Method and apparatus for doubling back single gauge lead frame

#Semiconductor dies are created from a silicon wafer through the employment of various etching, doping, and depositing steps that are well known in the art. Ultimately, the semiconductor die may be packaged by forming an encapsulant around the semiconductor die so as to form an "integrated circuit package" having a variety of pinouts or mounting and interconnection schemes. Plastic is often utilized as an encapsulant. Integrated circuit packages that utilize plastic as an encapsulant are generally less expensive then other packaging options.

#Prior to encapsulation, a semiconductor die is mounted upon what is known in the art as a lead frame. The lead frame provides mechanical support of the semiconductor die during the encapsulation procedure. In addition to providing mechanical support to the semiconductor die, the lead frame provides electrically conductive paths (known in the art as leads) between the semiconductor die and external circuitry. The lead frame also enables the semiconductor die to transfer excess thermal energy during operation to an external heat sink.

#Poor heat transfer between a packaged semiconductor die and an external heat sink typically results in high die operating temperatures. High die temperatures may result in unacceptable performance degradation or reliability problems. Therefore, it is essential for the lead frame encapsulated within materials such as plastic with low thermal coefficients to provide an thermal path between the semiconductor die and an external heat sink.

#The features of the present invention may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

#FIG. 1A is an illustration of a portion of a lead frame strip (not shown) which includes a recently developed lead frame assembly and a lead frame body.

#FIG. 1B is a cross sectional view of a recently developed dual gauge lead frame assembly mounted semiconductor die as shown in FIG. 1A subsequent to being encapsulated to form a semiconductor die package.

#Broadly speaking, a single gauge lead frame for use in manufacturing of semiconductor die packages capable of realizing benefits associated with dual gauge lead frames is disclosed. In the described embodiment, the single gauge lead frame includes a first support pad and a die attach area. The lead frame also includes a second support pad that is substantially a mirror image of the first support pad. The second support pad is integrally formed with and attached to the first support pad. During lead frame manufacture the second support pad is bent back, or placed, upon the first support pad to form a double thick support pad. This double thick support pad is provides thermal transfer capacity and mechanical support substantially similar to that provided by the support pad of a dual gauge lead frame. In this manner, the present invention is capable of providing the advantages of a dual gauge lead frame without the added cost of manufacture caused by the complexity of fabricating dual gauge lead frames from dual gauge, or thickness, lead frame blanks. A method for producing a lead frame and a semiconductor package is also described.

#In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to not unnecessarily obscure the present invention.

#As discussed above, lead frames are typically formed from metal strips. FIG. 2A illustrates a lead frame assembly 220 before it is separated from the strip. Lead frame assembly 220 is enclosed within and supported by a lead frame body 210 which is part of the lead frame metal strip from which the lead frame is created. The embodiment of the lead frame 200 that is shown is designed for employment with an overmolded integrated circuit package. As shown, the lead frame assembly 220 includes a first support pad 230, a second support pad 232, a plurality of leads 270, and a die attach area 272.