Patent Publication Number: US-2022223503-A1

Title: Spring bar leadframe, method and packaged electronic device with zero draft angle

Description:
BACKGROUND 
     The cost of manufacturing electronic devices can be reduced by increasing the device count of a given lead frame panel (also referred to as a lead frame sheet or strip). Columns of devices of a lead frame sheet can be interdigitated to increase the device density, but interdigitated devices require trim and form dies to singulate or separate individual packaged devices from the lead frame. Trim and form dies are also used in electronic device manufacturing to cut and then form leads of individual devices while part of a lead frame strip having rows and columns of partially completed devices. However, multiple trim and form die sets are needed for different lead frame strip configurations in manufacturing a variety of different devices having different lead counts and configurations. 
     SUMMARY 
     A lead frame is provided according to one aspect. The lead frame includes a metal structure with prospective device portions arranged in rows and columns along respective first and second directions. The columns include first columns and second columns, where at least some of the first columns are adjacent to one of the second columns. The lead frame includes punch structures with a punch bar that extends along the second direction from a first end of a respective first column to a first clamp portion of the metal structure. The lead frame also includes stretch structures with a spring bar that extends from the second end of a respective first column to a second clamp portion of the metal structure. 
     In one example, the spring bar extends along an arcuate path. In one example, the respective punch structures include a second punch bar that extends along the second direction from the first end of the respective first column to the first clamp portion of the metal structure, and the respective stretch structures include a second spring bar that extends along a second arcuate path from the second end of the respective first column to the second clamp portion of the metal structure. In one example, the respective spring bar and the second spring bar include first and second arcuate portions. 
     In one implementation, the punch bar is deformable along a third direction normal to a plane of the first and second directions, and the spring bar is configured to extend along the second direction to allow movement of the respective first column along the second direction toward the first clamp portion of the metal structure. 
     In one example, the first columns have first device portions that include a respective first die attach pad and respective first lead portions, and the second columns have second device portions that include a respective second die attach pad and respective second lead portions. In one implementation, at least some of the first lead portions of a given one of the first columns are connected to a respective one of the second lead portions of a second device portion of an adjacent one of the second columns. In one example, the first columns and the second columns are alternating. In one example, the spring bar is configured to extend along the second direction toward the first clamp portion by a pitch spacing distance of the first lead portions in response to deformation of the punch bar by a punch depth dimension. 
     A method is provided according to another aspect. The method includes attaching first semiconductor dies to respective first die attach pads of first device portions of respective first columns of a lead frame, and attaching second semiconductor dies to respective second die attach pads of second device portions of respective second columns of the lead frame. The method further includes performing a molding process and separating individual packaged electronic devices of the respective first and second columns from one another. The molding process encloses the first semiconductor dies of each respective first columns in a single respective first package structure, and encloses the second semiconductor dies of each respective second column in a single respective second package structure. 
     In one example, the lead frame includes rows that extend along a first direction and the first and second columns extend along a perpendicular second direction, and the method further includes cutting through the lead frame and the first and second package structures along cut lines between the first device portions of the respective first columns and between the second device portions of the respective second columns, where the cut lines are parallel to the first direction. 
     In one example, moving the first columns along the second direction relative to the second columns includes deforming punch bars proximate first ends of the respective first columns along a third direction normal to a plane of the first and second directions to extend spring bars proximate second ends of the respective first columns along the second direction. In one implementation moving the first columns along the second direction includes moving the first columns by a pitch spacing distance of the first lead portions relative to the second columns. 
     In one example, before performing the molding process, the method further includes performing an electrical connection process that electrically couples at least one of the first lead portions to a conductive feature of the respective first semiconductor die, and electrically couples at least one of the second lead portions to a conductive feature of the respective second semiconductor die. 
     In one example, before separating the individual packaged electronic devices from one another, the method further includes performing a lead trimming process that cuts through the lead frame along trim lines to separate respective first and second lead portions of adjacent ones of the first and second columns of the lead frame, where the trim lines are parallel to the second direction, and moving the first columns along the second direction relative to the second columns. 
     An electronic device is provided according to another aspect. The electronic device includes a molded package structure having a first side, a second side spaced apart from the first side along a first direction, a first end, a second end spaced apart from the first end along a second direction, as well as a top and a bottom spaced apart from the top along a third direction, where the second direction is perpendicular to the first direction and the third direction is normal to a plane of the first and second directions. The electronic device also includes a semiconductor die enclosed by the molded package structure, first conductive leads along the first side, at least one of the first conductive leads being electrically coupled to the semiconductor die, and second conductive leads along the second side. At least one of the second conductive leads is electrically coupled to the semiconductor die, and the respective first and second ends are planar. 
     In one example, the respective first and second sides include a first portion that extends from the top to a mold parting line at a first angle to a plane of the second and third directions, and a second portion that extends from the bottom to the mold parting line at a second angle to the plane of the second and third directions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial top view of a lead frame with interdigitated columns, as well as punch structures and stretch structures at respective ends of the odd-numbered columns according to an embodiment. 
         FIG. 2  is a flow diagram of a method according to another embodiment. 
         FIGS. 3-16  show the lead frame of  FIG. 1  in a fabrication process to produce packaged electronic devices. 
         FIG. 17  is a perspective view of a packaged electronic device according to another embodiment. 
         FIGS. 18 and 19  are partial top views of a lead frame with interdigitated columns and another embodiment of stretch structures at the bottom ends of the odd-numbered columns. 
         FIGS. 20 and 21  are partial top views of a lead frame with interdigitated columns and another embodiment of stretch structures at the bottom ends of the odd-numbered columns. 
         FIGS. 22 and 23  are partial top views of a lead frame with interdigitated columns and another embodiment of stretch structures at the bottom ends of the odd-numbered columns. 
         FIGS. 24 and 25  are partial top views of a lead frame with interdigitated columns and another embodiment of stretch structures at the bottom ends of the odd-numbered columns. 
         FIGS. 26 and 27  are partial top views of a lead frame with interdigitated columns and another embodiment of stretch structures at the bottom ends of the odd-numbered columns. 
         FIGS. 28 and 29  are partial top views of a lead frame with interdigitated columns and another embodiment of stretch structures at the bottom ends of the odd-numbered columns. 
         FIGS. 30 and 31  are partial top views of a lead frame with interdigitated columns and another embodiment of stretch structures at the bottom ends of the odd-numbered columns. 
         FIGS. 32 and 33  are partial top views of a lead frame with interdigitated columns and another embodiment of stretch structures at the bottom ends of the odd-numbered columns. 
         FIGS. 34 and 35  are partial top views of a lead frame with interdigitated columns and another embodiment of stretch structures at the bottom ends of the odd-numbered columns. 
     
    
    
     DETAILED DESCRIPTION 
     In the drawings, like reference numerals refer to like elements throughout, and the various features are not necessarily drawn to scale. Also, the term “couple” or “couples” includes indirect or direct electrical or mechanical connection or combinations thereof. For example, if a first device couples to or is coupled with a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via one or more intervening devices and connections. One or more operational characteristics of various circuits, systems and/or components are hereinafter described in the context of functions which in some cases result from configuration and/or interconnection of various structures when circuitry is powered and operating. 
       FIG. 1  shows a partial top view of a lead frame  100  formed as a panel or strip with interdigitated first and second columns  101  and  102 , respectively. The lead frame  100  includes a metal structure, such as copper, with prospective device portions arranged in rows along a first direction (e.g., the X direction in  FIG. 1 ), as well as columns along a second direction (e.g., the Y direction in  FIG. 1 ), where the first and second directions are perpendicular to one another. The lead frame is an interdigitated arrangement, in which respective device portions of the first columns  101  are offset or shifted along the second direction relative to the respective device portions of the second columns  102 . 
     The lead frame  100  has punch structures and stretch structures at respective ends of the first columns  101  according to one aspect. These features facilitate using sawing or other cutting operations to trim device leads of the interdigitated columns, followed by molding and saw cutting to separate packaged devices, without requiring lead trim dies for lead trimming. The punch and stretch structures facilitate moving the first columns  101  along the column direction after lead trimming and molding to align the previously offset lead portions of the first and second columns  101  and  102 . The lead frame  100  is an interdigitated configuration with device portions in each column  101  and  102  that include a respective die attach pad and lead portions with a pitch spacing distance  103 . The device portions and respective lead portions in the first and second columns  101  and  102  are offset or shifted relative to one another by a single pitch spacing distance  103 . In other examples, the offset is an integer number times the pitch spacing distance  103 , where the integer number is 2 or more. In other examples, the interdigitated column offset is not an integer multiple of the pitch spacing distance  103 . The lead frame  100  also includes several fixture alignment holes  106  to facilitate X, Y location of the lead frame  100  in a fixture or jig (not shown). 
     The respective first columns  101  have a first end  111  and a second end  112  spaced apart from the respective first end  111  along the second direction. The respective first columns  101  also include a punch structure  114  having a punch bar  115  that extends along the second direction from the first end  111  of a respective first column  101  to a first clamp portion  113  of the metal structure. The punch bar  115  is deformable along a third direction Z normal to a plane of the respective first and second directions X and Y (e.g., deformable into or out of the page in  FIG. 1 ). The illustrated punch structures  114  include a second punch bar  115  extending along the second direction Y from the first end  111  of the respective first column  101  to the first clamp portion  113  of the metal structure. Other examples include an integer number of one or more punch bars  115 . 
     The respective first columns  101  also include a stretch structure  116  that has a spring bar  117 . The respective first columns  101  have first device portions that individually include a respective first die attach pad  118  and respective first lead portions  119 . The spring bar  117  extends along an arcuate path from the second end  112  of a respective first column  101  to a second clamp portion  120  of the metal structure. The spring bar  117  is configured to extend along the second direction to allow movement of the respective first column  101  along the second direction Y toward the first clamp portion  113  of the metal structure. The spring bar  117  in the example of  FIG. 1  is configured to extend along the second direction toward the first clamp portion  113  by the pitch spacing distance  103  of the first lead portions  119  in response to deformation of the punch bar  115  by a punch depth dimension, as described further below in connection with  FIGS. 11-14 . The illustrated stretch structures  116  include a second spring bar  117  extending along a second arcuate path from the second end  112  of the respective first column  101  to the second clamp portion  120  of the metal structure. Other examples include an integer number of one or more spring bars  117 . In some examples, the respective spring bar  117  and the second spring bar  117  include first and second arcuate portions. In other examples, the spring bar or bars  117  include an integer number of one or more arcuate portions. 
     The respective second columns  102  have a first end  121  and a second end  122  that is spaced apart from the respective first end  121  along the second direction. The respective second columns  102  have second device portions that include a respective second die attach pad  128  and respective second lead portions  129 . The lead frame  100  of  FIG. 1  has alternating first columns  101  and second columns  102 , in which at least some of the first columns  101  are adjacent to one of the second columns  102 . In other examples, two or more second columns  102  can be adjacent to one another, with the individual first columns  101  adjacent to at least one of the second columns  102 . In the example of  FIG. 1 , prior to lead trimming, at least some of the first lead portions  119  of a given one of the first columns  101  are connected to a respective one of the second lead portions  129  of a second device portion of an adjacent one of the second columns  102 . 
     Referring now to  FIGS. 2-17 ,  FIG. 2  shows a method  200  for fabricating packaged electronic devices,  FIGS. 3-16  show the lead frame  100  of  FIG. 1  undergoing processing according to the method  200 , and  FIG. 17  shows a packaged electronic device according to another embodiment. The method  200  includes providing or creating a lead frame (e.g., lead frame  100 ) at  202 , attaching semiconductor dies to die attach pads of first and second columns of the lead frame at  204 , electrical connection processing at  206 , and enclosing the semiconductor dies of the columns  101  and  102  in respective first and second package structures at  208 . The method  200  further includes trimming the lead frame  100  at  210  to separate respective first and second lead portions (e.g.,  119  and  129 ) of adjacent ones of the first and second columns  101  and  102 . The method  200  also includes lead forming at  212 , moving the first columns at  214  along a column direction relative to the second columns, and package separation at  216  to separate individual packaged electronic devices of the respective first and second columns from one another and from the lead frame  100 . 
     At  202  in one example, the starting lead frame  100  is provided or created at  202  as a metal structure formed as an interdigitated strip having rows and respective first and second columns  101  and  102 , as well as respective punch structures and stretch structures  114  and  116  as shown in  FIG. 1  above. 
     The method  200  includes performing a die attach process at  204 .  FIG. 3  shows one example in which a die attach process  300  is performed that attaches first semiconductor dies  301  to respective first die attach pads  118  of first device portions of respective first columns  101  of the lead frame  100 . In this example, the first semiconductor dies  301  include conductive features, such as copper bond pads  311  on a top or upper side thereof. In addition, the die attach process  300  attaches second semiconductor dies  302  to respective second die attach pads  128  of second device portions of respective second columns  102  of the lead frame  100 . The second semiconductor dies  302  in  FIG. 3  include conductive features  312  on the top side thereof. One or both of the semiconductor dies  301  or  302  may include conductive features, such as solder bumps, copper pillars, etc. (not shown) that are electrically coupled to the respective die attach pads  118  and  128 , for example, using a flip chip die attach process  300 . In another example, the dies  301  and/or  302  are epoxied to the respective die attach pads  118  and  128  at  204 . 
     The method  200  continues at  206  with wire bonding or other electrical connection processing.  FIG. 4  shows one example, in which an electrical connection process  400  is performed, including wire bonding that electrically couples one or more of the first lead portions  119  to the respective conductive features  311  of the first semiconductor dies  301  of the first columns  101 . The process  400  also electrically couples one or more of the second lead portions  129  to the respective conductive feature  312  of the second semiconductor dies  302  of the second columns  102 . In one example, the electrical connection process  400  is performed while the lead portions  119  and  129  are connected to one another as shown in  FIG. 4 . The wire bonding process  400  connects first bond wires  401  between respective ones of the first lead portions  119  of the first columns  101  and respective conductive features  311  of the first semiconductor dies  301 . In addition, the wire bonding process  400  in this example connects second bond wires  402  between respective ones of the second lead portions  129  in the second columns  102  and respective conductive features  312  of the second semiconductor dies  302 . 
     The method  200  continues at  208  with a molding process that creates single molded package structures along each of the first and second columns  101  and  102 .  FIGS. 5 and 6  show one example in which a molding process  500  is performed that encloses the first semiconductor dies  301  of each respective first columns  101  in a single respective first package structure  501 . In addition, the molding process  500  encloses the second semiconductor dies  302  of each respective second column  102  in a single respective second package structure  502 . The process  500  uses a mold (not shown) with a single mold cavity with upper and lower portions that create tapered sides joined at a mold parting line with an upper first draft angle Θ 1  and a lower second draft angle Θ 2  as shown in  FIG. 5  to for each individual column  101  and  102 . In one example, the cavities associated with the first columns  101  are offset from the cavities associated with the second columns  102  along the second direction (Y) by the lead pitch dimension, to create the offset molded package structures  501  and  502  as shown in  FIG. 6 , although not a strict requirement of all possible implementations. 
     The method  200  continues at  210  with column direction lead trimming to separate the leads of adjacent columns.  FIGS. 7 and 8  show one example, in which a lead trimming process  700  is performed that uses a saw to cut through the lead frame  100  along trim lines  701  between adjacent pairs of the first and second columns  101  and  102 . The process  700  separates respective first and second lead portions  119  and  129  of adjacent ones of the first and second columns  101  and  102  which were previously joined in the starting lead frame  100  of  FIG. 1 . The process  700  in one example uses multiple cutting saw blades that cut along respective trim lines  701  concurrently. In another example, a single cutting blade is used to sequentially cut through designated portions of the lead frame  100  along the lines  701 . Another example uses a laser to cut through the designated portions of the lead frame  100  along the trim lines  701 . In the illustrated example, the trim lines  701  are parallel to one another and to the second direction, although not requirements of all possible implementations. 
     The method  200  continues at  212  with lead forming.  FIGS. 9 and 10  show one example, in which a lead forming process  900  is performed that forms the first and second lead portions  119  and  129  of the respective first and second columns  101  and  102  into gull wing shapes. In other examples, the first and second lead portions  119  and  129  are formed into different shapes, such as J leads, etc. 
     The method  200  continues at  214  with translating or moving the first columns  101  along the second direction relative to the second columns  102 .  FIGS. 11-14  illustrate one example, in which the first and second clamp portions  113  and  120  are clamped by clamping apparatus or other features of a fixture on which the lead frame  100  is installed ( FIGS. 11 and 12 ), and a punch is actuated ( FIGS. 13 and 14 ) along the third direction (e.g., the Z direction in  FIGS. 11 and 13 ) to deform the punch bar  115 .  FIG. 11  shows a section view of a portion of the lead frame  100  proximate the first end  111  of one of the first columns  101  taken along line  11 - 11  of  FIG. 12 . A first clamp  1101  engages a top side of the upper edge of the lead frame  100  as shown in  FIGS. 11 and 12 , and a lower clamp  1102  engages the bottom side of the lead frame  100  to hold the edge of the lead frame  100  stationary as shown in  FIG. 11 . A lower die  1104  ( FIG. 11 ) engages a bottom portion of a section of the punch bar  115 , leaving a gap between the lower die  1104  and the lower clamp  1102 . A punch  1106  is positioned in  FIG. 11  above the top side of the punch bar  115  in a position over the gap between the lower die  1104  and the lower clamp  1102 . As further shown in  FIG. 12 , a second clamp  1202  engages a top side of the bottom edge of the lead frame  100 . Similar clamping and punch die features are provided at the ends of each of the individual first columns  101  as shown in  FIG. 12 . 
       FIGS. 13 and 14  show an example, in which a punch process  1300  is performed that moves the punch  1106  downward (e.g., along the third direction “Z” in  FIG. 13 ) normal to the X-Y plane of the respective first and second directions to deform the punch bars  115  proximate first ends  111  of the respective first columns  101 . The Z direction deformation of the punch bars  115  by a punch depth dimension PD ( FIG. 13 ) moves the first columns  101  along the second direction relative to the second columns  102  by the pitch spacing distance  103  of the first lead portions  119  (e.g., upward along the direction of the arrows in  FIG. 14 ). 
     The movement of the first columns  101  along the second direction extends the spring bars  117  of the first columns  101  along the second direction as shown in  FIG. 14 . In one example, the punch  1106  is translated along the Z direction by an automated servo system (not shown). In another example, the punch  1106  is manually actuated. In one example, the punch depth dimension PD and the resulting Z direction movement of the punch  1106  are tailored according to the pitch spacing distance  103  or any other desired amount of Y direction movement of the first columns  101  relative to the second columns  102 , as well as according to the thickness and material of the lead frame  100 . 
     The method  200  continues at  216  with row direction cutting to separate the individual packaged electronic devices. The cutting at  216  also creates molded package and with a zero draft angle.  FIGS. 15 and 16  show one example, in which a sawing process  1500  is performed along cut lines  1501  to separate individual device portions of the column-length molded structures, and to create first and second ends  1502  and  1503 , respectively, for individual packaged electronic devices  1511  and  1512  of the respective first and second columns  101  and  102 . The sawing process  1500  separates individual packaged electronic devices  1511 ,  1512  of the respective first and second columns  101  and  102  from one another. In another example, the packaged electronic devices  1511  and  1512  are separated from one another and from the lead frame  100  using a different cutting technique, such as laser cutting. Because the columns  101  and  102  were previously aligned by the punch operation at  214 , the cut lines  1501  extend between the first device portions of the respective first columns  101  and between the second device portions of the respective second columns  102 . In this example, the cut lines  1501  are parallel to the first direction, although not a requirement of all possible implementations. 
     The method  200  and the inclusion of the punch structures  114  and stretch structures  116  facilitate improved lead frame strip device density through interdigitated starting lead frame configurations (e.g., lead frame  100 ), while allowing cutting operations for lead trimming as well as device separation, and without requiring multiple trim and form die sets to accommodate multiple lead count and package sizes during integrated circuit manufacturing. The package saw cutting at  216  can be easily adapted to different lead frame configurations by changing a saw equipment recipe or programming, without requiring multiple tooling sets (e.g., punch die sets) to accommodate multiple lead counts. In one example, a jig (not shown) is used for manual pressing of the punch  1106  such that the Y direction translation of the first columns  101  provides accurate and repeatable pitch correction according to the punch depth PD, where the jig includes a handle, a hinge punch stopper, a track, and a jig base (not shown). The spring bar  117  in the example of  FIG. 1  is configured to extend along the second direction toward the first clamp portion  113  by the pitch spacing distance  103  of the first lead portions  119  in response to deformation of the punch bar  115  by the punch depth dimension PD as shown in  FIGS. 13 and 14 . 
       FIG. 17  shows a perspective view of an example packaged electronic device  1511  (e.g., an integrated circuit or IC) produced by the method  200  of  FIG. 2  using the starting lead frame  100  of  FIG. 1 . The electronic device  1511  includes the molded package structure  501  with a first side  1701 , an opposite second side  1702  spaced apart from the first side  1701  along the first direction (X), as well as the first end  1502  and the second end  1503  spaced apart from the first end  1502  along the second direction (Y). The electronic device  1511  also includes a top  1706  and a bottom  1708  spaced apart from the top  1706  along the third direction (Z). The electronic device  1511  in this example includes the semiconductor die  301  (e.g.,  FIG. 4  above) enclosed by the molded package structure  501 , as well as first conductive leads  119  along the first side  1701  and second conductive leads  119  along the second side  1702  of the package structure  501 . The leads  119  have the pitch spacing  103  as previously discussed. In one example, one or more of the first conductive leads  119  is/are electrically coupled to the semiconductor die  301  and one or more of the second conductive leads  119  is/are electrically coupled to the semiconductor die  301  (e.g., via bond wires  401  shown in  FIG. 4 ). 
     The sawing process used to separate the packaged electronic devices  1511  and  1512  creates planar first and second ends  1502  are  1503  as shown in  FIG. 17 . In one example, the individual first and second sides  1701  and  1702  each include a first portion  1711  that extends from the top  1706  to a mold parting line  1704  at a non-zero first angle Θ1 to the Y-Z plane of the second and third directions. In addition, the individual first and second sides  1701  and  1702  include a second portion  1712  that extends from the bottom  1708  to the mold parting line  1704  at a second non-zero angle Θ2 to the Y-Z plane. In one example, the first and second angles are equal (e.g., Θ1=Θ2), although not a strict requirement of all possible implementations. 
     The stretch structures  116  and associated spring bars  117  at the second ends  112  of the first columns  101  in  FIG. 1  provide a single yield point design that is good for manufacturability.  FIGS. 1 and 10  show the spring bars  117  before punch actuation, and  FIG. 14  shows the stretched spring bars  117  moved 0.409 inches in response to punch actuation to a punch depth PD ( FIG. 13 ) of 0.032 inches. In certain examples, the spring bar  117  has a single arcuate portion. In other examples, the spring bar  117  has multiple arcuate portions. Different implementations have one or more yield locations for the individual spring bars  117 . 
       FIGS. 18-35  show different example implementations of the spring bars and stretch structures proximately the second ends  112  of the first columns  101 . These examples include the lead portions  119  and  129 , the alignment holes  106 , the molded package structures  501  and  502 , and lower clamps  1202  as previously described. 
       FIGS. 18 and 19  show partial top views of a lead frame  1800  with interdigitated columns as previously described.  FIGS. 18 and 19  show another embodiment of stretch structures  1816  and associated spring bars  1817  at the second ends  112  of the odd-numbered columns.  FIG. 18  shows the lead frame  1800  in interdigitated form prior to stretching, and  FIG. 19  shows the lead frame  1800  after the first columns have been moved upward along the second (e.g., Y) direction. In this example, the punch depth PD of 0.025 inches and a second direction movement of 0.397 inches. 
       FIGS. 20 and 21  show partial top views of a lead frame  2000  with interdigitated columns as previously described.  FIGS. 20 and 21  show another embodiment of stretch structures  2016  and associated spring bars  2017  at the second ends  112  of the odd-numbered columns.  FIG. 20  shows the lead frame  2000  in interdigitated form prior to stretching, and  FIG. 21  shows the lead frame  2000  after the first columns have been moved upward along the second (e.g., Y) direction. In this example, the punch depth PD of 0.022 inches and a second direction movement of 0.431 inches. 
       FIGS. 22 and 23  show partial top views of a lead frame  2200  with interdigitated columns as previously described.  FIGS. 22 and 23  show another embodiment of stretch structures  2216  and associated spring bars  2217  at the second ends  112  of the odd-numbered columns.  FIG. 22  shows the lead frame  2200  prior to stretching, and  FIG. 23  shows the lead frame  2200  after the first columns have been moved upward along the second direction, with a punch depth PD of 0.020 inches and a second direction movement of 0.412 inches. 
       FIGS. 24 and 25  show partial top views of a lead frame  2400  with interdigitated columns as previously described.  FIGS. 24 and 25  show another embodiment of stretch structures  2416  and associated spring bars  2417  at the second ends  112  of the odd-numbered columns.  FIG. 24  shows the lead frame  2400  prior to stretching, and  FIG. 25  shows the lead frame  2400  after the first columns have been moved upward with a punch depth PD of 0.020 inches and a second direction movement of 0.047 inches. 
       FIGS. 26 and 27  show partial top views of a lead frame  2600  with interdigitated columns as previously described.  FIGS. 26 and 27  show another embodiment of stretch structures  2616  and associated spring bars  2617  at the second ends  112  of the odd-numbered columns.  FIG. 26  shows the lead frame  2600  prior to stretching, and  FIG. 27  shows the lead frame  2600  after the first columns have been moved upward with a punch depth PD of 0.118 inches and a second direction movement of 0.046 inches. 
       FIGS. 28 and 29  show partial top views of a lead frame  2800  with interdigitated columns as previously described.  FIGS. 28 and 29  show another embodiment of stretch structures  2816  and associated spring bars  2817  at the second ends  112  of the odd-numbered columns.  FIG. 28  shows the lead frame  2800  prior to stretching, and  FIG. 29  shows the lead frame  2800  after the first columns have been moved upward with a punch depth PD of 0.023 inches and a second direction movement of 0.400 inches. 
       FIGS. 30 and 31  show partial top views of a lead frame  3000  with interdigitated columns as previously described.  FIGS. 30 and 31  show another embodiment of stretch structures  3016  and associated spring bars  3017  at the second ends  112  of the odd-numbered columns.  FIG. 30  shows the lead frame  3000  prior to stretching, and  FIG. 31  shows the lead frame  3000  after the first columns have been moved upward with a punch depth PD of 0.023 inches and a second direction movement of 0.454 inches. 
       FIGS. 32 and 33  show partial top views of a lead frame  3200  with interdigitated columns as previously described.  FIGS. 32 and 33  show another embodiment of stretch structures  3216  and associated spring bars  3217  at the second ends  112  of the odd-numbered columns.  FIG. 32  shows the lead frame  3200  prior to stretching, and  FIG. 33  shows the lead frame  3200  after the first columns have been moved upward with a punch depth PD of 0.042 inches and a second direction movement of 0.011 inches. 
       FIGS. 34 and 35  show partial top views of a lead frame  3400  with interdigitated columns as previously described.  FIGS. 34 and 35  show another embodiment of stretch structures  3416  and associated spring bars  3417  at the second ends  112  of the odd-numbered columns.  FIG. 34  shows the lead frame  3400  prior to stretching, and  FIG. 35  shows the lead frame  3500  after the first columns have been moved upward with a punch depth PD of 0.036 inches and a second direction movement of 0.421 inches. 
     The designs of  FIGS. 1, 22-23, 32-33 and 28-29  give comparable pitch correction result with the spring bars  1817  of  FIGS. 18 and 19 . The designs of  FIGS. 20-21, 24-25, 26-27, 30-31 and 34-35  give higher value of pitch correction along the second direction. 
     The above examples are merely illustrative of several possible implementations of various aspects of the present disclosure, wherein equivalent alterations and/or modifications will occur to others skilled in the art upon reading and understanding this specification and the annexed drawings. Modifications are possible in the described examples, and other implementations are possible, within the scope of the claims.