus.  
         [0012]      FIG. 5  is a sectional view of the QDP with a defect caused by poor cutting of the spacing adhesive tape  42 . Since the spacing adhesive tape  42  was not cut in a uniform size, space for wire bonding was not secured in the semiconductor chips  38 A and  38 C. As a result, the QDP became defective. Referring to  FIG. 5 , the spacing adhesive tape  42 A mounted on the semiconductor chip  38 A attached to the top surface of the chip pad  32  was not cut straight. Thus, the length of the cut spacing adhesive tape  42 A was extended. The spacing adhesive tape  42 B under the chip pad  32  was cut diagonally.  
         [0013]     In a multi-chip package like the QDP, the technology for cutting spacing adhesive tape uniformly is a key determiner of the defect rate of the QDP. The spacing adhesive tape  42 A and  42 B fixes the semiconductor chips  38 B and  38 D and, at the same time, provides space for wire-bonding the semiconductor chips  38 A and  38 C. Therefore, problems of the spacing adhesive tape  42  being pushed back and forth, not being cut straight, or having to be frequently replaced must be tackled to lower the defect rate and improve productivity.  
       SUMMARY OF THE INVENTION  
       [0014]     The present invention provides an apparatus for cutting spacing adhesive tape. The apparatus is easy to maintain, extends the lifespan of a blade, and cuts the spacing adhesive tape in a uniform size.  
         [0015]     The present invention also provides a method of cutting spacing adhesive tape, to easily maintain and extend the lifespan of a blade, and to cut the spacing adhesive tape in a uniform size. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments with reference to the attached drawings in which:  
         [0017]      FIG. 1  is a sectional view of a quarter die package (QDP) using a spacing adhesive tape;  
         [0018]      FIG. 2  is a perspective view of the spacing adhesive tape wound around a reel;  
         [0019]      FIG. 3  is a sectional view of the spacing adhesive tape;  
         [0020]      FIGS. 4A and 4B  are perspective views of a blade used to cut the spacing adhesive tape;  
         [0021]      FIG. 5  is a sectional view of the QDP with a defect caused by poor cutting of the spacing adhesive tape;  
         [0022]      FIG. 6  is a lateral view of a pair of wheel-shaped blades for illustrating a method of cutting spacing adhesive tape according to an embodiment of the present invention;  
         [0023]      FIG. 7  is a perspective view of the apparatus for cutting the spacing adhesive tape, according to an embodiment of the present invention;  
         [0024]      FIG. 8  is a top view of the apparatus of  FIG. 7 ;  
         [0025]      FIG. 9  is a lateral view of the two wheel-shaped blades included in the apparatus for dynamically illustrating operating mechanisms of the two wheel-shaped blades;  
         [0026]      FIG. 10  is another lateral view of the two wheel-shaped blades included in the apparatus for dynamically illustrating operating mechanisms of the two wheel-shaped blades;  
         [0027]      FIG. 11  is a top view of the apparatus for illustrating directions of forces generated when the spacing adhesive tape is cut by the two wheel-shaped blades;  
         [0028]      FIG. 12  is a perspective view of a blade-driving unit. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]     The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth therein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.  
         [0030]      FIG. 6  is a lateral view of a pair of wheel-shaped blades  102 A and  102 B for illustrating a method of cutting spacing adhesive tape according to the present invention. To begin, a spacing adhesive tape  112  is prepared. The spacing adhesive tape  112  is fixed to a worktable  106  of  FIG. 7  included in an apparatus  100  for cutting the spacing adhesive tape, and is cut using the two rotating wheel-shaped blades  102 A and  102 B. Since a portion of the wheel-shaped blades  102 A and  102 B overlaps (indicated by A in  FIG. 6 ), the spacing adhesive tape  112  can be cut in a uniform size.  
         [0031]     In the descriptions below, the term ‘tape’ may be used to represent the spacing adhesive tape, as well as other types of tape that may be used in other embodiments of the invention. Additionally, the term ‘blades’ may be used to collectively represent the two wheel-shaped blades  102 A and  102 B. The term ‘blade’ may refer to either of the two blades, the context clearly noting which of the two blades,  102 A or  102 B, is being referred to.  
         [0032]     The two rotating blades  102 A and  102 B shuttle straight in an F 1  direction and rotate in F 2  directions, as shown in  FIG. 6 . In other words, the upper blade  102 A rotates in a clockwise direction and the lower blade  102 B rotates in a counter-clockwise direction, to cut the tape  112 . The rotating blades  102 A and  102 B cut the tape  112  by moving forward in the direction indicated by F 1  and cut the tape  112  again by moving backward to their original position in the direction indicated by F 1 . Therefore, the number of units into which the tape  112  is cut per hour can be increased.  
         [0033]      FIG. 7  is a perspective view of the apparatus  100  for cutting the tape  112 .  FIG. 8  is a top view of the same apparatus  100 . Referring to  FIGS. 7 and 8 , the apparatus  100  includes a body having the worktable  106 . The body includes a controller (not shown) to control the entire operation of the apparatus  100  and various driving devices controlled by the controller, such as a motor needed to drive the apparatus  100 , a stepping motor, and a vacuum device.  
         [0034]     In addition, the apparatus  100  includes a tape-moving unit  108  that may continuously move or hold the tape  112  in a Y-axis direction on the worktable  106 . The apparatus  100  further includes a blade recess  104  which is a slot or groove in the worktable  106  in an X-axis direction substantially perpendicular to the tape-moving unit  108 .  
         [0035]     The apparatus  100  also includes the two blades  102 A and  102 B. These blades cut the tape  112  by rotating in the blade recess  104  in the X-axis direction. The blades  102 A and  102 B are connected to a blade-driving unit  114  driven by a motor.  
         [0036]     The apparatus  100  may further include vacuum holes  110 , which fix the tape  112  to a top surface of the worktable  106  so the blades  102 A and  102 B can firmly cut the tape  112 . The tape-moving unit  108 , which traverses the blade recess  104 , may further include a picker  118 , shown in of  FIG. 8 . The picker  118  may move tape section  112 A which are pieces of tape  112  that have been cut. The apparatus  100  may further include, in a lower part of the blade recess  104 , a dust remover, for example, a vacuum device  116 , shown in  FIG. 8 , for processing dust produced when cutting the tape  112 .  
         [0037]     The tape  112  may encompass many types of tape used in semiconductor device-packaging processes. For example, the tape  112  may be formed of polyimide used in the QDP manufacturing process and may include adhesive layers formed on both sides of the polyimide.  
         [0038]     The process of cutting the tape  112  to a uniform size will now be described in detail. The tape-moving unit  108  moves in an M 1  direction and then is fixed by the vacuum holes  110  connected to a vacuum, such as the vacuum device  116  of  FIG. 8 . The two rotating blades  102 A and  102 B move in the F 1  direction in the blade recess  104  that is perpendicular to the fixed tape  112  to cut the tape  112 .  
         [0039]     Consequently, the tape section  112 A, into which the tape  112  is cut, is produced in an upper part of the tape-moving unit  108 . The tape section  112 A may be moved by the picker  118  to be stored or to later be used to assemble a QDP, such as that shown in  FIG. 1 .  
         [0040]     Repeating the above process, the tape  112  is again moved in the M 1  direction and fixed by the vacuum holes  110 . Then the two rotating blades  102  again move in the F 1  direction, cut the tape  112 , and return to their original positions. In this process, the rotating blades  102  cut the tape  112  fixed by the vacuum-sucking holes  110  again to produce another tape section  112 A, which is preferably identical to the last cut tape section  112 A. The tape section  112 A is again moved by the picker  18 . Hereinafter, the process of cutting the tape  112  is repeated.  
         [0041]     Dust generated in the process of cutting the tape  112  may be collected and removed by the dust remover, for example, the vacuum-sucking device  116 , through the blade recess  104 .  
         [0042]      FIG. 9  is a lateral view of the two blades  102 A and  102 B included in the apparatus  100 . If the two blades  102 A and  102 B move in the F 1  direction without rotating to cut the tape  112 , a force F contact  is applied to the two wheel-shaped blades  102 A and  102 B in a direction perpendicular to the two wheel shaped blades  102 A and  102 B. In addition, a force F 3 , i.e., F contact *cos θ, is applied in a direction indicated by F 3 , which is a direction in which the tape  112  is cut.  
         [0043]      FIG. 10  is another lateral view of the two blades  102 A and  102 B. A force produced by the two blades  102 A and  102 B while moving forward in the F 1  direction and rotating will now be considered.  
         [0044]     The moment when the two blades  102 A and  102 B contact the tape  112  while rotating, a force F slitting  is applied to the two blades  102 A and  102 B due to speed components of the two rotating blades  102 A and  102 B. The force F slitting  may be decomposed into a force F slitting *sin θ, which works in the direction that the tape  112  is cut, and F slitting *cos θ, which acts in a direction opposite to the F 1  direction.  
         [0045]     A force F 4 , which is the sum of F slitting *cos θ of both blades, acts in a direction that the tape  112  is not pushed even though the two blades  102 A and  102 B proceed toward the tape  112 , thereby offsetting the force F 3  illustrated in  FIG. 9 . Accordingly, the position of the tape  112  is stably fixed.  
         [0046]      FIG. 11  is a top view of the apparatus  100  for illustrating directions of forces generated when the tape  112  is cut by the two blades  102 A and  102 B. Referring to  FIG. 11 , when the blades  102  move in the F 1  direction to cut a portion  120  of the tape  112 , the force F 3  is applied to the tape  112  at the speed of the two blades  102 . The force F 3  causes the fixed position of the tape  112  to be unstable. Consequently, it is difficult to cut the tape  112  straight. Furthermore, the tape  112  may be pushed, creating a burr on its surface. The tape  112  may even break.  
         [0047]     Hence, to solve such problems, the force F 4  that works in the direction opposite to the force F 3  is required. Thus, the apparatus  100  can stably cut the tape  112  in a uniform size since the force F 3  is offset by the force F 4 . The forces F 3  and F 4  are originally generated by the blade-driving unit  114  of  FIG. 7  connected to the two blades  102 A and  102 B, as well as reaction forces resulting from the rotation of the blades.  
         [0048]      FIG. 12  is a perspective view of an embodiment of the blade-driving unit  114 . Referring to  FIG. 12 , the two blades rotate while being fixed into a driving axis. The driving axis rotates by being fixed into axes of two spurs  122  in the blade-driving unit  114 . In this case, the rotation speed of the blades  102 A and  102 B can be controlled by adjusting a gear ratio of a pinion  126  and the spurs  124 . The speed of a motor within the blade-driving unit may also be adjusted, of course.  
         [0049]     In addition, a rotational movement of a rack gear  128  is converted into a straight-line movement, thereby enabling the two blades  102 A and  102 B to move straight at constant speed. Therefore, the rotation speed (F 2  of  FIG. 6 ) and the straight-line speed (F 1  of  FIG. 6 ) of the two blades  102 A and  102 B can be controlled by adjusting the gear ratio of the spurs  124 , the pinion  126 , and the rack gear  128  included in the blade-driving unit  114 .  
         [0050]     The present invention described above has the following advantages. First, when tape is cut using a pair of rotating wheel-shaped blades, the entire edge of each blade cuts the tape to a uniform size. This is in contrast to cutting with just a portion of a fixed blade. Thus, the lifespan of the blades can be extended. Accordingly, the time required to replace blades can be reduced, thereby enhancing operating efficiency of the cutting apparatus. If it is assumed that a conventional blade can be used up to 2000 times, then the rotating blades, according to embodiments of the present invention, can be used up to approximately 3,000,000 times, which is about 1500 times longer than the conventional blade.  
         [0051]     Second, a method of cutting tape according to embodiments of the present invention solves the problems of the tape being pushed back and forth or not being cut straight. Thus, the yield and quality of a resulting semiconductor package can be enhanced. When conventional blades are compared with the blades of the present invention in terms of straightness of a cut lane, a slit cut by conventional blades is, perhaps, 65 μm in width, while a slit cut by the blades of an embodiment of the present invention is, perhaps, 20 μm in width. Thus, the blades of embodiments of the present invention secure stable straightness by more than about three times compared with the convention blade.  
         [0052]     Third, it may take the conventional blade perhaps 1.9 seconds to cut tape once while it may take the two wheel-shaped blades of an embodiment of the present invention perhaps 0.8 seconds. Since the two blades according to an embodiment of the present invention cut the tape in both directions while shuttling in a straight line, the two blades may have productivity more than double the productivity of the conventional blade.  
         [0053]     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.