Abstract: There is disclosed a novel high heat flux liquid cooled semi-conductor heat sink of modular construction suitable for semi-conductor chips such as IC's, hybrids, lasers, and power semi-conductors, said modular heat sink containing inserts with chip substrates made of metals, such as tungsten or molybdenum, said substrate including at least one surface suitable for bonding one or more semi-conductor chips in intimate thermal relationship thereto, and including a heat exchange surface on the interior surface thereof, said module providing means for enclosing said heat exchange surface in a liquid tight manner and including means for providing a flow of coolant liquid to remove heat from said heat exchange surface by formation of nucleate vapor bubbles on said heat exchange surface, the improvement wherein said heat sink module comprises individual heat sink inserts upon which semi-conductor chips are intimately bonded, said heat sink element being provided with means to electrically isolate each heat sink eleme