Abstract:
A method for bonding includes positioning a bonding strip adjacent a sole first bond head, the bonding strip having a plurality of strip units, and bonding, with only the first bond head, a first number of the plurality of strip units. The method further includes transporting the bonding strip from the first bond head and positioning the bonding strip adjacent a sole second bond head, and bonding, with only the second bond head, a remaining number of the plurality of strip units on the bonding strip. In one embodiment, the method also includes heating at least one of the plurality of strip units prior to bonding the bonding strip. In one embodiment, the method also includes clamping, with a sole clamp, the bonding strip, thereby limiting warpage of the bonding strip.

Description:
This application claims priority under 35 USC §119(e)(1) of provisional application No. 60/094,053 filed Jul. 24, 1998 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     This invention relates generally to bonding systems and, more particularly, to a system and method for dual head bonding. 
     BACKGROUND OF THE INVENTION 
     Bonding systems are used to complete an interconnection between an integrated circuit chip and lead fingers of a bonding strip by bonding together or electrically coupling a plurality of bond pads of the integrated circuit chip to corresponding lead fingers on the bonding strip. In mass production, the bonding strip often includes a plurality of integrated circuit chips that may be separated after the bond pads of each integrated circuit chip have been bonded to corresponding lead fingers on the bonding strip. Thus, the bonding strip often includes a plurality of strip units with each strip unit having a single integrated circuit chip electrically coupled to lead fingers of the bonding strip. 
     One example of a bonding system is a dual head bonding system. Dual head bonding systems generally have two bond heads adjacent and in close proximity to one another for simultaneously bonding different strip units of the same bonding strip. Clamps are generally used to secure the bonding strip in two places while the two bond heads simultaneously bond different strip units of the bonding strip. Additionally, the dual head bonding system generally includes a heater positioned adjacent the two bond heads for heating the bonding strip during bonding. The dual head bonding system also generally includes a transfer mechanism for positioning various strip units of the bonding strip adjacent the two bond heads and for transporting the bonding strip to and from the two bond heads. 
     Dual head bonding systems, however, suffer several disadvantages. For example, since both bond heads are used to simultaneously bond different strip units of the same bonding strip, the two bond heads must be positioned so that the distance between the two bond heads is a multiple of the distance between strip units of the bonding strip. Thus, processing different bonding strips requires repositioning each bond head for each different bonding strip. Additionally, as heat is applied to the bonding strip during the bonding process, bonding strip warpage occurs in an area of the bonding strip between the clamps due to temperature expansion of the bonding strip. As the bonding strip warps, the interconnection between the integrated circuit chip and the lead fingers of the bonding strip may become defective. 
     SUMMARY OF THE INVENTION 
     Accordingly, a need has arisen for an improved dual head bonding system and method. The present invention provides an improved dual head bonding system and method that addresses shortcomings of prior dual head bonding systems and improves efficiency. 
     According to one embodiment of the invention, a method for bonding includes positioning a bonding strip adjacent a sole first bond head, the bonding strip having a plurality of strip units, and bonding, with only the first bond head, a first number of the plurality of strip units. The method further includes transporting the bonding strip from the first bond head and positioning the bonding strip adjacent a sole second bond head, and bonding, with only the second bond head, a remaining number of the plurality of strip units on the bonding strip. 
     According to another embodiment of the invention, a bonding system includes a first bond head operable to bond a bonding strip, the bonding strip having a plurality of strip units. The system also includes a second bond head operable to bond the bonding strip. The system further includes a first indexer operable to successively position each of a first number of the plurality of strip units adjacent the first bond head and a second indexer operable to transfer the bonding strip from the first bond head to the second bond head and successively position each of a second number of the plurality of strip units adjacent the second bond head. 
     The invention provides several technical advantages. For example, in one embodiment of the invention, the dual head bonding system provides for greater reliability of the bonding strips by substantially eliminating heat related warpage of the bonding strip during the bonding process. In the same embodiment, the dual head bonding system provides greater efficiency than conventional dual head bonding systems by utilizing two indexers for retrieving, transporting, and sequencing bonding strips between the bond heads. 
     Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions taken in connection with the accompanying drawings in which: 
     FIG. 1 is an isometric drawing of a dual head bonding system constructed in accordance with the present invention; 
     FIG. 2A is a drawing illustrating a plan view of a bonding strip having a plurality of strip units; 
     FIG. 2B is a drawing illustrating a plan view of a bonding strip having an array of columns and rows of strip units; 
     FIG. 3 is a drawing illustrating a clamp for clamping bonding strips constructed in accordance with the present invention; 
     FIG. 4 is a schematic drawing illustrating a bonding sequence performed using a dual head bonding system constructed in accordance with the present invention on bonding strips having a quantity of strip units equal to an even integer; 
     FIG. 5 is a schematic drawing illustrating a bonding sequence performed using a dual head bonding system constructed in accordance with the present invention on bonding strips having a quantity of strip units equal to an odd integer; and 
     FIG. 6 is a schematic drawing illustrating a BowTI™ bonding configuration sequence performed using a dual head bonding system constructed in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention and its advantages are best understood by referring to FIGS. 1 through 5 of the drawings, like numerals being used for like and corresponding parts of the various drawings. 
     FIG. 1 illustrates an isometric view of a dual head bonding system  10  incorporating the teachings of the present invention. Bonding system  10  includes an input unit  12 , two bond heads  14  and  16 , an output unit  18 , and a transfer system  20 . In general, transfer system  20  retrieves bonding strips  22  from input unit  12  and transports bonding strips  22  between input unit  12 , bond heads  14  and  16 , and output unit  18 . As will be described in greater detail in conjunction with FIG. 2A, bond heads  14  and  16  bond bonding strips  22  as bonding strips  22  are transported to and between bond heads  14  and  16  using transfer system  20 . 
     FIG. 2A is a plan view of bonding strip  22  having a single row of strip units  24 , and FIG. 2B is a plan view of bonding strip  22  having an array of columns and rows of strip units  24 . Although not shown in FIGS. 2A and 2B, bond heads  14  and  16  bond bonding strips  22  as bonding strips  22  are transported to and between bond heads  14  and  16  using transfer system  20 . As best illustrated in FIG. 2A, each strip unit  24  includes an integrated circuit chip  26  having a plurality of bond pads  28 . Each strip unit  24  of bonding strip  22  also includes lead fingers  32 . Bond heads  14  and  16  electrically couple, bond or interconnect lead fingers  32  to bond pads  28  of integrated circuit chips  26 . For example, lead fingers  32  may be electrically coupled to bond pads  28  using wires  34 . 
     Referring to FIG. 1, in one embodiment of the invention, input unit  12  includes an elevator system  36  for retrieving bonding strips  22  from a magazine or carrier (not explicitly shown) and supplying bonding strips  22  to transfer system  20 . However, input unit  12  may include other suitable methods or devices for supplying bonding strips  22  to transfer system  20 . For example, input unit  12  may be part of a continuous flow conveyor system (not explicitly shown). Additionally, in one embodiment of the invention, output unit  18  includes an elevator system  38  for receiving bonding strips  22  from transfer system  20  and transporting bonding strips  22  to a magazine or carrier (not explicitly shown). However, output unit  18  may include other suitable methods or systems for receiving bonding strips  22  from transfer system  20 . For example, output unit  18  may also be part of a continuous flow conveyor system (not explicitly shown) for transporting bonding strips  22  to packaging or subsequent processing operations. 
     Bonding system  10  also includes clamps  40  and  42  adjacent bond heads  14  and  16 , respectively. Clamps  40  and  42  secure bonding strips  22  adjacent bond heads  14  and  16 , respectively, while bond heads  14  and  16  bond bonding strips  22 . As illustrated in FIG. 1, each clamp  40  and  42  secures a single bonding strip  22  adjacent a single bond head  14  and  16 , respectively. For example, clamp  40  secures a single bonding strip  22  adjacent bond head  14  while bond head  14  bonds bonding strip  22 . By securing a single bonding strip  22  adjacent each bond head  14  and  16 , heat related warpage of bonding strips  22  during the bonding process is substantially eliminated because each bonding strip  22  is independently clamped adjacent a single bond head  14  or  16 . Thus, each end of bonding strip  22  remains unconstrained during the bonding process allowing each end of bonding strip  22  to expand under heat. Therefore, bonding system  10  provides a more reliable interconnection between bond pads  28  of integrated circuit chips  26  and lead fingers  32  than conventional dual head bonding systems. Clamps  40  and  42  are shown and described in greater detail in conjunction with FIG.  3 . 
     FIG. 3 is a drawing illustrating one embodiment of clamp  40 ; clamp  42  may be constructed in the same manner as described below for clamp  40 . Clamp  40  includes a base  41  and a cover  43 . Cover  43  includes an opening  47 . In operation, bonding strips  22  are positioned between base  41  and cover  43  so that bonding strips  22  are secured between base  41  and cover  43 . Cover  43  may also include a boss (not explicitly shown) on a surface of cover  43  extending outwardly toward base  41  for seating against bonding strips  22 . Opening  47  allows bonding of strip units  24  of bonding strips  22  while bonding strips  22  are secured using clamp  40 . Clamp  40  is illustrated in FIG. 3 having a single opening  47 ; however, clamps  40  and  42  may also include a plurality of openings  47  for bonding a plurality of strip units  24  of bonding strip  22  while bonding strip  22  is secured adjacent a single bond head  14  or  16 . 
     Referring to FIG. 1, transfer system  20  of bonding system  10  includes an indexer  44  having grippers  46  and  48  and an indexer  50  having grippers  52  and  54 . Indexers  44  and  50  transport bonding strips  22  between input unit  12 , bond heads  14  and  16 , and output unit  18 . Grippers  46 ,  48 ,  52  and  54  open and close to release or secure, respectively, bonding strips  22  for transport between input unit  12 , bond heads  14  and  16 , and output unit  18 . For example, indexer  44 , using gripper  46 , retrieves bonding strips  22  from input unit  12  and transports bonding strips  22  to bond head  14 . Although FIG. 1 illustrates bonding strip  22  material flow from left to right, or from input unit  12  to output unit  18 , indexers  44  and  50  may also be used to transport bonding strips  22  in the opposite direction, for example, from bond head  16  to bond head  14 . Thus, bonding system  10  may be linked or combined with other bonding strip  22  processing equipment for continuous flow manufacturing of bonding strips  22  having bonding strip  22  material flow in any direction. 
     In the embodiment illustrated in FIG. 1, indexers  44  and  50  are driven by lead screw motor systems  56  and  58 , respectively; however, other suitable methods or devices may be used to drive indexers  44  and  50 . Therefore, indexers  44  and  50  function independently of one another allowing for independent movement of indexers  44  and  50 . For example, indexer  44  may be driven toward input unit  12  for retrieving another bonding strip  22  while indexer  50  is driven toward output unit  18  for depositing another bonding strip  22  in output unit  18 . Thus, indexers  44  and  50  are independently driven for increased flexibility and improved efficiency of bonding system  10 . 
     Additionally, indexers  44  and  50  index or position bonding strips  22  for transport to and between bond heads  14  and  16 . For example, bond heads  14  and  16  are located at predetermined distances from each other and at predetermined distances from input unit  12  and output unit  18 . For example, these predetermined distances may be based on a length or type of bonding strip  22  being processed using bonding system  10 . Indexer  44  indexes bonding strip  22  so that when indexer  44  completes transporting bonding strip  22  from input unit  12  to bond head  14 , one or more desired strip units  24  of bonding strip  22  are positioned adjacent bond head  14  in preparation for bonding using bond head  14 . These predetermined distances and the distances between strip units  24  of bonding strips  22  are stored in a computer or processor (not explicitly shown) so that indexers  44  and  50  accurately position bonding strips  22  throughout bonding system  10 . These indexing and positioning operations are described in greater detail with respect to FIGS. 3 through 5. 
     Additionally, indexers  44  and  50  cooperate with clamps  40  and  42  so that once bonding strips  22  have been indexed, indexers  44  and  50  accurately position strip units  24  of bonding strips  22  throughout bonding system  10 . For example, indexer  44  indexes bonding strip  22  using gripper  46  and transports bonding strip  22  to bond head  14 . Clamp  40  secures bonding strip  22  adjacent bond head  14  prior to gripper  46  releasing bonding strip  22 . After bond head  14  completes bonding on bonding strip  22 , gripper  46  of indexer  44  secures bonding strip  22  prior to clamp  40  releasing bonding strip  22 . Thus, once bonding strip  22  has been indexed, clamps  40  and  42  and grippers  46 ,  48 ,  52 , and  54  cooperate to maintain accurate indexing locations of bonding strips  22  throughout bonding system  10 . 
     Grippers  46 ,  48 ,  52  and  54  also function independently of each other. Therefore, each gripper  46 ,  48 ,  52 , or  54  independently opens and closes to release or secure, respectively, bonding strips  22 . Thus, indexers  44  and  50  can transport up to four bonding strips  22 , for example, with each gripper  46 ,  48 ,  52 , and  54  securing a single bonding strip  22 . As will be described in greater detail in conjunction with FIGS. 3 through 5, grippers  46 ,  48 ,  52  and  54  may be alternately used for different tasks throughout bonding system  10  depending on variables such as the quantity of strip units  24  included in bonding strip  22 , the distance between strip units  24 , and the sequence of material bonding operations desired. Thus, bonding system  10  provides greater flexibility than conventional dual head bonding systems. 
     In one embodiment of the invention, bonding system  10  also includes a pre-heat station  60  and a post-bond bake station  62 . Pre-heat station  60  heats one or more of strip units  24  of bonding strip  22  prior to transporting bonding strip  22  to bond head  14 . Post-bond bake station  62  heats one or more of strip units  24  of bonding strip  22  after bonding strip units  24 . In one embodiment of the invention, pre-heat station  60  and post-bond bake station  62  include electrical coil resistance heating elements (not explicitly shown); however other suitable heating methods or devices may be used for heating bonding strips  22 . Pre-heat station  60  and post-bond bake station  62  provide several technical advantages. For example, heating strip units  24  of bonding strip  22  prior to and after bonding bonding strip  22  increases the shear strength of the bond and enhances the intermetallic growth between bonding materials. 
     In operation, for example, indexer  44  retrieves bonding strip  22  from input unit  12  and positions one or more of strip units  24  of bonding strip  22  adjacent pre-heat station  60 . After pre-heat station  60  heats strip units  24 , indexer  44  transports bonding strip  22  to bond head  14  for bonding. Additionally, for example, after bonding strip units  24  using bond head  16 , indexer  50  transports bonding strip  22  from bond head  16  to post-bond bake station  62  and positions one or more of strip units  24  adjacent post-bond bake station  62 . After post-bond bake station  62  heats strip units  24 , indexer  50  transports bonding strip  22  to output unit  18 . Thus, bonding system  10  provides an improved interconnection between bond pads  28  of integrated circuit chip  26  and lead fingers  32  by using pre-heat station  60  and post-bond bake station  62  to enhance the bonding material properties of bonding strips  22 . 
     Additionally, in one embodiment of the invention, bonding system  10  also includes heaters  66  and  68  adjacent bond heads  14  and  16 , respectively. In operation, heaters  66  and  68  heat one or more strip units  24  of bonding strips  22  prior to and after bonding strip units  24  of bonding strips  22 . For example, gripper  46  of indexer  44  retrieves bonding strip from input unit  12  and positions one or more of strip units  24  adjacent pre-heat station  60 . After strip units  24  have been heated using pre-heat station  60 , indexer  44  transports bonding strip  22  to bond head  14 . While one strip units  24  are bonded using bond head  14 , heater  66  heats one or more adjacent strip units  24  in preparation for bonding using bond head  14 . Thus, heaters  66  and  68  are also used to enhance the interconnection between bond pads  28  of integrated circuit chip  26  and lead fingers  32  of bonding strips  22 . A more detailed description for using heaters  66  and  68  in bonding system  10  will be provided in conjunction with FIGS. 3 through 5. 
     Thus, according to the above-described embodiments of the invention, bonding system  10  provides for an efficient and flexible method of processing different bonding strip  22  configurations without having the locations of bond heads  14  and  16  adjusted or altered. The following description provided in conjunction with FIGS. 3 through 5 illustrates the efficiency and flexibility of bonding system  10  processing a variety of bonding strip  22  and bonding configurations. 
     FIG. 4 is a schematic drawing illustrating the beginning of an indexing sequence of a bonding strip  70  between bond heads  14  and  16  wherein bonding strip  70  includes a quantity of strip units equal to an even integer. Numbers  500  through  550  illustrated in FIG. 4 represent a series of successive steps during the processing of bonding strip  70 . 
     As illustrated in FIG. 4, bonding strip  70  includes strip units  72 ,  74 ,  76 ,  78 ,  80 , and  82 . Although not illustrated in FIG. 4, prior to a first step  500 , gripper  46  of indexer  44  retrieves bonding strip  70  from input unit  12  and positions strip unit  72  adjacent pre-heat station  60  so that pre-heat station  60  heats strip unit  72  prior to bond head  14  bonding strip unit  72 . Additionally, indexer  44  indexes bonding strip  70  so that upon completion of transporting bonding strip  70  to bond head  14 , strip unit  72  will be positioned adjacent bond head  14 . 
     After pre-heating strip unit  72 , indexer  44  transports bonding strip  70  to bond head  14  at step  500 . Although not illustrated in FIG. 4, before gripper  46  releases bonding strip  70 , clamp  40  secures bonding strip  70  adjacent bond head  14 . Thus, clamp  40  and gripper  46  cooperate to control the indexed location of bonding strip  70 . For example, since clamp  40  secures bonding strip  70  prior to gripper  46  releasing bonding strip  70 , gripper  46  retrieves and secures bonding strip  70  from clamp  40  in the same indexed location. Thus, clamp  40  and gripper  46  cooperate to control the indexed location of bonding strip  70  so that indexer  44  accurately positions bonding strip  70  at the next processing location within bonding system  10 . Accordingly, clamps  40  and  42  secure bonding strip  70  prior to grippers  46 ,  48 ,  52 , or  54  releasing bonding strip  70  throughout bonding system  10 . 
     While bond head  14  bonds strip unit  72 , heater  66  pre-heats strip unit  74  in preparation for bonding. Heaters  66  and  68  are shown adjacent bonding strip  70  and bond heads  14  and  16  in FIGS. 3 through 5 to illustrate the position of various strip units in relation to heaters  66  and  68  during the indexing sequence. 
     After bond head  14  completes bonding strip unit  72 , gripper  46  secures bonding strip  70  and positions strip unit  74  adjacent bond head  14  at a step  510 . While bond head  14  bonds strip unit  74 , strip units  72  and  76  are post-bond baked and pre-heated, respectively, using heater  66 . 
     After bond head  14  completes bonding strip unit  74 , gripper  48  of indexer  44  secures bonding strip  70  and positions strip unit  76  adjacent bond head  14  at a step  520 . While bond head  14  bonds strip unit  76 , strip units  74  and  78  are post-bond baked and pre-heated, respectively, using heater  66 . 
     Additionally, after clamp  40  secures bonding strip  70  from gripper  46  of indexer  44 , indexer  44  is free to retrieve the next bonding strip, for example, bonding strip  84 , from input unit  12  and position strip unit  86  of bonding strip  84  adjacent pre-heat station  60 . Indexer  44  may retrieve bonding strip  84  at any time while clamp  40  secures bonding strip  70  adjacent bond head  14 . For example, indexer  44  may retrieve bonding strip  84  while bond head  14  bonds strip unit  72  at step  500 , while bond head  14  bonds strip unit  74  at step  510 , or while bond head bonds strip unit  76  at step  520 . Thus, indexers  44  and  50  may be efficiently performing additional processing operations while bond heads  14  and  16  are bonding. 
     Gripper  52  of indexer  50  secures bonding strip  70  and transports bonding strip  70  from bond head  14  to bond head  16  at a step  530 . Indexer  50  positions strip unit  78  adjacent bond head  16  for bonding using bond head  16 . While bond head  16  bonds strip unit  78 ,.strip units  76  and  80  are post-bond baked and pre-heated, respectively, using heater  68 . Thus, although bond head  14  bonds strip unit  76 , heater  68  adjacent bond head  16  post-bond bakes strip unit  76 . Also, at step  530 , gripper  46  of indexer  44  positions strip unit  86  of bonding strip  84  adjacent bond head  14 . While bond head  14  bonds strip unit  86 , strip unit  88  is pre-heated using heater  66 . 
     Gripper  52  of indexer  50  secures bonding strip  70  and positions strip unit  80  adjacent bond head  16  at a step  540 . While bond head  16  bonds strip unit  80 , strip units  78  and  82  are post-bond baked and pre-heated, respectively, using heater  68 . Additionally, at step  540 , gripper  46  of indexer  44  secures bonding strip  84  and positions strip unit  88  adjacent bond head  14 . While bond head  14  bonds strip unit  88 , strip units  86  and  90  are post-bond baked and pre-heated, respectively, using heater  66 . 
     Gripper  52  of indexer  50  secures bonding strip  70  and positions strip unit  82  adjacent bond head  16  at a step  550 . While bond head  16  bonds strip unit  82 , strip unit  80  is post-bond baked using heater  68 . Also, at step  550 , gripper  48  of indexer  44  secures bonding strip  84  and positions strip unit  90  adjacent bond head  14 . While bond head  14  bonds strip unit  90 , strip units  88  and  92  are post-bond baked and pre-heated, respectively, using heater  66 . 
     After bond head  16  completes bonding strip unit  82  of bonding strip  70 , gripper  54  of indexer  50  secures bonding strip  70  and transports bonding strip  70  to post-bond bake station  62 . Indexer  50  positions strip unit  82  adjacent post-bond bake station  62  for heating strip unit  82 . Also, gripper  52  of indexer  50  secures bonding strip  84  and positions strip unit  92  of bonding strip  84  adjacent bond head  16  for bonding using bond head  16 . Thus, bond head  16  will bond strip units  94  and  96  of bonding strip  84 . Additionally, while indexer  50  transports bonding strips  70  and  84 , indexer  44  transports the next bonding strip to bond head  14  to continue the above-described indexing sequence. 
     Accordingly, bonding system  10  provides an efficient method of sequencing bonding strips  22  from input unit  12  to bond heads  14  and  16  and output unit  18 . For example, although the above-described sequence describes using grippers  46 ,  48 ,  52  and  54  at particular steps during the sequencing process, the use of particular grippers  46 ,  48 ,  52  and  54  may be varied to meet a desired sequence of events or processes. 
     FIG. 5 is a schematic drawing illustrating an indexing sequence of bonding strips  98 ,  100 , and  102  between bond heads  14  and  16  wherein each bonding strip  98 ,  100 , and  102  includes a quantity of strip units  24  equal to an odd integer. Thus, bonding strip  98  includes strip units  104 ,  106 ,  108 ,  110 , and  112 , bonding strip  100  includes strip units  114 ,  116 ,  118 ,  120  and  122 , and bonding strip  102  includes strip units  124 ,  126 ,  128 ,  130 , and  132 . Numbers  600  through  640  illustrated in FIG. 5 represent a series of successive steps during the processing of bonding strips  98 ,  100 , and  102 . 
     As illustrated in FIG. 5, strip unit  108  of bonding strip  98  is positioned adjacent bond head  16  at a first step  600 . Although not illustrated in FIG. 5, strip units  104  and  106  have been bonded using bond head  14  prior to indexer  50  transporting bonding strip  98  to bond head  16 . While bond head  16  bonds strip unit  108 , strip units  106  and  110  are post-bond baked and pre-heated, respectively, using heater  68 . 
     Additionally, at step  600 , indexer  44  transports bonding strip  100  to bond head  14  and positions strip unit  114  adjacent bond head  14 . Although not shown in FIG. 5, strip unit  114  is pre-heated using pre-heat station  60  prior to indexer  44  transporting bonding strip  100  to bond head  14 . While bond head  14  bonds strip unit  114 , strip unit  116  is pre-heated using heater  66 . 
     Indexer  50  secures bonding strip  98  and positions strip unit  110  adjacent bond head  16  at a step  610 . While bond head  16  bonds strip unit  110 , strip units  108  and  112  are post-bond baked and pre-heated, respectively, using heater  68 . Also, at step  610 , indexer  44  secures bonding strip  100  and positions strip unit  116  adjacent bond head  14 . While bond head  14  bonds strip unit  116 , strip units  114  and  118  are post-bond baked and pre-heated, respectively, using heater  66 . 
     Indexer  50  secures bonding strip  98  and positions strip unit  112  adjacent bond head  16  at a step  620 . While bond head  16  bonds strip unit  112 , strip unit  110  is post-bond baked using heater  68 . Additionally, at step  620 , indexer  44  secures bonding strip  100  and positions strip unit  118  adjacent bond head  14 . While bond head  14  bonds strip unit  118 , strip units  116  and  120  are post-bond baked and pre-heated, respectively, using heater  66 . 
     Indexer S 0  secures bonding strip  100  and positions strip unit  120  adjacent bond head  16  at a step  630 . Although not explicitly shown in FIG. 5, indexer  50  also secures bonding strip  98  and transports bonding strip  98  to post-bond bake station  62 . For example, gripper  52  may be used to secure bonding strip  100  and gripper  54  may be used to secure bonding strip  98  and position strip unit  112  of bonding strip  98  adjacent post-bond bake station  62 . As illustrated in FIG. 5, strip unit  120  of bonding strip  100  is pre-heated using heater  66  adjacent bond head  14  prior to indexer  50  transporting bonding strip  100  to bond head  16 . While bond head  16  bonds strip unit  120 , strip units  118  and  122  are post-bond baked and pre-heated, respectively, using heater  68 . 
     Also, at step  630 , indexer  44  secures bonding strip  102  and transports bonding strip  102  to bond head  14 . Indexer  44  positions strip unit  124  adjacent bond head  14  for bonding using bond head  14 . Although not explicitly shown in FIG. 5, strip unit  124  is pre-heated using pre-heat station  60  prior to indexer  44  transporting bonding strip  102  to bond head  14 . While bond head  14  bonds strip unit  124 , strip unit  126  is pre-heated using heater  66 . 
     Indexer  50  secures bonding strip  100  and positions strip unit  122  adjacent bond head  16  at a step  640 . While bond head  16  bonds strip unit  122 , strip unit  120  is post-bond baked using heater  68 . Also, at step  640 , indexer  44  secures bonding strip  102  and positions strip unit  126  adjacent bond head  14 . While bond head  14  bonds strip unit  126 , strip units  124  and  128  are post-bond baked and pre-heated, respectively, using heater  66 . 
     Therefore, according to the above-described embodiment of the invention, both bond heads  14  and  16  are utilized to bond bonding strips  22  having a quantity of strip units  24  equal to an odd integer. Thus, bonding system  10  provides for greater efficiency than conventional dual head bonding systems. For example, although not explicitly shown in FIG. 5, according to the sequence of steps  600  through  640  illustrated in FIG. 5, bond head  16  bonds strip units  128 ,  130 , and  132  of bonding strip  102 . Thus, bonding system  10  uses a repeating sequence of steps for processing bonding strips between bond heads  14  and  16  so that neither bond head  14  nor bond head  16  is idle. 
     For example, for a bonding strip  22  having a quantity of strip units  24  equal to five, bond head  14  bonds two of the five strip units  24  while bond head  16  bonds the remaining three strip units  24 . However, the next bonding strip  22  to be processed using bond head  14  has three of its five strip units  24  processed using bond head  14  while bond head  16  bonds the remaining two strip units  24 . Thus, using this repeating sequence of steps, neither bond head  14  nor bond head  16  is idle. Thus, bonding system  10  provides greater efficiency than conventional bonding systems. 
     FIG. 6 is a schematic drawing illustrating an indexing sequence for bonding strips  134  and  136  wherein each strip unit  24  of bonding strips  134  and  136  receives a BowTI™ bonding configuration using bond heads  14  and  16 . Numbers  700  through  750  illustrated in FIG. 6 represent a series of successive steps during processing of bonding strips  134  and  136 . 
     As illustrated in FIG. 6, bonding strip  134  includes strip units  138 ,  140 ,  142 ,  144 ,  146 , and  148 , and bonding strip  136  includes strip units  150 ,  152 ,  154 ,  156 ,  158 , and  160 . Strip unit  138  of bonding strip  134  is positioned adjacent bond head  14  at a first step  700 . Additionally, strip unit  150  of bonding strip  136  is positioned adjacent bond head  16 . Although not explicitly shown in FIG. 6, indexer  44  is used to transport bonding strip  134  to bond head  14 , and indexer  50  is used to transport bonding strip  136  from bond head  14  to bond head  16 . Additionally, as previously described in conjunction with FIGS. 3-4, pre-heat station  60 , heaters  66  and  68 , and post-bond bake station  62  may be used to heat strip units  138 ,  140 ,  142 ,  144 ,  146 , and  148  of bonding strip  134  and strip units  150 ,  152 ,  154 ,  156 ,  158 , and  160  of bonding strip  136  prior to and after bonding using bond heads  14  and  16 . 
     Indexer  50  secures bonding strip  136  and positions strip unit  152  adjacent bond head  16  at a step  710 . Additionally, at step  710 , indexer  44  secures bonding strip  134  and positions strip unit  140  adjacent bond head  14 . Indexer  50  secures bonding strip  136  and positions strip unit  154  adjacent bond head  16  at a step  720 . Also, at step  720 , indexer  44  secures bonding strip  134  and positions strip unit  142  adjacent bond head  14 . 
     Indexer  50  secures bonding strip  136  and positions strip unit  156  adjacent bond head  16  at a step  730 . Also, at step  730 , indexer  44  secures bonding strip  134  and positions strip unit  144  adjacent bond head. Indexer  50  secures bonding strip  136  and positions strip unit  158  adjacent bond head  16  at a step  740 . Also, at step  740 , indexer  44  secures bonding strip  134  and positions strip unit  146  adjacent bond head  14 . 
     Indexer  50  secures bonding strip  136  and positions strip unit  160  adjacent bond head  16  at a step  750 . Also, at step  750 , indexer  44  secures bonding strip  134  and positions strip unit  148 .adjacent bond head  14 . Although not explicitly shown in FIG. 6, after bond heads  14  and  16  complete bonding strip units  148  and  160 , respectively, indexer  44  transports another bonding strip  22  from input unit  12  to bond head  14  while indexer  50  transports bonding strips  134  and  136  to bond head  16  and output unit  18 , respectively. 
     Therefore, according to the above-described embodiment of the invention, bonding system  10  may be used for bonding a BowTI™ configuration to bonding strips  22  by bonding in one direction using bond head  14 , for example, vertically, and bonding in an opposite direction using bond head  16 , for example, horizontally, Thus, bonding system  10  can be used to efficiently bond a variety of bonding configurations to bonding strips  22 . 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations, can be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.