Abstract: A high performance plastic-encapsulated integrated circuit package is disclosed having both improved heat dissipation and low ground noise comprising one or more separate ground and/or power planes below the signal lines which includes an electrically conductive heat sink member on which an integrated circuit die is centrally and directly mounted for dissipating heat while providing electrical insulation therebetween and which may also may function as a ground or power plane, a peripheral printed circuit board having electrically conductive members formed on one or more surfaces thereof, one surface of which is also mounted to the heat sink and electrically separated therefrom and which surrounds the centrally mounted die on the heat sink, and a lead frame assembly bonded to an opposite surface of the printed circuit board.