Patent Publication Number: US-2006011509-A1

Title: Packaging system and method for storing electronic components

Description:
FIELD OF THE INVENTION  
      The present invention relates to a carrier tape and cover tape used for packaging and transporting components. More particularly, the present invention is directed to a cover tape that protects components placed in the cavities of the carrier tape. A protective layer is attached on top of the cover tape to protect the components within the cavities of the carrier tape during transport or “drop testing.” 
     BACKGROUND OF THE INVENTION  
      In the electronic circuit assembly field, electronic components such as semiconductor chips, devices, integrated circuits, and the like are generally packaged and transported in carrier tapes from one manufacturer to another manufacturer or customer. It is often critical that the components be packaged and transported with minimal damage. By their very nature, these electronic components are lightweight objects and susceptible to damage. Accordingly, it is important to minimize damage from occurring by appropriately packaging and transporting these components. After manufacturing the electronic components in a “clean room” facility, the components are generally packaged and transported to a customer such as a computer wholesaler for mounting onto printed circuit boards.  
      A conventional carrier tape includes multiple thermoformed pockets or cavities formed along its longitudinal direction for storing and transporting the components. The carrier tape also includes a row of sprockets formed longitudinally along one side of the carrier tape for locating and feeding the components to the automated pick and place machine.  
      During the packaging process, the components are loaded into the cavities of the carrier tape by the automated pick and place machine. After the components are successfully loaded into the cavities, a cover tape is applied over the cavities by applying pressure or heat along the bonding zones. The cover tape prevents the components from exiting the cavities of the carrier tape. After sealing the cavities of the carrier tape with the cover tape, the components are transported to the manufacturer or to the customer.  
      The components are placed in the cavities of the carrier tape before the components are secured with the cover tape. The loaded carrier tape is then wound into a roll or a reel (“reel” hereinafter). The carrier tape and cover tape are made of materials sufficiently flexible to be wound onto a reel, which materials are described in more detail later herein. After the carrier tape is wound on the reel, the reel can be placed within a static control bag before it is placed in its individual box. Thereafter, one or more individual boxes can be placed in a shipping box for storage and transport to another manufacture or customer.  
      After receiving the shipping box, the reel is unpacked from its individual box and the static control bag. The carrier tape is then unwound from the reel and is positioned on the automated pick and place machine. As the carrier tape advances in a longitudinal direction using sprockets, the automated pick and place machine simultaneously removes the cover tape and picks up the components from the cavities and places them in desired locations (e.g., mounts them to printed circuit boards).  
      The electronic circuit industry conducts a “drop test” on the final packaging system. As described above, the final packaging system includes the reel, carrier tape, cover tape, and components. Again, the packaging system can also include the static control or vacuum-sealed bag, individual and/or shipping boxes for receiving the reel. During drop testing when the packaging system is dropped intentionally, it is reported that a great number of components sustain damage using current packaging technology. Most likely, the leads bend from the rapid deceleration of the components against the vertical sidewalls of the cavities after the components “jump.” Specifically, the components “jump” within the cavities, and the leads collide with the vertical sidewalls, thereby causing the leads to bend. Damage can also result within the components as a result of such collision. It can be appreciated that the conventional carrier tape system does not sufficiently protect the components from damage during drop testing or transport. Achieving minimal component damage is often very difficult and continues to be a major problem in the carrier tape industry.  
      Undulations may also result in the carrier tape as the components are transported from one facility to another. Such undulations may undesirably change the placement of the components in the cavities of the carrier tape, thereby leading to obstructions in using the automated pick and place machine.  
      Accordingly, there remains a need for a packaging system and method designed to protect the electronic components from damage, and particularly, protecting the leads from bending or crushing. There is also a need for a packaging system and method for preventing undulations of the components in the cavities of the carrier tape during transport.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide a packaging system and method for protecting electronic components from damage during transport or “drop testing.” 
      It is another object of the present invention to provide a cover tape that protects electronic components placed in the cavities of a carrier tape.  
      It is a further object of the present invention to provide a cover tape having a protective layer attached thereto for protecting electronic components in the cavities of the carrier tape.  
      It is yet another object of the present invention to provide a packaging system and method designed to protect the electrical terminals on electronic components from damage.  
      It is another object of the present invention to provide a packaging system and method for preventing undulations of the electronic components in the cavities of the carrier tape during transport.  
      The present invention relates to a packaging system and method for protecting electronic components from damage during transport or “drop testing.” The packaging system of the present invention includes a novel cover tape bonded to a carrier tape. A protective layer is attached to the top surface of the cover tape for protecting electronic components stored in the cavities of the carrier tape. The protective layer protects the components from excessive physical impact during transport or during testing. In particular, the protective layer protects the package, the die, as well as the electrical terminals of the electronic components from damage. The protective layer  100  is fabricated from an elastomeric material that has electrostatic dissipating properties. In addition, the protective layer is preferably made of a material that is flexible and not susceptible to generating residue. It is, however, not essential for the protective layer to have electrostatic dissipating properties since the protective layer does not directly contact the components in the packaging system.  
      The method for protecting the components in the cavities of the carrier tape includes placing each of a plurality of components in a respective plurality of longitudinally spaced cavities of a carrier tape; attaching a compressible protective layer to the top of the cover tape before sealing the cover tape on the carrier tape. The protective layer can be attached to the cover tape using adhesives. Furthermore, the cover tape is attached to the carrier tape on at least a pair of bonding zones on opposite sides of the cavities.  
      In another embodiment, the protective layer can be attached to the cover tape as the cover tape is being bonded to the carrier tape. Since the protective layer is separated from the components by the cover tape, the protective layer can also be selected from insulative materials.  
      The present invention also encompasses the method of providing a protective layer on a surface of the cover tape that faces away from the cavity, placing each of a plurality of components into a respective plurality of cavities and then wounding the protective layer, cover tape and carrier tape onto a tape receiving device.  
      In yet another embodiment, a film layer can be placed above the protective layer to shield the exposed surface of the film layer from contaminants. In this manner, the protective layer is sandwiched between the film layer on top and the cover tape below. In all of the above embodiments, the protective layer protects the components from damage. In addition, the protective layer also prevents undulations from occurring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and other objects and advantages of the present invention will become apparent and more readily appreciated from the following detailed description of the presently preferred exemplary embodiments of the invention taken in conjunction with the accompanying drawings, of which:  
       FIG. 1A  illustrates a top view of a cover tape in accordance with the preferred embodiment of the present invention;  
       FIG. 1B  illustrates a cross-sectional view of the cover tape of  FIG. 1A  in accordance with the preferred embodiment of the present invention;  
       FIG. 1C  illustrates a cross-sectional view of another embodiment of the packaging system in accordance with the present invention;  
       FIG. 2A  illustrates a perspective view of a carrier tape and cover tape in accordance with the preferred embodiment of the present invention;  
       FIG. 2B  illustrates a cross-sectional view taken along line II—II of the carrier tape and cover tape of  FIG. 2A ; and  
       FIG. 2C  illustrates a cross-sectional view of another embodiment for providing a protective layer above the carrier tape of  FIG. 2A . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The present invention will be described in greater detail, which may serve to further the understanding of the preferred embodiments of the present invention. As described elsewhere herein, various refinements and substitutions of the various embodiments are possible based on the principles and teachings herein.  
      The preferred embodiments of the present invention will now be described with reference to  FIGS. 1-2 , wherein similar elements are labeled with similar reference numerals. The specific details and parameters that are provided herein are intended to be explanatory and should not be construed in a limiting fashion.  
       FIGS. 1A-1B  illustrate a cover tape in accordance with the preferred embodiment of the present invention.  FIG. 1A  illustrates a top view, and  FIG. 1B  illustrates a side view of the cover tape  110  in accordance with the preferred embodiment. Reference will be made to  FIGS. 1A-1B  concurrently for a more complete understanding of the present invention.  
      The present invention discloses a packaging system and method for protecting electronic components from damage during transport or “drop testing.” The electronic component may include any type of electronic device that is not required to be stored in a dry pack. For example, the present invention would be appropriate for protecting components such as Ball Grid Arrays (BGA), Flip Chips, Chip Scale Packages (CSP), Quad Flat Packs (QFP), Small Outline Integrated Circuits (SOIC), Thin Shrink Small Outline Packages (TSSOP), Plastic Leaded Chip Carriers (PLCC) and leaded surface mount packages in general. The packaging system of the invention is also suitable for protecting capacitors, resistors, gate arrays and any other delicate devices that contain fragile features.  
      A perspective view of the packaging system is shown in  FIG. 1A  that includes a novel cover tape  110  bonded to a carrier tape  200 .  FIG. 1B  illustrates a detailed view of the cover tape  100  having a first surface  130  facing away from the cavity. The packaging system includes protective layer  100  attached to the first surface  130  of the cover tape  110 . The protective layer  100  shields the electronic components from excessive physical impact within the cavities, thereby protecting package leads, solder balls, and other portions of the components from damage. The method for protecting the components in the cavities  24  of the carrier tape  200  includes attaching the protective layer on the first surface of the cover tape before sealing the cover tape on the carrier tape. When the cover tape  110  is bonded to the carrier tape  200  with the components placed in the cavities, the protective layer prevents excessive movement of the components therein.  
      The cover tape  110  is preferably made from a heat-activated anti-static material that meets EIA industry standards, such as a VH-E1 cover tape. In an another preferred embodiment, the cover tape is made from a pressure sensitive adhesive (PSA) material. The width of the cover tape  110  should be sufficiently wide enough to cover the cavities of the carrier tape while bonding to the periphery of the carrier tape. However, the cover tape should not block the sprockets on the periphery of the carrier tape. In the current state of carrier tape technology, the width of the cover tape  110  is preferably about 37.5 or 49.5 mm (±0.2 mm), depending on the type and dimensions of the carrier tape.  
      Nevertheless, the present invention is not limited to carrier tapes having widths of either 37.5 mm or 49.5 mm. The thickness of the cover tape  110  should be about 0.04-0.06 mm, but other thickness values outside this range can be used so long as the cover tape  110  is sufficiently robust to be heated-bonded to the carrier tape while protecting the components in the cavities. The cover tape  110  and the film layer can be made from, but not limited to, polyester, polypropylene or polyethylene having heat sensitive adhesives with or without additives. An example of a suitable material for both cover tape  110  and film layer  120  that can be used in the present invention is the ST10 cover tape manufactured by Neptco Inc. of Pawtucket, R.I. The ST10 cover tape is a clear polyester film coated with heat-activated adhesive with anti-static properties. A suitable PSA material for both cover tape  110  and film layer  120  is W-4401ASP manufactured by Lintec Corporation of Tokyo, Japan.  
      Attached to a first surface  130  of the cover tape  110  is a protective layer  100 , which layer  100  protects the components during transport or “drop testing.” In one configuration, the protective layer  100  is attached to the center portion of the cover tape  110  in its longitudinal direction as shown in  FIG. 1B . In this configuration the protective layer is approximately one half the width of the cover tape. This configuration permits information on the components that is not covered by the protective layer to be visible through a clear cover tape. For a cover tape  110  that is 37.5 mm (±0.2 mm) or 49.5 mm (±0.2 mm) wide, the width of the protective layer  100  can be about 18.00 mm, and the thickness about 1.00 mm. However, those skilled in the art will recognize that other width and thickness values than those stated above can be used in the present invention so long the components are adequately protected during transport or “drop testing.” Also, in other embodiments, one or more protective layers can be attached to other portions of the cover tape besides the center portion.  
      The protective layer  100  is preferably made from a material that is flexible, static resistant, and not susceptible to generating residue. An example of the protective layer  100  that can be used in the present invention is a foam manufactured by LIT Industries that is made from a material such as polyether, polyester, PVC, neoprene, and sponge.  
      Further, a clear or transparent protective layer  100  can be used so that visual inspection of the leads  20 , or other terminals, can be performed. Gel is another suitable material for the protective layer. An example of a gel material that is suitable for the present invention is Gel-Film™ available from Gel-Pak LLC, of Hayward Calif.  
      The protective layer  100  can be attached to a first surface  130  of the cover tape  110  using adhesives before the cover tape  110  is bonded to the carrier tape. In another embodiment, the protective layer  100  can be attached to the cover tape  110  as the cover tape  110  is being bonded to the carrier tape. Those skilled in the art will recognize that various methods for attaching the protective layer  100  to a first surface  130  of the cover tape  110  can be implemented in the present invention. Further, after the protective layer  100  is attached to the cover tape  110 , the two layers ( 100  and  110 ) are successively wound together on a tape receiving device such as a reel. The pressure applied to the successively wound up layers compresses the protective layer  100  and the cover tape  110  against the components to shield the components from excessive physical impact. In addition,  FIG. 1C  illustrates yet another embodiment for applying a protective layer to a flexible carrier tape. In this embodiment a film layer  120  may be attached to the exposed side  115  of protective layer  100  of  FIG. 1B .  
       FIGS. 2A-2C  illustrate a carrier tape and cover tape in accordance with the preferred embodiment of the present invention.  FIG. 2A  illustrates a perspective top view,  FIG. 2B  illustrates a cross sectional view taken along line II—II, and  FIG. 2C  illustrates an exploded top view of a section of the carrier tape and cover tape of  FIG. 2A .  
      As discussed in the background section, the carrier tape  200  includes multiple thermoformed cavities  24  for storing and transporting the components  35 . Although each cavity  24  generally stores and transports one such component  35 , in other embodiments, each cavity  24  can store and transport two or more components  35 . Along the longitudinal direction of the carrier tape  200  are sprockets  28 . Again, as described above, these sprockets  28  are used by an automated pick and place machine in order to place and pick up the components  35  from/into the cavities  24 . The carrier tape  200  is generally made from, but not limited to, thermoplastic resin, polycarbonate, polystyrene or ABS (acrylonitrile butadiene-styrene) with or without additives. Currently, the widths of the carrier tapes  200  in the industry range from 8 to 56 mm.  
      After the components are successfully loaded into the cavities, a cover tape is applied over the cavities by applying pressure or heat along the bonding zones. The cover tape has a heat or pressure sensitive adhesive on bonding zones  12  which adheres to the carrier tape, and holds electronic component  35  securely in cavity  24 .  
      As illustrated in  FIG. 2B , the protective layer  100  is attached to the top of the cover tape  110 . The protective layer  100  does not directly contact the components. However, protective layer  100  conforms to the shape of the upper portion of the component  35  when the carrier tape  200  and protective layer  100  are wound onto a tape receiving device such as a reel. Further, each consecutive winding of layers onto a reel provides a packaging system that imparts additional protection to the components due to the protective layers interleaving with the carrier tape  200  on a reel. The packaging system also serves to maintain the integrity of the carrier tape. In summary, the present invention prevents the cavities from being crushed, minimizes undulations, and protects the components from being damaged.  
      The protective layer  100  should be lightweight and flexible enough to be wound on a reel. In a preferred embodiment, the protective layer  100  is made from a material that has electrostatic dissipating properties. However, since the protective layer is isolated from the components by cover tape  110 , it is not essential that protective layer  100  be made from electrostatic dissipating material. The protective layer  100  should not produce any residue or particulate since they can attach to the electrical terminals  20  of the component  35  and cause defects. Nevertheless, since protective layer  100  does not directly contact components  35 , the protective layer can be composed of a residue-generating material. Cover tape  110  with the attached protective layer  100  and film layer  120  should be capable of being peeled back from the carrier tape  200  with a uniform amount of force per industry standards. In other words, while separating the cover tape  110  from the carrier tape  200 , the force required for such separation should be constant with respect to the longitudinal direction of the carrier tape  200 .  
      It is to be understood that in the foregoing discussion and appended claims, the term “components” include any electronic or non-electronic components such as integrated circuits, memory chips, or semiconductor devices, etc.  
      In the previous descriptions, numerous specific details are set forth to provide a thorough understanding of the present invention. However, as one having ordinary skill in the art would recognize, the present invention can be practiced without resorting to the details specifically set forth.  
      Although various preferred embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications of the exemplary embodiments are possible without materially departing from the novel teachings and advantages of this invention.