Importance

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Abstract

A low-cost printed circuit board for a semiconductor package having the footprint of a ball grid array package has an integral heat sink, or 'slug,' for the mounting of one or more semiconductor chips, capable of efficiently conducting away at least five watts from the package in typical applications. It is made by forming an opening through a sheet, or substrate, of B-stage epoxy/fiberglass composite, or 'pre-preg,' then inserting a slug of a thermally conductive material having the same size and shape as the opening into the opening. The slug-containing composite is sandwiched between two thin layers of a conductive metal, preferably copper, and the resulting sandwich is simultaneously pressed and heated between the platen of a heated press. The heat and pressure forces the resin to the surface of the composite and into the space between the slug and the walls of the composite, where it solidifies, bonding the edges of the slug to the substrate within the opening and adhering the conductive layers to the upper and lower surfaces of the substrate. The resulting laminate can thereafter be processed as a convention printed circuit board to incorporate conventional circuit board features, e.g., circuit traces, wire bonding pads, solder ball mounting lands, and via holes.

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First Claim