Patent Abstract:
In accordance with the present invention, there is provided a CPV package which comprises a leadframe assembly, such leadframe assembly including multiple frames stacked on top of each other. A top frame of the leadframe assembly provides the electrical interconnect between the top or front surface of the receiver die and the bypass diode required to complete the circuit. The top frame also provides hook up wire interconnect pads for the completed CPV package. An exposed bottom surface of a bottom frame of the leadframe assembly defines a heat spreader which assists in thermal management. The fabrication of the CPV package to include multiple frames stacked on top of each other provides high thermal dissipation and high voltage isolation, while at the same providing a high level of reliability with a comparatively low manufacturing cost.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention relates generally to semiconductor devices and, more particularly, to a concentrated photovoltaic (CPV) receiver package or module which is assembled to include a leadframe assembly comprising multiple frames stacked on top of each other in to provide high thermal dissipation and high voltage isolation, while at the same providing a high level of reliability with a comparatively low manufacturing cost. 
     2. Description of the Related Art 
     Photovoltaic cells or dies are a well known means for producing electrical current from electromagnetic radiation. Traditional photovoltaic cells comprise junction diodes fabricated from appropriately doped semiconductor materials. Such devices are typically fabricated as thin, flat wafers with the junction formed parallel to and near one of the flat surfaces. Photovoltaic cells are intended to be illuminated through their so-called “front” surface. Electromagnetic radiation absorbed by the semiconductor produces electron-hole pairs in the semiconductor. These electron-hole pairs may be separated by the electric field of the junction, thereby producing a photocurrent. Currently known photovoltaic cells typically have a generally quadrangular (e.g., square) configuration defining four peripheral side edges, and include a pair of bus bars which are disposed on the top or front surface and extend along respective ones of an opposed pair of the side edges. The bus bars are used to facilitate the electrical connection of the photovoltaic cell to another structure, as described in more detail below. 
     There is currently known in the electrical arts semiconductor devices known as CPV receiver die packages or modules. Currently known CPV modules typically comprise a ceramic substrate having a conductive pattern disposed on one side or face thereof. Attached to the substrate and electrically connected to the conductive pattern are electrical components, including a pair of preformed wire connectors and a packaged diode. Also attached to the substrate and electrically connected to the conductive pattern thereof is a CPV receiver cell or die. The electrical connection between the receiver die and the conductive pattern is often facilitated by a pair of punched thin metal foil or braided ribbon/mesh connectors which extend along and are welded or soldered to respective ones of opposed sides of the receiver die, which typically has a quadrangular or square configuration as indicated above. More particularly, the pair of punched thin metal foils or braided ribbon/mesh connectors are welded or soldered to respective ones of the bus bars on the top or front surface of the receiver die. In certain existing CPV modules, the electrical connection of the receiver die to the conductive pattern is facilitated by the use of multiple wires bonded to the bus bars on the front surface of the receiver die and the bond pads of the conductive pattern of the substrate, the wires being used as an alternative to the aforementioned braided ribbon or mesh interconnects. These wire bonds are often fabricated from gold, and are provided in differing numbers and/or diameters depending on the design of the CPV module. The CPV module may further include a light concentration means which is adapted to concentrate solar radiation onto the front surface of the receiver die. 
     In certain currently known CPV receiver die packages or modules, anywhere from about 500 to about 1500 suns of energy will typically be focused on the receiver cell or die of the CPV package, such receiver die converting the impinging light into electricity and heat which must be effectively dissipated from the CPV package as well. In this regard, the total incoming energy often falls within the range of from about 45 to about 225 watts, of which about 65% is typically converted to heat that must be managed in the CPV package. CPV packages are often electrically connected to each other in series within panels, with multiple panels also being connected in series. These systems often operate at very high voltage, with the requirement typically being that each CPV package provides about 5,000 volts of electrical isolation. The requirements for high thermal dissipation as well as high voltage isolation, coupled with market demands for low cost as well as high reliability, are not satisfied by currently known CPV receiver die packages or modules. 
     In an attempt to satisfy the aforementioned desired attributes of high thermal dissipation coupled with high voltage isolation in a CPV package, one of the leading solutions provided in the CPV industry is the use of a ceramic core substrate with metal conductors adhered to one or both of its top and bottom surfaces. The ceramic material provides thermal conductivity from the top metal to the bottom metal, as well as voltage isolation between the circuit metallization on the top surface and the external environment. Another approach is to use more traditional semiconductor leadframe based solutions. However, the attempted leadframe solutions have generally been unsuccessful since providing good thermal conductivity concurrently with required voltage isolation has increased the complexity of these solutions, and hence the cost. Even the use of the aforementioned ceramic core substrate with metal conductors as a solution has proven to present difficulties in finding a good tradeoff between high thermal performance, electrical isolation and cost. 
     The present invention provides a matrix leadframe based approach in a unique assembly sequence to the addresses these and other shortcomings of the prior art CPV packages. In the CPV package of the present invention, a leadframe assembly is provide, such leadframe assembly including multiple frames stacked on top of each other. A top frame provides the electrical interconnect between the top or front surface of the receiver die and the bypass diode required to complete the circuit. The top frame also provides the attach pad or connector for a hook up wire which carriers the current away from the CPV package. In the assembly of the CPV package of the present invention, the top frame is placed into an empty fixture and solder paste is screen printed on areas which will connect to the receiver die, the diode, and a stand off die. The standoff die is a mechanical component only, and serves to maintain the separation between the top frame hook up wire pad and a middle frame of the assembly. The receiver die, the diode, and the standoff die are then each placed onto the top frame in a flip chip orientation so that the bus bars on the receiver die, the anode of the diode and a metalized surface of the standoff die are each in contact with corresponding connection points on the top frame. The assembly is then put through a reflow oven to join the receiver die, diode, and standoff die to the top frame. 
     In the next process step, the aforementioned middle frame is placed into an empty fixture and run through a dispensing process which deposits a solder paste under where the receiver die and diode will be connected thereto. Reusable shims are placed over locating features in the fixture and on top of side rails of the middle frame. These shims are used to maintain a prescribed gap between the top and middle frames. The top frame is then placed onto the fixture using features in the fixture to ensure the required alignment between the top and middle frames. The assembly is then put through a reflow. After the top and middle frames have been joined, the handling rails and interconnect structure (i.e., the support structure) of the top frame are cut away so that only the hook up wire pads will electrically accessible outside of the final CPV package. However, the middle frame retains its handling rails and interconnect structure. 
     In the next process step, a bottom frame is placed into an empty fixture and run through a dispensing process during which a thermally conductive, but electrically isolating thermal interface material (or TIM material) is deposited thereon. The previously joined top and middle frames are placed into the fixture and located relative to the bottom frame using features in the fixture. The previously deposited TIM material makes contact between the middle and bottom frames. The assembly is then placed into an oven and cured. After cure, the handling rails and interconnect structure of the middle frame are cut away such that only the hook up wire pads of the top frame will be electrically accessible outside of the completed CPV package. The bottom frame retains its handling rails and interconnect structure. The three layer structure including the top, middle and bottom frames is then over-molded such that the top of the receiver die, the two hook up wire interconnect pads and the bottom surface of the bottom frame remain exposed. Finally, the bottom frame handling rails and interconnect structure are then cut away leaving the finished and singulated CPV package. 
     Part of the uniqueness of the above-described CPV package lies in connecting a leadframe to the bus bars of the receiver die and to the bypass diode using solder, which provides the CPV package with much lower electrical resistance, while also improving the power out of the CPV package. Further, connecting the bottom of the receiver die and the cathode of the bypass diode using solder provides the CPV package with much lower electrical resistance, and improves the power out of the package as well. Still further, the TIM material used in the CPV package of the present invention provides lower thermal resistance, and is thinner then the alumina structures currently in use of existing CPV packages, thus providing superior thermal management. Further, that the top and middle frames of the CPV package have no exposed metal other than the hook up wire interconnect pads makes the CPV package inherently superior from a voltage isolation standpoint. The exposed heat spreader defined by the exposed bottom surface of the bottom frame also provides a superior interface to the next level of thermal management. Thus, the CPV package of the present invention provides superior electrical and thermal performance, while providing approximately 5,000 volts of isolation demanded by most applications. These and other features of the present invention will be described in more detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These, as well as other features of the present invention, will become more apparent upon reference to the drawings wherein: 
         FIG. 1  is a top plan view of a CPV module or package constructed in accordance with the present invention; 
         FIG. 2  is a cross-sectional view taken along line  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along line  3 - 3  of  FIG. 1 ; 
         FIG. 4  is a top plan view of the CPV package of the present invention in a partially completed state of fabrication prior to the formation of the mold body thereof; 
         FIG. 5  is a top plan view of the bottom frame component of the leadframe of the CPV package of the present invention; 
         FIG. 6  is a top plan view of the middle frame component of the leadframe of the CPV package of the present invention; 
         FIG. 7  is a top plan view of the top frame component of the leadframe of the CPV package of the present invention; and 
         FIGS. 8A-8I  depict an exemplary sequence of steps for facilitating the fabrication of the CPV package of the present invention. 
     
    
    
     Common reference numerals are used throughout the drawings and detailed description to indicate like elements. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings wherein the showings are for purposes of illustrating a preferred embodiment of the present invention only, and not for purposes of limiting the same,  FIGS. 1-3  depict a concentrated photovoltaic (CPV) package or module  10  constructed in accordance with the present invention. In  FIGS. 1-3 , the CPV package  10  is depicted in its fully fabricated state. In  FIG. 4 , the CPV module  10  is depicted in partially completed states of fabrication, with  FIGS. 8A-8I  depicting an exemplary sequence of steps for facilitating the fabrication of the CPV package  10 . 
     Referring now to  FIGS. 1-7 , the CPV module  10  comprises a leadframe assembly  12  which comprises a first or top frame  14  (shown in  FIG. 5 ), a second or middle frame  16  (shown in  FIG. 6 ), and a third or bottom frame  18  (shown in  FIG. 7 ) which are stacked upon each other in a prescribed arrangement, as will be described in more detail below. As best seen in  FIG. 5 , the top frame  14  of the leadframe assembly  12  has a generally quadrangular configuration and, from the perspective shown in  FIGS. 2 and 3 , defines a generally planar top surface  20 , and an opposed, generally planar bottom surface  22 . Additionally, as best seen in  FIG. 5 , the top frame  14  includes four side segments  24  which are integrally connected to each other, and are arranged in a generally square pattern. As such, the side segments  24  collectively define an opening  26 . As further seen in  FIG. 5 , one pair of the side segments  24  which extend in spaced, generally parallel relation to each other each define a plurality (e.g., six) contact fingers or tab portions  28  which protrude into the interior of the opening  26 . As is apparent from  FIG. 5 , each of the tab portions  28  on one of the side segments  24  including the same is disposed in opposed relation to a corresponding one of the tab portions  28  defined by the remaining one of the side segments  24  including the same. Those of ordinary skill in the art will recognize that the formation of six tab portions  28  on each of the side segments  24  including the same is exemplary only, and that such number of tab portions  28  may be decreased or increased without departing from the spirit and scope of the present invention. 
     The top frame  14  of the leadframe assembly  12  further includes an interconnect pad portion  30  which, as also seen in  FIG. 5 , protrudes outwardly from the central region of one of the two side segments  24  which does not include the tab portion  28  formed thereon. Thus, the interconnect pad portion  30  extends away from the opening  26 , rather than residing within the interior thereof. Still further, the top frame  14  includes a diode attach pad portion  32  which protrudes outwardly from one end region of that side segment  24  which extends in spaced, generally parallel relation to the side segment  24  having the interconnect pad portion  30  protruding therefrom. Thus, like the interconnect pad portion  30 , the diode attach pad portion  32  does not reside within the interior of the opening  26 . The use of the interconnect and diode attach pad portions  30 ,  32  of the top frame  14  will be described in more detail below. 
     Referring now to  FIG. 6 , the middle frame  16  of the leadframe assembly  12 , when viewed from the perspective shown in  FIGS. 2 and 3 , also defines a generally planar top surface  34 , and an opposed, generally planar bottom surface  36 . Additionally, as is apparent from  FIG. 6 , the middle frame  16  is not a unitary structure. Rather, the middle frame  16  includes a first section  38  and a second section  40  which are disposed in spaced relation to each other. The first section  38  defines a die attach pad portion  42  which has a generally square configuration. The die attach pad portion  42  is integrally connected to and protrudes from a central region of one side of an interconnect portion  44  of the first section  38  which itself has a generally rectangular configuration. The second section  40  of the middle frame  16  has a generally rectangular configuration mirroring that of the interconnect portion  44  of the first section  38 . As is further shown in  FIG. 6 , the first and second sections  38 ,  40  are oriented relative to each other such that the die attach pad portion  42  of the first section  38  resides between the interconnect portion  44  thereof and the second section  40 . 
     Referring now to  FIG. 7 , the bottom frame  18  of the leadframe assembly  12 , when viewed from the perspective shown in  FIGS. 2 and 3 , also defines a generally planar top surface  46 , and an opposed, generally planar bottom surface  48 . The bottom frame  18  also has a generally rectangular configuration. In this regard, the length and width dimensions of the bottom frame  18  are roughly equal to the maximum length and width dimensions of the middle frame  16 . 
     In the CPV package  10  of the present invention, it is contemplated that the leadframe assembly  12 , and in particular the top, middle and bottom frames  14 ,  16 ,  18  thereof, will be fabricated from a suitable conductive metal material, such as copper, copper with nickel, copper with PPF, etc. Additionally, as will be discussed below in relation to  FIGS. 8A-8I , in the manufacturing process corresponding to the CPV package  10 , it is contemplated that the top, middle and bottom frames  14 ,  16 ,  18  will each originally be provided as part of an etched or stamped strip. In this regard, the top, middle, and bottom frames  14 ,  16 ,  18  will each include interconnect structures which facilitate the integral connection thereof to handling rails or side rails ultimately removed during a singulation process completed as part of the fabrication process for the CPV package  10 . 
     The CPV package  10  constructed in accordance with the present invention further comprises a photovoltaic receiver cell or die  50 . The receiver die  50  has a generally square configuration, and defines a generally planar top or front surface  52 , and an opposed, generally planar bottom or back surface  54 . In addition, the receiver die  50  defines four (4) generally straight peripheral side surface segments. The receiver die  50  is fabricated from a number of layers, including an active layer which is applied to one side or face of an underlying substrate, and defines the front surface  52  of the receiver die  50 . The active layer includes a pair of elongate contact strips or bus bars  56  which extend in spaced, generally parallel relation to each other along respective ones of an opposed pair of the peripheral side surface segments of the receiver die  50 . 
     In the CPV package  10 , the receiver die  50  is electrically connected to the top frame  14 . More particularly, such electrical connection is facilitated by attaching and electrically connecting each of the tab portions  28  protruding from one of the side segments  24  to a respective one of the bus bars  56  of the receiver die  50 , the bus bars  56  being attached to those portions of the bottom surface  22  of the top frame  14  which are defined by corresponding sets of the tab portions  28 . Such electrical connection is preferably facilitated through the use of conductive solder paste or epoxy, though the present invention is not intended to be limited to any specific attachment material. When the bus bars  56  of the receiver die  50  are electrically connected to corresponding sets of the tab portions  28  in the aforementioned manner, the vast majority of the front surface  52  of the receiver die  50  is exposed within the opening  26  defined by the top frame  14  in the manner best shown in  FIG. 4 . 
     In addition to the receiver die  50 , the CPV package  10  includes a bypass diode  58  which has a generally square configuration and is attached and electrically connected to that region of the bottom surface  22  of the top frame  14  defined by the diode attach pad portion  32  thereof. The attachment and electrical connection of the anode of the bypass diode  58  to the underside of the diode attach pad portion  32  is also preferably facilitated through the use of conductive solder paste or epoxy. Thus, both the receiver die  50  and the bypass diode  58 , by virtue of their electrical connection to the top frame  14 , are in turn electrically connected to each other. 
     The CPV package  10  further comprises a standoff die  60  which, like both the receiver die  50  and bypass diode  58 , has a generally square configuration and is also attached to the top frame  14 . More particularly, the standoff die  60  is attached to that region of the bottom surface  22  of the top frame  14  which is defined by the interconnect pad portion  30  thereof. The standoff die  60  is preferably fabricated from silicon, with the attachment thereof to the underside of the interconnect pad portion  30  preferably being facilitated through the use of the solder paste or epoxy described above. 
     In the CPV package  10 , the receiver die  50 , the bypass diode  58 , and the standoff die  60 , in addition to each being attached to the top frame  14 , are also attached to the middle frame  16 . More particularly, the back surface  54  of the receiver die  50  is attached and electrically connected to that region of the top surface  34  of the middle frame  16  defined by the die attach pad portion  42  of the first section  38  through the use of a conductive solder paste or epoxy. Similarly, that surface or face of the bypass diode  58  which is opposite that attached to the bottom surface  22  of the top frame  14  and defines the cathode is attached and electrically connected to a prescribed region of the top surface  34  of the middle frame  16  defined by the interconnect portion  44  of the first section  38  thereof through the use of a conductive solder paste or epoxy. Further, that surface or face of the standoff die  60  opposite that attached to the bottom surface  22  of the top frame  14  is attached to a prescribed region of the top surface  34  of the middle frame  16  defined by the second section  40  thereof through the use of a conductive solder paste or epoxy. As a result, the receiver die  50 , the bypass diode  58  and the standoff dies  60  are each sandwiched or captured between the top and middle frames  14 ,  16 . As indicated above, in the CPV package  10 , the standoff die  60  is a mechanical component which is used to maintain a prescribed spatial separation or gap between the interconnect pad portion  30  of the top frame  14  and the second section  40  of the middle frame  16 . 
     As is apparent from  FIGS. 2-4 , in the CPV package  10 , the assembly including the top and middle frames  14 ,  16  having the receiver die  50 , bypass diode  58  and standoff die  60  interposed therebetween in the aforementioned manner is itself attached to the bottom frame  18 . More particularly, the bottom surface  36  of the middle frame  14  as defined by the first and second sections  38 ,  40  thereof is attached to the top surface  46  of the bottom frame  18  through the use of a layer  62  of a thermal interface material or TIM material. 
     In the CPV package  10 , at least portions of the top, middle and bottom frames  14 ,  16 ,  18  of the leadframe assembly  12 , the receiver die  50 , the bypass diode  58  and the standoff die  60  are covered by an encapsulant material which, upon hardening, defines a mold body  64  of the CPV package  10 . As best seen in  FIGS. 1-3 , the mold body  64  has a generally quadrangular (e.g., rectangular configuration). Additionally, from the perspective shown in  FIGS. 1-3 , the mold body  64  defines a generally planar top surface  66 , an opposed, generally planar bottom surface  68 , and a side surface  70  which is segregated into four (4) generally straight side surface segments. 
     As further seen in  FIGS. 1-3 , the mold body  64  is formed to cover the entirety of the top surface  20  of the top frame  14 , with the exception of a prescribed region of the top surface  20  which is defined by the interconnect pad portion  30  thereof. In this regard, formed in the top surface  66  of the mold body  64  is a generally square first window  72  in which the interconnect pad portion  30  of the top frame  14  is exposed. Though the mold body  64  covers the peripheral side surface segments of the receiver die  50 , the majority of the front surface  52  of the receiver die  50  is exposed in a generally square second window  74  of the mold body  64  which, like the first window  72 , is also formed in the top surface  66  thereof. As will be recognized, the length and width dimensions of the second window  74  are substantially equal to those of the opening  26  defined by the top frame  14 . 
     The mold body  64  of the CPV package  10  further covers the peripheral side surface segments of both the bypass diode  58  and standoff die  60 . As indicated above, the opposed top and bottom surfaces of such bypass diode  58  (defining the anode and cathode, respectively) and standoff die  60  are attached to respective ones of the bottom surface  18  of the top frame  14 , and the top surface  34  of the middle frame  16 . Though the majority of the top surface  34  of the middle frame  16  is also covered by the mold body  64 , a prescribed region of the top surface  34  defined by the interconnect portion  44  of the first section  38  is exposed in a generally square third window  76  also formed in the top surface  66  of the mold body  64 . As best seen in  FIG. 1 , the length and width dimensions of the first and third windows  72 ,  76  are substantially equal to each other, and are less than those of the second window  74  which is positioned between the first and third windows  72 ,  76 . 
     As is most apparent from  FIGS. 2 and 3 , the mold body  64  is formed to cover those portions of the top surface of the bottom frame  18  which are not already covered by the top and middle frames  14 ,  16 . Though the mold body  64  also covers the peripheral side surface of the bottom frame  18 , the majority of the bottom surface  48  of the bottom frame  18  is uncovered by the mold body  64 , and thus exposed in the bottom surface  68  thereof. However, as seen in  FIGS. 2 and 3  as well, it is contemplated that the peripheral side surface of the bottom frame  18  may be formed to include an undercut or reentrant portion  78  which is filled by the mold body  64 , and creates a firm mechanical interlock between the mold body  64  and bottom frame  18 , thus preventing any undesired separation therebetween. 
     In the completed CPV package  10 , the mold body  64  is fabricated to be of a thickness which allows those surfaces thereof defining the second window  74  to be used as a modality which facilitates the alignment of a light concentrating device such as an optical light guide or prism to the front surface  52  of the receiver die  50  which, as indicated above, is exposed in the second window  74 . Those portions of the top and middle frames  14 ,  16  exposed within the respective ones of the first and third windows  72 ,  76  effectively serve as “hook up” interconnect pads which allow for the electrical connection of hook up wires to the CPV package  10  for purposes such as carrying current away from the CPV package  10 . Since the only exposed metal of the top and middle frames  14 ,  16  is that which is exposed in respective ones of the first and third windows  72 ,  76 , the CPV package  10  is inherently superior from a voltage isolation standpoint. 
     Still further, in the CPV package  10 , connecting the bus bars  56  of the receiver die  50  and the bypass diode  58  to the top frame  14  through the use of solder provides the CPV package  10  with much lower electrical resistance and improves the power out thereof. Similarly, connecting the back surface  54  of the receiver die  50  and the cathode of the bypass diode  58  to the middle frame  16  through the use of solder similarly provides the CPV package  10  with much lower electrical resistance and also improves the power out thereof. The exposed bottom surface  48  of the bottom frame  18  in the mold body  64  of the CPV package  10  provides the same with superior thermal performance, the heat generated by the receiver die  50  effectively being transferred to the bottom frame  18  via the middle frame  16  (to which the receiver die  50  is attached) and the layer  62  of the TIM material which is used to facilitate the attachment of the middle frame  16  to the bottom frame  18 . As indicated above, the layer  62  of TIM material provides lower thermal resistance and is thinner than the alumina structures used in prior art CPV packages. 
     Having thus described the structural features of the CPV package  10 , an exemplary method of fabricating the same will now be described with specific reference to  FIGS. 8-8I . Referring now to  FIG. 8A , in an initial step of the fabrication process for the CPV package  10  of the present invention, the top frame  14  is placed into an empty fixture, with conductive solder paste or epoxy being screen printed onto the areas of the top frame  14  which will connect to the receiver die  50 , the bypass diode  58 , and the standoff die  60 . More particularly, the solder paste or epoxy is screen printed onto a prescribed region of the bottom surface  22  of the top frame  14  which is defined by the interconnect pad portion  30  thereof, a prescribed region of the bottom surface  22  which is defined by the diode attach pad portion  32  thereof, and those regions of the bottom surface  22  defined by the tab portions  28  protruding into the opening  26  from a corresponding pair of the side segments  24 . As shown in  FIG. 8A , in its original, unsingulated state, the top frame  14  includes interconnect structures  80  (e.g., tie bars) which facilitate the integral connection thereof to a spaced, generally parallel pair of side rails  82 . Thus, the unsingulated top frame  14  comprises a portion of a leadframe strip which, in addition to the top frame  14 , includes the interconnect structures  80  and side rails  82 . As indicated above, such leadframe strip including the top frame  14  may be fabricated through the implementation of a suitable etching or stamping process. 
     Referring now to  FIG. 8B , in the next step of the fabrication process for the CPV package  10 , the receiver die  50 , the bypass diode  58  and the standoff die  60  are each placed onto the bottom surface  22  of the top frame  14  in a flip chip orientation. More particularly, each of the bus bars  56  of the receiver die  50  is brought into contact with the solder paste or epoxy applied to a corresponding set of the tab portions  28  protruding from a respective one of the side segments  24 . The anode of the bypass diode  58  is brought into contact with the solder paste or epoxy applied to the diode attach pad portion  32  of the top frame  14 , with a metalized surface of the standoff die  60  being brought into contact with the solder paste or epoxy applied to the interconnect pad portion  30  of the top frame  14 . The assembly shown in  FIG. 8B  is then put through a reflow oven to join the receiver die  50  to the top frame  14 . 
     Referring now to  FIG. 8C , in the next step of the fabrication process for the CPV package  10 , the middle frame  16  is placed into an empty fixture, and run through a dispensing process. The dispensing process is used to deposit conductive solder paste or epoxy on those regions of the top surface  34  of the middle frame  16  where the back surface  54  of the receiver die  50 , the cathode of the bypass diode  58 , and one side or face of the standoff die  60  will ultimately be connected thereto. More particularly, the solder paste or epoxy is applied to a prescribed region of the top surface defined by the die attach pad portion  42  of the first section  48 , a prescribed region of the top surface  34  defined by the interconnect portion  44  of the first section  38 , and a prescribed region of the top surface  34  defined by the second section  40 , in the manner shown in  FIG. 8C . Like the top frame  14 , in its original, unsingulated state, the middle frame  16  includes interconnect structures  82  which facilitate the integral connection thereof to a spaced, generally parallel pair of side rails  86 . Thus, the unsingulated middle frame  16  comprises a portion of a leadframe strip which, in addition to the middle frame  16 , includes the interconnect structures  84  and side rails  86 . Such leadframe strip including the middle frame  16  may be fabricated through the implementation of a suitable etching or stamping process. 
     Referring now to  FIG. 8D , in the next step of the fabrication process for the CPV package  10 , reusable shims (not shown) are placed over locating features in the fixture and on top of the side rails  86  of the leadframe strip including the middle frame  16 . The leadframe strip including the top frame  14  in then flipped over from its orientation shown in  FIGS. 8A and 8B , and is placed onto the fixture having the leadframe strip with the middle frame  16  interfaced thereto using features in the fixture to ensure a prescribed alignment between the top and middle frames  14 ,  16 . The aforementioned shims are used to maintain a prescribed gap between the top and middle frames  14 ,  16 . The stacked assembly of the leadframe strips including the top and middle frames  14 ,  16  as shown in  FIG. 8D  is then put through a reflow. 
     Referring now to  FIG. 8E , after the top and middle frames  14 ,  16  have been joined in the step described above in relation to  FIG. 8D , the handling rails or side rails  82  and portions of the interconnect structures  80  of the leadframe strip including the top frame  14  are cut away or singulated. However, as also shown in  FIG. 8E , at this stage of the manufacturing process for the CPV package  10 , the interconnect structures  84  and side rails  86  of the leadframe strip including the middle frame  16  are not yet cut away or singulated. 
     Referring now to  FIG. 8F , in the next step of the fabrication process for the CPV package  10 , the bottom frame  18  is placed into an empty fixture and run through a dispensing process during which the layer  62  of the TIM material is deposited on a prescribed portion of the top surface  46  thereof. As is shown in  FIG. 8F , in its original, unsingulated state, the bottom frame  46  also includes interconnect structures  88  which facilitate the integral connection thereof to a spaced, generally parallel pair of side rails  90 . Thus, the unsingulated bottom frame  18  also comprises a portion of a leadframe strip which, in addition to the bottom frame  18 , includes the interconnect structures  88  and side rails  90 . Such leadframe strip including the bottom frame  18  may be fabricated through the implementation of a suitable etching or stamping process. 
     Referring now to  FIG. 8G , in the next step of the fabrication process for the CPV package  10 , the previously joined top and middle frames  14 ,  16  as shown in  FIG. 8E  are placed into the fixture holding the leadframe strip including the bottom frame  18  and located in a prescribed orientation relative thereto using features in the fixture. The stacked assembly of the top, middle and bottom frames  14 ,  16 ,  18  shown in  FIG. 8G  is then placed into an oven and cured. 
     Referring now to  FIG. 8H , in the next step of the fabrication process for the CPV package  10 , after the curing step described in relation to  FIG. 8G  above has been completed, the side rails  86  and portions of the interconnect structures  84  of the leadframe strip including the middle frame  16  are cut away or singulated. However, at this stage of the fabrication process for the CPV package  10 , the interconnect structures  88  and side rails  90  of the leadframe strip including the bottom frame  18  are not cut away or singulated. 
     Referring now to  FIG. 8I , in the next step of the fabrication process for the CPV package  10 , the three layer structure including the top, middle and bottom frames  14 ,  16 ,  18  is over-molded in a manner facilitating the formation of the mold body  64 . The structural features of the mold body  64  and manner in which the same is applied to the top, middle and bottom frames  14 ,  16 ,  18  is described with particularity in relation to  FIGS. 1-3  above. Subsequent to the formation of the mold body  64 , the side rails  90  and interconnect structures  88  of the leadframe strip including the bottom frame  18  are cut away or singulated, thus completing the formation of the CPV package  10 . 
     This disclosure provides exemplary embodiments of the present invention. The scope of the present invention is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification, such as variations in structure, dimension, type of material and manufacturing process may be implemented by one of skill in the art in view of this disclosure.

Technology Classification (CPC): 7