Abstract:
Consistent with an example embodiment, there is a package assembly structure. The structure comprises a lead frame having a topside surface and an opposite under-side surface; the lead frame includes a die attach paddle, wherein a die attach region is defined on the opposite under-side surface. Pad landings surround the die attach region. A plurality of locking pins are arranged at predetermined locations about the die attach paddle, on the top side surface. The plurality of locking pins may be formed integrally in the lead frame and project upward from the top side surface.

Description:
FIELD 
       [0001]    The disclosure is directed toward a lead frame having a passive component intermediate structure. More particularly, the lead frame is modified to provide enhanced mechanical anchoring of the intermediate structure having passive components placed thereon. 
       BACKGROUND 
       [0002]    Electronic components and systems destined for use in automotive applications must perform under severe environmental conditions. Within the engine compartment, operating temperatures may range from −40° C. to above 125° C. Exposure to elements on the road, such as dirt, grease, salt, etc., takes its toll on mechanical and electronic components. A number of these components are combinations of discrete passive components such as capacitors, inductors, and resistors connected to integrated circuit devices. 
         [0003]    As more and more mechanical components in the automobile are replaced by electronics, there are the competing requirements of designing and building the components and electronic subsystems (i.e, engine control systems, anti-lock braking systems, air bag control systems, security systems, etc.) to be both durable yet cost-effective. The electronics must be reliable even after years of exposure to the severe operating environment. Failure of these components may be catastrophic. 
         [0004]    There is a need for a packaging technique of combining passive components with integrated circuits which is sufficiently robust to withstand the rigors of an automotive environment. 
       SUMMARY 
       [0005]    The present disclosure has been found useful in assembling components that can withstand the rigors of an automotive environment. An integrated circuit is mounted onto a first surface of a lead frame and electrically connected to it. Additional passive components are mounted onto an intermediate substrate. The intermediate substrate is mounted on a surface opposite the first surface. The passive components mounted on the intermediate substrate in some applications, may be connected to selected bond pads on the integrated circuit through mechanical locking connectors on the intermediate substrate and those included on the opposite side surface of the lead frame. These locking connectors in the lead frame or intermediate substrate may either be locking pins or receptacles receiving the locking pins. These locking connectors provide mechanical strength in holding together the intermediate substrate populated with passive components with the lead frame and attached integrated circuit. The assembly of the lead frame, intermediate substrate, and integrated circuit are often encapsulated in a molding compound in an a system in package configuration. In one particular case, the packaged device is part of an automotive immobilizer system. 
         [0006]    In an example embodiment, there is a package assembly structure comprising a lead frame having a top-side surface and an opposite under-side surface. The lead frame includes a die attach paddle, wherein a die attach region is defined on the opposite under-side surface; pad landings surround the die attach region. A plurality of locking pins is arranged at predetermined locations about the die attach paddle on the top-side surface. A feature of this embodiment is that the plurality of locking pins may be formed integrally in the lead frame. 
         [0007]    In another example embodiment, an electronic device comprises a lead frame having a top-side surface and an opposite under-side surface, the lead frame including, a die attach paddle, wherein a die attach region are defined on the opposite under-side surface, pad landings surrounding the die attach region; and a plurality of locking couplings of a gender arranged at predetermined locations about the die attach paddle, on the topside surface. An intermediate substrate has locking couplings of an opposite gender corresponding to the predetermined locations for frictionally receiving the locking couplings of the lead frame and provide mechanical connection between the lead frame and the intermediate substrate; the intermediate substrate is mounted on the topside surface of the lead frame. The intermediate substrate has areas defined for passive component circuit. An active device die is attached to the die attach region on the opposite under-side surface of the lead frame and bond pads of the active device die are electrically connected to the pad landings by conductive interconnects. 
         [0008]    The above summaries of the present disclosure are not intended to represent each disclosed embodiment, or every aspect, of the present invention. Other aspects and example embodiments are provided in the figures and the detailed description that follow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The invention may be more completely understood in consideration of the following detailed description of various embodiments disclosed in connection with the accompanying drawings, in which: 
           [0010]      FIGS. 1A-1C  (Prior Art) illustrate an example of assembly of passive component assembly and integrated circuit device on a single lead frame in an electronic immobilizer package; 
           [0011]      FIGS. 2A-2D  present side views of assembly an example embodiment of the present disclosure; 
           [0012]      FIGS. 3A-3D  present side view of assembly of an example embodiment of the present disclosure; 
           [0013]      FIGS. 4A-4D  present top-views of an embodiment of an automotive component assembled according to the present disclosure; 
           [0014]      FIGS. 5A-5B  illustrate a lead frame having locking clips and an intermediate substrate attached thereon according to the present disclosure; 
           [0015]      FIG. 6  illustrates a lead frame with an intermediate substrate attached via locking pins in accordance with the present disclosure; 
           [0016]      FIGS. 7A-7B  illustrate a lead frame assembled with an intermediate substrate populated with passive components in accordance with the present disclosure; and 
           [0017]      FIG. 8  is a flow diagram of the assembly of a device in accordance with the present disclosure. 
       
    
    
       [0018]    While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION 
       [0019]    The disclosed embodiments have been found useful in increasing the reliability of assembling components that include integrated circuit (IC) devices connected to structures having passive components, such as resistors, capacitors, and inductors. In an example embodiment, on a front-side surface a lead frame substrate, an IC attached to a lead frame substrate located on a front-side surface, active device pads are wire bonded to defined areas on the lead frame. Additional passive components are mounted (usually via a pick-and-place process) onto a separate intermediate substrate. The intermediate substrate is attached, via locking connectors, to an opposite back side surface of the lead frame. The locking connectors include holes or locking pins in the lead frame or intermediate substrate and are of opposite gender. Predefined conductive traces in the lead frame electrically connect particular IC device pins to selected passive components via the IC device wire-bonds and predefined traces connected to the locking connectors. The assembly is encapsulated in molding compound. In an example embodiment, a particular package used is an electronic immobilizer package, which resembles a plastic dual-in-line (PDIP) package. In these embodiments, additional components beyond the integrated circuit are combined together to build circuit subsystems that fit into a single package. 
         [0020]    Refer to  FIGS. 1A-1C . On a top side surface of a lead frame assembly  5 , there are pads defined for the placement of passive components, such as chip capacitors  15 , and contacts  20  for a coil  10 . The passive components are glued and soldered onto the lead frame assembly  5 . On the opposite under-side surface of the lead frame assembly  5 , a device die  25  is bonded to a die attach area  30  (as indicated by the dashed-lined box), wire bonds  45  electrically connect die bond pads  35  to lead frame pad landings (“fingers”)  40 . The circuit assembly  55  is encapsulated in a suitable molding compound  50 , resulting in the LSP package  60 . 
         [0021]    The present LSP package assembly may suffer delamination between glue attaching components to the lead frame and the lead frame causing functional failures. Further, during the manufacturing process, short circuits may occur between passive components owing to conductive glue flowing between component connections. From production handling, the glued components may be dislodged from the lead frame. 
         [0022]    In accordance with the present disclosure, passive components are integrated onto an intermediate substrate, such as a printed circuit board (PCB), so as to become a passive component unit. In one example embodiment, the lead frame has a plurality of locking clips defined thereon. These locking clips engage locations defined in the passive component unit; the locking clips provide enhanced mechanical engagement of the passive component unit with the lead frame. In an example embodiment, the locking clips frictionally engage holes defined in the passive component unit; optionally after their frictional engagement, the locking pin may be soldered to provide electrical connection. The lead frame has a die attach area to which an IC device is bonded. The die attach area is surrounded by pad landings to which device die bond pads are wire bonded. Per design requirements, the appropriate pins on the IC device are connected to the passive components. The assembly of the lead frame, the intermediate passive component unit, and device die are encapsulated into a molding compound. 
         [0023]    Refer to  FIGS. 2A-2D . In an example embodiment, in an assembly  100 , a coil and other passive components  105  are attached to an intermediate substrate  110 . The intermediate substrate  105  has locking pins  115 . On a top-side surface of a lead frame  120 , the intermediate substrate  105  is inserted into the lead frame  120  having locking receptacles  125  to receive the locking pins  115  of the intermediate substrate  110 . These locking pins  115  are formed so that when engaged into the locking receptacles  125 , they may be frictionally held in.  FIG. 2B  depicts a structure  130  having the coil and other passive components  105  assembled on the intermediate structure  110 , and lead frame  120 . On an under-side surface of the lead frame  120 , a device die  140  is die attached with a suitable die bonding material  135 . The die bonding  135  may be with a glue, solder, ultrasonic welding, etc. Wire bonds  145  connect die attach pads  142  of the device die  140  with corresponding lead frame fingers so as to provide electrical connection to the device die  140 . Predefined locations on the lead frame  120  provide electrical connections to and from passive components and the device die  140 . Often, the locking pins  115  will be soldered to the predefined locations on the lead frame  120  to form electrical connections, as well. Having assembled all of the components, the assembly  150  of the device die  140 , intermediate substrate  110 , and passive components  105 , is encapsulated into a molding compound  160 . The completed device  170  of  FIG. 2D  undergoes additional process steps to prepare the device for the end-user. 
         [0024]    Refer to  FIGS. 3A-3D . In another example embodiment, a coil and other passive components  205  are attached to an intermediate structure  210 . Locking receptacles  225  are defined thereon. A lead frame  220  has locking pins  215  which engage with the locking receptacles  225  of the intermediate structure  210  as the intermediate structure  210  is mounted onto a side of the lead frame  220 . In one embodiment, these locking pins  215  can be soldered to the locking receptacles  225  to enhance the electrical connection between the lead frame  220  and the passive components  205  mounted onto the intermediate structure  210 .  FIG. 3B  shows the partially assembled device  230 . Refer to  FIG. 3C . On an opposite under-side surface of the lead frame  220 , a device die  240  is die attached to the lead frame  220  with a suitable die bonding material  235 . Wire bonds  245  connect die attach pads  242  of the device die  240  with corresponding lead frame fingers so as to provide electrical connection to the device die  240 . The assembly  250  is encapsulated into a molding compound  260 . The completed device  270  of  FIG. 3D  undergoes additional process steps to prepare the device for the end-user. 
         [0025]    Refer to  FIGS. 4A-4C . In an example embodiment, a lead frame  300  has a top-side surface and an opposite under-side surface. On a top-side surface of the lead frame  300 , a dashed-line area  310  defines an area of the lead frame encompassing the completed active circuit/passive device module. On the opposite under-side surface of the lead frame  300 , a die attach area  315  is defined by the dashed lines. Locking pins  320  have been defined in five locations ( 320   a - e ). In other embodiments, there may as few as one locking pin. To define a geometric plane and to enhance rigidity, three locking pins are distributed on the plane. On the opposite under-side surface of the lead frame  300 , a device die  350  is bonded. Bond pads  345  are electrically connected to bond pad landings  335  via bond wires  340 . The area defined by dashed lines  310  is where the lead frame is trimmed off after the device die and passive device module  350  are assembled. On the passive device module (intermediate structure)  350 , corresponding holes (i.e., locking receptacles)  325  in five locations ( 325   a - e ) engage the locking pins  320 . Passive devices which include a coil  330  and chip capacitors  335  are soldered onto the substrate of the intermediate structure  350 . After engaging the locking pins  320  with the locking receptacles  325 , the locking pins  320  may be secured mechanically by friction or gluing or soldering to these locking receptacle locations. The locations  325  may have metal through-hole plating and connect various passive components  330 ,  335  to particular device pads connected to the particular pad landings  335 . Refer to  4 C. The completed module  375  is encapsulated in a suitable molding compound. After encapsulation, the lead frame at the boundary  310  is trimmed. 
         [0026]    Refer to  FIGS. 5A-5B . In an example embodiment, a lead frame  400  having three locking pins  420  ( a - c ) integrally formed, accepts an intermediate structure having corresponding locking receptacles. A die attach area  415  is on the underside surface of the lead frame  400 . Pad landings  425  surround the die attach area. Dashed lines X, X′ and Y, Y′ define the area in which the lead frame  400  is trimmed after assembly of an electronic module according to the present disclosure.  FIG. 5B  shows a close-up view of the locking pin  420   a  on lead frame  400 . Note that in  FIG. 5B  locking pins  420   a - 420   c  are bent upward and is perpendicular to the planar surface of the lead frame  400 . The perpendicular locking pins  420   a - 420   c  engages the corresponding locking receptacle locations in an intermediate substrate attached thereon. 
         [0027]    Refer to  FIG. 6 . In an example embodiment, a lead frame  500  with an intermediate substrate  525  is attached to the lead frame  500  via locking pins  510  and  520 . 
         [0028]    Refer to  FIGS. 7A-7B . In an example embodiment, an assembly  700  has a lead frame  710  with locking pins  720  to which an intermediate substrate  715  is attached. Passive components  720  and a coil  730  are soldered onto the intermediate substrate  715 . The locking pins  720  may frictionally engage with the intermediate substrate  715  in some applications or be engaged by soldering or a combination, thereof. In some other applications, the through holes in the intermediate substrate  715  may be plated to facilitate electrical connection or may only be a mechanical connection to hold the intermediate substrate  715  to the locking pins  720  of the lead frame  710 . The mechanical connection may be such that the holes and locking pins are sized so that the locking pins frictionally engage with the holes. 
         [0029]    Refer to  FIG. 8 . In step  810  an example process, the particular component has an assortment of incoming materials which may include the lead frame and passive components. The lead frame may have an array of device positions. In step  820 , at predetermined locations, the locking pins are formed on the lead frame. Referring back to  FIGS. 5A-5B , the integral locking pins  420   a - 420   c , of lead frame  400 , would be bent upward and perpendicular to the plane of the lead frame  400 . Next in step  830 , the passive component unit is attached onto a first side of the lead frame. In step  840 , the IC device is attached to an opposite second side of the lead frame. At step  850 , the IC device is wire bonded. Next in step  860 , having made all of the electrical connections, the assembly is encapsulated in a molding compound. In step  870 , the array of assembled units is trimmed and formed into individual devices. Then in step  880 , the individual devices undergo a “final electrical” test  880  before shipping to the end user. 
         [0030]    In accordance with the present disclosure, other molded package types may be used. The lead frame may be modified to accommodate an appropriately configured intermediate structure. Further, the embodiments of the present disclosure are applicable for all general System-in-Packages, as well as Package-in-Package. The related production tooling would be designed to facilitate assembly. 
         [0031]    Various exemplary embodiments are described in reference to specific illustrative examples. The illustrative examples are selected to assist a person of ordinary skill in the art to form a clear understanding of, and to practice the various embodiments. However, the scope of systems, structures, and devices that may be constructed to have one or more of the embodiments, and the scope of methods that may be implemented according to one or more of the embodiments, are in no way confined to the specific illustrative examples that have been presented. On the contrary, as will be readily recognized by persons of ordinary skill in the relevant arts based on this description, many other configurations, arrangements, and methods according to the various embodiments may be implemented. 
         [0032]    To the extent positional designations such as top, bottom, upper, lower have been used in describing this disclosure, it will be appreciated that those designations are given with reference to the corresponding drawings, and that if the orientation of the device changes during manufacturing or operation, other positional relationships may apply instead. As described above, those positional relationships are described for clarity, not limitation. 
         [0033]    The present disclosure has been described with respect to particular embodiments and with reference to certain drawings, but the invention is not limited thereto, but rather, is set forth only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, for illustrative purposes, the size of various elements may be exaggerated and not drawn to a particular scale. It is intended that this disclosure encompass inconsequential variations in the relevant tolerances and properties of components and modes of operation thereof. Imperfect practice of the invention is intended to be covered. 
         [0034]    Where the term “comprising” is used in the present description and claims, it does not exclude other elements or steps. Where an indefinite or definite article is used when referring to a singular noun, e.g. “a” “an” or “the”, this includes a plural of that noun unless something otherwise is specifically stated. Hence, the term “comprising” should not be interpreted as being restricted to the items listed thereafter; it does not exclude other elements or steps, and so the scope of the expression “a device comprising items A and B” should not be limited to devices consisting only of components A and B. This expression signifies that, with respect to the present disclosure, the only relevant components of the device are A and B. 
         [0035]    Numerous other embodiments of the invention will be apparent to persons skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.