Patent Publication Number: US-2005126696-A1

Title: Snap cure device for semiconductor chip attachment

Description:
CROSS REFERENCE TO RELATED APPLICATION  
      This U.S. non-provisional application claims priority under 35 U.S.C § 119 from Korean Patent Application No. 2003-90096 which was filed on Dec. 11, 2003, the entire contents of which are incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an apparatus and a method for attaching semiconductor chips to substrates and, more particularly, to an apparatus and a method for operating the apparatus for performing a snap cure process during the attachment of a semiconductor chip to a substrate.  
      2. Description of the Related Art  
      The chip attaching process of a semiconductor package manufacturing process typically separates semiconductor chips from a wafer and then attaches the semiconductor chips to a substrate using an adhesive. The adhesive may include an adhesive tape and/or a liquid adhesive and typically requires a curing after the semiconductor chip process has been attached. The curing processes may include an oven cure and/or a snap cure depending on the characteristics and performance of the adhesive(s) used in the semiconductor chip attachment.  
      A snap cure device used in the snap cure process may be arranged inline with the semiconductor chip attaching apparatus, examples of which are disclosed in Japanese Publication Nos. 05-226390 and 07-106348. The conventional snap cure device may occupy a considerable space due to the horizontal arrangement of the plurality of curing zones.  
      In order to reduce the space required, Japanese Publication No. 10-163234 discloses a curing device in which a plurality of curing zones are arranged perpendicularly to the direction of transfer of the substrate. However, this curing device may also utilize a horizontal arrangement of the curing zones and therefore limit the degree of reduction that can be achieved in the area occupied by the snap cure device.  
     SUMMARY OF THE INVENTION  
      An exemplary snap cure device is provided in which at least one curing zone is arranged vertically. The snap cure device comprises a substrate conveyor for conveying substrates with a plurality of heater blocks installed above the substrate conveyor and arranged vertically at predetermined intervals. A transfer means may be utilized to transfer the substrates between the substrate conveyor and the heater blocks.  
      In accordance with an exemplary embodiment of the apparatus, eight heater blocks are arranged in a Z-axis direction and associated with a transfer means that includes a first fork and a second fork. The first fork transfers the substrates from the substrate conveyor to the heater blocks while the second fork transfers the substrates from the heater block to the substrate conveyor.  
      In accordance with another exemplary embodiment, the heater blocks may be arranged in two adjacent rows that are aligned in an X-axis direction. In the particular arrangement illustrated, the heater blocks include a first heater block row and a second heater block row with the first heater block row located above the substrate conveyor and the second heater block row also located above the substrate conveyor and adjacent the first heater block row in the direction of travel of the substrate conveyor. The first and second heater block rows each have four heater blocks and are associated with a transfer means that comprises a first fork, a second fork and a third fork. The first fork transfers the substrates from the substrate conveyor to the heater blocks in the first heater block row, the second fork transfers the substrates from the uppermost heater block in the first heater block row to the corresponding uppermost heater block in the second heater block row. The third fork is then used to transfer the substrates through the second heater block row and from the second heater block row to the substrate conveyor.  
      In accordance with yet another exemplary embodiment, the heater blocks may be arranged in two rows generally aligned along the Y-axis. The heater blocks include a first heater block row and a second heater block row with the first heater block row located above the substrate conveyor, and the second heater block row spaced apart from the substrate conveyor in the Y-axis direction and substantially parallel to the first heater block row. A dummy substrate conveyor may be installed below the second heater block row and substantially parallel to the substrate conveyor. The first and second heater block rows can each have four heater blocks that are associated with a transfer means that comprises a first fork, a second fork, a third fork and a fourth fork. The first fork transfers the substrates from the substrate conveyor to the heater blocks of the first heater block row and the second fork transfers the substrates from the uppermost heater block of the first heater block row to the corresponding uppermost heater block of the second heater block row. The third fork transfers the substrates from the second heater block row to the dummy substrate conveyor while the fourth fork transfers the substrates from the dummy substrate conveyor to the substrate conveyor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Exemplary embodiments of the present invention will be described with reference to the accompanying drawings in which identical reference numerals designate similar or corresponding structural elements, and, in which:  
       FIG. 1  is a schematic block diagram illustrating a snap cure device in accordance with an exemplary embodiment of the present invention;  
       FIG. 2  is a plane view of  FIG. 1 ;  
       FIG. 3  is a cross-sectional view taken along a line of  3 - 3  of  FIG. 2 ;  
       FIG. 4  is a view illustrating the step of transferring substrates in accordance with an exemplary embodiment of the present invention;  
       FIG. 5  is a plane view illustrating a snap cure device in accordance with another exemplary embodiment of the present invention;  
       FIG. 6  is a view illustrating the step of transferring the substrates of the snap cure device of  FIG. 5 ;  
       FIG. 7  is a plane view illustrating a snap cure device in accordance with yet another exemplary embodiment of the present invention; and  
       FIG. 8  is a view illustrating the step of transferring the substrates of the snap cure device of  FIG. 7 . 
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS  
      Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. It will be understood that the depicted elements may be enlarged, reduced, simplified and/or merely exemplary, and may not necessarily be drawn to scale.  
       FIG. 1  is a schematic block diagram of a semiconductor chip attaching apparatus  20  in accordance with an exemplary embodiment of the present invention, in which a snap cure device  10  is installed above a substrate conveyor  21 .  FIG. 4  illustrates the step of transferring substrates  32  in the snap cure device  10  of  FIG. 2 . For the purposes of the following discussion the longitudinal axis and the conveying direction of the substrate conveyor  21  will be referred to as the X-axis with the Y-axis being perpendicular to the X-axis and generally parallel to the main surface of the substrate conveyor and the Z-axis being perpendicular to both the X-axis and the Y-axis.  
      As illustrated in  FIGS. 1-4 , the semiconductor chip attaching apparatus  20  comprises a chip attaching unit  24  and a snap cure device  10 . The chip attaching unit  24  applies an adhesive  34  to a substrate  32  and attaches a semiconductor chip  35  to the substrate  32 . The snap cure device  10  then performs a snap cure process on the substrates  32  having the semiconductor chip  35 . In this embodiment, the snap cure device  10  is installed above the substrate conveyor  21 . Alternatively, the snap cure device  10  may be installed inline with a conventional semiconductor chip attaching apparatus.  
      As illustrated the semiconductor chip attaching apparatus  20  typically includes a substrate loading cassette  22  located at one end of the substrate conveyor  21  and a substrate receiving cassette  23  located at the other end of the substrate conveyor  21 . The substrate loading cassette  22  loads the substrates  32  before a chip attaching process. The substrate receiving cassette  23  receives the substrates  32  on which the semiconductor chips  35  have been mounted after the snap cure process. The substrate  32  may be a lead frame strip, a printed circuit board, a tape wiring substrate or other structure designed and configured to receive and mount one or more semiconductor chips. In case of a lead frame strip, the substrate loading cassette  22  may be a magazine from which the substrates  32  are placed one at a time on to the substrate conveyor  21  by a loader  25 .  
      The substrate  32  includes at least one chip attaching area  33  to which the semiconductor chip  35  may be attached. The substrate conveyor  21  may convey the substrates  32  at a predetermined interval or rate during the chip attaching and snap cure processes sufficient to support a consecutive and substantially continuous operation. The substrate conveyor  21  may employ a conventional member transfer system such as a transfer rail. The substrate conveyor  21  is installed longitudinally below the substrate  32 . After the snap cure process has been completed, the substrates  32  may be transferred from the substrate conveyor  21  to the substrate receiving cassette  23  by an unloader  26 .  
      The chip attaching unit  24  comprises an adhesive supplier  27 , a wafer cassette  28 , a wafer table  29  and a chip attaching device  31 . The adhesive supplier  27  supplies the adhesive  34  to the substrate  32 . The wafer table  29  supports and typically orients the wafers from which the semiconductor chips  35  will be separated. The chip attaching device  31  is installed between the wafer table  29  and the substrate conveyor  21  and separates the semiconductor chip  35  from the wafer and attaches the semiconductor chip  35  to the adhesive  34  applied on the substrate  32 . The wafer is transferred from the wafer cassette  28  to the wafer table  29 .  
      The adhesive supplier  27  supplies the adhesive  34  to the chip attaching area  33  of the substrate  32  as the substrates are conveyed past the chip attaching unit  24 . The adhesive  34  may be a double-sided adhesive tape or a liquid adhesive. The double-sided adhesive tape may be a polyimide tape while the liquid adhesive may be a conductive liquid adhesive such as Ag-epoxy, Ag-glass or solder, or may be a non-conductive liquid adhesive such as silicone.  
      The chip attaching device  31  attaches the semiconductor chip  35  to the chip attaching area  33  of the substrate  32 . The semiconductor chip  35  is typically provided from a wafer including a plurality of individual semiconductor chips  35  provided on the wafer table  29 . The chip attaching device  31  is located between the wafer table  29  and the substrate conveyor  21  and reciprocates therebetween. The chip attaching device  31  absorbs the semiconductor chip  35 , typically by vacuum, in order to separate it from the wafer and then places and presses the semiconductor chip  35  onto the substrate  32 . The attachment of the semiconductor chip  35  typically includes application of both heat and pressure.  
      The snap cure device  10  is installed near the substrate conveyor  21  adjacent the chip attaching unit  24 . The snap cure device  10  cures the adhesive  34  using a plurality of heater blocks  13  arranged in the direction of the Z-axis. The snap cure device  10  performs a snap cure process gradually on the substrate  32  by moving the substrates  32  progressively through each of the heater blocks  13  in the direction of the Z-axis.  
      The snap cure device  10  comprises the heater blocks  13  and a transfer means  11 . The heater blocks  13  are each spaced at predetermined intervals. The transfer means  11  transfers the substrate  32  between the substrate conveyor  21  and the heater blocks  13 .  
      The first exemplary embodiment is illustrated with eight heater blocks  13  installed above the substrate conveyor  21  in the direction of the Z-axis as shown in  FIGS. 2 through 4 . The transfer means  11  comprises a first fork  15  and a second fork  16 . Although illustrated and described herein as “forks,” those of ordinary skill will appreciate that a variety of transfer devices may be used including, for example, vacuum assisted devices, devices having one or more than two contact bars and devices including additional mechanisms for gripping or holding the substrate during transfer operations. The first fork  15  transfers the substrate  32  from the substrate conveyor  21  to the first or lowest heater block  13   a  through intermediate heater blocks  13 , and to the last or uppermost heater block  13   b.  The second fork  16  transfers the cured substrate  32  from the uppermost heater block  13   b  to the substrate conveyor  21 . As illustrated, the first and second forks  15  and  16  may be installed on opposite sides of the substrate conveyor  21 . Alternatively, the first and second forks  15  and  16  may be both installed on the same side of the substrate conveyor  21 .  
      The first fork  15  and the second fork  16  include transfer bars  11   a  for loading/unloading the substrates  32 . The transfer bars  11   a  of the first fork  15  are spaced at predetermined intervals corresponding to the spacing of the heater blocks  13 . The substrate conveyor  21  and the heater blocks  13  have grooves  36  and  37  respectively for inserting the transfer bars  11   a  below the substrates  32 . The first fork  15  is movable to transfer the substrates  32  from the substrate conveyor  21  to the first heater block  13  and successively through the intermediate heater blocks  13  in the direction of the Z-axis. The second fork  16  is movable to transfer the substrate  32  from the uppermost heater block  13   b  downward onto the substrate conveyor  21 . The number of transfer bars  11   a  provided on the first fork  15  may be the same as the number of heater blocks  13  or may be less than the number of heater blocks.  
      The snap cure process may be performed using a temperature range of 100° C. to 220° C. and may have a duration of between 1 and 5 minutes. The snap cure process proceeds by gradually increasing and decreasing the temperature of the heater blocks  13 . In this embodiment, the temperature of the heater blocks  13  may be set at 100° C., 150° C., 180° C., 220° C., 220° C., 180° C., 150° C., 100° C. from lowest to uppermost to provide a thermal cycle including ramp-up, cure and ramp down periods. As will be appreciated by those of ordinary skill in the art, the number and relative temperatures of the heater blocks may be adapted as necessary for the particular devices, substrates and adhesives being utilized. The substrates  32  remain on each of the heater blocks  13  for the same period of time and may be moved or indexed simultaneously, thus avoiding mechanical interference that may otherwise occur when transferring the substrates  32 .  
      In accordance with the first exemplary embodiment, the snap cure device  10  includes heater blocks  13  installed in the direction of the Z-axis, thereby reducing the horizontal area occupied by the snap cure device  10  within the chip attaching apparatus ( 20  of  FIG. 1 ). The snap cure device  10  may be located above the substrate conveyor  21  near the substrate receiving cassette  23 . As will be appreciated, the snap cure device  10  may also be provided separately from the semiconductor chip attaching apparatus ( 20  of  FIG. 1 ) by, for example being incorporated in a separate downstream unit that can be installed inline with the output of the substrate conveyor  21  and may include a separate substrate conveyor (not shown) or to which attached, but uncured, substrates are transferred by another means.  
      In another exemplary embodiment, the snap cure device may include heater blocks arranged in a plurality of rows to reduce the vertical space requirements while still reducing the horizontal area required. Such arrangements typically will adopt an X-axis expansion and/or Y-axis expansion configurations.  
      The second exemplary embodiment illustrates an X-axis expansion type snap cure device  40 . Heater blocks  43  include a first heater block row  42  and a second heater block row  44 , as shown in  FIGS. 5 and 6 . The first heater block row  42  is located above a substrate conveyor  51 . The second heater block row  44  is located adjacent to the first heater block row  42  in the direction of travel of the substrate conveyor  51  (i.e., the X-axis direction).  
      A transfer means  41  includes a first fork  45 , a second fork  46  and a third fork  47 . The first fork  45  transfers the substrates  32  from the substrate conveyor  51  to the heater blocks of the first heater block row  42  in the direction of the Z-axis, i.e. from the first or lowest heater block  42   a  to the last or uppermost heater block  42   b.  The second fork  46  transfers the substrates  32  from the uppermost heater block  42   b  of the first heater block row  42  to the corresponding uppermost heater block  44   b  of the second heater block row  44 . The third fork  47  transfers the substrates  32  from the uppermost heater block  44   b,  through the intermediate heater blocks  441 , and to the lowest heater block  44   a  of the second heater block row  44  in the direction of the Z-axis and then to the substrate conveyor  51 .  
      Therefore, the substrates  32  from the substrate conveyor  51  are transferred upwardly through heater block row  42  in the direction of the Z-axis by the first fork  45 , in the direction of the X-axis by the second fork  46  and then downwardly through heater row  44  in the direction of the Z-axis by the third fork  47  and returned to the substrate conveyor  51 . The number of transfer bars provided on the first and third forks  45  and  47  will typically correspond to the number of heater blocks in the respective heater block rows  42  and  44 . Similarly, the first fork  45  and the second fork  46  will typically be installed on opposite sides of the substrate conveyor  21  with the third fork  47  installed adjacent to the first fork  45  and offset in the “downstream” or X-axis direction.  
      The second exemplary embodiment is similar to the first exemplary embodiment in that the snap cure process is performed gradually through eight heater blocks, except for the direction of transfer through the heater blocks. The heater blocks  43  may be set at the same temperatures as suggested for the first exemplary embodiment and the first and third forks  45  and  47  may each have four transfer bars.  
      The third exemplary embodiment illustrates a Y-axis expansion type snap cure device  70 . Heater blocks  73  may be arranged in a first heater block row  72  and a second heater block row  74  as illustrated in  FIGS. 7 and 8 . The first heater block row  72  is located above a substrate conveyor  81 . The second heater block row  74  is spaced or offset a predetermined distance from the substrate conveyor  81  along the Y-axis and substantially parallel to the first heater block row  72 . A dummy substrate conveyor  79  may be installed parallel to the substrate conveyor  81  and adjacent the second heater block row  74 .  
      A transfer means  71  includes a first fork  75 , a second fork  76 , a third fork  77  and a fourth fork  78 . The first fork  75  transfers the substrates  32  from the substrate conveyor  81  to the heater blocks of the first heater block row  72  in the direction of the Z-axis, i.e. from the first or lowest heater block  72   a  to the last or uppermost heater block  72   b.  The second fork  76  transfers the substrates  32  from the uppermost heater block  72   b  of the first heater block row  72  to the corresponding uppermost heater block  74   b  of the second heater block row  74 . The third fork  77  then transfers the substrates  32  from the uppermost heater block  74   b  to the lowest heater block  74   a  of the second heater block row  74  in the direction of the Z-axis and on to the dummy substrate conveyor  79 . The fourth fork  78  transfers the substrates  32  from the dummy substrate conveyor  79  to the adjacent substrate conveyor  81 . Therefore, the substrates  32  from the substrate conveyor  81  are transferred in the Z-axis direction by the first fork  75 , in the Y-axis direction by the second fork  76 , in the Z-axis direction by the third fork  77  and then in the Y-axis direction by the fourth fork  78  and returned to the substrate conveyor  81 . The number of transfer bars provided on the first and third forks  75  and  77  will typically correspond to the number of heater blocks included in each of the heater block rows  72  and  74 , respectively. The second and fourth forks  72  and  74  will typically be installed between the substrate conveyor  81  and the dummy substrate conveyor  79 . As illustrated in  FIG. 7 , the first fork  75  and the second fork  76  will typically be installed on opposite sides of the substrate conveyor  81  with the second fork  76  and the third fork  77  being installed on opposite sides of the dummy substrate conveyor  79 .  
      The third exemplary embodiment is similar to the first and second exemplary embodiments in that the snap cure process is performed gradually using eight heater blocks, but utilizes a different transfer sequence as a result of the altered configuration of the heater blocks. The heater blocks  73 ,  74  may be set at the same temperatures as corresponding heater blocks in the first embodiment and the first and third forks  75  and  77  can each have four transfer bars.  
      Accordingly, the present invention may allow for the vertical and/or horizontal rearrangement of heater blocks to reduce the horizontal area occupied by a snap cure device utilized in a semiconductor chip attaching apparatus. The snap cure device may be incorporated within or arranged inline with a substrate conveyor of a conventional chip attaching apparatus.  
      Although certain exemplary embodiments of the present invention have been described in detail, it should be understood that many variations and/or modifications of the basic inventive concepts may appear to those skilled in the art when instructed by this disclosure and will still fall within the spirit and scope of the present invention as defined in the following claims.