Abstract:
A conductive clip having a riser or post formed along a side thereof includes a notch or opening formed in the riser or post to create a first riser or post section and second riser or post section separated by the notch or opening through which a tiebar extends. The conductive clip organization is will suited for formation as elongated strips of such conductive clips for automated machine assembly of the conductive clips in an integrated circuit package context.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application 61/231,998 filed Aug. 6, 2009 by the applicants herein, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates generally to the manufacture of integrated circuit packages and, more particularly, to the manufacture and packaging of conductive clips for subsequent assembly into or onto a die or dies as used in integrated circuit packages, and, still more particularly, to elongated strips of conductive clips in which successive clips are transferred therefrom on a clip-by-clip basis via a transfer machine into or onto an integrated circuit package for assembly thereto or thereon. 
     In the manufacture of electronic components, including integrated circuits, the various sub-components (circuit dies, discrete components, conductive clips, etc.) are often supplied on or as part of an elongated strip that is often wound on a reel by the manufacturer with that reel then supplied to the customer. For example, integrated circuit dies are often supplied by the manufacturer as a paper strip or tape upon which the dies are adhered in a uniformly spaced apart relationship. The paper strip or tape is supplied to a pick-and-place machine which picks successive dies from the paper strip and places the so-picked dies on a leadframe or other substrate of an integrated circuit package. In addition to the paper strip or tape arrangement, other types of parts, including conductive clips, are formed on blank metallic strips by one or more die-cutting or die-stamping steps to form a succession of properly shaped and spaced-apart conductive clips on the metallic strip. As in the case of the paper tape scheme, the metallic strip can be wound upon a reel for delivery to the customer. 
     In general, the paper tape system arrangement is more expensive to manufacture and use, where conductive clips are involved, relative to arrangements in which a conductive clip is formed as a part of an elongated metallic strip. 
       FIGS. 1A and 1B  illustrate a known conductive clip  10  of the type used, for example, in MOSFET power inverters; typically, these clips are used to make contact with the planar source or drain of a V-FET and effect an electrical connection to a conducive pad on a leadframe or other conductive part of a substrate. As shown, the conductive clip  10  includes a planar contact portion  12  and a riser or post  14  that is bent at some angle (e.g., about 90°) relative to the contact portion  12  of the conductive clip  10 . 
     In a typical application, the planar contact portion is mounted atop a MOSFET to make electrical and mechanical contact with a source or drain thereof with the riser or post  14  extending to a contact pad on a leadframe or other substrate (not shown). The conductive clip  10  is typically fabricated from a conductive metal or alloy such as copper or a copper alloy. 
     As shown in  FIG. 1C , the conductive clips  10  are often manufactured by subjecting an elongated strip of the metal starting-material to a succession of die-stamping steps that punch out material to form upper and lower rails  16  with appropriate sprocket holes  18  and to shape the conductive clips  10  with an additional metal-stamping step or steps to form the risers or posts  14 . As shown, the conductive clips  10  are connected to the upper and lower rails by tiebars  20 ; while the example shown shows two tiebars  20 , additional tiebars may be used. 
       FIGS. 1D and 1E  are perspective views showing a conductive clip  10  and its tiebars  20 . While not shown, each tiebar  20  can have a portion thereof that has a reduced cross-section or a reduced thickness or a score-line to allow the tiebars  20  to fracture or separate thereat when the conductive clip is pulled therefrom by a machine (not shown) for subsequent placement onto, e.g., a MOSFET chip of the type used in power inverters. 
     In general, the strips of so formed conductive clips  10  are wound on a reel (not shown) and supplied to the customer who often use a pick-and-place machine or robot to remove the conductive clips and place them into position in an integrated circuit undergoing assembly. 
     SUMMARY 
     A conductive clip having a laterally extending riser or post and a longitudinally extending riser or post and tiebars extending laterally therefrom includes an opening, notch, gap, or opening formed in at least one of the risers or posts to bifurcate the riser or post to create an opening through which a tiebar can pass. The conductive clip organization is well suited for creating elongated strips of such conductive clips for automated machine assembly of the conductive clips in an integrated circuit package context. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIGS. 1A and 1B  are perspective views of a known type of conductive clip having a post or riser formed along a lateral edge thereof; 
         FIG. 1C  is a plan view of a portion of a strip of conductive clips of the type shown in  FIGS. 1A and 1B ; 
         FIGS. 1D and 1E  are perspective views of the conductive clips of  FIGS. 1A and 1B  showing tiebars extending laterally therefrom; 
         FIGS. 2A ,  2 B,  2 C, and  2 D are perspective views of a type of conductive clip having a riser or post formed along a lateral edge and, additionally, another riser or post extending along a longitudinal edge; 
         FIGS. 3A ,  3 B,  3 C, and  3 D are perspective views of a type of conductive clip having a lateral-edge post or riser and a longitudinal-edge post or riser with tiebars extending laterally therefrom; 
         FIG. 4  is a plan view of a portion of a strip of conductive clips of the types shown in  FIGS. 3A-3D ; 
         FIGS. 4A-4C  illustrate one example of a multi-step process for manufacturing the structure shown in  FIG. 4 ; 
         FIG. 5  is a plan view of a portion of a double-row strip of conductive clips of the types shown in  FIGS. 3A-3D ; 
         FIG. 6  is a plan view of a portion of a strip of conductive clips rotated ninety degrees relative to those shown in  FIGS. 4 and 5 ; 
         FIG. 7  is a plan view of a portion of a double-row strip of conductive clips of the types shown in  FIG. 6 ; and 
         FIG. 8  illustrates a variant of the exemplary conductive clip. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIGS. 2A ,  2 B,  2 C, and  2 D illustrate a variant of the conductive clip discussed above and is designated herein by the reference character  100 . As shown, the conductive clip  100  includes a planar contact portion  102  and a first riser or post  104  formed along a lateral side and which is bent at some angle (e.g., usually about 90°) relative to the plane of the contact portion  102  of the conductive clip  100 . Additionally, the conductive clip  100  includes a riser or post  106  formed along a longitudinal side thereof that, in a manner similar to the riser or post  104 , is similarly bent at some angle (e.g., usually about 90°) relative to the plane of the contact portion  102 . 
     Because the conductive clips  100  of  FIGS. 2A ,  2 B,  2 C, and  2 D have both lateral posts (viz.,  104 ) and longitudinal posts (viz.,  106 ), conventional die-stamping operations cannot form laterally extending tiebars in a manner similar to that shown in  FIGS. 1C-1E . 
       FIGS. 3A ,  3 B,  3 C, and  3 D illustrate a conductive clip  200  that addresses the problem of the conductive clip  100  by a creating tiebar  210  on that side of the clip that includes a riser or post. As shown, the conductive clip  200  includes a planar contact portion  202  and a first riser or post  204  formed or along a lateral side that is bent at some angle (e.g., about 90°) relative to the contact portion  202  of the conductive clip  200  and another riser or post  206  along one longitudinal side thereof that is interrupted by an opening, gap, notch, or slot  208  to define an open space or clearance space on each side of a tiebar  210 . The notch or slot  208  effectively bifurcates the riser or post into first and second spaced-apart sections so that the conductive clip  200  includes laterally extending tiebars  210  in substantially the same plane and location on the contact portion  202  as that for the conductive clip shown in  FIGS. 1D and 1E . 
     As shown in  FIG. 4 , the conductive clips  200  can be formed as part of a strip of such clips along a longitudinally extending axis A x  in which the tiebars  210  support the clips  200  between first and second spaced rails R 1  and R 2  in a manner consistent with  FIG. 1C  as discussed above. 
       FIGS. 4A ,  4 B, and  4 C illustrate one exemplary metal-forming sequence for fabricating a strip of the type shown in  FIG. 4 . In  FIG. 4A , a starting strip of metal is subject to a die-cutting or metal-punching step in which the material between the to-be-formed clips is removed to leave a clip preform as shown in  FIG. 4B . In the preform, the material that is to become the risers or posts remains substantially in the same plane of the strip material, with their respective bend lines (unnumbered) shown in dotted-line. Thereafter, a metal-stamping step ( FIG. 4C ), bends the material along the bend lines to form the risers or posts  204  and  206 . If desired, a preferential separation line or region (not shown) in each tiebar  210  can be formed by a score line, a reduced-thickness zone, and/or a reduced-width zone so that each tiebar  210  will reliably separate from its rails during the subsequent pick-and-place step. 
     If desired and as shown in  FIG. 5 , a double-row of clips  200  can be formed between an upper first rail R 1 , a lower second rail R 2 , and an intermediate rail (unnumbered). 
     If desired and as shown in  FIG. 6 , the conductive clips  200  can be rotated ninety degrees from that shown in  FIG. 4  or  5  to form a more densely packed strip. If desired and in a manner analogous to that shown in  FIG. 5 , a double-row of clips  200  can be formed between an upper first rail R 1 , a lower second rail R 2 , and an intermediate rail (unnumbered). 
     In the above described embodiments the conductive clip is shown as having an approximately rectangular planform with laterally and longitudinally aligned risers or posts; as can be appreciated other planforms and alignments for the risers or posts are not excluded. The preferred embodiments have been described as having one lateral and one longitudinal riser or post, as can be appreciated and as shown at  206   a  in  FIG. 8 , a conductive clip can include a riser or post along each opposite longitudinal (and/or lateral) edge. Additionally, the bottom end each riser or post that contacts a conductive pad on the leadframe or substrate can be formed with an optional “foot” (not shown) to enlarge the contact area. While the notch or slot  208  has been shown as extending into the planar portion  202  of the clip, as represented by the upper tiebar  210  in  FIG. 8 , the notch or slot  208  can be formed so as not to extend into the planar portion of the clip, as shown on the lower side of the clip shown in  FIG. 8 . 
     As will be apparent to those skilled in the art, various changes and modifications may be made to the illustrated embodiment of the present invention without departing from the spirit and scope of the invention as determined in the appended claims and their legal equivalent.