Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1995-01-17
2001-03-27
Thompson, Gregory (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C165S080200, C165S185000, C174S016300, C257S713000, C257S722000, C361S718000
Reexamination Certificate
active
06208513
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to semiconductor packages, and particularly to semiconductor packages cooled to an external environment by fins.
BACKGROUND OF THE INVENTION
As semiconductor circuits continue to increase in complexity, so does their power consumption, and consequently, the amount of heat that is generated. Conventional semiconductor circuits are formed on a die. The die and a lead frame to electrically connect to the circuits are embedded in a an insulating plastic or ceramic package.
Traditionally, a heat sink is used to cool the package. The heat sink is typically configured with a mounting base and perpendicular, or parallel fins. The mounting base can be attached to the package using thermally conductive adhesives, conformable, thermally conductive adhesive tapes, or conformable, thermally conductive liquids or greases, with or without pressure to form a thermally conductive joint.
In a traditional semiconductor package, the heat path is, indirectly, from the die, through the package, through the thermal joint, through the heat sink base, and finally into the fins where the heat can be dissipated into a surrounding environment by convection or radiative cooling.
There are several problems with such traditional semiconductor packages. A substantial portion of the heat path is through the package material, or other laminate layers, such as adhesives, which are usually poor conductors of heat. In addition, the differences between the thermal expansion characteristics of the package and the heat sink can warp the components to varying degrees. The warped components mechanically stress the package and tend to decrease the effectiveness of the bond.
Therefore, it is desired to improve the reliability and performance of semiconductor package cooling techniques. In addition, it is desired that the improved packaging techniques reduce the size, weight, cost, number of parts, and the number of manufacturing steps used to assemble the package.
SUMMARY OF THE INVENTION
A semiconductor die has electrical circuits formed on a first side surface. The opposing second side surface is usually electrically nonfunctional. The electrical circuits of the die can be connected to power and signalling sources by a lead frame, tape bonding, or wire bonds. A package body made of a dielectric material is formed around the die and lead frame. One or more fins made of a thermally conductive material are independently attached the package by a thermally conductive bond to provide a direct thermally path between the package and the fins. If the non-functional side of the die is exposed external to the package, the fins may be attached to the die. If the die includes a metalized layer, the fins can be attached by soldering or brazing. In an alternative configuration, the fins can be molded onto the die.
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Fitch John S.
Hamburgen William R.
Compaq Computer Corporation
Oppenheimer Wolff & Donelly LLP
Thompson Gregory
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