Patent Publication Number: US-6701910-B1

Title: Film frame substrate fixture

Description:
This application is a divisional of application Ser. No. 09/293,151, filed on Apr. 16, 1999, now U.S. Pat. No. 6,321,739 which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to material handling machines for dicing semiconductor substrates. More particularly, the invention relates to film frames for holding substrates for dicing and, still more particularly, to fixtures coupled to the film frame for receiving and retaining the substrate in position on the film frame. 
     2. Description of the Related Art 
     Conventional substrate dicing machines include a film frame coupled to a chuck by vacuum. The film frame includes a frame and mounting tape stretched across the frame. Typically, die mounting tape is a polymer film having an adhesive surface for holding a substrate to be diced. 
     In conventional operation, a substrate is mounted on the mounting tape and the film frame is mounted on the chuck. Vacuum is applied to the bottom of the mounting tape. The vacuum stabilizes the mounting tape in the vertical direction. When the substrate has been diced, the film frame and substrate must be processed to remove the individual dies from the mounting tape. Unfortunately, dedicated equipment is required to remove the tape from the film frame. Moreover, the dedicated equipment is expensive and takes up valuable floor space. In addition, the tape removing process adds manufacturing steps, and the mounting tape is consumed during the dicing process, adding to the cost of producing products which incorporate the diced dies. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the above-cited disadvantages by providing a fixture that is mounted to the film frame by mounting tape. The fixture includes a recess configured to receive a substrate for dicing. A plurality of grooves for receiving a cutting saw extend longitudinally and transversely across the fixture to define die regions. As the cutting saw moves over the substrate and along the grooves, the substrate is diced into individual dies. The film frame, fixture and tape are reusable with other substrates 
     The fixture may also include a plurality of apertures that align with one or more apertures formed in the mounting tape. The aligned apertures supply vacuum to the substrate from a vacuum source which retains the substrate in the fixture and which also retains the dies in place in the fixture after dicing. When the dicing is completed, the vacuum is turned off and the individual dies can be readily removed from the fixture. 
     The invention advantageously reduces the number of manufacturing steps involved in the production of the dies. Moreover, since the cutting saw moves along the grooves, the fixture is not destroyed in the dicing process and can be reused, and since the fixture allows the saw to dice the substrate without destroying the mounting tape, the mounting tape is not consumed in the process, thereby further reducing material costs. 
    
    
     These and other features and advantages of the invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention which is provided in connection with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic of a dicing machine coupled to a vacuum source and a controller. 
     FIG. 2 is a plan view of a film frame. 
     FIG. 3 is a side view of a substrate to be diced. 
     FIG. 4 is a top plan view of the substrate of FIG.  3 . 
     FIG. 5 is a bottom plan view of the substrate of FIG. 3 
     FIG. 6 is a top plan view of a fixture for receiving the substrate of FIG. 3 in a contact down orientation. 
     FIG. 7 is a bottom plan view of the fixture of FIG.  6 . 
     FIG. 8 is a side view of the fixture of FIG.  6 . 
     FIG. 9 is an end view of the fixture of FIG.  6 . 
     FIG. 10 is a section view taken along line  10 — 10  of FIG.  6 . 
     FIG. 11 is a top plan view of a fixture for receiving the substrate of FIG. 3 in a contact up orientation. 
     FIG. 12 is a bottom plan view of the fixture of FIG.  11 . 
     FIG. 13 is a side view of the fixture of FIG.  11 . 
     FIG. 14 is an end view of the fixture of FIG.  11 . 
     FIG. 15 is a section view taken along line  15 — 15  of FIG.  11 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     A conventional film frame  10  for use in dicing a substrate is illustrated in FIG.  2 . The frame  10  includes a generally annular plate  12  having a pair of flats  14  on opposite sides of the plate  12  and a pair of positioning notches  16  for receiving guide pins (not shown). In operation, a film having an adhesive surface for supporting a substrate is stretched across the frame  10 . The frame  10  is mounted on the dicing machine  15  and mechanical clamps retain the frame  10  in position. 
     Although the subsequent description shows a particular type of substrate, e.g., an encapsulated substrate that includes a plurality of chip packages having ball grid array connectors, the substrate shown is merely exemplary. The invention can be used with a wide variety of substrates, including semiconductor wafers, or portions thereof. 
     A substrate  20  to be diced is illustrated in FIGS. 3-5. The illustrated substrate  20  is a forty unit overmolded panel and includes a panel  22  divided into four overmolded segments  24 . Each segment  24  will produce ten individual encapsulated packages  26  when diced. Each of the packages has a plurality of contacts in the form of solder balls  28  formed as a ball grid array (BGA) or fine pitch ball grid array (FBGA)  30  on the bottom of the panel  22 , i.e., beneath each package  26 . The panel  22  further includes apertures  32  disposed between adjacent segments  24  and apertures  34  disposed along the longitudinal edges of the panel  22 . A plurality of cutting saw alignment marks  36  extend longitudinally and transversely across the panel  22 . The substrate  20  has three square corners  21   a  and a beveled corner  21   b  for orientation of the substrate  20  in a fixture  40  described below. 
     FIGS. 6-10 illustrate a first embodiment of a fixture  40  for receiving the substrate  20  in a “contacts down” configuration. The fixture  40  includes a plate  42  having a two-stage central recessed area  44  (FIG.  10 ), a plurality of longitudinal grooves  46  (FIGS.  6  and  9 ), and a plurality of transverse grooves  48  (FIGS.  6  and  10 ). The recessed area  44  is sized and configured to receive the substrate  20  and includes a shallow panel-receiving region  44   a  and a deeper contact-receiving region  44   b . The grooves  46 ,  48  cooperate to define a plurality of die regions  50  that are disposed to align with the packages  26  on the substrate  20 . The grooves  46 ,  48  are sized to receive the blade of a cutting saw  17  and extend below the level of the contact-receiving region  44   b , so that the cutting saw  17  cuts completely through a panel  22  disposed in the recessed area  44  without contacting any part of fixture  40 . A controller  21  (FIG. 1) controls the positioning of the cutting saw  17  in the grooves  46 ,  48  and the movement of the saw  17  to cut the substrate  20 . 
     Each die region  50  includes a plurality of apertures  52  formed as an aperture array  54 . The aperture array  54  matches the BGA  30  beneath each package  26  so that each ball  28  in tie BGA  30  fits into one of the apertures  52  of the aperture array  54 . An additional plurality of apertures  56  are formed in each die region  50  for supplying vacuum from a vacuum source  19  to retain each package  26  in the fixture  40  during and after dicing. 
     The grooves  46 ,  48  further define a plurality of non-die regions  60  disposed along the periphery of the panel  22  and between the segments  24 . The non-die regions  60  include apertures  64  for supplying vacuum to retain the non-die regions of the substrate  20  in the fixture during and after dicing. 
     The recessed area  44   a  includes three circular corners  68  for receiving square corners  21   a  on the substrate  20 . The fourth corner  70  is rounded for receiving a shaped corner  21   b  on the substrate  20 . The corners  68 ,  70  cooperate to ensure that the substrate  20  is property oriented in the fixture  40 . 
     FIGS. 11-15 illustrate a second embodiment of the fixture  140  for use in dicing the substrate  20 . The fixture  140  includes a plate  142  having a one-stage central recessed area  144 , a plurality of longitudinal grooves  146 , and a plurality of transverse grooves  148 . The recessed area  144  is sized and configured to receive the substrate  20  in a “contact up” configuration, wherein the encapsulant is disposed in the recessed area  144 . The grooves  146 ,  148  cooperate to define a plurality of die regions  150  that are disposed to align with the packages  26  on the substrate. The grooves  146 ,  148  are sized to receive a cutting saw  17  and extend below the level of the recessed area  144 , so that the cutting saw cuts completely through a panel  22  disposed in the recessed area  144  without contacting the fixture  140 . 
     Each die region  150  includes a pair of apertures  153  for supplying vacuum to retain each package  26  in the fixture during and after dicing. The grooves  146 ,  148  further define a plurality of non-die regions  160  disposed along the periphery of the panel  22  and between the segments  24 . The non-die regions  160  include apertures  164  and  165  for supplying vacuum to retain the non-die regions of the substrate  20  in fixture  140  during and after dicing. 
     The recessed area  144   a  includes three circular corners  168  for receiving square corners  21   a  on the substrate  20 . The fourth corner  170  is rounded for receiving a shaped corner  21   b  on the substrate. The corners  168 ,  170  cooperate to ensure that the substrate  20  is properly oriented in the fixture  40 . 
     The use of the FIGS. 4-15 fixtures will now be described. One of the fixtures (FIGS. 6-10) is used for a contacts shown down dicing, while the other fixture (FIGS. 11-15) is used for contact up dicing. 
     In use, mounting tape is stretched across the film frame  10  and the fixture  40  or  140  is mounted on the mounting tape. The tape is cut out beneath fixture  40  or  140  to allow apertures  56 ,  64 ,  153 ,  164 , and  165  to receive a vacuum from the source  19  (FIG. 1) through the cut-out position of the tape (FIGS.  6 - 10 ). The film frame  10  is mounted on a chuck and a substrate  20  is positioned in the recess  44  or  144 . Vacuum is then applied to the substrate  20  through the cutout in the tape and through the apertures in fixture  40  or  140  to retain the substrate  20  on the fixture  40  or  140 . The cutting saw is then moved through the grooves  46 ,  48  or  146 ,  148  to dice the substrate  20 . After the substrate has been diced, the vacuum is turned off and the film frame  10  is removed from the chuck and the individual dies easily removed from the fixture  40  or  140  for further processing. The film frame is returned to the chuck, another substrate  20  mounted on the fixture  40  or  140  and vacuum reapplied to retain a new substrate  20  for dicing It will be appreciated that the substrate can be mounted on the fixture before the fixture is mounted on the film. Moreover, the fixture can be mounted on the mounting tape before the film frame is mounted on the chuck. In other words, the precise sequence of steps is not essential. 
     The present invention provides a fixture for mounting a substrate to a film frame so as to retain the substrate for dicing without destroying the mounting tape during the dicing process. The fixture also reduces the number of manufacturing steps involved and eliminates the need for dedicated and expensive equipment. In particular, the invention has been described with respect to use with encapsulated substrates employing ball grid array contact packages which are to be diced from the substrate. However, as noted, any substrate can be diced using the fixture of the invention. For example, the invention can be used with differently shaped substrates or to dice semiconductor wafers of different sizes or shapes. Therefore, the scope of the present invention is not to be considered as limited by the specifics of the particular fixtures described above, but is only limited by the scope of the appended claims.