Printed circuit board with integral heat sink for semiconductor package
First Claim
1. A method for fabricating a low-cost printed circuit board having an integral heat sink for use in a semiconductor package, comprising:
- selecting a sheet of composite material having a predetermined thickness and generally parallel top and bottom surfaces;
forming an opening through the sheet, the opening having a periphery and defining interior sidewalls on the sheet inside of the opening that are generally perpendicular to the top and bottom surfaces of the sheet;
forming a heat sink of a thermally conductive material, the heat sink having a thickness that is the about the same as the thickness of the dielectric sheet, generally parallel top and bottom surfaces, a periphery that is about the same size and shape as the periphery of the opening in the sheet, and exterior sidewalls that are generally perpendicular to the top and bottom surfaces of the heat sink;
inserting the heat sink in the opening in the dielectric sheet such that the respective top and bottom surfaces of the heat sink and the dielectric sheet are generally coplanar, with the respective exterior sidewalls of the heat sink and the interior sidewalls of the dielectric sheet in spaced opposition to each other; and
, adhering the opposing sidewalls of the heat sink and the dielectric sheet to each other such that the heat sink is retained within the opening in the dielectric sheet, with the respective top and bottom surfaces of the heat sink and the dielectric sheet generally coplanar with each other.
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Accused Products
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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Citations
20 Claims
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1. A method for fabricating a low-cost printed circuit board having an integral heat sink for use in a semiconductor package, comprising:
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selecting a sheet of composite material having a predetermined thickness and generally parallel top and bottom surfaces;
forming an opening through the sheet, the opening having a periphery and defining interior sidewalls on the sheet inside of the opening that are generally perpendicular to the top and bottom surfaces of the sheet;
forming a heat sink of a thermally conductive material, the heat sink having a thickness that is the about the same as the thickness of the dielectric sheet, generally parallel top and bottom surfaces, a periphery that is about the same size and shape as the periphery of the opening in the sheet, and exterior sidewalls that are generally perpendicular to the top and bottom surfaces of the heat sink;
inserting the heat sink in the opening in the dielectric sheet such that the respective top and bottom surfaces of the heat sink and the dielectric sheet are generally coplanar, with the respective exterior sidewalls of the heat sink and the interior sidewalls of the dielectric sheet in spaced opposition to each other; and
,adhering the opposing sidewalls of the heat sink and the dielectric sheet to each other such that the heat sink is retained within the opening in the dielectric sheet, with the respective top and bottom surfaces of the heat sink and the dielectric sheet generally coplanar with each other. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20)
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16. A method of making a low-cost printed circuit board having an integral heat sink for use in a semiconductor package, comprising:
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punching an opening of a given size and shape through a porous, insulative substrate impregnated with a stage B epoxy, the substrate having a predetermined thickness and opposite surfaces;
pressing a slug of a thermally conductive metal into the opening, the slug having about the same size and shape as the opening and about the same thickness as the substrate;
positioning the substrate between two sheets of an electrically conductive metal to form a sandwich; and
,applying heat and pressure to opposite faces of the sandwich to laminate the electrically conductive sheets to the respective opposite surfaces of the substrate and bond the slug in the opening.
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Specification