A heat sink assembly for removing heat from a plurality arrays of heat generating-components mounted on a printed circuit board includes a fist and a second heat sink, a plurality of fastening assemblies. Each of the first and second heat sinks comprises an elongated base and a plurality of fins mounted on the base. The base extends beyond the fins at two lateral sides of the fins to form a first shoulder and a second shoulder located above the first shoulder in a manner such that the second shoulder of the first heat sink is superposed on the first shoulder of the second heat sink. The fastener assembly extends through the superposed first and second shoulders of the first and second heat sinks to assemble the first and second heat sinks on the printed circuit board.