Abstract:
A system for fabricating semiconductor components includes mating mold cavity plates having mold cavities configured to mold body segments of the semiconductor components on either side of a leadframe. The mold cavity plates also include runners configured to direct molding compound between the mold cavities and into the corners of the mold cavities. The runners prevent trapped air from accumulating in the corners of the mold cavities, and eliminate the need for air vents in the corners. The mold cavity plates also include dummy mold cavities configured to form dummy segments on the leadframe, and air vents in flow communication with the dummy segments. The dummy mold cavities are configured to collect trapped air, and to direct the trapped air through the air vents to atmosphere. Each dummy mold cavity has only a single associated air vent, such that cleaning is facilitated, and flash particles from the air vents are reduced. A method for fabricating semiconductor components includes a molding step performed using the system. A semiconductor component fabricated using the system includes the leadframe, a die, upper and lower body segments encapsulating the die, and dummy segments on the leadframe.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to semiconductor packaging. More particularly, this invention relates to a system and to a method for fabricating semiconductor packages using mold cavities having runners configured to minimize venting. 
     BACKGROUND OF THE INVENTION 
     Semiconductor packages typically include a semiconductor die encapsulated in a molded plastic body. The molded plastic body rigidifies and protects the die from the environment. Semiconductor packages also include a substrate, such as a leadframe, or a circuit board material, on which the die is mounted. The substrate includes conductors such as lead fingers for a leadframe, or conductive traces for a circuit board substrate which provide internal signal, power and ground paths through the package body to the die. The package also includes terminal contacts, such a metal leads, or solder balls, for making electrical connections from the outside to the package. 
     The molded plastic body can be formed using a transfer molding process. During this process a mold cavity is placed on the substrate and over the die, and a molding compound, such as an epoxy resin, is injected into the mold cavity. The molding compound can be injected on either side of the substrate to encapsulate the die and associated wire bonds. 
     A prior art transfer molding process is illustrated in  FIG. 1 . In this example the substrate comprises a metal leadframe  10 .  FIG. 1  illustrates only a portion of the leadframe  10 , which includes multiple semiconductor dice  12  mounted in pairs across the width of the leadframe  10 . The leadframe  10  is an elongated member configured to fabricate multiple semiconductor packages  14 . Each package  14  includes a molded plastic body  28  which encapsulates a die  12 , and opposing surfaces on a portion of the leadframe  10 . 
     The leadframe  10  includes openings  16 A,  16 B,  16 C along longitudinal edges thereof, which facilitate handling by automated equipment such as conveyor tracks, magazines and loaders. The openings  16 A,  16 B,  16 C also function to align the leadframe  10  on various process systems such as die attachers, wire bonders, molding systems, and singulation systems. The leadframe  10  also includes transverse thermal expansion slots  18  and leadfingers  20  that are wire bonded to bond pads (not shown) on the dice  12 . The leadfingers  20  are connected by bus bars  22 , and will subsequently be trimmed and formed into the terminal leads for the packages  14 . Further, the leadframe  10  includes a molding slot  24  which facilitates the flow of a molding compound  26  during molding of the plastic bodies  28 . 
     As illustrated by the flow arrows  30 , during the molding process the molding compound  26  is injected across the width of the leadframe  10  from left to right in  FIG. 1 . A system for performing the molding process includes mold cavities (not shown) clamped to the opposing surfaces of the leadframe  10 . During the molding process, trapped air bubbles  36  in the molding compound  26  can be released to a dummy mold cavity (not shown) which forms dummy segments  38  on the opposing surfaces of the leadframe  10 . However, some of the air is trapped at the corners of the mold cavities, proximate to the corners  32  of the molded plastic bodies  28 . The trapped air requires that the molding system includes air vents  34  (indicated by dotted lines) in flow communication with the mold cavities proximate to the corners  32  of the molded plastic bodies  30 . 
     One problem with the prior art molding system is that the air vents  34  will typically fill with molding compound  26  during normal production. At given intervals the air vents  34  must be cleaned, which requires that any molding compound  26 , and also any cleaning compound in the air vents  34 , be scrapped out and removed. In view of the large number of air vents  34  in a molding system and their small size, the cleaning process takes time, and adversely affects the productivity of the molding system. 
     Another problem with the air vents  34  is the excess molding compound which forms in the air vents  34 . This excess molding compound is sometimes referred to as mold “flash”. The flash fills the air vents  34  causing blockage and defective packages  14 . In addition, small pieces of flash can break loose from the air vents and stick to the leadframe  10 . The pieces of flash can cause shorting in the completed packages  14 , and can also accumulate on various process equipment, such as conveyor tracks, causing additional problems. Often times the flash pieces are charged such that they are attracted to metal surfaces. 
     The present invention is directed to a system and to a method for molding semiconductor components in which additional runners are employed to channel the molding compound through corners of the mold cavities that must normally be vented. This eliminates a large number of air vents, and alleviates the cleaning and flash accumulation problems associated with the air vents. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, an improved system for fabricating semiconductor components, an improved method for fabricating semiconductor components, and improved semiconductor components fabricated using the system and the method are provided. 
     In an illustrative embodiment, the system and the method are used to fabricate plastic semiconductor packages on a metal leadframe. The leadframe is configured to support semiconductor dice in pairs two abreast for molding. In addition, the leadframe includes leadfingers wire bonded to the dice, and configured to form the internal and external leads for the packages. 
     The system includes an upper mold cavity plate having a plurality of upper mold cavities, and a lower mold cavity plate having a plurality of lower mold cavities. The upper mold cavity and the lower mold cavity are configured to engage opposing surfaces of the leadframe, and to mold the plastic packages onto the leadframe. In addition, each mold cavity plate includes corner runners configured to channel molding compound through the corners of the mold cavities, and into dummy cavities on opposing surfaces of the leadframe. The flow of molding compound through the corners prevents trapped air from accumulating in the corners. Each dummy cavity is in flow communication with a single air vent, and any trapped air in the molding compound is channeled through the dummy mold cavities and into the air vents. The runners eliminate the corner air vents of the prior art molding system such that there are fewer air vents to clean and less flash particles are produced. 
     The method includes the step of providing the upper mold cavity and the lower mold cavity with the mold cavities, the runners, the dummy cavities and the air vents. The method also includes the steps of injecting the molding compound into the mold cavities, and directing the molding compound proximate to the corners of the mold cavities using the runners. In addition, the method includes the step of directing trapped air through the runners into the dummy mold cavities, and then out the air vents. 
     Each semiconductor package includes a semiconductor die, and upper and lower body segments encapsulating the die and a portion of the leadframe. Prior to singulation of the packages, the leadframe includes upper dummy segments and lower dummy segments on upper and lower surfaces thereof proximate to an edge of the leadframe. The leadframe also includes a connecting dummy segment on the lower surface thereof between adjacent pairs of packages. In addition, the leadframe includes second dummy segments on the lower surface thereof connected to the lower dummy segments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross sectional view illustrating a prior art method for molding a semiconductor package using multiple vents located proximate to the corners of the package; 
         FIGS. 2A–2D  are schematic cross sectional views illustrating a system constructed in accordance with the invention, and steps in a method for fabricating semiconductor packages in accordance with the invention; 
         FIG. 3A  is a bottom view of an upper mold cavity plate of the system taken along line  3 A— 3 A of  FIG. 2A ; 
         FIG. 3B  is a side elevation view of the upper mold cavity plate; 
         FIG. 3C  is an enlarged view of a portion of the upper mold cavity plate taken along dotted segment  3 C of  FIG. 3A  illustrating upper mold cavities on the upper mold cavity plate; 
         FIG. 3D  is a side elevation view of the upper mold cavities; 
         FIG. 3E  is an enlarged view of a portion of the upper mold cavity plate taken along dotted segment  3 E of  FIG. 3A  illustrating a dummy mold cavity on the upper mold cavity plate; 
         FIG. 3F  is a side elevation view of the dummy mold cavity; 
         FIG. 3G  is an end view of the dummy mold cavity; 
         FIG. 4A  is a plan view of a lower mold cavity plate of the system taken along line  4 A— 4 A of  FIG. 2A ; 
         FIG. 4B  is a side elevation view of the lower mold cavity plate; 
         FIG. 4C  is an enlarged view of a portion of the lower mold cavity plate taken along dotted segment  4 C of  FIG. 4A  illustrating lower mold cavities on the lower mold cavity plate; 
         FIG. 4D  is a side elevation view of a lower mold cavity; 
         FIG. 4E  is an enlarged view of a portion of the lower mold cavity plate taken along dotted segment  4 E of  FIG. 4C  illustrating a connecting dummy cavity on the lower mold cavity plate; 
         FIG. 4F  is a side elevation view of the connecting dummy cavity; 
         FIG. 4G  is an end elevation view of the connecting dummy cavity; 
         FIG. 4H  is an enlarged view of a portion of the lower mold cavity plate taken along dotted segment  4 H of  FIG. 4C  illustrating a dummy mold cavity on the lower mold cavity plate; 
         FIG. 4I  is an end elevation view of the dummy mold cavity; 
         FIG. 4J  is a side elevation view of the dummy mold cavity; 
         FIG. 5  is an enlarged plan view taken along line  5 — 5  of  FIG. 2B  illustrating a leadframe configured for constructing packages in accordance with the invention; 
         FIG. 6  is a cross sectional view taken along section line  6 — 6  of  FIG. 2C  illustrating a flow of a molding compound on an upper surface of the leadframe during a molding step; 
         FIG. 7A  is a plan view taken along line  7 A— 7 A of  FIG. 2D  illustrating semiconductor packages on the leadframe constructed using the system and method of the invention; and 
         FIG. 7B  is a side elevation view of the semiconductor packages on the leadframe. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 2A–2D , a system  40  for fabricating semiconductor components, and steps in a method for fabricating the semiconductor components using the system  40  are illustrated. In the illustrative embodiment, the components comprise semiconductor packages  52  ( FIG. 2D ) having a TSOP (thin small outline package) configuration. However, it is to be understood that the system  40 , and the method, can be used to fabricate other types of semiconductor components, such as chip scale packages, BGA devices, multi chip modules and other types of plastic packages (e.g., DIPs, SIPs etc.). 
     Referring to  FIG. 2A , the system  40  includes a transfer molding apparatus  58 . One suitable transfer molding apparatus  58  is manufactured by ASAHI Engineering Company of Japan and is designated a “COSMO” model. 
     The system  40  also includes an upper mold cavity plate  42 U, and a lower mold cavity plate  42 L. The upper mold cavity plate  42 U and the lower mold cavity plate  42 L are movable by the transfer molding apparatus  58  between an open position ( FIG. 2A ), and a closed position ( FIG. 2C ). However, as is apparent the “upper” and “lower” terminology is for illustrative purposes, and would change according to the orientation of the system  40 . Accordingly, the claims to follow refer generically to “a first mold cavity plate” (i.e., upper mold cavity plate  42 U) and to “a second mold cavity plate” (i.e., lower mold cavity plate  42 L). 
     Referring to  FIG. 2B , for performing a molding step of the method, a leadframe  46  is placed between the upper mold cavity plate  42 U and the lower mold cavity plate  42 L. The transfer molding apparatus  58  can include suitable mechanisms (not shown) for placing and aligning the leadframe  46  between the mold cavity plates  42 U,  42 L. However, prior to the molding step, a plurality of semiconductor dice  56  ( FIG. 5 ) are attached to the leadframe  46 . The leadframe  46  includes an upper surface  47 U on which the dice are mounted, and a lower surface  47 L. In addition, as shown in  FIG. 5 , the leadframe  46  includes a plurality of lead fingers  60 , and the dice  56  are wire bonded to the lead fingers  60 . The leadframe  46  can also include a plurality of mounting paddles (not shown) for supporting the dice  56 . 
     As shown in  FIG. 5 , the lead fingers  60  are initially connected by a bus bar  62 , but following a trim and form step, will become the external leads for the semiconductor packages  52 . As also shown in  FIG. 5 , the leadframe  46  includes handling openings  68 A,  68 B,  68 C, and thermal expansion slots  66  that function substantially as previously described. In addition, the leadframe  46  includes mold inlet openings  64 , connecting segment openings  70 , and dummy segment openings  72  configured to facilitate the flow of the molding compound  50  and the formation of the molded features on the leadframe  46 . 
     Referring to  FIG. 2C , during the molding step, the upper mold cavity plate  42 U and the lower mold cavity plate  42 L are clamped by the transfer molding apparatus  58  to the upper surface  47 U and the lower surface  47 L of the leadframe  46 . As also shown in  FIG. 2C , the system  40  includes a molding compound source  48  configured to inject a molding compound  50  ( FIG. 6 ) under pressure between the upper mold cavity plate  42 U and the lower mold cavity plate  42 L. The flow of the molding compound  50  ( FIG. 6 ) during the molding step will be more fully explained as the description proceeds. Also during the molding step, air is vented from the upper mold cavity plate  42 U and the lower mold cavity plate  42 L through upper air vents  84 U, and lower air vents  84 L as indicated by air flow arrow  54 . Although there are a plurality of air vents  84 U,  84 L, a single upper air vent  84 U and a single lower air vent  84 L is associated with each pair of packages  52  on the leadframe  46 . 
     Referring to  FIG. 2D , following the molding step the leadframe  46  includes a plurality of semiconductor packages  52 . The leadframe  46  with the semiconductor packages  52  thereon is also shown in  FIGS. 7A and 7B . Each semiconductor package  52  includes an upper body segment  74  and a lower body segment  76 , having matching thicknesses and peripheral outlines. However, it is to be understood that the invention can also be practiced to form a molded body segment on only one side of a semiconductor component, or to form a component having asymmetrical molded body segments. 
     As also shown in  FIG. 2D , the leadframe  46  includes upper dummy segments  80  and lower dummy segments  82  located proximate to a right lateral edge  98  of the leadframe  46 . In addition, the leadframe  46  includes connecting dummy segments  78  located between adjacent semiconductor packages  52 . The structure and function of the dummy segments  78 ,  80 ,  82  will be more fully explained as the description proceeds. 
     Referring to  FIGS. 3A–3D , the upper mold cavity plate  42 U is illustrated. The upper mold cavity plate  42 U is preferably machined out of a single block of a metal, such as stainless steel. As shown in  FIG. 3A , the upper mold cavity plate  42 U has a generally rectangular peripheral shape which corresponds to, but is slightly larger than the rectangular peripheral shape of the leadframe  46 . 
     As also shown in  FIG. 3A , the upper mold cavity plate  42 U includes a plurality of upper mold cavities  86 U, which are arranged in pairs corresponding to the locations of the semiconductor dice  56  ( FIG. 5 ) on the leadframe  46 . The upper mold cavities  86 U are configured to mold the upper body segments  74  ( FIG. 2D ) of the packages  52  ( FIG. 2D ). The upper mold cavity plate  42 U also includes upper dummy mold cavities  102 U configured to mold the upper dummy segments  80  ( FIG. 2D ) on the leadframe  46 . 
     As shown in  FIG. 3B , the upper mold cavity plate  42 U also includes handling recesses  88 U on opposing sides thereof. In addition the upper mold cavity plate  42 U includes stepped surfaces  90 U on opposing ends thereof. 
     As shown in  FIG. 3C , the upper mold cavity plate  42 U also includes openings  92 U in the upper mold cavities  86 U configured to receive knockout pins for pushing the semiconductor packages  52  ( FIG. 2D ) out of the upper mold cavities  86 U. In addition, the upper mold cavity plate  42 U includes through holed openings  94 U configured to for use with associated ejector pins for ejecting the leadframe  46 . 
     As also shown in  FIG. 3C , the upper mold cavity plate  42 U includes inlet runners  96 U configured to receive the molding compound  50  ( FIG. 6 ) from the molding compound source  48  ( FIG. 2C ), and to direct the molding compound  50  into the upper mold cavities  86 U. In addition, the upper mold cavity plate  42 U includes connecting runners  100 U configured to direct the molding compound  50  between adjacent pairs of upper mold cavities  86 U. Further, the upper mold cavity plate  42 U includes corner runners  106 U configured to direct the molding compound  50  into the corners  108 U of the upper mold cavities  86 U. As will be further explained, the corner runners  106 U prevent air from being trapped in the corners  108 U of the upper mold cavities  86 U, and allow the air vents  34  ( FIG. 1 ) of the prior art system to be eliminated. In addition, the corner runners  106  improve the construction of the packages  52  because the corners thereof do not include trapped air. 
     As shown in  FIG. 3C , the upper mold cavity plate  42 U also includes dummy runners  110 U configured to direct the molding compound  50  from the upper mold cavities  86 U into the dummy cavities  102 U. In addition, the upper mold cavity plate  42 U includes the upper air vents  84 U configured to vent air from the dummy mold cavities  102 U to atmosphere. Each pair of upper mold cavities  86 U has a single upper air vent  84 U associated therewith. However, all of the air vents  84 U are in flow communication and vent to atmosphere. 
     During the molding step, the inlet runners  96 U, the corner runners  106 U, the connecting runners  100 U, and the dummy runners  110 U, in combination with the upper surface  47 U ( FIG. 2B ) of the leadframe  46 , form closed conduits for channeling the flow of the molding compound  50  over the upper surface  47 U of the leadframe  46 . 
     Still referring to  FIG. 3C , the upper mold cavities  86 U include peripheral lips  104 U which are also known as “clamping surfaces” which are configured to engage the upper surface  47 U of the lead frame  46 . The peripheral lips  104 L are the highest surfaces on the upper mold cavity plate  42 U and sealingly engage the upper surface  47 U of the lead frame  46  for forming the upper body segments  74  of the packages  52 . In addition, the peripheral lips  104 U space the runners  96 U,  106 U,  100 U,  110 U from the upper surface  47 U of the leadframe  46  such that the molding compound  50  can flow between the runners  96 U,  106 U,  100 U,  110 U and the upper surface  47 U of the leadframe  46 . 
     One method for fabricating the peripheral lips  104 L is to EDM (electric discharge machine) the cross hatched area  112 U which surrounds the peripheral lips  104 L to a selected depth. By way of example, this cross hatched area  112 U can be EDMed to a depth measured from the surfaces of the peripheral lips  104 L of about 1.01 to 1.78 mm. Similarly, the inlet runners  96 U, the corner runners  106 U, the connecting runners  100 U, the dummy runners  110 U and the air vents  84 U can be EDMed to selected depths with respect to the surfaces of the peripheral lips  104 L. By way of example, the depth of the inlet runners  96 U, the connecting runners  100 U and the dummy runners  110 U can be about 0.005–0.008 mm. The depth of the corner runners  106 U and the air vents  84 U can be about 0.025 mm. In  FIG. 3C , areas that have the same depth are cross hatched with the same section lines. 
       FIG. 3D  illustrates the depth of the upper mold cavities  86 U which is about 10 times greater than the depths of the runners  96 U,  106 U,  100 U,  110 U listed above. Accordingly, for simplicity  FIG. 3D  does not illustrate the depth of the runners  96 U,  106 U,  100 U,  110 U or the height of the peripheral lips  104 U relative to the runners. By way of example, the upper mold cavities  86 U can be EDMed to a depth of about 0.445 mm. In addition, the upper mold cavities  86 U can have a length of about 18.40 mm and a width of about 14.000 mm. The inlet runners  96 U can have a width of about 5.00 mm. The corner runners  106 U can have a length of about 4.00 mm, and a width of about 0.8 mm. The peripheral lips  104 U can have a width of about 0.8 mm. 
     Referring to  FIGS. 3E–3G , a dummy mold cavity  102 U and associated air vent  84 U are illustrated. The dummy mold cavities  102 U can have a depth of about 0.445 mm, a length of about 7.20 mm and a width of about 1.30 mm. However, as is apparent, all of the dimensions given above are merely exemplary, and can be adjusted as required by the skilled artisan. 
     Referring to  FIGS. 4A–4I , the lower mold cavity plate  42 L is shown. The lower mold cavity plate  42 L is constructed substantially in a mirror image of the upper mold cavity plate  42 U. In addition, the lower mold cavity plate  42 L has the same size and shape as the upper mold cavity plate  42 U includes the same stepped surfaces  90 L as opposing ends. In addition, the lower mold cavity plate  42 L includes lower mold cavities  86 L having peripheral lips  104 L ( FIG. 4C ) configured to sealingly engage the lower surface  47 L of the leadframe  46 . The lower mold cavities  86 L and the upper mold cavities  86 U form enclosed spaces which substantially determine the size and shape of the semiconductor packages  52  ( FIG. 2D ). The peripheral lips  104 U of the lower mold cavities  86 L are defined by EDMed surface  112 L. The lower mold cavity plate  42 L also includes openings  92 L for knock out pins. 
     The lower mold cavity plate  42 L also includes inlet runners  96 L, corner runners  106 L, connecting runners  106 L, dummy runners  110 L, dummy mold cavities  102 L and air vents  84 L. These elements are constructed substantially as mirror images of the equivalent elements contained on the upper mold cavity plate  42 U. However, there are some differences between these elements. Specifically, as shown in  FIG. 4C , the inlet runners  96 L include faceted surfaces. 
     In addition, as shown in  FIGS. 4E–4G , the connecting runners  100 L include a connecting dummy cavity  114 L, configured to form the connecting dummy segment  78  ( FIG. 2D ) between the packages  52 . As shown in  FIG. 4E , the connecting dummy cavity  114 L is generally circular in shape with faceted surrounding surfaces. Further, as shown in  FIGS. 4H–4I , the dummy runners  110 L include a second dummy cavity  116 L configured to form a second lower dummy segment  118  ( FIG. 2D ) on the leadframe  46 . As shown in  FIG. 4H , the second dummy cavity  116 L is generally circular in shape with faceted surrounding surfaces. 
     Referring to  FIG. 6 , the flow of the molding compound  50  over the upper surface  47 U of the leadframe  46  during the molding step is illustrated. As indicated by flow arrows  120 , the molding compound  50  enters the inlet runners  96 U and is directed into the upper mold cavities  86 U ( FIG. 3C ). In general, the flow of the molding compound  50  is from left to right in  FIG. 6 , from the left lateral edge  99  of the leadframe  46  towards the right lateral edge  98  of the leadframe  46 . However, as is apparent the “right” and “left” terminology is for illustrative purposes, and would change according to the orientation of the leadframe  46 . Accordingly the claims to follow refer generically to a “first edge” (i.e., left lateral edge  99 ) and to a “second edge” (i.e., right lateral edge  98 ). 
     The corner runners  106 U also direct the molding compound  50  proximate to the corners  108 U ( FIG. 3C ) of the upper mold cavities  86 U such that the corners  124  of the packages  52  do not include voids and trapped air  120 . Each corner  124  includes orthogonal surfaces such that the corner runners  106 U direct the flow of the molding compound  50  through the corner  124  in a direction generally perpendicular to one corner surface and generally parallel to the other corner surface. With the corner runners  106 U directing the flow of the molding compound through the corners  124 , there is no need to vent the corners  108 U ( FIG. 3C ) of the upper mold cavities  86 U. 
     In the illustrative embodiment the corner runners  106  are configured to initially direct the molding compound  50  along outside edges of the upper mold cavities  86 U on the left lateral edge  99  of the leadframe  46  in a flow direction generally perpendicular to the flow of the molding compound through the inlet runners  96 U. In addition, the corner runners  106 U are configured to turn the flow direction of the molding compound approximately 90° such that the molding compound  50  enters the corners  108 U of the upper mold cavities  86 U on the left lateral edge  99  of the leadframe  46  in a flow direction that is generally parallel to the flow direction through the inlet runners  96 U. 
     The molding compound  50  is also directed through the connecting runners  100 U into the adjacent mold cavities  86 U. The flow direction through the connecting runners  100 U is generally parallel to the flow direction through the inlet runners  96 U. The corner runners  106 U are configured to turn the molding compound  50  exiting the upper mold cavities  86 U on the left lateral edge  99  of the leadframe  46  approximately 90° and towards the connecting runners  100 U, then 180° and away from the connecting runners  100 U. 
     The molding compound  50  is also directed through the dummy runners  110 U and into the dummy mold cavity  102 U. Any trapped air  122  is also directed into the dummy mold cavity  102 U and is vented through the air vent  84 U to atmosphere. The corner runners  106 U are configured to turn the molding compound  50  exiting the upper mold cavities  86 U on the right lateral edge  99  of the leadframe  46  approximately 90°, and to direct the molding compound towards the dummy runners  110 U. The corner runners  106 U then turn the flow of the molding compound approximately 90° in a direction generally parallel to the flow direction through the dummy runners  110 U and the dummy mold cavities  102 U. 
     The flow of the molding compound over the lower surface  47 L ( FIG. 2C ) of the leadframe  46  is substantially the same as described above, except the connecting dummy segment  78  ( FIG. 2C ) and the second lower dummy segment  118  ( FIG. 2C ) are also formed and function as package to package runners. 
     Thus the invention provides a system and a method for fabricating semiconductor components, and improved semiconductor components fabricated using the system and the method. While the invention has been described with reference to certain preferred embodiments, as will be apparent to those skilled in the art, certain changes and modifications can be made without departing from the scope of the invention as defined by the following claims.