Importance

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Abstract

A structure and a method provide an assembly for receiving an integrated circuit die. The assembly comprises a heat sink selectively coated with electrically insulative material. The heat sink is attached by one of various methods directly on to the integrated circuit die and a lead frame for external electrical connections. The heat sink is formed as a stepped structure to increase the path of moisture penetration so as to improve moisture resistance and reliability. In one embodiment of the present invention, the electrically insulative material comprises anodized aluminum, which is formed on the heat sink by a vapor deposition step, followed by a hard anodization step. Other electrical insulative material which can be thinly applied on the surface of the heat sink are non-conductive resins and polymers. The heat sink is formed out of copper or a copper alloy, selected for strength and electrical and thermal conductivities. The heat sink can be connected to a power or a ground terminal of the integrated circuit, which is bonded on the heat sink on an exposed (i.e. unaluminized) exposed area of the heat sink. The exposed area of the heat sink is formed either by a step which masked off the exposed area from the aluminum deposition step, or by a subtractive process, such as sand-blasting, to selectively removing the anodized aluminum. In one embodiment, the assembly is encapsulated in plastic with one side of the heat sink flush with one outer surface of the plastic encapsulation.

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First Claim