Importance

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Abstract

A low-cost EMI shield that fits around an integrated circuit package to absorb electromagnetic energy and dissipate it as heat. The shield is not ohmically conductive so it may contact electrically active conductors without affecting the operation of the circuit. EMI is prevented from being radiated by and around an integrated circuit package by a perimeter of material that is lossy to high-frequency electromagnetic currents. This perimeter is fitted around an integrated circuit package such that the gap between a heat sink or other top conductor and the printed circuit board is completely closed by the lossy material. This provides not only a line-of-sight obstruction to RF currents, but also provides a lossy return path to close the circuit loop for currents on the skin of the heat sink. Since the material is lossy, rather than purely conductive, it can be used with a less than perfect ground attachment. Grounding is accomplished by the placement of the lossy material adjacent to the printed circuit board, allowing capacitive coupling to close the loop. The position of the lossy material is secured by a friction fit, adhesive, or self-locking or retaining features built into the lossy material.

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First Claim