Quad flat package heat slug composition

#1. Field of the Invention

#The present invention relates to an integrated circuit package.

#2. Description of Related Art

#The objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, wherein:

#FIG. 1 is a perspective view of an integrated circuit package of the present invention;

#FIG. 2 is a cross-sectional view of the integrated circuit package taken at line 2--2 of FIG. 1.

#Referring to the drawings more particularly by reference numbers, FIG. 1 shows an integrated circuit package 10 of the present invention. The package 10 includes a housing 12 which has a top surface 14, a bottom surface 16 and four side surfaces 18. Extending from the side surfaces 18 are the leads 20 of a lead frame 22. The leads 20 are typically soldered to a printed circuit board (not shown). Although "gull-wing" type leads are shown, it is to be understood that the package may have any arrangement of leads such as pogo pins that extend from the bottom surface 16 of the housing and are soldered to the printed circuit board.

#As shown in FIG. 2, the package 10 includes an integrated circuit 24 that is connected to the lead frame 22 and encapsulated by the housing 12. Coupled to the integrated circuit 24 is a heat slug 26 that has a top surface 28 which extends to the top surface 14 of the housing 12. The heat slug 26 is constructed from a material that is both thermally conductive and has a coefficient of thermal expansion which matches the coefficient of thermal expansion of the housing 12 and the integrated circuit 24.

#The housing 12 is typically constructed from a glass filled epoxy which has a coefficient of thermal expansion of approximately 15.0 parts per million per degrees centigrade ("ppm/.degree.C."). The integrated circuit is typically constructed from silicon that has a coefficient of thermal expansion of approximately 3.0 ppm/.degree.C. In the preferred embodiment, the heat slug 26 is constructed from either nickel which has a coefficient of approximately 13.0 ppm/.degree.C., or a copper clad with molybdenum which have coefficients of 17.0 ppm/.degree.C. and 5.0 ppm/.degree.C., respectively, that combine to have a net coefficient of 13.0 ppm/.degree.C. As one embodiment, the heat slug 26 may have approximately 70% copper and 30% molybdenum measured across the thickness of the slug.